In order to further investigate shear-induced
interfacial crystallization of polymer-based composites, an
improved fiber-pulling device was designed and built. Its
peculiar characteristic is that a force transducer is assembled
to in situ monitor the variation of interfacial shear stress
between the polymer matrix and pulling fiber. Thus, the
relationship between interfacial shear stress and the subsequent
crystalline morphology can be quantitatively
established. In the preliminary study via this device, isotactic
polypropylene (iPP)/glass fiber composite was adopted as a
model system. The results indicate that interfacial crystallization
kinetics is promoted by the presence of interfacial
shear stress. Furthermore, there are two thresholds of interfacial
shear stress for interfacial crystalline morphology. To
be specific, one (0.017 MPa) is for the induction of iPP
nucleation, above which a-form iPP crystals are obviously
encouraged during the subsequent isothermal crystallization;
the other is for the generation of b-form iPP crystals
(0.042 MPa), above which b-form crystals are favored to be
triggered in the transcrystalline region.