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, M_c 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 M_c. 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.