摘要:

AbstractPoly(vinylchloride) (PVC) was mixed with various poly(methacrylate)s, poly(carbonate)s and polymers containing nitrile groups (poly(acrylonitrile), poly(styrene‐co‐acrylonitrile), nitrile rubber, hydrogenated nitrile rubber) and/or C  C double bonds (nitrile rubber, high‐impact poly(styrene)). The thermal stability was measured at 180°C in nitrogen, and the evolved HCl was detected by conductometry.It is shown that the nature of the ester group and the content of nitrile groups and C ‐ C double bonds are the dominating factors for the thermal stability of poly(vinylchloride) in these blends. An influence of the miscibility of PVC with the various blend components on the thermal stability can not be clearly detected.Differential scanning calorimetry (DSC) was used as a powerful method to study the stabilizer distribution of heterogeneous PVC/poly(styrene‐co‐acrylonitrile) and PVC/poly(methylacrylate) blends. It is shown that the stabilizer can be solubilized either in the PVC phase (PVC/poly(methylacrylate)) or in both phases of the blends PVC/poly(styrene‐co

ISSN:0003-3146    

DOI:10.1002/apmc.1994.052160101

出版商:Hüthig&Wepf Verlag    

年代:1994

数据来源: WILEY

摘要:

AbstractAfter a general introduction including definition of biodegradability, the recent literature is briefly summarized. The results obtained in our laboratory for various polymers in three different composting units are then presented. They demonstrate that there is an urgent need for a quantitative method to characterize polymer biodegradation. For that purpose, a manometric method which allows the measurement of the oxygen consumed by the growing microorganisms has been developed. It has been tested with various inocula of increasing complexity: oneStreptomycessp., a mixture of threeStreptomyces(badius, setoniiandviridosporus), a compost extract or sewer sludge, growing in the presence of low molecular weight molecules as sole carbon source. Its performances and limitations are discussed. It is then applied to various polymer systems: polyesters and their constituent units, autoxidized polyethylene (APE) and its model compounds, polyvinyl alcohol (PVAl), starch and cellulose. The biodegradability of these polymers is characterized and their potential use as biodegradable materials for packaging, sanitary and agricultural uses is discussed.

ISSN:0003-3146    

DOI:10.1002/apmc.1994.052160102

出版商:Hüthig&Wepf Verlag    

年代:1994

数据来源: WILEY

摘要:

AbstractThe UV‐degradation of an unstabilized and two HALS stabilized polyethylene (PE) films is described. The degradations are characterized by measuring the oxygen uptake, the formation of CO and CO2, the FT‐IR spectra, the mechanical properties, the stabilizer concentration and the oxygen content of the film.The oxygen uptake of the unstabilized PE film led to the expected changes in the IR spectra and embrittlement of the film, while the oxygen uptake by the HALS stabilized films caused only minor changes. The differences between the results for the unstabilized and the HALS stabilized polymers are explained assuming that the initiation of the photodegradation of PE is due to charge transfer comple

ISSN:0003-3146    

DOI:10.1002/apmc.1994.052160103

出版商:Hüthig&Wepf Verlag    

年代:1994

数据来源: WILEY

摘要:

AbstractPolymer blends can undergo, during processing, degradation phenomena because of the presence of both temperature and mechanical stresses. With respect to pure homogeneous polymers, the degradation of polymer blends shows distinct features because of the possible interaction between the different chemical species. These interaction can give rise to both a faster degradation or to the formation of copolymers which act as stabilizing agents. This latter phenomena is particularly important in the processing of condensation polymers

ISSN:0003-3146    

DOI:10.1002/apmc.1994.052160104

出版商:Hüthig&Wepf Verlag    

年代:1994

数据来源: WILEY

摘要:

AbstractThe low molecular weight by‐product of a high‐density polyethylene plant (slurry process in hexane, Ti‐based highly active catalysts) was subjected to controlled oxidation by air bubbling into the polymer melt maintained under stirring at constant temperature (130–170°C). Oxidized polyethylene waxes having various oxidation degree, i.e. acid number up to 60 mg.KOH/g and saponification number up to 120 mg.KOH/g have been obtained under different reaction conditions. Oxidation temperature and polymer/air ratio proved to be the main parameters that control the process. Inhibition and catalytic effects have been also studied as well as the dependence of the oxidation process on the like of the starting low molecular weight polyethylene. the results have been used to develop an industrial process for producing oxidized polyethylene waxes with useful properties and appl

