Effects of Drying Temperature on the Properties of Deproteinized Natural Rubber Latex/starch Composite Films

The aim of this study was to observe the effects of drying temperature on the properties of deproteinized natural rubber latex (DNRL)/starch composite films. These composite films were prepared by simple mixing and then drying at different temperatures of 50, 60 and 70 C. Various parameters such as types (potato, sago, bean, corn, tapioca, rice, and glutinous starches), amounts (5-20 part per hundred of rubber (phr)) and water-dispersed concentrations (5-50%) of starch blended were evaluated. It was found that only some DNRL/starch composite formulations could be prepared as the completely homogeneous films. Drying temperature affected the degree of starch gelatinization that confirmed by differential scanning calorimeter (DSC) technique. The DNRL composite films of 20 phr of all 7 starch types could be formed at 50 and 60 C, while those of 20 phr sago, bean, corn, and rice starch could be formed at 70 C. Some of these films were difficult to be the completely dry films at 70 C due to their more degree of gelatinization of starch on the surface films which inhibited the evaporation of water inside the films. However, only some DNRL/starch composites showed the homogeneous film under cross-section scanning electron microscopy (SEM) observations. Their compatibilities were confirmed by Fourier transform infrared spectroscopy (FT-IR) and DSC. Their physical and mechanical properties were further evaluated by the universal testing machine.