Chlorination Of Cis-Polybutadient And The Thermal Reversible Covalent Crosslinking Of Polymers Containing Chlorine

The first goal of this paper was to found the mechanism and to obtain optimal conditions of chlorination reaction, in which t-butyl hypochlorite was used as chlorinating agent and organic acid was used as catalyst. The effects of different factors, such as the kinds of organic acid, the mol ratio of acid to t-butyl hypochlorite, the feeding method of reactant, free-radical inhibitor, reaction temperature and reaction time etc. on chlorination efficiency, chlorine content and gel content were investigated in detail. The ionic reaction mechanism of chlorination was proved by Infrared spectra (IR), proton nuclear magnetic resonance (NMR) and chemical analysis. The active chlorine atoms were introduced in the chlorinated cis-polybutadiene(CBR) through a strong organic acid containing active chlorine. And then, thermal reversible covalent crosslinking reaction behaviors of potassium salt of dicyclopentadiene acid(DCPD(COOK)₂) with acrylic rubber (ACM) or CBR both containing active chlorine were studied. The main results or conclusions were as follows.1. The chlorination of cis-polybutadien(BR) was easily carried outwhen formic acid, chloroacetic acid and t-butyl hypochlorite were used as a compound chlorination agent, which was a good method to chlorinate diolefinic rubber with high efficiency, low gel content. The ionic reaction mechanism and equation were presented on the basis of the rusults of chemical analysis and measurement of IR and NMR.2. The result also showed that chloroacetic acid was not only a chlorinating catalyst but also a kind of important chlorination agent, which can provide thermal reversible covalent crosslinking with an active site.3. Both chlorination efficiency and chlorination yield were more than 90 percent and gel content was below 4 percent when the chlorination was carried out at 65 °C, 40⁵0minutes.4. The heat stability of CBR was studied with thermogravimetric analysis, which was improved by adding sodium carbonate and a kind of compound stabilizing agent. Glass transition temperature, determined by differential scanning calorimetry(DSC), showed that CBR can be used as polar elastomer. Mechanical properties of CBR were improved greatly by compared with that of BR.5. The extruding reaction behaviours of the composites of ACM containing active chlorine, DCPD(COOK)2 and white carbon black were studied; and the products with good appearance and good mechanical properties were obtained and could be re-extruded successfully at 190°C. This result showed that the crosslinking reaction was thermally reversible and its molding and vulcanization can be carried out at the same process; its heat resistance matched to that of ACM by general...