ABSTRACT
There is a need to identify usable lignocellulosic materials that can be blended with thermoplastic resins to produced commercial lignocellulosic plastic composites (LPC) at lower costs with improved performance. The core objectives of this study are to: i) evaluate the use of dried distillers grain with solubles (DDGS) and Paulownia wood (PW) flour in high density polyethylene-composites (LPC); ii) assess the benefit of chemically modifying DDGS and PW flour through chemical extraction and modification (acetylation/malation); and iii) to evaluate the benefit of mixing DDGS with Pine wood (PINEW) in a hybrid LPC. Injection molded test specimens were evaluated for their tensile, flexural, impact, environmental durability (soaking responses), and thermal properties. All mechanical results from composites are compared to neat high-density polyethylene (HDPE) to determine their relative merits and drawbacks. HDPE composites composed of various percentage weights of fillers and either 0% or 5% by weight of maleate polyethylene (MAPE) were produced by twin screw compounding and injection molding. Chemical modification by acetylation and malation of DDGS and PW fillers prior to compounding was done to evaluate their potential in making an improved lignocellulosic material. Composite-DDGS/PINEW mixture blends composed of a majority of PINEW were superior to composites containing DDGS only. Composites containing MAPE
had significantly improved tensile and flexural moduli compared to neat HDPE. Impact strength of all composites were significantly lower than neat HDPE. Chemical modification substantially improved the tensile, flexural, water absorbance, and thermal properties of the resultant composites compared to untreated composites. Differential scanning calorimeter and thermogravimetric analysis were conducted on the HDPE composites to evaluate their thermal properties as this may indicate processing limitations with conventional plastics processing equipment due to the exposure of the bio-material to elevated temperatures. Finally, because exposure to the moisture in the environment can affect the physical and color properties of wood, changes in the size and color of test specimens after prolonged soaking were evaluated.
