Manufacturing of hybrid composites based on polypropylene matrix

Abstract

Composites are becoming widely popular in wide range of applications due to their superior properties. Based on the key learnings from number of literatures, this present work aimed to explore potential methodologies to improve and to maximize the performance of recycled PP matrix composites via hybrid reinforcement systems by adapting methods overcome the knowledge gaps and limitations. The novelty of this research was created by the consideration of processibility and cost, the suitable compatibilizer dosage, the maximum filler content and maximum ratio of recycled PP to obtain the acceptable range to the composite in the market. To achieve the best possible combinations, a comprehensive study was carried out to explore the effect of filler types and loading via a number of screening tests. Fillers from both fibre family (i.e., carbon fibre and glass fibre), and particle family (i.e., CaCO3, glass bead, kaolin and Graphene Nanoplatelets (GNPs)) were processed using a twin screw extruder. Firstly, the effect of filler types and loading on mechanical and thermal properties of neat PP composite systems were investigated as a reference result. The filler contents were varied from 10 – 30 % by weight. Mechanical properties such as the tensile modulus, flexural modulus and Izod impact strength were evaluated. For the particle family, PP/glass bead composites had the best overall mechanical properties. Mechanical properties such as tensile, flexural modulus and Izod impact strength showed maximum improvements by 37%, 47% and 6%, respectively compared to neat PP. These PP/glass bead composites were improved with a simple compounding process and with an acceptable cost. Therefore, the most suitable filler from the particle family was the “Glass Bead”. For the fibrous family, PP/glass fibre was selected as the most suitable fillers due to the incorporation of glass fibre could promote the mechanical properties up compared to neat PP more than carbon fibre especially for Izod impact strength. At the second stage, the best performing fillers from each family which were glass fibre and glass bead were used to manufacture hybrid composite systems. These hybrid composite systems were investigated on neat PP resin. Then, thirteen sets of experimental trials were carried out by varying the ratios of glass bead and glass fibre combinations. Based on the experimental results, it can be concluded that PP hybrid composites with 10 wt% of glass bead and 40 wt% of glass fibre and 7.5 wt% of PP-g-MA (HC13) was the most suitable formulation among all of hybrid composite formulations tested. This is considering their superior mechanical properties e.g. tensile, flexural modulus and Izod impact strength with 250%, 330% and 34% improvement respectively compared to the extruded neat PP. Moreover, it was also cheaper and its density and melt flow index were acceptable for injection moulding application in the current market. At the final stage of the project, the selected combination of glass fibre and glass bead reinforcements (HC13) was used to manufacture recycled PP based composites. Composites were manufactured by varying the percentage of recycled PP from 5 to 100 wt% in order to investigate the mechanical properties. In conclusion, the implementation of the formulation HC13 by replacing neat PP with rPP, could be effective since the performance of rPP was demonstrated to be comparable to that of neat PP in term of the mechanical properties. Furthermore, all the test samples were validated through thermal and rheology properties. Fractured surfaces were studied by employing scanning electron microscopes (SEM). These types of hybrid filler systems can be considered as promising reinforcing materials to increase the performance of thermoplastics. Hence, the results achieved in this work with these composite systems should encourage recycled thermoplastics to be applied for high-end applications at a significant rate in the near future.

Date of Award	31 Dec 2021
Original language	English
Awarding Institution	The University of Manchester
Supervisor	Venkata Potluri (Supervisor), Ivan Vera Marun (Supervisor) & Chamil Abeykoon (Supervisor)