Preparation and Characterization of Thermal-Insulating Microporous Breathable Al/LLDPE/CaCO₃ Composite Films

Breathable films were prepared based on linear low-density polyethylene (LLDPE), calcium carbonate (CaCO₃), and aluminum (Al; 0, 2, 4, and 8 wt.%) using extrusion molding at a pilot scale. These films must generally be able to transmit moist vapor through pores (breathability) while maintaining a barrier to liquids; this was accomplished using properly formulated composites containing spherical CaCO₃ fillers. The presence of LLDPE and CaCO₃ was confirmed by X-ray diffraction characterization. Fourier-transform infrared spectroscopy results revealed the formation of Al/LLDPE/CaCO₃ composite films. The melting and crystallization behaviors of the Al/LLDPE/CaCO₃ composite films were investigated using differential scanning calorimetry. Thermogravimetric analysis results show that the prepared composites exhibited high thermal stability up to 350 °C. Moreover, the results demonstrate that surface morphology and breathability were both influenced by the presence of various Al contents, and their mechanical properties improved with increasing Al concentration. In addition, the results show that the thermal insulation capacity of the films increased after the addition of Al. The composite with 8 wt.% Al showed the highest thermal insulation capacity (34.6%), indicating a new approach to transform composite films into novel advanced materials for use in the fields of wooden house wrapping, electronics, and packaging.