Effect of Compatibilizing Agent on Mechanical Properties of Waste Paper and Gracinia kola Filled Low Density Polyethylene Composites

Transcription

1 International Journal of Innovative Scientific & Engineering Technologies Research 4(1):24-30, Jan-Mar SEAHI PUBLICATIONS, ISSN: X Effect of Compatibilizing Agent on Mechanical Properties of Waste Paper and Gracinia kola Filled Low Density Polyethylene Composites EZE, U. W 1 ; ISHIDI, E. Y. 1 ; UCHE, C. A 2 and OHANUZUE, C. B. C. 2 1 Department of Polymer Technology, Nigerian Institute of Leather and Science Technology, Zaria, Nigeria 2 Department of Polymer and Textile Engineering, Federal University of Technology Owerri, Imo State, Nigeria wilstyrene@yahoo.ca, ogbosoedith@gmail.com / , ABSTRACT The effects of compatibilising agent on mechanical properties of low density polyethylene/waste paper and gracinia kola composite were studied. The mechanical properties of the composite was characterised using an Instron machine. Four levels of filler loading; 5, 10, 15 and 20 wt % and a constant amount of compatibilizing agent of 0.2wt % were used for the composite fabrication. The tensile strengths, extension at break of the composites decreased as the filler loading increased, but the modulus was significantly improved as filler loading increases and with the compatibilizing agent. Both the notched charpy impact strength and brinell hardness test increased significantly with the addition of compatibilizing agent. Study revealed that the positive effect of the compatibilizing agent resulted in a stronger interfacial bonding. Keywords: Compatibilizing agent, Mechanical properties, LDPE Composites. INTRODUCTION Modification of polymers with an organic material to produce a polymer composite is a commonplace in the world of modern plastics. Recently, composite materials have successfully substituted the traditional materials in several light weight and high strength applications. The reasons why composites are selected for such applications are mainly their high strength-to-weight ratio, high tensile strength at elevated temperatures, high creep resistance and high toughness.[1,2] Thus, research on the development of composites prepared using various organic materials is being actively pursued. Among the possible alternatives, the development of composites using lignocellulose or agro-wastes materials as reinforcing fillers and thermoplastic polymers as matrixes is currently at the centre of attention. These composites would resolve environmental problems [3] and offer the possibility of producing products having a range of different physical properties and functions. Composites are materials that comprise strong load carrying material (known as reinforcement) imbedded in weaker material (known as matrix). Reinforcement provides strength and rigidity, helping to support structural load. The matrix or binder (organic or inorganic) maintains the position and orientation of the reinforcement. Significantly, constituents of the composites retain their individual, physical and chemical properties; yet together they produce a combination of qualities which individual constituents would be incapable of producing alone. However, the mechanical properties of these composites are somewhat lower than their synthetic counterparts due to the hydrophilic properties of the filler. Poor interfacial bonding between the filler materials and the hydrophobic matrix polymer causes the mechanical properties of the composites to be 24

2 lowered. Comprehensive studies are currently being performed on polyolefin such as polypropylene and polyethylene and various natural reinforcing fillers, in conjunction with various chemicals that could affect the interface [4, 5].This problem can be alleviated by the use of compatibilizing agents like maleic anhydride graft-polyethylene.(mape). This compatibilizing agent becomes chemically linked with the hydrophilic fillers on one side, while facilitating the wetting of the hydrophobic polymer chain on the other side. In other words, the MAPE have dual characteristics in that it possess both the hydrophilic and hydrophobic properties needed for them to adhere well with the fillers and matrix. The strong interfacial bonding strength obtained by improving the compatibility between the hydrophilic filler and hydrophobic matrix polymer can improve the physical, mechanical and thermal properties of the composite system [6,7,8]. The purpose of the current research was to examine the effect of the compatibilizing agent MAPE and fillers loading on the interfacial bonding between hydrophilic filler and hydrophobic matrix polymer. EXPERIMENTAL METHODS Materials Matrix Polymer The thermoplastic polymer, low-density polyethylene (LDPE), WA type virgin a product of Exxon Mobile in the Kingdom of Saudi Arabia, was obtained from Ceeplas Industries, Aba, Abia State. Reinforcing filler The reinforcing fillers was a used waste paper (old newspaper) and bitter kola (garcinia kola) were obtained from local market. The particle sizes of both fillers were reduced to 250 microns. Compatibilizing Agent The compatibilizing agent; Polyethylene-graft-Maleic Anhydride was made by Exxon Mobile Limited, Sigma ALDARICH chemical company USA. Silicone Oil The silicone oil used was a product of Vickers Laboratory Limited, Burley-in-Warfedale West Yorks, England, obtained from Chemisciences (Nig.) Ltd. Owerri, Imo State, Nigeria. Sample Preparation Waste paper was shredded and soaked in water for three days. It was then removed from the water and soaked in 3.5% w/v sodium hypochlorite for another three days for bleaching. It was washed and pounded using pestle and mortar. After pounding it was then sun dried for two days; there after grinded using electrical powered plate grinding machine to achieve fine particles size. The bitter kola was kept at room temperature for two days. The material so obtained was dried in an oven at a temperature of 100 C for four days. After drying them they were de-hulled and ground. The fabrication of the composite samples was carried out using the injection moulding technique. Separate sets of composites were prepared using the Low Density polyethylene, waste paper and bitter kola as filler. The filler loadings were varied from 0 to 20% weight. Some samples were prepared with a constant weight of 2% of the Polyethylene-graft-Maleic Anhydride while others were prepared without the Polyethylene-graft-Maleic Anhydride while the silicon oil was added to every sample produced. The formulations for the composites fabrication are shown in Table 1. Table 1: Formulations for the filled low density polyethylene composites Ingredients Content LDPE 200g Filler 0-20% MAPE 2% Silicon Oil 4ml 25

