Design and characterisation of microfibrillar reinforced composite materials based on PET/PA12 blends

Abstract

Microfibrillar reinforced composites (MFCs) have been prepared by reactive melt-extrusion of poly(ethylene terephthalate) (PET) and polyamide 12 (PA12) in the presence of a catalyst. These composites have been generated by a series of processes, which include reactive extrusion in a mini twin-screw extruder, followed by drawing (fibrillation) and finally the isotropisation of the lower-melting PA12 phase. During the preparation of MFCs additional condensation and transreactions occur at high temperature at the interface between PET and PA12 which leads to the formation of a copolymer layer at the blend interface playing the role of an in situ compatibiliser for the composite system. These composites have been investigated by differential scanning calorimetry (DSC), X-ray diffraction, scanning electron microscopy (SEM) and static and dynamic mechanical testing. The melting and crystallisation behaviour could be understood from DSC analysis. Wide-angle X-ray diffraction measurements have been made use of to characterise the orientation and crystallisation of the blends upon the drawing and isotropisation processes. The microstructure of MFCs, as revealed by SEM, showed fine fibrils of the PET phase in the matrix of PA12. Finally, the static and dynamic mechanical properties of the blends have been evaluated. The MFCs showed excellent ultimate mechanical properties.