Surface characterisation of chlorinated unvulcanised natural rubber latex films

Natural rubber (NR) latex film chlorinated by chlorine gas generated in sit u from acidified hypochlorite solution at room temperature was characterise d by FTIR-ATR, SEM-EDX and contact angle techniques. Chlorinated and oxygen ated structures were found on the him surface after chlorination. The level of surface chlorination increased with chlorination duration and chlorine dosage. The hydrophilicity of the surface improved after chlorination. Howe ver, cracking of the surface was noted and the surface mean roughness, R-a of the chlorinated surface increased with extent of chlorination. The thick ness of the chlorinated layer on the NR latex him was found to be less than 10 mu m. Severe cracking of the film surface at high chlorine dosage and e xtended reaction time was evident. Surface roughening and hardening both wo uld result in a reduction in the adhesive friction of the chlorinated surfa ce against a substrate. Chlorination accelerated the oxidative chain scissi on of the rubber molecules, especially at elevated temperature, with the at tendant introduction of conjugated C = C double bonds into and increase in number and concentration of oxygenated structures of the rubber molecules. Discoloration and poor heat resistance properties of chlorinated NR latex f ilm are perhaps the results of these effects. (C) 1999 Elsevier Science Ltd . All rights reserved.