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  • Polymer and Materials Science  (32)
  • ELECTRONICS AND ELECTRICAL ENGINEERING  (3)
  • 1
    Electronic Resource
    Electronic Resource
    Molecular weight dependence of the diffusion coefficient for the polystyrene-toluene system (1989)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 27 (1989), S. 465-468 
    Details
    ISSN: 0887-6266
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/polb.1989.090270216
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  • 2
    Electronic Resource
    Electronic Resource
    Inducement of apparent anisotropic superstructure in amorphous cold drawn polyethylene terephthalate (1975)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Letters Edition 13 (1975), S. 303-312 
    Details
    ISSN: 0360-6384
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1975.130130511
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  • 3
    Electronic Resource
    Electronic Resource
    Effects of enzymes and gamma irradiation on the tensile strength and morphology of poly(p-dioxanone) fibers (1984)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 29 (1984), S. 1865-1877 
    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: The objective of this study was to examine how and to what extent a new degradable polymeric fiber, poly(p-dioxanone), used as a surgical suture material, degrades in the presence of enzymes and after γ-irradiation. The degradation of the fiber was studied mechanically using an Instron and morphologically by SEM. Both esterase and trypsin enzymes and their corresponding buffer controls were used. The fibers were γ-irradiated at the dosages ranging from 0 to 20 Mrad, immersed in the solution for up to 70 days, and then removed for tensile strength and morphological examinations. It was found that γ-irradiation alone lowered the tensile strength of PDS fibers and made them more susceptible to hydrolysis. Esterase and trypsin did not accelerate the hydrolytic degradtion of this fiber to any significant level. Both γ-irradiation and enzymes influenced the gross morphological characteristic of PDS fibers when they were subjected to hydrolysis. The most important morphological observations were the formation of surface cracks and chips on the fibers and the subsequent peeling of the chips. Enzyme-treated PDS fibers exhibited similar morphological findings but the size of the chips was smaller. The morphological observations of PDS fibers were consistent with the tensile strength data.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1984.070290537
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  • 4
    Electronic Resource
    Electronic Resource
    Hydrolytic degradation of polyglycolic acid: Tensile strength and crystallinity study (1981)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 26 (1981), S. 1727-1734 
    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: The hydrolytic degradation of polyglycolic acid (PGA) was studied by examining the changes of tensile strength and the level of crystallinity of the suture material. It was found that the breaking stress decreased from 6.369 × 10-1 at 0 day to 3.97 × 10-3 Newton/Tex at 49 days. The sigmodial shape of the stress-strain curves gradually disappeared with increase in the duration of in vitra degradation. The endpoint titration method used to assess the degree of degradation beyond the period of measurable tensile strength showed that the percent of PGA degraded were 42, 56, and 70% at 49, 60, and 90 days, respectively. The level of crystallinity of PGA at various durations of degradation exhibited an initial increase in the degree of crystallinity from 40% at 0 day to an upper limit of 52% at 21 days, then gradual decrease to 23% at 90 days. This observation is essentially parallel to hydrolysis of cellulose and polyethylene terephthalate. The concept of microfibrillar structure of fibers provides the basis for the proposed degradation mechanism of PGA in vitro. It is believed that degradation proceeds through two main stages which are different in rate of degradation.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1981.070260527
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  • 5
    Electronic Resource
    Electronic Resource
    Concentration dependence of solvent self-diffusion coefficients (1987)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 34 (1987), S. 587-592 
    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: The concentration dependence of solvent self-diffusion coefficients is examined near the pure solvent limit. It is shown that it is possible to explain an apparently anomalous concentration dependence for the solvent self-diffusion coefficient at high penetrant mass fractions within the framework of the free-volume theory of transport.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1987.070340213
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  • 6
    Electronic Resource
    Electronic Resource
    Study of critical phenomena of polystyrene - poly(vinyl methyl ether) blends by solid state NMR (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 41 (1990), S. 2311-2325 
    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: Thermally induced phase separation in PS/PVME blends was studied by solid state NMR. The proton spin - lattice relaxation in both the laboratory and the rotating frame were measured for the entire range of blend composition. Under conditions in which the blends are said to be compatible by other techniques T1pH results obtained at -5°C showed microheterogeneity at a 10-°A scale. T1pH values at room temperature are closer to the longer relaxation time of PS than that expected from simple weighted average of the relaxation times of the constituent homopolymers. This indicates incomplete averaging by spin diffusion and a restraining effect of PS on segmental motions of PVME. The blends were heated to cause phase separation and quenched. From the biphasic decay of 13C magnetization, the compositions of the separated phases were estimated to give a lower critical solution temperature phase diagram. NMR relaxation in PVME blends with PS molecular weights of 9, 100, and 900 K were compared.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1990.070410933
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  • 7
    Electronic Resource
    Electronic Resource
    The effect of ionic electrolytes on hydrolytic degradation of biodegradable polymers: Mechanical and thermodynamic properties and molecular modeling (1993)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 31 (1993), S. 1759-1769 
    Details
    ISSN: 0887-624X
