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Effect of fiber loading on the mechanical and physical properties of “green” bagasse–polyester composite
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H O S T E D BY
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Available online at www.sciencedirect.com
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Journal of Radiation Research and Applied Sciences journal homepage: http://www.elsevier.com/locate/jrras
Effect of fiber loading on the mechanical and physical properties of “green” bagasseepolyester composite Q1
Hamdy M. Naguib a,*, Usama F. Kandi a, Ahmed I. Hashem b, Yasser Baghdady c a
Dept. of Petroleum Applications, Egyptian Petroleum Research Institute (EPRI), Cairo, Egypt Dept. of Chemistry, Faculty of Science, Ain Shams University, Cairo, Egypt c Egyptian Petrochemicals Holding Co., Cairo, Egypt b
article info
abstract
Article history:
The main aim of this work is to fill unsaturated polyester resin with bagasse agricultural
Received 12 May 2015
waste, as reinforcement, to prepare green woodenepolymer composites. Bagasse fibers
Accepted 14 June 2015
were treated with 5% sodium hydroxide and then with dilute sulfuric acid. Bagasseepo-
Available online xxx
lyester composites were prepared by addition of 5, 10 and 15% of untreated and alkali treated bagasse fibers to polyester. The crosslinking reaction was performed using methyl
Keywords:
ethyl ketone peroxide as a catalyst and cobalt octoate as an accelerator. The prepared
Wooden polymer
composites were then exposed to post-curing at elevated temperature for completely
Polyester
crosslinking. The flexural behavior of the prepared composites was studied. An enhance-
Bagasse
ment in the mechanical properties was achieved after chemical treatment. In addition, water absorption and chemical resistance were conducted showing that the produced bagasseepolyester composite with appreciable mechanical and physical properties is a new partner and cost effective material for many advanced industrial applications in addition to their environmental friendly behavior. Copyright © 2015, The Egyptian Society of Radiation Sciences and Applications. Production and hosting 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/).
1.
Introduction
The agriculture waste is a dangerous and harmful environmental problem representing in the burning large quantities of natural fibers. There is no doubt that this bad behavior is the main source of air pollution in many countries. So we tried to exploit these cheep fibers as filler into polymeric materials to achieve a bundle of goals. These targets are summarized in
maintaining of clean environment, production of cheep advanced composites and enhancement the characteristics of the neat polymers. All these desired demands can be achieved by creation of woodenepolymer composites (WPC). Agriculture wastes such as bagasse, rice straw and wood flour (Fig. 1) are very cheap, easily available and renewable. Therefore, composites based on these natural fibers are cheaper than traditional composites (Marcovich, Aranguren, & Reboredo, 2001). Natural fibers are interest in their usage as natural
* Corresponding author. Tel.: þ20 1223744272. E-mail address: [email protected] (H.M. Naguib). Peer review under responsibility of The Egyptian Society of Radiation Sciences and Applications. http://dx.doi.org/10.1016/j.jrras.2015.06.004 1687-8507/Copyright © 2015, The Egyptian Society of Radiation Sciences and Applications. Production and hosting 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/). Please cite this article in press as: Naguib, H. M., et al., Effect of fiber loading on the mechanical and physical properties of “green” bagasseepolyester composite, Journal of Radiation Research and Applied Sciences (2015), http://dx.doi.org/10.1016/j.jrras.2015.06.004
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J o u r n a l o f R a d i a t i o n R e s e a r c h a n d A p p l i e d S c i e n c e s x x x ( 2 0 1 5 ) 1 e5
Fig. 1 e (a) Rice straw, (b) bagasse and (c) wood flour. fillers for different polymers. The new pattern in the preparation of WPC is the use of natural fibers in place of synthetic fibers. Even though synthetic fibers such as fiberglass, rayon, aramid and carbon are used extensively for the reinforcement of plastics; these materials are expensive and non-renewable (de Albuquerque, Joseph, de Carvalho, & Roberto, 2000). Natural fibers have special advantages such as low cost, low density, high specific mechanical properties, non-abrasive and biodegradable properties (Hashim, Roslan, Amin, Zaidi, & Ariffin, 2012; Ramanaiah, Prasad, & Reddy, 2012). One of the most used fibers in WPC is bagasse, the fibrous residue left over after milling of cane plant. Generally, bagasse and other natural fibers consist of cellulose, hemicellulose and lignin in different proportions. Some fibers include other rest even in small concentrations such as pectin and waxes. These undesired non-cellulosic components can lead to the formation of ineffective fiberematrix interface, especially in such large impurities containing fibers, resulting in debondings and