Over recent decades, most plastic materials processed by incorporating some fillers in it. In this regard, many researchers have continued to close attention towards the study of various fillers and their effects on the advanced polymeric material. Similarly, these fillers and additives incorporate within the polymer matrix to meet various applications and to enhance its mechanical properties, strength, durability, etc. The trends have been significantly arise to the use of waste material as filler owing to its advanced properties in plastic material, ease of availability, and its low cost. In general, fly ash (FA) is a waste by-product generated from most thermal power plants and contains varieties of different elemental particles. It is utilized as filler material in a variety of polymeric materials to make sports equipment/devices, household products, construction industries, and in many other engineering applications. Hence, this section particularly focused on fly ash filler and its composites preparation using different polymer matrix.
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Fly ash is the residue formed during coal combustion known by the names such as coal ash and pulverized flue ash. It is generally have light tan in colour and has a fine particulate structure along with its not having virtual odour and is considered as industrial waste pollution. In recent years about million tonnes of coal is burnt to produce electricity so that a huge amount of fly ash is being generated which possesses environmental pollution and many other serious issues as mention in Figure 1. Moreover, India generates about 120 to 150 million tons of fly ash from burning coal in approximately 120 thermal power plants than any other country (Akhtar & Tarannum, 2018). It is also forecasted that the global fly ash market will be expected valued will be USD 11.0 billion by the end of 2024 (Globe News Wire, 2018). The major market for fly ash is within Asia pacific region including countries such as China, Japan, India, South Korea, and rest of the Asia pacific region.
Figure 1. The most important issues to be analyzed from the generated waste fly ash
The coal is major source for energy generation and being available abundantly worldwide. During energy production, the coal is used to burn and during combustion some volatile material as well as carbon also burn off. In meantime the coal impurities such as quartz, clays, feldspar etc. are hugely fused and stayed in suspension form. Thereafter, these fused particles are getting passed using flue gas. At the end these flue gas approaches to low temperature, these fused substances cause to coagulate and form spherical particles. So, these coagulated spherical form of particles called as “Fly ash”. Similarly, the remaining matter are going to agglomerate as well as settle down at the bottom of the furnace are referred as “Bottom ash”. It is also expected that fly ash market will reach US$ 64,761.9 Mn by 2022 which was US$ 39,548.1 Mn in 2015. The growing rate of this fly ash market is reported at a CAGR of 7.3% during the period of 2016-2022 (forecasted period) (Surabhi, 2017).
The another report marked the global fly ash market sized was valued at USD 8.54 billion in 2019 and expected to reach USD 13.33 billion by 2027, (with 5.83%CAGR) as illustrated in Figure 2. The report is basically analysed including both type of fly ash (Class F & Class C) within the study period 2016-2026. The most of the report indicates that there is rise in the fly ash market by > 4% CAGR. A very large amounts of this particles is formed by different thermal power plants, and their disposal generates major environmental challenges (Fly ash market size, 2020).
Figure 2. Fly ash market report (Fly ash market-growth, n.d.)
However, such generated waste fly ash is mainly composed of SiO2 with low-lying contents of Al2O3, Na2O, Fe2O3, K2O, CaO, MgO, SO3, etc. Accordingly, fly ash categorized as class-F as well as class-C type depends upon the percentage of calcium and silicon present in it. In a current situation, such waste fly ash finds utilization in most of the applications such as in brick manufacturing, road, and building construction, cementing industries, mineral filler, structural fills, road base/sub-base, soil modification, and others (Attarde et al., 2014). Nowadays, fly ash finds a place in plastic industries due to its desired properties of the final plastic products after the incorporation of fly ash in it. Similarly, fly ash having a low cost, ease of availability causes rising popularity in plastic industries.