Molding Compounds from Douglas-Fir Bark

Variables influencing the process of molding whole bark-extended compounds (primarily Douglas-fir bark) into a deep-draw cup mold were studied. Variables included particle size, moisture content, resin type, resin content, mold temperature, and press time. Douglas-fir bark exhibited reasonable flow properties without the addition of any binder for simple shapes, however, 10 percent resin had to be added to achieve satisfactory flow for deep-draw molding. Temperature of the bark was important in producing good flow, probably above 315?F, and cooling of the mold was necessary to prevent blistering. Whole Douglas-fir bark can be added as an extender to certain injection molding compounds except where color clarity is critical. The modulus of rupture of cups containing phenol binder increased with increasing binder content while specific gravity decreased slightly. This decrease in specific gravity resulted from improved flow properties of molding compound with high resin content. Increasing the particle size of the bark filler increased the modulus of rupture.

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