voids. Such these voids have bad effects on the physical and mechanical properties of the final composite. For a better interfacial bonding with the matrix, natural fibers are chemically treated to remove these impurities (Wong, Zahi, Low, & Lim, 2010). Unsaturated polyester is a linear thermosetting polymer based on unsaturated and saturated acids/ anhydrides and diols, it is dissolved in unsaturated vinyl monomers such as styrene. The solution of unsaturated polyester with styrene monomer is known as UP resin. The unsaturation in the backbone provides sites for reaction with the double bonds in styrene monomer through peroxide initiators, leading to the formation of three-dimensional network (Malik, Choudhary, & Varma, 2000). UP is capable of producing very strong bonds with other materials; in addition, good toughness and crack stopping capability are particularly important (Willis & Masters, 2003). Unlike the compatible interaction between polar UP and polar natural fibers; nonpolar thermoplastics are not compatible with natural fibers, so an interface with poor adhesion can occur (Geottler, 1983). In order to enhance this week adhesion between fibers and thermoplastics, coupling agents are used in small quantities to treat the fibrous surface (Schneider & Brebner, 1985). Various studies on the application of natural fibers in polymer composites were widely reported; polyesterejute composite (Roe & Ansell, 1985), polyesterecoconut composite (Owolabi, Czvikovszky, & Kovacs, 1985), polyesterebananaecotton composite (Satyanarayana et al., 1983), polyesterestraw composite (White & Ansell, 1983), polyesterepineapple leaf
composite (Devi, Bhagawan, & Thomas, 1997), polyesterecottonekapok composite (Mwaikambo & Bisanda, 1999) and epoxyejute composite (Bledzki & Gassan, 1999) are some of these studies. WPC find advanced applications in construction materials and automotive accessories industry such as door panels, seat backs, headliners, package trays and dashboards. Other potential applications include door and instrument panels, package trays, glove boxes, arm rest and seat back panels (Vilay, Mariatti, Taib, & Todo, 2008). In this work, we prepared bagasseepolyester composites by different loading values of both untreated and alkali treated bagasse fibers. In order to understand the behavior of addition and modification of bagasse fibers, the flexural behavior was studied. Furthermore, water absorption and chemical resistance were investigated for the prepared composites.
2.
Materials and methods
2.1.
Materials
For fiber, bagasse between meshes of 0.5 and 1 mm was obtained as received as residue left over after milling of the local cane, Egypt. For the matrix, we used Crystic-126-Scott Bader unsaturated polyester resin with styrene content of 38% and viscosity of 400 cps. NaOH and HCl were supplied from EPRI lab. Methyl ethyl ketone peroxide and cobalt octoate supported from Sigma Aldrich. All ingredients and chemicals were used without further purification except some bagasse that underwent alkali treatment.
2.2.
Treatment of fiber
Alkali treatment was performed by soaking a part of bagasse in 5% NaOH solution for 60 min at room temperature. 10 g of the treated fibers were dispersed in 200 mL of 6.5 M sulfuric acid for 30 min at 60 C under vigorous stirring. The excess acid was then removed by 8000 rpm-centrifuge for 10 min. The treated bagasse was then filtrated and washed by distilled water to remove any additional chemicals. The washed fiber was heated at 70 C for 4 h to remove all moisture.
2.3.
Preparation of composites
Firstly, untreated (B) and alkali treated bagasse (AB) fibers were added to UP as fillers by 5, 10 and 15% (by weight). Curing
Please cite this article in press as: Naguib, H. M., et al., Effect of fiber loading on the mechanical and physical properties of “green” bagasseepolyester composite, Journal of Radiation Research and Applied Sciences (2015), http://dx.doi.org/10.1016/j.jrras.2015.06.004
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reaction was then performed by addition of MEKP as 2% and cobalt octoate as 0.5%. The composite components and initiators were mixed well together then poured into molds. These molds were previously coated by grease to avoid any stacking with the composites. Before demoulding, samples were kept for 24 h at room temperature for curing followed by 3 h at 85 C for completely crosslinking reaction. Finally, the specimens were cooled at room temperature for 3 h and cleaned from any residual grease that appeared on the specimens.
2.4.
distilled water, maintained at room temperature and then removed from the water at the same time after 24 h. The surface water was wiped off with a dry cloth and the wet specimens were weighted immediately. For 2 h boiling water immersion; samples were placed in a container of boiling distilled water, maintained for 2 h and removed from the water. The specimens were then cooled by distilled water at room temperature for 15 min. After the surface water was removed, the specimens were weighted immediately. Water absorption percentage (DW%) was calculated from Equation (2);
Characterization DW% ¼
2.4.1.
