Bending Strength of Radiation-Produced Southern Pine Wood-Plastic Combinations

Specimens of loblolly pine sapwood were randomly assigned to one of four treatment groups. One group was not treated and served as control; the other groups were treated with methyl methacrylate (MMA). Polymerization was initiated by gamma radiation from 0.96 to 3.60 megarads. The percent retention of monomer in wood was found to be inversely proportional to specific gravity. Polymer loading was also inversely proportional to specific gravity, and proportional to percent conversion. The bending strength of the wood-plastic composite reaches a maximum at about 0.45 g/g polymer loading, and then decreases. This phenomenon is probably the result of specific gravity variation and unusually high stress concentration transmitted to woody cells during polymerization. Regression lines of MOR and MOE of treated and untreated wood were drawn as functions of untreated specific gravity. The treated wood samples exhibited greater strength than the untreated samples.

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