Effect of die structure on the properties of self-reinforced polypropylene/noil ramie fiber composites prepared by solid-state extrusion

Abstract

In this work, the self-reinforced polypropylene (PP)/noil ramie fiber (NRF) composites were prepared by the solid-state extrusion method. And the effect of die structure such as draw ratio and conical angle on the morphology, thermal and mechanical properties of samples was investigated. The results indicated that the solid-state deformation of PP/NRF composites conducted below the melt transition promoted the formation of the orderly arranged microfibrils inside the samples, which arranged along the extrusion direction and could be observed by scanning electron microscopy (SEM). Besides, the increased draw ratio and conical angle both contributed to the higher degree of orientation, which was obvious observed inside the sample prepared at the draw ratio of 5 and conical angle of 20°. The thermal properties tested by differential scanning calorimetry (DSC) also suggested that the intensified orientation of microfibrillar structure not only demonstrated the transformation of the spherulitic crystal into the aligned chain crystals, but also resulted in the enhanced crystallinity and narrowed melting peak. Moreover, the highly oriented fibrillar bundle structure endowed the samples with the excellent tensile strength and flexural strength, which were up to 80.9 MPa and 83.5 MPa respectively and increased by 182.8% and 102.7% compared with the commonly extruded samples.