ISSN:0003-3146    

DOI:10.1002/apmc.1994.052160105

出版商:Hüthig&Wepf Verlag    

年代:1994

数据来源: WILEY

摘要:

AbstractOutdoor weathering at three locations in Japan has been carried out for new engineering plastics; PPO, PPS, PA and PEI. The degradation results were compared with those exposed in the Sunshine and Xenon Weather simulation machines. The half‐time of these materials, which was the time to give a 50% decrease of some property, strongly depended on a property to be noted. The elongation to break and impact energy, i.e. fracture energy, reflected the degradation process of neat polymers and they were closely related to the condition of a very thing degraded layer. The half‐amount of ultraviolet radiation also depended both on a property and material. The acceleration rate of the weather simulating machines has been obtained by this half‐amount. The loss in mechanical properties of fiber‐filled materials is much smaller than that of neat polymers. The fibers could reduce the embrittlement of the degraded layer. It has been demonstrated that a micro‐cutting technique to measure cutting resistance is a useful method to monitor a continous change in mechanical properties from the surface to the interior of the degraded layer. The effect of stabilizer has been clearly shown by this

ISSN:0003-3146    

DOI:10.1002/apmc.1994.052160106

出版商:Hüthig&Wepf Verlag    

年代:1994

数据来源: WILEY

摘要:

AbstractThe photo and thermal reactivity of nitroxyl radicals derived from di‐, (oligo)meric hindered amine light stabilizers (HALS) on iso‐octane, a model compound for polyprophylene, was studied and compared to that of monomeric 2,2,6,6‐tetramethyl‐ piperi‐dine‐N‐oxyl (TEMPO).The exchange‐interaction among>NO. groups seems to affect only th

ISSN:0003-3146    

DOI:10.1002/apmc.1994.052160107

出版商:Hüthig&Wepf Verlag    

年代:1994

数据来源: WILEY

摘要:

AbstractThe kinetics of the natural and accelerated photo‐oxidation of low‐denisty polyethylene (LDPE) films have been studied; different geographical locations have been selected for the natural tests, and a range of temperatures used in the accelerated experiments in a specially built temperature‐controlled ultraviolet radiation enclosure. A meaningful correlation between natural and accelerated weathering results was established, by means of an adequate superposition of the effects of UV radiation exposure and temperature. Reasonably detailed and accurate, lumped‐parameter, kinetic models of the photo‐oxidation process have also been developed, to interpret and predict the results of measurements of carbonyl, hydroperoxide and vinyl absorbances as functions of time and temperature; the models predict the general experimental behaviour, and also that both the formation of hydroperoxides and carbonyl Norrish‐I reactions are important initiation steps. More complex models have the potential of interpreting other fine details of the degradation behaviour, namely the generation of other chemical species, and the chain scission and cross‐linking process which are directly related to changes in the mechanic

ISSN:0003-3146    

DOI:10.1002/apmc.1994.052160108

出版商:Hüthig&Wepf Verlag    

年代:1994

数据来源: WILEY

摘要:

AbstractPrincipal chemical pathways characteristic of active participation of radical scavenging polymer stabilizers (phenols, aromatic, hydroaromatic and hindered aliphatic amines) are outlined. Pathways resulting in a partial depletion or distortion of activity of stabilizers, in formation of polymer discolouring products, or in interactions in bifunctional stabilizers are involved.

ISSN:0003-3146    

DOI:10.1002/apmc.1994.052160109

出版商:Hüthig&Wepf Verlag    

年代:1994

数据来源: WILEY

摘要:

AbstractThe photochemical behaviour of Bisphenol‐A polycarbonate (PC) under various types of monochromatic and polychromatic radiations is reported. The PC dual photochemistry observed in the solid state is characterized using both UV and FTIR spectroscopy. At short wavelength, the intrinsic photochemistry, which is associated with the direct photo‐excitation of PC chromophore groups, accounts for the formation of phenylsalicylate, dihydroxybenzophenone, hydroxybiphenyl and hydroxydiphenyl ether groups. The extrinsic photochemistry of PC, related to the excitation of chromophoric defects, is easily observed at long wavelength. This photoinduced oxidation leads to the formation of tertiary hydroperoxides which decompose into alcohols and ketones. The two photochemistries kinetically overlap but their stoichiometry remains independent. PC films can be used therefore to check the relative importance of short and long wavelength radiations emitted by the various sources used in the field of polymer degradat

ISSN:0003-3146    

DOI:10.1002/apmc.1994.052160110

出版商:Hüthig&Wepf Verlag    

年代:1994

数据来源: WILEY