Temperature effect on tribological properties of polyol ester-based environmentally adapted lubricant Nur Atiqah Mohamad Aziz a , Robiah Yunus a,b,n , Umer Rashid a , Nurin Wahidah Mohamad Zulkifli c a Institute of Advanced Technology, Universiti Putra Malaysia, 43400 UPM Serdang, Selangor, Malaysia b Department of Chemical and Environmental Engineering, Engineering Faculty, Universiti Putra Malaysia, 43400 UPM Serdang, Selangor, Malaysia c Department of Mechanical Engineering, University of Malaya, 50603, Malaysia article info Article history: Received 22 April 2015 Received in revised form 4 September 2015 Accepted 5 September 2015 Available online 14 September 2015 Keywords: Polyol ester Tribology properties Pentaerythritol ester Lubricant regime abstract The production of pentaerythritol ester (PE) as food grade lubricant base oil was investigated. The properties of formulated lubricant (AWCI) and neopentyl glycol ester (NPGE) were tested – density, viscosity, total acid number, flash point, copper strip corrosion and NOACK. Wear scar diameter (WSD) and coefficient of friction (COF) were analyzed and compared to commercial lubricant (CL). AWCI which comprised of 0.15% Irgalube 349, 0.15% Irgalube TPPT, and 0.1% Irgamet 39 showed excellent lubricant properties with high flash point, low WSD and low COF at all temperatures despite its lower viscosity than the commercial lubricant, CL. & 2015 Elsevier Ltd. All rights reserved. 1. Introduction In recent decades, environmental friendly lubricant production has been one of the major interesting research subjects to address the health and environmental issues. Particularly in food proces- sing industry, a safe and mechanically reliable lubricant is explored and studied enormously. The information on the tribo- logical properties of ester-based lubricant is scarce, thus require more investigations as compared to widely-known tribological data of mineral oils [1]. Mineral oil has conventionally been used to produce lubricant, however, biodegradability and pollution in soil, water and air; leave them unfavourable even though it has better oxidative stability and higher flash point [2]. Mineral-based chain oil is not safe and may contaminate food after contact. Besides toxicity issue, the depletion of mineral oil is also the rea- sons for synthetic bio-oil to become a promising alternative for base oil [2–5]. Bio-based lubricants available in the market must perform as par as mineral-based oil, and more environmental friendly. However, the commercially available food grade lubri- cants are expensive. Vegetable oils such as soy bean, rapeseed, and palm oil have undergone various studies and investigation to prove that they are potential base oil with characteristics such as renewable, non- toxic, biodegradable and good lubricity. However, these vegetable oils are poor in corrosion [5], oxidative and hydrolytic stability. As vegetable oil is modified through a transesterification process of polyol to produce polyol ester, the characteristics are improved in term of lubricity, viscosity, thermal and oxidative stability as β- carbon in the ester chain is eliminated [6–8]. Formerly, hydro- genation, epoxidation, and post-esterification are the techniques implemented to obtain better oil properties [9,10]. Pentaerythritol (PE), trimethylolpropane (TMP) and neopentyl glycol (NPG) are among the polyol used during the transester- ification process. These polyol esters contribute in varies field of lubricant, such as hydraulic, compressor, aviation, engine and metal working oil [11]. While tribological data on TMP-based esters derived from jatropha oil [12] soybean oil [13,14], castor, rapeseed, and sunflower oil [14] also palm oil [8,10] are widely available as lubricant base oils, far too little attention has been paid for PE ester which is the focus of this paper. The aim of this paper is to evaluate the physical and chemical characteristics of pentaerythritol ester base oil and its formulated oil, neopentyl glycol ester base oil, and commercial lubricant. These studies contribute to information of lubricant regime esti- mation and wear properties of oils at elevated temperature condition. Contents lists available at ScienceDirect journal homepage: www.elsevier.com/locate/triboint Tribology International http://dx.doi.org/10.1016/j.triboint.2015.09.014 0301-679X/& 2015 Elsevier Ltd. All rights reserved. n Corresponding author at: Institute of Advanced Technology, Universiti Putra Malaysia, 43400 UPM Serdang, Selangor, Malaysia. Tel.: þ60 389467531; fax: þ60 389467004. E-mail address: robiah@upm.edu.my (R. Yunus). Tribology International 93 (2016) 43–49