Evaluation of the Flexural Strength, Sorption, Rheological and Thermal Properties of Corncob Plastic Composites

Plastic composites were made from corncobs and high density polyethylene (HDPE) by extrusion and evaluated. The composites were manufactured using two different screened corncob particle size fractions (<2 mm and <0.5 mm) and tested for flexural properties, water sorption, melt flow and thermal properties. The melt viscosities at 190oC were 18.0 ± 0.8 kPa•s (<2 mm) and 24.0 ± 0.6 kPa•s (<0.5 mm). The results obtained indicated that the composites made with the smaller particle size fraction had higher flexural strength (31.7 ± 1.7 MPa) and modulus of elasticity (1.4 ± 0.1 GPa) than those made with the larger particle size fraction (21.2 ± 1.4 MPa and 1.1 ± 0.1 GPa). Also, the composites made with the smaller particles and were more dimensionally stable. Corncob composites had thermal stability range of 259 – 274oC (onset degradation temperature). The corncob composites made with smaller sized particles possessed better properties in comparison with those made from the <2 mm. Particle size and density significantly affected the mechanical, physical and thermal properties of the composites evaluated.