Silica-reinforced natural rubber processed in two routes, with and without mastication. A conventional route begins by mixing dry rubber, silica particles, and additives by high-intensity processes, which masticate polymer chains. A new solution-based process begins with dissolving latex particles into rubber chains in toluene. The solution is mixed with silica particles by low-intensity mixing, which retains long chains. Credit: Harvard John A. Paulson School of Engineering and Applied Sciences

Natural rubber, tapped from trees as latex, is the world's most widely used bio-elastomer.…