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  • 1
    Electronic Resource
    Electronic Resource
    The degradation of gel-spun poly(β-hydroxybutyrate) “wool” (1994)
    Springer
    Journal of polymers and the environment 2 (1994), S. 185-194 
    Details
    ISSN: 1572-8900
    Keywords: Poly(β-hydroxybutyrate) ; gel-spinning ; fiber ; photoacoustic spectroscopy ; nonwoven
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Energy, Environment Protection, Nuclear Power Engineering , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The apparent biodegradability and biocompatibility of the microbially produced polyester, poly(β-hydroxybutyrate) (PHB), has been the focus of much research by a number of authors with regard to its potential for use in packaging and medical implantation devices. PHB has recently been produced by gel-spinning into a novel form, with one possible application being as a wound scaffolding device, designed to support and protect a wound against further damage while promoting healing by encouraging cellular growth on and within the device from the wound surface. This new nonwoven form combines a large volume with a low mass, has an appearance similar to that of “cotton wool,” and has been called “wool” because of this similarity. The hydrolytic degradation of this wool was investigated in an accelerated model of pH 10.6 and temperature 70°C. It was determined that the PHB wool gradually collapsed during degradation. The surface area-to-volume ratio was concluded to be a primary influencing factor. Degradation was characterized by a reduction in the glass transition temperatures and melting points and a fusion enthalpy peak of maximum crystallinity, (88%), which coincided with the point of matrix collapse.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02067444
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  • 2
    Electronic Resource
    Electronic Resource
    Plasma oxidation of polymers (1986)
    Springer
    Plasma chemistry and plasma processing 6 (1986), S. 401-416 
    Details
    ISSN: 1572-8986
    Keywords: Plasma oxidation ; polymers ; copolymers ; mechanism ; plasma-developable resists
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract The rates of plasma oxidation have been measured for homopolymers of several monomers and for copolymers of methyl methacrylate with styrene and vinyl naphthalene. Our results show that relatively small amounts of the aromatic component in the copolymer convey substantially increased resistance to plasma oxidation. Current knowledge of the mechanisms of plasma oxidation is reviewed and new mechanistic explanations are suggested. The implications for improved design of plasma-developable resists systems are considered.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00565552
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  • 3
    Electronic Resource
    Electronic Resource
    A comparison of friction in hydrogel and polyurethane materials for cushion-form joints (1993)
    Springer
    Journal of materials science 4 (1993), S. 515-520 
    Details
    ISSN: 1573-4838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: The use of a thin layer of a compliant material as a bearing surface in human replacement joints has been found to promote fluid-film lubrication in the joint during continuous movement. However, during periods of continuous loading and little or no movement the fluid film may break down and the articulating surfaces may come into direct contact. This study considers the friction of three compliant materials under conditions of continuous loading and slow sliding velocities. The friction of a non-porous polyrethane and two porous hydrogel polymers, a terpolymer and a semi-interpenetrating network, was studied. Friction was measured between a hard spherical slider and a thin layer of the compliant material. Sliding was carried out in the presence of deionised water or new-born-calf serum as the lubricant. The friction was measured at the start up of motion, after prolonged periods of static loading, and during the subsequent sliding at a constant velocity. All three materials were found to give lower friction during steady-state sliding than at start up. Friction was also higher when serum was used as a lubricant. However, the porous hydrogels gave lower friction than the non-porous polyurethane, especially at start up. The terpolymer hydrogel gave the lowest friction values of the three materials, both at start up and in the steady state.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00120132
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  • 4
    Electronic Resource
    Electronic Resource
    Poly-α-ester degradation studies. II. Thermal degradation of poly(isopropylidene carboxylate) (1973)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 11 (1973), S. 1079-1093 
    Details
