Resizing Approach to Increase the Viability of Recycled Fibre-Reinforced Composites

Abstract

Most recycling methods remove the essential sizing from reinforcing fibres, and many studies indicate the importance of applying sizing on recycled fibres, a process we will denote here as resizing. Recycled fibres are not continuous, which dissociates their sizing and composite lay-up processes from virgin fibres. In this study, commercial polypropylene and polyurethane-based sizing formulations with an aminosilane coupling agent were used to resize recycled glass and carbon fibres. The impact of sizing concentration and batch process variables on the tensile properties of fibre-reinforced polypropylene and polyamide composites were investigated. Resized fibres were characterized with thermal analysis, infrared spectroscopy and electron microscopy, and the tensile properties of the composites were analysed to confirm the achievable level of performance. For glass fibres, an optimal mass fraction of sizing on the fibres was found, as an excess amount of film former has a plasticising effect. For recycled carbon fibres, the sizing had little effect on the mechanical properties but led to significant improvement of handling and post-processing properties. A comparison between experimental results and theoretical prediction using the Halpin-Tsai model showed up to 81% reinforcing efficiency for glass fibres and up to 74% for carbon fibres.

Evaluation of Mechanical Properties and Pyrolysis Products of Carbon Fibers Recycled by Microwave Pyrolysis

“…In addition, the use of CFRPs as vehicle materials has greatly increased the necessity of developing a recycling technology. 12 Therefore, it is imperative to recycle CFs.…”

“…Only short CFs can be obtained by the mechanical method, and their mechanical properties are severely damaged after grinding and shearing. 12 In the chemical method, the cross-linked bonds in the resin are broken by solvent and heat and the resin is decomposed into low-molecular-weight polymers or small organic molecules and dissolved in the solvent, thereby separating CFs from the resin matrix. CFs recycled by chemical method can retain a tensile strength of 80% and up to 99% under extreme conditions.…”

“…In addition, toxic substances will cause water pollution when they are transferred into the water. , Consequently, most developed countries have started to legally prohibit the landfill disposal of CFRPs. In addition, the use of CFRPs as vehicle materials has greatly increased the necessity of developing a recycling technology . Therefore, it is imperative to recycle CFs.…”

“…Generally, the main recycling methods of CFs include mechanical, − chemical, − and thermal methods. − In the mechanical method, CFRP waste is crushed into particles or milled into powder, which can be directly used as a filler. Only short CFs can be obtained by the mechanical method, and their mechanical properties are severely damaged after grinding and shearing . In the chemical method, the cross-linked bonds in the resin are broken by solvent and heat and the resin is decomposed into low-molecular-weight polymers or small organic molecules and dissolved in the solvent, thereby separating CFs from the resin matrix.…”

Influence of Shelf Life on Mechanical Properties of Glass Fibre Reinforced Composites

“…In this case study was mentioned that the problems with older epoxy aren't related to the material's age but to the presence of contamination like moisture, hardener-resin cross contamination, dirt or contact with other chemicals. Other studies are available regarding the durability of epoxy resin and fibre composites after immersion in different fluids [27] or regarding the feasibility of using recyclable epoxy resin and recovered glass fibres for manufacturing recycled thermoset composites [28,29].…”