摘要:

AbstractThe photoinitiated reactions of bromotrichloromethane and of carbon tetrabromide on styrene, and of bromotrichloromethane on methyl methacrylate have been studied. The products have been analysed by gel permeation chromatography and the transfer constants for the first few steps in the polymerisations have been determined; some Arrhenius parameters have also been found. The processes may provide a synthetic route to a number of oligomers which are difficult to form by other methods.

ISSN:0007-1641    

DOI:10.1002/pi.4980030201

出版商:John Wiley&Sons, Ltd    

年代:1971

数据来源: WILEY

摘要:

AbstractThe historical development of the polyester‐rubber adhesive Pexul is described. This substance can be used in single‐ or two‐stage dipping in conjunction with a resorcinol‐formaldehyde latex for the adhesion of polyester cords to rubber.The most effective formulation is a molecule consisting of two molecules of resorcinol linked to a central p‐chlorophenol molecule by means of formaldehyde (methylene links), but the commercial product contains many related compounds.Its mode of action is postulated to be (a) adhesion of the substance to the surface of the polyester as a result of good matching of the cohesive energy densities and hydrogen bonding between the polyester oxygen atoms and the phenolic hydroxyls; and (b) thermal polycondensation of the surface film to give a strongly adherent crosslinked film which simultaneously or subsequently reacts with RF‐latex to form a complete system capable of bonding to rubber.The determination of Pexul on dipped cords by chlorine analysis and by the use of trace metals and X‐ray fluorescence

ISSN:0007-1641    

DOI:10.1002/pi.4980030202

出版商:John Wiley&Sons, Ltd    

年代:1971

数据来源: WILEY

摘要:

AbstractSome of the general features of the way in which the nature of the polymer substrate influences the fading of dyes by light are briefly surveyed. The effects of oxygen, water vapour and atmospheric contaminants are considered in particular. It is suggested that singlet oxygen and hydrogen peroxide vapour play an important role in the fading of many dyes.

ISSN:0007-1641    

DOI:10.1002/pi.4980030203

出版商:John Wiley&Sons, Ltd    

年代:1971

数据来源: WILEY

摘要:

AbstractNylon 6 and nylon 6.6 yarns were subjected to wet heat in a relaxed state and the subsequent rate of dyeing of these yarns with Durazol Blue 2R was then studied. The rate of dyeing progressively increased as the temperature of steaming increased. For nylon 6 this increase in rate of dyeing was almost eightfold in heating up to 140°C compared with that of unheated samples; for nylon 6.6 the increase was threefold after heating in steam at 150°C. It was confirmed that Fick's law is still valid for describing the dyeing process with nylon 6.6 but not with nylon 6. Measurements of density, birefringence, X‐ray orientation and degree of lateral order by an X‐ray method show that these are all increased by the steam treatments. There is little change in the moisture regain and amine end‐group content. An explanation of these observations is advanced in terms of a morphology that allows an increase in the size, shape or quantity of voids on heating the polyamides i

ISSN:0007-1641    

DOI:10.1002/pi.4980030204

出版商:John Wiley&Sons, Ltd    

年代:1971

数据来源: WILEY

摘要:

AbstractExplanations of the deviations of polymer crystallisation isotherms from Avrami equations are considered in the light of the assumptions inherent in the derivation of the equations and analysis of the crystallisation isotherms; these explanations are rejected. Modified equations which allow for the presence of several crystallisation mechanisms and recrystallisation are considered to be a more satisfactory physical model of spherulitic crystallisation from the melt. While they describe the crystallisation isotherms more accurately than a single Avrami process, non‐random deviations which cannot be satisfactorily explained still exist. Further modifications to include changing nucleation characteristics, induction periods, etc., do not improve the fit of these modified equation

ISSN:0007-1641    

DOI:10.1002/pi.4980030205

出版商:John Wiley&Sons, Ltd    

年代:1971

数据来源: WILEY

摘要:

AbstractPolythiocarbamate polymers have been prepared from a prepolymer containing terminal isocyanate groups, obtained from reaction of a low molecular weight thiol‐terminated polymer with a diisocyanate. The prepolymer was chain extended and crosslinked with diols. and triols. Optimum conditions for prepolymer formation were established. Void formation in prepolymer is avoided by use of antioxidants but is difficult to prevent in the crosslinked material. Isocyanate appeared to be consumed in a reaction other than directly with thiol, and a water‐forming oxidation may be involved. A crosslinking reaction involving the thiocarbamate hydrogen and isocyanate appears to be favoured, contrary to results with carbamates. The nature of an isocyanate and catalyst complex is discus

ISSN:0007-1641    

DOI:10.1002/pi.4980030206

出版商:John Wiley&Sons, Ltd    

年代:1971

数据来源: WILEY

摘要:

AbstractThe thermal degradation of a series of cured melamine‐formaldehyde resins and of two relevant model compounds has been investigated using thermogravimetry accompanied by the analysis of volatile products. Low temperature degradation reactions which occur up to ∼350°C involve the loss of water and formaldehyde, the latter arising from reversible demethylolation reactions.It is proposed that ether linkages, which model compound studies indicate would yield formaldehyde in the low temperature region, are not present to any significant degree in cured resins. Deep‐seated rupture of the polycondensate system takes place at temperatures above ∼375°C when a number of independent reactions involving both side‐chain and ring degradation give rise to products among which ammonia, hydrogen cyanide, carbon monoxide and melamine have be

ISSN:0007-1641    

DOI:10.1002/pi.4980030207

出版商:John Wiley&Sons, Ltd    

年代:1971

数据来源: WILEY

摘要:

AbstractIn the preparation of novolac resins, three possible dimers with slightly different molecular dimensions may be produced in the polymerisation reaction. Gel permeation studies were carried out on four novolac resins prepared using different acid catalysts, and the results indicated that the nature of the catalyst influences the type and quantity of dimer produced. The weight and number average molecular weights were also calculated from the chromatograms obtained.

ISSN:0007-1641    

DOI:10.1002/pi.4980030208

出版商:John Wiley&Sons, Ltd    

年代:1971

数据来源: WILEY

ISSN:0007-1641    

DOI:10.1002/pi.4980030209

出版商:John Wiley&Sons, Ltd    

年代:1971

数据来源: WILEY

ISSN:0007-1641    

DOI:10.1002/pi.4980030212

出版商:John Wiley&Sons, Ltd    

年代:1971

数据来源: WILEY