Preparation, Properties And Structural Analysis Of Photoactive Benzoxazine Resi

As a new thermosetting resin,benzoxazine is prepared by ring opening crosslinking polymerization of benzoxazine monomer.Benzoxazines are six membered heterocyclic compounds with nitrogen and oxygen synthesized from primary amines,phenols and formaldehyde.Benzoxazine Resin has high crosslinking density,a large number of benzene rings and hydrogen bonds in the molecule.These structural characteristics give Benzoxazine Resin high glass transition temperature,excellent electrical insulation and excellent mechanical properties.Benzoxazine Resin is a new type of heat-resistant phenolic resin.It is formed by the cationic ring opening polymerization of benzoxazine monomer,which overcomes the shortcomings of traditional phenolic resin.For example,the crosslinking process is a kind of ring opening crosslinking curing process,which is generated by absorbing a certain amount of heat.With the rapid development of science and technology and the rapid development of society,the fields of biomedicine,photoelectric information storage,chemical sensing,molecular machinery and other fields are developing rapidly.It is urgent for Benzoxazine Resin to achieve a new breakthrough in structure and function The development of class I is in urgent need of functional and intelligent materials.At the same time,benzoxazine has abundant sources and flexible molecular design.Benzoxazine monomers with different functional types can be prepared by selecting different amine and phenol sources,which can meet the functional requirements of materials in the application field,and bring huge space for the functional and fine development of benzoxazine.As one of the important engineering materials,benzoxazine resin has potential application value in aerospace,microelectronics and other high-tech fields.Based on the flexible molecular design of benzoxazine,three kinds of photoactive benzoxazine monomers with azobenzene group were designed and synthesized successfully,including PP-BA(p-phenylazophenol/aniline benzoxazine),PH-BA(4-hydroxyazopyridine/furylamine benzoxazine)and CPA-BA(4-hydroxyazopyridine/furylamine benzoxazine),respectively resin composites.The curing behavior and kinetics of three benzoxazine monomers were investigated by in situ FTIR and non isothermal DSC.According to Kissinger and Ozawa methods,the apparent activation energy Ea and pre exponential factor A of ring opening polymerization were obtained.Friedman method and autocatalytic model calculation equation were used to determine that the ring opening polymerization of three kinds of photo active benzoxazines belongs to the mechanism of autocatalytic reaction.In order to further study the functional properties of benzoxazine,three kinds of monomers were tested by ultraviolet spectrophotometry(UV).In the dark condition,ultraviolet light with specific wavelength was used to irradiate.During the irradiation process at different time intervals,the trans absorption peak and cis absorption peak decreased and increased in different degrees in the solution,which verified the trans cis isomerization of the three monomers in the solution The mechanical properties of TPU/PP-BA,TPU/PH-BA and TPU/CPA-BA composites were prepared.The mechanical properties of the three kinds of composites were 24.3%,28.7%and 34.2%higher than that of pure TPU under the same UV light intensity and irradiation time.The results showed that the mechanical properties of the three kinds of composites were 24.3%,28.7%and 34.2%higher than that of pure TPU under UV irradiation.The quantum chemical calculation(QCC)method was used to obtain pp-ba,ph-ba and cpa-ba The optimal molecular structures of three kinds of photoactive benzoxazine monomers were determined,and the EHOMO and ELOMO of the three monomers were determined.By judging the phase of wave function and its positive and negative values,the density of electron cloud is determined.The internal reasons that affect the difference of open-loop curing temperature and optical activity of the three monomers are deeply analyzed.At the same time,the thermal stability(TGA)of the three kinds of composites is tested and analyzed to explore the difference of heat resistance of the composites.