摘要:

AbstractMethods are described for identifying polyamides, polyurethanes, ethylene–vinyl acetate resins, polyesters, rosins and their esters, polyisobutenes and paraffin waxes in “hot‐melt” adhesives, by a combination of chemical tests and infrared spectrophotometry. Mixtures are separated quantitatively into their components by selective solvent extraction before

ISSN:0007-1641    

DOI:10.1002/pi.4980040102

出版商:John Wiley&Sons, Ltd    

年代:1972

数据来源: WILEY

摘要:

AbstractThe initial stages in the development of spherulites from primary nuclei to spherical arrays of branching fibrils are included in the kinetics of polymer crystallisation. Since most of the experimental isotherms exhibit the required time dependence only over a limited range it is considered that the model has little use, and these initial stages in the development of spherulites have little effect on the degree of fit of the experimental isotherms to the Avrami rate equation.The general time dependences of crystallisations developing as a branching process is outlined and compared with that of the Avrami equations for growth of spherical particles.

ISSN:0007-1641    

DOI:10.1002/pi.4980040103

出版商:John Wiley&Sons, Ltd    

年代:1972

数据来源: WILEY

摘要:

AbstractThe possibility that the presence of several processes occurring during the crystallisation of polymers may account for anomalous constant fractional values of the Avrami exponent is reconsidered, and for various reasons rejected. Experimental isotherms exhibit systematic variations when analysed as two stage processes, which can only be accounted for by fractionalnvalues of no theoretical significance. An explanation for these deviations must be sought in the mechanism of spherulitic crystallisation, and in particular the mechanism of branching and impurity rejection of the basic fibrillar units.

ISSN:0007-1641    

DOI:10.1002/pi.4980040104

出版商:John Wiley&Sons, Ltd    

年代:1972

数据来源: WILEY

摘要:

AbstractThe thermal decomposition of a polyester and a polyether flexible foam in a nitrogen atmosphere has been studied by gas chromatography, mass spec‐trometry and elemental ultramicroanalysis. It is shown that the decomposition behaviours of the two foams are similar. At low temperatures (200 to 300 °C) there is a rapid and complete loss of the tolylene diisocyanate unit of each foam as a volatile yellow smoke leaving a polyol residue. The smoke has been isolated as a yellow solid (common to both foams) which contains virtually all of the nitrogen of the original foams and, under the conditions of test, is stable at temperatures up to 750 °C. Nitrogen‐containing products of low molecular weight (mainly hydrogen cyanide, acetonitrile, acrylonitrile, pyridine and benzonitrile) observed during the high temperature decomposition (over 800 °C) of the foams are shown to be derived from the yellow smokes. At 1000 °C, approximately 70% of the available nitrogen has been recovered as hydrogen

ISSN:0007-1641    

DOI:10.1002/pi.4980040105

出版商:John Wiley&Sons, Ltd    

年代:1972

数据来源: WILEY

摘要:

AbstractProducts from the thermal decomposition of four polyurethane foams heated to temperatures in the range 220 to 400 °C, in atmospheres of nitrogen, of 6% oxygen in nitrogen and of air were examined for some of the anticipated toxic materials. When phosphorus‐containing inhibitors were added to or chemically incorporated in the foams, phosphorus compounds were evolved under most of the conditions employed. Other materials detected were hydrogen cyanide, isocyanate, urea, halogenated compounds and alkenes. A brief discussion is given of the hazard presented by polyurethane foams decomposing under these conditio

ISSN:0007-1641    

DOI:10.1002/pi.4980040106

出版商:John Wiley&Sons, Ltd    

年代:1972

数据来源: WILEY

摘要:

AbstractThe influence of some benzophenone‐type ultraviolet absorbers in a general PVC formulation has been studied by determining rates of photo‐oxidation when specimens were exposed to xenon‐arc irradiation under controlled conditions. Replicates of the formulation but without the absorbers were similarly photo‐oxidised behind a series of glass filters to provide a basis for assessing the effectiveness of the absorbers. Some changes in appearance of the specimens have also been measured and discussed in relation to the data on photo‐oxida

ISSN:0007-1641    

DOI:10.1002/pi.4980040107

出版商:John Wiley&Sons, Ltd    

年代:1972

数据来源: WILEY

摘要:

AbstractThe minimum sequence length for crystallisation in a polymer was determined by a novel kinetic approach using sequence analysis of a series of blocky terpolymers.Copolymers and terpolymers of ethylene, propylene, and but‐l‐ene were prepared with a Ziegler–Natta catalyst system. Compositions of feeds and polymers were analysed, and kinetic reactivity parameters were calculated using both the Fineman–Ross and Alfrey–Goldfinger approaches. The parameters were then applied to determine the sequence length distribution of each component in the terpolymers. Also, deliberate control of sequence lengths enabled synthesis of heptane‐soluble, rubbery polymers even using a catalyst system which normally produced blocky materials.Crystalline contents of the terpolymers were determined experimentally by nitric acid digestion. A critical comparison of the measured crystallinities with the calculated sequence length distributions was thereby made possible. From this comparison a minimum sequence length of monomer below which crystallisation did not occur was estimated; this length was approximately 20 backbone c

ISSN:0007-1641    

DOI:10.1002/pi.4980040108

出版商:John Wiley&Sons, Ltd    

年代:1972

数据来源: WILEY

ISSN:0007-1641    

DOI:10.1002/pi.4980040109

出版商:John Wiley&Sons, Ltd    

年代:1972

数据来源: WILEY

ISSN:0007-1641    

DOI:10.1002/pi.4980040110

出版商:John Wiley&Sons, Ltd    

年代:1972

数据来源: WILEY

ISSN:0007-1641    

DOI:10.1002/pi.4980040101

出版商:John Wiley&Sons, Ltd    

年代:1972

数据来源: WILEY