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The thermal degradation of poly(isopropylidene carboxylate) has been studied over the temperature range 200-800°C by using the kinetic and analytical techniques described in Part I of this series. Over a wide range of temperature, tetramethyl glycollide, acetone, carbon monoxide, and, to a lesser extent, methacrylic acid are observed when the products are rapidly swept away from the reaction zone. As decomposition temperature is increased, tetramethyl glycollide takes on the role of an intermediate, the more stable products carbon monoxide and acetone being formed from it. At the highest temperature examined, carbon monoxide begins to predominate, and its formation is accompanied by formation of small amounts of a carbonaceous residue. When the reaction products are allowed to remain in the reaction zone, which is possible at the lower end of the temperature range, methacrylic acid becomes the major product. This is interpreted as a dual decomposition route, involving the tetramethyl glycollide intermediate. Kinetic studies have shown that the decomposition is a first-order process and that the first-order rate constant k is related to temperature (T) by the expression: \documentclass{article}\pagestyle{empty}\begin{document}$$ k = 4.1 \times 10^7 e^{{{ - 27,200} \mathord{\left/ {\vphantom {{ - 27,200} {RT}}} \right. \kern-\nulldelimiterspace} {RT}}} {\rm sec}^{ - {\rm 1}} $$\end{document} The results are interpreted in terms of an intramolecular ester interchange process involving tetramethyl glycollide as the primary decomposition product.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1973.170110514
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  • 5
    Electronic Resource
    Electronic Resource
    Poly α-ester degradation studies. V. Thermal degradation of polyglycollide (1973)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 11 (1973), S. 2045-2056 
    Details
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The thermal degradation of polyglycollide [poly(methylene carboxylate)] has been studied over the temperature range 250-400°C by using the combined kinetic and analytical technique previously described. The results obtained from thermogravimetry and product analysis were in many ways similar to those from previous work involving higher poly-α-esters. Thus the reaction was predominantly first-order and the major degradation product was glycollide monomer. This confirms the observations of Carothers and is best interpreted in terms of an intramolecular ester interchange process. Kinetic studies have shown that the first-order rate constant k is related to temperature T by the expression: \documentclass{article}\pagestyle{empty}\begin{document}$$ k = 2.1 \times 10^8 e^{ - 32,{{600} \mathord{\left/ {\vphantom {{600} {RT}}} \right. \kern-\nulldelimiterspace} {RT}}{\rm sec}^{ - {\rm 1}} } $$\end{document} The results from gas evolution analysis showed consistent and marked deviation from first-order behavior. This is interpreted in terms of the greater sensitivity of this technique to traces of acidic degradation products. Solution viscometry was used to demonstrate the effect of degradation conditions on molecular weight change in both thermogravimetric and gas evolution techniques.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1973.170110823
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  • 6
    Electronic Resource
    Electronic Resource
    Studies in ring-opening polymerization. IV. Thermal polymerization of phenyl-substituted 1,3-dioxolan-2,4-diones (1976)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 14 (1976), S. 949-960 
    Details
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The effect of C-5 phenyl substituents on the thermal decomposition of the 1,3-dioxolan-2,4-dione ring has been examined. Unlike the dimethyl-substituted ring, 5-methyl-5-phenyl-1,3-dioxolan-2,4-dione decomposes smoothly in dry nonhydroxylic solvents to yield polymer and carbon dioxide. The introduction of a second C-5 phenyl substituent produces a similar but more rapid decomposition, with the added complication of a competing ring fragmentation leading to ketone formation. An analogy is drawn between the observed behavior of the phenyl-substituted 1,3-dioxolan-2,4-diones and that of the previously studied 1,3,2-dioxanthiolan-4-one 2-oxides. These monomers therefore provide another example of the thermal polymerisation mechanism first observed with 5,5-dimethyl-1,3,2-dioxathiolan-4-one 2-oxides. In these reactions the rate-determining step is the first-order ring-scission process leading to the formation of an α-lactone intermediate. This intermediate then takes part in a very rapid chain-growth process which governs the characteristics of the polymer formed.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1976.170140415
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  • 7
    Electronic Resource
    Electronic Resource
    Poly α-ester degradation studies. IV. Rheological studies of polymer degradation (1973)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 11 (1973), S. 2031-2043 
    Details
