The Preparation And Performance Of A Heat Resistant Adhesive From Bamboo

With the rapid development of the aerospace electronics and other fields, application of high temperature adhesives has been widespread concern. More and more strict performances of heat resistant adhesives are demanded to satisfy the application for bonding in high-temperature environment. Heat resistant adhesives include inorganic and organic adhesives. Inorganic adhesives have excellent heat resistance, but the bonding strength is low;Organic adhesives with excellent adhesion properties at room temperature, but the application are often limited below 300 ℃.Inorganic fillers with excellent chemical stability, heat resistance and mechanical characteristics have been used to modify resins to prepare adhesives.The production of bamboo tar increases year after year. Bamboo tar contains a variety of valuable chemical raw materials. Development and utilization of bamboo tar as raw materials help to improve the added value of bamboo tar, the comprehensive utilization of bamboo tar provides a new way of its application, which has remarkable economic benefits and environmental significance.In our experiment, the compositions of bamboo tar were analyzed by gas cartography-mass spectrometer （GC-MS） and infrared spectroscopy （FT-IR）.The COPNA resin was synthesized by bamboo tar, 1,4-benzene-dimethanol（PXG） used as a cross-linking agent,and p-toluene sulphonic acid played the role of catalyzer.An orthogonal experiment with four levels and three factors was designed to discuss the influence of the ratio of cross-linking agent to bamboo tar, the content of catalyst,reaction temperature and reaction time on carbon residue.The best synthesis condition is supposed to be:cross-linking agent and bamboo tar ratio is 0.6, the content of catalyst is 5%, and react under 150℃ for 3h.And the carbon residue of the resultant COPNA resin was 44.82%.The softening point of B stage COPNA was below 57.6℃.The resultant COPNA resin possessed good thermal stability, whose initial decomposition temperature above 300℃.A novel high-temperature adhesive was prepared using COPNA resin as the matrix and some inorganic filler as additives to modify the performance of the adhesives for joining Al2O3 ceramic. The influence of B₄C powder dosage and temperature on the performance of adhesives was discussed. The more B₄C powder, the strength is higher. With the increase of temperature,the strength decreased and then increased.At 1000℃,the shear strength was 23.16MPa and displacement was 0.48mm.The addition of B₄C powder improved the heat resistance of COPNA resin greatly, at 1000℃ the weight loss was only 5.75%.The structural evolution of studied by XRD and FT-IR,results showed above 550℃ ,B₄C reacted with micro molecules which were from degradation of organic matrix, and B2O3 was produced to restrain volume shrinkage. The SEM of joints section showed the section is uneven revealing plastic deformation. The joints were broken by mixed failure. In addition, the effect of curing conditions on strength was studied.In order to improve strength the curing time and temperature should be increased property. Suitable curing conditions was 80～100℃/2h+200～240℃/3h.NanoSiO₂ added to modify the COPNA-B₄C adhesive, which largely improves the strength.At 1000℃, when SiO₂ was added 3%wt, the shear strength was 53.28MPa.The influence of SiO₂ dosage and temperature on the performance of adhesives was also discussed.COPNA-B₄C-SiO₂ adhesive showed good resistance to chemical corrosion as well as thermal shock. High treatment temperature and more times cycle could enhance resistance to thermal shock.