**2.1. Preparation of thermoplastic blend (TPB)**

The rHDPE and rPET were compounded via extrusion process by using a laboratory-scale corotating twin screw extruder (Thermo Prism TSE 16 PC). The screw-rotating speed was fixed at 30 rpm. The four barrel temperatures from feeding to die zones were set as 250, 270, 240 and 190 °C, respectively. For the uncompatibilized thermoplastic blend (UTPB), the weight ratio of rHDPE/rPET was fixed at 75/25 (wt%). Meanwhile, 5 parts per hundred compounds (phc) of E-GMA was added in the compatibilized thermoplastic blend (CTPB) with the same ratio of both plastics.
