摘要:

AbstractThe effect of disulfide rupture, reoxidation, and crosslinking with formaldehyde on decrimping parameters of wool keratin is studied in an attempt to establish the comparative role of cystine‐type of bonding in the decrimping region. Large changes in crimp shape accompanied by changes in decrimping forces and energy suggest that the stability of crimp shape is obviously dependent on cystine linkage

ISSN:0021-8995    

DOI:10.1002/app.1976.070200101

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

年代:1976

数据来源: WILEY

摘要:

AbstractA study of the influence of processing conditions and structure on engineering mechanical properties was conducted in bulk isotactic polypropylene. The influence of one processing parameter, undercooling, defined so as to account for both pressure and temperature effects, was particularly studied.Improved mechanical properties were found with increased undercooling. At low undercoolings, brittle failure without yield occurred, presumably the result of a sparsity of intercrystalline links under these conditions. As undercooling was increased, failure occurred after yielding as failure stress elevated dramatically, apparently because of greater link density. A modest improvement in yield stress with increased undercooling was attributed to the increasingly crosshatched lamellar structure produced at higher undercoolings, a structural trend confirmed by electron microscopy.Spherulite size, varied by altering melt history (melt temperature and time at melt temperature) at constant undercooling, was found to have no effect on engineering yield stress. This result indicates that apparent yield stress–spherulite size effects found by several earlier investigators were probably caused by structural variations other than spherulite siz

ISSN:0021-8995    

DOI:10.1002/app.1976.070200102

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

年代:1976

数据来源: WILEY

摘要:

AbstractA method has been suggested for calculating the first difference of normal stresses characterizing the flow of polymers at high shear stresses. The calculations are based on the results of rheooptical measurements in a slit of rectangular cross section. It has been found, for several samples of high molecular weight polybutadienes and polyisoprenes, that the flow behavior of the representatives of the given polymer homologous series having different molecular weights is characterized by a general relationship between the first normal stress differences and the shear stresses in those cases where the polymers are characterized by narrow molecular weight distributions. It has also been established that the first normal stress difference sharply increases in the region of shear stresses which immediately precedes the spurt—a jumpwise increase of the flow rate at a certain critical value of shear stress; while for polymers of wide molecular weight distribution the increase of the normal stress difference in the region of high values of shear stresses is retarded. Equilibrium swell of the extrudate has been measured and the first normal stress difference determined by the rheo‐optical method has been found to agree satisfactorily with the values calculated from the swelling ratios according to theoretical mod

ISSN:0021-8995    

DOI:10.1002/app.1976.070200103

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

年代:1976

数据来源: WILEY

摘要:

AbstractComparison of the various solubility parameters of different plasticizing agents has shown that their plasticizing action on Acrilan filaments is governed by polar interactions. The diameter swelling of the filaments appears to decrease with increasing efficiency of the plasticizing agent. The diffusion of a disperse day through the plasticized fiber is not related to the fiber swelling and is controlled by the plasticizing action of the dyebath.

ISSN:0021-8995    

DOI:10.1002/app.1976.070200104

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

年代:1976

数据来源: WILEY

摘要:

AbstractSome characteristics of alkoxylated catalysts derived from VOCl3and trialkylaluminum compounds have been examined for ethylene polymerization. Specifically studied were catalysts resulting from reaction of VOCl3with either an alcohol or an alkylaluminum alkoxide, or both, prior to reduction with a trialkylaluminum compound (R3Al). Although the two methods of preparing alkoxylated catalysts did not give identical results, certain overall generalizations can be drawn. In general, as the alkoxide content was increased, the molecular weight distribution was narrowed (by a simultaneous increase inM̄nand decrease inM̄w), polymerization rate was decreased, and the polymer melt index increased at a constant hydrogen level. Alkoxides had a negative effect on rate which could largely be overcome by raising the R3Al/V ratio or using continuous addition of R3Al. By suitably adjusting the alkoxide and hydrogen amounts, the complete range of molecular weights and molecular weight distribution of current commercial HDPE products can be mad

ISSN:0021-8995    

DOI:10.1002/app.1976.070200105

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

年代:1976

数据来源: WILEY

摘要:

AbstractConsiderable deviations of molar refraction from the additivity in the solutions containing polycarbonate and its antiplasticizers symmetrical trinitrotoluene and 1,1‐bis(4‐hydroxy‐3, 5‐dichlorophenyl)2,2,2‐trichloroethane diacetate are reported. In contrast to this, the solutions of polycarbonate with plasticizer di‐n‐butyl phthalate and the solutions of antiplasticizers in pure solvent show only insignificant deviation from the additivity. The calorimetric studies showed the differences in the heats of solution of the used antiplasticizers in pure solvent and in the solvent containing a constant amount of polymer, whereas there was no noticeable difference in the polycarbonate–plasticizer (di‐n‐butyl phthalate) system. Both deviations of the molar refraction from the additivity and differences of the heats of solution prove the existence of strong interactions between the molecules of polycarbonate and

