摘要:

AbstractA dynamic TGA method was used to study the effect of the molecular weight of well‐defined polystyrene samples as well as the effect of heating rate and sample weight on the kinetic parameters of the thermal decomposition. It is shown that the maximum rate, the average specific rate, and the activation energy of the decomposition increase up to molecular weights of about 360,000 and then level off. The activation energy for the first part of the decomposition was 33 ± 5 kcal/mole and 50 ± 5 kcal/mole for the second part. An activation energy of 42 ± 5 kcal/mole was determined for the overall decomposition of polysty

ISSN:0021-8995    

DOI:10.1002/app.1973.070170101

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

年代:1973

数据来源: WILEY

摘要:

AbstractMass‐spectrometric techniques were applied to elucidate the mechanism by which polymers release condensation nuclei during pyrolysi

ISSN:0021-8995    

DOI:10.1002/app.1973.070170102

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

年代:1973

数据来源: WILEY

摘要:

AbstractEpoxy resins cured with diethylenetriamine (37%–103% of stoichiometric composition) were heat treated at 120°C, and the dynamic elastic modulus and internal friction of the specimens were measured over the range of 85°–300°K. Results indicate that heat treatment causes the dynamic modulus to decrease at 85°K and at room temperature, but to increase over the region 150°–200°K. The γ‐ (∼150°K) and β‐(∼250°K) peaks merge into a single broad peak with heat treatment, and a β′‐peak is observed in the heat‐treated samples. Effects of heat treatment also depend upon the amou

ISSN:0021-8995    

DOI:10.1002/app.1973.070170103

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

年代:1973

数据来源: WILEY

摘要:

AbstractThe representation and interpretation of dynamic mechanical properties of heterogeneous polymer–polymer composites are discussed in terms of equivalent mechanical models and the viscoelastic form of the well‐known Kerner equation. Model parameters calculated from dispersed phase volume fraction and matrix Poisson's ratio (using the Kerner equation) are in fairly good agreement with experimental values for systems comprising soft inclusions in a hard matrix. The effects of partial phase inversion on dynamic properties are discussed in terms of an extension of the Kerner equation. Model calculations indicate that the in‐phase component of the complex modulus depends primarily on dispersed phase volume concentration, while the out‐of‐phase component depends on both the concentration and the morphology of the dispersed phase. Although substantial information about the microstructure of polymer–polymer composites can in principle be deduced from dynamic measurements, quantitative correlation between dynamic properties and use properties such as impact strength (which may have a quite different dependence on structural parameters) is probably

ISSN:0021-8995    

DOI:10.1002/app.1973.070170104

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

年代:1973

数据来源: WILEY

摘要:

AbstractA two‐stage emulsion polymerization procedure has been developed and used to prepare relatively uniform populations of heterogeneous acrylic latex particles (HLP). One class of particles (HLP1) can be described as composite materials comprising a glassy continuous phase and a rubbery discrete phase. Another class (HLP2) can be described (at high rubber content) as composite materials comprising a rubbery continuous phase and a glassy discrete phase. The phase structure of the HLP1 is sufficiently stable to allow fabrication of composites having a uniform spatial distribution of inclusions by direct compression molding. Although the observed particle structure of the HLP2 does not depend markedly on crosslinking, the phase structure and mechanical properties of compression moldings do. Crosslinking of the glassy stage appears to stabilize HLP2 phase structure during molding, while crosslinking of the rubbery stage favors phase inversion. The observed HLP2 particle structures and the morphology of molded HLP1 specimens are consistent with a shell‐core model. It is found that the modulus and thermal expansion coefficient of many of these materials can be adequately described in terms of a simple theoretical model for the elastic and thermoelastic properties of particulate composites, provided that an interaction parameter interpreted as a maximum packing fraction is introdu

ISSN:0021-8995    

DOI:10.1002/app.1973.070170105

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

年代:1973

数据来源: WILEY

摘要:

AbstractThe physical properties of heterogeneous polymer–polymer composites such as rubber‐modified plastics depend not only on the properties of the constituent polymers, but also on structural characteristics such as phase geometry and morphology. The dependence of the viscoelastic properties of particulate composites on phase morphology and composition has been treated in a previous paper. This analysis is further modified and applied to dynamic Young's modulus (E*) data on several types of heterogeneous acrylic polyblends prepared in this laboratory. By taking into account interparticle interactions, copolymerization effects, and phase inversion, a nearly quantitative representation ofE*is obtained. Deviations from calculated behavior can be explained by assuming more complicated models of phase structure and composition and by postulating higher‐order and temperature‐dependent interaction

