Analysis of the Effect of Temperature and Heating Time Variations on the Sheet Press Machine Toward the Hardness of PP and HDPE Plastic Materials

Abstract

Plastic waste, which is difficult to degrade, requires effective management solutions, one of which is recycling using a sheet press machine. The quality of the produced plastic sheets is strongly influenced by process parameters, particularly temperature and heating time. This study aims to analyze the effect of temperature and heating time variations on the sheet press machine toward the hardness of recycled polypropylene (PP) and high-density polyethylene (HDPE) plastics. The research was conducted experimentally using a quantitative approach at the Materials Testing Laboratory of Politeknik Negeri Manado. The temperature variations used were 165°C, 170°C, and 180°C for HDPE, and 170°C, 185°C, and 195°C for PP, with heating times ranging from 150 to 200 minutes. Hardness values were measured using the Rockwell M scale method in accordance with ASTM D785 standards, with five repetitions for each specimen. The results showed that PP achieved the highest hardness value of 17.13 HRM at 195°C/200 minutes, while HDPE reached its maximum hardness of 15.4 HRM at 165°C/150 minutes. Increasing temperature and heating time tended to increase PP hardness but reduced HDPE hardness due to thermal degradation. These findings can serve as a reference for optimizing the plastic recycling process to produce products with better mechanical properties.