Date of Award

5-2004

Document Type

Thesis

Degree Name

Master of Science in Materials Science and Engineering (MSMSE)

Department

Materials Science

First Advisor

Dr. Abdallah AI-Khanbashi

Second Advisor

Dr. Adel Hammami

Abstract

During the last twenty years, ecological concerns have resulted in a renewed interest in natural materials. Composite materials usually depend on using man-made fibers as the reinforcing element. The possibility of using natural fibers instead of synthetic fibers is gaining acceptance among users. This work aims to investigate the possibility of extracting natural fibers from date palm trees to be used as reinforcement with polymeric materials. The objective was achieved by characterizing fibers through different chemical, physical and mechanical tests and using different treatment methods in order to modify the fiber properties. Date Palm Fibers (DPF) exhibit a cylindrical shape and are composed of a collection of hollow fibers surrounded by relatively thick layers. The density of raw DPF was found to be about 0.92 g/cm3, and its chemical composition is comparable to that of other common natural fibers and consists of approximately 46 wt. % cellulose, 20 wt. % lignin and 18 wt. % hemicelluloses. The diameter of DPF ranges from 100 to 1000 µm. However, thermal analysis by using thermogravimetric analyzer (TGA) under air atmosphere and heating rate 10°C min-1 shows that thermal degradation of DPF starts at 250°C. The tensile strength of DPF ranges from 170 to 275 MPa and the modulus of elasticity ranges from 5 to 12 GPa with an elongation to break of 5-10%. Surface modification of raw DPF affects its surface morphology, density, thermal stability, chemical composition and maximum tensile strength. The fibers were used as reinforcement for a polymeric matrix (polymer resin) and the resulting composites were subjected to different kinds of mechanical and physical testing, which included flexural, impact testing and water absorption. Also, composite specimens containing randomly oriented glass fibers were used for benchmarking. Higher flexural properties (flexural strength and modulus) were achieved for critical length of 2 cm and weight fraction of 9 wt. %. The mechanical properties of specimens’ prepared using critical length and critical weight fraction of fibers from different treatment processes have shown variation in the mechanical properties. Also, surface modification of fibers affects the mechanical properties of DPF/polyester composites and specimens prepared with alkali treated DPF yields the highest flexural strength about 70 MPa among other treatment methods.

Furthermore, impact strength (toughness of composites) shows different behavior when using fibers from different treating methods. Composites prepared with fibers treated with a soda solution giving the highest impact strength about 12 KJ m-2. Moisture absorption of DPF/polyester composites was low and did not reach 2% with all types of fibers used but it was higher than moisture absorption of glass/polyester composites which was about 0.7%.

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