Abstract:
Polypropylene and polystyrene are petroleum-based thermoplastics which are commonly
used and disposed of in the environment after their service life, leading to environmental
degradation. There is a need to recycle polypropylene and polystyrene, but the effect of
recycling on thermo-mechanical properties is not well understood. This study aims to determine
thermo-mechanical properties of the recycled polypropylene and recycled polystyrene and compare
them with corresponding virgin polypropylene and newly produced polystyrene (general purpose
polystyrene 1540 and high impact polystyrene 7240). The study was carried out by preparing
bar-shaped samples of recycled polypropylene, recycled polystyrene, general purpose polystyrene
1540, and high impact polystyrene 7240 by compression molding using a hot press and thermally
characterizing them to determine glass transition temperature and melting temperature using
differential scanning calorimetry. The changes in Young’s modulus, tensile strength, hardness, and
toughness due to recycling activities were determined at room temperature (24 ◦C), 40 ◦C, 60 ◦C, and
80 ◦C. The thermo-mechanical properties of recycled polystyrene (PS) were found to be comparable
to those of high impact polystyrene (HIPS) 7240. The study revealed that the hardness and toughness
for the recycled polymers were higher than those of corresponding virgin polymers. On the other
hand, tensile strength and Young’s modulus for the recycled polymers were lower than those of the
virgin polymers. Understanding the thermo-mechanical properties of the recycled polymers will
contribute to more industrial applications hence increase the rate of recycling, resulting in a reduction
in environmental pollution.
