Linseed Oil Plasticizer Based Natural Rubber/Expandable Graphite Vulcanizates: Synthesis and Characterizations

Natural rubber (NR)/expandable graphite (EG) vulcanizates have been prepared using linseed oil plasticizer. The effects of linseed oil on the cure and mechanical properties of the NR/EG vulcanizates such as cure time, tensile strength, tear strength, modulus, elongation at break and swelling behavior have been studied to evaluate its suitability as plasticizer. Naphthenic oil was used as a reference. The linseed oil vulcanizates showed good processing behavior in terms of torques and scorch. With the incorporation of linseed oil there was improvement in the cure time and the mechanical properties of the EG/NR vulcanizates. 2–4 phr linseed oil in the NR/EG vulcanizates showed maximum tensile strengths. The higher value of cross link density at 4 phr for the linseed oil vulcanizates indicates better reinforcement of the EG–rubber matrix. The NR/EG/linseed oil vulcanizates exhibited higher thermal stability compared to NR/EG vulcanizates. The scanning electron micrographs revealed that incorporation of linseed oil up to 4 phr hinders the crack formation apparently with no major crack present in the NR/EG/LO composites minimizing the failure when compared to similar composites with naphthenic oil. The results indicate that the optimum level of linseed oil in the vulcanizates is 2–4 phr.