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  • 1
    Electronic Resource
    Electronic Resource
    Magnetic phase diagram of dilute Cr-Al system from electrical resistivity studies on single crystals (1987)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 61 (1987), S. 3994-3996 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Electrical resistivity (ρ) studies as a function of temperature are reported for the first time, on single-crystal samples of dilute Cr-Al alloys containing 0.23-, 0.52-, 1.02-, 1.41-, 1.91-, 2.99-, and 4.53-at. % Al with a view to resolve the unusual and complex features reported for the magnetic phase diagram of Cr-Al system. ρ(T) anomalies are obtained in the region of TN for all the concentrations, contrary to earlier conclusions based on data on polycrystalline samples, that antiferromagnetism disappears in the concentration c range 2〈c〈4 at. % Al. The TN vsAl content plot shows a sharp fall initially up to 1.02 at. % beyond which it rises with increase in Al content. A C-I phase boundary region has been identified in the magnetic phase diagram by utilizing the infrared reflectivity data reported earlier on the same samples as complementary evidence.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.338556
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  • 2
    Electronic Resource
    Electronic Resource
    Structure-property relations in non-linear, segmented copolyureas formed by reaction injection moulding, RIM (1987)
    Springer
    Polymer bulletin 18 (1987), S. 517-523 
    Details
    ISSN: 1436-2449
    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: Summary Segmented copolyureas have been formed by RIM using a MDI-based polyisocyanate (RMA400) and mixtures of a polyether triamine (Jeffamine T5000) and diethyltoluene diamine (DETDA) chain extender. Hard segment (HS) content was varied between 35 and 65% w/w at a constant overall stoichiometric ratio of -NCO to -NH2 groups of 1.03. All the copolyureas were translucent and DSC confirmed their totally amorphous structure. The copolyureas were shown by dynamic mechanical-thermal analysis to possess a two-phase morphology comprising polyether soft segments of constant Tgs of −40°C and aromatic polyurea hard segments with TgH increasing from 215 to 236°C as HS content increased. The ratio of flexural moduli at −35 and 65°C, decreased from 4.9 to 2.2 at 65% HS, and mechanical integrity was retained at temperatures in excess of 250°C, with flexural moduli of 10MPa at 270°C. Tensile stress-strain studies showed the polyureas to range from semi-rigid elastomers to stiff plastics with moduli greater than IGPa. Postcuring significantly improves materials toughness at high HS contents.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00255336
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  • 3
    Electronic Resource
    Electronic Resource
    The opto-mechanical behaviour of diacetylene-containing segmented block copolymers (1991)
    Springer
    Polymer bulletin 27 (1991), S. 353-359 
    Details
    ISSN: 1436-2449
    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: Summary The effects of mechanical deformation on the optical properties of segmented copolyurethanes have been studied using resonance Raman spectroscopy. Linear elastomeric and glassy copolyurethanes, each containing diacetylene-urethane (DA-U) hard segment domains dispersed in a continuous polyether-urethane (PE-U) matrix, were prepared in bulk and themally cross-polymerised in the solid state. The crosslinked copolymers produced intense Raman spectra in which the $${\text{C}} \equiv {\text{C}}$$ triple bond stretching Raman band at ∼2080 cm-1 is well defined and shifts to lower frequency under the application of tensile stress. Shifts in Raman spectra have been used to monitor stress concentrations around defects such as holes and notches machined into copolyurethane sheets. The copolyurethanes are readily applied as surface coatings to various subtrates, and their use as optically stress/strain-sensitive materials (optical strain sensors) is demonstrated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00294543
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  • 4
    Electronic Resource
    Electronic Resource
    Structure-property relationships in novel polydiacetylene-containing oligoester: Polyolefin blends (1993)
    Springer
    Polymer bulletin 30 (1993), S. 347-352 
    Details
    ISSN: 1436-2449
