KAJIAN SIFAT MEKANIK HDPE, PMMA DAN POLYESTER AKIBAT PERUBAHAN LAJU REGANGAN

• Main Author: Kharina, Anastasia
• Format: Final Project
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/59266
• Institution: Institut Teknologi Bandung

Compared to other classes of materials, polymers have more variety in their constituents, properties, and versatility of use. Therefore, knowledge and databases on polymers’ properties need to be improved continuously. Polymer’s sensitivity of strain rate, even in room temperature, is a matter that needs to be considered in all kinds of polymers application. The research was carried out to study the effect of strain rate to mechanical properties of High Density Polyethylene (HDPE) – semi crystalline thermoplastic, Poly(methyl methacrylate) – amorphous thermoplastic, and Polyester-thermoset. Some observations on fractography of fracture surface of specimens was also conducted. Mechanical properties were obtained by uniaxial tensile test with three different strain rates (1,6x10-4 s-1, 1,6x10-2 s-1, dan 1,6x10-1 s-1). Specimes’ geometry were made according to ASTM D638-03 standard type 1. Observations on fractography features were carried out using microscopy techniques. Specimens characterizations using DSC (Differential Scanning Calorimetry) and density measurement were also performed for verification and analysis of data obtained from specimens manufacturing and tensile test. The results obtained show that the modulus of elasticity and tensile strength of PMMA and HDPE increased with strain rate in the range of 1,6x10-4 s-1 to 1,6x10-1 s-1 (????EHDPE=121%, ????EPMMA=58%, ????????????HDPE=60%, ????????????PMMA=68%). In the other hand, increasing strain rate caused the ductility and toughness of HDPE and PMMA to decrease (????e*HDPE=77%, ????e*PMMA=31%, ????UTHDPE=66%, ????UTPMMA=5%). Compared to HDPE and PMMA, change of mechanical properties values of Polyester due to change of strain rate is not significant. Mechanical properties change with strain rate is due to viscoelasticity nature of the three polymers, as well as their glass-transition temperature and structure. HDPE has the highest sensitivity to strain rate, followed by PMMA and Polyester, respectively. HDPE showed ductile fracture characteristics with the formation of fibrils and craze, while PMMA and Polyester underwent brittle fracture. Fracture surface of PMMA featured mirror zone, rib marks, hackles, conic marks, dimples, and microfibrils, while Polyester showed mirror zone, wallner lines, hackles, and conic marks.