3 Measurement of Tensile Properties The tensile tests were conducted according to ASTM - D 638 [9] with a Universal Testing Machine (Instron). 120mm x 20mm x 3mm dumb bell specimen was cut from the moulded sheets. The tests were performed at a crosshead speed of 100 mm/min and at room temperature. The various values of tensile strength, extension at break, modulus were recorded. Impact Resistance Measurement The notched chapy impact strength tests were conducted according to ASTM D [2] at room temperature. Each value obtained represented the average of three samples. Hardness Measurement A Tensometer W type by Monsanto was used to perform Brinell hardness test. The test samples were cut in rectangle shapes of 50mm by 30mm and placed in the machine. The values obtained represented the average of three samples. RESULTS AND DISCUSSION Effect of Compatibilizing Agent on Tensile Properties of the Fabricated Composites. The results for tensile properties of waste paper/bitter kola filled LDPE composites of samples with compatibiliser and without compatibilised are shown in Figure 1 and 2. Fig 1: The plot of Tensile Strength against Percentage filler loading for Waste paper. Fig 2: The plot of Tensile Strength against Percentage filler loading for Bitter kola. The tensile strength decreased with increasing filler loading due to the poor interfacial bonding between hydrophilic filler and hydrophobic matrix polymer. This weak bonding between the hydrophilic filler and the hydrophobic matrix polymer causes decreased tensile strength. Previous researches show that the 26

4 tensile strengths of the composites decreased with increasing filler loading [10-11]. In this study the addition of maleic anhydride-graft-polyethylene made the tensile strength of bitter kola and waste paper filled composites to be higher than that of bitter kola and waste paper without MAPE. The compatiblizing agent has a positive effect on the tensile property because they strengthen the interfacial bonding between the filler and the matrix polymer. Thus, the maleic anhydride-graft-polyethylene coupling agent with a structure similar to the matrix is grafted into the filler which is helpful to improve interfacial adhesion. The compatibilizing agent chemically bonded with hydrophilic filler and blended by wetting in the polymer chain. The incorporation of waste paper/bitter kola fillers into the LDPE matrix resulted in reduction of extension at break of composites as shown in Figures 3 and 4. The composites produced with MAPE showed a decrease in extension when compared to those produced without MAPE. The coupling agent improves the strength of the composite thus indicating interference by the coupling agent in the mobility of the matrix, which is, reducing the ductility of the polymer matrix. The waste paper/bitter kola fillers were combined with thermoplastics through covalent bonding or strong interfacial bonding and the interface was strengthened with coupling agents, thus resulting in a stronger interfacial structure. This however, resulted in an increase in brittleness of the composite. Fig. 3 The plot of Extension at Break against Percentage filler loading for Waste paper. Fig. 4 The plot of Extension at Break against Percentage filler loading for Bitter kola. The increase in Young s modulus with filler loading clearly indicates the ability of the waste paper/bitter kola fillers to impart greater stiffness to the LDPE composites as shown in Figures 5 and 6. At a similar filler loading, Young s modulus of the compatibilized LDPE composites is higher than that of uncompatibilized LDPE composites. The anhydride groups present in the coupling agent (maleic 27

