Surface characterisation of chlormated unvulcanised natural rubber latex films

Natural rubber (NR) latex film chlorinated by chlorine gas generated in situ from acidified hypochlorite solution at room temperature was characterised by FTIR-ATR, SEM-EDX and contact angle techniques. Chlorinated and oxygenated structures were found on the film surface after chlorination. The level of surface chlorination increased with chlorination duration and chlorine dosage. The hydrophilicity of the surface improved after chlorination. However, cracking of the surface was noted and the surface mean roughness, R(a) of the chlorinated surface increased with extent of chlorination. The thickness of the chlorinated layer on the NR latex film was found to be less than 10 (mu)-m. Severe cracking of the film surface at high chlorine dosage and extended reaction time was evident. Surface roughening and hardening both would result in a reduction in the adhesive friction of the chlorinated surface against a substrate. Chlorination accelerated the oxidative chain scission of the rubber molecules, especially at elevated temperature, with the attendant introduction of conjugated C = C double bonds into and increase in number and concentration of oxygenated structures of the rubber molecules. Discolo ration and poor heat resistance properties of chlorinated NR latex film are perhaps the results of these effects. © 1999 Elsevier Science Ltd. All rights reserved.