ABSTRACT: The main objective of this research is to develop new composite material and evaluate the physical and mechanical properties of particleboards made of Bamboo and Sesame stalk which is grown in the lowland of Ethiopia bonded with urea-formaldehyde resin. The composite material was prepared by crushing bamboo and sesame stalk and blended with 14.5% of urea-formaldehyde, 3% of hardener, 1.5% of paraffin wax and 2.5% of boric acid through hand mixing from 5 to 8 minutes and press within a temperature 120 oC to 175 oC for 3 minutes.
Nine types of particleboards were produced with their proportions through Taguchi design of experiment (L9) approach. Minitab 16 software package is used for experimental result analysis. Physical and mechanical properties including internal bonding strength, modulus of rupture, modulus of elasticity, Moisture content, water Absorption, thickness swelling, and fire retardant tests were conducted. The experiment result shows Internal bonding; Water Absorption, Modulus of Elasticity, Board density and Thickness Swelling are above the minimum requirement, however, Moisture contents, Modulus of rupture are significantly decreased from the standard.
The optimum factors combination are Bamboo to sesame ratio (2:1), pressure (25 N/mm2) and particle size [0.5 ” 1.5 for surface layer and 1.5 ” 2.5 for core layer]. Fire retardation test, boric acid treated particleboard was reducing its flammability by 35 % from the untreated board.Keyword: – Particleboard, Bamboo and Sesame stalk, Urea-formaldehyde, Composite, Resin. I. INTRODUCTIONThe composite materials are materials which made through combining of two or more materials usually they that have very different properties. The two materials work together to give the composite that has unique properties. But, regarding the composite, we can easily tell the different materials separately as they do not dissolve into each other. The main advantage of composite materials is, they are light in weight as well as strong. It also provides design flexibility because many of them can be molded into complex shapes. Composite materials can be titled by reinforcement and the matrix material. According to the type of matrix materials, it is categorized into A) Metal Matrix Composite material, B) Ceramic Matrix Composites, and C) polymer matrix composite material. Particleboard is one of the most common wood-based composite materials for decorating materials because of its desirable properties like low-density, sound absorption, and excellent machining properties.. It is categorized into three based on their density of fiber particle. A) Low-density fiberboard. B) Medium-density fiberboard. C) High-density fiberboard. Particleboard is produced in densities ranging from around 590 kilograms per cubic meter (kg/m3) to 800 kg/m3). This study has been considered to use Ethiopian lowland bamboo and sesame stalk because it is abundant accessibility none used (sesame stalk) materials in Ethiopia. This research generally conquer to replace of eucalyptus via bamboo and sesame stalk that have been studied by conducting subsequent tests of physical and mechanical properties through the series follow up of the standard specimen preparation procedures. Bamboo is a naturally occurring composite material which grows abundantly in most of the tropical countries. It is considered a composite material because it consists of cellulose fibers embedded in a lignin matrix. It has also been widely used in building applications, such as flooring, ceiling, walls, windows, doors, fences, housing roofs, trusses, rafters, and purlins; it is also used in construction as structural materials for bridges, water transportation facilities. In Ethiopia, bamboo was found in to two broad classes based on its growth location. (a) Ethiopianhighland bamboo (Yushania alpine. It is found around Amhara region, Oromiya region,(bale, westershowa, Aris) SNNPR, (sidamo, North Omo, gurage). (b)Ethiopian lowland bamboo (Oxytenantheraabyssinica). It is abundantly found in North Tigray, (tselemtie, tahtay-Adiabo, welkayt and humera) and from BenishagulGumuz region of Ethiopia. For this study, it was focused on the lowland bamboo (Oxytenantheraabyssinica) collected from TigrayTahtay-adiabo)[4,5,6]. Figure 1: a) Ethiopian highland bamboo (Amhara, injibara), b) Ethiopian lowland bamboo (Tigray, (shire: TahtayAdiabo), c) Traditional harvested of sesame stalk (Sesamumindicum L)Sesame (SesamumindicumL):- is the one and the oldest oilseed crops and is cultivated in Africa, Asia and South America (Zhang et al., 2013). Sesame production was started in India and the Middle East since 4000 years ago. More than 50% of the world’s sesame production was from India, Myanmar, Ethiopia, China, and Nigeria during 2011. And Ethiopia is one of the top 5 world’s producers of sesame seed [7,8]. Sesame stalk is abundantly available in the North West Tigray particularly in welkait and Humera, the largest production farmland in northern Ethiopia. The stalk of the sesame is not being used for any purpose; rather, they use wood for house cooking and baking [9,10].The objective of the research is to develop new composite material using urea formaldehyde as matrix and bamboo – sesame stalk particles as reinforcement for particleboard Application.The specific objective of the study is to investigate mechanical and physical properties of sample board such as internal bonding (IB), Modulus of Rupture (MOR), Moisture content, water absorption, fire resistance, thickness swelling of the sample and to compare it properties based on the results obtained from the experiment with the standard.II. MATERIALS AND METHODS I. MATERIALS The materials utilized todevelop these composite materials from bamboo ” sesame stalk with urea-formaldehyderesin for particleboard are: Reinforcement (bamboo and sesame stalk fiber), Resin (urea-formaldehyde), Hardener (NH4Cl), emulsion agents (paraffin wax) and fire retardant agent (Boric acid H3BO3).II. METHODS a) Particle Preparation: -The log of Bamboo and sesame stalk has been crushed separately within 40 to 60% of moisture contents by chopper and flaker machine . The produced particles were screened using Laboratory sieves to remove the oversize, and for categorized within the required particle size. The particles passed through up to 3.5 mm sieves were used for core and surface layer accordingly.b) Design of experiment (DOE):The experimental design of the research would be performed to identify better result through bamboo and sesame stalk ratio (BR: SSR), pressure difference (PD) and Size difference of particle (PZ) of the reinforcement material using Taguchi orthogonal array method. In this study, the experiment has four variables in three different settings. A full factorial experiment would require 34 = 81 experiments[12,13]. But in here, a Taguchi experiment with an L9 (34) orthogonal array would be conducted (9 tests, 4 variables, 3 levels) with three trials listed in table 1.Table 1: Experimental factors and their levels Table 2: Standard L9 orthogonal array with factors ratio c) BOARD MANUFACTURING PROCESS: Procedures 1. Collecting the raw materials from the area where it is found. 2. Fabricate the coil heater manual platen from different thickness mild steel and fiberglass to hold the temperature. 3. Crushed, sieve and categorized the raw materials (bamboo & sesame stalk) accordingly the required particle size. 4. Take the flake sample and conduct physical properties tests like moisture of the flake (ensure 3 ” 5 %) and weighting its mass for determination of bulk density. 5. The blending the particles with the resin (urea-formaldehyde) and the necessary additive accordingly their proportion.6. Develop the sample particleboard through hot pressing with a temperature range of C to 175o C for 3 minute pressing time and conditioned at room temperature. 7. Perform experimental investigation of the mechanical and physical properties and compare with the standard board. Figure 2: The fabrication process the sample particleboard Figure 3: Process of flow diagramIII. RESULTS AND DISCUSSIONBased on the Taguchi Design of experiments L9 (34) Orthogonal array the experiments were performed on a particleboard with the standard size using ASTM standard method (D1037-99, ASTM, 1999). The physical and mechanical properties listed in experimental setup evaluated under the designed conditions in terms of the following measured response parameters like internal bonding (IB, N/mm2), flexural strength (MOR, Mpa), Moisture contents of board (MC,%), Water absorption (WA/24 hrs., %) and thickness swelling (TS/24 hrs, %). The results were evaluated through Analysis of Variance (ANOVA) calculations, the percentage of contribution of each control factor influencing the above-measured parameter and show the optimal parameter combination of the process listed in table .3Table 3: Summary of mechanical and physical properties test result for particleboard made from bamboo and sesame stalk Based on ANOVA (ANOVA can identify the product or process parameters that are statistically significant)the parameters that the higher observed value shows the better board performance in the case of Internal bonding (IB), (MOR), and Board density (BD) and it is Called as Higher the better characteristics. But the lower observed value represents the better board performance, such as MC (%), water absorption (WA), thickness swelling (TS) are called as Lower the Better characteristics.a) DISCUSSION ON INTERNAL BONDINGThe greater average S/N ratio corresponds to the maximum IB. that the larger observed value represents the better board performance in terms of internal bonding. Optimal combination of control factors for internal bonding strength was found 2:1 BR: SSR with 25 Mpa press pressure and second level particle size (D2) shown in figure 5. From delta rank Particle size is the most significant control factors, and it has 83.90% percentage of contribution while weight percentage of sesame stalk is less significant factors that have3.72%. Figure 4: internal bonding testing process: (a) sample before testing. (b) Sample boards after gluing. (C) Testing sample on the universal testing machine. (d) Sample