Mechanical Properties of Luffa Acutangula-Filled Polypropylene MUHAMMAD FAKHRURAZI Daud 1,a, ENGKU ZAHARAH Engku Zawawi 1,b, Dzaraini Kamarun 1,c

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1 Advanced Materials Research Online: ISSN: , Vol. 812, pp doi: / Trans Tech Publications, Switzerland Mechanical Properties of Luffa Acutangula-Filled Polypropylene MUHAMMAD FAKHRURAZI Daud 1,a, ENGKU ZAHARAH Engku Zawawi 1,b, Dzaraini Kamarun 1,c 1 Faculty of Applied Sciences, Universiti Teknologi MARA, Shah Alam, Malaysia. a k550i_87@yahoo.com, b engku946@salam.uitm.edu.my, c dzaraini@salam.uitm.edu.my Keywords: Luffa Acutangula, Lignocelluloses, Composites Abstract. The value of Luffa acutangula, a species of the melon family, Curcubitaceae as food diminished as the fruit matured. They are then disposed as industrial or domestic waste material. However, the fibers of the matured fruits, also known as lignocelluloses fibers have high mechanical strength and can be used as reinforcing fillers for polymers. In this present study, treated and untreated fibers of Luffa acutangula were loaded as fillers for polypropylene (PP) at 1%, 3% and 5% loading. PP fiber composites loaded with alkali-treated fibers showed lower tensile and impact strength compared to PP fiber composites with untreated fibers. Thermal analysis of the fibers showed that alkali-treated fibers were deprived of the lignin content present in untreated fiber. This led to the lower mechanical properties of the alkali-treated luffa-filled PP composites as compared to its untreated counterpart. Increasing the fiber loading of the composites, increased the tensile and impact strength of untreated luffa-filled PP but decreased the tensile and impact strength of alkali-treated luffa-filled PP. This is in accordance to the removal of the lignin component upon alkali treatment which acts as a strengthening as well as energy absorption component of the fiber. Introduction Nowadays, developments in natural fibers such as hemp, jute, kenaf, sisal, and bamboo have shown that it is possible to obtain well performing composite materials using these materials for reinforcement. Natural fiber-reinforced polymer has many advantages such as light weight, reasonable strength and stiffness, renewable and biodegradable. Other advantages of utilizing natural fibers are related to their cycle of production that is economical and their ease of processing which demands minor requirements in equipment and safer handling and working conditions as compared to synthetic fibers such as glass fibers [1]. Luffa acutangula is a species of Luffa, economically grown for its unripe fruits as a vegetable. Meanwhile fibers of mature fruits are commonly used to make cleaning sponges. Luffa Acutangula fiber has been used as a support of immobilization for the discoloration of certain solutions and dyeing water [2]. Other species of luffa fibers such as Luffa aegyptiaca and Luffa cylindrica has been used for other technical applications such as to reinforce plastic materials using thermoplastics [3,4] and thermosetting polymers as matrix [5,6]. In this project, Luffa acutangula fibres obtained from local plant species were used as fillers for polypropylene to determine the possibility of using these fibers in commercial plastic products. The mechanical properties of Luffa acutangula-filled polypropylene at three different fiber loadings were determined. Fibers were also treated with alkaline solution to modify its structure for possibility of providing better interaction with the PP matrix. Experimental Material. Polypropylene pellets were supplied by Etilinas (M) Sdn. Bhd. Luffa acutangula fibers were obtained from matured fruits obtained at local farms. 40% (wt/vol.) NaOH solutions were prepared using distilled water. Pre-treatment of Luffa Acutangula with NaOH. Seeds of the dried fruit of Luffa acutangula fibres were first removed before crushing it into fibers of length 2-3 mm. The fibers were then treated with 40 % sodium hydroxide (NaOH) solution by immersing the fibres in the solution for 20 minutes at C. The fibers were then washed with distilled water until neutral ph was achieved; and dried in an oven at 70 C for 6 hours. All rights reserved. No part of contents of this paper may be reproduced or transmitted in any form or by any means without the written permission of Trans Tech Publications, (ID: , Pennsylvania State University, University Park, USA-09/04/16,12:34:19)

