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  • 1
    ISSN: 1572-8935
    Keywords: PEEK ; Composites ; DSC ; Crystallinity ; Melting
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Films of short carbon fiber reinforced poly(ether ether ketone) (PEEK) composite were formed by compression molding pellets for 10 min at 380 °C under air. A heating stage was used to prepare isothermally treated PEEK composites before DSC scan. The dependence of degree of crystallinity on the heating rate (10–80 °C/min) was investigated for specimens crystallized at different temperatures. The results indicated that 50 °C/min was an optimum heating rate to suppress the reorganization and to avoid the superheating of high crystallinity specimens with the sample weight of 10 mg. The upper peak temperature of double-melting peaks continued to increase with crystallization temperature. This peak temperature was related to the transition from regime II to III. The phenomenon of lower crystallinity and higher melting temperature supports the interpretation that the upper melting peak corresponded to crystals growing during the earlier stage of isothermal crystallization.
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  • 2
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    Journal of polymer research 7 (2000), S. 257-266 
    ISSN: 1572-8935
    Keywords: Poly(ether sulfone) ; Epoxy resin ; Physical aging ; DSC
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract The physical aging process of 4-4′-diaminodiphenylsulfone (DDS) cured diglycidyl ether bisphenol-A (DGEBA) blended with various molecular weights of poly(ether sulfone) (PES; Mn = 28,600, 10,600, and 6,137) was studied by DSC. For DGEBA/DDS system blended with a low MW PES-3 (Mn = 6,137), no phase separation of the polymer blend and only one enthalpic relaxation process due to physical aging was observed. Since the high MW PES-1 (Mn = 28,600) had a Tg close to that of fully cured DGEBA/DDS, the fully cured DGEBA/DDS/PES-1 blend had a broader glass transition than a neat DGEBA/DDS system. However, the DSC results showed two enthalpic relaxation processes due to the physical aging of PES-rich and cured epoxy-rich phases as the material was aged at 155 °C (30 °C below Tg). Since the Tgs of PES-1-rich and epoxy-rich phases overlapped with each other, the enthalpic relaxation processes corresponding to each phase coupled to each other in the earlier stage of physical aging. The medium MW PES-2 (Mn = 10,600) has a much lower Tg than that of fully cured DGEBA/DDS, two well separated Tgs were observed for the cured DGEBA/DDS/PES-2 blend, indicating the cured epoxy was immiscible with PES. Aging the polymer blend at 155 °C (24 °C below Tg1 of the PES-2-rich phase and 53 °C below Tg2 of the epoxy-rich phase) produced two well separated relaxation processes due to PES-2-rich and epoxy-rich phases. The experimental results suggested that aging the polymer blend at a suitable temperature would improve the phase separation between PES-1-rich and epoxy-rich phases.
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  • 3
    ISSN: 1572-8935
    Keywords: TDI-based polyurethane elastomers ; Tg ; Tglobal transition ; DSC ; TSC/RMA ; DMA
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Thermal transitions of TDI-based polyurethane elastomers with PTMO as the soft segment were characterized by the depolarization technique in TSC and by using with the thermal windowing technique on selected specimens in the RMA measurements. Results indicate that the broadened thermal transition in the glass transition region as observed in the DSC thermogram is related to the combined Tg transition and the Tglobal transition in the TSC spectrum. This Tglobal transition is associated with the macromolecular property as detected by tan δ in DMA measurement. The increase in the Tg with a high NCO content may be explained by the structural modification found on the urethanic chain with the additional linkage of the hard segment that affects the cooperative motion of the molecular chain. Data measured from DSC, TSC/RMA and DMA with simulated DEA and wide angle X-ray data are presented for the characterization of the polyurethanes. The RMA measurement leads to a compensation search on Tg transition and provides pertinent thermokinetic data that correlates the NCO content with changes in enthalpy and entropy on the relaxation behaviors in the Tg transition of polyurethane elastomers.
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  • 4
    ISSN: 1572-882X
    Keywords: cellulose alkyl esters ; poly(∈-caprolactone) ; blends ; miscibility ; DSC
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Cellulose alkyl esters, CELL- OCOCnH2n+1(n = 1 ∼ 6), were synthesized by a homogeneous reaction of cotton cellulose with different acyl chlorides in N,N-dimethylacetamide--lithium chloride solution. The miscibility of the esterified celluloses with poly(∈-caprolactone) (PCL) was investigated, mainly through thermal analysis by differential scanning calorimetry (DSC). A polymer pair, cellulose butyrate (CB)/PCL, showed the highest miscibility of all the binary blends examined here; this is usual when relatively high-substituted esters (DS ≥ 2.0) are used as the respective component. The butyl ester derivatives with DS ≤ 1.5 showed poor miscibility with PCL
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  • 5
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    European biophysics journal 24 (1996), S. 293-299 
    ISSN: 1432-1017
    Keywords: Phase transition ; NMR ; DSC ; X-ray diffraction ; Bonnet Transformation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Physics
    Notes: Abstract Ternary systems of palmitoyl-oleoyl-phosphatidylcholine (POPC) and the non-ionic surfactant C12EO2 (di-ethylene-oxide-mono-dodecyl-ether) in water have been studied with optical microscopy, NMR, DSC and X-rays from ambient temperatures to 45 °C. Below 29 °C the system is in the lamellar liquid crystalline state. Between 30 and 32 °C it transforms into a cubic Ia3d structure which converts into the cubic Pn3m phase at 39 °C. The transitions are fully reversible. An epitaxial relationship between all three phases was found, which is an elegant and convenient way to rearrange molecules from lamellar bilayers to a network of curved surfaces. The la3d (Q230) to Pn3m (Q224) transition occurs without measurable enthalpy change. This, together with the metric relation of 1.60 between the cubic lattice constants is strong evidence for a Bonnet transformation, where the structural changes occur without change in curvature. The potential significance of the cubic phases as intermediate structures for biological processes, e. g. transport across a bilayer or fusion of membranes, are discussed.
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  • 6
    ISSN: 1432-1017
    Keywords: Key words Phosphatidylcholine ; Phosphatidylglycerol ; DSC ; Phase diagrams ; Miscibility ; Nonideality parameter
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Physics
    Notes: Abstract The miscibility of phosphatidylcholine (PC) and phosphatidylglycerol (PG) with different chain lengths (n = 14, 16) was examined by differential scanning calorimetry (DSC) at pH 2 and pH 7. The determination of the coexistence curves of the phase diagrams was performed using a new procedure, namely the direct simulation of the heat capacity curves as described recently (Johann et al. 1996, Garidel et al. 1997). From the simulations of the heat capacity curves first estimates for the nonideality parameters for nonideal mixing as a function of composition were obtained and phase diagrams were constructed using temperatures for the onset and offset of melting which were corrected for the broadening effect caused by a decrease in cooperativity of the transition. In most cases, the composition dependence of the nonideality parameters indicated nonsymmetric mixing behavior. The phase diagrams were further refined by simulations of the coexisting curves using a four-parameter model to account for nonideal and nonsymmetric mixing in the gel as well as in the liquid-crystalline phase. The mixing behavior of the systems was analyzed as a function of pH and chain length difference to elucidate the effect of these two parameters on the shape of the phase diagrams. At pH 7 the phase boundaries are much closer together and a narrower coexistence range is obtained compared to the corresponding phase diagrams at pH 2. For DPPC/DMPG at pH 2, the shape of the phase diagram and the strongly positive nonideality parameter ρ 1 for the liquid-crystalline phase indicates an upper azeotropic point. This indicates an unusual behavior of the system, namely more pronounced clustering of like molecules in the liquid-crystalline phase compared to the gel phase.
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  • 7
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    Journal of thermal analysis and calorimetry 47 (1996), S. 35-49 
    ISSN: 1572-8943
    Keywords: bone cement ; DSC ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Bone cements are widely used for the fixation of metallic prostheses in orthopaedics and to form replacements for skull defects in neurosurgery. Acrylic bone cements are based on a mixture of methyl methacrylate (MMA) and a fine powder of polymethyl methacrylate (PMMA). The polymerization of the bone cement occurs in contact with the bone and the prosthesis which act as the boundaries of a bulk polymerization reactor. The kinetic behaviour of the bone cement plays a fundamental role for the final performance of the implant. In this paper, the isothermal and non-isothermal polymerization behaviour of a commercial bone cement is described. A simple phenomenological model, accounting for the autoacceleration ffect, for a diffusion controlled termination mechanism and for the reaction between inhibitor and initiator, is proposed. The reaction kinetics is analysed by DSC. DSC data are used for the determination of the rates of polymerization under isothermal and non-isothermal conditions. The experimental data are processed to calculate the parameters of the proposed phenomenological kinetic model. The analytical and numerical details related to the integration of the model are discussed.
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  • 8
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    Journal of thermal analysis and calorimetry 47 (1996), S. 181-194 
    ISSN: 1572-8943
    Keywords: DSC ; gelatinization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Data obtained by dynamic mechanical analysis and DSC analysis of durum wheat dough are presented and discussed. Doughs with water contents ranging from 45 to 55% (w/w) were subjected to sinusoidal shearing by means of a dynamic mechanical spectrometer (Rheometrics, RFS2) equipped with parallel plate geometry, 0.1 strain amplitude and 1 rad/min frequency. The tests were carried on in temperature sweep mode at a heating rate of 2°C min−1. Wheat samples with water contents in the range between 7.5 and 37.5% and doughs with 37.5% moisture content were mixed for different times and subjected to DSC analysis (Perkin-Elmer, DSC-7) at a heating rate of 20°C min−1. Dynamic mechanical analysis revealed that the relationship between the dynamic properties of the dough and the temperature was modified as the water content of the dough increased and was quite different from that for gluten. A similar response was observed in the course of temperature scans made by means of DSC. These experimental findings suggest that the water-starch interaction in the presence of a protein matrix is affected by the availability of water and that the protein system is a competitor with respect to starch.
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  • 9
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    Journal of thermal analysis and calorimetry 47 (1996), S. 543-557 
    ISSN: 1572-8943
    Keywords: compensation effect ; DSC ; kinetics ; TG
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Four computer programs as well as one demo-version for non-linear evaluation of kinetic data in thermal analysis and calorimetry, were presented. The multi-task program TA-kin meets all mathematical requirements for solving the numerical assignments. It is shown that the so-called compensation effect is due to the mathematical structure of the Arrhenius equation. Several applications of TA-kin to a lot of DSC- and TG-measurements and isoperibolic batch experiments as well as adiabatic semi batch experiments realized by precision calorimetry have been discussed.
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  • 10
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    Journal of thermal analysis and calorimetry 47 (1996), S. 685-695 
    ISSN: 1572-8943
    Keywords: DSC ; polymers ; resins ; TG
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The paper describes the co-curing studies of ethynyl and ethenyl end-capped imide resins. The effect of composition and chemical structure of ethenyl end-capped resins (nadicimides) on thermal behavior of ethynyl end-capped resins was evaluated using DSC and thermogravimetric analysis. An increase in char yield was observed on co-curing of few resin formulations. A mechanism has been proposed to account for this observation.
