By following the rules of green chemistry, a novel composite is developed from a renewable and ecofriendly resource, namely, vanillin. The latter was used as a phenolic precursor for the microwave synthesis of a bio-based benzoxazine resin (Va-BZ). Afterward, high-performance green composites were developed by reinforcing Va-BZ with various amounts of chopped silane surface modified carbon fibers (CFs). The chemical structure of the Va-BZ monomers was confirmed by 1H NMR and Fourier transform infrared spectroscopy. The grafting of the silane moiety on the CF surface was assessed by FTIR and TGA analyses. The autocatalytic ring opening polymerization of the Va-BZ monomers was confirmed by DSC analysis. The mechanical performances of the developed green composites were studied by flexural and tensile investigations. The findings suggested that the maximum amount of 20 wt. CFs afforded the best results, with flexural and tensile strengths of 450 and 462 MPa, respectively. The SEM was used to study the fractured tensile surfaces and elucidated the toughening mechanism. Meanwhile, the TGA showed that the introduction of the CFs markedly improved the thermal stability of the benzoxazine matrix. Overall, this study confirmed that greener approaches can also result in high-performance composites satisfying the needs of exigent applications.

Benzoxazine containing phthalonitrile, as one of the most advanced high performance thermosetting resin, has gained a lot of attention in the last decades. Indeed, the combination of the thermally activated ring-opening polymerization of the benzoxazine and the cyano addition reaction of the phthalonitrile allows the development of robust polymeric networks. Following this path, a renewable natural resource, vanillin, was used to develop a new benzoxazine containing phthalonitrile thermosetting system. The newly developed monomers present the advantage of a simple synthesis process along with an autocatalytic polymerization mechanism. The molecular structures of the synthesized monomers were characterized by Fourier transform infrared spectroscopy and proton nuclear magnetic resonance spectroscopy . Thermal properties were also characterized by differential scanning calorimetry and thermogravimetric analysis . Typically, the newly developed monomers showed excellent thermal stability with starting decomposition temperatures over 496.4°C with a char yield at 800°C of about 80.7%. The thermomechanical properties were investigated by dynamic mechanical analyzer and the fractured surfaces were studied by scanning electron microscopy Globally, the newly developed partially bio polymer showed outstanding thermal resistance along with excellent thermomechanical properties.

In this study, a new strategy is adopted for the development of advanced, and lightweight ballistic armor. This new generation of ballistic protections is referred to as “hybrid”, in which certain layers of Kevlar have been impregnated with a high-performance green and bisphenol-A free thermosetting resin, namely the vanillin-based benzoxazine (Va-BZ). The role of thermosetting polymer is to slow down and stop the projectile. In addition, the backface signature (BFS) with a minimum number of Kevlar layers is reduced. Indeed, this kind of matrix not only possesses one of the highest crosslinking densities in the field, but also offers excellent mechanical and thermal properties. The adopted experimental approach consists in gradually changing, in increments of 5, the number of impregnated Kevlar layers. The ultimate goal is to reduce the number of Kevlar layers from 26 (currently in use) to 20 while ensuring a BFS of less than 44 mm (as per the requirement of the National Institute of Justice standard NIJ-0101.06). Indeed, the adopted strategy allowed significant reduction in the BFS. For instance, armors made of 20 layers of Kevlar layers in which 10 layers were impregnated by the Va-BZ displayed the minimal BFS value of 36.54 mm. Hence, by introducing the Va-BZ resin, the non-perforated Kevlar fabrics gained enough rigidity to sustain the impact with minimal deformation. Overall, these newly developed armors offer the best BFS possible to protect vital human body parts.