2 88 Progress in Polymer and Rubber Technology Preparation of Polypropylene-Luffa acutangula (PP/LA) Composite. PP, untreated and treated luffa fibers were mixed together using a twin screw extruder according to the fomulation in table 1. Extrudates were cut into smaller pieces and compressed into square sheets using a compression moulding machine. Rectangular test pieces were prepared from these sheets; of sizes as specified in the standards used for measurement of its mechanical properties. Table 1 Formulation for preparation of PP/LA composites Sample No. Polypropylene (wt %) Untreated luffa Treated Luffa (wt %) (wt %) Characterization Thermal Analysis of Luffa Fiber. Determination of thermal properties of luffa fiber from enthalpy changes upon heating was performed on a differential scanning calorimeter (DSC), Perkin Elmer DSC 7 under N 2 atmosphere at a heating rate of 20 C/min. A thermogravimmetric analyzer (TGA) from Perkin Elmer, TGA 7 was used to determine the decomposition temperatures of luffa acutangula fibers. Temperature scans were conducted from 50 to C at a heating rate of 20 0 C/min. under N 2 environment. Mechanical Testing of PP-Luffa Composite. The tensile strength of the composite was measured according to ASTM D638 using an Instron Testometric Tensile Machine. Based on the standard method, the luffa- filled PP was cut into rectangular shape using a wood cutter. The thickness of the samples was measured at three different positions along the length of the specimen and the average thickness was recorded. The test speed used was mm/min with the gauge length fixed at 50.00mm. Five samples were conducted for each formulation. Impact strength of the composites was determined according to ASTM D256 using a Ray- Ran Machine. These tests were carried at ambient temperature; the hammer used weighed kg operated at a speed of 3.5 m/s. Five test pieces were used for each formulation. Each test piece was notched at 2 mm depth. Results and Discussion Thermal Analysis of Luffa Fiber Thermogravimetric Analysis. The results from thermogravimetric analyzer for luffa fiber are as shown in Fig.1. The derivative weight (DTG) curve showed three different decomposition temperatures at C, C and C, which corresponded to the removal of water, degradation of cellulosic component and lignin respectively that were present in the untreated luffa fibres. The percentages of each component present were: water (12%), cellulosic materials (54%) and lignin (34%) as determined from the weight % curve.

3 Advanced Materials Research Vol Fig.1 TGA and DTG curves of luffa acutangula untreated fibres Luffa fibres treated with base solution showed only two peaks that corresponded to temperatures of water removal and degradation of cellulosic components of the fibre (Fig. 2). The peak detected at C in untreated fibre was not present in the DTG curve of the treated fibre, showing that alkaline treatment removed the lignin component of the fibre. Similar delignification of luffa fibers by NaOH was reported by Ghali et al [7]. The cellulosic materials which were of lower composition (40%) decomposed at lower temperature (298 0 C) compared to the untreated fibres. The treated fibre had a higher percentages of water (20%) compared to the untreated fibre (12%). In general, both treated and untreated fibers remained thermally stable at temperatures below C which qualified it to be fillers for common thermoplastic matrices. Fig. 2 TGA and DTG curves of Luffa acutangula-treated fibres Differential Scanning Calorimetry. The DSC curve of untreated luffa acutangula fibres is shown in fig.3. Two melting peaks (T m ) at 86 0 C and C were recorded. These two peaks corresponded to two different crystalline structures of cellulosic material in untreated of Luffa acutangula fibres. This cellulosic component could be the - and -cellulose, commonly present in lignocelluloses fibers [8].

4 90 Progress in Polymer and Rubber Technology 86 C 100 C Fig. 3 The DSC curve of untreated luffa acutangula fibres showing melting peaks (shown by blackcoloured arrows) Fig.4 The DSC curves of treated Luffa acutangula fibers. Treated luffa acutangula fibres (fig.4) showed only one melting peak at 100 C. This suggested that alkaline treatment modified the two crystalline structures of the fibre into one single crystalline structure. Alkaline treatment of the fibres caused removal (leaching) of the fibrous, amorphous lignin component (as shown by the TGA curves of fig.2); and rearrangement of the cellulosic component. Mechanical Properties of PP/Luffa Composite Young s Modulus and Tensile Strength. Young s modulus illustrates the stiffness of a material while stress at peak demonstrated the tensile strengths of the composite material. Fig. 5 and 6 show the results of the Young s modulus and stress at peak respectively for blank PP (denoted as 0 wt% fibre loading), untreated and treated Luffa acutangula fibers-pp filled composites. Fig. 5 The Young s Modulus for blank PP (0 wt% of fibre loading), untreated and treated luffa acutangula fibres- filled PP composites