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  • 11
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    Journal of thermal analysis and calorimetry 47 (1996), S. 1213-1228 
    ISSN: 1572-8943
    Keywords: cassava starch ; DSC ; starch thermal properties
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Order-disorder transitions were investigated in native cassava starch at intermediate moisture contents (35 to 60% wt. water), using Differential Scanning Calorimetry (DSC) and dynamic Wide Angle X-ray Diffractometry (WAXS) with a synchrotron radiation source. The gelatinization of granules occurs as a cooperative process, due to constraints induced in crystallites by the amorphous areas. Variations of water content (water volume fraction from 0.28 to 0.86) and heating rate (0.2–10
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  • 12
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    Journal of thermal analysis and calorimetry 47 (1996), S. 1179-1200 
    ISSN: 1572-8943
    Keywords: DSC ; isothermal microcalorimetry ; retrogradation ; starch
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract In the present study, isothermal microcalorimetry was introduced as a tool to investigate properties of starch retrogradation during the first 24 h. The study was made on purified amylose and amylopectin from corn, as well as on native starches, such as wheat, potato, maize, waxy maize and amylomaize, differing in their amylose content. The results were obtained in the form ofP-t traces (thermal powervs. time), and integration of these traces gave a net exothermic enthalpy of reaction, caused by the crystallization of amylose and amylopectin. TheP-t traces reflected the quantities of amylose and amylopectin in the starch studied. Depending on the amylose content and the botanical source of the starch, the rate of crystallization of amylose was high and predominated over that of amylopectin during the first 5–10 h. The contribution from amylose crystallization to the measured exothermic enthalpy was very substantial during this period. After ∼10 h, amylose crystallized at a lower constant rate. During the first 24 h, amylopectin crystallized at a low steady rate. The exothermic enthalpies obtained by the isothermal microcalorimetric investigations during the first 24 h of retrogradation were generally low in relation to the endothermic melting enthalpies observed by differential scanning calorimetry (DSC) measurements after 24 h of storage. The discrepancies in enthalpy values between the two methods are discussed in relation to phase separation and the endothermic effects owing to the decrease in polymer-water interactions when polymer-rich regions in the starch gel separate. Besides the exothermic enthalpies obtained, theP-t traces also made it possible to study the initial gelation properties of amylose from different botanical sources. The present study further demonstrated that isothermal microcalorimetry can provide a possible way to investigate the antistaling effect of certain polar lipids, such as sodium dodecylsulphate (SDS) and 1-monolauroyl-rac-glycerol (GML), when added to starches of different botanical origin. The net exothermic heat of reaction for starch retrogradation during the first 24 h was decreased when GML or SDS was added to the starch gels. The recordedP-t traces also showed how the effect of the added lipid influenced different periods during the first 24 h of starch retrogradation, and that the effect depended mainly on the amylose content, the botanical source of the starch, and the type of lipid used. When GML or SDS was added to waxy maize, the isothermal microcalorimetric studies clearly indicated some interaction between amylopectin and the polar lipids. These results concerning the action of anti-staling agents are further discussed in relation to the helical inclusion complexes formed between amylose-polar lipid and amylopectin-polar lipid.
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  • 13
    ISSN: 1572-8943
    Keywords: cooling/heating rate ; DSC ; fragility parameter ; glass transition temperature ; sorbitol-fructose
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The glass transition temperatures of sorbitol and fructose were characterized by four points determined on DSC heating thermograms (onset, mid-point, peak and end-point), plus the limit fictive temperature. The variations of these temperature values, observed as functions of cooling and heating rates, were used to determine the fragility parameter, as defined by Angell [1] to characterize the temperature dependence of the dynamic behavior of glass-forming liquids in the temperature range above the glass transition. The apparent activation energy values, determined for the different temperatures studied, were similar for fructose and sorbitol. These values were compared to data obtained from other techniques, such as mechanical spectroscopy. The variations of the apparent activation values, observed in experiments involving cooling and heating at the same rate, slow cooling followed by rate-heating, or rate-cooling followed by fast heating, were explained by aging effects occurring during the heating step.
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  • 14
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    Journal of thermal analysis and calorimetry 47 (1996), S. 1545-1565 
    ISSN: 1572-8943
    Keywords: cocoa butter ; fat crystallization ; DSC ; fat polymorphism ; fat structure ; fats ; lard ; milk fat ; triacylglycerols ; X-ray diffraction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The thermal behavior of three ural fats (displaying very different composition), cocoa butter (CB)2, lard, and a stearin obtained from anhydrous milk-fat (AMF) fractionation, were studied by both DSC and X-ray diffraction as a function of temperature (XRDT). To perform temperature explorations between −30
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  • 15
    ISSN: 1572-8943
    Keywords: DSC ; polyethylenes ; X-ray
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract In thermal analysis polyethylenes can be characterized by their melting temperature. With the polyethylene mixtures studied, we obtained the best results during solidification. Crystallization temperature decreased in the order: high density PE, low density PE linear, radical low density PE. Calorimetric measurement of crystallization enthalpies allowed the determination of the composition of each of the polyethylenes, in regenerated and recycled mixtures in relation with the frame of the plastic waste valorisation process. The rate of crystallization obtained from X-ray diffraction spectra of these polymers is function of their volumic mass. A good agreement has been observed between these two techniques.
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  • 16
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    Journal of thermal analysis and calorimetry 46 (1996), S. 5-14 
    ISSN: 1572-8943
    Keywords: cadmium phenoxyacetate ; complexes ; DSC ; mercury(II) phenoxyacetate ; TG
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Solid cadmium and mercury(II) phenoxyacetates were prepared and investigated by DSC and TG techniques. The cadmium salt decomposed in two steps with the loss of 1.5 water molecules at first and the successive formation of CdCO3 as final product. Δdeh H * associated with the loss of one water molecule was compared with the corresponding values obtained for other phenoxyacetates previously studied and the obtained results were discussed. Anhydrous mercury(II) phenoxyacetate gave, on heating, HgCO3 which successively decomposed with the formation of gaseous products and a little amount of solid residue.
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  • 17
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    Journal of thermal analysis and calorimetry 46 (1996), S. 177-186 
    ISSN: 1572-8943
    Keywords: activation energy ; chalcogenide glass ; DSC
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Results of differential scanning calorimetry (DSC) at different heating rates on Se2Ge0.2Sb0.8 chalcogenide glass are reported and discussed. As the heating rate (α) changed, also the glass transition temperature (T g) and onset temperature of crystallization (T c) changed. As the value of the transition activation energyE t changed, the crystallization fraction (χ), heat flow (Δq and the crystallization peak temperature (T p) also changed. The value of the effective activation energy of crystallizationE c was calculated by means of six different methods. The Se2Ge0.2Sb0.8 chalcogenide glass has two crystallization mechanisms, a one-dimensional and an other surface crystallization growth. The average value ofE t for Se2Ge0.2Sb0.8 is equal to 194.95±3.9 kJ·mol−1 and the average value ofE c is equal to 164±3.3 kJ·mol−1.
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  • 18
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    Journal of thermal analysis and calorimetry 46 (1996), S. 237-243 
    ISSN: 1572-8943
    Keywords: DSC ; DTG ; polyacetylene films ; TMA
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Polyacetylene films irradiated byγ-rays up to 100 MRad were studied by means of TMA, DTG and DSC methods. It is shown that as the irradiation dose increases the concentration of topological branching knots into the polymer chains and theT g values decrease, the total mass loss and the enthalpy of the thermal isomerization reaction also decrease.
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  • 19
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    Journal of thermal analysis and calorimetry 49 (1997), S. 79-85 
    ISSN: 1572-8943
    Keywords: cross-linking degree ; DSC ; enthalpy relaxation ; epoxy resins ; physical aging ; reactive diluent
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Structural relaxation in different epoxy-anhydride and epoxy-diamine resins has been investigated by differential scanning calorimetry using annealing and cooling rate experiments. The annealing experiments lead to the determination of enthalpy loss,δH, at an equivalent annealing temperatureT a=T g-20, and for periods of annealing time, ta, between 1 h and 4 months. The variation ofδH with logta, defines a relaxation rate per decade,rrpd, which is very sensitive to changes of the epoxy network. The cooling rate experiments allow the determination of the apparent activation energy,δh *. The effect of the degree of crosslinking, the addition of a reactive diluent, which acts as flexibilizer, and the length of cross-link onrrpd and δh* was studied.
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  • 20
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    Journal of thermal analysis and calorimetry 49 (1997), S. 149-154 
    ISSN: 1572-8943
    Keywords: DSC ; heterogeneity in polymer network ; poly(methacrylic acid)-net-poly(oxytetramethylene) ; thermogravimetry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract TG and DSC were carried out on PMAA-net-POTM in order to elucidate the relation between the heterogeneity and the thermal changes; moreover, TG and DSC were carried out on PPOTMDM and PMAA to compare the results. The onset temperature in the last stage in the TG curve of PMAA-net-POTM increases as the concentrations of DMF and POTMDM in the polymerization decrease. This is explained in terms of plasticizers effects. A single peak due to fusion of POTM chains appears in the DSC curves of most copolymers. However, it is not seen in the DSC curves of copolymers with high heterogeneity. This is explained in terms of the freezing of POTM chains by frozen heterogeneous moieties.
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  • 21
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    Journal of thermal analysis and calorimetry 49 (1997), S. 177-182 
    ISSN: 1572-8943
    Keywords: bismaleimide resin ; CTBN ; curing behaviour ; DSC ; TG
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Bismaleimide resin (Compimide 353) was modified with the liquid elastomer carboxyl-terminated acrylonitrile butadiene (CTBN). The prereaction synthesis and curing of the CTBN-bismaleimide resin is discussed. The structure of the modified resin was identified by IR and NMR spectroscopy. The basic curing mechanism is also discussed. DSC and TG were used to study the curing behaviour and kinetic parameters, viz. the order of reaction, energy of activation and preexponential factor. Adhesive properties such as lap shear strength and peel strength at room temperature and elevated temperature were evaluated and are discussed.
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  • 22
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    Journal of thermal analysis and calorimetry 46 (1996), S. 619-626 
    ISSN: 1572-8943
    Keywords: crystallization ; DSC ; filled polypropylene ; nucleation ; structural modification
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The influence of high concentration of BaSO4 as nucleating agent on crystallization of fiber-forming polypropylene was studied by DSC. The work presents experimental and calculated values of melting and crystallization enthalpies of filled polypropylene and the influence on the formation of interface interactions between filler and polymers. These results show minimal interactions of components (BaSO4 and polypropylene) under experimental conditions.
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  • 23
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    Journal of thermal analysis and calorimetry 46 (1996), S. 643-679 
    ISSN: 1572-8943
    Keywords: DDTA ; DSC ; macromolecules
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract This review traces the development of thermal analysis over the last 40 years as it was experienced and contributed to by the author. The article touches upon the beginning of calorimetry and thermal analysis of polymers, the development of differential scanning calorimetry (DSC), single run DSC and other special instrumentations, up to the recent addition of modulation to calorimetry. Many new words and phrases have been introduced to the field by the author and his students, leaving a trail of the varied interests one can have over 40 years. It began with “cold crystallization” and most recently the term “oriented, intermediate phase” was coined, creating in-between: “extended chain crystals,” the “irreversible thermodynamics of melting of polymer crystals,” “dynamic differential thermal analysis” (DDTA), “the rule of constant increase ofC p per mobile bead within a molecule at the glass transition temperature,” “superheating of polymer crystals,” “melting kinetics,” “crystallization during polymerization,” the “chain-folding principle, “molecular nucleation,” “rigid amorphous phase,” a “system of classifying molecules,” “macroconformations,” “amorphous defects,” “rules for the entropy of fusion based on molecular shape and flexibility,” “single-molecule single-crystals,” “a system of classifying phases and mesophases,” and “condis phase.”
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  • 24
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    Journal of thermal analysis and calorimetry 46 (1996), S. 795-808 
    ISSN: 1572-8943
    Keywords: DSC ; kinetics ; liquid crystalline polymer ; optical transmittance ; polycarbosilane ; side-chain mesogen ; transition parameters
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract This paper is concerned with an analysis of the thermodynamics and kinetics of mesophase formation by cooling from the isotropic state of side-chain liquid crystalline polycarbosilanes containing spacers in the range from 3 to 11 CH2-groups. The polymers are characterized by their thermotropic behaviour as far as temperature, enthalpy and entropy of the transitions are concerned. The kinetics was followed by optical and calorimetric methods. Longer spacer length leads to more perfect ordering in the mesophase, higher isotropization temperatures, and lower glass transition temperatures. The Avrami and Ozawa formalism to describe the transition kinetics to the mesophase from the isotropic state cannot be interpreted as the nucleation and growth mechanism known from crystallization.
