Morphology, phase diagram, and properties of high-density polyethylene/thermally treated waste polyethylene wax blends

Waste polyethylene wax is thermally treated using a rotary evaporator to reduce unwanted components. Fourier transform infrared proves the absence of undesirable material. Wax is extruded with high-density polyethylene (HDPE) at various loadings to study its morphology and final properties. Scanning electron microscopy and differential scanning calorimeter were employed to obtain the phase diagram showing the immiscibility of blends containing more than 20 wt% of wax. Due to the low melting temperature of the wax and its plasticating effect on HDPE, a decrease in melting temperature, enthalpy of fusion, and crystallinity with increasing wax content of the blend is observed. The phase diagram displays four possible phases depending on temperature and wax loading. Improved processability of HDPE/wax blends is demonstrated using complex viscosity curves. Han plots prove the miscibility of wax and HDPE in the melt state even at high concentrations of wax. HDPE/wax compounds have lower crystallinity, and wax particles, acting as weak spots, lower the elastic modulus, yield stress, and stress and strain at break as wax content increases. An increase in yield strain is observed due to the more effortless extension of HDPE chains at higher wax content. In 10 wt% of wax is accepted as the upper limit for wax incorporation into the HDPE matrix.

Automated summary

The study focused on the thermal treatment of waste polyethylene wax and its incorporation into high-density polyethylene (HDPE). The results showed that wax significantly affects the properties of the blend, but remains miscible within a certain range of content.