There are green marks or regulations regarding recycled plastics, which request that specific products must be blending with certain ratios of postconsumer recycled plastics. However, there’s still no standard of verification on plastics blended with various ratios. Consequently, this project is aimed to establish a method of verification on Polypropylene (PP) plastics blended with various ratios by investigated the thermal and mechanical properties of the blended plastics. In this study, blended specimens are produced by injection molding with various ratios based on the parameters obtained from previous experiments. The blended specimens are analyzed and tested with thermal properties (by DSC, viscosity, MI, and TGA), mechanical properties (by tensile test and impact test), and morphological observations (by SEM and TEM), then verify the results with the activation energy (Ea) obtained from the kinetics, to investigate the characteristics of the blended specimens. The results revealed that Tm of new PP chips was 171.97℃ while that of postconsumer recycled PP was 170.24℃. MI of new PP chips was 8.3 g/10 min while that of postconsumer recycled PP was 25.6 g/10 min. Viscosity of new PP chips covered the range of 11,600 to 13,400 poise while that of postconsumer recycled PP covered the range of 7,120 to 8,320 poise. The operational parameters to inject blended specimens were set based on the testing results and operating conditions on-site, and produced the specimens with various mixing ratios. Tm of the specimens were in between 167-169℃. MI were in between 7.59-18.36 g/10 min, increased with increase of the ratio that recycled PP took account, and with increase of rotation speed as well. Maximum decomposition temperature decreased with increase of the ratio that recycled PP took account, and increased with increase of heating rates. Young’s Modulus (E) were in between 112.11-191.02 Mpa, and increased with increase of the ratio that recycled PP took account. Impact strength were in between 37.94~49.41 J/m and revealed no specific trends. The results of SEM showed that the specimens became more brittle with the increase of the ratio that recycled PP took account, which corresponded to the results of the tensile tests. Results of morphology analysis indicated good dispersions among the specimens by TEM. Ea were in between 39.91-12.07 kcal/mol, and decreased with increase of the ratio that recycled PP took account. Ea had significantly and highly negative correlation with MI, and E, and had significantly and highly positive correlation with viscosity. According to the experimental and statistical analysis results, we established equations to estimate mixing ratios in three different ways, and those equations can serve as reference for verifying the mixing ratios of PP plastics.

Polypropylene, thermal property, mechanical property, waste plastics, resource recycle, postconsumer recycled plastic