Cotton bamboo fiber and properties of epoxy - Cotton bamboo composites

176 Journal of Chemistry, Vol. 45 (5A), P. 176 - 181, 2007 COTTON BAMBOO FIBER AND PROPERTIES OF EPOXY - COTTON BAMBOO COMPOSITES Received 16 August 2007 Tran Vinh Dieu, Nguyen Thi Thuy and Nguyen Anh Hiep Polymer Centre, Hanoi University of Technology summary Cotton bamboo fiber was prepared by steam explosion or mechanical method. Both methods included treated step in NaOH 1 N solution and the treated time was studied. The parameters of cotton fiber have been studied. The results of morphology and mechanical properties showed that the optimum treated time was 2.5 hours for the explosion-cotton fiber and 2 hours for the mechanical-cotton one. Cotton fiber reinforced epoxy composites (PC) have been developed with varying fiber content. Tensile and bending strength with variation of fiber content have been studied and they were found to be maximal for the fiber content of 38 wt%. With the same fiber content, the properties of the explosion-cotton composites were higher than those of the mechanical-cotton composites. For example, tensile strength was 77.1 MPa and showed 5.6% higher than that of mechanical-cotton composites; bending strength was 129.5 MPa and showed 12% higher than that of mechanical-cotton composites. Keywords: Bamboo, epoxy, composites, cotton. I - INTRODUCTION Although bamboo is extensively used as a valuable materials from times immemorial (because of its high strength and low weight), the studies on this fiber reinforced plastics are meager. Jindal [1] has reported the development of bamboo fiber reinforced plastic composites using Araldite (Ciba-CY 230) resin as matrix. A. Varada Rajulu and et al. [2] has reported the chemical resistance and tensile properties of short bamboo fiber reinforced composites using Araldite (Ciba-LY 5052) epoxy resin. In the present work, the cotton fiber and properties of epoxy-cotton bamboo composites have been developed. II - MATERIALS AND METHODS 1. Materials a) Matrix resin Epoxy resin (Ruetapox CY/160) with density 1.2252 g/cm3 and epoxy group content 24.8% was used for composites formulation. This resin was cured with Ruetadur HG (1.1898 g/cm3) as a hardener and dimethylbenzylamine (DMBA) as a catalyst. They were supplied by Bakelite, Germany. These chemicals were mixed at room temperature with the weight ratio [3] of 100 : 44.4 : 5.45 as shown in table 1. Table 1: Components of matrix resin Item Weight ratio Ruetapox CY/160 100 Ruetadur HG 44.4 DMBA 5.45 177 fiber b) Reinforcement Bamboo was purchased from Hoa Binh province of Vietnam. Cotton bamboo fiber was prepared by steam explosion or mechanical method. Both methods included treated step in NaOH 1 N solution. 2. Material preparation Prepregs prepared by impregnation of short bamboo fiber with matrix resin was filled in the mould and hot-pressed [3], at 110oC for 3 hours by the Gotech hydraulic machine (Taiwan). 3. Testing methods The tensile strength was measured on Instron-5582 100 KN machine (USA), according to ISO 527-1 at 5 mm/min of cross- head speed. The bending strength was measured on Instron-5582 100 KN machine (USA), according to ISO 178-1993 (E) at 5 mm/min cross-head speed. Diameter was measured on optical microscope HC-300Z1 (Nikon-Japan). III - RESULTS AND DISCUSSION 1. Cotton bamboo fibers and their parameters a) Explosion-cotton bamboo fiber The step to prepare explosion-cotton bamboo fiber was shown in the schema below: Raw bamboo was cut and split into bars. The bars were firstly exploded in steam explosion machine and then rolled into bamboo fiber by a twin rolling-mill (Japan). After rolling, bamboo was treated [4] by NaOH 1 N solution. The treated bamboo fiber was wet- mixed and then dry-mixed to obtain explosion- cotton bamboo fiber. The parameters of steam explosion were shown in table 2. Table 2: The parameters of steam explosion Time, minutes Temperature, oC Pressure, MPa Cycle 110 170 - 180 0.12 - 0.18 11 b) Mechanical-cotton bamboo fiber The step to prepare mechanical-cotton bamboo fiber was shown in the following schema: Raw bamboo was cut and split into bars. The bars were rolled by a twin rolling-mill (Japan) [4]. After rolling, bamboo was firstly treated by NaOH 1 N solution and then scratched into bamboo fiber. Treated bamboo fiber was wet-mixed and then dry-mixed to obtain mechanical-cotton bamboo fiber. c) The parameters of cotton bamboo fiber The ash content, moisture content and diameter of cotton bamboo fiber were measured by specific equipments and the results were shown in figure 1 and table 3. 