Three point bending test
Three point bending behavior was conducted on BeUP and ABeUP composites according to the specifications of ASTM D 790-03 using 10 kN servo hydraulic testing machine that was run under displacement control mode at crosshead speed 2 mm/min. All tests were performed at room temperature and results were taken as the average value of five samples with dimensions of 180 35 9 mm. The specimen is deflected until rupture occurs in the outer surface of the test specimen or until a maximum strain of 5.0% is reached, whichever occurs first. The flexural strength and Young's modulus of elasticity of the composites were calculated using Equation (1). smax ¼
3Pmax L 2bh2
& E¼
L3 P 4bh3 D
(1)
where smax is flexural strength, E is Young's modulus of elasticity, Pmax is the maximum load, L is specimen span, b is specimen width, h is specimen thickness and (P/D) is the slope of the linear region of the obtained loadedeformation relationship.
2.4.2.
3
Wwet Wconditioned % Wconditioned
(2)
where Wwet and Wconditioned are respectively the weights of specimen after and before immersion.
2.4.3.
Chemical resistance
According to ASTM D 543-95, chemical resistance (CR) test was performed to specimens with the same dimensions of specimens of water absorption test against 10% HCl and NaOH solutions. The composite specimens were completely immersed in both fresh regents at room temperature for 24 h. They were free-suspended to avoid any contact with container walls or bottom. Specimens were then washed by distilled water to remove any additional reagents and weighed immediately after surface drying. The percentage of chemical resistance (CR%) against exposure to chemicals was calculated from Equation (3) as the average of three specimens; CR% ¼
Wexposed Wconditioned % Wconditioned
(3)
where Wexposed is weight after exposure to the chemical reagent and Wconditioned is weight before exposure.
Water absorption
Water absorption (WA) test was performed on BeUP and ABeUP composites following ASTM D 570-98 standards. Samples in the form of disks with 50.8 mm in diameter and 3.2 mm in thickness were weighted and results were calculated as an average value of three samples. For 24 h immersion; the conditioned specimens were placed in a beaker of
3.
Result and discussion
3.1.
Three point bending test
Fig. 2 shows the stressestrain curves (a) for BeUP and (b) for ABeUP composites. It is observed from Fig. 2(a) that increasing
Fig. 2 e Stressestrain curve (a) for BeUP and (b) for ABeUP composites. Please cite this article in press as: Naguib, H. M., et al., Effect of fiber loading on the mechanical and physical properties of “green” bagasseepolyester composite, Journal of Radiation Research and Applied Sciences (2015), http://dx.doi.org/10.1016/j.jrras.2015.06.004
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Table 1 e The mechanical characteristic for BeUP and ABeUP composites. Sample ID
Strength (MPa)
Failure strain
Young's modulus (GPa)
Blank UP 5% BeUP 10% BeUP 15% BeUP 5% ABeUP 10% ABeUP 15% ABeUP
27.3 23.1 19.9 13.8 26.4 23.1 22.2
0.00735 0.00737 0.00633 0.00619 0.00892 0.00744 0.00916
4.39 3.44 3.73 3.01 4.42 4.57 3.40
Fig. 3 e Flexural strength for BeUP and ABeUP composites.
of bagasse content in BeUP composite leaded to reducing the flexural strength. From Fig. 2(b), the flexural strength increased by addition of more AB fiber. In addition, there is an increase in failure strain with ABeUP composite more than BeUP composites. Figs. 3 and 4 respectively represent the flexural strength and Young's modulus of elasticity for all BeUP and ABeUP composites. Young's modulus increased after alkaline treatment recording 4.42 and 4.57 GPa for 5 and 10% ABeUP composites compared with 4.39 GPa of neat UP, but it is still below UP at 15% ABeUP. The mechanical characteristics for BeUP and ABeUP composites are summarized in Table 1. After chemical treatment, the network structure of fibers was removed and new celluloses were generated with free hydroxyl groups that interact with polyester through strong fiberematrix interface. This leads to more uniform dispersion of applied stress and requires more energy for debonding of bagasseepolyester interface. It is clear that with alkali treatment of bagasse, enhanced mechanical behavior was achieved especially at 5 and 10% loadings. This improvement can be attributed to high strength and modulus of modified bagasse fibers and to the strong interfacial adhesion with polyester matrix.
3.2.
Water absorption
Fig. 5 illustrates water absorption percentages of BeUP and ABeUP specimens through immersion in water at room temperature and boiling water. It is clear that increasing of bagasse content leaded to increasing of water absorption percentage for the prepared composites within room
Fig. 4 e Young's modulus for BeUP and ABeUP composites.
temperature and boiling water immersion conditions, but water absorption achieved higher percentages with boiling water. Also, water absorption of ABeUP composites is higher than BeUP composites. After chemical treatment of bagasse surface, more surface area with more hydroxyl groups was exposed to absorb more moisture. The maximum water absorption after alkaline treatment was 0.023% and 0.041% for 15% ABeUP in cold and boiling water immersion. These values are acceptable compared with 0.6% water absorption that was reported by Kord (2012).