    Keywords: biodegradable polymers ; molecular modeling ; MNDO ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The purpose of this study was to examine the effect of electrolytes on the hydrolytic degradation of synthetic biodegradable polymers and fibers. Both Polyglycolic acid (PGA) and poly(glycolide-lactide) copolymer (PGL) were used for the study. Four different electrolytes were used: NaCl, LiCl, MgCl2, and ZnCl2. The electrolyte effect was evaluated in terms of the change in tensile properties, water uptake, and surface morphology of the polymers and fibers. It was found that the NaCl and MgCl2 solutions significantly retarded the hydrolytic degradation of both PGA and PGL as evidenced in the prolonged retention of tensile breaking strength of these fibers when compared to deionized water control. Increasing the concentration of the electrolyte retarded the hydrolytic degradation rate further. These mechanical property data agreed well with the rate and amount of water uptake of PGA and could be correlated with the chemical potential difference of water between the electrolyte solution and pure water. The effect of electrolyte was further analyzed by theoretical calculation. Semiemperical molecular orbital calculations indicated that hard cations like Mg, Li, and Zn strongly coordinated to the polar sites of the polymer chain segments (—C=O) and severely disrupted their solvation spheres. Such a disruption was reflected in the smaller amount and slower rate of water uptake by PGA, and thus a slower rate of hydrolytic degradation as evident in the retention of tensile breaking strength. © 1993 John Wiley & Sons, Inc.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1993.080310715
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  • 8
    Electronic Resource
    Electronic Resource
    Dimethyltitanocene-induced surface chemical degradation of synthetic biodegradable polyesters (1994)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 32 (1994), S. 949-960 
    Details
    ISSN: 0887-624X
    Keywords: dimethyltitanocene ; biodegradable polymers ; poly(glycolic acid) ; surface degradation ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The purpose of this research was to selectively alter the rate of surface degradation of linear aliphatic polyesters without adversely affecting their bulk properties by way of functional group transformation, where the surface ester linkages would be converted to vinyl ether functionalities with dimethyltitanocene. It has been observed that dimethyl titanocene causes surface degradation of poly (glycolic acid) without adversely affecting its bulk properties, such as Mv, bursting strength, and thermal properties The vinvl ether resulting from the conversion of the PGA ester groups was unstable under ambient conditions, and further reacted by polymer chain scissioning, as was observed from measurements of molecular weight. © 1994 John Wiley & Sons, Inc.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1994.080320516
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  • 9
    Electronic Resource
    Electronic Resource
    Plasma surface modification of synthetic absorbable sutures (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Biomaterials 3 (1992), S. 131-146 
    Details
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: The aim of the study was to examine the feasibility of using plasma surface modification technology to alter the hydrolytic degradation rate of commercial synthetic absorbable sutures. Size 2-0 Dexon, Vicryl, PDSII, and Maxon sutures were tested. They were treated by two different surface modification techniques: parylene deposition and plasma gases (Methane, trimethylsilane, and tetrafluoroethene). The thickness of surface treatment ranges from 200 to 1000°AR. The treated sutures were subject to in vitro hydrolytic degradation in phosphate buffer of pH = 7.4 at 37°C for up to 120 days. The tensile breaking strength, weight loss, surface wettability, bending stiffness, and surface morphology were evaluated. The results indicated that the concept of plasma surface treatment for altering the hydrolytic degradation of synthetic absorbable sutures was feasible, and the level of improvement depended on the type of sutures, the treatment conditions, and the duration of hydrolysis. Vicryl and PDSII sutures showed overall the best improvement in tensile strength retention among the four commercial sutures. Dexon and Maxon sutures, however, exhibited only marginal improvement. The observed improvement in tensile strength retention appeared to be related to the increasing hydrophobicity of the sutures. The surface treatments did not adversely affect the bending stiffness of the sutures and no visible surface morphological changes were observed. Refinements and optimization of the surface treatment conditions are needed for achieving the maximum advantage of the proposed concept, particularly shielding the harmful effect of uv during plasma treatment.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jab.770030209
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  • 10
    Electronic Resource
    Electronic Resource
    A comparison of a new polypropylene suture with prolene (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Biomaterials 4 (1993), S. 169-181 
    Details
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: The purpose of this paper is to examine the performance of the newly available monofilament polypropylene suture (Surgipro) manufactured by U.S. Surgical and compared it with commercial Prolene sutures for determining the merit of this new suture. Two different sizes of Surgipro sutures were esused. They were 4/0 and 0 sizes and were tested in terms of their fundamental properties: level of crystallinity, melting temperature, fiber morphology, and mechanical properties including knot strength and knot security. The effect of three different sterilization methods on the mechanical and fundamental properties of the new polypropylene (PP) sutures was also examined. In general, the new Surgipro sutures performed as good as Prolene sutures in terms of mechanical properties; but there were some differences in fundamental properties between these two types of PP sutures, particularly in finer size PP sutures. The major differences were in interior fiber morphology, level of crystallinity, and melting temperature. Surgipro suture fibers showed homogeneous interior morphology, while Prolene fibers exhibited two distinctive fiber morphologies. These two types of PP suture fibers also responded differently to the three sterilization methods tested. Surgipro sutures are less affected by different sterilization methods than the same size Prolene control. Except for the Co60 gamma sterilization, Surgipro suture fibers did not exhibit statistically significant differences in tensile breaking strength between sterilized and control. Ethylene oxide and autoclave sterilized Prolene suture fibers, however, showed statistically (p 〈 0.05) consistently lower tensile breaking strength than their unsterilized controls. One should be aware of the fact that suture manufacturers are constantly improving their manufacturing processes. The difference between these two types of PP suture fibers may disappear in the future. © 1993 John Wiley & Sons, Inc.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jab.770040209
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