Tensile Strength Analysis of High Density Polyethylene for Injection Moulded Parts

This paper investigates the performance of pure high density polyethylene (p-HDPE) and recycled high density polyethylene (r-HDPE) by comparing the tensile strength of both materials. The specimens were injected by injection moulding machine and the parameters investigated were melting temperature (200-240°C), injection pressure (75-95 MPa), and holding time (20-30 s). Response Surface Methodology (RSM) was used to accommodate the experimental run as well as to analyse the experimental results. The result from Analysis of Variance (ANOVA) showed that the melting temperature is the most significant parameters affecting the tensile strength of both materials with the F-value is 307.58, followed by injection pressure (77.32) and holding time (19.67). The result also showed that the tensile strength of both materials increase with increasing of melt temperature, injection pressure and holding time. The optimal tensile strength of p-HDPE (27.04 MPa) was obtained at the melting temperature of 240°C, injection pressure of 95 MPa and holding time of 20 s. On the other hand, the optimal tensile strength of r-HDPE (16.058 MPa) was achieved at the melting temperature of 240°C, injection pressure of 95 MPa, and holding time of 29 s. The reduction percentage of tensile strength for r-HDPE as compared to p-HDPE was in the range of 43.478% - 40.703%. Even though the tensile strength of r-HDPE has been reduced by around 40% as compared to p-HDPE, the r-HDPE can still be utilised for packaging application such as containers, bottles, and jars. Therefore, this will help to significantly reduce waste in order to sustain the environment.