Contents lists available at ScienceDirect Materials Science & Engineering B journal homepage: www.elsevier.com/locate/mseb Properties of antimony oxide-coated clay/polypropylene composites Ahmad Al-Jabareen Materials Engineering Department, Al-Quds University, 20002 East Jerusalem, Palestine ARTICLE INFO Keywords: Composites Fire retardants Antimony oxide Coatings ABSTRACT Brominated flame retardant polypropylene composites were prepared by melt blending polypropylene, tetra- bromobisphenol A, antimony oxide and organically-modified montmorillonite clay. The synergy between anti- mony oxide, clay and the brominated fire retardant was studied by thermogravimetric analysis under oxygen and UL-94 testing. Thermal, structural and tensile properties were studied using differential scanning calori- metry, X-ray diffraction and a universal testing machine respectively. Tetrabromobisphenol A and/or antimony oxide with clay is more efficient than clay alone in improving the flame retardancy of the materials and pro- moting carbonization in the polypropylene matrix. Thermogravimetric analysis showed significant improve- ments in the degradation temperature for all composites compared with the neat one. This can be ascribed to the physico-chemical adsorption of the volatile degradation products on the silicates. In the presence of mon- tmorillonite, the melting and cooling points and degree of crystallization shift to higher values. These ob- servations are compatible with the assumption that montmorillonite and other additives behave as nucleating agents, as a result of their large relative surface area. Moreover, the structure of the composites was char- acterized by scanning electron microscopy, which revealed good dispersion of the fillers in the polymer matrix. The experimental results of tensile tests indicated that the incorporation of clay and other additives improved the Young’s modulus, but decreased the tensile strength. 1. Introduction The expanding use of polymers in varied applications results in a continuous demand for improvement of their mechanical, thermal and electrical properties, in order to meet increasingly stringent conditions. As a result of the chemical structure and weak bonding among the molecules, synthetic polymers easily degrade when they are exposed to high temperatures. This problem significantly limits their industrial applications. Thus, significant research has been focused on improving the thermal and flame retardant properties of these materials [1–3]. Additives and reactive flame retardants, such as chlorinated paraffin, brominated polystyrene, polyvinyl chloride and ammonium phosphate, have been used to protect polymeric materials against fire in the recent years. Traditionally, the incorporation of halogen-based compounds re- presents an economical route for enhancing the flame retardancy of polymers without relinquishing product quality. Brominated flame re- tardants are one of the main materials used to reduce the speed by which the plastic components of consumer goods, including beds, couches, chairs and electronics, could be consumed by fire. Despite regulatory concerns regarding human and environmental contamina- tion caused by the toxic dioxins and furans evolved during the combustion of halogens, they are still used on a large scale in industry all around the world. While being non-toxic and environmentally sound, halogen-free compounds, especially inorganic substances, re- quire high levels of loading, leading to additional costs, processing difficulties and deterioration of polymer mechanical properties. Alternatively, intumescent systems are relatively expensive with re- gards to large-scale production of low-cost combustible materials [4–6]. Recently, clay/polymer-based composites have attracted increased attention in flame retardancy applications [7–9]. Clays, such as mon- tmorillonite (MMT), are valuable minerals and widely used because of their high aspect ratio, plate morphology, natural abundance and low cost. They are expandable layered silicates and can be intercalated and/ or exfoliated into nanocomposites [10–12]. The use of MMT/polymer composites for flame retardancy causes a decrease in the peak heat release rate (PHRR), a change in the char structure and a decrease in the rate of mass loss during combustion in cone calorimetry [13–15]. Moreover, they do not have the usual drawbacks associated with other fire retardant additives. These composites push the frontiers in the development of flame-retarded polymeric materials and are considered as a revolutionary new flame retardant approach [10]. Research results, however, swiftly noted that clays, while exhibiting astonishing effects on some fire retardant properties of polymers, are not sufficient for https://doi.org/10.1016/j.mseb.2018.11.024 Received 7 January 2018; Received in revised form 11 September 2018; Accepted 29 November 2018 E-mail addresses: ajabareen@science.alquds.edu, ahmad.jabareen@staff.alquds.edu. Materials Science & Engineering B 236–237 (2018) 18–23 0921-5107/ © 2018 Published by Elsevier B.V. T