Mechanical properties of cuttlebone reinforced natural rubber composites

Abstract

Cuttlebone is an important biomass which can be incorporated in natural rubber (NR) as a reinforcing filler. The main composition in cuttlebone particles was inorganic calcium carbonate (CaCO₃) about 89 – 94 % and the remained contents were protein (3 - 7 %) and chitin (3 - 4 %). The obtained chitin extracted from cuttlebone had been characterized by fourier transform infrared spectroscopy (FTIR). The results indicated that the characteristic absorption peaks were corresponding to the chemical structure of chitin in β-form. The composites were prepared via three kinds of sulfur vulcanizations, i.e., conventional vulcanization (CV), semi-efficiency vulcanization (semi-EV) and efficiency vulcanization (EV) systems. From the results of cure characteristics, the scorch time and cure time of NR compounding trended to be decreased with increasing filler loading. The mechanical properties of NR composites via three kinds of sulfur vulcanizations were improved by addition of cuttlebone particles and the mechanical properties were found to be comparable with those of the NR filled with commercial CaCO₃. However, the CaCO₃ did not improve the tear and abrasion resistances of the NR composites. When the NR composites were subjected to thermal aging, it was found that the incorporation of the CaCO₃ filler could improve the thermal stability of composite materials, compared with NR vulcanizate without the reinforcing filler. Nevertheless, the incorporation of CaCO₃ filler could not prevent the surface cracking caused by ozone. Dynamic mechanical properties of cuttlebone particles filled NR vulcanizates were comparable with those of the commercial CaCO₃ filled ones. In addition, the presence of organic component such as chitin was affected to give a good rubber-filler interaction of cuttlebone particles to NR matrix as supported by scanning electron microscopy (SEM).