Biopolymers & Biocomposites Workshop - August 14, 2012

Tensile Strength, Elongation, Tensile and Flexural Moduli, and Hardness of Thermoplastic Starch Filled with Glycerol-Plasticized DDGS

S.C. Clarizio and R.A. Tatara
Northern Illinois University

Distillers dried grains with solubles (DDGS), a co-product of ethanol-fuel manufacture, has been physically mixed with thermoplastic starch (TPS) pellets and injection molded into test bars using glycerol (a co-product of biodiesel production) as a plasticizer. Different blends consisting of 0-15% glycerol, 0-50% DDGS, and 0-100% TPS were mixed by weight according to a Design of Experiments procedure. The bars were subject to mechanical testing procedures to obtain tensile strength, tensile modulus, and elongation to break in according with ASTM 0638-10. The bars were also subjected to flexural modulus testing in accordance with ASTM D747-10, as well as surface hardness. From these tests ultimate tensile strength (UTS), Young’s modulus, % elongation to break, flexural modulus, and Shore D hardness data were generated. Up to 55% filler retained 75% of the UTS of pure TPS. For the tensile modulus, glycerol reduced the stiffness significantly. The percent elongation to break was 40-80% of pure TPS for blends with the exception of the 15% glycerol data, which showed a 200-300% increase. There was under 20% surface hardness loss up to 60% DDGS and glycerol filler. Overall, the blends retained reasonable mechanical performance up to 55% filler, especially when glycerol was under 5% although glycerol did act as a plasticizer allowing for molding of higher levels of DDGS. Thus these blends show promise as biodegradable, biobased materials. Applications may include one-time, outdoor disposable uses.