摘要:

AbstractCharacterization measurements of a commercial phenol‐formaldehyde resin prepared from constituents including phenol and formaldehyde in the molar ratio 1:1.33 are reported. The measurements consist of (1) the linear thermal expansion coefficient between approximately 85 and 270°K; (2) the specific heat capacity between approximately 6 and 100°K; (3) the Young's modulus at room temperature. A critical examination of the data reveals that: (1) the vibrational behavior is predominantly that of a three‐dimensional assembly; (2) as far as data available from other sources permit an assessment to be made, the principle of additivity appears to be applicable to the specific heat capacity between approximately 50 and 100°K; and (3) the data lie near the limit of an empirical relationship observed between the Young's modulus and linear thermal expansion coefficient of other po

ISSN:0098-1273    

DOI:10.1002/pol.1978.180160501

出版商:John Wiley&Sons, Inc.    

年代:1978

数据来源: WILEY

摘要:

AbstractThe crystal structure of p‐phenylenediacrylic acid diethyl ester above the transition point was determined at 70°C by x‐ray diffraction. No significant differences in molecular arrangement are found between the structures of the α2form (above the transition point) and the α1form (at room temperature). Since the α1form is photopolymerized, it is concluded that selective dimerization in the α2form results not form the crystal structure of the monomer, but from the deterioration of molecular arrangement by the formation

ISSN:0098-1273    

DOI:10.1002/pol.1978.180160502

出版商:John Wiley&Sons, Inc.    

年代:1978

数据来源: WILEY

摘要:

AbstractThe morphology of surfaces produced during peel experiments was studied to increase the understanding of peel phenomena. Thin films of polystyrenes of narrow molecular‐weight distribution and a polydisperse polyester on flexible supports were peeled from rigid substrates at temperatures above their glass transitions with equipment that also permitted quenching and preservation of the peeled surfaces which then could be studied by scanning electron microscopy. The results show many types of cavitation including foams and the coalescence of cavities to form fibers. Cavitation occurred throughout and beyond the region of transition from cohesive to interfacial failure where peel force decreased abruptly; however, cavity growth was abruptly restricted as the failure mode changed. The master curves and shift factors obtained in this work provided strong evidence that the quenching used to preserve the peeled surfaces did not introduce large perturbations in the results. The reason was that failure occurred at or close to the heated substrat

ISSN:0098-1273    

DOI:10.1002/pol.1978.180160503

出版商:John Wiley&Sons, Inc.    

年代:1978

数据来源: WILEY

摘要:

AbstractDiffusion of α and β cyclodextrin (α‐CD and β‐CD, respectively) has been studied in aqueous solutions of poly(methacrylic acid), sodium poly(styrene sulfonate), having three different degrees of sulfonation (DS), and copoly(styrene‐methacrylic acid) containing three different amounts of styrene.N‐Acetylglucosamine and raffinose were included as reference diffusants. It was found that a decrease of the diffusion coefficients of the CD's in these polymer solutions is characteristically dependent on the polymer concentration, DS, Styrene content, and the degree of neutralization. The results were interpreted by assuming a 1:1 complex formation between CD and an appropriate residue in the polymer. The complex diffusion behavior of CD in the copolymer solutions suggested that the ability of the polymer residue to form complexes with the CD is lost when the polymer chain dimensions are reduced with decreasing neu

ISSN:0098-1273    

DOI:10.1002/pol.1978.180160504

出版商:John Wiley&Sons, Inc.    

年代:1978

数据来源: WILEY

摘要:

AbstractIt has previously been shown that, under high stress and consequently at short times to failure, a major factor governing the environmental stress cracking (ESC) of polyethylene is the ability of a liquid environment to penetrate a growing fissure at a sufficiently high speed to maintain contact with the fracture front. In this earlier study, viscosity was shown to play a significant role in this kinetic effect. The purpose of the present paper is to demonstrate that another property of the solid–liquid system influencing ESC under these high stress conditions is the spreading coefficient of the liquid on the polymer—the parameter defining the tendency of the liquid to wet the polyethylene. It has been shown that the spreading coefficient can be considered as a force and this force in conjunction with atmospheric pressure constitutes the force necessary to drive the liquid into the growing cr

ISSN:0098-1273    

DOI:10.1002/pol.1978.180160505

出版商:John Wiley&Sons, Inc.    

年代:1978

数据来源: WILEY

摘要:

AbstractIn‐service secondary creep rates of natural rubber (NR) vulcanizates at ambient temperature are known to be low. However, in tests on thin strips of NR vulcanizates in tension, secondary creep at rates of up to 120%/week were observed. From an examination of the effect of antioxidants, antiozonants, waxes, and specimen thickness it was shown that the anomalous creep was due to ozone attack on the vulcanizate, which only becomes serious in tests on thin strips in tensio

ISSN:0098-1273    

DOI:10.1002/pol.1978.180160506

出版商:John Wiley&Sons, Inc.    

年代:1978

数据来源: WILEY

摘要:

AbstractFourier transform infrared studies of the thermal degradation of polyacrylonitrile (PAN) conducted at 200°C in air and under reduced pressure are presented. The spectra are markedly superior to those published previously. A mechanism consistent with the infrared results obtained under reduced pressure is advanced, and assignments for the infrared bands occuring in the spectrum of both the reduced pressure and air degraded PAN are given

ISSN:0098-1273    

DOI:10.1002/pol.1978.180160507

出版商:John Wiley&Sons, Inc.    

年代:1978

数据来源: WILEY

摘要:

AbstractRibbon‐like lamellar single crystals of cellulose II are grown from dilute aqueous solution of cellulose triacetate (number‐average degree of polymerization (DP)‐15) by deacetylation and consequent precipitation. The best results are obtained with methylamine as the deacetylation reagent at 90°C. Electron diffraction indicates the (110) planes to be the growth face. Twin growth occurs frequently with (110) as the twinning

ISSN:0098-1273    

DOI:10.1002/pol.1978.180160508

出版商:John Wiley&Sons, Inc.    

年代:1978

数据来源: WILEY

摘要:

AbstractOzone‐degradation products of polyethylenes prepared by γ‐ray‐Induced polymerization in ethyl alcohol,t‐butyl alcohol, and 2,2,5‐trimethylhexane were analyzed by gel permeation chromatography (GPC). The ozonized polymers show two discrete peaks in the GPC traces, and the ratio of molecular weights corresponding to the peaks is close to 1:2, suggesting that these polymers are composed of folded‐chain crystals similar to solution‐grown single crystals. The peak profiles, however, are broad and the peaks in the chromatograms shift concertedly toward lower molecular weight in the course of degradation. These findings suggest that the fold surfaces of the polymers are coarse and that there is no unique crystalline core containing a regularly folded layer. The long period estimated from small‐angle x‐ray measurements increases with increasing polymerization temperature, but scarcely varies with the solvent type. This implies that when crystallization occurs during polymerization, kinetic factors may have no great effect

ISSN:0098-1273    

DOI:10.1002/pol.1978.180160509

出版商:John Wiley&Sons, Inc.    

年代:1978

数据来源: WILEY

摘要:

AbstractA detailed description of the synthesis of a model poly(isoprene‐g‐styrene) is given. From light scattering measurements the real radius of gyration of the polyisoprene is backbone is found to be smaller than that of the polystyrene branches. The core‐and‐shell conformation of graft copolymers in dilute solution in good solvents, which was proposed for poly(styrene‐g‐isoprene), is supported by th

ISSN:0098-1273    

DOI:10.1002/pol.1978.180160510

出版商:John Wiley&Sons, Inc.    

年代:1978

数据来源: WILEY