Studies on mechanical, thermal properties and characterization of ABS-bagasse-MMT nano composites

Excerpt: The present study includes compounding of Acrylonitrile Butadiene Styrene (ABS) with Sugarcane Bagasse Powder (SBP ) and evaluation of the composite properties.

Abstract

The present study includes compounding of Acrylonitrile Butadiene Styrene (ABS) with Sugarcane Bagasse Powder (SBP ) and evaluation of the composite properties. The ABS / Bagasse composites has been prepared by the extrusion of ABS resin with 5%, 10%, and 15% wt% of Bagasse in a co-rotating Twin Screw Extruder. The extruded strands has been cut into pellets and injection molded to make test specimens. The optimum composition of resultant ABS / Bagasse composites were blended with organo nanoclay Cloisite 25A (1%, 3%, 5% and 7%) to evaluate the property modifications. The Tensile strength was slightly decreased by the addition of bagasse with ABS and by adding Nanoclay with ABS/Bagasse the tensile strength, tensile Modulus, flexural strength and flexural modulus were improved. The impact strength was lowered by the addition of Bagasse but improved by the addition of nanoclay with ABS /bagasse(5%) composites. The composites were characterized by SEM Technique. In DMA, the storage modulus increased with the addition of ABS with Bagasse. In ABS/Bagasse/Nanoclay composites, the storage modulus increased by the addition of Nanoclay. The thermal stability was decreased with the addition of ABS with Bagasse. In ABS/Bagasse/Nanoclay composites, the thermal stability was increased by the addition of Nanoclay (Cloisite 25A). ABS and Bagasse was optimized to 95% and 5wt % respectively due to lowering the impact strength and increase in brittleness characteristics. ABS/bagasse nano-composites may be Photo/Bio-degradable and eco friendly.

Key words : ABS, Bagasse, O-MMT, Melt blending, Mechanical properties, MFI, SEM

Introduction

DURING the last decade there has been a renewed interest in the natural fibre as a substitute for glass fibre, motivated by potential advantages of weight saving, lower raw material price and 'thermal recycling' or the ecological advantages of using resources which are renewable. On the other hand natural fibres have their shortcomings and these have to be solved in order to be competitive with glass fibres. Natural fibres have lower durability and lower strength than glass fibres. However, recently developed fibre treatments have improved these properties considerably.

Natural fibres have many significant advantages over synthetic fibres. Currently, many types of natural fibres have been investigated for use in plastics including flax, hemp, jute, straw, wood, rice husk, wheat, barley, oats, rye, sugarcane [1-10] and bamboo, grass, reeds, kenaf, ramie, oil palm , sisal, coir, paper mulberry, raphia, banana fibre, pineapple leaf fibre and papyrus. Thermoplastics reinforced with special wood fillers are enjoying rapid growth due to their many advantages; lightweight, reasonable strength and stiffness. Due to the light weight, high strength to weight ratio, corrosion resistance and other advantages, natural fibre-based composites are becoming important composite materials in building and civil engineering and automotive fields. Also, natural fibre based composites are environment friendly to a large extent.

Sugarcane Bagasse, an abundant agricultural lingocellulosic by product is a fibrous residue of canes stalks left over after crushing and extraction process of the juice from sugarcane. About 54 million dry tons of bagasse is produced annually throughout the world. Among the agro-industrial residue diverse, sugarcane bagasse is detached to be a residue widely generated in high proportions and contains cellulose ( 46 %), hemi-cellulose ( 24.5%), lignin (19.5%), fat and waxes (3.5%), ash (2.4%), silica (2%) and other elements (1.7%). Thus the utilization of cellulosic materials in production of polymeric composites is attractive particularly because of low cost and one method of production of value added products. Bagasse with PP[1, 4, 6], HDPE [3], PLA[5], Unsaturated Polyesters [8] and PVC [10] were reported in the literature. ABS with bagasse is not reported. ABS is widely used in Electrical and Electronic applications such as Electrical Housings, Radio housings, Calculators, Cell phones, remote controls etc. mostly for indoor applications. ABS is photodegradable and Bagasse is biodegradable. Hence ABS bagasse will be Photo /Bio Degradable. With nanoclay the ABS Bagasse nano composites will be environmentally friendly.

