To determine the gel content in natural rubber, 0.2–0.3 g of the rubber
pieces were soaked in an excess of toluene for 24 h. The solution
was filtered through a 120 lm Nylon net filter disc (Millipore, Billerica,
MA). The weight of the dried material remaining on the filter,
considered as gel, was calculated on the basis of the total original
rubber weight.