A novel resveratrol-based bio-benzoxazine monomer (RES-al) containing an allyl group has been synthesized using resveratrol, allylamine, and paraformaldehyde via Mannich condensation reaction, and its chemical structures have been characterized by FT-IR spectroscopy and NMR techniques. The polymerization behavior of this benzoxazine resin has been investigated using in situ FT-IR and differential scanning calorimeter (DSC) measurements, and the thermal-mechanical properties of its corresponding polybenzoxazines are evaluated by DMA and TGA. We show that by controlling the curing process of the oxazine ring, the C=C bond in resveratrol, and the allyl group in RES-al, the cross-linking network of the polybenzoxazine can be manipulated, giving rise to tunable performance of thermosets. As all curable functionalities in RES-al are polymerized, the resulted polybenzoxazine exhibits a good thermal stability with a Tg temperature of 313 °C, a Td5 value of 352 °C, and char yield of 53% at 800 °C under N2.

Ammonium polyphosphate (APP)-polystyrene (PSt) core-shell microspheres (CSPs) were synthesized via in situ radical polymerization. The core-shell structure was confirmed by transmission electron microscope (TEM). The results of optical contact angle measurements demonstrated a significant improvement in hydrophobicity of the modified APP. The obtained APP-PSt CSPs were added into epoxy (EP) system with various loadings. Effects of CSP on flame retardancy, thermal properties, heat release rate (HRR), smoke production, and mechanical properties of EP/CSP composites were investigated by limiting oxygen index (LOI), UL-94 tests, thermogravimetric analysis (TGA), cone calorimeter, and tensile test. LOI and UL-94 indicated that CSP remarkably improved the flame retardancy of EP composites. TGA showed that the initial decomposition temperature and the maximum-rate decomposition temperature decreased, whereas residue yields at high temperature increased with the incorporation of microspheres. Cone calorimetry gave evidence that HRR, peak release rate, average HRR, and smoke production rate of EP/CSP composites decreased significantly. The morphology of char residues suggested that CSP could effectively promote EP to form high-quality char layer with compact outer surface and swollen inner structure. Tensile strength of EP was enhanced with the addition of CSP. V C 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40218.

Epoxy (EP) composites containing polystyrene-ammonium polyphosphate core-shell microspheres (CSP PS-APP ) were developed for flame retardant and toughening effects. The flame retardancy and thermal degradation behavior of the EP composites was investigated by limited oxygen index (LOI), vertical burning test (UL-94), cone calorimeter (CONE) and thermogravimetric analysis (TGA). Scanning electron microscope with energy-dispersive spectroscopy capability (SEM-EDS) was used to characterize the morphology and elements of the residual chars. A possible flame retardant mechanism of CSP PS-APP in EP matrix was proposed based on the CONE, TGA and SEM-EDS results. The influence of CSP PS-APP content on the glass transition temperature (T g ), storage modulus, Young's modulus, tensile strength and fracture toughness (K IC ) of material was also investigated. The results show that the CSP PS-APP microspheres lead to significant flame retardant and char formation effects on the EP. The Young's modulus and fracture toughness of EP/CSP PS-APP composites increase with increasing CSP PS-APP content. The fracture toughness of the composite containing 15% CSP PS-APP increased by approximately 59% compared to that of neat matrix. In addition, the critical strain energy release rate (G IC ) of the epoxy increased from 159 to 409 J.m -2 with the addition of 15% CSP PS-APP . The SEM images of fracture surface indicate that the enhanced toughness of EP/CSP PS-APP composites can be attributed to the debonding of the core-shell 2 microspheres and the subsequent plastic void growth of the matrix, as well as the crack deflection effect of CSP PS-APP .

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