Mechanical and thermal properties of date palm leaf fiber reinforced recycled poly (ethylene terephthalate) composites Alireza Dehghani a , Sara Madadi Ardekani a , Mariam A. Al-Maadeed b , Azman Hassan a , Mat Uzir Wahit a,⇑ a Department of Polymer Engineering, Faculty of Chemical Engineering, Universiti Teknologi Malaysia (UTM), Johor, Malaysia b Materials Technology Unit, Qatar University, Qatar article info Article history: Received 29 January 2013 Accepted 10 June 2013 Available online 22 June 2013 Keywords: Recycled poly (ethylene terephthalate) Date palm leaf fiber Thermal properties Mechanical properties abstract Development of a recycled poly (ethylene terephthalate) (PETr) reinforced with surface treated date palm leaf fiber (DPLF) composites with enhanced mechanical properties have been studied. Surface modified date palm leaf fiber reinforced PETr composites were prepared using twin-screw extruder followed by injection molding and the influence of the DPLF content on the mechanical and thermal behavior of the PETr matrix was evaluated. Upon the addition of fibers, remarkable enhancements in the mechanical properties of the composites were observed. Scanning electron microscopy (SEM) images taken from DPLF fibers showed significant enhancements in the fiber’s surface topography after the surface treat- ment process. Dynamic mechanical analysis (DMA) indicated that the addition of DPLF to PETr matrix increased the composites toughness. The crystallization behavior of the samples, analyzed by differential scanning calorimetry (DSC) indicated an increase in the onset crystallization temperature and showed a higher degree of crystallinity of the composites as compared to PETr, demonstrating that DPLF particles could act as nucleating agents. The results point to the composite’s potential in wider indoor applications. Ó 2013 Elsevier Ltd. All rights reserved. 1. Introduction The history of thermoplastic polyesters goes back to 1929 with the pioneering work of Carothers. Poly (ethylene terephthalate) (PET) was first prepared by Whinfield and Dickson and was pro- duced commercially in 1953 as fiber for the textile industry (Da- cron) by Dupont using modified nylon technology [1]. Because of the good barrier properties of blow molded containers made from PET, it became a very important commercial plastic, used in food packaging and soft drink bottles [2,3]. Production has grown rap- idly in the last two decades annual global production has reached 60 million tons [4], making it a suitable target for recycling [5,6]. Recycled PET often contains contaminations and impurities, which could facilitate the chain scission reactions and lead to degrada- tions during processing. The presence of impurities (PVC contami- nates) and moisture could result in severe hydrolytic degradation of PETr chains and reduces the average molecular weight of the re- sin. This leads to a reduction in intrinsic viscosity and poor mechanical properties [7]. It was proposed that the hydrolytic deg- radation of PET during processing in the presence of moisture is an autocatalytic reaction and that the concentration of carboxyl end groups controlled the hydrolytic degradation and that the in- creased number of carboxyl end groups increase the hydrophilicity of the system and hence, facilitate the penetration of water [8]. On the contrary, other studies suggest that the kinetics of degradation follows the diffusion-controlled system behavior [9]. The concept of using natural fibers as reinforcements in a com- posite structure has been successfully utilized by multiple civiliza- tions throughout world history. Over the past decade a renewed interest on the utilization of natural fibers as reinforcing agents in polymer matrices has been realized worldwide [10–12] and this new class of materials has been used as a substitute for other fiber reinforced composites with applications in the automotive and building industries [11,13,14]. The interest in natural fiber rein- forced polymer composites has grown rapidly due to the high per- formance in mechanical properties, significant processing advantages, low cost and low density [5,15,16]. These are espe- cially important if the fibers are residues of agroindustrial pro- cesses as in the case of date palm leaf fiber (DPLF), which is widely produced in the Middle East. The possibility of finding uses for DPLF in composite manufacturing will help open new markets for what is normally considered waste or for use in low value prod- ucts [17]. However, one limitation of DPLF used as reinforcement is the poor interfacial adhesion between polar–hydrophilic fibers and nonpolar–hydrophobic polymers [18]. Various surface treatment methods as well as coupling agents and compatibilizers such as maleate and silane have been used to increase the compatibility between natural fibers and thermoplastic matrices, thereby enhancing the composites performance [5,19–21]. 0261-3069/$ - see front matter Ó 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.matdes.2013.06.022 ⇑ Corresponding author. Tel.: +60 7 55 35909; fax: +60 7 55 81463. E-mail addresses: dalirza5@live.utm.my (A. Dehghani), masara2@live.utm.my (S. Madadi Ardekani), m.alali@qu.edu.qa (M.A. Al-Maadeed), azmanh@cheme.utm.my (A. Hassan), mat.uzir@cheme.utm.my (M.U. Wahit). Materials and Design 52 (2013) 841–848 Contents lists available at SciVerse ScienceDirect Materials and Design journal homepage: www.elsevier.com/locate/matdes