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  • 25
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    Journal of thermal analysis and calorimetry 49 (1997), S. 343-349 
    ISSN: 1572-8943
    Keywords: double melting peak ; DSC ; fiber ; polyethylene
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The multiple melting peaks observed on differential scanning calorimetry (DSC) of ultrahigh molar-mass polyethylene fibers (UHMMPE) are analyzed as a function of sample mass. Using modern DSC capable of recognizing single fibers of microgram size, it is shown that the multiple peaks are in part or completely due to sample packing. Loosely packed fibers fill the entire volume of the pan with rather large thermal resistance to heat flow. On melting, the fibers contract and flow to collect ultimately at the bottom of the pan. This process seems to be able to cause an artifact of multistage melting dependent on the properties of the fibers. A method is proposed to greatly reduce, or even eliminate, errors of this type. The crucial elements of the analysis of melting behavior and melting temperature are decreasing the sample size and packing the individual fibers in a proper geometry, or to introduce inert media to enhance heat transport.
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    Journal of thermal analysis and calorimetry 49 (1997), S. 399-405 
    ISSN: 1572-8943
    Keywords: DSC ; polyimide fiber ; TMA ; TG
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    Topics: Chemistry and Pharmacology
    Notes: Abstract A commercially available polyimide fiber was investigated as a possible precursor for the formation of carbon fibers. The thermal response of the fiber was thoroughly investigated using DSC, TMA and TG. These responses were dependent on the atmosphere and tension during scanning. The fiber was stabilized at high temperatures both in inert and oxidative environments and the effect of these stabilization treatments on the structure and properties of the fiber was carefully followed. During heating, the fiber showed shrinkage tendency at small tensions, but at higher tensions the fibers could be stretched. Among the two environments investigated, air was more effective than nitrogen in getting a more stable fiber.
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    Journal of thermal analysis and calorimetry 49 (1997), S. 407-415 
    ISSN: 1572-8943
    Keywords: compatibility ; covulcanization ; derivative heat flow (δW/δT) ; DSC ; microheterogeneous
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    Topics: Chemistry and Pharmacology
    Notes: Abstract Derivative heat flow curves give much more information about the phase heterogeneity of binary blends composed of NR, SBR and BR elastomers thanT g. In blend compositions, the areas under the derivative heat flow curves appear to be an additive function of the concentration of elastomers in the case of incompatible blends (NR/BR, NR/SBR). They are less than additive for either a partially compatible blend (uncured SBR/BR) or a compatible blend (covulcanized SBR/BR). In the case of 60/40 SBR/BR blends, a DSC (T 0.5) reveals a singleT g, in conformity with the earlier investigators, whereas the derivative heat flow curve shows two peaks (T p) indicating incomplete homogenization of the phases. This is a new observation not mentioned in the published literature. Thus, derivative heat flow traces are likely to provide a unique tool to determine compatibility of elastomers. The study also reveals the importance of sample contact with the DSC pan in quantitative determinations.
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    Journal of thermal analysis and calorimetry 49 (1997), S. 449-454 
    ISSN: 1572-8943
    Keywords: DSC ; network ; polyethylene ; turbidimetry
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    Topics: Chemistry and Pharmacology
    Notes: Abstract Semicrystalline polymers are made of a crystalline phase and of an amorphous phase. Recently, NMR, Raman and FTIR experiments have identified a third phase comprised of defects such as tie-molecules, in the organization of chains. Our investigation of physical gels has led us to believe that by following the heat flow in a very slow temperature ramp (0.05 K min−1), phasechanges, unnoticed in the usual fast ramp, could be detected. These are associated to a physical network strained in the temperature ramp. In order to obtain more information on the network phase, the polymer has been crosslinked The characteristics obtained by slow calorimetry and turbidimetry of the original and modified materials are compared.
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    Journal of thermal analysis and calorimetry 49 (1997), S. 483-490 
    ISSN: 1572-8943
    Keywords: carboxyterminated polybutadiene ; DSC ; DMA ; SEM ; toughened epoxy
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    Topics: Chemistry and Pharmacology
    Notes: Abstract A new type of toughened epoxy polymer based on epoxy cresol novolac resin (ECN) and carboxy terminated polybutadiene (CTPB) liquid functional rubber has been studied. ECN has been synthesized in the laboratory and CTPB used was also of indigenised origin. Rubber modified epoxies were characterized with the help of differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA) and scanning electron microscopy (SEM) techniques.
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    Journal of thermal analysis and calorimetry 49 (1997), S. 477-481 
    ISSN: 1572-8943
    Keywords: DSC ; EVA blends ; phenolic resin ; TG-DTG
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    Topics: Chemistry and Pharmacology
    Notes: Abstract The properties of polymeric blends originate from the synergistic association of their components. In this investigation, phenolic resins obtained by the reaction of cashew-nut shell liquid (CNSL) and aldehyde are used in several applications. Mixtures of CNSL with industrial reject ethylene-co-vinyl acetate (EVA reject) were prepared with an EVA reject content up to 70%. The thermal compatibility and stability were evaluated by means of thermogravimetry (TG), derivative thermogravimetry (DTG) and differential scanning calorimetry (DSC). For blends containing a high percentage of EVA reject, the TG curves clearly show two decomposition stages, one at 350
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    Journal of thermal analysis and calorimetry 49 (1997), S. 513-520 
    ISSN: 1572-8943
    Keywords: DSC ; glass transition ; heat capacity ; melting transition ; nanophases ; polymers
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    Topics: Chemistry and Pharmacology
    Notes: Abstract Polymer molecules have contour lengths which may exceed the dimension of microphases. Especially in semicrystalline samples a single molecule may traverse several phase areas, giving rise to structures in the nanometer region. While microphases have properties that are dominated by surface effects, nanometer-size domains are dominated by interaction between opposing surfaces. Calorimetry can identify such size effects by shifts in the phase-transition temperatures and shapes, as well as changes in heat capacity. Specially restrictive phase structures exist in drawn fibers and in mesophase structures of polymers with alternating rigid and flexible segments. On several samples shifts in glass and melting temperatures will be documented. The proof of rigid amorphous sections at crystal interfaces will be given by comparison with structure analyses by X-ray diffraction and detection of motion by solid state NMR. Finally, it will be pointed out that nanophases need special attention if they are to be studied by thermal analysis since traditional ‘phase’ properties may not exist.
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  • 32
    ISSN: 1572-8943
    Keywords: dielectric spectroscopy (DETA) ; DSC ; dynamic mechanical (DMA) spectroscopy ; glass transition ; PET ; polymers ; relaxation ; rigid amorphous ; temperature modulated DSC
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    Topics: Chemistry and Pharmacology
    Notes: Abstract The relaxation strength at the glass transition for semi-crystalline polymers observed by different experimental methods shows significant deviations from a simple two-phase model. Introduction of a rigid amorphous fraction, which is non-crystalline but does not participate in the glass transition, allows a description of the relaxation behavior of such systems. The question arises when does this amorphous material vitrify. Our measurements on PET identify no separate glass transition and no devitrification over a broad temperature range. Measurements on a low molecular weight compound which partly crystallizes supports the idea that vitrification of the rigid amorphous material occurs during formation of crystallites. The reason for vitrification is the immobilization of co-operative motions due to the fixation of parts of the molecules in the crystallites. Local movements (Β-relaxation) are only slightly influenced by the crystallites and occur in the whole non-crystalline fraction.
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    Journal of thermal analysis and calorimetry 49 (1997), S. 745-753 
    ISSN: 1572-8943
    Keywords: DSC ; kerogen ; oxidation ; pyrolysis ; type determination
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    Topics: Chemistry and Pharmacology
    Notes: Abstract The rate of pyrolysis and oxidation of 8 different samples of oil shale kerogen concentrate (KC) were investigated using DSC analysis. Recently performed thermogravimetric studies (TG and DTG) with the same samples of KC indicated that the activation energy of the pyrolysis of specific KCs increases with increasing paraffinic structure in the KC. An opposite effect, i.e. a decrease of the activation energy with an increase of paraffinic structure was determined in the case of KC oxidation. In this study, using the standard ASTM E-698 method based on the determined temperature at which the maximum heat effect could be observed (exo in the case of oxidation and endo in the case of pyrolysis), an activation energy for the pyrolysis, as well as for the oxidation process was determined and also successfully correlated with the content of paraffinic structure of KC. Thus, the higher content of paraffinic structure in KCs indicates that higher values of the activation energy could be determined either in the case of pyrolysis or oxidation followed by DSC analysis.
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    Journal of thermal analysis and calorimetry 49 (1997), S. 795-799 
    ISSN: 1572-8943
    Keywords: butter ; butter oil ; DSC ; recombined butter
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    Topics: Chemistry and Pharmacology
    Notes: Abstract DSC can be used to quickly determine if a product labeled as butter is actually a recombined butter made without milk. Recombined butter is manufactured from anhydrous milk fat, skim milk powder, water, salt, and lecithin. Melting profiles of tempered samples of natural butter and recombined butter were alike, but DSC curves from 5 to 25°C of untempered refrigerated samples revealed that the enthalpy of the melting transition around 17–20°C was much higher for natural butter than for recombined butter. The procedure for differentiating the two products can be completed in less than 20 min.
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    Journal of thermal analysis and calorimetry 49 (1997), S. 809-816 
    ISSN: 1572-8943
    Keywords: dehydration ; drying method ; DSC ; lactitol ; lactitol monohydrate ; TG ; X-ray powder diffraction
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    Topics: Chemistry and Pharmacology
    Notes: Abstract The purpose of this study is to find out the effect of the crystal water content on the crystal structure of lactitol monohydrate. Crystal water was removed by drying over silicagel at 40°C and by using phosphorus pentoxide as drying agent at 20°C. The amouts of water removals were identified by thermogravimetry, the melting points and the heat of fusions were calculated from the results of differential scanning calorimetry measurements and the structure of samples were identified by X-ray powder diffraction method. Over 23 w/w% of total water content could removed by gently drying until significant structural changes could be detected. The melting point of anhydrous lactitol obtained by drying lactitol monohydrate was 120°C and the melting enthalpy was 102 J g−1 when measured with heating rate 10°C min−1 by DSC.
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    Journal of thermal analysis and calorimetry 49 (1997), S. 831-837 
    ISSN: 1572-8943
    Keywords: DSC ; enzymatic hydrolysis ; functional properties ; hemisphaericin ; mexicain
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    Topics: Chemistry and Pharmacology
    Notes: Abstract DSC was used to study the extent of denaturation of hemisphaericin and mexicain hydrolysates from corn gluten, soybean and sunflower meals. It was observed that the defatted meals studied exhibited only one broad peak transition. The data obtained demonstrated that the partial protein denaturation found with hemisphaericin or mexicain is correlated to modifications of functional properties. The two enzymes display different modes of action, according to the protein source.
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    Journal of thermal analysis and calorimetry 49 (1997), S. 913-927 
    ISSN: 1572-8943
    Keywords: anesthetic drugs ; bupivacaine hydrochloride ; dibucaine hydrochloride ; DSC ; polymorphism ; prilocaine hydrochloride ; procaine hydrochloride ; solvent mediated transitions ; temperature resolved X-ray diffraction ; tetracaine base ; tetracaine hydrochloride ; thermodynamic relationships
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    Topics: Chemistry and Pharmacology
    Notes: Abstract The local anesthetic drug tetracaine hydrochloride is described in the Europ. Pharmacopea with a melting point of 148°C or with a range of 134 to 147°C due to the melting points of two other forms. The polymorphic behaviour of tetracaine hydrochloride has been studied by using thermal treatments, storage at 92% r.h., crystallizations and equilibrations with saturated solutions. Samples were characterized by X-ray diffraction, IR, thermal analysis and elemental analysis. Since some findings were difficult to interpret, temperature resolved X-ray diffraction was used additionally for the understanding of the thermal behaviour of tetracaine hydrochloride. In this study the polymorphic behaviour of some other local anesthetic drugs is compared. Ten different forms of tetracaine hydrochloride: six anhydrous crystalline forms, an amorphous form, a hemihydrate, a monohydrate and a tetrahydrate were identified. The relationships between all forms are given. The heating curve of the commercial form 1 is very dependent on the heating rate. This anhydrous form 1 is the thermodynamic stable modification at ambient temperature. The form 2 is reversibly enantiotrope to form 1. The four other modifications called 3, 4, 5 and 6 are monotropes of form 1. Only forms 1 and 5 are stable at ambient temperature. Form 1 is hygroscopic only at high humidity level of 92% r.h., form 5 is hygroscopic at 61% r.h. Both transform into the monohy-drate. No polymorphic forms of tetracaine base, dibucaine hydrochloride, procaine hydrochloride or prilocaine hydrochloride were found. The commercial form of bupivacaine hydrochloride is a monohydrate. Thermal treatment at 200°C gives one anhydrous form. As demonstrated by temperature resolved X-ray diffraction two other forms are detected by heating and cooling processes between 100 and 170°C. Equilibrations and crystallization experiments show that solvates are easily obtained in different solvents. Temperature resolved X-ray diffraction is a very efficient tool as a support to DSC for the identification of the transition processes and interpretation of thermal events and thermodynamic relationships. Equilibration experiments are very adequate to find out the thermodynamically stable form at ambient temperature (solvent mediated transitions).