3.3.
Chemical resistance
Fig. 6 illustrates chemical resistance percentages of BeUP and ABeUP specimens against 10% HCl and NaOH solutions. Increasing of bagasse content resulted in weight gain of the exposed specimens. The obtained weight increase regarding the absorption of both reagents. After filling UP with AB, the composite absorption for chemicals was increased as noticed in water absorption test. It is clear that all BeUP and ABeUP composites did not lose weight and therefore they not seem as if any erosion occurred.
4.
Conclusion
In this work, “green” woodenepolymer composites based on bagasse-unsaturated polyester composites were prepared by addition of bagasse with 5, 10 and 15% by weight to the polyester resin. Chemical treatment of bagasse fiber was performed by firstly 5% NaOH and then with diluted HCL
Fig. 5 e Water absorption % for BeUP and ABeUP composites with cold and boiling water conditions.
Please cite this article in press as: Naguib, H. M., et al., Effect of fiber loading on the mechanical and physical properties of “green” bagasseepolyester composite, Journal of Radiation Research and Applied Sciences (2015), http://dx.doi.org/10.1016/j.jrras.2015.06.004
66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130
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Fig. 6 e Chemical resistance % for BeUP and ABeUP composites against 10% NaOH and HCl.
solutions. The effect of this treatment on the mechanical and physical properties of the prepared composites was studied. Three point bending test indicated that addition of treated bagasse filler to polyester matrix began to enhance both of flexural strength and Young's modulus compared to untreated bagasse fiber. The chemical treatment of bagasse leaded to stronger interaction at fiberematrix interface compared to untreated fibers getting more uniform dispersion of applied stress and more energy for debonding of bagasseepolyester interface. Water absorption percentage with both room temperature and boiling immersion conditions was increased by addition of more content of bagasse to polyester matrix, especially after chemical treatment. In addition, all bagasseepolyester composites did not show any erosive character against NaOH and HCl solutions. Consequently, preparation of environmentally friendly woodenepolymer composites by filling of polyester matrix with chemically treated bagasse fiber achieved more enhanced characteristics than obtained by untreated bagasseepolyester composites. Such cheep composites can be used in car accessories, building construction and many other advanced industrial applications that can bear high loads in mild operating conditions.
references
de Albuquerque, A. C., Joseph, K., de Carvalho, L. H., & Roberto, J. (2000). Effect of wettability and ageing conditions on the physical and mechanical properties of uniaxially oriented juteerovingereinforced polyester composites. Composites Science and Technology, 60, 833e844.
5
Bledzki, A. K., & Gassan, J. (1999). Composites reinforced with cellulose based fibres. Progress in Polymer Science, 24, 221e274. Devi, L., Bhagawan, S., & Thomas, S. (1997). Mechanical properties of pineapple leaf fibreereinforced polyester composites. Journal of Applied Polymer Science, 64, 1739e1748. Geottler, L. A. (1983). US Patent 4,376,144. Hashim, M. Y., Roslan, M. N., Amin, A. M., Zaidi, A. M., & Ariffin, S. (2012). Mercerization treatment parameter effect on natural fiber reinforced polymer matrix composite: a brief review. Engineering and Technology, 68, 1638e1644. Kord, B. (2012). The impact of plastics virginity on water absorption and thickness swelling of wood plastic composites. World Applied Sciences Journal, 17, 168e171. Malik, M., Choudhary, V., & Varma, I. K. (2000). Current status of unsaturated polyester resins. Journal of Macromolecular Science, 40, 139e165. Marcovich, N. E., Aranguren, M. I., & Reboredo, M. M. (2001). Modified wood flour as thermoset fillers. Part I. effect of the chemical modification and percentage of filler on the mechanical properties. Polymer, 42, 815e825. Mwaikambo, L., & Bisanda, E. (1999). The performance of cotton/ kapok fabricepolyester composites. Polymer Testing, 18(3), 181e198. Owolabi, O., Czvikovszky, T., & Kovacs, I. (1985). Coconut fibre reinforced thermosetting plastics. Journal of Applied Polymer Science, 30, 1827e1836. Ramanaiah, K., Prasad, A. V., & Reddy, K. H. (2012). Effect of fiber loading on mechanical properties of borassus seed shoot fiber reinforced polyester composites. Journal of Materials and Environmental Science, 3, 374e378. Roe, P., & Ansell, M. (1985). Jute reinforced polyester composites. Journal of Materials Science, 20, 4015e4020. Satyanarayana, K., Kulkarni, A., Sukumaran, K., Pillai, S., Cherian, P., & Rohatgi, P. (1983). Performance of banana fabricepolyester resin composites. In I. H. Marshall (Ed.), Composite structures proceedings of the international conference (p. 535). London: Applied Science. Schneider, M. H., & Brebner, K. I. (1985). Woodepolymer combinations: the chemical modification of wood by alkoxysilane coupling agents. Wood Science and Technology, 19, 67e73. Vilay, V., Mariatti, M., Taib, R., & Todo, M. (2008). Effect of fiber surface treatment and fiber loading on the properties of bagasse fiberereinforced unsaturated polyester composites. Composites Science and Technology, 68, 631e638. White, N., & Ansell, M. (1983). Strawereinforced polyester composites. Journal of Materials Science, 18, 1549e1556. Willis, M. R., & Masters, I. (2003). The effect of filler loading and process route on the three-point bend performance of waste based composites. Composite Structures, 62, 475e479. Wong, K. J., Zahi, S., Low, K. O., & Lim, C. C. (2010). Fracture characterization of short bamboo fibre reinforced polyester composites. Materials and Design, 31, 4147e4154.
