Evaluation of tensile and flexural strength properties of virgin and recycled high-density polyethylene (HDPE) for pipe fitting application

Innovative ways of eliminating heavy plastic waste all over the world must be designed and implemented via recycling of post used plastic materials by making new products. As a result of continuous use of plastic materials, adverse effect on the environment and economic issues had been a problem confronting the post-consumer recycling of these materials. High-Density Polyethylene (HDPE) polymers are widely being used and its products are preferable than metals having the properties such as lightweight, ease of manufacture, stronger and tough. This research work focuses on investigating the flexural and tensile strength properties of virgin and recycled HDPE for pipe fitting application. The mixing of recycled with virgin HDPE were done at different weight percentages (0:100, 10:90, 20:80, 30:70, 40:60, 50:50, 60:40, 70:30, 80:20, 90:10, and 100:0). Eleven (11) T-reducer pipe fitting samples were produced via injection moulding machine. Data of flexural strength test for selective samples similar with tensile test in showed that 100 wt% virgin HDPE had 39.98 MPa whereas 100 wt% recycled HDPE had 20.88 MPa. Generally, all the mechanical (tensile and flexural) properties decreased as number of recycled contents increased. Because, recycled high density polyethylene scrap (rHDPE) have weaker bond strength than virgin high density polyethylene (vHDPE) materials. Bond strength is very strong in virgin HDPE, and they also have molecular weight that is large. Also, there is highest rigidity in virgin HDPE. Rigidity is very high in virgin HDPE due to high toughness. So, with lower load, bond strength is not allowed to break. But there is weaker bond strength in 100% recycled scraps of HDPE as a result of different kinds of stresses they have been subjected to during prior usage.