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    Journal of thermal analysis and calorimetry 49 (1997), S. 961-970 
    ISSN: 1572-8943
    Keywords: distribution constant ; DSC ; powder compact ; Rosin-Rammler particle size distribution ; thermal resistance
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    Topics: Chemistry and Pharmacology
    Notes: Abstract How a DSC result is influenced by the particle size distribution of a powder sample is shown, and a simple and optimal method to be included in a routine DSC analysis (e.g., purity determination) to improve the reliability of the analysis is proposed. In case ofα-Al2O3 powder, most reliable heat capacity data can be obtained by preparing a powder with a self-similar particle size distribution with a distribution constant of 0.7, and by compressing it under a pressure of 1.5 MPa for a duration of 5 min or longer.
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    Journal of thermal analysis and calorimetry 49 (1997), S. 999-1005 
    ISSN: 1572-8943
    Keywords: DSC ; finite element method ; temperature gradients ; polymer
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    Topics: Chemistry and Pharmacology
    Notes: Abstract Differential Scanning Calorimetry is frequently used for measurements of thermal properties on all kinds of substances. The temperature lag in the samples depend on the thermal properties and the thermal contact between sample and sample holder. In the paper, we discuss the temperature distribution in samples of comparatively low thermal conductivity, such as polymers. The purpose of this study is to pinpoint the substantial temperature differences that may occur in such bad conducting samples under different conditions. The calculations of the temperature gradients have been carried out by using a finite element software package.
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    Journal of thermal analysis and calorimetry 49 (1997), S. 991-998 
    ISSN: 1572-8943
    Keywords: cryo-microscopy ; crystallization ; DSC ; ICE ; microscopy
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    Topics: Chemistry and Pharmacology
    Notes: Abstract A simultaneous differential scanning calorimeter (DSC)-optical video microscope instrument has been developed. The instrument development included slight modifications to the sample head of a Perkin-Elmer DSC-7, along with the use of a CCD camera and magnifying lenses. The instrument permitted simultaneous following of optical and thermal events during isothermal and non-isothermal DSC experiments. The DSC curves were almost identical to those given by a standard DSC-7. The operational temperature range of the instrument is between −160 to 600°C. The capabilities of the DSC-video microscope are illustrated by examples of ice crystallization data in aqueous solutions of glycerol and dimethyl sulphoxide.
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    Journal of thermal analysis and calorimetry 47 (1996), S. 1201-1212 
    ISSN: 1572-8943
    Keywords: aging ; amylopectin ; DSC ; gels ; glass transition ; recrystallization ; retrogradation ; rice starch ; sugars
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    Topics: Chemistry and Pharmacology
    Notes: Abstract Thermal characterization of gelatinized binary rice starch-water and ternary starch-sugar-water gels before and after aging was carried out using differential scanning calorimetry. The glass transition temperature of the maximally freeze-concentrated solution (T′g) in both fresh and aged gels was observed to decrease progressively with increasing sugar concentration. Aging of the gels generally shiftedT′g to higher temperatures, but had little or no effect on the ice melting peak temperature (T m). The presence of various sugars could either accelerate or retard starch (amylopectin) recrystallization, depending on the type and concentration of sugar, as well as on starch/water ratio. A hypothesis based on the dual antiplasticizing-plasticizing effects of sugars was postulated to explain the observed effects. Of the sugars studied, xylose and fructose appeared to display exceptional retardative and accelerative effects, respectively, on retrogradation.
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    Keywords: DSC ; gelatinisation ; potato starch
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    Topics: Chemistry and Pharmacology
    Notes: Abstract Gelatinisation temperatures as a function of moisture content were determined for potato starch. The native starch was then hydrothermally treated at a temperature 3% (Kelvin degrees) below the gelatinisation peak temperature and at moisture levels varying from 20 to 67% (by weight). Gelatinisation temperatures, temperature ranges and enthalpy values were affected for all treated samples. However, two sample populations could be distinguished: those samples treated under ‘limited’ moisture conditions and other samples treated in the presence of ‘extragranular’ moisture. A two-step hydrothermal treatment further increased the gelatinisation temperature, but the effect of the second step was small in comparison to that of the first.
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    Journal of thermal analysis and calorimetry 47 (1996), S. 1299-1314 
    ISSN: 1572-8943
    Keywords: baked goods ; cookies ; crackers ; DSC ; pretzels ; starch
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    Topics: Chemistry and Pharmacology
    Notes: Abstract We describe an application of DSC as an analytical ‘fingerprinting’ method that has been used to characterize the thermal properties of wheat starch in low-moisture, wheat-flour-based baked products, including cookies, crackers, and pretzels. This use of DSC has enabled us to relate starch thermal properties, on the one hand, to starch structure, and on the other hand, to starch functionality, in terms of baking performance and finished-product quality.
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    Journal of thermal analysis and calorimetry 47 (1996), S. 1339-1360 
    ISSN: 1572-8943
    Keywords: bread crumb ; bread dough ; DSC ; hydrocolloid ; mechanical properties ; pentosans ; protein
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    Topics: Chemistry and Pharmacology
    Notes: Abstract The effects of hydrocolloids (guar and locust bean gums), soluble pentosans, and whey proteins on staling of bread crumb were investigated by means of DSC, rheometry, and image analyis. One current hypothesis, that these ingredients would behave as “water binders” and, at least the former two, as anti-staling agents, was indeed confirmed, although this action might be indirect. All the samples considered showed an exothermic DSC peak preceding the endotherm of the amylopectin fusion. According to a previous work, this signal was attributed to a water-dependent cross-linking process that would involve next-neighbouring polymer chains. To check the effect produced by molecular modifications that were expected to increase the water uptake of these ingredients, doughs containing added succinylated pentosans and whey proteins, and a polycarboxylate polymer, PEMULEN TR-1, were examined. These modifications enhanced starch retrogradation and yielded a firmer crumb. It was tentatively concluded that some direct interaction between these modified molecules and the crumb polymers might have taken place. In line with the food polymer science approach, the use of Time-Temperature-Transformation (TTT) diagrams is also discussed.
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    Journal of thermal analysis and calorimetry 47 (1996), S. 1513-1525 
    ISSN: 1572-8943
    Keywords: Β-lactoglobulin ; DSC ; protein modification ; thermal properties
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    Topics: Chemistry and Pharmacology
    Notes: Abstract The thermal properties of Β-lactoglobulin (Β-LG) were studied by differential scanning calorimetry (DSC) under different medium conditions.pH, neutral salts, protein perturbants, and polyols all affected the DSC characteristics of Β-LG. Acylation with fatty acids also changed the thermal properties, particularly peak width at half-height. The results suggest that the structural stability of Β-LG is controlled by non-covalent forces, particularly electrostatic and hydrophobic interactions. Disulfide bonds did not contribute to the thermal response of Β-LG. Fatty N-acyl-amino acids caused marked increases in thermal stability and decreases in denaturation enthalpy, and additional peaks were observed in the presence of some palmitoyl derivatives.
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    Journal of thermal analysis and calorimetry 48 (1997), S. 19-38 
    ISSN: 1572-8943
    Keywords: chalcedony ; crystalline disorder ; DSC ; DTA ; high-low quartz inversion ; silcretes
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    Topics: Chemistry and Pharmacology
    Notes: Abstract The paper reviews studies on possible applications of the high-low quartz inversion in petrology. Since the first suggestions of Fenner and Tuttle, nearly fifty papers have dealt with the subject, including ten by the present authors. The detailed discussion of the preparative and instrumental factors which may influence the quartz inversion behaviour reveals that the DTA (DSC) runs have to be made under highly standardized conditions to permit measurement of the ‘material inherent factors’ (mainly crystal physical factors) which cause variations in shape and temperatures. The most striking variations in shape and temperatures of the inversion effect (e.g. including temperatures more than 70°C lower than the ‘textbook value’ of 573°C for the quartz inversion) are observed for microcrystalline quartz crystals. The literature and the authors' own investigation demonstrate that the most interesting field of application of the method is that of authigenic quartz formation in sediments and soils. The characterization of metamorphic quartz is more complicated. Four fields of study are chosen to demonstrate the possible application of the quartz inversion characterization for petrogenetic interpretations: (1) the differentiation between authigenic and inherited quartz crystals in sediments, (2) the characterization of the contact-metamorphic aureoles around granites, (3) special regional-metamorphic terrains and (4) (from a few so far unpublished studies) the differentiation between sedimentary and soil silcretes.
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    Journal of thermal analysis and calorimetry 48 (1997), S. 259-266 
    ISSN: 1572-8943
    Keywords: DSC ; freezable water ; muscle water
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    Topics: Chemistry and Pharmacology
    Notes: Abstract The freezable water contents of samples obtained from previously chilled semimembranous muscle of middle-aged beef carcasses after a 24 h cooling period a room at in 5±1
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    Journal of thermal analysis and calorimetry 48 (1997), S. 473-483 
    ISSN: 1572-8943
    Keywords: dosage form ; drug products ; DSC ; identification ; quantitation ; TG
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Thermal analysis techniques, DSC and TG can advantageously be used in quality control of drug products. The methods are commonly used in preformulation for the study of polymorphism and for the study of the interactions drug substance-excipients, since these physical interactions can be the basis of the dosage form performance. For routine control of the drug products, DSC and TG methods which are quick, which require only few mg of the samples and which are automated, are very attractive for routine analysis of drug products. A single scan can give several qualitative and quantitative informations. DSC offer analytical possibilities only if the drug substance and the excipients do not have physical interactions or limited interactions (e.g. eutectic behaviour). About twenty marketed products have been analyzed by DSC and TG. In most of them identification of drug substance is easy. Several excipients could be identified in a tablet. Quantitations are demonstrated for some drug substances and excipients. DSC purity calculations have been applied to acetyl salicylic acid, paracetamol, cimetidine, pindolol, ibuprofen.
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    Journal of thermal analysis and calorimetry 48 (1997), S. 437-445 
    ISSN: 1572-8943
    Keywords: cardiac glycoside binding ; DSC ; membrane protein ; membrane receptor binding ; Na+ ; K+-ATPase ; thermal unfolding ; titration calorimetry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract DSC studies are carried out to characterize Na+,K+-ATPase isolated from pig kidney in its natural membrane environment as well as in its purified state upon detergent treatment. The transition temperatures of the investigated thermal protein unfolding process, observed between 43 and 64.5° C, depend on the local membrane environment as well as onpH. In addition, the transition temperature is significantly increased upon binding of different cations and ligands which are known to interact with the enzyme. Evidence for a lipid phase transition around 23 °C in the original biological membrane is reported. The application of a calorimeter equipped with removable cells appears to be more suitable for the investigation of this type of membrane sample than an instrument with fixed capillary cells. Filling the sample capillary cell with an usual syringe, consisting of a long and thin needle, can influence the experimental results. Na+, K+ -ATPase acts as the receptor for cardiac glycoside binding. The thermodynamic parameters of this binding process are determined by titration calorimetry. The binding of ouabain, as a typical example, is unusually slow and is enthalpy driven. The enthalpy change upon binding enthalpy is −75 kJ mol−1 at 25 °C. The surprisingly low stoichiometric coefficient, resulting from an evaluation based on a simple one step binding model, is interpreted in terms of a dimeric receptor unit.
