After obtaining the best results based on a comparison between the three types of blend compatibilizers, the PhHRJ-PE compatibilizer was selected to prepare the MNR/HDPE TPVs. To investigate the influence of loading level of the PhHRJ-PE compatibilizer on the properties of the TPVs, five loading levels 3, 5, 7, 9, and 12 wt% of the HDPE were studied and compared with TPV without a compatibilizer. The OE-MNR was first prepared using the compounding formulation and mixing schedule described in Table 1 and Table 2, respectively. The oil-extended MNR/HDPE TPVs at a fixed blend proportion at 60/40 with various amounts of PhHRJ-PE were then prepared using the mixing steps as described in Table 3. After fabrication of test specimens by injection molding, the mechanical, dynamic and morphological properties of the TPVs were investigated.