2351-9789 © 2015 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).
Selection and Peer-review under responsibility of the Scientific Committee of MIMEC2015 doi: 10.1016/j.promfg.2015.07.062
Procedia Manufacturing 2 ( 2015 ) 353 – 358
ScienceDirect
2nd International Materials, Industrial, and Manufacturing Engineering Conference, MIMEC2015,
4-6 February 2015, Bali Indonesia
The effects of the alkaline treatment’s soaking exposure on the
tensile strength of Napier fibre
M.J.M. Ridzuan
a,*,
M.S. Abdul Majid
a, M. Afendi
a, K. Azduwin
b, S.N. Aqmariah
Kanafiah
aand Y. Dan-mallam
a.
aSchool of Mechatronics, Universiti Malaysia Perlis, Pauh Putra Campus, 02600 Arau, Perlis, Malaysia.
bFaculty of Technology Engineering, Universiti Malaysia Perlis, Unicity Alam Campus , 02100 Padang Besar, Perlis, Malaysia. *Corresponding Email: ridzuanjamir@unimap.edu.my
Abstract
The effects of soaking time during the alkaline treatment on the tensile strength of Napier grass fibre and its morphology are discussed. The fibres were treated with 10% of Sodium Hydroxide (NaOH) concentration solution at different soaking times exposure; 3, 6, 12, 18 and 24 hr. The single fibre tests were then performed in accordance with ASTM D3822-07 standard. The surfaces of the fibres prior and after the treatment were observed with a metallurgical Microscope MT8100. The results show that the fibre subjected to 6 hr NaOH treatment yields the maximum tensile strength, albeit lower elastic modulus. Morphology study on the other hand found that the fibre became rougher after treatment with 18 and 24 hr of soaking resulted in severe surface damage of the fibre.
© 2015 The Authors. Published by Elsevier B.V.
Selection and Peer-review under responsibility of the Scientific Committee of MIMEC2015. Keywords: Natural Fibre; Napier grass; Alkaline treatment; and Tensile properties
1. Introduction
“Napier grass” (Pennisetumpurpureum) is a plant with an interesting source of fibres which originally from Brazil[1]. Napier grass can grow well with limited nutrient for growth. It can mature in a short time between 3–4 months after planting and can continue to grow at an interval of 6–8 weeks up to 5 years [2]. It contains high fibre composition which can be up to 40%. To date, few studies on Napier grass fibres have been conducted by researchers while a serious in-depth study about it is still ongoing [3]. Tremendous progresses have been made in recent years in the development of materials from agricultural crops based fibres. In search to find substitutes for non-biodegradable-manmade fibres, researchers continue to explore the suitability and more importantly durability of natural fibres as reinforcing materials in many composite engineering applications. Liu et al. and Rao et al. found © 2015 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license
(http://creativecommons.org/licenses/by-nc-nd/4.0/).
that the natural fibres have high potentials to be used as alternative to non-biodegradable glass and carbon fibres in production of thermosetting or thermoplastic composites[4][5].
Alkaline treatment was found to have positive effects on the natural fibres. The resulted rougher surface of the fibres provides better mechanical interlocking with the resin system hence stronger interfacial strength between them. Through study conducted by others, they have reported improvements in mechanical properties of natural fibres when undergoes alkalization process for different soaking periods and at different concentrations. Reddy et al. reported degradation in thermal and tensile properties of alkali treated (up to 5%) Napier grass fibres [3]. Murali Mohan Rao et al. later reported the investigation on the tensile properties of Indian grown Napier grass fibres extracted through chemical and water retting processes [5]. The higher strength and abundant availability of Napier grass fibres have been the prime reasons for the choice of these fibres for the study [6]. Bachtiar et al. on the other hand reported that the alkaline treatment improved the tensile properties of sugar palm fibre reinforced epoxy composites. However further increment of the alkaline concentration and soaking periods reduces the tensile strength due to severe damages to the fibres [7]. Haameem et al. also reported 10% of alkaline treatment of Napier grass fibre yield highest strength compared to untreated fibre [8]. They went further and investigated the tensile strength of the Napier grass fibre/polyester composites. They results indicate a good potential uses of Napier grass fibres in composite applications[9].
The main aim of this paper is to examine the effects of soaking time during alkaline treatment to the tensile strength of the Napier grass fibre. The mechanical properties and surface morphology were then analyzed and discussed.
2. Experimental Procedure 2.1. Extraction of the fibres
Napier grasses were harvested from a local plantation in Bukit Kayu Hitam, Kedah located in north of Peninsular Malaysia. The fibres were manually extracted from grass internodes after subjected to water retting process. Initially the stems were cleaned and crushed using a mallet to separate the fibres strands. Subsequently, the short grass stems were immersed in a running tap water for a few weeks to facilitate the separation process. Finally the fibre strands were cleaned using distilled water and dried under the sun to ensure removal of moisture content of the fibres.
2.2. Alkaline Treatment
The processed Napier grass fibre strands were then treated with 10% aqueous solutions of NaOH at room temperature for 3, 6, 12, 18 and 24 hr, maintaining the liquor ratio 40:1 to remove the hemicelluloses and surface impurities of the fibre. Finally, the fibres were cleaned using distilled water and dried at room temperature.