Please cite this article in press as: Naguib, H. M., et al., Effect of fiber loading on the mechanical and physical properties of “green” bagasseepolyester composite, Journal of Radiation Research and Applied Sciences (2015), http://dx.doi.org/10.1016/j.jrras.2015.06.004
55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108
H O S T E D BY
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Available online at www.sciencedirect.com
ScienceDirect
Journal of Radiation Research and Applied Sciences journal homepage: http://www.elsevier.com/locate/jrras
Effect of fiber loading on the mechanical and physical properties of “green” bagasseepolyester composite Q1
Hamdy M. Naguib a,*, Usama F. Kandi a, Ahmed I. Hashem b, Yasser Baghdady c a
Dept. of Petroleum Applications, Egyptian Petroleum Research Institute (EPRI), Cairo, Egypt Dept. of Chemistry, Faculty of Science, Ain Shams University, Cairo, Egypt c Egyptian Petrochemicals Holding Co., Cairo, Egypt b
article info
abstract
Article history:
The main aim of this work is to fill unsaturated polyester resin with bagasse agricultural
Received 12 May 2015
waste, as reinforcement, to prepare green woodenepolymer composites. Bagasse fibers
Accepted 14 June 2015
were treated with 5% sodium hydroxide and then with dilute sulfuric acid. Bagasseepo-
Available online xxx
lyester composites were prepared by addition of 5, 10 and 15% of untreated and alkali treated bagasse fibers to polyester. The crosslinking reaction was performed using methyl
Keywords:
ethyl ketone peroxide as a catalyst and cobalt octoate as an accelerator. The prepared
Wooden polymer
composites were then exposed to post-curing at elevated temperature for completely
Polyester
crosslinking. The flexural behavior of the prepared composites was studied. An enhance-
Bagasse
ment in the mechanical properties was achieved after chemical treatment. In addition, water absorption and chemical resistance were conducted showing that the produced bagasseepolyester composite with appreciable mechanical and physical properties is a new partner and cost effective material for many advanced industrial applications in addition to their environmental friendly behavior. Copyright © 2015, The Egyptian Society of Radiation Sciences and Applications. Production and hosting 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/).
1.
Introduction
The agriculture waste is a dangerous and harmful environmental problem representing in the burning large quantities of natural fibers. There is no doubt that this bad behavior is the main source of air pollution in many countries. So we tried to exploit these cheep fibers as filler into polymeric materials to achieve a bundle of goals. These targets are summarized in
maintaining of clean environment, production of cheep advanced composites and enhancement the characteristics of the neat polymers. All these desired demands can be achieved by creation of woodenepolymer composites (WPC). Agriculture wastes such as bagasse, rice straw and wood flour (Fig. 1) are very cheap, easily available and renewable. Therefore, composites based on these natural fibers are cheaper than traditional composites (Marcovich, Aranguren, & Reboredo, 2001). Natural fibers are interest in their usage as natural
* Corresponding author. Tel.: þ20 1223744272. E-mail address: [email protected] (H.M. Naguib). Peer review under responsibility of The Egyptian Society of Radiation Sciences and Applications. http://dx.doi.org/10.1016/j.jrras.2015.06.004 1687-8507/Copyright © 2015, The Egyptian Society of Radiation Sciences and Applications. Production and hosting 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/). Please cite this article in press as: Naguib, H. M., et al., Effect of fiber loading on the mechanical and physical properties of “green” bagasseepolyester composite, Journal of Radiation Research and Applied Sciences (2015), http://dx.doi.org/10.1016/j.jrras.2015.06.004
65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129
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2 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65
J o u r n a l o f R a d i a t i o n R e s e a r c h a n d A p p l i e d S c i e n c e s x x x ( 2 0 1 5 ) 1 e5
