Effect of Filler on Physical Properties and Surface Morphology of Natural Rubber Latex Films

The physical properties of unfilled and filled natural rubber latex (NRL) films were investigated. The presence of calcium carbonate in latex films, determined by ash content method that was lower than the amount of filler added to the compound, suggested that the filler tended to sediment. Images obtained from Field Emission Scanning Electron Microscope System (FESEM) on the filled latex film confirmed agglomerates in the latex films especially with higher filler loading and hence, influencing the appearance of the films whereby the dense colour was observed. The stress on the latex films due to the filler was investigated using Mooney Rivlin (C-1) stress-strain relaxation measurement method. The clear difference in the C-1 values obtained from the test sample before and after being stretched indicated possible breaking at the polymer-filler interphase, especially in natural rubber latex films with high filler loading. It was confirmed that the addition of calcium carbonate up to 20 parts per hundred rubber (p.p.h.r) into compounded natural rubber latex produced films with some improvements in strength and stiffness. The improvement in strength, however, ceased and decreased on higher filler content and the elasticity of the film reduced drastically.