Evaluation of mechanical, thermal and structural properties of MWCNT/LDPE composite films produced by hot pressing

Low-density polyethylene (LDPE) is a prominent polymer with applications like packaging bags, textile fabrics, brushes and agriculture application - soil mulching because of its excellent chemical resistance, good impact strength, low coefficient of friction, and moderate stiffness but it has somewhat poor tensile and damping properties. Carbon nanotubes (CNT) are an excellent choice for reinforcement because of their excellent mechanical, thermal and electrical properties. This study aims to investigate the effect of CNT reinforcement on the mechanical, thermal and structural properties of LDPE composite films. LDPE/CNT composite films were prepared by hot Pressing. LDPE and CNTs (0.1 to 0.4 wt.%) were mixed by two different techniques: ball milling and mechanical stirring. The mixture was further pressed into thin films at 190°C and 12MPa. Two types of CNTs were used as reinforcements namely pristine and carboxyl functionalized. Carboxyl functionalized CNTs were obtained by refluxing CNTs with a mixture of H₂SO₄:HNO₃. It was found that LDPE/CNT (0.4 wt.% functionalized) composite films with ball milled exhibited storage modulus almost two times higher than that of pure PE films. The mechanically stirred CNT-PE composite films also showed nearly 62% improvement in storage modulus for functionalized and un-functionalized CNTs. The thermal stability of PE films slightly improved with the addition of CNTs. Maximum thermal stability was observed in the case of ball milled 0.4 wt.% functionalized CNT/LDPE films wherein decomposition of composite film started at 423°C and for PE films at 377°C. Wettability studies revealed that mechanically stirred 0.4 wt.% functionalized CNT/LDPE films showed the most hydrophobic surface with a water contact angle 110°, around 90° for pure LDPE films. (author)