    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: Summary The paper describes thermal and mechanical properties of a series of novel blends prepared using a two-stage process which invloved solution blending a specially-synthesised diacteylene-containing oligoester (DOE) with a semi-crystalline poly[ethylene-co-(vinyl acetate)] (EVA), followed by conversion of the DOE to a polydiacteylene-containing oligoester (cp-DOE) by in situ thermal cross-polymerisation during moulding. Moulded blends range from ductile to brittle materials and give intense Raman spectra in which the C≡C stretching band at ∼2100 cm-1 is well-defined and shifts to lower wavenumber when the blends are subjected to tensile stress. For each blend composition, shifts in wavenumber were used to determine local stress in the cp-DOE component independently of the overall stress applied to blend.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00343071
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  • 5
    Electronic Resource
    Electronic Resource
    The relationship between structure and properties in titanium dioxide filled polypropylene (1993)
    Springer
    Polymer bulletin 30 (1993), S. 361-368 
    Details
    ISSN: 1436-2449
    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: Summary The effect of a pigment grade of titanium dioxide on the morphology, crystallisation and mechanical properties of a typical grade of isotactic polypropylene are described. Pigment particles are able to nucleate additional spherulites, and are incorporated within spherulitic and lamellar morphologies. Measurements of isothermal crystallisation rates using differential scanning calorimetry and hot-stage microscopy show that bulk crystallisation rate is increased by addition of the pigment due to the larger number of spherulites, while the growth rate of the spherulites is unchanged. Addition of the pigment increased tensile modulus, and reduced yield stress. The elongation at break and impact resistance were modulus, and reduced yield stress. The elongation at break and impact resistance were increased by the addition of pigment, showing that particle debonding processes can lead to toughening of the polypropylene matrix.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00343073
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  • 6
    Electronic Resource
    Electronic Resource
    The effects of hard segment content on microphase separation and physical properties of non-linear, segmented copolyureas formed by RIM (1989)
    Springer
    Polymer bulletin 22 (1989), S. 629-635 
    Details
    ISSN: 1436-2449
    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: Summary The properties of RIM-copolyureas formed from a polyether triamine and containing 30 to 70% by weight of MDI/DETDA hard segments (HS) were investigated. As-moulded (mould temperature 115°C) and postcured (200°C/1h) materials were compared using DSC, DMTA and tensile stress-strain measurements. Phase separation ratios (PSR) of as-moulded materials increased from 47 to 56% with increasing HS content. Postcuring increased PSR to ∼70% for all materials resulting in significant intensification of HS glass transition at TgH (220 to 250°C), and reduced mechanical damping and modulus-temperature dependence between −40 and 200°C. Agreement between experimental tensile moduli and those predicted by appropriate two-phase composite theory has confirmed the co-continuous morphology of these RIM-copolyureas over the entire composition range studied.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00718945
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  • 7
    Electronic Resource
    Electronic Resource
    Phase separation in segmented polyurethanes derived from mixtures of polyether polyols with different functionality (1996)
    Springer
    Journal of polymer research 3 (1996), S. 221-225 
    Details
    ISSN: 1572-8935
    Keywords: Segmented polyurethanes ; Phase separation ; Compatibility ; Polyol mixture ; Thermal transitions
    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 A series of segmented polyurethanes containing 60 wt° of hard segments (HS) was prepared from MDI (4,4′-diphenylmethane diisocyanate) ethylene glycol and mixtures of a polyoxyethylene end-capped polyoxypropylene triol and a polyoxyethylene end-capped polyoxypropylene diol. The effects of the content of polyether diol in polyether polyols on phase separation and properties was investigated by dynamic mechanical analysis (DMA), differential scanning calorimetry (DSC) and investigation of tensile properties. The DSC and DMA results indicate that the polyurethane derived from only polyether triol exhibits obvious phase separation and that the HS is immiscible with the SS, but that the HS is compatible with the HS for the polyurethane derived from polyether diol. As the content of polyether diol increases, the compatibility between HS and SS increases. As the content of polyether diol increases, the tensile strength. elongation. toughness and tear resistance of the polyurethanes increases. but their moduli decrease. The modulus-temperature dependence in the temperature region of −30 to 65 °C increases as the polyether diol content increases.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01493491
