Surface tension of polyethylene used in thermal coating

In this work the surface tension of a polyethylene used in thermal coating, identified as a mixture of low density polyethylene (LDPE) and stearic aci d, was measured as a function of temperature for temperatures ranging from 120 degrees C to 150 degrees C using a pendant drop apparatus. The values w ere compared to the surface tension of the pure components (low density pol yethylene and stearic acid). It was shown that the surface tension of the m ixture is higher than the surface tension of the pure components (more than 25%). Surface analysis by Electron Spectroscopy for Chemical Analysis (E.S .C.A.) of the polyethylene used in thermal coating before and after surface tension measurement was conducted: the experimental results showed that th e oxygen and the carbon present at the surface of both the powder and the d rop were involved in C-OH and COOH bonds (for oxygen) and in C-C and C-O bo nds (for carbon). It was shown that there is an increase of COOH and a decr ease of C-OH bonds at the surface when the polymer is heated. It was also s hown that there is an increase of C bounded to O at the surface of the drop and consequently a decrease of C-C bonds. The decrease of C-OH was attribu ted to the drying of the polymer during heating and the decrease of C-C was attributed to the coalescence of the polymer particles during pendant drop formation.