Traditionally, calcium carbonate is used as a filler in foam industries and studies have shown that egg-shell contains about 94 % calcium carbonate. The effect of egg-shell in flexible polyurethane foam was studied in this work. Foam with no filler was produced as a control. The egg-shell was beneficiated, characterized and used as filler in flexible polyurethane foam production with varying loads from 5w% to 15 w% at 2.5 w% interval. The effect of various particle sizes on the egg-shell was also studied. Conventional calcium carbonate was also used and the result compared against the produced egg-shell filled foam samples. The produced samples were characterized for compression set, indentation hardness, elongation at break, tensile strength, heat ageing elongation and tensile strength, support factor and density. Scanning electron microscopy (SEM) was also used to study the foam‟s morphology. The result of beneficiation showed that the amount of CaCO3 increased by 1.355 % after beneficiating the egg-shell. The results indicated that 45 µm particle size egg-shell was better in most of the properties than other particle sizes tested, with values closest to the control. The highest elongation, tensile strength before and after heat ageing were obtained at 5 wt% of egg-shell. The results also showed that the egg-shell filled foams at 63 µm particle size and 5 wt% loading for tensile strength and elongation before and after heat ageing tests were higher than calcium carbonate filled foam by 1.04 %, 2.66 kN/m2, 0.82 % and 2.22 kN/m2, respectively. In all cases, the density increase with increase in filler loading and particle size. The SEM analysis showed that cell openings of the produced filled foams decreased as particle size and filler content were increased.
A brief review of the research work is given in this chapter.
1.1 Background of the Study
Solid foam is formed when gas is blown through solidifying plastic. Depending on its ability to retain original shape after compression, it can be classified as either flexible or rigid, Isa etal.,(2012). The foam can either be closed or open cell foams. In closed cell foams, the foam cellsare isolated from each other while the open cell foams are made up of broken cell walls, Babalola and Dominic, (2012).
Flexible polyurethane (PU) foam is one of the major productions from urethane material. Flexible polyurethane foams are used as cushioning material for automotive seat, mattress, furniture, and in packaging etc. According to Klempner and Sendijarevic (2004), flexible polyurethane material has become such widely usedbecause of its excellent light weight, strength to weight ratio performance and the most important is, it offers degree of comfort, protection and utility not matched by other single materials. This usefulness prompts the increase in the prices of polyurethane products consistently over the years which in turn necessitated the incorporation of variety of fillers into foam samples.
Also, the prices of flexible polyurethane foams are becoming increasingly high due to the high cost of raw materials (Onuegbuet al., 2010). The raw materials are mostly liquid reagents and chemicals obtained from petrochemicals and agro-products. The raw materials needed for the production of flexible polyether foam include polyol poly isocyanate, blowing agents, catalysts surfactants and additive such as fillers (Onuegbuet al., 2005).