Fig. 1 e (a) Rice straw, (b) bagasse and (c) wood flour. fillers for different polymers. The new pattern in the preparation of WPC is the use of natural fibers in place of synthetic fibers. Even though synthetic fibers such as fiberglass, rayon, aramid and carbon are used extensively for the reinforcement of plastics; these materials are expensive and non-renewable (de Albuquerque, Joseph, de Carvalho, & Roberto, 2000). Natural fibers have special advantages such as low cost, low density, high specific mechanical properties, non-abrasive and biodegradable properties (Hashim, Roslan, Amin, Zaidi, & Ariffin, 2012; Ramanaiah, Prasad, & Reddy, 2012). One of the most used fibers in WPC is bagasse, the fibrous residue left over after milling of cane plant. Generally, bagasse and other natural fibers consist of cellulose, hemicellulose and lignin in different proportions. Some fibers include other rest even in small concentrations such as pectin and waxes. These undesired non-cellulosic components can lead to the formation of ineffective fiberematrix interface, especially in such large impurities containing fibers, resulting in debondings and voids. Such these voids have bad effects on the physical and mechanical properties of the final composite. For a better interfacial bonding with the matrix, natural fibers are chemically treated to remove these impurities (Wong, Zahi, Low, & Lim, 2010). Unsaturated polyester is a linear thermosetting polymer based on unsaturated and saturated acids/ anhydrides and diols, it is dissolved in unsaturated vinyl monomers such as styrene. The solution of unsaturated polyester with styrene monomer is known as UP resin. The unsaturation in the backbone provides sites for reaction with the double bonds in styrene monomer through peroxide initiators, leading to the formation of three-dimensional network (Malik, Choudhary, & Varma, 2000). UP is capable of producing very strong bonds with other materials; in addition, good toughness and crack stopping capability are particularly important (Willis & Masters, 2003). Unlike the compatible interaction between polar UP and polar natural fibers; nonpolar thermoplastics are not compatible with natural fibers, so an interface with poor adhesion can occur (Geottler, 1983). In order to enhance this week adhesion between fibers and thermoplastics, coupling agents are used in small quantities to treat the fibrous surface (Schneider & Brebner, 1985). Various studies on the application of natural fibers in polymer composites were widely reported; polyesterejute composite (Roe & Ansell, 1985), polyesterecoconut composite (Owolabi, Czvikovszky, & Kovacs, 1985), polyesterebananaecotton composite (Satyanarayana et al., 1983), polyesterestraw composite (White & Ansell, 1983), polyesterepineapple leaf
composite (Devi, Bhagawan, & Thomas, 1997), polyesterecottonekapok composite (Mwaikambo & Bisanda, 1999) and epoxyejute composite (Bledzki & Gassan, 1999) are some of these studies. WPC find advanced applications in construction materials and automotive accessories industry such as door panels, seat backs, headliners, package trays and dashboards. Other potential applications include door and instrument panels, package trays, glove boxes, arm rest and seat back panels (Vilay, Mariatti, Taib, & Todo, 2008). In this work, we prepared bagasseepolyester composites by different loading values of both untreated and alkali treated bagasse fibers. In order to understand the behavior of addition and modification of bagasse fibers, the flexural behavior was studied. Furthermore, water absorption and chemical resistance were investigated for the prepared composites.
2.
Materials and methods
2.1.
Materials
For fiber, bagasse between meshes of 0.5 and 1 mm was obtained as received as residue left over after milling of the local cane, Egypt. For the matrix, we used Crystic-126-Scott Bader unsaturated polyester resin with styrene content of 38% and viscosity of 400 cps. NaOH and HCl were supplied from EPRI lab. Methyl ethyl ketone peroxide and cobalt octoate supported from Sigma Aldrich. All ingredients and chemicals were used without further purification except some bagasse that underwent alkali treatment.
2.2.
Treatment of fiber
Alkali treatment was performed by soaking a part of bagasse in 5% NaOH solution for 60 min at room temperature. 10 g of the treated fibers were dispersed in 200 mL of 6.5 M sulfuric acid for 30 min at 60 C under vigorous stirring. The excess acid was then removed by 8000 rpm-centrifuge for 10 min. The treated bagasse was then filtrated and washed by distilled water to remove any additional chemicals. The washed fiber was heated at 70 C for 4 h to remove all moisture.
2.3.
