The effects of filler loading on the curing characteristics,swelling behavior,and mecanical properties of natural rubber compounds were studied using a conventional vulcanization system.Recycle rubber powder (RRP),carbon black (CB) (N550),and calcium carbonate (CaCO_3)were used as fillers and the loading range was from 0 to 50phr.Results show that the scorch time ,t_2,and cure time,t_(90),decrease with increase in filler loading.At a similar filler loading,RRP shows shortest t_2 and t_(90) followed by CB and calcium carbonate.The tensile strength,tensile modulus,and hardness increase with increase in CB loading,where as elongation at break,resilience,and swelling properties show opposite trend.For RRP and calcium carbonate filled natural rubber compounds,the tensile strnegth increases up to 10 phr and starts to deteriorate at higher filler loading.The other properties such as tensile modulus,hardness,elongation at break,resilience,and swelling percentage show a small change with increase in RRP and calcium carbonate loading in natural rubber compounds where improved mechanical properties are not critical.
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