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Epoxy resin as an adhesive, the main drawback of the resin base material is the adhesive layer is more brittle, and the impact and peel strength is poor, but the introduction of high molecular weight elastomer into the epoxy resin curing system is best for improving the toughness of the adhesive [ 2]. Polyvinyl butyral is one of the most widely used elastomers. Because of its high molecular weight, the cohesive strength of the adhesive layer is increased, the toughness of the adhesive is increased, and the impact strength and peel strength are also greatly enhanced. Because the elastomer contains a hydroxyl group, it can further polycondense with the hydroxyl groups of the silicone resin and the epoxy resin condensation body to form a three-dimensional network molecular structure, so that in addition to improving the toughness of the adhesive, but also improve the temperature resistance of the adhesive.
3.5 Adhesive use, bonding conditions and performance
Experiments have shown that it can be used as a structural adhesive for long-term use around 300°C, and can be used for the bonding of materials such as steel, aluminum, ceramics, glass, plastics, and bakelite. Curing pressure 0.05MPa, curing temperature 160 °C, curing time 1 ~ 2h. Its main performance is as follows.
3.5.1 Shear Strength of Adhesive Adhesive Shear strength of adhesive is tested according to GB7124-86 standard. The shear strength of the prepared adhesive is shown in Table 1 for the results of different materials at room temperature.
3.5.2 Thermal Loss of Adhesives We performed a TGA on the cured samples of this adhesive. The results of the analysis are shown in Figure 1.
As can be seen from Figure 1, the adhesive has no thermal decomposition before 30Q°C. Between 300 and 350° C. is a slow decomposition zone, and the thermal decomposition rate at 350° C. is 15%. When the temperature exceeds 350° C., the thermal decomposition rate rapidly increases.
4 Conclusion
The adhesive prepared by modifying the epoxy resin (E-20) with a silicone resin has both good mechanical properties of the epoxy resin and high temperature resistance of the silicone resin. At the same time, polyvinyl butyral was added during the preparation process to improve the brittleness of the epoxy resin and improve the toughness of the adhesive. The adhesives prepared by the method described in this article have a shear strength of 20 MPa or more at room temperature and excellent performance in various aspects when used under room temperature conditions; the shear strength at 300°C is 8.8 MPa or more, and therefore the workpiece to be bonded should be at 300°C. The long-term work under left and right conditions, the adhesive is also more suitable. In addition, the adhesive has a wide application area and can be used as a structural adhesive for a variety of materials.
Source: 21st Century Fine Chemicals Network
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