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    Journal of thermal analysis and calorimetry 48 (1997), S. 647-656 
    ISSN: 1572-8943
    Keywords: aluminate sodalite ceramics ; ceramics ; dielectric properties ; DSC ; ferroelectric transitions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Aluminate sodalite ceramics, (Sr8Al12O24)(CrO4)2) — SACR, have been prepared from solution spray-dried precursors. The spray drying of a mixed aqueous nitrate solution gave an anhydrous powder which was thermally decomposed in air at 1350 °C to give a crystalline SACR powder with a median volume diameter of 4–6 μm. The SACR powder was dry pressed and sintered to 〉90% density. The yellow SACR powder showed two phase transitions between 10 and 45 °C with a 25 ° intermediate phase region indicative of a low defect concentration in the crystalline structure. A colour change observed in the sintered ceramic (changing to a mixed green/yellow) and a narrowing of the phase transition region (15–40 °C) are discussed. Dielectric measurements were consistent with the presence of two extrinsic ferroelectric transitions at 17 and 35 °C.
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    Journal of thermal analysis and calorimetry 48 (1997), S. 691-696 
    ISSN: 1572-8943
    Keywords: conglomerate ; DSC ; melting phase diagram ; recemic compound
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The phenomena of conglomerate formation-racemic compound formation were investigated in a series of five (N-alkyl)-2′,6′-pipecoloxylidides. The optically active enantiomers were prepared by optical resolution of the racemates using 2R,3R-tartaric acid and 0,0′-dibenzoyl-2R,3R-tartaric acid as resolving agent. By DSC measurement of the racemates and the enantiomer the binary phase diagrams were determined. Among the four racemic molecular compounds the N-methyl derivative is the more stable. By increasing the length of the alkyl chain the stability of the racemic compound decreased, and in case of the longest -butyl-chain conglomerate formation was observed.
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    Journal of thermal analysis and calorimetry 48 (1997), S. 727-734 
    ISSN: 1572-8943
    Keywords: DSC ; monosulfide solid solution ; system Fe-Ni-S
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    Topics: Chemistry and Pharmacology
    Notes: Abstract The decay of a monosulphide solid solution (mss) with the composition (Fe1−1Nix)0.96S was investigated by means of differential scanning calorimetry in the temperature range, from 20 to 305
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    Journal of thermal analysis and calorimetry 49 (1997), S. 1305-1314 
    ISSN: 1572-8943
    Keywords: DSC ; electrolytic capacitors ; etched Al foils ; thermal resistance ; transient state
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    Topics: Chemistry and Pharmacology
    Notes: Abstract A DSC method for evaluating the surface area of etched Al foils for use in high performance electrolytic capacitors is presented. A linear relationship between the etching degree (effective surface area) and the thermal resistance of the sample is obtained by means of DSC, based on the transient phenomenon. This method using the transient state in DSC measurement is not only novel, but also rapid and simple in evaluating the surface area of an etched aluminum foil. The method is effective even when the Al foil has a naturally oxidized surface.
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  • 54
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    Journal of thermal analysis and calorimetry 49 (1997), S. 1357-1364 
    ISSN: 1572-8943
    Keywords: chemisorption ; desorption ; DSC ; dynamic FT-IR silver powder ; XPS
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The mechanism of adsorption and desorption of ethyl cellulose (EC) on and from silver powder was studied. After analysis with DSC, XPS and dynamic FT-IR, which could be heated by a program-controlled heater, applied to observe the states of pure EC and of EC adsorbed on silver powder, and also the thermal decomposition of EC from silver powder, the chemisorption bonding bridge between the oxygen atoms of EC and the silver atoms investigated. The differences in thermal decomposition between pure EC and EC adsorbed in silver powder were also studied. It was concluded that the chemisorption bonding between the oxygen atoms of EC and the silver atoms mainly involved the lone-pair electrons of the oxygen atoms on the EC chain and the outer empty 5 sp3 hybrid orbital of the silver. Because of the formation of this bridge, the bonds between neighboring carbon and oxygen atoms are weakened. As a result of this effect, the C-O bonds in the EC chain are broken more easily than the C-H bonds, which leads to the observation of -C-H- fragments in the upper space when EC adsorbed on silver is heated. When the same experiments were carried out on pure EC, almost all kinds of broken fragments of the EC molecule, including -C-H-, -C=O- and -C-O- appeared simultaneously.
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  • 55
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    Journal of thermal analysis and calorimetry 49 (1997), S. 1467-1475 
    ISSN: 1572-8943
    Keywords: CRTA ; DSC ; kinetics ; synthetic brochantite ; TG-DTA ; thermal decomposition
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    Topics: Chemistry and Pharmacology
    Notes: Abstract The reaction pathway of the thermal decomposition of synthetic brochantite, Cu4(OH)6SO4, to copper(II) oxide was investigated through the detailed kinetic characterization of the thermal dehydration and desulferation processes. The dehydration process was characterized by dividing into two overlapped kinetic processes with a possible formation of an intermediate compound, Cu4O(OH)4SO4. The dehydrated sample, Cu4O3SO4, was found first to be amorphous by means of XRD, followed by the crystallization to a mixture of CuO and CuO-CuSO4 at around 776 K. The specific surface area and the crystallization behaviour of the amorphous dehydrated compound depend largely on the dehydration conditions. The thermal desulferation process is influenced by the gross diffusion of the gaseous product SO3, which is governed by the advancement of the overall reaction interface from the top surface of the sample particle assemblage to the bottom.
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  • 56
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    Journal of thermal analysis and calorimetry 50 (1997), S. 365-373 
    ISSN: 1572-8943
    Keywords: DSC ; heat capacity ; indium ; linearity ; modulated DSC
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Experiments using a commercial modulated DSC (MDSC) for the measurement of specific heat capacity of a sample have been carried out. It is found that because the amplitude of heat flow of MDSC is a complicated non-linear function of various experimental conditions such as the modulation frequency and the heat capacities of a sample and pan, the methodology of heat capacity determination using an MDSC in a single run has not been justified. The experimental results, on the other hand, agree with the theoretical equation of one of the authors. It is therefore concluded that the capabilities of MDSC should be further examined.
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  • 57
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    Journal of thermal analysis and calorimetry 50 (1997), S. 625-632 
    ISSN: 1572-8943
    Keywords: DSC ; NMR ; 8-quinolinol compounds ; TG-DTG ; stability ; thermal decomposition
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    Topics: Chemistry and Pharmacology
    Notes: Abstract Solid M-Ox compounds, whereM represents Mg(II), Zn(II), Pb(II) and NbO(III), and Ox is 8-quinolinol, have been prepared. Thermogravimetry, derivative thermogravimetry (TG, DTG), differential scanning calorimetry (DSC), nuclear magnetic resonance (NMR) and infrared absorption spectra (IR) have been used to characterize and to study the thermal stability and thermal decomposition of these compounds.
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  • 58
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    Journal of thermal analysis and calorimetry 52 (1998), S. 765-772 
    ISSN: 1572-8943
    Keywords: DSC ; isoconversional method ; polyethylene glycol ; T-CR-T diagrams
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    Topics: Chemistry and Pharmacology
    Notes: Abstract The analysis of DSC experimental data from solidification is improved, thanks to a modified isoconversional method. The validity of the proposed method is tested for a polyethylene glycol with a mean molecular weight of 6000. The temperature-cooling rate-transformation diagrams reveal good agreement between the experimental and calculated data.
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  • 59
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    Journal of thermal analysis and calorimetry 53 (1998), S. 35-47 
    ISSN: 1572-8943
    Keywords: DSC ; isothermal crystallization ; thermotropic polyester
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    Topics: Chemistry and Pharmacology
    Notes: Abstract Differential scanning calorimetry was used to study the isothermal kinetics of three-dimensional ordering formation from the mesophase of the thermotropic polyester poly(ethylethylene-4,4-diphenoxyterephthalate). An Avrami exponent of 4 was found and the measured rates of transformation were related with the efficiency of packing. A nucleation and growth process was assumed in the determination of the temperature coefficient, and the interfacial free energies are discussed in terms of the chain flexibility.
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  • 60
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    Journal of thermal analysis and calorimetry 53 (1998), S. 71-85 
    ISSN: 1572-8943
    Keywords: DSC ; enantiomer ; IR ; powder X-ray diffractometry ; racemate ; TG ; thermomicroscopy
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    Topics: Chemistry and Pharmacology
    Notes: Abstract The physicochemical characterization of the solid-state enantiomers and racemate of efaroxan hydrochloride (C13H17N2O+Cl-, M=252.5 g mol-1) was performed by thermoanalytical methods (differential scanning calorimetry, thermogravimetry and thermomicroscopy) and spectral methods (infrared spectrometry and X-ray diffractometry). The efaroxan enantiomers and racemate were shown to be unstable near the melting point. At the beginning of the decomposition, a loss of hydrogen chloride was observed. However when sealed pans were used, the compounds decomposed at higher temperature, allowing a precise evaluation of the melting enthalpies by means of differential scanning calorimetry. The nature of the racemate and its thermal stability were assessed by evaluating its free formation enthalpy. An enantiotropic solid-solid transformation (II→I) was noted for the racemate; the reverse process (I→II) follows zero-order kinetics.
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  • 61
    ISSN: 1572-8943
    Keywords: copper(II)-oxime complexes ; DSC ; kinetic parameters
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    Topics: Chemistry and Pharmacology
    Notes: Abstract Several new complexes of the types [Cu(DioxH)2] and [CuX2·DioxH2] (DioxH2: aliphatic or alicyclic α-dioxime) were obtained and characterized by means of near and far Fourier transformation IR spectroscopy. The thermal decompositions of seven complexes of these types were studied by using DSC measurement data. For several decomposition stages, apparent kinetic parameters were derived by means of the nomogram method.
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  • 62
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    Journal of thermal analysis and calorimetry 54 (1998), S. 467-476 
    ISSN: 1572-8943
    Keywords: DSC ; TMDSC ; thermal conductivity ; thermal diffusivity
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    Topics: Chemistry and Pharmacology
    Notes: Abstract One of the benefits of temperature-modulated DSC (TMDSC) is its ability to measure thermal conductivity and thermal diffusivity without DSC cell modifications or additional accessories. Thermal conductivity of solid materials from 0.1 to about 1 W m-1 K-1 measured. Applications of this approach have been discussed in the literature but no description is yet available concerning the derivation of the working equations. This presentation provides a detailed derivation of the working equations used to obtain thermal conductivity and thermal diffusivity from TMDSC data.
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  • 63
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    Journal of thermal analysis and calorimetry 54 (1998), S. 721-729 
    ISSN: 1572-8943
    Keywords: branching ; chain extension ; cross-linking ; diepoxides or bis-epoxides ; DSC ; PET ; poly(ethylene terephthalate)
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    Topics: Chemistry and Pharmacology
    Notes: Abstract A series of chain-extended PET samples were obtained by the use of different amounts of a diepoxide as chain extender, which was prepared for this purpose. These samples exhibited different intrinsic viscosities and degrees of branching or cross-linking. The effects of this differentiation on the thermal properties were studied by differential scanning calorimetry. The thermal parameters studied were the glass transition temperature (Tg), the cold-crystallization temperature (Tcc), the melting temperature (Tm), the enthalpy (ΔHm) and the degree of crystallinity. The data revealed that, the higher the quantity of chain extender or the chain extension time, the higher Tgand Tcc, but the lower Tmand ΔHm, i.e. the more amorphous the chain-extended samples, as also shown by density measurements.
