A. K. Mukherjee

Graft Copolymerization of Vinyl Monomers onto Polypropylene

Abstract Modification of polymeric materials to improve their performance for specific use has been a fascinating field for research. A great amount of research work has been published in this area [1, 2]. Modification of polymers through graft copolymerization offers an effective means for introducing some desirable properties into the polymer without affecting the architecture of the polymer backbone.

Dehydrochlorination of Poly(vinyl Chloride) in Pyridine. 1. Effect of Conditions

Abstract Poly(viny1 chloride) (PVC) was dehydrochlorinated thermally in pyridine solution under N2 atmosphere and the effect of variation of reaction time, temperature, and concentration of PVC in pyridine was studied. The extent of dehydrochlorination (or conversion, x%) increases with an increase in reaction time and temperature, and with a decrease in the concentration of PVC. Incomplete precipitation of dehydrochlorinated PVC (DHPVC) occurs by nonsolvent (methanol). During dehydrochlorination there is no HCl evolution as it forms a pyridine hydrochloride complex which is supposed to act as a catalyst for dehydrochlorination. A possible mechanism has been proposed. Chain scission and cross-linking reactions are responsible for the molecular weight changes that take place during the reaction.

Grafting Vinyl Monomers onto Nylon 6 Fiber. II. Graft Copolymerization of Methyl Methacrylate onto Nylon 6 Fiber by Photoirradiation in the Presence of Fructose

Abstract Photopolymerization of methyl methacrylate (MMA) onto nylon 6 fiber by UV radiation in alcoholic solutions of water-methanol, water-ethanol, and water-n-propanol in the presence of fructose was investigated. The effects of monomer concentration, time of polymerization, fructose concentration, and effect of media have also been studied. Graft add-on (GAO) % greatly enhanced with an increase in monomer concentration and time. With fructose concentration it increases up to 15 mmol/L of fructose and thereafter falls. The GAO in the media is in the following order: W + M + F > W + E + F > W + P + F(W = water; M = methanol; E = ethanol; P = n-propanol). A probable mechanism has been suggested. It appears that the active site is formed on MMA which abstracts an H-atom from the nylon 6 backbone, giving rise to graft of MMA by mutual combination.

Dehydrochlorination of Poly(vinyl Chloride) in Pyridine. II. Characterization of Dehydrochlorinated PVC

Abstract The structural changes in PVC during thermal dehydrochlorination in pyridine have been investigated. From gel permeation chromatography analyses, chain scission and cross-linking reactions were observed. Cross-linking increased with an increase in reaction time and temperature, whereas the chain scission increased with dilution of the reaction solution. Infrared spectros-copy indicated the presence of conjugated double bond sequences in polymeric chains. Polyene sequences were analyzed by ultraviolet spectroscopy. The length of the polyene sequences and the total number of conjugated double bonds increased with reaction time. An increase in dehydrochlorination temperature lowered the fraction of long polyene sequences, and thus the discoloration. Dilution of the reaction solution decreased the polyene sequence lengths as well as the total number of conjugated double bonds. Shorter polyenes were maximum and their proportion decreased with increase in their length.

Grafting Vinyl Monomers onto Nylon 6 Fiber. III. Graft Copolymerization of Vinyl Monomers onto Nylon 6 Fiber in Water Medium in the Presence of Fructose

Abstract Nylon 6 fiber was grafted with various vinyl monomers e.g., methyl methacrylate (MMA), ethyl methacrylate (EMA), and n-butyl methacrylate (n-BMA), in water in the presence of fructose using a carbon arc lamp as the source of photoirradiation at 70°C and a liquor ratio of 1:26. The effects of various parameters, e.g., monomer concentration, time of grafting, and fructose concentration on grafting reactions, were studied individually for each monomer. The graft yield is greatly enhanced by increasing the monomer concentration and the time of grafting. However, the optimum fructose concentration is required for maximum grafting efficiency. The accelerating action of photopolymerization by fructose was attributed to the sensitizing action of fructose involving an energy transfer.

HALOGENATION OF ATACTIC POLYPROPYLENE

2 Introduction 3 Procedure 4 Conditions 4 Appearance 4 Characterization 4 Glass Transition Temperature (Tg) 6 Polymer Melting Temperature (PMT) 8 Thermogravimetric Studies 9 Flammability Characteristics 11 Electrical Properties 12 Application 13 PVC Plasticization 14 Coating 15 Conclusion 16 References 17 VoL 10, Nos. 1-3,1991 Halogenation of Atactic Polypropylene

Thermal studies on chlorinated atactic polypropylene

Abstract Thermal behavior of chlorinated atactic polypropylene (CAPP) obtained by thermal chlorination of atactic polypropylene was evaluated by thermogravimetric analysis and differential thermal analysis (DTA). It was found that the initial decomposition temperature, integral procedural decomposition temperature, activation energy, and char yield increase with an increase in chlorine content. The thermal stability of CAPP was found to be lower in air than in nitrogen. This has been ascribed to thermooxidative degradation in air. DTA study shows that onset decomposition temperature, glass transition temperature, and polymer melting temperature increase with increasing degree of chlorination. The possible reasons for the phenomena are discussed.

Dehydrochlorination of Poly(viny1 Chloride) in Pyridine. III. Thermal and Mechanical Properties

Abstract The thermal properties of dehydrochlorinated PVC (DHPVC) were evaluated. From thermogravimetric analysis (TGA) and differential thermal analysis (DTA), a larger decrease in thermal stability of dehydrochlorinated PVC than of PVC was observed. Thermal stability of DHPVC increased continuously with an increase in dehydrochlorination temperature and dilution of the reaction solution during dehydrochlorination. However, with an increase in dehydrochlorination time, an increase in thermal stability after an initial drop was obtained. The highly cross-linked product separated from the reaction solution at higher dehydrochlorination temperatures showed a lower thermal stability than that of corresponding soluble DHPVC. The stress-strain behavior of dehydrochlorinated PVC samples was also studied.