摘要:

AbstractHomopolymers ofm‐N,N‐diethylaminostyrene andp‐N,N‐diethylaminostyrene and their copolymers with styrene have been subjected to thermal analysis studies in air. Molecular weight and copolymer composition have been shown to influence the stability of the polymers and the shape of the TG and DSC curves in the case of polymers containingm‐N,N‐dimethylaminostyrene. Polymers containingp‐N,N‐diethylaminostyrene show TG and DSC curves essentially independent of molecular weight and copolymer composition. The behavior of the two systems is discussed in terms of the antioxidant effect of the chain‐bound N,N‐dialkylamino substituents and their

ISSN:0021-8995    

DOI:10.1002/app.1976.070200401

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1976

数据来源: WILEY

摘要:

AbstractThe kinetics of reactions, namely, hydrolysis, acetylation, and deamination, on polyamide fibers has been studied at different temperatures. Rate constants and apparent activation energies of these reactions were determined. All the three reactions studied show two rates, the initial fast rate, followed by the slow one. The existence of two rates has been explained on the basis of two‐phase structure of the polyamide fibers, the fast rate corresponding to the weakly hydrogen‐bonded regions and the slow rate corresponding to the regions which are strongly hydrogen bonded in the regular fashion. For hydrolysis, the fast rate was 38 times faster than the slow one, while the fast rate of acetylation reaction was about 162 times that of the slow rate. The ratio between the fast and slow rates was constant at all the temperatures studied in case of the hydrolysis and acetylation reactions. This ratio, however, was found to be extremely temperature sensitive for the deamination reaction. The hydrolysis and acetylation reactions were found to be strongly temperature dependent leading to the increase in the extent of modification with increase in temperature. Deamination, on the other hand, showed negative temperature dependence giving progressive decrease in the modification with increase in temperature. All the three modifications studied observed first‐order kinetics. The apparent activation energy for hydrolysis was 1.38 and 1.05 kcal/mole corresponding to the fast and slow rates, respectively. The apparent activation energy values for acetylation were 2.53 and 3.29 kcal/mole, while those for deamination reaction were −8.28 and −46.0 kcal/mole, respectively. The apparent activation energy values for the deamination reaction bore negative signs possibly because of the negative temperature dependence of this reaction. The apparent activation energy for slow reactions in case of acetylation and deamination was found to be higher than that of the fast rate, while the reverse was true in case of hydrolysis, showing that the acetylation and deamination reactions, being the chemical modification of polyamide fibers at the NH2groups, proceed by altogether different mechanisms than the hydrolytic breakdown of the polyam

ISSN:0021-8995    

DOI:10.1002/app.1976.070200402

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1976

数据来源: WILEY

摘要:

AbstractThe two simplest models that can be put forward to account for the elasticity of composite materials are the Reuss model and the Voigt model in which the constituents undergo, respectively, the same stress or the same strain. Experimental measurements always fall between the values predicted by these models. We propose correcting the Reuss model by stating\documentclass{article}\pagestyle{empty}\begin{document}$ \sigma _f = K\sigma _m $\end{document}σfand ϵmbeing the average stresses undergone, respectively, by reinforcing agent and the matrix. Similarly, we shall modify the Voigt model by supposing\documentclass{article}\pagestyle{empty}\begin{document}$ \epsilon _f = L\epsilon _f $\end{document}σfand ϵmbeing the average strain undergone, respectively, by reinforcing agent and the matrix.KandLare interrelated tensors which depend on the nature of the reinforcing agent, on its possible orientation, and on the mechanical behavior of the interface and also on the moduli of the constituents. We have developed the equations for determining the tensors with regard to fiber composite, taking into account the characteristics of the fibers (length, diameter, orientation, interface). The evaluation ofKandLenables us, therefore, to calculate the modulus or the compliance. Conversly, by measuring the modules or the complience, one can determineKorLand , in this way, obtain data on the machnism of load transfer from the matrix to the reingforcing agent and thus on the behavior of their interface. The theoretical values of the Young modules calculated from our model are in good agreement with the experemental values obtained by Le

ISSN:0021-8995    

DOI:10.1002/app.1976.070200403

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1976

数据来源: WILEY

摘要:

AbstractA class of amine‐cured epoxy resins containing various amounts of polysulfide plasticizer were subjected to dynamic testing during curing at high temperature. BothEmodulus and loss factor were determined simultaneously. It was proved that the method allowed for rapid determination of the general pattern of the crosslinking procedure and the necessary curing time and, in general, that dynamic methods are most suitable for the mechanical characterization of polymers under curing at each stage of the curing cycl

ISSN:0021-8995    

DOI:10.1002/app.1976.070200404

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1976

数据来源: WILEY

摘要:

