ISSN:0022-233X    

DOI:10.1080/00222337808061367

出版商:Taylor & Francis Group    

年代:1978

数据来源: Taylor

摘要:

Despite the fact that polyvinyl chloride) (PVC) has occupied the most important position among general-purpose plastics, its industrial applications are limited due to its inferior thermal stability and mechanical properties. Many studies have been conducted to remedy these disadvantages. This paper reviews these studies from the viewpoint of chemical modification of PVC.

ISSN:0022-233X    

DOI:10.1080/00222337808061368

出版商:Taylor & Francis Group    

年代:1978

数据来源: Taylor

摘要:

The synthesis, characterization and some physical properties of polyvinyl chloride-g-styrene) are described. The graft copolymer was prepared by initiating the polymerization of styrene with polyvinyl chloride) in conjunction with Et2AlCl. Graft copolymer characterization involved GPC, T, heatstability, and intrinsic viscosity studies. Among the physical properties stress-strain and impact strength measurements have been carried out.

ISSN:0022-233X    

DOI:10.1080/00222337808061369

出版商:Taylor & Francis Group    

年代:1978

数据来源: Taylor

摘要:

The effects of crosslinking on PVC are well known in regard to the improvement of mechanical properties, creep behavior, and softening temperature. Little is known, however, on the application of the PVC-crosslinking reaction, because most of crosslinked PVC tends to color easily at elevated temperatures. In this paper, a novel PVC-crosslinking reaction with 2-R-4,6-dithiol-s-triazine (I) has been presented to obtain insoluble products which hardly color on ageing. The reaction rate and induction period of the crosslinking reaction with I are made controllable by selecting the basicity of the substituent R of I as well as that of an acid acceptor in the blends. The utility of I as stabilizer as well as a crosslinking agent is also emphasized.

ISSN:0022-233X    

DOI:10.1080/00222337808061370

出版商:Taylor & Francis Group    

年代:1978

数据来源: Taylor

摘要:

β,β-Dideuterated poly(viny1 chloride) (β,β -d2-PVC) was chlorinated under conditions of photochemical suspension chlorination in concentrated hydrochloric acid with addition of chloroform as a swelling agent, and also under conditions of thermal solution chlorination in tetrachloroethane. The1H-NMR spectra of chlorinated β,β -d2PVC (β,β -d2CPVC) were measured. The deuterium concentration was determined in combustion products of β,β -d2CPVC as the D2O:H2O ratio by means of mass spectroscopy. It was found that the concentration of CHC1- groups decreases in both the photochemical suspension chlorination and in the thermal solution chlorination. The structural nonidentity of β,β -d2PVC chlorinated in suspension and in solution was confirmed.

ISSN:0022-233X    

DOI:10.1080/00222337808061371

出版商:Taylor & Francis Group    

年代:1978

数据来源: Taylor

摘要:

Four samples of PVC polymerized in suspension (S) or emulsion (E) or in bulk at two different temperatures (Mi and M2) have been treated by ozone between -20 and 120°C, either in the solid state or in tetrachloroethane solution. Chain scission and peroxidation are observed with a clear parallel between the two processes. The polymer which contains the smaller amount of internal double bond (broken down at -20°C) is less sensitive to peroxidation and further chain scission at higher temperatures. Chemical or thermal peroxide decomposition experiments show that there are no residual peroxide structures in the backbone of the chain and the presence of ozone is necessary to cause chain scission. Ozonization in the solid state shows that, under Tg, the peroxidation process involves a dehydrochlorination step. A tentative mechanism for the ozonization process is suggested.

ISSN:0022-233X    

DOI:10.1080/00222337808061372

出版商:Taylor & Francis Group    

年代:1978

数据来源: Taylor

摘要:

From previous investigations of the alkaline dehydrochlorination of PVC it is well known that polyene sequences are formed. In this paper the true overall kinetics of the dehydrochlorination reaction between PVC and alcoholic KOH in tetrahydrofuran solution was studied at 9.5°C by measuring the rate of disappearance of KOH. Titrations of the hydroxide ions consumed and the chloride ions evolved showed close agreement. IR spectra of the samples did not show any evidence of substitution by hydroxide ions. Small amounts of DMSO present in the solvent were found to increase the reaction rate markedly. The kinetic scheme was discussed and the first rate constant was determined. Preliminary results of reactions of the polyene sequences with various reagents are presented. These reactions were made in order to introduce new functional groups into the PVC chains.

ISSN:0022-233X    

DOI:10.1080/00222337808061373

出版商:Taylor & Francis Group    

年代:1978

数据来源: Taylor

摘要:

The effect of solvent structure, particularly the application of the low molecular weight aliphatic alcohols, on the radiation grafting of monomers to PVC with the use of cobalt-60 and the simultaneous procedure is discussed. The addition of sulfuric acid to a typical system such as styrene/methanol/PVC enhances both the grafting yield and the size of the Trommsdorff peak. The results are shown to be consistent with a mechanism involving charge-transfer complex formation between monomer and grafting site in PVC. The role of hydrogen atoms in these reactions, particularly in the presence of sulfuric acid, is emphasized, and the importance of the magnitude of G(H) on the grafting yields and the Trommsdorff effect is discussed. These principles, developed for radiation grafting styrene, are shown to be of value for the radiation copolymerization of p-nitrostyrene and vinyl phosphorus monomers to PVC. The use of these PVC copolymers for immobilizing enzymes such as trypsin and heterogenizing typical catalytically active homogeneous metal complexes is described.

ISSN:0022-233X    

DOI:10.1080/00222337808061374

出版商:Taylor & Francis Group    

年代:1978

数据来源: Taylor

摘要:

The reaction kinetics and characterization of the reaction products of the modification of the vinyl chloride oligomer containing CCl3end groups by n-butyl methacrylate in the presence of copper (II) ephedrinate was studied. The reaction product contains three high molecular weight components: modi- fied poly(vinyl chloride) (copolymer), unchanged vinyl chloride oligomer, and poly(n-butyl methacrylate) homopolymer. The extent of the modification process depends on the molar ratio between the concentration of the halogen-containing groups utilizable for the reaction with metal chelate and on the concentration of metal chelate. If there is a molar excess of chelate compared with the molar concentration of CCl3end groups in vinyl chloride oligomer, then other halogen-containing groups besides CCl3end groups of vinyl chloride oligomer are used in the formation of modified poly(viny1 chloride). This enables incorporation of more than two poly(n-butyl methacrylate) sequences into the poly(vinyl chloride) chain.

ISSN:0022-233X    

DOI:10.1080/00222337808061375

出版商:Taylor & Francis Group    

年代:1978

数据来源: Taylor

摘要:

The grafting on polyvinyl chloride) by carbanionic deactivation of a living polymer involves two types of reactions: a nucelophilic substitution (SNg) and an elimination (E2). Under the experimental conditions, of our study, we did not observe metallation of the polyvinyl chloride) chain. The influence of different parameters on the ratio E/S of the two reactions has been studied. The substitution is enhanced when the basicity of the carbanion is decreased. Higher temperatures favor the elimination, which might be due to the relative change in the nature of the different ionic species. The appearance of conjugated double bonds, the electroattractive character of which makes the hydrogen atom in theaposition of the C-Cl bond labile, favors autoacceleration of the elimination reaction. The shorter the living chain, higher the yield in substituted product. Steric hindrance of the random coils of PVC and living polymer also plays an important role.

ISSN:0022-233X    

DOI:10.1080/00222337808061376

出版商:Taylor & Francis Group    

年代:1978

数据来源: Taylor