摘要:

Thiol-containing antioxidants such as 4-(mercaptoacetamido)-diphenylamine (MADA) undergo ready addition of-SH groups to the double bonds in diene rubbers in the presence of initiators. The reaction is a radical chain process leading to rubbers with improved thermooxidative resistance. The modification reaction has been carried out on high cis-polyisoprene and polybutadiene, and conditions under which the physicochemical properties (e.g., inherent viscosity, gel content, and microstructure) are less affected have been found. An oxygen absorption test and DSC were used as rapid methods for evaluation of thermooxidative stability of modified rubbers. The superiority of rubbers with MADA chemically attached (ranging from 1 to 4 phr) was shown by a circulating air oven test and by an extraction process which simulates the aggressive environments experienced by many rubbers under practical conditions. The results obtained show that a small degree of modification (1 phr MADA) is large enough to provide good thermooxidative stability without alteration of the molecular characteristics of the parent rubbers. At higher degrees, cistrans isomerization can occur.

ISSN:0022-233X    

DOI:10.1080/00222338508056621

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

A number of new polymers have been studied. They include polymers obtained by chain reaction polymerization of olefins and epoxides with functional groups where the polymerizable group was separated from the functional group by an inert spacer group, the preparation of head-to-head polymers, and the preparation of optically active polymers based on the macromolecular asymmetry.

ISSN:0022-233X    

DOI:10.1080/00222338508056622

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

This paper describes the synthesis and characterization of some polycondensation polymers (poly- and copolyamides, polyesters) which contain cycloaliphatic units in their chains. Syntheses were carried out by a low-temperature polycondensation technique (interfacial and solution), and also by the Yamazaki method in NMP-pyridine solution using triphenylphosphite as the catalyst. The products obtained were characterized by elemental analysis, IR, and x-ray diffraction. Thermoanalytical data have shown very good thermal properties for all products, but especially for the aromatic cycloaliphatic polyamides which were stable up to 400°C.

ISSN:0022-233X    

DOI:10.1080/00222338508056623

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

The ceric ion method has been used to graft acrylic acid directly onto cellulose with a minimum amount of homopolymer. The method utilizes the pretreatment of the cellulose with ceric ammonium nitrate followed by washing out any excess of the catalyst. Oxygen can be present with the pretreatment step, but must be excluded during the grafting reaction itself. The process, which is entirely aqueous in nature, would appear to be quite practical on a large scale. Wet strengthened papers which are essential for the use of the grafted products as ion-exchange media can also be grafted but with adequate but lower yields than with the untreated paper. Apart from ion exchange, the products are of considerable potential value as water sorbing agents. Methacrylic acid gave lower grafting yields than acrylic acid, but these were much improved at higher temperatures.

ISSN:0022-233X    

DOI:10.1080/00222338508056624

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

Some results on the polymerization of acrylamide in heterogeneous systems are presented. The first part presents the polymerization of acrylamide in inverse suspension; the steps of the reaction and the part played by each factor that influences the advancement of the reaction are discussed. Some aspects whose elucidation was required throughout the investigation are presented, together with a hypothesis and the experimental results obtained. The second part presents reactions of the modifications achieved with the polymers obtained in inverse suspension and the properties of modified polymers. The final section reports some attempts to entrap some enzymes in polyacrylamide gel. The results of entrapment by copolymerization of acrylamide with methylenebisacrylamide in a homogeneous system are presented comparatively with those yielded by the same reaction in a heterogeneous system.

ISSN:0022-233X    

DOI:10.1080/00222338508056625

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

The author' work on preparing polyethers with reactive side chains is reviewed with emphasis on hydroxy polyethers. High molecular weight hydroxy polyethers were prepared by polymerizing epoxides containing a hydroxyl group protected with an appropriate group such as SiMe3and then removing it by hydrolysis.

ISSN:0022-233X    

DOI:10.1080/00222338508056626

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

The dibenzyl system represents the simplest biaromatic system able for rotational isomerism which allows multiple spatial arrangements, with different reciprocal influences of the functional groups situated in the two rings. The possibility of introducing this system to a macromolecular chain and its influence on some properties of the polymer obtained was studied of the cases of polyurethanes, polyureas, poly(parabanic acids), and poly-imides. In the case of copolyurethanes, made using 4,4′-dibenzyl-diiSocyanate, an unexpected phenomenon was the possibility of disproportionation of some homogeneous systems by two parallel polyaddition processes which progress in parallel in two places, i.e., solution and suspension, leading to different polymers. The process is probably governed by the lower entropy of the crystalline polymer which appears in suspension. Some practical applications of polymers with dibenzyl structures are presented.

ISSN:0022-233X    

DOI:10.1080/00222338508056627

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

Two ion-pair comonomers of 2-methacryloyloxyethyltrimethyl-ammonium 2-methacryloyloxyethanesulfonate (METMAMES) and 3-acrylamido-3-methylbutyltrimethylammonium 2-acrylamido-2-methylpropanesulfonate have been synthesized. The spontaneous and radical homocopolymerizations of these monomer pairs, wherein no nonpolymerizable counterions are present, have also been studied. Moreover, the intrinsic viscosity of the homocopolymer derived from METMA MES was found to increase with increasing KCl concentration in aqueous solutions.

ISSN:0022-233X    

DOI:10.1080/00222338508056628

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

Application of anionic polymerization and group transfer polymerization to the synthesis of methacrylate polymers with one or two functional endgroups and with functional groups in the side chain is described. Success in the preparation of end-functional polymers depends largely on the absence of chain transfer and chain termination reactions. The higher stability of living chains in group transfer polymerization at temperatures as high as 100°C makes it the preferred route to functional polymers.

ISSN:0022-233X    

DOI:10.1080/00222338508056629

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

A new principle for improving the catalytic activity of the classical complexes CuCl2-aliphatic amines used for the oxidative coupling of 2,6-dimethylphenol (DMP) is presented. It is based on the “trans” effect, typical of the substitution reactions of ligands in the square planar complexes of platinum(II). Thus, by replacing a Cl−anion with a strong “trans” effect-giving ligand such as NO2−, CN−, RS−,, a significant increase in the rate of oxidative coupling of 2,6-DMP is observed. It was quantitatively estimated by measuring the oxygen absorption rate. The highest reaction rates are given by complexes having CUS bonds (mercap-tides, thiophenolates, thiosulfates). These bonds, which probably have a high oxygen affinity, are typical for copper-containing enzymes (laccase, tyrosinase, ascorbic acid oxidase), redox enzymes that catalyze the oxidative coupling of some natural phenols very efficiently.

ISSN:0022-233X    

DOI:10.1080/00222338508056630

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor