摘要:

AbstractThis paper describes an investigation into the degradation of a purified epoxide based on the diglycidyl ether of bisphenol A hardened withp,p′‐diaminodiphenylmethane. The method used was that of hot‐wire pyrolysis followed by gas chromatography. Special attention was given to the problem of solid residues formed on the pyrolyzer tube, and evidence was found that these probably contain oligomers. Resonance‐stabilized free radicals also appear to be formed, and evidence is found to support the idea of dehydration during degradation, originally put forward by Lee. An attempt, based on first principles, is made to explain the degradation of epoxides, using evidence from previous work as well as that described in thi

ISSN:0021-8995    

DOI:10.1002/app.1967.070110701

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

年代:1967

数据来源: WILEY

摘要:

AbstractThe parallel between fibers and metals is discussed in terms of their behavior upon heat treatment, crystallite size and orientation, and diffusion of atoms and molecules. It is pointed out that the degree of crystallinity employed to interpret the x‐ray diffraction patterns of fibers is not an important physical parameter. The need for critical study of the mechanism of the growth of primary and secondary walls is stressed for a better understanding of the physical properties of fibers. Reference is made to Hosemann's theory of paracrystals which will help to resolve the “open” problems in polymer ph

ISSN:0021-8995    

DOI:10.1002/app.1967.070110702

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

年代:1967

数据来源: WILEY

摘要:

AbstractA generalized flow theory is put forward which is derived from a review of accepted types of stress–response curves. The theory is summarized in a single flow curve of universal shape from which all types of liquid flow can be interpreted. This “generalized flow curve” can be applied to polymer melts in particular, but there is no reason why it should not equally apply to solutions, dispersions, suspensions, emulsions, or pure liquids. The generalized flow curve is exactly analogous to the typical fully developed load–deformation curve which applies to tough plastics in the solid state. A molecular interpretation of the processes involved in producing the flow phenomena implicit in the various portions of the generalized flow curve is put forward. The evidence on which the theory is based is reviewed. Some fundamental implications are di

ISSN:0021-8995    

DOI:10.1002/app.1967.070110703

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

年代:1967

数据来源: WILEY

摘要:

AbstractTime dependence in the melt indexing of polyolefins stabilized against thermally induced changes is well known, the prevalent effect being an increase in melt index toward a steady‐state value. The melt index of polyethylenes compounded with carbon black has been found to decrease, in some cases radically, although oxygen uptake data show no evidence of thermal instability. The melt index–time plot can be restored to its normal shape by adding excess quantities of a standard thioether antioxidant. Data are rationalized by assuming that polyethylene adsorbs on the available pigment surface, forming a crosslink network. The thioether antioxidant, however, may adsorb preferentially, thereby restoring the normal response of the polymer to forces resulting in its capillary extrusion. The results emphasize the contribution of chain orientation effects to the time dependence of melt in

ISSN:0021-8995    

DOI:10.1002/app.1967.070110704

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

年代:1967

数据来源: WILEY

摘要:

AbstractThe infrared spectra of unsaturated polyesters in process of cure have been taken of samples free from unreacted protion. Styrene and polyester fractions in the curing polyester films were assessed from comparison of the band intensities at 695 and 740 cm.−1. The styrene fraction in curing films was found to increase as cure proceeded, and the delayed curing was seen to be accompanied by a build‐up of films of lower styrene content. The differences between samples observed in the mechanical behavior were considered attributable for the most part to the difference in styrene cont

ISSN:0021-8995    

DOI:10.1002/app.1967.070110705

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

年代:1967

数据来源: WILEY

摘要:

AbstractSamples of commercially prepared poly(methyl methacrylate) (Lucite) were irradiated with 13‐M.e.v. electrons in the dose range 0–11 Mrad, and the induced changes in the index of refraction, density, and dielectric constant were observed. An attempt is made to interrelate the observed changes theoretica

ISSN:0021-8995    

DOI:10.1002/app.1967.070110706

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

年代:1967

数据来源: WILEY

摘要:

AbstractA method is described for deriving by digital computer a temperature program which, when applied to batch polymerization, will keep the supply of new free radicals constant throughout the main part of the reaction.

ISSN:0021-8995    

DOI:10.1002/app.1967.070110707

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

年代:1967

数据来源: WILEY

摘要:

AbstractThe temperature dependence of acoustic shear velocities are reported for Poly‐Penco nylon, type G Plexiglass [poly(methyl methacrylate)], TFE Teflon (tetrafluoroethylene), low‐ and high‐density polyethylene, Lexan (polycarbonate), and Delrin Acetal (nylon). Most of the data were obtained at a frequency of 1 Mc./sec. over the temperature range of 25–100°C. In addition, previously unreported longitudinal velocities to ∼125°C. are reported for Lexan and De

ISSN:0021-8995    

DOI:10.1002/app.1967.070110708

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

年代:1967

数据来源: WILEY

摘要:

AbstractRadiation‐induced solid‐state polymerization in binary systems containing long‐chain compounds has been investigated. Butyl stearate–methyl methacrylate and stearyl alcohol–methyl methacrylate systems have been studied in detail. In these systems insource polymerization does not occur but a remarkable post‐polymerization takes place on warming after irradiation at low temperature. The limiting conversion characteristics of this post‐polymerization depend greatly on the nature and the concentration of the long‐chain compounds. The post‐polymerization is observed to be more marked in the butyl stearate–methyl methacrylate system than in the stearyl alcohol–methyl methacrylate system, and it increases with increasing concentration of the long‐chain component. An optimum warming rate and warming temperature exists for the maximum saturated conversion. Irradiation in air causes some decrease of conversion compared to irradiationin vacuo. The possible mechanism is that monomer diffuses into the crystals of the long‐chain compound after melting at the eutectic temperature. The polymerization may be initiated by trapped radicals of the long‐chain compound and carried out in the crystal of the long‐chain compound with a smaller possibility of termination. In binary systems containing long‐chain compounds, lowering of the melting point is slight, and the eutectic composition exists at the richer composition of monomer, so almost all the long‐chain substance remains as excess crystals, which are suitable for holding trapped radicals. The crystal lattices of long‐chain compounds may be softer than those of compounds of small molecular size. This fact is favorable for monomer diffusion. This explains why such a post‐polymerization takes place only in sy

ISSN:0021-8995    

DOI:10.1002/app.1967.070110709

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

年代:1967

数据来源: WILEY

摘要:

AbstractThe radiation‐induced solid‐state polymerization in the binary systems such as acryl‐amide–methacrylamide and acrylamide–acenaphthylene was studied. The former system forms a solid solution, and the latter one forms a eutectic mixture. In the solid solution, the polymerization proceeds homogeneously and copolymer is formed, while in the eutectic mixture, it proceeds heterogeneously, forming only homopolymer. The post‐polymerization of the same binary systems was also studied. Linearity between the conversion and the logarithm of the post‐polymerization time was found for the various monomer compositions at various temperatures. This relationship satisfied the kinetic equation presented by Morawetz et al. for the post‐polymerization of acrylamide. The kinetics of the binary systems might be considered similarly to the single system, considering that the crystalline state of the system is changed by the monom

ISSN:0021-8995    

DOI:10.1002/app.1967.070110710

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

年代:1967

数据来源: WILEY