Abstract This paper investigated the formation of crosslinks in natural rubber compounds in the vulcanization systems: conventional (CV), semi-efficient (SEV), and efficient (EV), processed with three types of accelerators: MBTS (dibenzothiazole disulfide), TMTD (tetramethylthiuram disulfide) and CBS (n-cyclohexyl 2-benzothiazole sulfenamide). The cross-linked densities were determined by organic solvent swelling, dynamic mechanical analysis (DMA), stress vs strain, and low-field nuclear magnetic resonance, the latter being the reference technique for comparison with the other results. It was found that the choice of accelerator type influences the processing time and the cross-linked density of the vulcanizate. The four techniques showed close values of cross-linked density for natural rubber compounds, demonstrating that the analytical techniques studied can be applied to determine cross-linked density.

In this study we have explored the behavior and the damage mechanisms of a laminate panel composed of polymeric and ceramic materials, submitted to the impact of a metallic projectile. The design of a system with the impact side in ceramic material (SiC) was made, with a support of an ultra-high molecular weight polyethylene (UHMWPE), plaques made with 200 mm square geometry and 5 mm thick, and polymeric tissue cuts with equal area dimensions. The (NIJ) Standard 0101.06 was taken as reference for testing the ballistic impact essay; crater formation was identified in the ceramic material; using optical microscopy and scanning fractures and delamination were identified as predominant failure mechanisms; in the polymeric material, fibrillation twist, fiber fusion, conical deformation and delamination were observed and then samples were analyzed using "Morye, Smith and Retch e Ipson" kinetic energy balance models. The result showed that the most influential to dissipate energy, is the panel made with dual ceramic plate (SiC) and double-layer polymeric tissue as a backup.

En este trabajo se exploró el comportamiento y los mecanismos de daño de un panel laminado compuesto a partir de materiales poliméricos y cerámicos, ante el impacto de un proyectil metálico. Se realizó el diseño de un sistema con la cara de impacto en material cerámico (SiC), con respaldo elaborado en polietileno de peso molecular ultra alto (UHMWPE), placas elaboradas con geometría cuadrada de 200 mm de lado y 5 mm de espesor, y cortes de tejido polimérico con iguales dimensiones de área. Se tomó como referencia el montaje de la norma (NIJ) Standard 0101.06 para el ensayo a impacto balístico; en el material cerámico se identificó la formación de cráter, fracturas y delaminación como mecanismos de falla predominantes, utilizando microscopia óptica y de barrido; en el material polimérico se observó fibrilación, torsión, fusión de fibras, delaminación y deformación cónica y posteriormente se analizaron las muestras empleando los modelos de balance de energía cinética de "Morye, Smith y de Retch e Ipson". El resultado evidenció que el arreglo con mayor influencia para disipar energía, es el panel elaborado con doble placa cerámica (SiC) y doble capa de tejido polimérico como respaldo.