Synthesis Of Diamine-based Benzoxazine Resin And Their Composite Materials

Due to its superior performance and price ratio,excellent comprehensive performance and outstanding processing performance,benzoxazine resin has becomed a new star among thermosetting resins.Its products have been used in aerospace,electronic information,transportation,architecture and other fields.Among them,aromatic diamine-type benzoxazines with higher thermal stability and mechanical properties are receiving much attention and have great potential for development.However,this benzoxazines have difficulties and limitations,such as the presence of insoluble substances during synthesis,the need to use alkaline substances for regulation and complicated post-treatment,which greatly hinder their development and application in industry.Therefore,the active research and exploration of the synthesis of high-performance aromatic benzoxazines and their composite materials are of great significance in promoting the application and industrialization of benzoxazines.This article from the perspective of industrial production,using abundant and inexpensive phenol and diphenylmethanediamine as main raw materials,a simple and reasonable synthesis process was studied to solve the above difficulties and limitations.The structure and properties of the product were characterized by FTIR,1HNMR,GPC and DSC.The amplification was performed successfully in the laboratory and the product was stable.In order to formulate a reasonable curing mechanism and obtain a product with good performance.Firstly,the curing process of benzoxazine was investigated by FTIR and DSC.DSC shows that it is difficult to cure below 150? and curing is still not complete until 200?.FTIR indicates that the product is a phenolic hydroxyl Mannich bridge structure.Secondly,the theoretical curing temperature was obtained from non-isothermal DSC analysis,the initial curing temperature was 213.62?,the constant temperature curing temperature was 222.79? and the post-treatment temperature was 233.34?.Finally,through the established curing mechanism,a cast body with good appearance quality was prepared and the properties of the cured product were studied.DSC shows that the benzoxazine had been completely cured,and its glass transition temperature was as high as 185?.TGA shows that the product had good thermal stability,and its decomposition occurred at temperatures above 300?.The temperatures at 5%and 10%weight loss were respectively 345.79? and 392.29?.The char residue yield at 800? is 52.50%;DMA shows that the dynamic thermal properties of the cast body were very good and the glass transition temperature is as high as 211.06?.The dielectric properties indicate that the cast body had excellent dielectric properties.Its dielectric constant and dielectric loss factors were 2.13 and 0,0057,respectively.In view of the difficulty for curing benzoxazines,the selection of suitable catalysts was studied in this paper.Gel time and DSC show that adipic acid,imidazole and anhydrous aluminum chloride all had significant catalytic effects.When the same amount was added,the catalytic ability was the largest of anhydrous aluminum chloride,followed by imidazole and the smallest was adipic acid.However,anhydrous aluminum chloride requires a higher temperature to cure completely.Moreover,it is prone to absorb moisture and release the hydrogen chloride toxic gase.The TGA shows that the cured products with adipic acid catalyzed had the best thermal stability,followed by imidazole.Considering comprehensively,it is ideal to use adipic acid and imidazole as catalysts.Also,the amount of adipic acid and imidazole is not more than 3%and 2%,respectively.The industrial amplification test was carried out and the product was characterized.Furthermore,it was combined with the glass cloth to obtain a laminate with good appearance quality and comprehensive performance.It laid a foundation for future industrial production and research.