5 Advanced Materials Research Vol Fig. 6 The stress at peak for blank PP, untreated and treated luffa acutangula-filled PP composites Both the values of Young s modulus and tensile strength of 1% luffa-loaded composites are higher for treated fibre counterpart compared to untreated fibre. However, increasing the fibre loading further, decreased the two mechanical properties measured for the treated fibre composites; and increased the untreated counterparts. Moreover, 3% and 5% untreated fiber-loaded composites showed higher Young s modulus and tensile strength compared to the treated composites. The reduction in both the Young s modulus and tensile strength for treated Luffa acutangula fibres compared to the untreated fibre-filled composites can be explained by the removal of lignin content from treatment with NaOH. Both the lignin and crystalline cellulose content contributed to the increased in tensile properties of the composites. Izod Impact Test. Fig. 7 shows the impact strength for blank PP, untreated and treated Luffa acutangula fibers-pp filled. It was observed that increasing the fiber loading from 1% to 5% increased the strength of both the untreated and treated fibre-filled PP. The impact strength of the 5 % treated fiber-filled composite however remained constant. Fig. 7. The impact strength for blank PP, untreated and treated luffa acutangula fibers-pp filled. The untreated fiber-filled PP showed higher strength than the treated fiber-filled PP. For 1% fiber loaded, untreated samples show an average value of KJ/m² compared to KJ/m² of the treated samples. In the 3% fiber loaded samples, untreated ones shows an average value of KJ/m² but for the treated sample, a value of KJ/m² with a 20% reduction in impact resistance. The value is also higher (5.169 KJ/m²) in the 5% untreated fiber-loaded PP compared to the treated fiber-loaded PP (3.755 KJ/m²). The tensile properties of the untreated luffa acutangula-filled samples showed greater strength compared to the treated luffa acutangula-filled samples at 3 and 5 % fiber loading as discussed earlier. Similar trend was observed in the impact strength where the increased in fiber loading of untreated counterparts resulted in increased impact strength. The ability of untreated luffa

6 92 Progress in Polymer and Rubber Technology acutangula-filled PP to absorb more energy than the treated luffa acutangula-filled PP showed that the lignin content is desirable for additional strength of PP as a composite material. The higher amount of water present in the treated fiber composites could have also contributed to the decreased in the mechanical properties of the composites. Conclusion Alkaline treatment of luffa fibers removed the lignin component of the fiber resulting in decreased tensile and impact strength of PP/Luffa composite compared to the untreated fiber/pp composites. The lignin content contributed significantly to the mechanical strength of the PP/Luffa composite. References [1] J.Holbery and D.Houston, Natural-Fiber-Reinforced Polymer Composites in Automotive Applications, JOM,, Volume 58, Issue 11, (2006), p.80 [2] H.Demir, A. Top, D.Balkose, S. U. lku, Dye adsorption behavior of Luffa cylindrica fibers, Journal of Hazardous Materials, Volume 153, Issues 1 2, 1 (2008), p.389 [3] H.Demir, U.Atikler, D.Balkose, F. Tihminlioglu, The Effects of Fiber Surface Treatment on The Tensile and Water Sorption Properties of Polypropylene-Luffa Fiber Composites, Composites: Part A 37 (2008), p.447 [4] K.Kaewtatip and J.Thongmee, Studies on the structure and properties of thermoplastic starch/luffa fiber composites, Materials & Design, Volume 40, (2012), p.314 [5] C.A. Boynard, S. N. Monteiro, J. R. M. d'almeida, Aspects of alkali treatment of sponge gourd (Luffa cylindrica) fibers on the flexural properties of polyester matrix composites, Journal of Applied Polymer Science, Volume 87, Issue 12 (2003), p.1927 [6] M.A. Paglicawan, M.S. Cabillon, R.P.Cerbito and E.O.Santos, Loofah Fiber as Reinforcement Material for Composite, Philippine Journal of Science, 134 (2) (2005), p.113 [7] L.Ghali, S.Msahli, M.Zidi, F.Sakli, Effect of pre-treatment of Luffa fibres on the structural properties, Materials Letters 63 (2009), p.61 [8] V.O.A. Tanobea, H.Thais, D. Sydenstrickera, M. Munaro, S. C. Amico, A comprehensive characterization of chemically treated Brazilian sponge-gourds (Luffa cylindrica), Polymer Testing 24 (2005), p.474

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