In the molding of the carbon fiber reinforced thermoplastic (CFRTP), impregnation of the carbon fiber (CF) bundle is one of the important issues. In this study, we discussed the influence of the melting viscosity of matrix polycarbonate (PC) resin into the CF fabric substrate on the impregnation behavior, and also discussed the influence of the viscosity of the PC and molding time on the formation mechanism of the void. The CF/PC composites were prepared by using the CF plain fabric and PC film using film stacking method by changing the molding temperature and the molding time. According to the photograph of CF/PC surface, the PC resin into the CF bundle flowed in the chink of the CF bundle and crossing point of CF fabrics. The voids were formed by the PC resin impregnated as surrounding the aggregateofCF.Thesizeofvoids becomes smaller by impregnation of the PC resin into inside of the aggregate of CF. Therefore, when the matrix viscosity of PC is low, resin is easy to flow and the size of voids is easy to become smaller.

Aqueous methylcellulose (MC) forms hydrogel upon heating and the gel dissolves upon cooling i.e. thermo-reversible gelation. However, the values of the gelation temperature differ depending on the sources of MC samples and on the methods of determination as well. In this study, we have obtained a lower limit of the gelation temperature for a specific MC below which aqueous MC does not form the gel, by dually extrapolating the holding time for gelation to infinite and the mechanical probing force to zero. The gelation temperature obtained in this manner decreased with increasing concentration of the MC; to cite a case, it was located at ca. 21 ̊C for 10 wt%, which is ca. 10 ̊C lower than a conditional value estimated after holding 1 h without these dual extrapolations.

Carbon fiber reinforced thermoplastic (CFRTP) is expected to be useful in the automobile applications because CFRTP has some excellent aspects such as relatively light weight, high strength,easiness of recycling etc. Mechanical properties of the CFRTP depend on the impregnation state of the matrix resin into the carbon fiber (CF) bundles. In this study, we discussed the influence of the melting viscosity of the matrix polycarbonate (PC) resin at impregnation time on impregnation state of PC into CF bundles, and also discussed the effect of number and size of void of CF/PC on the flexural properties of the CF/PC. Three kinds of PC with different viscosities were employed as the matrix resin. The CF/PC composites were prepared by heat press molding using the CF plain fabric and PC film using the film stack method. The void fraction of the CF/PC almost linearly decreased with viscosity of PC resin and was independent of the kinds of PC. The flexural strength and modulus of CF/PC increased with decreasing void fraction of the CF/PC. According to the photograph of CF/PC surface, the number of large size of voids in CF/PC decreased with PC viscosity. These results imply that the impregnation of PC matrix into the carbon filaments is improved by using the PC with low viscosity. Then, the matrix viscosity is found to be important characteristics for CFRTP with high performance.