Rotational Shear-Induced PS Microfibers Enable Interfacial Strengthening in High-Strength, Thermally Enhanced PS/PB-1 Composite Pipes

This study presents a method for fabricating polybutene-1 (PB-1)/polystyrene (PS) composite pipes with an in situ microfibrillar morphology and a strengthened interphase featuring surface-induced, oriented PB-1 lamellae. Under a rotating shear field, the dispersed PS phase is stretched into high-aspect-ratio microfibers within the PB-1 matrix, and PB-1 lamellae grow from the microfiber surface with a preferential orientation (mainly perpendicular to the microfiber axis). SEM imaging directly shows the PS microfibers and the surface-grown PB-1 lamellae, while XRD results confirm enhanced lamellar orientation and crystallinity along the shear direction. As a weakly polar, amorphous phase, PS exhibits good interfacial compatibility with PB-1. During cooling-induced crystallization, the mismatch in volumetric shrinkage between the two phases, together with this favorable compatibility, leads to compressive interlocking at the interface, enhancing stress transfer and interfacial bonding. At an optimal mandrel speed of 8 rpm, the composite exhibits a crystallinity of 65%, a melting point of 133.6 °C, and a hoop tensile strength of 41.22 MPa, increasing from 13.68 MPa at 0 rpm. In addition, the Vicat softening temperature increases to 115.4 °C, and thermal conductivity is also improved. These results show that combining in situ microfibrillation, interfacial mechanical interlocking, and surface-induced oriented lamellar growth can improve both the mechanical and thermal performance of PB-1-based pipes.