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  • 8
    Electronic Resource
    Electronic Resource
    Strain measurement in diacetylene-containing copolymers using Raman spectroscopy (1992)
    Springer
    Journal of materials science 27 (1992), S. 5958-5964 
    Details
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Rigid diacetylene-containing block copolymers are shown to have Raman spectra similar to those of polydiacetylene single crystals. The vibrational frequencies of certain main-chain Raman-active modes of the copolymers are sensitive to deformation which enables strain measurement to be made by following the shift in the Raman band positions. Measurements of the stress concentrations around defects in copolymer specimens during deformation have been carried out using Raman spectroscopy and they have been compared with theoretical analyses of stress concentrations. There is good agreement between the theoretical and experimental measurements and it has been demonstrated that the use of Raman spectroscopy allows the measurement of stress or strain in complex situations for which no theoretical solutions exist.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01119768
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  • 9
    Electronic Resource
    Electronic Resource
    Synthesis and properties of polydiacetylene-containing polyesters (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Polymer International 34 (1994), S. 23-33 
    Details
    ISSN: 0959-8103
    Keywords: polyesters ; diacetylenes ; cross-polymerisation ; DSC ; Raman spectroscopy ; tensile deformation ; Raman shift factors ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: A series of diacetylene-containing polyesters with number-average molar masses (GPC) in the range 900-4200 g mol-1 were prepared from terephthaloyl chloride and hexa-2,4-diyne-1,6-diol using benzoyl chloride as a monofunctional reactant for control of molar mass. Degrees of crystallinity were estimated from WAXD to be up to 29%. Correlations between molar mass, melting behaviour, degree of crystallinity and thermal cross-polymerisation of diacetylene-containing polyesters have been established using hot-stage microscopy, DSC and resonance Raman spectroscopy. The polyester with M̄n of 1264 g mol-1 gave the best balance between processability and the ability to cross-polymerise efficiently. Its degree of crystallinity before cross-polymerisation was estimated from WAXD measurments to be 24%, a value coincident with the percentage conversion of diacetylene units to polydiacetylene chains measured by 13C solid-state NMR. The optimum conditions for compression moulding the polyester to produce a material with a strong Raman spectrum involved heating under vacuum at 120°C for 6h after an initial 3 h heat-up period. The material thus produced gave an intense Raman C=C stretching band, which upon tensile deformation shifted linearly with strain to lower wavenumber by 12.0 cm-1 %-1. The potential use of the diacetylene-containing polyesters in the preparation of model blends for use in quantitative micromechanics studies of stress transfer between phases is briefly discussed.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pi.1994.210340105
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  • 10
    Electronic Resource
    Electronic Resource
    Polymers from renewable sources. III. Hydroxy-terminated myrcene polymers (1986)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 31 (1986), S. 1963-1975 
    Details
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: A range of hydroxy-terminated polymyrcenes has been prepared using hydrogen peroxide initiated polymerization of pyroysate grade, β-myrcene in n-butanol solution at 100°C. An oligomeric fraction, containing a large proportion of dimeric material formed via the Diels-Alder reaction, always accompanies the major polymeric fraction. Procedures are described for the removal of this oligomeric material. Polyols so prepared and purified had number average molecular weights (Mn) between 4000 and 2000 g mol-1 at low and high initiator concentrations, respectively, with corresponding number average functionalities (fn) between 1.3 and 2.3 and polydispersities (Mw/Mn) of ∼1.3. The microstructure of the polyols was investigated using NMR spectroscopy from which the main mode of propagation during polymerization of myrcene was deduced to be 1,4 addition across the conjugated double bonds. Glass transition temperatures of the polymyrcenes measured by differential scanning calorimetry were in the range -50-60°C.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1986.070310702
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