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Preparation of Polymer Composites Using Natural Fiber and Their Physico-mechanical Properties

Husna P. Nur
Fiber & Polymer Division, BCSIR Laboratories, Dhaka-1205

M. Akram Hossain
Fiber & Polymer Division, BCSIR Laboratories, Dhaka-1205

Shahin Sultana
Fiber & Polymer Division, BCSIR Laboratories, Dhaka-1205 and

M. Mamun Mollah
Department of Chemistry, National University, Dhaka, Bangladesh.

Abstract/ Executive Summary:

Use of natural fiber as reinforcing material is the latest invention of polymer science in order to get higher strength with lower weight composite materials having several applications. In this present investigation banana fiber, a natural fiber, is used as the reinforcing material. Low density polyethylene (LDPE)-banana fiber reinforced composites were prepared using both untreated and bleached (treated) banana fiber and LDPE with 7.5, 15, 22.5 and 30% weight content of fibers by using compression molding technique. Physico-mechanical properties (e.g. tensile strength, flexural strength, elongation at break, Young's modulus) of different types of prepared composites were characterized. From this study it is observed that all these values have augmented up to a definite percentage. The tensile strengths and flexural strengths of the composites increased up to 22.5% fiber addition then started to decrease gradually. Young moduli of the composites increased with the increase of fiber addition. Water absorption also increased with the weight of the fiber. Whereas elongation at break decreased with increasing fiber loading. Mechanical properties of bleached banana fiber-LDPE composites were slightly higher than the untreated banana fiber-LDPE composites. Compared to virgin molded LDPE both tensile and flexural strengths and Young moduli of these LDPE-banana fiber composites were significantly higher. All the variable properties like tensile strength, flexural strength, and water absorption capacity showed a very significant role in these polymer composites.

Keywords: Banana fiber, LDPE, Composite, Tensile strength, Flexural strength

Location: Fiber & Polymer Division, BCSIR Laboratories, Dhaka

Start Date:

End Date:

Program Area: Variety and Species

Non-commodity: Performance

Objectives:

The main goal of this research work was to fabricate different composites and to investigate the performances of the prepared composites by determining their physico-mechanical properties (e.g. tensile strength, flexural strength, elongation at break, Young's modulus etc.).

Methodology:

Collection and separation of banana fiber from their plants: Banana trees were collected from the village of Naynabad in the district of Narayangonj. The fresh part of the banana trees were then cut into manageable size and kept under water, where microorganisms were available, so that they rot quickly. Within 20-22 days the trees were completely rotten and the fiber became loose from the other part of the tree. The fiber was then washed several times with fresh water and then the fiber bundles were sun dried. Raw materials: The main raw materials used for the sample preparation were Low density polyethylene (LDPE) and banana fiber. LDPE is collected from local market. Banana fiber was used as reinforcement agent. Banana fibers were chopped into small pieces (2-3 mm average), with the help of scissors. The sized banana fibers were manually agitated to make the fibers loose from each other and were dried in an oven at around 105^o C for 24 hours. Light bleaching of banana fiber: For light bleaching of banana fiber, fibers were taken in water solution containing 6% hydrogen peroxide, 4% sodium hydroxide, 4% sodium silicate, 2% soda ash and 1% soap followed by 24 hours storing at room temperature (Choudhury, 2006). Here hydrogen peroxide acts as the main ingredient for bleaching. Finally the bleached banana fiber was washed with water and dried in an oven at around 105^o C for 24 hours. Composite fabrication and mixing of fiber and LDPE: Different formulations of composites were prepared using LDPE and banana fiber. The chopped banana fibers (untreated and bleached) and LDPE were mixed homogeneously to get improved quality products. Blender was used to mix fiber and matrix homogeneously where blending was done for one minute at 400 rpm for each specimen. Mechanical testing of the composites: In order to investigate the mechanical properties of the prepared composites the following (a) tensile and (b) flexural tests were performed using an universal tensile testing machine (capacity:10 KN, Hounsfield) at a crosshead speed of 1 mm/min. a. Tensile test: The static tensile tests of the composites were performed according to ASTM D 638-01 (2002). The test specimens were prepared as per ASTM D 638-01 (2002) and each test was performed until tensile failure occurred except 100 % LDPE composite. Five specimens of each composition were tested and the average values were reported. b. Flexural strength: Flexural specimen preparation and tests was performed according to ASTM D 790-00 (2002). Three point flexural test set up was used to perform this test. Five specimens of each composition were tested and the average values were reported. c. Water absorption test: Water absorption tests of the composites were conducted according to ASTM D570-99 (2002). The samples were dried in an oven at 105⁰ C for about 2 hrs, cooled in a desiccator and immediately weighed to the variation of 0.0001 g using Denver Instron balance. The dried and weighed samples were immersed in boiling water for about 2 hrs as described in ASTM D570-99 (2002). Excess water on the surface of the samples was removed and the weights of the samples were taken. Five specimens of each composition were tested and reported the average result. The percentage increase in weight after immersion in water was calculated as follows: Increase in weight,

Source of Information: Bangladesh J. Sci. Ind. Res. 45(2), 117-122, 2010

Article Link (Online Journal):

Funding Source:

Total Budget (Tk.) :

Achievement/Findings:

From this research study it is revealed that the tensile strength, flexural strength and young moduli of the untreated and bleached banana fiber-LDPE composites increases with increasing fiber loading up to 22.5 %. It is observed that the mechanical properties of bleached banana fiber-LDPE composites are slightly higher than the untreated banana fiber-LDPE composites. It is also observed that the tensile strength, flexural strength and young moduli of the LDPEbanana fiber composites are significantly higher than mold molded virgin LDPE (at 0% of fiber). Water absorption increases with increasing fiber loading, so coating is needed to improve the dimensional stability of the composites. Finally, it can be concluded that banana fiber can be used as reinforcing agent successfully.

Knowledge Management: Journal