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The Farol-Weissenberg rheogoniometer has been used to follow molecular weight changes during the degradation of certain poly-α-esters in the melt state. By observing the change in melt viscosity at low shear rates it had been shown that the decomposition of the poly(isopropylidene carboxylate) is substantially first-order with respect to the molecular weight of the residual polymer. The derived kinetic parameters are in good agreement with those previously obtained by other techniques. This provides a substantial piece of supporting evidence for the view that degradation takes place predominantly by intramolecular ester interchange involving the formation of 1,1,4,4,-tetramethylglycollide. The introduction of β-chlorine atoms into the polymer structure leads to a more complex degradation pattern. Thus the presence of a single β chlorine atom per repeat unit, as in poly(3-chloro-2-methyl-2-hydroxypropionic acid) leads to a substantially similar dependence on molecular weight with the added complication of progressive crosslinking which becomes more apparent in later stages of the reaction. This crosslinking reaction plays an increasingly important part as the extent of chlorination of the polymer is increased. In addition, the presence of chlorine leads to an increased sensitivity of the degradation reaction to the presence of oxygen.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1973.170110822
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  • 8
    Electronic Resource
    Electronic Resource
    Poly-α-ester degradation studies. III. Effect of β-chlorination on polymer degradation (1973)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 11 (1973), S. 2343-2355 
    Details
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The thermal degradation of two β-chlorinated versions of poly(isopropylidene carboxylate) has been studied by the combined thermogravimetric and gas evolution techniques described previously. Poly(3-chloro-2-methyl-2-hydroxypropionic acid) was found to decompose by a predominantly first-order process which was characterized by kinetic parameters similar to those obtained for poly(isopropylidene carboxylate). These are interpreted in terms of an intramolecular ester-exchange process. As the reaction proceeds intermolecular elimination of hydrogen chloride leads to crosslinking and ultimately to the formation of a carbonaceous char. This process is much more marked in the randomly β-chlorinated analog of poly(isopropylidene carboxylate). With this polymer, drastic deviation from first-order behavior is observed in thermogravimetric results, even in the early stages of reaction. Gas evolution analysis, being more influenced by degradation fragments having an appreciable vapor pressure, yields reasonable first-order data and indicates that the intramolecular interchange mechanism is still an important process. In general, the introduction of β-chlorine atoms is seen to reduce the rate of thermal decomposition of poly-α-esters.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1973.170110923
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  • 9
    Electronic Resource
    Electronic Resource
    Poly-α-ester degradation studies. I. Introduction: Design and construction of equipment (1973)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 11 (1973), S. 1069-1077 
    Details
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The various types of polyester degradation known to occur at elevated temperature are briefly summarized with particular reference to features of potential diagnostic value. Although little is known of poly-α-ester degradation in particular, examination of work on other linear polyesters indicates the spectrum of analytical and kinetic information that will be needed to characterize the degradation of poly-α-esters of various structures. On the basis of this review, an apparatus has been designed which enables kinetic information to be simultaneously obtained by thermogravimetry, gas evolution analysis, and rheological studies of the residual polymer melt. In addition a gas sampling procedure enables twin-column gas-liquid chromatographic analysis to be carried out on the degradation products. Samples of the chromatographically separated degradation products are collected in a microcollector cell for infrared and mass spectrometric analysis. Other refinements include in-line filament and Curie-point pyrolysis techniques.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1973.170110513
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  • 10
    Electronic Resource
    Electronic Resource
    Poly-α-ester degradation studies. VI. Thermal degradation of poly(3-pentylidene carboxylate) (1980)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 18 (1980), S. 123-146 
    Details
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The thermal degradation of poly(3-pentylidene carboxylate) has been studied kinetically over the temperature range 200-300°C using thermogravimetry, gas evolution analysis, and rheogoniometry together with isolation and analysis of the reaction products. The observed behavior is completely different from that previously reported for poly(isopropylidene carboxylate) and poly(methylene carboxylate). Whereas in the latter cases the decomposition occurs by a first-order intramolecular ester interchange process characterized by an activation energy in the region of 27 kcal mole-1, poly(3-pentylidene carboxylate) decomposition occurs by random chain scission superimposed on a first-order hydrogen abstraction process. The activation energy associated with this decomposition reaction is in the region of 47 kcal mole-1, and the major degradation products are cis- and trans-2-ethyl crotonic acid.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1980.170180113
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