Synthetic Rubber with the Tensile Strength of Natural Rubber

The preparation of synthetic rubber with tensile strength identical to that of natural rubber is a long-standing unsolved problem in chemistry despite extensive related research. Here, we prepare synthetic rubber with tensile strength identical to that of natural rubber as a result of our discovery that natural rubber is a naturally occurring nanocomposite with proteins and lipids. The synthetic rubber is prepared by chemically attaching nanoparticles onto microparticles of synthetic cis-1,4-polyisoprene dispersed in water as a colloidal dispersion, followed by drying to form an "island-nanomatrix structure" similar to that of natural rubber. The stress at break of synthetic cis-1,4-polyisoprene increases dramatically from 0.1 to 3.9 MPa. The cis-1,4-polyisoprene with an island-nanomatrix structure exhibits almost the same mechanical properties as natural rubber. In addition, the synthetic cis-1,4-polyisoprene with an island-nanomatrix structure is vulcanized in the conventional manner using sulfur, zinc oxide, a vulcanization accelerator, and stearic acid at 150 °C and 15 MPa for an optimal vulcanization time after mechanical mixing. The stress at break of the resulting vulcanized cis-1,4-polyisoprene with an island-nanomatrix structure is 35.2 MPa, which is higher than that of vulcanized natural rubber. The preparation of synthetic rubber with mechanical properties identical to those of natural rubber is achieved by the formation of an island-nanomatrix structure in the synthetic rubber and is demonstrated by the mechanical properties of the vulcanized synthetic rubber being identical to those of vulcanized natural rubber.