5 anhydride-graft-polyethylene) can covalently bond to the hydroxyl groups of the filler surface. Any maleic anhydride that has been converted to the acid form can interact with the fibre surface through acid base interactions [12]. Fig. 5 The plot of Modulus of Elasticity against Percentage filler loading for Waste paper. Fig. 6 The plot of Modulus of Elasticity against Percentage filler loading for Bitter kola. Chapy Impact Strength Test The chapy impact test method was conducted at room temperature. The notched specimens were tested and the results obtained are as shown in Figures 7 and 8. The results obtained indicated increase filler loading which resulted to the stiffening and hardening of the composite thereby increasing the impact energy of the composite. This shows that the resistance to impact loading of waste paper/bitter kola reinforced low density polyethylene composites improves with increase in filler loading. The compatibilizing agent has a significant effect on the impact strength because they strengthen the interfacial bonding between the filler and the matrix. Strong adhesion between the filler and matrix interface can cause better stress transfer from the matrix to the filler and this leads to higher impact strength. Without the chemical modification, there is simply adhesion of the polymer to the filler through weak bonding, that is, Van der Waals or induction interactions. 28

6 Fig 7: The plot of Impact Energy (J/m 2 ) against percentage filler loading for Waste paper filler Fig 8: A graph of Impact Energy (J/m 2 ) against Percentage filler loading for Bitter kola filler Brinell Hardness Test The waste paper/bitter kola composites produced using the compatibilizing agent exhibits a higher value of hardness compared to that produced without the compatibilizing agent as shown in Figure 9 and 10. This indicates that the compatibilizing agent may react with the LDPE matrix to produce a closer packed structure, which could lead to an increase in the hardness of the composites. The backbone structure of the coupling agent also affected interfacial bonding strength of the resultant composites thereby resulting in dynamic increase in the hardness of the composites. Fig 9: A graph of Brinell hardness test against filler loading for Waste paper 29

7 Fig 10: A graph of Brinell hardness test against Percentage Filler loading for Bitter kola filler CONCLUSION As the filler loading increased, the composite made without any compatibilizing agent showed decreased tensile strength and more brittleness, but the mechanical properties greatly improved by incorporating the compatibilizing agent. The poor interfacial bonding between the filler and the matrix polymer causes the composites to have decreased tensile strengths, but the presence of Maleic Anhydride graft-polyethylene (MAPE) increased the tensile strength and Young s modulus but decreased the elongation at break of waste paper/bitter kola filled LDPE composites. The compatibilizing agent also made a positive effect on Chapy impact strength and Brinell hardness tests. REFERENCES [1] Yang H-S, Kim H-J, Son J, Park HJ, Lee BJ, Hwang TS. Rice-husk flour filled polypropylene composites; mechanical and morphological study. Compos Struct 2004;63(3): [2] Mueller D.H and Krobjilowski A, New Discovery in the Properties of Composites Reinforced with Natural Fibers, Journal of Industrial Textiles, 33(2), 2003, pp [3]. Lee SY, Yang HS, Kim HJ, Jeong CS, Lim BS, Lee JN. Creep behavior and manufacturing parameters of wood flour filled polypropylene composites. Compos Struct 2004;65(3 4): [4] Hattotuwa G, Premalal B, Ismail H, Baharin A. Comparison of the mechanical properties of rice husk powder filled polypropylene composites with talc filled polypropylene composites. Polym Test 2002;21(7): [5] Lai S-M, Yeh F-C, Wang Y, Chan H-C, Shen H-F. Comparative study of maleated polyolefins as compatibilizers for polyethylene/wood flour composites. J Appl Polym Sci 2003;87: [6] Ismail H, Nizam JM, Abdul Khalil HPS. The effect of a compatibilizer on the mechanical properties and mass swell of white rice husk ash filled natural rubber/linear low density polyethylene blends. Polym Test 2001;20(2): [7] Yang HS, Kim HJ, Park HJ, Lee BJ, Hwang TS. Water absorption behavior and mechanical properties of lignocellulosic filler-polyolefin bio-composites. Compos Struct 2004;72 (4): [8] Yang HS, Wolcott MP, Kim HS, Kim HJ. Thermal properties of lignocellulosic filler thermoplastic polymer bio-composites. J Thermal Anal Calorim 2004;82(1): [9] American Society for Testing and Materials. Annual book of ASTM standards, 100 Barr Harbor Dr.,West Conshohocken, PA 19428, [10] Lilholt H and Lawther J.M, Comprehensive Composite Materials, chapter 1.10, 2000, Elsevier Ltd. [11] Li Q, Matuana LM. Surface of cellulosic materials modified with functionalized polyethylene coupling agents. J Appl Polym Sci 2003;88: [12] Bikiaris, D., and C. Panayiotou (1997). LDPE/starch blends compatibilized with PE-g-MA copolymers. J. Appl. Polym. Sci. 70: