摘要:

AbstractSix oligoethylene glycols were crosslinked with triphenylmethane triisocyanate, and polymers with systematically changing network chain lengths were obtained and investigated. The 10‐sec. torsion moduli versus temperature, glass transition temperatures, and cohesive energy densities of the polymers were determined and studied. The 10‐sec. torsion modulus versus temperature plots show that all six polymers have a glassy transition and rubbery region of rheological behavior. The front factor calculated from the equation for the torsion modulus in the rubbery region when measured values of the modulus were used was compared with the front factor computed from equations that take into consideration molecular structures of the rubbery networks. With the exception of the case of crosslinked diethylene glycol the agreement in all the other cases between the values obtained for the front factor in both ways was good. In the investigated range of temperatures the polymers have below the glass transition temperature another transition point. The solubility parameters of the polymers, calculated from swelling experiments, were with the exception of the first member in the series almost identi

ISSN:0449-2978    

DOI:10.1002/pol.1968.160060501

出版商:John Wiley&Sons, Inc.    

年代:1968

数据来源: WILEY

摘要:

AbstractThe phase equilibria in polymer–liquid 1–liquid 2 ternary systems have been calculated on the basis of the Flory‐Huggins theory of polymer solutions. A new approximation method based on the “cluster” concept has been introduced for mixed solvents comprising a solvent and a nonsolvent. This concept has been verified with polystyrene–solvent–met

ISSN:0449-2978    

DOI:10.1002/pol.1968.160060502

出版商:John Wiley&Sons, Inc.    

年代:1968

数据来源: WILEY

摘要:

AbstractExtended chain crystals of polyoxymethylene were irradiated with x‐rays of about 105r./min. An immediate decrease in superheating on melting was noted. After 90 min. of irradiation the melting point level, refractive indices, and density also decreased. After 480 min. the DTA melting peak at a heating rate of 20°C./min. had decreased 25°C., the melting point decreased about 18°C., and the density calculated from refractive indices decreased 0.031 g./cm.−3. These effects are interpreted as indication of chain scission and formation of amorphous d

ISSN:0449-2978    

DOI:10.1002/pol.1968.160060503

出版商:John Wiley&Sons, Inc.    

年代:1968

数据来源: WILEY

摘要:

AbstractHighly crystalline polycaprolactam was prepared by zone polymerization of ε‐caprolactam. Folded‐chain crystallized and annealed, melt‐crystallized, and solution‐crystallized polycaprolactam was produced from commercial polycaprolactam. All samples were characterized by x‐ray diffraction, electron microscopy, density measurement, and heat of fusion measurement. The determination of the time‐dependent melting by DTA and scanning calorimetry revealed that all the different morphologies show different melting behavior. Zone‐polymerized polycaprolactam superheats, and the other morphologies reorganize on heating to different degrees. Densities and heat of fusion vary in the same manner—from highest to lowest—in the order: zone‐polymerized, solution‐crystallized, annealed, and melt‐crystallized. An estimate of heat of fusion, equilibrium melting point, and surface free energy was obtained

ISSN:0449-2978    

DOI:10.1002/pol.1968.160060504

出版商:John Wiley&Sons, Inc.    

年代:1968

数据来源: WILEY

摘要:

AbstractPrecise heat capacity values are reported over the temperature range from 10 to 360°K. for a sample of atactic polystyrene having a narrow molecular weight distribution. This sample was taken from the stock from which National Bureau of Standards Standard Sample 705, Narrow Molecular Weight Distribution Polystyrene, was established. Data are reported for the sample as received, and after an annealing procedure. At temperatures below about 60°K. a systematic difference comparable with the limits of experimental precision appears between the values obtained for the present sample as received and after the annealing, although at higher temperatures the values for the two conditions showed no systematic difference beyond the limits of precision of the measurements. At temperatures above 100°K., previously published values for atactic polystyrene samples of various molecular weight distributions and for isotactic polystyrene agree within about 0.5% of the values from this investigation. At temperatures below 100°K. significant heat capacity differences appear, especially between values for the atactic and the isotactic isomers, and even between atactic samples of different molecular weight distribut

ISSN:0449-2978    

DOI:10.1002/pol.1968.160060505

出版商:John Wiley&Sons, Inc.    

