Wear 262 (2007) 1426–1432 Graphite modified cotton fibre reinforced polyester composites under sliding wear conditions S.A.R. Hashmi ∗ , U.K. Dwivedi, Navin Chand Regional Research Laboratory, CSIR, Hoshangabad Road, Habibganj Naka, Bhopal 462026, India Received 14 June 2006; received in revised form 1 December 2006; accepted 9 January 2007 Available online 12 February 2007 Abstract Graphite modified polyester–cotton composites were developed and studied for friction and sliding wear behaviour at different applied loads and graphite concentrations. Sliding wear tests were conducted using pin-on-disc apparatus. The composite pins were tested against EN-31 steel disc. The specific wear rate of polyester reduced on reinforcement of cotton and on addition of graphite. The coefficient of friction of polyester resin increased on cotton reinforcement and reduced significantly on addition of graphite in cotton–polyester composite. The temperature of contact surface reduced on addition of graphite in cotton–polyester composite. The reduction in wear rate of graphite modified polyester–cotton composite has been discussed with the help of scanning electron microscope (SEM) observations of worn surfaces, coefficient of friction and the temperature of contact surface. © 2007 Elsevier B.V. All rights reserved. Keywords: Cotton; Polyester; Graphite; Sliding wear 1. Introduction A recent review on frontiers of fundamental tribological research emphasizes the concern over the environmental issues such as biodegradability in the development of tribo-materials [1]. The environment friendly, natural-fibre reinforced polymer composites are being preferred over the synthetic fibre rein- forced composites due to their inherent bio-degradability, low density, a range of mechanical properties, less abrasiveness, etc. [2–8]. Amongst the natural fibres, cotton is one of the most popu- lar fibre used in several applications those varying from common fabrics to composites [8–14]. The cotton waste has been used as reinforcing fibres for the preparation of the cost-effective, biodegradable composites and was reported to enhance signif- icantly the biodegradation rate [15]. Similarly a cotton stalk fibre/gypsum composite was proposed as building material due to its low density, good thermal and acoustic insulation, and a high strength to weight ratio [14]. The performance of cotton fibre reinforced polymer matrix composite in-terms of physical, mechanical and thermal prop- ∗ Corresponding author. Fax: +91 7552488323. E-mail address: sarhashmi@rediffmail.com (S.A.R. Hashmi). erty, etc. has been reported recently [8,12–16]. An addition of 27.5 vol.% of cotton in unsaturated polyester resin increased the impact strength from 61 to 971 Nm/s 2 per unit width, flex- ural strength from 101.8 to 142 MPa, modulus of elasticity at bending from 2.4 to 4.2 GPa [9]. The tribological study of cot- ton fibre reinforced polyester against stainless steel reported an increased coefficient of friction with volume fraction of cotton fibres. The wear rate decreased with increased volume fraction of cotton fibre in polyester resin up to a 15 vol.% of cotton fibre and remained almost constant thereafter. The orientation of fibres in the composites affects coefficient of friction that stabilized after initial variations. [11]. The incorporation of 1/3rd wt. % of cotton fibres in the unsaturated polyester resin improved the structural integrity of material under sliding wear condition which was nearly double to that of un-reinforced polyester resin [16]. In an attempt to further improve the tribological properties of cotton–polyester composites, graphite was incorporated as a friction modifier in cotton–polyester composite and charac- terized for friction and sliding wear performance of composite. The graphite is another form of carbon in which carbon atoms are arranged in layered structure and that has attained high importance due its lubricating effectiveness and has been well documented as far tribological properties are concerned [17–20]. The experimental study on graphite filled thermosetting resin 0043-1648/$ – see front matter © 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.wear.2007.01.014 brought to you by CORE View metadata, citation and similar papers at core.ac.uk provided by Advanced Materials and Processes Research Institute, Bhopal