Investigation of plasma-induced thermal, structural and wettability changes on low density polyethylene powder

Abstract

We demonstrate here the structural, thermal, and wettability characteristics of low density polyethylene powder before and after plasma treatments. The plasma treatment was carried out using different working gas i.e. air, oxygen and a mixture of hydrogen and oxygen at an atmospheric pressure of 100 Pa. The plasma treatment time was kept constant at 2 min for all the specimens. Fourier transform infrared (FTIR), dynamic capillary rising using Washburn method, differential scanning calorimetry (DSC), and thermogravimetric analysis has been carried out for both pristine and plasma treated polyethylene specimens. Our study shows that there is 88% increase in the wettability after plasma treatments. Plasma treatment in air atmosphere gives the maximum wettability. Thermogravimetric analysis (TGA) investigation shows plasma treatment in the H2 + O2 mixture atmosphere gives maximum thermal stability whereas the DSC results reveal the lowest crystallinity for plasma treatment in air atmosphere. The lowest latent heat of fusion (154 J/g) calculated from the melting curve of DSC is observed for LDPE treated in air atmosphere. The FTIR spectroscopy of the plasma-treated LDPE powder reveals that plasma treatment introduces polar group on the LDPE surface leading to the increased surface free energy and surface active sites. The CH2 concentration increases after plasma treatments.