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

Abstract

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.

Effect of porous zeolite on temperature-dependent physical properties of polypropylene/octadecane (PP/OD) composite films

“…Gas permeation through polymers occurs via a sorption-diffusion mechanism [1][2][3][4][5]. Various penetrants such as O 2 and water vapors adsorb onto the upper surface of a polymer, diffuse through the polymer matrix, and desorb from the opposite surface, while gas permeation properties of a material are strongly dependent on its chemical structure and changes in the polymer morphology originating from the temperature variations [1][2][3]5].…”

“…Various penetrants such as O 2 and water vapors adsorb onto the upper surface of a polymer, diffuse through the polymer matrix, and desorb from the opposite surface, while gas permeation properties of a material are strongly dependent on its chemical structure and changes in the polymer morphology originating from the temperature variations [1][2][3]5]. During the last several decades, many different groups have conducted research studies on the permeability of various penetrant molecules (such as O 2 and water vapors) in polymers [3][4][5].…”

“…During the last several decades, many different groups have conducted research studies on the permeability of various penetrant molecules (such as O 2 and water vapors) in polymers [3][4][5]. Among the studied materials, polymers characterized by temperature-dependent gas and water vapor permeability properties such as poly(alkyl acrylate) [3,5], poly(N-isopropylacrylamide) [1], polyurethane [6,7], low-density polyethylene/paraffin wax (LDPE/PW) composite films [2], and polypropylene/octadecane (PP/OD) composite films [8] are becoming increasingly important in packaging applications for agricultural products and medical devices. The quality of agricultural products strongly depends on atmospheric composi-tions, which are affected by variations of respiration rates, transpiration during storage, and distribution environments [1,3,5].…”

“…Therefore, chemical and physical properties of the packaging materials should be adjusted to provide optimal gas permeability properties for practical applications in various fields. Phase change materials (PCMs) are materials that store and release heat energy during temperature-driven phase changes [2,8,[10][11][12]. Among various PCMs, PW is readily available and possess desirable characteristics such as large latent heat storage capacity, chemical inertness and stability, and non-toxicity [2,[10][11][12][13].…”

“…Phase change materials (PCMs) are materials that store and release heat energy during temperature-driven phase changes [2,8,[10][11][12]. Among various PCMs, PW is readily available and possess desirable characteristics such as large latent heat storage capacity, chemical inertness and stability, and non-toxicity [2,[10][11][12][13]. For these reasons, PW-based materials have been investigated for energy storage applications and thermal protection systems [10][11][12].…”