Novel cardanol-containing boron-modified phenolic resin composites

Abstract

To improve the thermal stability of phenolic resin and develop functional sustainable adhesive, a thermal-resistant cardanol-containing boron–phenolic resin (CBPR) was prepared by copolymerizing salicyl alcohol, cardanol, and boric acid. The structure of CBPR was characterized by Fourier transform infrared spectroscopy. Thermal stability of the investigated composites was estimated using thermogravimetric analysis (TGA). The results of TGA indicated that the modified resin exhibited excellent thermal stability. Specifically, the B-0.2 thermoset had a char yield of 69% when the boron content was only 1.27 wt%. The curing kinetic behavior was well described by differential scanning calorimetry and model-free kinetic analysis. Further, CBPRs, nano-aluminum oxide powders, glass powders with low melting point, and vitreous silica fibers were used as resin matrix, filler, forming additive, and reinforced material, respectively, to produce a novel ceramizable phenolic molding composite. The ablative characteristics of the co-cured blends were explored in terms of linear/mass ablation rate and microscopic pattern of ablation via the oxyacetylene torch tests. After thermal treatment, the formation and growth of the ceramic phase enhanced the thermal stability and ablation performance of the composites at high-temperature region. The morphology and phase composition of the residual chars were studied by scanning electron microscopy and energy dispersive spectroscopy, respectively. The linear and mass ablation rates for the modified composites decreased obviously in comparison with those of the unmodified composites, indicating that the modified composites possessed enhanced thermal stability and ablation property.