Mechanical and thermal properties of UHMWPE / LLDPE / CNT blends and nanocomposites for ballistic application
ABSTRACT The purpose of developing UHMWPE/ LLDPE/ CNT nanocomposite plates is to obtain a material that can be applied in laminated ceramic/polymer structures for high-impact ballistic protection. The polymer nanocomposite is used in the backing plate of the armor structure to absorb the residual kinetic energy of the projectile and shards from the ceramic material after impact. The polymer nanocomposite must have high fracture toughness, high mechanical strength and controlled deformation, in order to comply with these requirements. For instance, extreme deformations of the backing plate may cause injury to users of ballistic protective vests. In this work, a blend of linear low-density polyethylene (LLDPE) and ultra-high molecular weight polyethylene (UHMWPE) was prepared, using a high-rotation homogenizer with subsequent hot pressing, in order to facilitate the manufacturing process of the polymer nanocomposite plates. Furthermore, carbon nanotubes (0.5, 1.0 and 2.0 wt%), functionalized with nitric acid, were added to the polymer blend, in order to improve the mechanical properties of the resulting material. The mechanical and thermal properties of the polymer blend and the polymer nanocomposite were compared with each other. The polymer blends and polymer nanocomposites were submitted to mechanical tests such as Shore D hardness and uniaxial tensile tests. Differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) were performed to evaluate thermal stability of the various compositions. Finally, scanning electron microscopy (SEM-FEG) was performed to evaluate the morphology of the nanocomposites.