Development of bulk moulding compounds and extrusion compounding processes using recycled glass fibres
Topic(s) : Special Sessions
Co-authors :
David Bryce (UNITED KINGDOM), Liu YANG (UNITED KINGDOM), Ramin MORADI , James THOMASON (UNITED KINGDOM)Abstract :
To achieve global carbon neutrality, adoption of renewable energy sources such as wind power can be expected to rise significantly in the coming decades. As demand for wind power increases, so does the significant amount of end-of-life composite blade waste generated during decommissioning. Consequently, developing a cost-effective and environmentally conscious method of recycling large composite structures remains an essential challenge to achieving a circular economy for the global composites industry [1,2]. Fluidised bed recycling involves thermal decomposition of the polymer matrix to liberate clean glass fibres into the gas stream which are subsequently separated and collected. The reclaimed fibres can then be reprocessed into novel composite materials, reducing landfill burden and offsetting emissions associated with virgin material production through replacement.
This paper describes how recycled glass fibres were reclaimed from end-of-life turbine blade material and model recycled glass fibres were used to produce injection moulding pellets and bulk moulding compounds (BMC) at varying ratios of virgin glass fibre replacement. The effect of fibre post-treatment and processing conditions on composite mechanical properties are also reported. It was found that BMC products with mechanical properties acceptable for commercial implementation could be achieved with almost total replacement of virgin fibres (Figure 1a). Applying a polyester-compatible coupling agent had little significant effect on composite mechanical properties (Figure 1b). This is possibly due to any positive benefits of increased adhesion being offset by silane-treated fibres being relatively poorly dispersed. The introduction of an extended mixing period caused the moulding compound to form distinct spherical structures and significantly reduced tensile, flexural, and impact properties were measured.
Recycled glass fibres treated with a silane solution were also extrusion compounded with injection moulding grade polypropylene and a maleic anhydride functionalized homopolypropylene. Silane-treated fibres tended to form entangled mats unsuitable for compounding as shown in Figure 2a. The issue was mitigated by re-chopping treated fibres into bundles before extrusion (Figure 2b) to produce an injection moulding compound with approximately 10% fibre reinforcement. Extrusion compounding at higher levels of reinforcement loading was not possible due to poor material flow in the hopper relative to virgin chopped glass products. This was primarily caused by the low bulk density of recycled glass fibres and the tendency for treated fibres to agglomerate in the hopper. It is concluded that in addition to optimising recycling technologies and fibre post-treatment formulations, suitable manufacturing or fibre preparation techniques must be developed to support the introduction of recycled materials into conventional composite manufacturing processes.
This paper describes how recycled glass fibres were reclaimed from end-of-life turbine blade material and model recycled glass fibres were used to produce injection moulding pellets and bulk moulding compounds (BMC) at varying ratios of virgin glass fibre replacement. The effect of fibre post-treatment and processing conditions on composite mechanical properties are also reported. It was found that BMC products with mechanical properties acceptable for commercial implementation could be achieved with almost total replacement of virgin fibres (Figure 1a). Applying a polyester-compatible coupling agent had little significant effect on composite mechanical properties (Figure 1b). This is possibly due to any positive benefits of increased adhesion being offset by silane-treated fibres being relatively poorly dispersed. The introduction of an extended mixing period caused the moulding compound to form distinct spherical structures and significantly reduced tensile, flexural, and impact properties were measured.
Recycled glass fibres treated with a silane solution were also extrusion compounded with injection moulding grade polypropylene and a maleic anhydride functionalized homopolypropylene. Silane-treated fibres tended to form entangled mats unsuitable for compounding as shown in Figure 2a. The issue was mitigated by re-chopping treated fibres into bundles before extrusion (Figure 2b) to produce an injection moulding compound with approximately 10% fibre reinforcement. Extrusion compounding at higher levels of reinforcement loading was not possible due to poor material flow in the hopper relative to virgin chopped glass products. This was primarily caused by the low bulk density of recycled glass fibres and the tendency for treated fibres to agglomerate in the hopper. It is concluded that in addition to optimising recycling technologies and fibre post-treatment formulations, suitable manufacturing or fibre preparation techniques must be developed to support the introduction of recycled materials into conventional composite manufacturing processes.