摘要:

AbstractA numerical method for calculation of the weight‐fraction distribution resulting from random crosslinking of polydisperse primary chains is suggested. The method is based on the numerical inverse Laplace transform of the weight‐fraction generating function given by the theory of branching processes. The applicability of the method was demonstrated using the Schulz‐Zimm type distribution of primary chains. A good agreement was obtained by comparing the results with those following from the kinetic theory of crosslinking for the most probable distribution of primary chains at low degrees of crossli

ISSN:0007-1641    

DOI:10.1002/pi.4980120102

出版商:John Wiley&Sons, Ltd    

年代:1980

数据来源: WILEY

摘要:

AbstractDicyclopentadiene reacts with excess sulphur in the melt at 140°C to give initially cyclic tri‐ and pentathianes which then copolymerise with further sulphur to give initially chain polymers and then finally cross‐linked species, Styrene reacts under the same conditions to give rapid initial formation of relatively high molecular weight polymeric polysulphides which then depolymerise to give a mixture of short chain species and 2,4‐diphenylthi

ISSN:0007-1641    

DOI:10.1002/pi.4980120103

出版商:John Wiley&Sons, Ltd    

年代:1980

数据来源: WILEY

摘要:

AbstractThe effect of a range of chemically dissimilar solvents on the Tg of PET is dependent upon dispersion forces. A correlation is presented between the dispersion solubility parameters (δd) of the solvents and the reduction of theTgwhich they cause. Two experimentally determed values for the (δd) of PET are presented as evidence to support the claim that aromatic and cyclic solvents solvate the aromatic part of the repeat unit and aliphatic solvents solvate the aliphatic par

ISSN:0007-1641    

DOI:10.1002/pi.4980120104

出版商:John Wiley&Sons, Ltd    

年代:1980

数据来源: WILEY

摘要:

AbstractSimultaneous measurements of stress and birefringence were made on a vulcanized styrene‐butadiene rubber (SBR) at 0°, 15° and 25°C. The stress‐strain curves at all temperatures showed a strong upward deviation from the Gaussian statistical theory at high extensions which became more pronounced with decreasing temperature due to the increasing extension to break. The birefringence, however, was substantially of the form predicted by the Gaussian theory. Comparison studies on natural rubber under similar conditions of experiment showed birefringence and hysteresis effects which could be interpreted on the basis of strain‐induced crystallisation (as revealed by X‐rays). Such effects were completely absent in the SBR samples which also showed no evidence of crystallisation on X‐ray examination in the stretched state. It is concluded that the upturn in stress‐strain curve in both materials is primarily due to the limited extensibility of the network, as treated in the non‐Gaussian statistical theory, and that crystallisation, when present, plays only a

ISSN:0007-1641    

DOI:10.1002/pi.4980120105

出版商:John Wiley&Sons, Ltd    

年代:1980

数据来源: WILEY

摘要:

AbstractFracture properties of a wide range of filled unsaturated polyester resin composites have been investigated with respect to filler size, shape, loading and adhesion to the matrix resin. Mechanisms are proposed for the fracture behaviors found, based on geometrical considerations of interacting filler particles and stress concentrations which result from them.

ISSN:0007-1641    

DOI:10.1002/pi.4980120106

出版商:John Wiley&Sons, Ltd    

年代:1980

数据来源: WILEY

摘要:

AbstractThe factor for the refraction correction was considered for the Fica 50 type of light scattering photometer, in which the scattered light is twice refracted before reaching the detector. The correction factor was first calculated after Hermans and Levinson, which elucidated that the factor is just the same as for the Brice type of photometer, and a vat liquid has no further effects on the final form of the correction factor. This result was examined and found to be practically applicable to a Fica 50 photometer by measuring the scattering intensities of several liquids and the RAPRA PS2 standard polystyrene in solvents of varying refractive index.

ISSN:0007-1641    

DOI:10.1002/pi.4980120107

出版商:John Wiley&Sons, Ltd    

年代:1980

数据来源: WILEY

摘要:

AbstractThe interaction of nitrogen monoxide (nitric oxide, NO) with pyrolysed polyacrylonitrile (PANP) has been examined together with the feasibility of the use of PANP based catalysts for the removal of small quantities of NO from the exhaust systems of internal combustion engines. Kinetic studies indicated that PANP was capable of interacting with and removing NO from an inert carrier gas and that the initial specificity of this interaction was little affected by hydrogen, hydrocarbons, carbon monixide or oxygen, the initial rates of removal being appreciably higher than those obtainable with conventional inorganic catalysts or graphitised carbon. The activation energy and kinetic features of the reaction suggested that the interaction involved the odd electron nature of NO and the free spin generated at the polymer surface. Once adsorbed the nitric oxide decomposes to form dinitrogen oxide (N2O) which is further reduced to nitrogen with concurrent assimilation and rearrangement of oxygen within the polymer structure. As a result the PANP gradually loses its capacity to adsorb and decompose NO. In addition, it appears that the structural features which promote the oxidative instability of PANP also govern its NO removal ability. Consequently, the lifetime and therefore practical utility of these systems is governed by the limits of oxidative stability and catalytic capacity.

ISSN:0007-1641    

DOI:10.1002/pi.4980120108

出版商:John Wiley&Sons, Ltd    

年代:1980

数据来源: WILEY

ISSN:0007-1641    

DOI:10.1002/pi.4980120109

出版商:John Wiley&Sons, Ltd    

年代:1980

数据来源: WILEY

ISSN:0007-1641    

DOI:10.1002/pi.4980120101

出版商:John Wiley&Sons, Ltd    

年代:1980

数据来源: WILEY