Preparation and properties of benzoxazine precursors containing siloxane units and their epoxy copolymers

Abstract

Four siloxane benzoxazines containing different rigid segments were successfully synthesized and characterized herein, including a benzene ring, a biphenyl, a naphthalene ring, and a diphenyl sulfone group. Different rigid segments had different effects on polymer properties. The introduction of the naphthalene ring and sulfone group considerably reduced the curing temperature of benzoxazine. Although the benzoxazine with the naphthalene ring exhibited low heat resistance, all the four samples showed a high char yield at 800°C under nitrogen atmosphere. In addition, during copolymerization with AG-80 epoxy, the introduction of epoxy promoted the curing of the benzoxazines containing the naphthalene ring and sulfone group. The heat resistance of all copolymers was considerably improved, especially for the copolymer containing the naphthalene ring, whose 5% thermal weight loss temperature ( Td5) increased from 248°C to 321°C under nitrogen atmosphere. The copolymer containing the biphenyl structure had the highest glass transition temperature, reaching 259.1°C. Copolymerization with epoxy also considerably improved the tensile strength and elongation at break of the copolymers, which were much higher than those of traditional bisphenol A-aniline based benzoxazine (BA-a). Compared with the neat benzoxazine prepared using siloxane and bisphenol A, the developed copolymers also had better tensile properties, and the copolymer containing the sulfone group showed the greatest improvement (from 49 to 69 MPa, from 3.1% to 9.12%).

Polysilazane hybrid phenolic resin ceramic aerogels with excellent electromagnetic wave absorption performance

“…However, how to avoid phase separation between polysilazane and support materials, achieve effective dispersion and prepare a highly cross‐linked polymer framework remains a challenge 27,39 . As a traditional processing polymer, phenolic resin is an example of an early‐developed carbon aerogel, which provides an idea for solving this problem 40–43 . Phenolic resin could be added to polysilazane aerogel to reduce the brittleness of polysilazane and simplify its complex preparation method, which is an excellent additive candidate to prepare a new ceramic aerogel with low density, heat insulation, and excellent EMW absorption properties.…”

Integrating Benzoxazine‐PDMS 3D Networks with Carbon Nanotubes for flexible Pressure Sensors

“…[44][45][46] The addition of siloxane to benzoxazine moieties has been a popular option in the literature for improving the polybenzoxazine properties, including its ability to impart excellent flexibility and high thermal stability. [47][48][49] Various studies have integrated distinct siloxanes into benzoxazines, resulting in improved characteristics in the resulting polybenzoxazines, such as enhanced glass transition temperature (Tg) and toughness, [49][50][51][52][53][54][55] better thermal stability, [49,[51][52][53][54][55][56][57][58][59][60][61][62][63][64][65][66][67][68][69] increased flame retardancy, [53,55,66,70] higher surface hydrophobicity, [71] improved mechanical properties, [51,58,62,64,72,73] enhanced shape memory effect, [48] corrosion resistance [74] and lower...…”