Effect of shear on nucleation of carbon fiber reinforced polymer composites: Experiments and modeling

Abstract

AbstractIn this study, shear‐induced crystallization of short carbon fiber (SCF)‐reinforced isotactic polypropylene (iPP) composite was investigated using polarized optical microscopy (POM) and rheometry. Although the SCF exhibited no nucleation ability to iPP in the quiescent melt under the chosen conditions, different interfacial morphologies were observed after shear was applied. The POM results revealed that the crystallite morphologies along the SCF strongly depended on the shear rate () and shear duration. A nucleation kinetics model was proposed to determine how shear affects the fraction of SCF covered with transcrystalline. The nucleation rate on the SCF was proportional to . The dependence of the nucleation rate corresponded well with the change in the shear‐induced free energy of the melt, indicating that the interactions between SCF and iPP were insignificant. The rheological results demonstrated that conformational ordering directly affected the nucleation rate. The helical content near the SCF increased rapidly owing to the enhancement of shear. Therefore, the nucleation kinetics on the SCF surface accelerated significantly.