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    Journal of thermal analysis and calorimetry 55 (1999), S. 9-19 
    ISSN: 1572-8943
    Keywords: ARC ; DSC ; HFC ; kinetics
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    Topics: Chemistry and Pharmacology
    Notes: Abstract Isopropylnitrate (IPN) is described as a detonable material used in propellants and explosives. While there is considerable information available on its sensitivity and compatibility with other materials, very little is known about its thermochemical properties. This paper will describe the results obtained from some DSC, heat flux calorimetry (HFC) and accelerating rate calorimetry (ARC) measurements. The ASTM DSC method using a hermetic aluminum pan having a lid with a laser-produced pin hole was used to determine the vapour pressure of IPN1. Results calculated from an Antoine equation are in substantial agreement with those determined from DSC measurements. From the latter measurements, the enthalpy of vaporization was determined to be 35.32±0.62 kJ mol−1. Attempts to determine vapour pressures above about 0.8 MPa resulted in significant decomposition of IPNg. The enthalpy change for decomposition in sealed glass systems was found to be -3.43±0.09 kJ g−1 and -3.85±0.03 kJ g−1, respectively from DSC and HFC measurements on IPN1 samples loaded in air. Slightly larger exotherms were observed for the HFC results in air than those in inert gas, suggesting some oxidation occurs. In contrast, no significant difference in the observed onset temperature of about 150°C was observed for both the HFC and ARC results. From DSC measurements, an Arrhenius activation energy for decomposition of 126±4 kJ mol−1 was found. These measurements were also conducted in sealed glass systems and decomposition appeared to proceed primarily from the liquid phase.
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    Journal of thermal analysis and calorimetry 55 (1999), S. 67-76 
    ISSN: 1572-8943
    Keywords: activation energy ; DSC ; ethylene-vinyl acetate copolymer ; TG ; TG/IR ; thermal degradation
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    Topics: Chemistry and Pharmacology
    Notes: Abstract When ethylene-vinyl acetate copolymer, EVA, is heated, a two-stage thermal degradation occurs following its melting. The vinyl acetate content of the copolymer was determined to be 43.8% by using TA 2950 and TA 2050 thermogravimetric instruments. TG/FTIR was used to detect the evolved gas. Acetic acid and trans-1-R-4-R'-cyclohexane were the main products evolved from EVA in the first and second stage, respectively. The apparent activation energies were determined for both stages by differential methods.
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  • 66
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    Journal of thermal analysis and calorimetry 55 (1999), S. 57-65 
    ISSN: 1572-8943
    Keywords: artificial ageing ; DSC ; dynamic crystallization ; isoconversional method
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    Topics: Chemistry and Pharmacology
    Notes: Abstract A crystallization kinetics analysis of several polypropylene-polyethylene (PP-PE), PP-rich copolymers was made by means of differential scanning calorimetry. The crystallization was studied via calorimetric measurements at different cooling rates. Several additives were added to the base material. Some test samples were subjected to artificial ageing processes. A modified isoconversional method was used to describe the crystallization process under non-isothermal conditions. The value of the Avrami parameter was determined for primary and secondary crystallization.
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  • 67
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    Keywords: dioximine complexes of Co ; DSC ; kinetic compensation effect ; kinetic parameters of thermal decomposition
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    Topics: Chemistry and Pharmacology
    Notes: Abstract 14 mixed Co(III) dioximine chelates of the types [Co(Diox·H)2(amine)2]X (X = Br, I, NO3, ClO4) and H[Co(Diox·H)2(N3)2], respectively (Diox·H2-1,2-cyclohexane dione dioxime (nyoxime), 1,2-cycloheptane dione dioxime (heptoxime) 1,2-cyclooctane dione dioxime (octoxime) were obtained and their thermal decompositions were studied in an argon atmosphere. After the dehydration of the crystallohydrates, both types of complexes exhibit 3 decomposition stages. For the [Co(Diox·H)2(amine)2]X type complexes (X = Br, I) the first endothermal stage is the substitution of an amine molecule for the external sphere anion and this process is followed by two exothermal decomposition stages. With H[Co(Diox·H)2(N3)2] type complexes the first and third processes are relatively slow, but the second process is very fast, corresponding to a vertical portion of the TG curves. From the TG curves kinetic parameters were derived for 11 processes and the validity of a non-linear compensation law was observed.
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    Journal of thermal analysis and calorimetry 56 (1999), S. 51-57 
    ISSN: 1572-8943
    Keywords: DSC ; enthalpies ; NaAlF4 ; Na5Al3F14
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    Topics: Chemistry and Pharmacology
    Notes: Abstract Beside the two well-known minerals cryolite, Na3AlF6, and chiolite, Na5Al3F14, the binary system NaF-AlF3 also contains a third compound, NaAlF4, sodium tetrafluoroaluminate. Solid NaAlF4 has been prepared from its vapour under controlled conditions. The stability of NaAlF4 has been investigated by differential scanning calorimetry. It is shown that the disproportionation of the compound: 5NaAlF4(s)=Na5Al3F14(s)+2AlF3(s) takes place at considerable rate between 700 and 900 K. The enthalpy of this reaction is calculated and found to be -66.9 kJ. Enthalpies of the two solid state transitions α-Na3AlF6 → β-Na3AlF6 and α-AlF3 → β-AlF3 have also been measured and new values are reported. The enthalpy of formation of chiolite, Na5Al3F14, at 900 K has been recalculated from enthalpy increment data obtained by drop calorimetry. A value of ΔH900 o = -7513.6±12.0 kJ mol-1 has been obtained. This value is in disagreement with the recommended value given in JANAF Thermochemical Tables given at 900 K ΔHf o = -7559.2 kJ mol-1.
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    Journal of thermal analysis and calorimetry 56 (1999), S. 925-929 
    ISSN: 1572-8943
    Keywords: DSC ; equilibrium ; Fe-Ni distribution ; monosulfide solid solution ; pentlandite
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    Topics: Chemistry and Pharmacology
    Notes: Abstract Two mixtures of pentlandite and the monosulfide solid solution (mss) have been synthesized. The bulk compositions of the samples are Fe6Ni3S8 and Fe3Ni6S8. Differential scanning calorimetry detected exothermic process in the samples under heating. The process takes place in temperature range between phase transition in the mss (near 400 K) and 690 K and is governed by diffusion. X-ray powder diffraction has showed that equilibrium Fe-Ni distribution between pentlandite and the mss is achieved after short-time heating up to 670 K.
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  • 70
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    Keywords: cure kinetics ; DSC ; epoxy resin ; SAN ; thermoplastic blends
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    Topics: Chemistry and Pharmacology
    Notes: Abstract Cure kinetics using a differential scanning calorimetry (DSC) technique were analyzed for a thermoplastic modified tetraglycidyl-4,4′-diaminodiphenylmethane (TGDDM) epoxy resin cured with diaminodiphenylsulphone (DDS), an aromatic diamine. The neat resin and its blends with the poly(styrene-co-acrylonitrile) (SAN) of various compositions were studied by applying a phenomenological model proposed by Kamal. Kinetic parameters were determined by fitting experimental data. This model gives a good description of cure kinetics up to the onset of vitrification. Diffusion control was incorporated to describe the cure in the latter stages of cure. The results showed that the addition of SAN did not alter the nature of the reaction, but the reaction rates and final conversions decreased when SAN contents increase, due to reduction of mobility of the reacting species.
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    Journal of thermal analysis and calorimetry 56 (1999), S. 1285-1304 
    ISSN: 1572-8943
    Keywords: amorphous state ; combined techniques ; drug design ; drug product development ; drug substance ; drug technology ; DSC ; excipients ; failure investigations ; hydrates ; MDSC ; microcalorimetry ; pharmaceuticals ; polymorphism ; polymers ; preformulation ; process optimization ; purity ; quality control ; solvates ; stability ; sub-ambient DSC ; TG ; temperature resolved X-ray diffraction ; water interactions ; thermal microscopy ; water sorption-desorption
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Modern thermal analysis, microcalorimetry and new emerging combined techniques which deliver calorimetric, microscopic and spectroscopic data offer a powerful analytical battery for the study of pharmaceuticals. These techniques are very useful in all steps of development of new drug products as well as methods for quality control in production. The characterization of raw materials enables to understand the relationships between polymorphs, solvates and hydrates and to choose the proper development of new drug products with very small amount of material in a very short time. Information on stability, purity is valuable for new entities as well as for marketed drug substances from different suppliers. Excipients which vary from single organic or inorganic entity to complexes matrixes or polymers need to be characterized and properly controlled. The thermodynamic phase-diagrams are the basis of the studies of drug-excipients interactions. They are very useful for the development of new delivery systems. A great number of new formulations need proper knowledge of the behaviour of the glass transition temperature of the components. Semi-liquid systems, interactions in aqueous media are also successfully studied by these techniques.
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    Journal of thermal analysis and calorimetry 57 (1999), S. 61-73 
    ISSN: 1572-8943
    Keywords: amorphous ; combined techniques for polymorphism ; DSC ; MKS 492 ; polymorphism ; purine ; quantitative determination ofamorphous and polymorphs ; solvent mediated transitions ; temperature resolved X-ray diffraction ; TG ; thermodynamic relation between polymorphs ; xanthine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The polymorphic behaviour of the purine derivative MKS 492 was studied with investigations of suspensions of selected samples in different solvents and of samples obtained by crystallizations. The samples were analyzed by DSC, TG and X-ray diffraction. Six different crystalline modifications called A, B, B’, C, D and E and an amorphous form were identified. Four pure crystalline modifications, A, B, C and D have been manufactured and characterized by DSC, X-ray, IR, solubilities, densities, hygroscopicity and dissolution measurements. The four forms A, C, D and E are monotrop to the form B. The form B is enantiotrop to the form B’, which revealed the highest melting point of all known polymorphs. This form B’ is only stable at high temperature. Temperature resolved X-ray diffraction was very helpful for proper interpretation of the thermal events. The melting peaks of the forms A and C and the endothermic peak corresponding to the enantiotropic transition B into B’ occur in a narrow range of temperature. The form B which is the most stable one at room temperature has been chosen for further development. Quantitative methods to determine the content of the forms A, C and D in samples of form B or to determine the content of form A, B and D in form C have been developed by using X-ray diffraction. Limits of detection are 1 or 2%. For the quantitative determination of the amorphous fraction, X-ray diffraction and microcalorimetry are compared. For high amounts of the amorphous fraction, the X-ray diffraction method is preferred because it is faster. Microcalorimetry is very attractive for levels below 10% amorphous content. The lowest limit of detection is obtained by microcalorimetry, about 1%.
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  • 73
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    Keywords: crystal modifications ; DSC ; Gibbs free energy function ; molecular modelling ; solution calorimetry
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    Topics: Chemistry and Pharmacology
    Notes: Abstract The thermodynamic energy relationship between two crystal modifications of cimetidine was investigated and compared with differences in their processing properties with respect to transformation from one modification to the other. The crystal energies of the two modifications A and D were found to be almost identical and therefore the polymorphs are regarded as virtually isoenergetic crystals. This statement is based on DSC measurements of the melting points and of the enthalpies of fusion for the two crystal forms, which enable the calculation of the Gibbs free energy functions. Furthermore, the statement is supported by measurements of the enthalpies of solution in two different solvents. Both DSC and solution experiments reveal a slightly higher stability of the D modification with respect to the A form. In addition, tribomechanical treatment also indicates modification D to be the more stable one, as well as the higher density of the D form. No transformation during DSC at low heating rate was found which could be used in a stability consideration. As the explicit crystal structures of the two modifications are resolved, it was possible to calculate crystal energies theoretically as well. The theoretical results showed a remarkable difference in the crystal energies at zero degree Kelvin. Furthermore, they were just contradicting experimental findings by stating A being more stable than D. Possible reasons for this discrepancy and the feasibility of today's calculation methods with respect to prediction of stability properties are discussed.
