Commingled natural fibre/polypropylene wrap spun yarns for structured thermoplastic composites

A major challenge for natural fibre composites is to achieve high mechanical performance at a competitive price. Composites constructed from yarns perform better than composites made from random nonwoven mats. However, the twist structure of conventional ring spun yarns prevents the full utilization of fibre mechanical properties in the final composites. We produced flax/polypropylene commingled wrap yarns in which all flax fibres were twistless. Composites made from the wrap yarn demonstrated significant improvement of flexural modulus. Most currently available low cost natural fibres, such as decorticated hemp, cannot be efficiently made into yarns because of their lack of cohesion. Adding polypropylene fibres to decorticated hemp improved textile processing performance. The polypropylene fibres served as a carrier for the natural fibres during processing and became the polymer matrix in the final composites.