Cellular Polymers

Introducing glass fibre to polyurethane foams increases the foam stiffness without raising the isocyanate content. This allows glass fibre reinforced polyurethane foams to be used in structural applications. Glass fibre reinforced polyurethane foams can be manufactured on a large scale using a chopper gun spray system. The glass fibre is commonly supplied as a roving (long strands of fibre wound into a spool) and the chopper gun breaks the roving into equal length pieces, which delivers a stream of glass fibre at a constant mass flow rate. Residual natural fibre is cost-effective, abundant and renewable making it an ideal candidate to replace non-renewable glass fibre in reinforcing polyurethane foam. However, residual natural fibre are often supplied as loose tufts and require multiple steps to be made into roving. In this study, a novel concept was developed that can meter natural fibre at a constant mass flow rate. The concept has the potential for developing natural fibre reinforced polyurethane foams on a large scale, with uniform fibre dispersion and high fibre volume fractions. The concept is verified through mathematical simulations and a prototype.

Alkali-treated wood fibre-reinforced polyurethane (PU) foams were fabricated with a free-rising foaming process. The surface chemistry of alkali-treated wood fibres was characterized using in situ Fourier transform infrared spectroscopy (FTIR), and the fibre surface morphology was explored using scanning electron microscopy (SEM). X-ray computed tomography (CT) was performed to observe the cell structure of foams incorporating the treated wood fibres. Compression tests were conducted and the influence of treated fibres on the compressive strength and modulus of PU foam was investigated. The foams reinforced with treated fibres exhibited increase of 40% in strength and 64% in modulus. The high surface roughness and high aspect ratio of the treated fibres contributed to these improved mechanical properties through enhanced interfacial bond strengths.