24 12.5-14 9 26 9 13-15.5 0 10 20 30 As can be seen from figure 1, diameter of steam explosion-cotton bamboo fiber distributed from 9 µm to 24 µm and focused on 12.5 - 14 µm. The distribution range of mechanical-cotton Bamboo Rolling mill Sc ra tc h Alkali treatment Wet mixing Mechanical cotton fiber Dry mixing Bamboo Rolling mill A lk al i tr ea tm en t Wet mixing Explosion cotton fiber Dry mixing Steam explosion D ia m et er ,µ m Figure 1: The distribution of cotton bamboo fiber diameter Steam explosion fiber Mechanical fiber 178 bamboo fiber size was broader, from 9 µm to 26 µm. So the average diameter of steam explosion-cotton fiber was slightly smaller than that of mechanical-cotton fiber. The ash content of steam explosion-cotton fiber was larger than that of mechanical-cotton fiber. The moisture content of both cotton bamboo fibers were the same (table 3). Table 3: The parameters of cotton bamboo fiber Cotton bamboo fiber Steam explosion Mechanical Ash content, % 5.4 5.0 Moisture content, % 8 - 8.2 8 - 8.2 Diameter, µm 12.5 - 14 13 - 15.5 c) The morphology of cotton fiber surface. With the same magnification (2500 times), SEM image showed that the surface of mechanical-cotton fiber was rougher and harsher than that of steam explosion-cotton fiber. Furthermore, there were some thin scabs sticking to mechanical-cotton surface. It might be lignin and extraneous matter that were not removed. This was presented in figure 2. 2. The influence of treated time on properties of PC materials a) Steam explosion-cotton bamboo fiber Using steam explosion cotton fiber with different treated time to prepare PC materials, the mechanical properties of the PC with 44 wt% fiber were shown in figure 3. From this figure we can see, the treated time influenced remarkably the properties of PC. Generally, tensile strength increased significantly after treatment. The highest tensile strength was 68.9 MPa (at 3 hours of treatment) it was slightly higher (3.8%) than that of at 2.5 hours of treatment but noticeably higher (18.8%) than that of materials without fiber. However, with increasing treated time, the bending strength increased to definite value and then decreased with further increasing of treated time. The highest bending strength was 127.4 MPa and increased 51.7% compared to epoxy materials (EM) without reinforcing fiber. Figure 2: The SEM image of surface cotton fiber b) Mechanical-cotton bamboo fiber Using mechanical-cotton fiber with different treated time to prepare PC materials, the mechanical properties of PC with 38 wt% fiber were shown in figure 4. As can be seen from this figure, with different treated time, tensile and bending strengths increased to definite value at treated time of 2 hours and then decreased slightly with further prolonging of treated time. The tensile strength was 72.9 MPa and increased 25.7%, bending strength was 114 MPa increased 35.7% in comparison with EM. 3. The influence of cotton bamboo fiber content on properties of PC materials a) Steam explosion-cotton bamboo fiber The mechanical properties of PC materials with steam explosion cotton fiber content changing from 0 to 47 wt% were shown in figure 5. The presence of steam explosion cotton Steam explosion Mechanical 179 fiber caused obviously change in properties of PC materials. Especially, at 38 wt% cotton bamboo fiber content, the tensile strength was 77.1 MPa and increased 32.9%, bending strength was 129.5 MPa and increased 54.2% compared to materials without fiber. Figure 3: The influence of treated time on properties