2.3. Physical Properties
The physical properties of the treated and untreated fibres are presented in Table 1. The measurement of the mass, length, and diameter were taken prior to the tensile test to ensure the properties of the specimens were maintained for analysis purpose. The main aim of the alkaline treatment is to remove amorphous components and reduce hemicelluloses fraction, thus enhancing the strength of fibres [10]. Table 1 shows the gauge lengths of treated fibres are 136 mm and untreated fibre is 165 mm. The mass of the treated fibres are in between 0.004 g to 0.01 g while for untreated fibre the mass recorded was 0.002 g. The ranges of average diameter of the fibres are 0.15 mm to 0.27 mm.
Table 1: Physical properties of treated and untreated fibres Soaking
Time
Physical Properties Average Diameter
(mm) Length (mm) mass (g) Area (mm2)
3 hr 0.24 136 0.007 0.044 6 hr 0.27 136 0.009 0.057 12 hr 0.18 136 0.004 0.025 18 hr 0.15 136 0.004 0.019 24 hr 0.27 136 0.01 0.06 Untreated 0.26 165 0.002 0.053 2.4. Tensile Test
The tensile strength of the fibre were determined through a single fibre tensile testing in accordance with ASTM D3822-07 standard [11]. The treated and untreated fibres were weighed using analytical balance device and the length of fibre strand was measured microscopically. The surface and the diameter of the fibres were observed using Metallurgical Optical Microscope MT8100. The fibre was mounted onto a tab-shaped piece of paper with the gauge length greater than 100 mm. The tensile strengths of the treated and untreated fibres were then determined using an INSTRON 5848 Micro universal testing machine with a load cell of 2kN, at crosshead speed of 1 mm/min.
3. Results And Discussion
Six samples of fibre strands of Napier grass were tested and their maximum stress, Young’s modulus and surfaces morphology of test samples were measured, observed and discussed. The samples consist of treated and untreated fibres with different soaking times.
Fig. 1 shows the stress-strain responses of the treated and untreated fibres. The results show the stresses between treated and untreated fibres were distinctly different. The maximum stress of untreated fibre was calculated slightly under 40 MPa which is much lower than those treated fibres. The finding confirms the improvement in the mechanical properties of the fibres after subjected to alkaline treatment. The maximum strength of 3 hr NaOH exposure fibres yields almost 50% increment in strength at 60 MPa. The maximum strengths for treated fibres achieved for 6, 18 and 24 hr soaking time were recorded around 94 to 96 MPa, whilst the maximum strength of treated fibre with 12 hr soaking time was recorded at 80 MPa.
Fig. 2 illustrates the changes in Young’s modulus of the fibres after subjected to alkaline treatments. The highest modulus was obtained for untreated fibre at 3.1 GPa. Slight lower in the modulus were observed between 3 and 18 hr soaked treated fibres at 2.0GPa and 1.8 GPa respectively. From the results, it can be said that, as the strength increases with increased in soaking time during treatment, the fibres become less elastic with up to 60% reduction in elastic modulus.
The slight variation in stress-strain responses towards the increment of soaking time of treated fibres is suspected due to the differences of the physical properties of the fibre. As can be seen in Table 1, the mass of 12 and 18 hr soaking times treated fibres were 0.004 g, which is less than the 6 and 24 hr soaked treated fibres which were weighed at 0.009 and 0.01 g respectively.
The morphologies of untreated and treated fibres with different soaking time are shown in Fig. 3. Significant differences in the surface morphology between the fibre before and after the treatment at different soaking times were observed which suspected to influence the tensile strength of the fibre. The treated fibres were observed with rougher surfaces at 3, 6 and 12 hr, which expected to provide a better interlocking mechanism between the polymer
and fibres in reinforced composites thus improves t reported in the previous research according to Oma untreated fibres have multi cellular structure, where severe damage textures can be seen at the 18 and 24 The maximum strength of treated fibres was obs since the 24hr soaked fibres observed with a more s soaking time to yield the maximum strength.
Fig.1: Stress-strain responses of treated and untreat alkaline treatment
Fig.2: Young's Modulus of treated and untreated alkaline treatment 3.1 0 0.5 1 1.5 2 2.5 3 3.5 Y oung 's Modul us (Gpa ) Untreated
the interfacial bonding between them [12]. Similar findings w ar Faruk et al. [13]. According to Reddy et al. [10], generally e lignin and hemicelluloses bind a bundle of individual cells. 4 hr soaking time of treated fibres.
served with 6 and 24 hr soaking times at over 90 MPa. Howe severe surface damage thus 6 hr is the concluded as the optim
ted Napier grass fibre subjected of different soaking times dur
d Napier grass fibre subjected of different soaking times during 2 1.2 1.2 1.8 1.2 3h 6h 12h 18h 24h were y all The ever, mum ring g
Fig.3: The effect of the alkaline treatment’s soaking exposure on the fibre’s surface morphology of the fibres 4. Conclusion
The tensile properties of the untreated and treated Napier grass fibre with 10% NaOH aqueous solutions were investigated. The 6 and 24 hr soaking time during treatment yield the highest strength. However, the 24 hr soaked fibre was observed with higher degree of textures damage. The alkaline treatment found to improve the tensile strength of the Napier grass fibres. The maximum strength increased with the increment of soaking time. The surface observation shows the texture of the fibres were damage with 18 hr soaking time of treated fibres and above. From this study, Napier grass fibres shows potentials to be used as reinforcing fibres in composites structures.
Acknowledgements
The authors would like to thanks to Ministry of Education under Fundamental Research Grant Scheme(FRGS) no. 9003-00382 for the financial support. The authors gratefully acknowledge the support from School of Mechatronics, University Malaysia Perlis.
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