Production of PP Composites Reinforced with Flax and Hemp Woven Mesh Fabrics via Compression Molding

Abstract

Hemp and flax fibers are among the most interesting vegetable fibers that can be used to reinforce polymeric matrices. In line with the global environmental requests, the use of these fibers especially coupled with thermoforming polymers are increasing more and more in order to expand their applications and replace synthetic fibers and thermosetting plastics. However, one of the major limitations of vegetable fibers is their poor adhesion with polymeric matrices that is often overcome by fibers chemical treatments or by using coupling agents within the matrix. Aiming to produce polypropylene (PP) bio composite laminates reinforced by hemp and flax fibers without additional process steps, this paper deals on the study of their production via the compression molding technique by using woven fabrics characterized by a large mesh size able to ensure a mechanical anchoring between fibers and matrix. Two different forming strategies that differ in the time required for reaching the maximum values of compression pressure and in the dwelling time at this value were used in order to investigate how the yarn impregnation was affected by them. To expand the applications of composites under investigation, tensile, bending, Izod, heat deflection temperature (HDT) and bearing tests were carried out. The results highlighted how the use of a waiting time before the reaching of the maximum moulding pressure allowed a better matrix flow within the vegetable yarn leading to higher mechanical performances.

Vacuum formed bio‐based composite materials using polyolefin and thermally modified wood powder

“…43 Otherwise compression molding is the natural choice for thermoforming composites and other heterogeneous polymer-based systems. [44][45][46]…”

“…Normally vacuum forming is performed on “single‐component” polymers, although the technique has also been applied on sandwich structures 43 . Otherwise compression molding is the natural choice for thermoforming composites and other heterogeneous polymer‐based systems 44–46 …”

A review on engineering biocomposites and natural fiber-reinforced materials

“…Due to their higher mechanical performance, flax fibers are mostly combined with glass fibers [55] or carbon fibers [56]. However, they can also be combined with other natural fibers, including hemp fibers [57,58], to preserve their recyclabil-ity and to be able to classify them as biocomposites [38]. However, hemp fibers are not as strong as flax fibers, and because of this, the most used synthetic fiber for hybrid hemp fiber composites is glass fibers [26,59].…”

Mechanical and thermal properties of recycled polyethylene/surface treated hemp fiber bio‐composites

“…In these studies, mostly mechanical properties such as impact, shear stress, and tensile stress was analyzed and investigate with the different binders. 15,16 The studies of various binders has been reported such as biodegradable polymers, 17 polyethylene, 18 epoxies, 19,20 polypropylene, [21][22][23] polybutylene adipate-co-terephthalate, 24 polyamide PA 11, 25 and so forth. In most of the studies, different compatibilizers and plasticizers were used to improve the mechanical properties of binders.…”