Preparation And Properties Of High-Performance Benzoxazine Resin For Light-Curing 3D Printing

Polybenzoxazine is one of the few new polymers that have been part of the commercialization in the last 40 years.Polybenzoxazine is well suited for use in extreme environments because of its excellent stiffness,low flammability and high temperature properties,and because it is virtually impervious to moisture,chemicals and other corrosive materials.New-generation benzoxazine resins are also safer and easier to handle and process because they can be stored at room temperature,have low volume shrinkage and do not release major reaction byproducts during polymerization.Although some minor components are produced due to thermal cleavage or evaporation of monomer and solvent molecules.They have applications in aerospace,such as interior panels and bulkheads;transportation,such as automotive under-the-hood components;the oil/gas industry,such as risers and downhole plugs;and electronics manufacturing,such as printed circuit boards.However,the current engineering use of benzoxazine is too brittle,so it is difficult to achieve the complex structure of the molding manufacturing,which has become a bottleneck in the application and development of benzoxazine,and additive manufacturing technology combined with photosensitive benzoxazine material system for light-curing 3D printing,using its "shape control and control" advantage,can solve the problem of benzoxazine The combination of additive manufacturing technology and photosensitive benzoxazine material system for photocurable 3D printing can solve the problem that benzoxazine is too brittle to be manufactured.Based on this,this article synthesized a photosensitive benzoxazine intermediate and successfully prepared a photocurable 3D printing ink of benzoxazine resin to solve the problem that benzoxazine is too brittle for molding and manufacturing,and explored its mechanical,thermal,rheological and other properties.The main research contents and conclusions are as follows:(1)Three different benzoxazine intermediates with photosensitive properties were synthesised.Suitable monomers were selected through molecular monomer culling.A series of chemical reactions using paraformaldehyde and isocyanoethyl methacrylate resulted in the successful preparation of three photosensitive benzoxazine intermediates and and characterise its structure.These were then individually formulated into light-curable resin inks and subjected to thermal weight loss(TGA)testing.The carbon residue rates of the photosensitive benzoxazine intermediates synthesised with different monomers varied significantly.(2)The problem that benzoxazine cannot be molded and manufactured due to excessive brittleness was solved,and the parameters for light-curing 3D printing of benzoxazine and the optimal process for subsequent heat treatment were determined.One of the three benzoxazine intermediates with better performance was selected,and for this intermediate,a light-curable 3D printable resin ink was prepared.The determined printing parameters were: the LED power of the light-curing 3D printer was set to 250,the thickness of the first layer slice was 50μm,and the curing time was 20 s.The remaining layer thickness slice was set to 100μm,and the curing time was 10s.The optimal process for the subsequent heat treatment was determined as follows: the oven was heated to 80℃,the heating rate was 3℃/min,the sample was kept warm for 1 h,and then it was heated to 140℃,the heating rate of 3 ℃ /min,the sample holding 1h,after heating to 200 ℃,heating rate of 3 ℃ / min,the sample holding 1h,after heating to 240 ℃,heating rate of 3 ℃ / min,holding 2h,and finally cooled to room temperature and removed.(3)For the above benzoxazine intermediates,a series of ink formulations that can be light-cured 3D printed were designed.And light-cured 3D printed samples were prepared and tested for thermal properties,mechanical properties,rheological properties,dimensional shrinkage and printing accuracy.The results showed that the light-cured 3D-printable benzoxazine has extremely low curing shrinkage,the linear shrinkage can reach 1.8%,and the smallest printable feature size is 300 μm.