Desenvolvimento e caracterização de filmes poliméricos de polietileno com adição de nanocargas para aplicação em blindagem balística

Abstract

The development of new engineering materials for individual or collective protection purposes is increasing. Due to the advancement of tactical and military technologies, it is necessary to improve armoring systems, for example, more functional vests and helmets, with lower density and greater flexibility. Allied to these properties, it seeks to reduce costs, without compromising impact absorption. An alternative to improve these properties is to replace the usual materials with more common materials, such as polymers considered commodities, which are affordable and have attractive mechanical, chemical and thermal properties. The addition of nanofillers in polymeric matrices has been highlighted in recent years, due to their advantageous characteristics compared to pure materials, increasing the properties of materials called nanocomposites, such as mechanical and thermal properties. Among the nanofillers, we can mention nanofibrillated cellulose (CNF), nanoclay (ARG) and graphene nanoplatelets (NPG), each with distinct morphology and characteristics. The use of cellulose for this type of application, combined with thermoplastic polymer was not found in the literature, being a positive point for the technological innovation of the research. The objective of this work was to develop nanostructured films of high and low density polyethylene (HDPE/LDPE) with the incorporation of different nanofillers to later obtain multilayer plates with aramid fabric (AR), aiming at the potential application for ballistic protection. For the production of the films, a masterbatch of CNF in LDPE was incorporated into HDPE and the premixes were subjected to double-screw extrusion followed by balloon blowing extrusion. Subsequently, the AR and the films were cut, stacked in interleaved layers, and subjected to hot and cold compression, respectively. The first multilayer plates with the addition of CNF between 0-1.5% were evaluated in step 1, and with the best concentration, new films were produced with ARG and NPG, the addition of coupling agent (CA) was also evaluated. All nanostructured films were characterized in step 2. In step 3, multilayer plates with nanostructured films from step 2 were made and characterized. In step 1, in the dynamic compression test on split Hopkinson pressure bar (SHPB), the HDPE/LDPE/1.0CNF/AR sample obtained superior energy dissipation behavior among the others, with 1.0% being the predefined concentration for the production of other films in the subsequent step. All samples from stage 1 were classified in ballistic protection level III-A. In step 2, the films with the addition of ARG and NPG showed superior results in relation to thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), dynamic-mechanical testing (DMA), flow index (IF) and tensile strength. The CNF+CA and the matrix sample with the addition of CA (HDPE/LDPE+CA) also showed an increase in some properties. In step 3, the multilayer plates were evaluated by SHPB, and the samples with ARG, NPG, and HDPE/LDPE+CA obtained higher stress behavior at high strain rates, contributing to better energy dissipation in these plates. All samples from step 3 were classified in ballistic protection level III-A, and the posterior deformation (DP) was reduced in samples with ARG and NPG, in 11.61 and 12.98% in relation to the raw sample (PEAD/PEBD/AR). In the mechanical tests, the modulus of elasticity due to flexural strength was more pronounced, being 44% higher for the samples with CNF+CA and with NPG, and 18% for the sample with ARG. The results showed that the addition of nanofillers to can be a viable alternative for application in multilayer composites, together with AR, for protection purposes, maintaining and/or improving the mechanical and impact properties. [resumo fornecido pelo autor]