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hyperbranched polyimide resin modified by TRIS 2019-06-14 17:19:51


Automobile brake pads are generally composed of a steel plate, a bonded heat insulating layer and a friction block. At present, the brake pads on the market mainly use phenolic resin and nitrile rubber, but the phenolic resin is harmful to the environment, and the heat-resistant limit temperature is only about 250 °C. When the temperature is too high, the thermal decomposition phenomenon is quite serious, which will affect the bonding strength between the friction block and the steel plate, and in severe cases, the friction block will fall off. Therefore, it is necessary to find a new type of adhesive insulation material instead of phenolic resin.


Polyimide is a high performance polymer material, which can be used for a long time in the temperature range of -240 °C to 260 °C. The long-term use temperature of thermosetting polyimide resin can be above 300 °C, because this material is at high temperature. It has excellent thermal stability, chemical stability, mechanical properties and low dielectric constant, making it widely used in aerospace, electronics industry, automobile manufacturing and other fields. Hyperbranched polymer has three-dimensional network structure, multiple active sites, low viscosity, good fusion with matrix, etc. It has broad application prospects, and have shown great application value in the field of photovoltaic materials, coatings, adhesives, nanotechnology, drug delivery .


In order to solve the problem of the bond strength reduction under the high temperature condition of the brake pad bonding heat insulation layer, the researcher [1] provides a modified hyperbranched polyimide resin, and the preparation method is as follows:


Step 1: Add a triamine monomer (selected one or more from TAPOB, TAPOB, and TAP), dianhydride monomer (selected one or more from 6FDA, PMDA, BPDA, ODPA, BTDA) and the solvent DMF were stirred and dissolved at room temperature, and then heated to 60 °C, and stirred under N2 for 24 hours to obtain a hyperbranched polyamic acid solution.


Step 2: A Tris(Hydroxymethyl) Aminomethane (TRIS) monomer was added to the hyperbranched polyamic acid solution obtained in the first step, and reacted at 60 °C for 24 hours to obtain a modified hyperbranched polyamic acid solution having a terminal hydroxyl group.


Step 3: After removing the solvent of the modified hyperbranched polyamic acid solution obtained in the second step, the mixture is heated to 160 °C for 1 h to carry out an imidation reaction and an esterification reaction, and the water formed in the reaction is removed by N2. A modified hyperbranched polyimide resin is obtained.


The modified hyperbranched polyimide resin provided by the method introduces TRIS monomer, which improves the mechanical properties and high temperature resistance of the hyperbranched polyimide. At the same time, the end of the hyperbranched resin contains a large amount of hydroxyl groups, which can be crosslinked to form a stable system. The adhesive prepared by using the TRIS-modified hyperbranched polyimide resin can tightly bond the friction block and the steel sheet together, and the bond strength is not lowered at a high temperature.


Reference

[1] Preparation and application of a modified hyperbranched polyimide resin. CN109824895A, 2019.5.31.


Edited by Suzhou Yacoo Science Co., Ltd. 

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