ABS is derived from acrylonitrile, butadiene, and styrene and the cost of producing ABS is roughly twice the cost of producing polystyrene, it is considered superior for its hardness, gloss, toughness, and electrical insulation properties. The combination of ABS and Sugarcane Bagasse Fibre is selected in order to evaluate the properties to be used in engineering application with cost reduction. Also, Nanoclay O-MMT (Organically modified Mont Morillonite, Cloisite 25A) was blended with ABS and Bagasse and their Mechanical and Thermal properties are evaluated.

Materials

Commercially available injection mouldling grade ABS (SD-0150) has been procured from Samsung Polymers Co. Ltd. and the properties of which are given in the Table 1(a). Sugarcane Bagasse fibres are collected from External sources and the reported properties are given in Table 1 (b). Nanoclay is procured from Southern Clay products Inc. and the reported properties are given in Table 1 ©.

Twin screw compounding

The ABS material was blended with sugarcane Bagasse fibre in three formulations such as 5%, 10% and 15% with compatibilizer glycerol using a twin screw extruder. The temperature of 160 to 195oC was used for melt blending. The extrudate was cut in the cutter and granules were made. These granules were injection moulded into tensile, flexural and impact specimen and test were conducted and evaluated as per ASTM standards.

The 5% Bagasse formulation with ABS was selected and cloisite 25A Nanoclay was blended in 1%, 3%, 5% and 7% ratio and four formulations of ABS- Bagasse-Nanoclay composite was prepared. These formulations were again injection moulded and tensile, flexural and impact specimens were prepared and the properties were evaluated

Result and discussion

Mechanical properties

Tensile properties (ASTM D 638, ISO 527)

The tensile strength and elongation test results of ABS / Bagasse composites at different filler loadings are given in Table 2. Tensile strength decreased from 47.64 to 46.08 MPa and elongation from 9.87 to 8.56% as the loading of Bagasse increases from 0.0 to 15 %. The reduction in tensile strength and elongation at break may be due to the lower Tensile strength of Cellulose Fibres than glass fibres. It was found that there is a marginal increase in tensile modulus with the increase in Bagasse loading. This may be due to interaction of polar ABS material with hygroscopic nature of filler which may contribute formation of hydrogen bond in between ABS and Bagasse fiber.

The tensile strength, tensile modulus and elongation test results of ABS / Bagasse (5%) / Nanoclay (Cloisite 25A) composites at different filler loadings are given in Table 3. Tensile strength increased from 47.20 to 50.58 MPa, tensile modulus from 540.52 to 900.23 and elongation decreased from 9.37 to 8.52% as the loading of Nanoclay (Cloisite 25A) with ABS and Bagasse increases from 0 to 7 %. The increase in tensile strength and modulus by the addition of nanoclay due to intercalation of nanoclay with ABS matrix. 5% bagasse was selected as optimum concentration for modification with nanoclay. At 10% and 15% loadings the ABS bagasse become more brittle and impact strength was much lowered.

Flexural properties (ASTM D 790, ISO 178)

The flexural strength test results of ABS/Bagasse composites at different filler loadings are given in Table 4 which show that the flexural strength decreased from 92.85 to 73.98 MPa.But the flexural modulus was increased. The flexural strength and Flexural modulus test results of ABS/Bagasse/ Nanoclay(Cloisite 25A) composites at different filler loadings are given in Table 5 which show that the flexural strength increased from 87.07 to 94.56 MPa. And flexural modulus from 2991 to 3301 MPa. The increase in flexural strength and modulus by the addition of nanoclay due to intercalation of nanoclay with ABS.

Impact properties (ASTM D 256 AND ISO 180)

The impact strength test results of ABS/Bagasse composites at different filler loadings are given in Table 6 As per the data, it was found that impact strength of ABS/Bagasse composites decreased as the loading of Bagasse increased from 5-15% since flexural modulus was higher (table 4). The impact strength test results of ABS/Bagasse/ Nanoclay(Cloisite 25A) composites are given in Figure 1. As per the data, it was found that impact strength of ABS/Bagasse/ Nanoclay(Cloisite 25A) was increased due to intercalation of nanoclay layers.