of PC materials Figure 4: The influence of treated time on properties of PC materials 77.1 58 0 20 40 60 80 100 0 35 38 44 47 Explosion cotton fiber content , wt% Te ns ile str en gt h, M Pa 129.5 84.1 0 30 60 90 120 150 0 35 38 44 47 Explosion cotton fiber content, wt% Be nd in g str en gt h, M Pa Figure 5: The influence of explosion-cotton fiber content on properties of PC materials 84.1 114 0 30 60 90 120 1 2 2.5 3 Treated time, hours PC-fiber EM-without fiber B en di ng st re ng th ,M Pa 58 72.9 0 20 40 60 80 1 2 2.5 3 Treated time, hours PC-fiber EM-without fiber Te ns ile st re ng th ,M Pa Treated time, hours 0 84.1 115.1 127.4 30 60 90 120 150 1 1.5 2 2.5 3 B en di ng st re ng th ,M Pa PC-fiber EM-without fiber Treated time, hours 58 68.9 66.3 0 20 40 60 80 1 1.5 2 2.5 3 T en si le st re ng th ,M Pa PC-fiber EM-without fiber 179 b) Mechanical-cotton bamboo fiber Similar to PC with steam explosion-cotton fiber, the properties of PC with mechanical- cotton fiber content changing from 0 to 47 wt% were presented at figure 6. In this figure we can see, with the presence of mechanical-cotton fiber, the mechanical-properties increased significantly. The PC with 38 wt% mechanical- cotton fiber have tensile strength 72.9 MPa, increased 25.7% and bending strength was 114 MPa, increased 35.6% compared to materials without fiber. 3. The influence of cotton fiber preparation method on properties of PC materials PC materials with two kinds of cotton bamboo fiber were prepared. The properties of PC with the same cotton fiber content (38 wt%) were shown in table 4. 72.9 58 0 20 40 60 80 0 35 38 44 47 Mechanics cotton fiber content, wt% Te ns ile str en gt h, M Pa 114 84.1 0 30 60 90 120 0 35 38 44 47 Mechanics cotton fiber content , wt% Be nd in g str en gt h, M Pa Figure 6: The influence of mechanics-cotton fiber content on properties of PC materials As can be seen from table 4, the mechanical properties of PC materials reinforced by steam explosion-cotton fiber were higher than that of PC with mechanical-cotton fiber. For example, tensile strength was 77.1 MPa, increased 5.8% and bending strength was 129.5 MPa, increased 13.6% compared to PC reinforced by mechanical-cotton fiber. Table 4: The influence of cotton fiber preparation method on properties of PC Method Tensile strength, MPa Bending strength, MPa Steam explosion 77.1 129.5 Mechanical 72.9 114.0 The SEM image of tensile-fracture surface of PC materials confirmed again this result. It showed that there were a lot of lignin and extraneous matter in PC with mechanical-cotton fiber. They decreased interfacial adhesion between fibers and matrix, agglomerated into micro-masses in matrix and made the structure of PC reinforced by mechanical-cotton fiber spongy. All this contributed to decreasing the mechanical-properties of the materials. We can draw the conclusion from table 4 and figure 7 that the steam explosion method showed better effects on cotton bamboo fiber than the mechanical one. IV - CONCLUSIONS 1. Cotton bamboo fiber was prepared successfully. Average diameter was 12.5 - 14 µm with steam explosion-cotton bamboo fiber and 13 - 15.5 µm with mechanical-cotton bamboo fiber. 2. The treated time for bamboo fiber was studied and the optimum treated time was 2.5 hours with steam explosion method and 2 hours with mechanical method. 3. The optimal fiber content was 38 wt% for both kinds of cotton bamboo fiber. With the 180181 Figure 7: The SEM image of tensile-fracture surface of PC materials same fiber content, the properties of PC reinforced by steam explosion-cotton fiber were higher than that of PC with mechanical-cotton fiber. References 1. Jindal U C. J Composites Material, Vol. 20, No. 9 (1986). 2. A. Varada Rajulu, S Allah Baksh, G. Ramachandra Reddy and K. Narasimha Chary. J Reinforced Plastics and Composites, Vol. 17, No. 17 (1998). 3. I. Hamerton. Recent Developments in Epoxy Resin, Shropshire: Rapra Technology, (2000). 4. Seema Jain, Rakesh Kumar. Materials and Manufacturing processes, Vol. 9, No. 5 (1994). PC-explosion cotton PC-mechanics cotton