Effects of the paraffin wax (PW) content on the thermal and permeation properties of the LDPE/PW composite films

A series of low density polyethylene/paraffin wax (LDPE/PW) composite films were fabricated via a twin-screw extruder, and their morphologies, thermal properties, gas and vapor permeations, and surface properties were interpreted as functions of the PW contents. The PW was well dispersed into the LDPE matrix at low PW contents, whereas phase separation and an increase in surface roughness occurred with increasing PW content. The parameter results of surface properties such as contact angle, surface free energy, and solubility showed that the hydrophobicity of the LDPE/PW composite films also increased, and their phase changes and permeation properties were significantly dependent on the PW contents in the LDPE matrix. With increasing PW contents, both the oxygen transmittance rate (OTR) and water vapor transmittance rate (WVTR) of the LDPE/PW composite films decreased at a relatively low measuring temperature (23 °C), and increased at a relatively high temperature (48 °C). These results relate to the morphological structure (including tortuous paths and crystallinity) of the composite films via the incorporation of PW.