Study on Fire Resistance Ability and Mechanical Properties of Composites Based on Epikote 240 Epoxy Resin and Thermoelectric Fly Ash: An Ecofriendly Additive

Tuan Anh Nguyen , Quang Tung Nguyen, Xuan Canh Nguyen , and Van Hoan Nguyen Bài báo của nhóm tác giả thuộc khoa Công nghệ hóa - Trường Đại học Công nghiệp Hà Nội đăng trên tạp chí Hindawi - Journal of Chemistry Volume 2019. doi: 10.1155/2019/2635231

In this study, fly ash was tested as a filler in epoxy with concentrations of 5, 10, and 20 wt.%. Fly ash particles were modified by
chemical treatments (using NaOH and HCl) to enhance the compatibility and adhesion, making mechanical properties and flame retardancy of materials better. Flexural strength, tensile strength, and impact resistance decrease as fly ash content increases. 'e compressive strength is further increased by the addition of fly ash (compressive strength of the materials including 5, 10, 20 wt.% of fly ash modified with NaOH is 176.01, 189.90, and 197.07 MPa, respectively). 'e interface between fly ash and epoxy matrix plays an important role in determining the mechanical strength and flame retardancy of synthetic materials. 'e results of UL- 94HB and LOI test method for composite materials including 20 wt.% fly ash (modified by NaOH) reached 13.45 mm/min and 22.4%, respectively. 'ese results showed that fly ash is an efficient additive as a flame retardant which decreases the amounts of additives in products and improves their efficiency. Fly ash was also dispersed into epoxy resin to enhance its resistance to oxidation.

1. Introduction
Flame retardants (FRs) used as additives in a wide range of production play a very important role in suppressing fire generation and delaying fire spread [1, 2]. A composite material based on epoxy resin and fly ash (a by-product from thermal power plan) with a good fire resistance ability was developed. Fly ash used as a flame retardant instead of current ones (for example, organic halogen compounds) reduces environmental problems when compared to using flame retardant epoxy resin [3]. Some popular commercial flame retardants are not only dangerous to human and environment but they also have negative effects on mechanical properties of materials [4]. For this reason, it is necessary to find an ecofriendly material which is harmless to human. Additives such as clay and fly ash are being paid great attention. Many authors studied the use of ecofriendly additives such as fly ash, multiwalled carbon nanotube, and nanoclay in enhancing fire resistance of epoxy resin [5–7]. In this study, ultrafine fly ash has been used. Fly ash has been surface-treated with NaOH and HCl acid to improve dispersion in Epikote 240 epoxy matrix. 'e purpose of this study was to improve fire retardancy and improve some mechanical durability, thereby expanding the application area of fly ash for thermal power plants in Vietnam and reducing the impact on the environment. Methods such as UL 94 and limiting oxygen index (LOI) are used to study the combustibility of composites.

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