Effect of thermo‐oxidative aging on surface characteristics of benzoxazine and epoxy copolymer

Abstract

The copolymer of bisphenol A‐based benzoxazine and cycloaliphatic epoxy resin possesses greater processability and glass‐transition temperature compared to that of benzoxazine homopolymer, making it suitable for high‐temperature aerospace applications. The aim of this work is to investigate the behavior of the copolymers under thermos‐oxidative aging conditions using the surface characterization techniques. The benzoxazine homopolymer and copolymer samples were thermally aged in an air‐circulating oven under controlled temperatures of 180 and 200°C for various periods of time up to 24 weeks. The thermo‐oxidative‐induced weight change and surface cracking were monitored for samples during the aging period. As an alternative method to characterize thermal aging, static contact angle, and contact angle hysteresis of samples were measured over time. Moreover, droplet impact tests using deionized water were performed on stationary and moving samples to investigate the effects of aging time and temperature on impact dynamics of droplets. In addition, FTIR analysis was performed to evaluate the chemical changes on the surface of samples. The results indicated the extent of degradation of aged samples increased with increasing the aging time and temperature. In addition, the copolymer of cycloaliphatic epoxy and benzoxazine showed a greater amount of thermos‐oxidative degradation than the one for benzoxazine homopolymer. More importantly, the results obtained from the surface analysis measurements (e.g., contact angle) followed a similar trend to the one obtained from the traditional aging experiments (e.g., weight change). This showed the former nondestructive and simple method can be used to monitor thermal aging of materials in service.

Multifunctional Biobased Benzoxazines Blended with an Epoxy Resin for Tunable High-Performance Properties

“…Benzoxazine-epoxy resin formulations are one of the most academically and commercially relevant class of benzoxazine materials and are a topic of great interest in recent benzoxazine research. − Benzoxazine-epoxy (B-E) resin formulations have shown to increase the processability, cross-link density, and T g and enhance mechanical properties of the resulting polymer compared to the benzoxazine homopolymer. − B-E resins do not require the use of a curing agent as phenolic hydroxyl groups generated from the ring-opening of the benzoxazine are able to catalyze the ring-opening of oxirane rings in epoxy resins. , Furthermore, liquid epoxy resins can serve as reactive diluents for typically solid powder benzoxazines, which is advantageous for resin processing. − , B-E resins containing petroleum-derived bisphenol A and bisphenol-F have been reported, but a fully biobased benzoxazine monomer blended with a commercial epoxy resin has not been studied.…”

Studies on thermal and mechanical behavior of nano TiO2 - epoxy polymer composite

“…Although the Tonset values of nanoparticle incorporated composites were higher than the Tonset of pristine epoxy, it seemed to be no obvious trend. The multistage thermo-oxidative degradation of epoxy systems has been reported in previous studies [31]. It is reasoned that several complex chemical reactions involving epoxy chains, such as aromatization and dehydrogenation of alkyl groups occurred [32].…”

Phosphorus‐containing benzoxazine modified epoxy resin: High flame retardancy, low dielectric, and low water absorption

“…The change of contact angle could be associated with benzoxazine. According to literatures, [46][47][48] the hydrogen bond and surface energy of polybenzoxazine are affected by the structure and polymerization conditions of amine. When benzoxazine is cured together with epoxy resin, the hydrogen bond changes and results in the variation of surface energy.…”