Grassland fiber, specifically switchgrass or fescue, were investigated as a filler for thermoplastic materials. Laboratory and pilot plant studies were carried out to examine the processing characteristics and properties of injection molding grade high density polyethylene (6 melt flow index or MFI) blended with experimental switchgrass or fescue flour or commercial pine wood flour. Switchgrass performed comparably to pine for most properties evaluated, particularly for the larger screen fraction materials (e.g., 40 and 60 mesh flour). Fescue also produced acceptable properties for 40 mesh flour, but the finer fraction (60 mesh) generally had properties inferior to pine or switchgrass. The finest fraction switchgrass (80 mesh) exhibited properties comparable to the 60 mesh fescue. In general, the tensile and flexural modulus increased linearly with the addition of natural fiber, and tensile and flex strength was typically unchanged or slightly decreased as fiber load increased. Izod impact re- sistance (notched or unnotched) decreased substantially upon addition of filler. Mold shrinkage and MFI also decreased as flour was added. Trends such as these are in agreement with previous research on wood flour as an additive to polyoelfins. Overall, the indications here are that Iowa grassland flour could be used as a substitute for wood flour in similar fiber/plastic applications.
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