ISSN:0021-8995    

DOI:10.1002/app.1976.070200106

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

年代:1976

数据来源: WILEY

摘要:

AbstractTetramethylthiuram disulfide‐accelerated sulfur vulcanization of natural rubber has been investigated. Continuous measurements in a Vuremo curemeter at 145°C were used to estimate the effects of zinc oxide concentration on the induction periods, on the first‐order rate constants, and on the ultimate extents of crosslinking, on the extents of degradation reaction (reversion), and on the extents of relaxation of vulcanizates at the cure temperature. The concentration of zinc oxide has practically no influence on the rate of thiuram‐accelerated sulfur cure. The values of the ultimate extents of crosslinking increase with increasing the zinc oxide content in the rubber compound up to a certain limit corresponding to the theoretical amount of zinc oxide which is necessary for the formation of zinc dimethyldithiocarbamate from tetramethylthiuram disulfide and zinc oxide during the vulcanization reaction. From the point of view of the reversion, however, this limit value of zinc oxide concentration is not sufficient. The relaxation measurements provide the same results. On the basis of these, for thiuram‐accelerated sulfur vulcanizations, the optimum zinc oxide content in the rubber mix of 2.5 phr has been calculated. This value is in very good agreement with the optimum value of zinc oxide concentration found for both sulfenamides and thiazoles‐accelerated su

ISSN:0021-8995    

DOI:10.1002/app.1976.070200107

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

年代:1976

数据来源: WILEY

摘要:

AbstractTo understand influences of various factors on dynamic durability of engineering plastics, effects of average molecular weights of samples, molding variables, preparing methods of specimens, and fillers on plane and rotational bending, torsional, and impacting fatigue and cavitation erosion and solvent cracking of polycarbonate were studied. From the experimental results, the following tendencies are observed as a whole in case of polycarbonate: The extent of influence of the factors on dynamic durability varies depending on the type of testing. Increase in molecular weight has a favorable effect on dynamic durabilities. Influence of molding conditions is remarkable: especially, deficient drying of resin pellets before molding decreases dynamic durability noticeably, and specimens prepared by injection molding have much better durabilities than those by machaning from extruded sheet. Polyethylene blending has an unfavorable effect on durability, except for Izod‐type impact strength and solvent cracking. Reinforcement by glass fiber has a favorable effect on fatigue under constant deformation and cavitation erosio

ISSN:0021-8995    

DOI:10.1002/app.1976.070200108

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

年代:1976

数据来源: WILEY

摘要:

AbstractPolyethylene glycol (molecular weight 8000) was degraded by ozone in 1% aqueous solution of pH 12. Chemical oxygen demand of the solution decreased with increasing ozone consumed. Intrinsic viscosity of the solution lowered exponentially as a result of the ozonization. The number of breaks calculated from the viscosity indicated that two molecules of ozone were consumed for one cleavage of the polymer chain. The molecular weight distribution obtained by gel permeation chromatography was very broadened and molecular weight was lower as well, and the polymer chain was found to be cleaved randomly by ozone. The production of formic ester, ethylene glycol, diethylene glycol, triethylene glycol, and hydrogen peroxide was confirmed by IR, NMR, gas chromatography, and chemical analysis. These observations could be accounted for by electrophilic attack of ozone on the ether bond.

ISSN:0021-8995    

DOI:10.1002/app.1976.070200109

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

年代:1976

数据来源: WILEY

摘要:

AbstractThe diffusion of binary dye mixtures of markedly different chemical constitutions (4‐nitro‐4′‐aminoazobenzene and 1‐amino‐4‐hydroxyanthraquinone) and of similar ones (1‐amino‐4‐hydroxyanthraquinone and 1,4‐dihydroxyanthraquinone) into nylon 6 film was examined. Apparent diffusion coefficients of dyes in the mixture within a single dyeing were determined by the film roll method at 60°, 70°, 80°, and 90°C. Diffusion coefficients of individual dyes used in a mixture of chemically dissimilar dyes are found to change little in comparison with single dyeings, while diffusion coefficients of dyes of similar structures are decreased appreciably. It is suggested that the latter effect is due to the interaction between two dy

ISSN:0021-8995    

DOI:10.1002/app.1976.070200110

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

年代:1976

数据来源: WILEY