ISSN:0021-8995    

DOI:10.1002/app.1973.070170106

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

年代:1973

数据来源: WILEY

摘要:

AbstractMeasurements were taken of the viscoelastic properties of six polymer melts by mean of the Weissenberg rheogoniometer and the Han slit/capillary rheometer. Polymers in vestigated were three high‐density polyethylenes of different polydispersity, a low‐density polyethylene, a polypropylene, and a polystyrene. The range of shear rates tested was from about 5.0 × 10−3to 10 sec−1with the Weissenberg rheogoniometer, from about 10 to 102sec−1with the slit rheometer, and from about 102and 103with the capillary rheometer: the temperature of measurement was 200°C. The three different apparatuses give consistent results over almost six decades of shear rates, yielding satisfactory correlations of shear viscosity to shear rate and of normal stress difference to

ISSN:0021-8995    

DOI:10.1002/app.1973.070170107

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

年代:1973

数据来源: WILEY

摘要:

AbstractThe 2,4‐dinitrophenylhydrazones formed on irradiated polystyrene films were regenerated to carbonyl groups by immersing the films in levulinic acid solutions. The changes in the amount of carbonyl groups regenerated from the hydrazones were inferred by comparing the absorptions of the hydrazones at 378 mμ. The carbonyl groups were regenerated from the hydrazones with increase in regeneration times in the early stages of the regenerations and gradualy regenerated with increase in the regeneration times thereafter. The regeneration of the carbonyl groups was facilitated by raising the temperature in the levulinic acid solution, by adding dilute hydrochloric acid to the levulinic acid, or by raising the temperature in the levulinic acid solution containing hydrochloric acid. When the polystyrene films were irradiated for different periods of time, the increase in the critical surface tension of the films with increase in irradiation time showed a trend similar to the increase of amount of hydrazones formed on the surface zones with increase in irradiation ti

ISSN:0021-8995    

DOI:10.1002/app.1973.070170108

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

年代:1973

数据来源: WILEY

摘要:

AbstractThe molecular weight distribution has been derived for a homopolymer polymerized in a continuous‐feed reactor under homogeneous conditions. The derived equations are then compared with data obtained on polymers of acrylonitrile–co(vinyl acetate) prepared under heterogeneous conditions with the potassium peroxydisulfate–sodium bisulfite–iron redox system. The termination reaction is assumed to be effected completely by recombination of active radicals with no disproportionation. The only transfer reaction considered is the transfer‐to‐activator reaction\documentclass{article}\pagestyle{empty}\begin{document}$ R_n ^* + {\rm HSO}_{\rm 3} ^ - \to {\rm P}_n {\rm H} + {\rm SO}_3 ^{ - *} $\end{document}The transfer and termination reactions produce polymers with different acid groups as endgroups. Each molecule, on the average, contains one sulfonate group, whereas the concentration of sulfate groups depends upon the extent of the transfer‐to‐activator reaction. The basic dye acceptance of the polymer depends on the number of acid groups in the polymer and hence on the activator and catalyst concentrations. Analysis of the basic dye acceptance and conversion data at a variety of catalyst and activator concentrations yields the following parameters at 50°C:kp/k t1/2= 1.01 (1./mole sec)1/2,ktr/kp= 0.2063, andk1[see eq. (1)] = 50.7 l./mole sec. Owing to the heterogeneous nature of the polymerization, the weight‐average molecular weight of the polymer depends only on the activator concentration and the conversion and not directly on the catalyst concen

ISSN:0021-8995    

DOI:10.1002/app.1973.070170109

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

年代:1973

数据来源: WILEY

摘要:

AbstractThe results of studies on the oxidative degradation of poly(vinyl chloride) in a solvent, triphenyl phosphate, are described and compared with results previously reported for the oxidative degradation of bulk polymer samples. A range of chain‐breaking and peroxide‐decomposing antioxidants of the type commonly used to stabilize polyolefins were not effective in reducing the rate of dehydrochlorination of poly(vinyl chlori

ISSN:0021-8995    

DOI:10.1002/app.1973.070170110

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

年代:1973

数据来源: WILEY