Fabrication of high density polyethylene composites reinforced with pine cone powder: mechanical and low velocity impact performances

The pine cone plant is a cellulosic material that is inexpensive and abundant in nature. It can be used as a reinforcing material in thermoplastic based composites. Pine cone plant has good mechanical properties and therefore allows it to be used as a filler material in composites. Alternative utilization from such agricultural pine cone powder in high density polyethylene (HDPE) composites can supply economic and environmental advantages. In this study, pine cone reinforced high density polyethylene (HDPE) composites were fabricated and their mechanical (i.e., tensile, compression and flexural properties) and low velocity impact behaviors were determined experimentally. To this end, collected pine cones were firstly cut into 1 cm pieces by using a knife and were pulverized by grinding in a ring mill. After that, two HDPE plates with dimensions of 350 x 350 x 1 mm were manufactured in the hot press. Then, various percentage amounts of powdered pine cones (5, 10, 15 and 20% wt) were added between these plates. Thereafter, pine cone reinforced HDPE composites were obtained under the same conditions. Mechanical properties and low velocity impact behaviors of the pine cone reinforced HDPE composites were determined at room temperature and findings were compared with each other. The parameters such as tensile and flexural strengths, compressive strength, elasticity and flexural modulus and energy absorption capacities of the composites were evaluated through various curves. According to obtained results, HDPE containing 10% pine cone powder showed the highest tensile strength, elasticity modulus and flexural strength. Low velocity impact test results exhibited that maximum contact force values of the reinforced HDPE with 5, 10 and 15% wt pine cone powder are higher than the neat HDPE at the impact energy levels ranging from 5 J to 25 J.