Silica filled ethylene propylene diene monomer rubber (EPDM) with bis (3-triethoxysilylpropyl) tetrasulfide (TESPT) were mixed in an internal mixer ripened at 23 ± 2℃ and 50 ± 5% RH for several hours. The reaction of TESPT with silanol groups on the silica surface during ripening was pursued on the basis of ²⁹Si-CP/MAS solid state NMR spectroscopy in conjunction with the amount of ethanol released from unvulcanized rubber. The dispersion of silica was evaluated by a nonlinear effect at a small strain, called Payne effect, through dynamic mechanical analysis. The silica dispersion in the compound mixed at a lower temperature was improved during ripening, in which the reaction proceeded. On the other hand, for the mixture prepared at a higher temperature, unreacted silica particles were aggregated upon ripening. Mooney viscosity (ML₁₊₄) of the unvulcanized compound containing TESPT increased during ripening, regardless of the mixing temperature. The vulcanized rubber prepared after ripening exhibited a better dispersion of silica, leading to a decrease in hardness and an increase in reinforcement. The physical properties would be better with a higher mixing temperature and a longer ripening time.

A novel CFRTP made from fabric sheets woven from covering composite yarns consisting of carbon fibers and resin yarns was developed in this study. The developed CFRTP was expected to have high strength because the resin easily impregnates into the clearance between carbon fibers due to the fact that the carbon fibers and resin yarns are closely located in the composite yarn. By evaluating the influence of molding conditions on the internal state of the produced CFRTP, optimum molding conditions for the highest strength were determined. First, by evaluating the void fraction in the range of 230 to 250℃, the optimum molding temperature was determined to be 230℃. Next, by evaluating the impregnation ratio, the optimum molding time and pressure were determined to be 15 minutes and 3 MPa, respectively. The impregnation ratio of resin in the produced CFRTP was sufficiently high, almost 100%. And then the relationship between cooling time in the molding process and bending strength of the produced CFRTP was investigated. The bending strength was evaluated by three-point bending test. The results showed that the bending strength of CFRTP was higher when the cooling time was longer. When the cooling time was shorter, the resin was easily shrunk by heat, resulting in the peeling of resin from carbon fibers. The bending strength of CFRTP produced under the best condition was 683 MPa, which is similar to the strength achieved by conventional methods such as film-stacking and the prepreg method. The study showed that the produced CFRTP had sufficient high strength without taking spreading and pre-impregnation processes, and therefore the proposed method for the novel CFRTP was promising.