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    Journal of thermal analysis and calorimetry 57 (1999), S. 631-642 
    ISSN: 1572-8943
    Keywords: DSC ; fluorocarbon chain ; polymerizability ; polymorphic behaviors ; X-ray diffraction
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    Topics: Chemistry and Pharmacology
    Notes: Abstract The molecular aggregation of acrylic and methacrylic acid esters containing long-fluorocarbon chains: 2-(perfluoroalkyl)ethyl acrylate (FFnEA) and 2-(perfluoroalkyl)ethyl methacrylate (FFnEMA) (F(CF2)nCH2CH2OCOC(X)=CH2, where X=H, CH3 and n=6, 8, 10) was investigated by differential scanning calorimetry (DSC) and temperature controlled X-ray powder diffraction measurement. These compounds exhibited some characteristic polymorphic behaviors depending on the length of fluorocarbon chain and the α-position methyl group. The solid-state polymerization by γ-ray irradiation was studied for these compounds in the various crystal forms. In the solid-state polymerization, highest polymerizability was observed in the crystal form that exists in the highest temperature region for each compound.
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    Journal of thermal analysis and calorimetry 58 (1999), S. 29-38 
    ISSN: 1572-8943
    Keywords: benzoicacid ; controlled release ; DSC ; ethyl cellulose ; FTIR
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The physical state of benzoic acid (BA) and its interaction with ethyl cellulose (EC) were examined in ethyl cellulose—benzoic acid matrices by Differential Scanning Calorimetry (DSC). The glass transition temperature (Tg) of EC of various matrices having BA in solid solution form (upto 27.7%) was reduced. The BA in matrices containing more than 38.9% drug exhibited distinct melting endotherms due to crystalline form. The peak temperatures of these endotherms were lowered and they broadened as the concentration was lowered. The solubility of BA increased at its melting point as compared to ambient temperature. The melting enthalpy of BA, when plotted as a function of its concentration yielded a straight line with intercept of 330 mg g−1 of matrix. This is the solubility of BA in EC at its melting temperature. Fourier Transform Infra Red Spectroscopy (FTIR) investigations confirmed that hydrogen bonding occurred between EC and BA through hydroxyl groups.
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    Journal of thermal analysis and calorimetry 58 (1999), S. 363-368 
    ISSN: 1572-8943
    Keywords: DSC ; lipid ; phase behaviour ; synchrotron radiation ; X-ray diffraction
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    Topics: Chemistry and Pharmacology
    Notes: Abstract The phase behaviour and phase stability of lipids are of importance in an understanding of the biological functions of cell membranes. Among a variety of physical techniques employed to study the phase behaviour and structural properties of polar lipids, differential scanning calorimetry and X-ray diffraction have proved to be successful and are the most frequently used methods. Applications involving a combination of the two techniques, particularly when synchrotron radiation is used as the light source of X-ray diffraction, are reviewed in this article.
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    Journal of thermal analysis and calorimetry 58 (1999), S. 653-662 
    ISSN: 1572-8943
    Keywords: dehydration ; DSC ; TG ; water ; zeolites
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A procedure for measurement of the heat of zeolite dehydration by scanning heating has been designed. Simultaneous data on heat flow (DSC) and mass loss (TG) are required for evaluation. The heating rate depends on the experimental conditions (point-spread function, sample mass, crucible design, and calorimetric reproducibility). Dehydration measurements have three advantages as compared with the sorption procedure: i) one can investigate samples with irreversible dehydration; ii) no approximation model is needed for calculation of the partial molar heat of dehydration; and iii) the procedure is not labor-consuming. The procedure was tested on the natural zeolites heulandite, chabazite and mordenite. The results are close to those measured by the sorption procedure. The partial molar heat of dehydration was found to depend on the water content. It increases from 50 to 87 J mol−1 K−1 for heulandite, from 53 to 81 J mol−1 K−1 for chabazite, and from 51 to 71 J mol−1 K−1 for mordenite. The approximation of the heat of sorption by linear regression was found to be wrong. Detection of a ‘phase transitioN’ after this approximation has no meaning.
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    Journal of thermal analysis and calorimetry 58 (1999), S. 725-739 
    ISSN: 1572-8943
    Keywords: DDC ; DSC ; DTA ; transformation-governed TA
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    Topics: Chemistry and Pharmacology
    Notes: Abstract The described instrumental method makes it possible that the quasi-static heating technique, well applicable to thermogravimetric measurements, (see Part I of this paper) can be used in the case of DTA and DSC examinations, too. Based on the new type of curves the characteristic transformation temperatures, the whole course of the transformation in dependence of sample temperature, the extent of the enthalpy change caused by the transformation or by its partial processes can accurately be determined. The essentially greater accuracy of the measurements — in comparison to the conventional ones — is due to the quasi-static heating technique which ensures that the transformations should take place under quasi-equilibrium conditions.
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    Journal of thermal analysis and calorimetry 59 (2000), S. 83-92 
    ISSN: 1572-8943
    Keywords: cationic and photoinitiated polymerization ; DSC ; interfacial mixing ; interpenetrating polymer network (IPN) ; glass transition temperature ; NMR ; quantitative thermal analysis of phases ; reactive epoxy and acrylate systems ; Tg broadening
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract In this study NMR and DSC are used to probe the structure, thermal characteristics and morphology of a network formed from a diepoxide/acrylate system. Separate chemistries are employed to polymerize the diepoxide and acrylate components. The cationic polymerization of the diepoxide exhibits excellent selectivity in producing a crosslinked polyether network without affecting the acrylate monomer. Subsequent photoinitiated free-radical polymerization of the acrylate produces a phase separated, semi-interpenetrating polymer network (SIPN).
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  • 80
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    Journal of thermal analysis and calorimetry 59 (2000), S. 93-100 
    ISSN: 1572-8943
    Keywords: catalyst ; cure kinetics ; DSC ; HTPB ; kinetic compensation effect ; urethane
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The kinetics of theurethane-forming cure reaction of hydroxyl terminated polybutadiene (HTPB) with isophorone diisocyanate (IPDI) in presence of ferric tris (acetyl acetonate) (FeAA) catalyst was investigated using differential scanning calorimetry (DSC). The Arrhenius activation parameters, viz., activation energy E and pre-exponential factor A were evaluated using the non-isothermal integral Coats-Redfern equation. The cure reaction was catalysed by ferric acetyl acetonate (FeAA), as revealed from the decrease in reaction temperatures and the increase in rate constants; however, the computed activation energy did not show any correlation to the catalyst concentration. The values of E and A for the uncatalysed reaction at different heating rates showed interdependence through kinetic compensation (KC) effect. Using KC correction, E values were normalised for the value of A for the uncatalysed reaction under identical conditions. The normalised E values decreased exponentially with increase in concentration of FeAA, showing high propensity of the HTPB-IPDI system for catalysis.
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  • 81
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    Journal of thermal analysis and calorimetry 59 (2000), S. 157-168 
    ISSN: 1572-8943
    Keywords: cellulose acetate ; DSC ; glass transition ; melting ; polycaprolactone
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Cellulose acetate-based polycaprolactones (CAPCL's) were synthesized by the polymerization of ε-caprolactone which was initiated by non-substituted OH group in cellulose acetate. The CL/OH (mol mol−1) ratios of the CAPCL's were changed from 2 to 20. Thermal and viscoelastic properties of the CAPCL sheets were studied by differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA). Glass transition, cold crystallization and melting were determined by DSC. Dynamic modules (E'), dynamic loss modules (E'') and tanδ were measured in a temperature range from −150 to 50°C by DMA. Apparent activation energy of a dispersion was calculated from the frequency dependency of E'' peak temperature. It was found that the main chain motion of both CA and PCL is observed in a CL/OH ratio from 0 to 10 mol mol−1. However, when CL/OH ratio exceeds 10 mol mol−1, the crystalline region which is rearranged by the PCL chain association is observed and only the main chain motion of PCL can be detected.
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  • 82
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    Journal of thermal analysis and calorimetry 59 (2000), S. 245-255 
    ISSN: 1572-8943
    Keywords: DSC ; metallocene ; polyethylenes ; SAXS ; synchrotron radiation ; thermal fractionation ; WAXD ; Ziegler-Natta
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract In this study, the stepwise isothermal crystallization or thermal fractionation of Ziegler—Natta and metallocene based polyethylenes (ZN-PE and m-PE) with two kinds of branch lengths (ethyl and hexyl) and branch compositions were studied using simultaneous synchrotron small-angle X-ray scattering (SAXS)/wide-angle X-ray diffraction (WAXD) and differential scanning calorimetry (DSC). The crystal long period and the invariant were determined by SAXS, and the variations of crystal unit cell parameters and the degree of crystallinity were determined by WAXD. The arithmetic mean length (Ln), the weightedmean length (Lw) and the broadness index (Lw/Ln) of the studied polyethylenes were previously determined by DSC. Results from these studies were interpreted using the model of branch exclusion, which affects the ability of the chain-reentry into the crystal phase. Multiple SAXS peaks and step-change in crystallinity change (WAXD) were seen during heating, which corresponded well with the crystal thickness distribution induced by stepwise crystallization. The effects of the heterogeneity of the 1-olefin branch length and the distribution on the crystal long period and the invariant as well as the degree of crystallinity were discussed.
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  • 83
    ISSN: 1572-8943
    Keywords: annealing ; DSC ; self-nucleation ; SSA ; thermal fractionation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A new technique to thermally fractionate polymers using DSC has been recently developed in our laboratory. The applications of the novel successive self-nucleation and annealing (SSA) technique to characterize polyolefins with very dissimilar molecular structures are presented as well as the optimum conditions to thermally fractionate any suitable polymer sample with SSA. For ethylene/α-olefin copolymers, the SSA technique can give information on the distribution of short chain branching and lamellar thickness. In the case of functionalized polyolefins, detailed examinations of SSA results can help to establish possible insertion sites of grafted molecules. The application of the technique to characterize crosslinked polyethylene and crystallizable blocks within ABC triblock copolymers is also presented.
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  • 84
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    Journal of thermal analysis and calorimetry 59 (2000), S. 497-508 
    ISSN: 1572-8943
    Keywords: Avrami equation ; crystallization ; dibenzylidene sorbitol ; DSC ; isothermal kinetics ; nucleating agents ; nucleation ; pine crystal ; polypropylene
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The effects of nucleating agents such as dibenzylidene sorbitol (DBS) (a derivative of sorbitol), pine crystal 1500, sodium and potassium benzoates in commercial grade isotactic polypropylene iPP are studied using differential scanning calorimetry (DSC). Isothermal crystallization kinetics of polypropylene to the alpha phase have been analyzed using Avrami's model. Results indicate that dibenzylidene sorbitol and pine crystal are very effective in increasing the crystallization temperature of the polymer and number of nuclei formed during crystallization.
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  • 85
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    Journal of thermal analysis and calorimetry 59 (2000), S. 559-570 
    ISSN: 1572-8943
    Keywords: adhesive ; composition analysis ; curing kinetics ; DMA ; DSC ; TGA ; thermal cure ; thermoplastic/thermoset blend
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract DSC, TGA and DMA thermal analysis techniques are used to characterize a complex adhesive blend. The chemical and thermomechanical property development shown to follow a two-stage process. Beneficial synergy between these analysis tools is demonstrated in this study.
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  • 86
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    Journal of thermal analysis and calorimetry 59 (2000), S. 23-31 
    ISSN: 1572-8943
    Keywords: DSC ; fullerene ; glass transition ; star-like polystyrene ; segmental dynamics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Segmental dynamics around Tg in the 4- and 6-arm fullerene (C60) core star-like polystyrenes with different preset arm lengths was studied by DSC as compared to that in the linear PS and PS/C60 blend. The ‘anomalies’ in glass transition behavior were found for the stars including both suppression and facilitation of segmental motion, and pronounced dynamic heterogeneity within a transition range. The results are interpreted in terms of breakdown of intermolecular cooperativity of segmental motions and PS-C60 interactions.
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  • 87
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    Journal of thermal analysis and calorimetry 59 (2000), S. 675-680 
    ISSN: 1572-8943
    Keywords: conducting polymer ; DSC ; kinetic analysis ; PPV ; TG
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The title polymer was obtained electrochemically by the reduction of 4,4'-bis(dibromomethyl)-2,2'-dimethoxybiphenyl under very smooth conditions. The DSC and TG/DTG curves registered at four different heating rates showed that the polymer is stable in air up to 150°C, where smooth degradation starts. Above 300°C, decomposition is fast and exothermic (ΔH= –323 J g–1) . The activation energy (116±4 kJ mol–1 ) was determined by Ozawa's method.