Preparation of composites
Firstly, untreated (B) and alkali treated bagasse (AB) fibers were added to UP as fillers by 5, 10 and 15% (by weight). Curing
Please cite this article in press as: Naguib, H. M., et al., Effect of fiber loading on the mechanical and physical properties of “green” bagasseepolyester composite, Journal of Radiation Research and Applied Sciences (2015), http://dx.doi.org/10.1016/j.jrras.2015.06.004
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JRRAS171_proof ■ 25 June 2015 ■ 3/5 J o u r n a l o f R a d i a t i o n R e s e a r c h a n d A p p l i e d S c i e n c e s x x x ( 2 0 1 5 ) 1 e5
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reaction was then performed by addition of MEKP as 2% and cobalt octoate as 0.5%. The composite components and initiators were mixed well together then poured into molds. These molds were previously coated by grease to avoid any stacking with the composites. Before demoulding, samples were kept for 24 h at room temperature for curing followed by 3 h at 85 C for completely crosslinking reaction. Finally, the specimens were cooled at room temperature for 3 h and cleaned from any residual grease that appeared on the specimens.
2.4.
distilled water, maintained at room temperature and then removed from the water at the same time after 24 h. The surface water was wiped off with a dry cloth and the wet specimens were weighted immediately. For 2 h boiling water immersion; samples were placed in a container of boiling distilled water, maintained for 2 h and removed from the water. The specimens were then cooled by distilled water at room temperature for 15 min. After the surface water was removed, the specimens were weighted immediately. Water absorption percentage (DW%) was calculated from Equation (2);
Characterization DW% ¼
2.4.1.
Three point bending test
Three point bending behavior was conducted on BeUP and ABeUP composites according to the specifications of ASTM D 790-03 using 10 kN servo hydraulic testing machine that was run under displacement control mode at crosshead speed 2 mm/min. All tests were performed at room temperature and results were taken as the average value of five samples with dimensions of 180 35 9 mm. The specimen is deflected until rupture occurs in the outer surface of the test specimen or until a maximum strain of 5.0% is reached, whichever occurs first. The flexural strength and Young's modulus of elasticity of the composites were calculated using Equation (1). smax ¼
3Pmax L 2bh2
& E¼
L3 P 4bh3 D
(1)
where smax is flexural strength, E is Young's modulus of elasticity, Pmax is the maximum load, L is specimen span, b is specimen width, h is specimen thickness and (P/D) is the slope of the linear region of the obtained loadedeformation relationship.
2.4.2.
3
Wwet Wconditioned % Wconditioned
(2)
where Wwet and Wconditioned are respectively the weights of specimen after and before immersion.
2.4.3.
Chemical resistance
According to ASTM D 543-95, chemical resistance (CR) test was performed to specimens with the same dimensions of specimens of water absorption test against 10% HCl and NaOH solutions. The composite specimens were completely immersed in both fresh regents at room temperature for 24 h. They were free-suspended to avoid any contact with container walls or bottom. Specimens were then washed by distilled water to remove any additional reagents and weighed immediately after surface drying. The percentage of chemical resistance (CR%) against exposure to chemicals was calculated from Equation (3) as the average of three specimens; CR% ¼
Wexposed Wconditioned % Wconditioned
(3)
where Wexposed is weight after exposure to the chemical reagent and Wconditioned is weight before exposure.
Water absorption
Water absorption (WA) test was performed on BeUP and ABeUP composites following ASTM D 570-98 standards. Samples in the form of disks with 50.8 mm in diameter and 3.2 mm in thickness were weighted and results were calculated as an average value of three samples. For 24 h immersion; the conditioned specimens were placed in a beaker of
3.
Result and discussion
3.1.
Three point bending test
Fig. 2 shows the stressestrain curves (a) for BeUP and (b) for ABeUP composites. It is observed from Fig. 2(a) that increasing
Fig. 2 e Stressestrain curve (a) for BeUP and (b) for ABeUP composites. Please cite this article in press as: Naguib, H. M., et al., Effect of fiber loading on the mechanical and physical properties of “green” bagasseepolyester composite, Journal of Radiation Research and Applied Sciences (2015), http://dx.doi.org/10.1016/j.jrras.2015.06.004
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JRRAS171_proof ■ 25 June 2015 ■ 4/5
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J o u r n a l o f R a d i a t i o n R e s e a r c h a n d A p p l i e d S c i e n c e s x x x ( 2 0 1 5 ) 1 e5
Table 1 e The mechanical characteristic for BeUP and ABeUP composites. Sample ID
Strength (MPa)
Failure strain
Young's modulus (GPa)
Blank UP 5% BeUP 10% BeUP 15% BeUP 5% ABeUP 10% ABeUP 15% ABeUP
27.3 23.1 19.9 13.8 26.4 23.1 22.2
0.00735 0.00737 0.00633 0.00619 0.00892 0.00744 0.00916
4.39 3.44 3.73 3.01 4.42 4.57 3.40
Fig. 3 e Flexural strength for BeUP and ABeUP composites.
