Mechanical properties of poly(vinyl chloride) filled with pitch-based carbon short fibers

Abstract

XPS data showed that pitch-based carbon short fibers (PCF) were more reactive than graphite short fibers (PGF) to both silane and titanate coupling agents, although the O1s contents for PCFs were lower than those for PGFs. Dynamic mechanical measurement, flexural tests, and SEM observation for poly(vinyl chloride) (PVC) filled with PCF in the range of 0-100 phr (0-0.450 in volume fractions (Øf)), and those treated with coupling agents by 40 phr (Øf= 0.246)), were carried out. During the blending with a hot mixing roll, the PCF particles in the specimens were broken to the aspect ratio of 2.6-2.9, but they were aligned parallel to the machine direction (MD). As the Øf increased, the storage modulus (E') and flexural modulus (Ef) of the specimens became higher. The E' values of the specimens were larger than those estimated from the rule of mixtures and the modified Halpin-Tsai equation in the glassy region and that calculated from Mooney's equation in the pseudo-rubbery region. The flexural strength for MD was larger than that of PVC, but that for transverse to the MD (TD) was decreased as the Øf increased. The increase in affinity between PVC and PCF particles treated with coupling agents was larger than that of affinity between PVC and PGF.