Influence Of The Microinjection Moulding Process On The Crystalline Orientation And Morphology Of Semicrystalline Polymers

摘要

Microinjection moulding ((mu)IM) seems to be a key for the large scale production of polymer microparts. For semicrystalline polymers, the crystallisation under high shear and cooling rates induces specific morphologies and properties and thus takes tremendous importance in microinjection process compared to classical injection moulding (IM) process where wall thicknesses are generally larger than 1mm. Two semicrystalline polymers were microinjected, a high density polyethylene and a polyamide 12 in plaque cavities having thicknesses of 0.3 and 0.5mm. Analyses obtained by optical microscopy show that the crystalline morphologies vary between micro- and macro- parts. While a 'skin-core' morphology is present for the macropart, the (mu)part exhibits a specific morphology. The X-ray scattering at small angles (SAXS) studies show an orientation of HDPE lamellae whatever the conditions of microinjection whereas the orientation of PA12 lamellae is either isotropic or anisotropic depending on the thickness of molded parts.