of bagasse content in BeUP composite leaded to reducing the flexural strength. From Fig. 2(b), the flexural strength increased by addition of more AB fiber. In addition, there is an increase in failure strain with ABeUP composite more than BeUP composites. Figs. 3 and 4 respectively represent the flexural strength and Young's modulus of elasticity for all BeUP and ABeUP composites. Young's modulus increased after alkaline treatment recording 4.42 and 4.57 GPa for 5 and 10% ABeUP composites compared with 4.39 GPa of neat UP, but it is still below UP at 15% ABeUP. The mechanical characteristics for BeUP and ABeUP composites are summarized in Table 1. After chemical treatment, the network structure of fibers was removed and new celluloses were generated with free hydroxyl groups that interact with polyester through strong fiberematrix interface. This leads to more uniform dispersion of applied stress and requires more energy for debonding of bagasseepolyester interface. It is clear that with alkali treatment of bagasse, enhanced mechanical behavior was achieved especially at 5 and 10% loadings. This improvement can be attributed to high strength and modulus of modified bagasse fibers and to the strong interfacial adhesion with polyester matrix.
3.2.
Water absorption
Fig. 5 illustrates water absorption percentages of BeUP and ABeUP specimens through immersion in water at room temperature and boiling water. It is clear that increasing of bagasse content leaded to increasing of water absorption percentage for the prepared composites within room
Fig. 4 e Young's modulus for BeUP and ABeUP composites.
temperature and boiling water immersion conditions, but water absorption achieved higher percentages with boiling water. Also, water absorption of ABeUP composites is higher than BeUP composites. After chemical treatment of bagasse surface, more surface area with more hydroxyl groups was exposed to absorb more moisture. The maximum water absorption after alkaline treatment was 0.023% and 0.041% for 15% ABeUP in cold and boiling water immersion. These values are acceptable compared with 0.6% water absorption that was reported by Kord (2012).
3.3.
Chemical resistance
Fig. 6 illustrates chemical resistance percentages of BeUP and ABeUP specimens against 10% HCl and NaOH solutions. Increasing of bagasse content resulted in weight gain of the exposed specimens. The obtained weight increase regarding the absorption of both reagents. After filling UP with AB, the composite absorption for chemicals was increased as noticed in water absorption test. It is clear that all BeUP and ABeUP composites did not lose weight and therefore they not seem as if any erosion occurred.
4.
Conclusion
In this work, “green” woodenepolymer composites based on bagasse-unsaturated polyester composites were prepared by addition of bagasse with 5, 10 and 15% by weight to the polyester resin. Chemical treatment of bagasse fiber was performed by firstly 5% NaOH and then with diluted HCL
Fig. 5 e Water absorption % for BeUP and ABeUP composites with cold and boiling water conditions.
Please cite this article in press as: Naguib, H. M., et al., Effect of fiber loading on the mechanical and physical properties of “green” bagasseepolyester composite, Journal of Radiation Research and Applied Sciences (2015), http://dx.doi.org/10.1016/j.jrras.2015.06.004
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JRRAS171_proof ■ 25 June 2015 ■ 5/5 J o u r n a l o f R a d i a t i o n R e s e a r c h a n d A p p l i e d S c i e n c e s x x x ( 2 0 1 5 ) 1 e5
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54
Fig. 6 e Chemical resistance % for BeUP and ABeUP composites against 10% NaOH and HCl.
solutions. The effect of this treatment on the mechanical and physical properties of the prepared composites was studied. Three point bending test indicated that addition of treated bagasse filler to polyester matrix began to enhance both of flexural strength and Young's modulus compared to untreated bagasse fiber. The chemical treatment of bagasse leaded to stronger interaction at fiberematrix interface compared to untreated fibers getting more uniform dispersion of applied stress and more energy for debonding of bagasseepolyester interface. Water absorption percentage with both room temperature and boiling immersion conditions was increased by addition of more content of bagasse to polyester matrix, especially after chemical treatment. In addition, all bagasseepolyester composites did not show any erosive character against NaOH and HCl solutions. Consequently, preparation of environmentally friendly woodenepolymer composites by filling of polyester matrix with chemically treated bagasse fiber achieved more enhanced characteristics than obtained by untreated bagasseepolyester composites. Such cheep composites can be used in car accessories, building construction and many other advanced industrial applications that can bear high loads in mild operating conditions.
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Please cite this article in press as: Naguib, H. M., et al., Effect of fiber loading on the mechanical and physical properties of “green” bagasseepolyester composite, Journal of Radiation Research and Applied Sciences (2015), http://dx.doi.org/10.1016/j.jrras.2015.06.004
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