AbstractThree classes of active halogen compounds were effective in promoting photodegradation of polystyrene, polypropylene, and polyethylene. The classes are arylmethyl halides, phenyl halomethyl ketones, and haloalkenes. The additives were blended with the polymers and fabricated into films which were irradiated 66–200 hr with a 275‐watt RS sunlamp. Photo‐oxidation, as determined by IR spectroscopy, was used as a measure of photodegradation. The relationship between the structure of the additive and its effectiveness as a photoinitiator within each of the three classes of compounds is discussed. In general, photoactivated polystyrene was degraded the most, followed by polypropylene and then polyethylene. Viscosity measurements on irradiated polystyrene containing the additives showed significantly greater molecular weight loss than a polystyrene co

ISSN:0021-8995    

DOI:10.1002/app.1976.070200405

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1976

数据来源: WILEY

摘要:

AbstractPolystyrene (PS), polypropylene (PP), and polyethylene (PE) films, blended with additives to enhance photodegradability, were irradiated with UV light and sunlight. In almost every case, photodegradation was greater with outdoor exposure than under laboratory conditions. Explanations for the differences in degradation obtained by the two methods of irradiation are discussed. Based on IR measurements and molecular weight determinations, photo‐oxidative changes that occur in PS induced by UV light appear similar to those induced by sunlight. In addition to the additives previously reported, several new classes of photoinitiators were evaluated. These include selected halocarbonyl compounds, haloalkyl sulfur compounds, and halogen compounds containing certain electron‐withdrawing groups. The performance of the additives in vinyl polymer blends is discus

ISSN:0021-8995    

DOI:10.1002/app.1976.070200406

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1976

数据来源: WILEY

摘要:

AbstractAn instrumental system consisting of a combination in series of a programmable pyrolyzer, a thermal conductivity detector, a mass chromatograph, and a fast‐scan vapor‐phase infrared spectrophotometer is descri

ISSN:0021-8995    

DOI:10.1002/app.1976.070200407

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1976

数据来源: WILEY

摘要:

AbstractThe proton magnetic resonance spectra at frequencies of 60, 100, and 220 MHz of two bisphenol A–neopentyl glycol–terephthalate copolyesters having the same overall composition but different sequence distributions are correlated. Analysis of the terephthalate proton resonances indicates the usual singlets for the two symmetrical diester sequences. However, the dissimilar protons in the unsymmetrical diester give rise to an apparent quartet originating from an incompletely resolved AA′BB′ spectrum. The apparent quartet coupling constant is accurately determined to be 8.03 Hz by a 220 MHz separation of the appropriate peaks and is found to be approximately 8.3 Hz by employing a shift reagent [Pr(fod)3] in conjunction with suitable model compounds at 100 MHz. This permits an approximate calculation of the entire quartet intensity in those cases where the outside resonances of the latter and the singlets are superimposed, resulting in a more accurate calculation of sequence distribution. In particular, a copolyester prepared by a normal two‐stage, interfacial polycondensation yields a degree of randomnessBestimated to be slightly greater than 1, indicating a nearly random distribution of the comonomers. A second copolyester, prepared so as to enhance an alternating comonomer sequence, exhibits aBvalue of a

ISSN:0021-8995    

DOI:10.1002/app.1976.070200408

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1976

数据来源: WILEY

摘要:

AbstractThe determination of the copolymer composition as a function of molecular weight by preparative gel permeation chromatography (GPC) for a poly(styrene‐co‐vinyl stearate) sample is described. These results were compared to data obtained on the same copolymer by the previously described rapid stop‐and‐go GPC/IR method of analysis of copolymer composition as a function of molecular weight and found to be in good ag

ISSN:0021-8995    

DOI:10.1002/app.1976.070200409

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1976

数据来源: WILEY

摘要:

AbstractIn order to extend the application of grafting for the modification of natural polymers, the graft polymerization of methyl methacrylate onto gelatin by radical initiators was studied in aqueous solution at temperatures between 60°C and 80°C. Among the initiators used (peroxy‐sulfates, α,α′‐azobisisobutylonitrile, and benzoyl peroxide), potassium peroxysulfate was found to be the most efficient initiator in this particular graft polymerization. From the kinetic data with this initiator, it was shown that (1) efficiency of grafting is higher at lower temperature; (2) a sharp increase in the efficiency of grafting occurs at the later period of the polymerization at high temperature, which is attributable to the combination between homopolymer and backbone gelatin; and (3) generally, the number of branches was small and the molecular weight of the branch polymer was high in this polym

ISSN:0021-8995    

DOI:10.1002/app.1976.070200410

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1976

数据来源: WILEY