Means to Improve the Elastic Characteristics of Epoxy Adhesives and Efficiency of Adhesive Joints on Their Basis
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s to Improve the Elastic Characteristics of Epoxy Adhesives and Efficiency of Adhesive Joints on Their Basis A. P. Petrovaa, *, N. F. Lukinaa, and A. Yu. Isaeva aAll
Russian Institute of Aviation Materials, Moscow, 105005 Russia *e-mail: [email protected]
Received August 7, 2019; revised February 3, 2020; accepted February 7, 2020
Abstract—Approaches to the modification of epoxy film adhesives with various low-molecular rubbers and polysulfones are considered. A significant improvement is shown of such characteristics as elasticity, longterm strength, vibration strength, and others is demonstrated. Improvement of the characteristics of adhesive joints using a combination of phenolic elastomer adhesive and unmodified cold-curing epoxy adhesive, at which the adhesion technology is facilitated as compared to phenolic elastomer adhesive. Keywords: epoxy adhesive, rubber, polysulfone, adhesive combination, sublayer DOI: 10.1134/S1995421220040164
Cured epoxy adhesives possess relatively low crack resistance and elasticity due to their chemical nature, which restricts their application for adhesion of materials in loaded structures. To increase their elastic characteristics and efficiency under loading during operation, special components are added to adhesive compositions. Plasticizers, which do not interact with the epoxy basis of adhesive, as well as low-molecular elastomers or thermosetting materials, are employed in adhesive epoxy systems as modifiers, which improve their elastic properties and crack resistance. Employment of plasticizers, such as phthalic, sebacic, phosphoric, and other acid esters, results in a decrease in the viscosity of adhesive compositions and an increase in flexibility of macromolecules; however, this leads to a decrease in glass-transition temperature, mechanical and adhesion strength, and some other parameters [6]. Among elastomers, butadiene–acrylonitrile rubbers with terminal carboxylic groups are mainly used as modifiers. Terminal carboxylic groups of rubber interact with epoxy groups of epoxy oligomer; in this case, a high strain capacity of the polymer is provided and the water absorption ability is significantly reduced. However, high-temperature stability of adhesive joints decreases in this case. Polysulfones are used as thermosetting materials for modification. The use of polysulfones for modification of epoxy systems significantly increases strength and thermomechanical characteristics of cured compositions.
Another approach to the improvement of the efficiency of adhesive joints under various loads is the combination of cold-curing epoxy adhesives and phenolic elastomer adhesives. In this case, liquid phenolic elastomer adhesive is first deposited as a sublayer onto glued surfaces and heat-treated without pressure. Cold-curing epoxy adhesive is then deposited onto the sublayer of phenolic elastomer adhesive. The surfaces are glued using the technology recommended for epoxy adhesive (without heat treatment and high pressure, which is necessary upon gluing with phenolic elastomer ad
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