Increasing demand of energy to fulfill the need of people is also increasing different forms of waste worldwide, such as coal fly ash (CFA). CFA is the byproduct of coal power plant (Mahlaba et al., 2012) and it is estimated that 41% of electricity produced is from coal power plants and predicted that this percentage can be increase to 44% in 2030 (Chávez-Valdez et al., 2011). Fly ash is a useful waste, that is generated after combustion in the power generation plants. it should be utilized as a filler material in different commercial products as well as in rubber industries. In USA, around 750 million tons CFA is produced as waste material but only 39% is used in different products (Kuenzel and Ranjbar, 2019). CFA is also an environmental problem. Dumping of CFA and environmental protection from their effects is also very difficult. The CFA emissions in environment can cause high risk of environmental pollution and pulmonary diseases in humans (Whiteside and Herndon, 2018). Therefore, the reuse of CFA is very important. CFA has good deformability and segregation capacity due to the strong bond, thus it can be used as self-compacting agent in concrete (Siddique and Kaur, 2016). In self-compacting matrix CFA increases the holding bond and flow ability of fresh mortar and make the material solid and strong (Behnia et al., 2017). Fly ash can also be used as pavement material in recyclable concrete (Yoshitake et al., 2016). It also has a potential in rubber industry and can be used as a filler material in rubber products for the strengthening of mechanical properties. Palm based fly ash is suitable for thermoplastic materials to improve mechanical properties of product (Kanking et al., 2012). The main component of fly ash is carbon black (CB), and silica in the form of precipitated silica (Ahmad et al., 2012). Therefore, CFA can be used instead of CB in rubber industry. It improves the mechanical properties like hardness, tensile strength and tearing energy of rubber (Ansarifar et al., 2005). Furthermore, silica has great influence for the protection of environment because it emits less CO2 in the environment during its production, as well as it plays an important role in tire industry due to its good rolling resistance and enhanced wet and ice traction (Martin et al., 2015).
Since last few years, the silicone rubber and epoxy resin have great potential in industry because of their use as alternative material of ceramic and glass and its properties, like dielectric, volume resistivity, mechanical strength, thermal conductivity and light weight (Fernando and Gubanski, 2010; Manjang and Nagao, 2011; Lau and Piah, 2011; Kitta et al., 2016; Gençoğlu, 2016). Due to their light weight, it is easy to use and control than other ceramic and glass materials (Zhu et al., 2016). Furthermore, polymer insulator especially silicone rubber is a hydrophobic material and can be used as outdoor insulator. Especially in rainy weather, the hydrophobic properties of silicone rubber has a benefit to prevent the leakage of current due to the low conductivity of the insulator (Amin et al., 2009).
Moreover, plastic waste is also a problem for various countries. Historic data shows that 2 million metric tons (MT) of plastic waste was produced in 1950 in China which was increased to 322 million MT in 2015 (Geyer et al., 2017). China is one of the top country in plastic waste and CFA waste production (Peng et al., 2018; Chen et al., 2019), but the recycling and reuse practice of CFA waste is very low as compared to plastic waste. Therefore, this study aims to reuse the waste product (CFA) of coal power plants in rubber conveyer belt instead of calcium carbonate or talcum powder and in recycling of plastic poly propylene (PP) as bonding filler material instead of barium sulfate to increase the durability of plastic products and to reduce cost, CFA waste and plastic waste.
At present, fly ash is mainly utilized in the construction industry, such as brick, cement, building fillers etc. (Shi et al., 2019). But in this study, the CFA was used as filler material in the rubber and plastic to utilized the CFA as maximum, because CFA is cheaper filler material instead of others filler materials. The unit price is less than 200 CNY/ton in China, and most of the power plants cannot sell their fly ash waste in the area above 200 km radius. In this study, smooth surfaced CFA was used instead of rough CFA, due to the need of smooth surface of rubber and plastic products. So that, high-value utilization of fly ash has been subjected to research experts of various fields but the grinding equipment’s for fly ash pulverization are not enough in the respected areas. And only with a certain extent of particle size (20 µ/m) is considered as high-value fly ash. The high-value fly ash utilization can make a substantial breakthrough that enhance the quality of the product, and reduce waste. Therefore, it is required to develop technology for the utilization of high-value fly ash.