Waste Polyethylene and Polypropylene Particles as Mechanical Reinforcements of Polyester Polymer Mortar: Gamma Radiation as Postcuring Treatment

Abstract

The excessive use of high-density polyethylene (HDPE) and polypropylene (PP) to produce materials with a very short useful life has caused environmental problems due to the lack of sustainable recycling routes and end-use applications for the recyclates of these materials. Different processes for the reuse of these polymers have been proposed, including the use of ionizing energy to modify the molecular structure and physicochemical properties, including mechanical properties. For these reasons, in the present study, waste HDPE and PP particles (size 0.7 mm), replaced 1, 2, and 3 wt.% silica sand in polymer mortar produced with 20 wt.% polyester resin and silica sand. The mortar specimens were exposed to gamma rays at doses of 100, 200, and 300 kGy. The results show an increase of up to 45% in compressive strength, 19% in flexural strength, 43% in modulus of elasticity, 40% in compressive strain, and 33% in half-span deflection for polymer mortars with 1% of wPP particles and irradiated at doses of 300 kGy. These mechanical results show that the use of waste polymers as fillers is a good alternative for the final disposal of them. Furthermore, these improvements were related to the morphological modifications produced by gamma rays in the waste polymers, analyzed by scanning electron microscopy.