Physical properties

The physical properties like density, water absorption and surface hardness for ABS composites at different reinforcement loadings are depicted in Table7. In case of density (Table 7), there is only a marginal increase in density from 1.05 to 1.09 gm/cc with addition of Bagasse. Figure 2a-2c depicts density, surface hardness and water absorption of ABS and three formulations. The marginal increase in the density may be due to the bulky nature of Bagasse, which does not affect the material applications. The percentage of water absorption (Table 7) of ABS matrix has increased with increase in the Bagasse content due to polar and hygroscopic nature of Bagasse.. The surface hardness of ABS matrix decreased with increase in the Bagasse content. However, increase is only marginal even at higher percentage of Bagasse used. Figure 3a-3c depicts density, surface hardness and water absorption of ABS, Bagasse and Nanoclay formulations. (Table 8)

Melt flow index (ASTM D 1238, ISO 1133)

In case of MFI, the addition of Nanoclay(Cloisite 25A) reduction of MFI from 3.76 to 2.61 g/10 min. The decrease in melt flow is due to the high viscous nature of Nanoclay restrict the flow of melt. Table 9 depicts the values of melt flow index properties of ABS/Bagasse/ Nanoclay(Cloisite 25A) composites at different filler loadings.

Characterization

The Natural Fibre Composites and Nanocomposites are characterized by SEM, DSC & DMA, and TGA. The thermal decomposition temperature of the composites reduces with loading of Bagasse. The degradation temperature of ABS/Bagasse composite is lower than that of virgin ABS and higher than that of Bagasse. The Sugarcane Waste Fibres were also treated with alkali and then blended with ABS & MMT Nanoclay. The Mechanical & Thermal Properties were studied.

Thermogravimetric analysis

Table 10a shows the results of TGA thermograms of virgin ABS matrix, 5, 10 and 15% Bagasse filled ABS matrix. The thermal decomposition temperature of the composites reduces with loading of Bagasse. The degradation temperature of ABS/Bagasse composite is lower than that of virgin ABS and higher than that of Bagasse.

It is found that natural fibers show two (TGA curves) decomposition peaks. The first peak appearing at 300°C corresponds to the thermal decomposition of hemicelluloses and the glycosidic links of cellulose; the second one appearing at around 360°C is due to the thermal decomposition of α-cellulose Table 10b depicts the values of degradation temperature from the TGA data in presence of Nanoclay. The degradation temperatures were slightly increasing.

Dynamic mechanical analysis

In DMA, the storage modulus increased with the addition of ABS with Bagasse. In ABS/Bagasse/Nanoclay(Cloisite 25A) composites, the storage modulus increased by the addition of Nanoclay(Cloisite 25A). Table 11 depicts the values of storage modulus from the DMA data. The Tg of the ABS with Bagasse little lowered. The Tg of ABS, Bagasse and nanoclays were increased.

Scanning electron microscopy

The morphology of prepared composite has been investigated using scanning electron microscope (SEM). Figures (2a-2c) of SEM images of fractured surface of Impact specimen revealed uniform mixing of Bagasse in ABS resin matrix. Further, it was found that the mixing of Bagasse in polymer matrix was homogenized and without any sign of pull out with lower filler loading. Further studies of all composition of 1%, 3%, 5% and 7%, the nano particles are evenly distributed (Figures 3a-3d). Therefore, the mechanical properties are increased particularly improvement in the impact strength and with increase in flexural modulus.

Conclusion

ABS/Bagasse(5,10 &15%) composites and ABS/Bagasse(5%)/Nanoclay (1, 3, 5 & 7%) composites were prepared. ABS and Bagasse was optimized to 95% and 5wt % respectively due to lowering the impact strength and increase in brittleness characteristics. The Tensile strength was slightly decreased by the addition of bagasse with ABS and by adding Nanoclay with ABS/Bagasse the tensile strength, tensile Modulus, flexural strength and flexural modulus were improved. The impact strength was lowered by the addition of Bagasse but improved by the addition of nanoclay with ABS /bagasse(5%) composites. This is confirmed with the improved morphology through SEM micrographs. In DMA, the storage modulus increased with the addition of ABS with Bagasse. In ABS/Bagasse/Nanoclay composites, the storage modulus increased by the addition of Nanoclay. The thermal stability decreased with the addition of ABS with Bagasse. In ABS/Bagasse/Nanoclay composites, the thermal stability was increased by the addition of Nanoclay (Cloisite 25A). ABS/bagasse nano-composites may be Photo/Bio-degradable and eco friendly.

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Author Details

M.Pheer Mohamed and S.Soundararajan

Central Institute of Plastics Engineering & Technology Guindy, Chennai 600 032, India