DEVELOPMENT AND CHARACTERISATION OF BANANA PEDUNCLE FIBRE REINFORCED POLYESTER COMPOSITES USING COW HORN ASH PARTICLES AS FLAME RETARDANT ADDITIVE

1.1Backgroundof the Study

Fibre-reinforced composites are used in a wide range of applications such as automobiles, aircraft, ships, boats, pipelines, sport equipment, storage tanks, etc. The traditionalpolymeric and metallic materials have been replaced successfully by fibre-reinforced composites (Ihueze & Okafor, 2012). This is as a result of their high strength-to-weight ratio, light weight, goodchemical andcorrosion resistance, fatigue resistance and low maintenance requirements. The unique properties achieved depend on the fibre reinforcing material, and the polymer matrix. The fibre reinforcing material is mainly responsible for the strength and stiffness of composites while the polymer matrix material is responsible for the load distribution applied on the fibres and the protection of the fibres from the effect of environmental harm conditions (Okafor, Ihueze & Nwaigbo, 2014)

Generally, the reinforcing materials are high performance fibres such as glass, carbon, Kevlar etc., whereas the matrix material can be either thermoplastic (polyetheretherketone, nylon 6, polystyrene, acrylic, polyester, polyethylene, etc.) or thermoset polymer (unsaturated polyester, phenolics, epoxy, vinyl ester, polyimide, melamine formaldehyde, etc.). Amongst thermoset resins, the unsaturated polyester (UP) is one of the widely used thermoset resin matrix for fiber-reinforced composite, owing to its excellent mechanical properties, good moisture resistance, good corrosion and chemical

resistances (Kandola, Mouritz, Mathys, Sorathia, Ness, Blum, Horrocks &Price, 2018). Despite these advantages, poor flame resistance, the evolution of smoke and emission of styrene during burning of UP based composites are the major limiting factors for applications where fire safety is important(Mouritz & Mathys, 2013). In order to mitigate the high flammability and thermal decomposition of polymers, there is strong need to reduce their flammability (McGeorge & Hoyning, 2014; Grenier, 2015).

The intrinsic flammability property of UP can be altered either by chemical modification of the resin or by adding flame retardant chemicals into it. In the chemical modification of the resin, flame retardant elements such as halogen or phosphorus (Dai, Song, Jiang,Yu, Yang, Richard, Yuen&Hua, 2013) are introduced in the UP resin backbone. The presence of halogen or phosphorus in UP resin significantly improves the flame retardancy of UP, but when it burns the presence of halogen raises environmental issues (Levchik, Piotrowskia, Weilb, Yaob, Walczak & Horold, 2015)

On the other hand, commonly used mineral fillers such as alumina trihydrate (ATH), magnesium hydroxide and calcium carbonate can be used, however to be effective, they are required in high concentration (typically >30 wt.%), which can deleteriously affect the mechanical properties of the composite (Horrocks & Kandola, 2005; Ihueze et al., 2014).

An alternative method to improve the fire resistance of the composites is to coat the surface with ceramic or intumescent coatings. When exposed to heat, the

surface coatings protect the composite by forming a thermally insulative

ceramic layer or intumescent char (Wang, Han & Ke, 2015). However, this method has its own limitations, mainly of additional weight.

Presently, there have been developments in the area of polymer/ nanocomposites, where nanoparticles such as nanoclays and carbon nanotubes are dispersed into a resin matrix to enhance the fire retardancy and mechanical properties of the composites. Nanoclays are used at low loading levels (2-5 wt.%). Even 5 wt. % clay loadings can reduce the peak heat release value by 70 % for polymers such as poly butylene terephthalate, co-polyester elastomer (Kiliaris 2010; Katsoulis & Papaspyrides, 2010). However, the use of nanoparticles dispersed in the uncured Unsaturated Polyester(UP) may cause an increase in resin viscosity and so decrease the ease of processing.

Considering these drawbacks, a different approach to improve the fire retardancy of polymers with biobased fire retardant additives that will be human and environmentally friendly as well as not impact negatively on the engineering properties of the composites is clearly required. With this in mind, UP will be blended with cow horn ash particle to give composites that are green and sustainable with fire retardancy and mechanical properties that will compete favourably with other fire retarded polymer composites as well as address environmental and human health concern.

In the prevention of fire-induced loss of lives and properties, bio-sourced fire retardant additives (cow horn ash particle) will provide a valuable preventive and control measure to reduce the risk of fire initiation, and flash

over. This will become an attractive class of fire retardant material as a result of their human and environmental friendliness, low cost and availability.