Technical Report Mechanical properties of soil buried kenaf fibre reinforced thermoplastic polyurethane composites S.M. Sapuan ⇑ , Fei-ling Pua, Y.A. El-Shekeil, Faris M. AL-Oqla Department of Mechanical and Manufacturing Engineering, University Putra Malaysia, 43400 UPM Serdang, Selangor, Malaysia article info Article history: Received 12 January 2013 Accepted 5 March 2013 Available online 15 March 2013 abstract A study on mechanical properties of soil buried kenaf fibre reinforced thermoplastic polyurethane (TPU) composites is presented in this paper. Kenaf bast fibre reinforced TPU composites were prepared via melt-mixing method using Haake Polydrive R600 internal mixer. The composites with 30% fibre loading were prepared based on some important parameters; i.e. 190 °C for reaction temperature, 11 min for reaction time and 400 rpm for rotating speed. The composites were subjected to soil burial tests where the purpose of these tests was to study the effect of moisture absorption on the mechanical properties of the composites. Tensile and flexural properties of the composites were determined before and after the soil burial tests for 20, 40, 60 and 80 days. The percentages of both moisture uptake and weight gain after soil burial tests were recorded. Tensile strength of kenaf fibre reinforced TPU composite dropped to 16.14 MPa after 80 days of soil burial test. It was also observed that there was no significant change in flexural properties of soil buried kenaf fibre reinforced TPU composite specimens. Ó 2013 Elsevier Ltd. All rights reserved. 1. Introduction Nowadays, the use of thermoplastic composites produced from synthetic polymers filled with natural fibres has attracted the attention of many researchers worldwide. The major advantages of using natural fibres are low cost, availability and environmen- tally friendliness [1]. Composites made from natural fibres show comparable specific mechanical properties to synthetic fibre com- posites [2]. It is proven the use of natural fibres can reduce the dependence on materials obtained from non-renewable fossil based sources. Thermoplastic polyurethane (TPU) is a class of polyurethane polymer and it has been applied in many industries such as in automotive components, and the production of cables, films, and roller systems. TPU contains flexible coiled and rigid hard seg- ments, which can be melted without the degradation of urethane bonds. Thus, it can be formulated to obtain desirable properties such as high modulus and excellent abrasion and tear resistances. The main components of TPU include polyols and isocyanates [3]. Isocyanate active group can readily react with hydroxyl. Kenaf (Hibiscus cannabinus) had become an important commod- ity in Malaysia and it is applied in various industries such as in packaging, automotive, and furniture industries [4,5]. Kenaf is one of the herbaceous type annual plants with short growing per- iod. There are many reasons make kenaf plantation Kenaf has been cultivated for two main benefits; it absorbs nitrogen and phospho- rus from the soil and it accumulates carbon dioxide at a high rate [6,7]. Kenaf can grow up 3–4 m in 5 months under moderate tem- perature. It is reported that kenaf can yield three times a year in Malaysian climates [8], and 2 ton/acre to 25 ton/acre, depending on many factors such as soil type, variety and month planted [9]. It is a plant with good fibre quality and its stem consists of bast and core fibres. A stem of kenaf tree can produce approximately 34–38% of bast fibres [10–13]. Kenaf bast fibre generally has supe- rior mechanical properties compared to other parts of the plant. Attractive features of kenaf fibres include lightweight, low cost, renewability, biodegradability and high mechanical properties. Ke- naf fibres demonstrated higher cellulose content and therefore bio- degradable [10,14,15]. El-Shekeil et al. [3,11,16–18] have studied the combination of TPU with kenaf fibres. In their studies new TPU/kenaf composites were developed. Effect of fibre size, fibre loading, various treat- ments on mechanical, thermal, chemical and morphological prop- erties were studied. The outcome of their research has shown that TPU was successfully combined with kenaf. TPU/kenaf composites were treated with Sodium Hydroxide (NaOH) [16] and isocyanate additive and chemical treatments [17,18]. The best tensile proper- ties were obtained from using NaOH followed by isocyanate chem- ical treatment [18] for TPU/kenaf composites. In this paper, a study of tensile and flexural properties of soil buried kenaf bast fibre reinforced TPU composites is presented. 0261-3069/$ - see front matter Ó 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.matdes.2013.03.013 ⇑ Corresponding author. Tel.: +60 3 89466318. E-mail address: sapuan@eng.upm.edu.my (S.M. Sapuan). Materials and Design 50 (2013) 467–470 Contents lists available at SciVerse ScienceDirect Materials and Design journal homepage: www.elsevier.com/locate/matdes