Polypropylene/acrylonitrile-styrene copolymer (PP/SAN

98/2

96/4

94/6 and 92/8) blend parts were molded via water-assisted injection molding (WAIM) at different water pressures and melt temperatures.The crystal and phase morphologies of the WAIM PP/SAN blend parts were studied by means of polarized optical microscopy (POM) and scanning electron microscopy (SEM).The results showed that the high shear stress and cooling rate occurring during the high-pressure water penetration in the WAIM process could cause the in situ fibrillation of the SAN droplet

followed by the formation of transcrystalline structures at the interface of PP matrix and SAN fiber.For the WAIM 96/4 PP/SAN blend part

increasing the water pressure and lowering the melt temperature were found to be favorable for the formation of transcrystalline structures through increasing the shear stress and relaxation time of PP matrix

respectively.Moreover

it was found that no transcrystalline structures could form at a low SAN content

e.g.

2 wt%.