Miscibility, morphology, and thermal properties of hyperbranched polyborates modified phenolic resins

Research Progress in Boron-Modified Phenolic Resin and Its Composites

As one of the most successful modified phenolic resins, boron-modified phenolic resin (BPF) has excellent heat resistance and ablative resistance, good mechanical and wear resistance, and flame retardancy. BPF and its composites can be widely used in areas such as aerospace, weapons and equipment, automobile brakes, and fire retardants. In this review, the current state of development of BPF and its composites is presented and discussed. After introducing various methods to synthesize BPF, functionalization of BPF is briefly summarized. Particular emphasis is placed on general methods used to fabricate BPF-based composites and the heat resistance, ablative resistance, mechanical property, wear resistance, flame retardancy, and water resistance of BPF-based composites. Finally, the challenges of this research area are summarized and its future outlook is prospected.

Thermal behavior of phenolic-based ceramizable composites modified by nano-aluminum oxide

A novel ceramizable organic composite was prepared by compression molding using silicone-modified phenolic resin (PR) as the matrix, nano-aluminum oxide powder as the filler, glass powder with low melting point as the forming additive, and vitreous silica fiber as the reinforced material. The ablative characteristics were explored in terms of linear/mass ablation rate and microscopic pattern of ablation via the oxyacetylene torch tests. Thermal stability of the investigated composites was estimated by means of thermogravimetric analysis. The final charring yields after pyrolysis increased from 63% to 69% and 74%, respectively. The silicone-modified PR acted as cross-linking adhesive at low-temperature region and tended to convert to bonding layer at high-temperature region. The formation and growth of the ceramic phase after thermal treatment 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, energy dispersive spectroscopy, and X-ray diffraction, respectively. The test results revealed that the modified composite possessed excellent thermal stability and ablation property.

Novel cardanol-containing boron-modified phenolic resin composites

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.