Properties of vulcanised concentrated skim natural rubber latex dipped film

Skim latex can be concentrated using an ultrafiltration process. It is a liquid separation process where water can be removed from latex through a membrane. Vulcanised dipped concentrated skim latex (CSK) films were prepared, and their properties were compared to commercial high ammonia natural rubber (HANR)-dipped films. As expected, HANR-dipped films were stronger as seen from the higher tensile and modulus values. However, the highest tensile strength and modulus values for CSK-dipped films stood at 17 MPa and 620%, respectively. Interestingly, the crosslink density of CSK-dipped films was higher than HANR-dipped films while the average molecular weight of rubber between crosslinks, Mc demonstrated the opposite. Both dipped films showed comparable results in oil and water uptakes, with CSK-dipped films having more water-resistance after prolonged immersion time than HANR-dipped films. The maximum decomposition temperature of CSK, i.e., 373.06 oC, and HANR dipped films, i.e., 374.08 oC, were almost identical. Interestingly, the TEM images revealed vulcanised CSK particles formed only intra-particle crosslinks, which agreed with the lower tensile strength, elongation at break (EB), crosslink density, and higher Mc. Overall, the non-rubber components and naturally occurring networks, with the influence of molecular weights, vulcanisation degree, and smaller particles, substantially affected the resulting CSK vulcanised dipped films.