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  • 88
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    Journal of thermal analysis and calorimetry 59 (2000), S. 721-727 
    ISSN: 1572-8943
    Keywords: ageing ; annealing ; DSC ; polyaniline ; relaxation transition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Thermally treated films of polyaniline-emeraldine base (PANI-EB) cast from NMP solution were studied by using differential scanning calorimetry. Dependence of the thermodynamic parameters of the relaxation transitions on temperature and annealing period as well as the effect of the thermal history of the samples upon the crosslinking processes were investigated. For the first time DSC analysis of PANI-EB films after prolonged ageing was performed. It was found that relaxation transitions can be registered only for crosslinked PANI-EB. The crosslinking processes proceed both upon short-time heating of the polymer studied over80°C and during long-time storage at room temperature.
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  • 89
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    Journal of thermal analysis and calorimetry 59 (2000), S. 711-719 
    ISSN: 1572-8943
    Keywords: cure ; dicyandiamide ; DSC ; epoxy ; hermetic ; solvent
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The curing characteristics of adicyandiamide-cured epoxy system under the influence of solvents in a closed environment were studied by means of isothermal differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FTIR). The DSC analyses revealed that the presence of solvent results in decreases in the curing exotherm, the initial curing rate, the glass transition temperature, the reaction rate and the reaction order of the epoxy resin. The greatest decreases were caused by the solvent with the highest boiling temperature. A change in temperature-dependent curing route due to the heat absorbed during solvent evaporation is responsible for the difference. The FTIR analyses confirmed that the composition of the cured resin is affected by the solvent, the curing temperature and the specimen configuration. As compared with those obtained from open systems, specimens produced in a closed environment have an enhanced curing exotherm, initial curing rate, glass transition temperature, reaction rate and reaction order because of the retention of volatile catalytic by-products.
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  • 90
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    Journal of thermal analysis and calorimetry 59 (2000), S. 837-846 
    ISSN: 1572-8943
    Keywords: DSC ; γ-irradiation ; laser Raman ; microelectrophoresis ; XRD ; zeta-potential ; zirconium hydroxide ; ZrO2
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Zirconium hydroxide particles produced by rapid precipitation at pH 10.4, 7 or 2 were subjected toγ-irradiation up to a final dose of 20 MGy. The effects of the γ-irradiation were examined by X-ray powder diffraction, laser Raman spectroscopy, differential scanning calorimetry and microelectrophoretic measurements. It was found that γ-irradiation had no influence on the behaviour of zirconium hydroxide during calcination and subsequent cooling. The results of microelectrophoretic measurements showed that γ-irradiation influences the surface properties of zirconium hydroxide as a function of the precipitation pH. Zirconium hydroxide precipitated at pH 2 proved to be the most susceptible to γ-irradiation, while the sameγ-irradiation had very little (if any) effect on the surface properties of zirconium hydroxide precipitated at pH 10.5. After γ-irradiation, the electrophoretic mobility of zirconium hydroxide precipitated at pH 2 was increased at both low and high pH, thereby indicating an increase in its adsorption capacity. The analogy observed between the pH-dependence of the effects of γ-irradiation on the electrokinetic behaviour of zirconium hydroxide and the influence of ball-milling on the thermal behaviour of zirconium hydroxide [8] suggested that the susceptibility of amorphous zirconium hydroxide increases with decrease of the precipitation pH.
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  • 91
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    Journal of thermal analysis and calorimetry 61 (2000), S. 607-614 
    ISSN: 1572-8943
    Keywords: composted materials ; DSC ; thermal characterization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Differential scanning calorimetry (DSC) was applied to the study of material composted from sawdust, used coffee, farmyard manure and the organic fraction of domestic solid waste. Composting trials were carried out in Morocco and samples were collected after different periods of composting. The results obtained provided evidence that sawdust substrate is not a suitable source for composting due to the high content of lignin; samples from used coffee are characterized by a degree of aromaticity that is lower and a functional group heterogeneity that is higher than those of organic wastes from manure and the organic fraction of domestic wastes. The latter organic waste substrates appear to be easily degraded and humified and to give DSC curves that at the end of composting are vary close to those of native soil humic acids.
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  • 92
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    Journal of thermal analysis and calorimetry 61 (2000), S. 711-718 
    ISSN: 1572-8943
    Keywords: DSC ; PEG ; T-CR-T
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A modified isoconversional method is applied to perform the kinetic analysis of non-isothermal processes. The solidification process of a polyethylene glycol with a mean molecular of 4000 (PEG 4000) was here analyzed. It was stated that the Avrami model provides a good description of the solidification process. Temperature-cooling rate-transformation diagrams were constructed and there was a good agreement between experimental data and the calculated T-CR-T curves. Moreover, morphological qualitative analysis has been performed by means of scanning electron microscopy.
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  • 93
    ISSN: 1572-8943
    Keywords: chiral complex ; DSC ; hydrate ; optical resolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Thermal behaviour of O,O'-dibenzoyl-(2R,3R)-tartaric acid (DBTA), its monohydrate, and its potential supramolecular compounds with achiral alcohols and phenols were investigated with TG, DSC, EGD. The structural differences among the anhydrous DBTA, its monohydrate, and the supramolecular derivatives were investigated with X-ray powder diffraction. The thermal behaviour of DBTA-supramoleculars with isopropyl, tert-butyl, and 5-cyclohexyl alcohols is found to be similar to each other but essentially different from that of both DBTA and its monohydrate. On heating they melt and decompose between 60–180°C while they loose in one or two steps the bound alcohol. The thermal stability of the supramolecular compounds increases with the boiling point of the alcohol component. According to the X-ray powder diffraction patterns each supramolecular substance has different structure, that may also result in the different thermal stability of the compounds. The molar ratio of DBTA:achiral alcohol samples is 1:1.01–1:1.57 estimated from the corresponding mass losses. The XRD patterns of the prepared two DBTA-phenol materials are different from those of DBTA-achiral alcohol samples. The phenol compounds melt with slow mass losses and give an endothermic peak between 73–83°C but the melting point of the anhydrous DBTA cannot be observed. DBTA:phenol molar ratio is estimated to be 1:0.41 and 1:0.65 for phenol and 2-methylphenol, respectively.
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  • 94
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    Journal of thermal analysis and calorimetry 61 (2000), S. 771-778 
    ISSN: 1572-8943
    Keywords: burning rate ; DATH ; DSC ; TG ; thermal decomposition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The thermal decomposition characteristics of1,7-diazido-2,4,6-trinitrazaheptane (DATH) and multi-component systems containing DATH were studied by using DSC, TG and DTG techniques. Three –NO2 groups in the DATH molecule break away first from the main chain when DATH is heated up to 200°C. Following this process, the azido groups and the residual molecule decompose rapidly to release a great deal of heat within a short time. In the multi-component systems, DATH undergoes a strong interaction with the binder of the double-base propellant and a weak interaction with RDX. The burning rates of the two propellants were determined by using a Crawford bomb. The results showed that the burning rate rises by about 19–66% when 23.5%DATH is substituted for RDX in a minimum smoke propellant. Meanwhile, the N2 level in the combustion gases is enhanced, which is valuable for a reduction of the signal level of the solid propellant.
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  • 95
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    Journal of thermal analysis and calorimetry 62 (2000), S. 51-62 
    ISSN: 1572-8943
    Keywords: DSC ; kinetic models ; protein denaturation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract New approaches to the analysis of differential scanning calorimetry (DSC) data relating to proteins undergoing irreversible thermal denaturation have been demonstrated. The experimental approaches include obtaining a set of DSC curves at various scanning rates and protein concentrations, and also reheating experiments. The mathematical methods of analysis include construction of a linear anamorphosis and simultaneous fitting of a theoretical expression for the dependence of the excess heat capacity on temperature to a set of experimental DSC curves. Different kinetic models are discussed: the one-step irreversible model, the model including two consecutive irreversible steps, the Lumry and Eyring model with a fast equilibrating first step, and the whole kinetic Lumry and Eyring model.
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  • 96
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    Journal of thermal analysis and calorimetry 60 (2000), S. 117-121 
    ISSN: 1572-8943
    Keywords: biopol/polyamide 6 blends ; DSC
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Blends obtained from Biopol D600G and polyamide 6 reveal in DSC investigations multiphase structure with a distinct crystalline polyamide 6 phase. Due to rapid crystallization of the polyamide 6 the crystallization of the Biopol D600G is retarded. The grade of crystallization of Biopol D600G is lower in the blends than in the pure state, as calculated from the melting enthalpies. Crystallization of polyamide 6 in the blends is faster and results in increasing of the grade of crystallization of polyamide 6 phase comparing to the unblended component.
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  • 97
    ISSN: 1572-8943
    Keywords: cyanazine ; DSC ; kinetics ; thermal stability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Cyanazine was taken as an example for investigations under the influence of different conditions on thermal decomposition of triazine herbicides. DSC measurements were carried out under atmospheric pressure and hermetically closed, under pressure 1.3 kPa. The influence of the pressure on the constant reaction rate of decomposition of cyanazine was discussed. It was also proved that the predicted reaction constant rates from isothermal and non-isothermal measurements are consistent.
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  • 98
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    Journal of thermal analysis and calorimetry 60 (2000), S. 111-116 
    ISSN: 1572-8943
    Keywords: DMTA ; DSC ; HMDI ; mesogenic chain extender ; polyurethane
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract New polyurethanes with mesogenic units in the main chain due to the use of a liquid crystalline chain extender were synthesized from 4,4'-methylenebis(cyclohexyl isocyanate) (HMDI)using diisocyanates of different trans, trans isomer content, a low molecular diol4,4'-bis(6-hydroxyhexoxy)biphenyl (BHHBP) and a high molecular poly(hexyleneadipate)diol (PHA). The growth of trans, trans isomer content in HMDI used to syntheses of PU induces monotonic growth of melting point, rectilinear growth of crystallization temperatures and the growth of crystallization enthalpy, both for hard segment polyurethanes and block polyurethanes. The increase of trans, trans isomer content in HMDI increases also glass transition temperatures and dynamic storage modulus of the polyurethanes.
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  • 99
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    Journal of thermal analysis and calorimetry 60 (2000), S. 163-166 
    ISSN: 1572-8943
    Keywords: comparison ; decomposition ; DSC ; enthalpy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The comparison of thermal and calorimetric properties of metal derivatives of 6-aminopicolinic acid (APH) is presented. The salts and complexes of APH with Cr(III), Cd(II), Cu(II), Ni(II), Pb(II), Co(II)and Ag(I) have been studied by TG-DTA and DSC methods up to 1200°C in a nitrogen atmosphere. Decomposition processes are proposed. The decarboxylation, deamination and carbonation of the organic fragments of molecules take place. The compounds decompose to metal or to metal oxides. The values of the transition enthalpy were determinated.
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  • 100
    ISSN: 1572-8943
    Keywords: DMA ; DSC ; physical aging ; TGDDM epoxy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The physical aging of a system containing tetraglycidyl-4-4′-diaminodiphenylmethane (TGDDM), with a multifunctional novolac glycidyl ether resin hardened by 4,4′-diaminodiphenylsulphone (DDS) has been investigated by differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA). Samples fully cured were aged at temperatures between 200 and 250°C, during periods of time from 1 to a maximum of 336 h. Furthermore, the dynamic mechanical relaxation behaviour annealed at temperature of 220°C, was studied, aging during 24 and 168 h. The effect of the enthalpy relaxation during DSC heating scan is shown by the presence of an endothermic peak whose position and intensity depends on the aging conditions, both temperature and time. DSC studies suggest that enthalpy relaxation increases gradually with aging time to a limiting value for each temperature where structural equilibrium is reached. DMA results show that the effect of aging is to cause chain stiffening and a decrease in the height of the peak value of the loss factor.
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