年代:1968

数据来源: WILEY

摘要:

AbstractTwo crystalline forms (α and β) of poly(vinylidene fluoride) were studied by infrared spectroscopy. The spectral differences permitted the study of the transformation and the ratio of the two forms. The ordinary\documentclass{article}\pagestyle{empty}\begin{document}$ \vec G,\vec F $\end{document}matrix method was used to calculate the fundamental mode with a Urey‐Bradley type potential field, and a preferred set of the force constants was obtai

ISSN:0449-2978    

DOI:10.1002/pol.1968.160060506

出版商:John Wiley&Sons, Inc.    

年代:1968

数据来源: WILEY

摘要:

AbstractThe following measurements were carried out on the melts of two samples of polypropylene, one with a narrow and one with a broad molecular weight distribution: viscosity in steady shear flow, dynamic storage and loss moduli, total normal thrust in cone‐and‐plate apparatus, and flow birefringence. The validity of various theoretical interrelations between the measured quantities is checked. The influence of molecular weight distribution is qualitatively discus

ISSN:0449-2978    

DOI:10.1002/pol.1968.160060507

出版商:John Wiley&Sons, Inc.    

年代:1968

数据来源: WILEY

摘要:

AbstractAs an extension of earlier work on the crystallization kinetics of isotactic polystyrene, the spherulite growth rate in mixtures of isotactic polystyrene and benzophenone has been measured over a concentration range extending from pure polymer to a mixture containing about 30% benzophenone. The glass transition temperature has been measured over the entire range from pure polymer to pure benzophenone. For the mixtures the dependence of the growth rate on temperature is similar to that of the undiluted polymer. The addition of benzophenone causes a shift of the crystallization range to lower temperatures. For mixtures containing up to about 20% benzophenone, the maximum in the growth rate increases with increasing content of benzophenone. On addition of more benzophenone, the maximum rate is depressed. Taking into account the glass transition temperature of the mixtures, the influence of benzophenone on the melting point of isotactic polystyrene, and the volume fraction of polymer, we can describe the influence of benzophenone on the growth rate in a semiquantitative way.

ISSN:0449-2978    

DOI:10.1002/pol.1968.160060508

出版商:John Wiley&Sons, Inc.    

年代:1968

数据来源: WILEY

摘要:

AbstractThe incorporation of comonomers bearing functional groups yields butadiene copolymers capable of hydrogen bonding. Three such butadiene‐based materials were studied: methacrylic acid copolymers, 2‐methyl‐5‐vinylpyridine copolymers, and stoichiometric mixtures of the acidic and basic copolymers. The elastic effects of intermolecular hydrogen bonding were determined by comparing the simple weighted average of the moduli of the parent copolymers with the observed modulus of their stoichiometric mixture. The results show that measurable increases in the moduli of the mixtures persist even above the glass temperatureTg, which is itself elevated in the mixtures. These increases may be treated as temperature‐dependent temporary c

ISSN:0449-2978    

DOI:10.1002/pol.1968.160060509

出版商:John Wiley&Sons, Inc.    

年代:1968

数据来源: WILEY

摘要:

AbstractThe mechanical lability of intermolecular hydrogen bonds in stoichiometric mixtures of acidic and basic butadiene copolymers has been studied by both infrared and mechanical methods. Comparison is made between the weight‐averagedE(t) andH(τ) spectra of the parent copolymers and those of the mixed copolymers. The results indicate that the maximum contributions of bond‐interchange relaxation migrate to shorter times as the concentration of bonding groups incre

ISSN:0449-2978    

DOI:10.1002/pol.1968.160060510

出版商:John Wiley&Sons, Inc.    

年代:1968

数据来源: WILEY