Thermo-mechanical characterization of HDPE-tobacco lignin blends

With the expected exponential growth prospects of additive manufacturing, petroleum based plastic products and applications are also expected to increase. Hence there exists a need for renewable alternatives to traditional petroleum-derived plastics. Lignin, an abundant plant-derived feedstock, has been a perfect candidate for renewable materials. Lignin extracted from tobacco plants were used to prepare blends with high density polyethylene (HDPE). Different concentrations of blends (0, 5, 10, 15 and 30% by wt.) were prepared by extrusion of HDPE pellets and lignin powder at 175 ̊C. Coupons for mechanical characterization were fabricated using injection molding process. The effect of lignin on the processing conditions such as processing temperature, injection pressure and time were studied. Physical and mechanical tests such as density, specific gravity, tensile and hardness tests were conducted on the samples according to ASTM standards and compared with the neat HDPE properties. The compatibility of the blend morphology was studied using optical microscopy. Results show that the lignin concentration did not have a significant influence on the tensile strength at lower concentrations but decreased by 19% at 30 wt% of lignin. The tensile modulus increased with the increased in lignin content. Thermogravimetry Analysis (TGA) results indicated that the thermal stability has decreased at lower concentrations of lignin but unaffected at 15 and 30 wt%.