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Document Type

Thesis - University Access Only

Award Date

2003

Degree Name

Master of Science (MS)

Department / School

Agricultural and Biosystems Engineering

Abstract

Interest in the use of natural fibers has grown during the last decade due to their lower costs and the search for renewable sources. Composites consisting of polypropylene (PP), or high-density polyethylene (PE), and mixed pinewood, big blue stem (BBS), soybean hulls or distillers dried grain and solubles (DDGS) were prepared by extrusion processing. The test samples were prepared by injection molding. Mechanical properties; Young’s modules, tensile and flexural strengths, melt flow index, shrinkage and impact energy of the composites were evaluated. The effect of the fiber type, size and content on the mechanical properties of natural fibers/PP composites and natural fibers/PE composites were evaluated according to the appropriate ASTM standards. The results showed the fiber content influenced tensile and flexural properties. The Young’s modulus, under tensile load, or wood, big blue stem and soybean hull fiber composites compared with pure polypropylene and polyethylene were comparable or higher. The wood and big blue stem fiber composites had higher Young’s modulus, under tensile load, and tensile strength than soybean hull fiber composites. Compared among all the composites wood 80 mesh size fiber and 30% fiber content resulted in the highest Young’s modulus under tensile load, 1330 MPa for polypropylene. BBS 40 mesh size fiber and 30% fiber content resulted in the highest Young’s modulus under tensile load, 1120 MPa for polyethylene. Compared among all the composites BBS 80 mesh size fiber and 30% fiber content resulted in the highest Young’s modulus under flexural load, 24.70 MPa for polypropylene plastic. BBS 40 mesh size fiber and 30% fiber content resulted in the highest Young’s modulus under flexural load, 14.50 MPa for polyethylene plastic. Tensile strength significantly decreased for all the polypropylene fiber composites when compared with the control. The tensile strength of BBS fiber composites at 20% fiber content was higher or comparable to wood at 20% fiber content and at all fiber sizes. The use of soybean hull fiber resulted in lower tensile strength than when wood fiber was combined with polypropylene or polyethylene plastic composites. Compared among all the composites BBS 40 mesh size fiber and 20% fiber content resulted in the highest tensile strength, 34.6MPa, when combined with polypropylene. BBS 40 mesh size fiber and 30% fiber content resulted in the highest tensile strength, 22.6 MPa, when combined with polyethylene. Compared among all the composites BBS 40 mesh size fiber and 20% fiber content resulted in the highest flexural strength, 59.59 MPa for polypropylene. BBS 40 mesh size fiber and 30% fiber content resulted in the highest flexural strength, 36.27 MPa for polyethylene. There was a significant decrease in the melt flow index when mixed pinewood, BBS, soybean hulls were blended with polypropylene and polyethylene plastics. Compared among all the polypropylene DDGS 40 mesh fiber size and 20% fiber content resulted in highest melt flow index, 12.60 g/10 min. Polyethylene plastic, DDGS 40 mesh fiber and 20% fiber level resulted in highest melt flow index, 14.70 g/10 min compared to other fiber polyethylene blends. There was no significant difference in the shrinkage of all fiber plastic controls. BBS at 40 and 60 mesh fiber size and 20% and 30% fiber content polyethylene plastic controls resulted in higher notched impact strength than wood or soybean hull fiber composites. DDGS, BBS, and soybean hulls at 40 mesh and 20% or 30% showed no significant difference in unnotched impact strength when compared with wood fiber composites. The formulation of BBS 40 mesh size fiber and 20% fiber content resulted in the highest notched impact strength for both the plastics, 31.4 J/m for polypropylene and 34 J/m for polyethylene. Among all the composites tested, wood 60 mesh fiber size at 20% fiber content resulted in the highest unnotched impact strength, 142.91 J/m for polypropylene and soybean hulls 80 mesh fiber size at 20% fiber resulted in highest unnotched impact strength, 138.82 J/m for polyethylene. Biorenewable fibers like soybean hulls, big blue stem may have potential to be used as reinforcing materials for low cost composites.

Library of Congress Subject Headings

Fibrous composites -- Mechanical properties

Fiber reinforced plastics

Renewable natural resources

Format

application/pdf

Number of Pages

119

Publisher

South Dakota State University

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