after testing Figure 5: Larger the better factor combination for internal bonding (IB)b) DISCUSSIONS ON FLEXURAL STRENGTH The signal to noise ratio for bending strength of the board is observed from figure (6b) that the factors point impliesthat the larger value represents the better board performance for a particular response parameter. Therefore the optimal combination of control factors is found 2:1 for BR: SSR with 15 Mpa press pressure and D2 particle size. From delta rank of the response parameter (flexural strength)particle size is the most significant control factor which has47.39%percentage of contribution whereas the pressing pressure is less significant factors (5.38%) in affecting the bending strength of the particleboards. Figure 6: flexural strength testing Figure 7: larger the better S/N ratio factor combination for flexural strength.c) DISCUSSION FOR BOARD MOISTURE CONTENT From the graph shown below (figure 7b), the lower observed value represents the better board performance with respect to moisture uptakes. Among the variables, particle size (pz) is the most significant control factors with a percentage of contribution (63.97%), whereas the weight percentage of sesame stalk (SSR) is less significant in affecting (4.05%) of moisture uptakes property of the particleboards. The optimal combination of variables for board moisture content is 2:1 for BR: SSR with 25 Mpa of pressing load and second level of particles size (D2) shown in figure (7b). Figure 8: Sample board for moisture content testing, Figure 9: Signal to noise ratio for Moisture contentd) DISCUSSION ON WATER ABSORPTION For water absorption property of the particleboards, the lower results are the desirable response. For the lower value of the response, the optimal combination of variables are Bamboo to sesame ratio (2:1), press pressure (250 Mpa) and size of particles (D2 = [0.5-1.5 mm for the outer layer and 1.5-2.5 mm for core layer)shown in figure (8b). in the water absorption property weight percentage of bamboo is the most significant control factors with a contribution (48.24%) while the weight percentage ofsesame stalk ratio is less significant factors in affecting the water absorption property with (5.87%) of the particleboards. Figure 10: Water Absorption test after 2 and 24 hours soaking, Figure 11: Signal to noise ratio for water absorptione) DISCUSSION ON THICKNESS SWELLING According to ANOVA results, the graphs show that best values of parameters are Bamboo to sesame stalk ratio (3:2), pressure (15 Mpa) and size of the particle (D3 = [1.5 ” 2.5 mm for surface layer and 2.5 ” 3.5 mm for core layer) shown in figure 9b. this combinationlay on board #8 in orthogonal array L9 table and the result of Signal to Noise ratio, that the smaller value represents the better particleboard performance in dimension stability. Therefore the delta value shows that pressure difference is the most significant control factors which are 50.39% of the contribution, whereas the particle size (pz) is less significant (3.20%) in affecting of thickness change property of the particleboard. Figure 12: Thickness swelling testing Figure 13: S/N ratio for thickness swellingIV. DISCUSSION ON FIRE RESISTANCEThe test was accomplished by exposing the sample board for 365+5oC heated flame. Kerosene flame was used as the heat source and the heating flame was applied for 10 min. The test was basically conducted in terms of measuring weight loss of the board within a given time. During the test, the mass of panels measured and recorded before and after burned. Flame penetration and spread through the board caused by weight loss.These newly developed materials (bamboo and sesame hybrid composites) present a significant improvement in their flammability properties. From the experiment, it was shown that boric acid (H3BO3) can effectively reduce the flammability (almost 34.79 %) of bamboo and sesame discrete particleboard urea formaldehyde composites. It is because of due to the presence of the flame-retardant chemicals depositing on the fibers of the boards shown in figure 8. Figure 14: Fire-retardant testingV. CONCLUSIONFrom the exponential results ofsample board made from bamboo ” sesame stalk reinforced urea formaldehyde, the following conclusions are formulated. The lowland bamboo and sesame stalk hybrid with a ratio of [2:1] is a good candidate for the production of particleboard. The results show that the internal bonding strength, water absorption and thickness swelling highly depending on particle size (i.e. where the size of particle decrease, IB increases while Water absorption and thickness swelling decrease which is desirable. However, MOR and MOE decrease as particle size decreases which is undesirable. Except for water absorption and thickness swelling, increase in MOR, MOE, MC, and BD was observed with an increase in pressing pressure from 15 ” 25Mpa. As learned from the ANOVA results, particle size shows the highest influence and weight percentage of reinforcement phases show the least influence on most response parameters. 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