The Study of Properties of Natural Pigments for Mixing with Natural Rubber

Abstract

The purposes of this study were to: 1) study the physical properties of natural pigments for mixing with natural rubber, 2) study the mechanical properties of natural rubber mixed with natural pigments, and 3) compare the physical properties and the mechanical properties between natural and synthetic pigments. The researcher obtained natural pigments from turmeric, basil, and vegetable wastes, i.e. tea and green tea wastes and coffee grounds. The pigments were prepared in the micronized particles and their physical properties, i.e. color, pH, and density  were studied. Also, the effect of natural pigments and commercial synthetic pigments on the mechanical properties, i.e. tensile strength, elongation at break, and hardness of natural rubber (NR) vulcanizates were investigated.

The results show that natural pigments including, turmeric, basil, tea and green tea wastes, and coffee grounds gave color shades of yellow, dark green, cedar, pale green, and pecan respectively. Moreover, the pH of the natural pigments about 5.5 to 7 were observed and they were close to the pH value of NR resulted in good compatibility with vulcanized NR. Also, it was found that the natural pigments gave lower density than the commercial synthetic pigments. Furthermore, the NR vulcanizates mixed with natural pigments showed tensile strength, elongation at break and hardness close to the properties of NR vulcanizates mixed with commercial synthetic pigments. In addition, both mechanical and physical properties of NR  vulcanizates mixed with natural pigments were a little bit less than those mixed with commercial synthetic pigments meaning that natural pigments can be mixed with NR replacing synthetic pigments.