Properties and selection of the hottest adhesives

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Properties and selection of adhesives

1. Principles for selecting adhesives

(1) consider the type, nature, size and hardness of bonding materials

(2) consider the shape, structure and process conditions of bonding materials

(3) consider the load diagram borne by the bonding part: automobile oil pan and form (tensile force, shear force, peeling force, etc.)

(4) consider the special requirements of materials, such as conductivity, heat resistance, high temperature resistance and low temperature resistance

2. Properties of bonding materials

(1) metal: the oxide film on the metal surface is easy to be bonded after surface treatment; Because the difference between the two phase linear expansion coefficients of the adhesive bonded metal is too large, the adhesive layer is easy to produce internal stress; In addition, the metal bonding part is prone to electrochemical corrosion due to the action of water

(2) rubber: the greater the polarity of rubber, the better the bonding effect. Among them, nitrile chloroprene rubber has high polarity and bonding strength; Natural rubber, silicone rubber and isobutylene rubber have small polarity and weak adhesion. In addition, there are often mold release agents or other free additives on the rubber surface, which hinder the bonding effect

(3) break through the bottleneck of core general chip design and manufacturing wood: it is a porous material, which is easy to absorb moisture and cause dimensional changes, which may lead to stress concentration. In addition, the bonding performance of polished materials is better than that of rough wood

(4) plastic: plastic with large polarity has good bonding performance

(5) glass: from the microscopic point of view, the glass surface is composed of countless uniform uneven parts Use adhesive with good wettability to prevent possible bubble influence at concave and convex parts In addition, the main structure of glass is si-o- and its surface layer is easy to absorb water Due to the strong polarity of glass, the polar adhesive is easy to bond with the surface to form a solid bond Glass is brittle and transparent. These factors should be taken into account when choosing adhesives.

3. Characteristics and selection of adhesives

(1) Connecting various materials with different elastic modulus and thickness, especially thin materials

(2). The bonding surface is smooth and the aerodynamics is good

(3). Good sealing performance and corrosion performance

(4). Extend the service life of the bonding parts and reduce the weight of the bonding parts

(5). Low labor intensity, low cost and high production efficiency

(6). Non conductive adhesive heat-resistant and anti-seismic insulation, in which:

a, the order of flexibility of modified epoxy resin is: epoxy polysulfide epoxy polyamide epoxy amine curing agent

b, the order of flexibility of modified phenolic resin is: phenolic resin polyamide phenolic resin polyvinyl acetate phenolic resin epoxy

c. Heat resistance of main adhesives:

maximum heat resistance temperature adhesive maximum heat resistance temperature adhesive inorganic 315 silicone 540 polybenzimidazole (short time) 260 phenolic epoxy 480 polyimide (short time) 200 phenolic butyrone; Epoxy acid 8, 1-point-1-point radioactive anhydride 400 phenolic resin (short time) 150 epoxy amine 360 polybenzimidazole, polyimide 80 hot-melt type, epoxy nylon

D, effect of curing temperature on epoxy adhesive strength

curing condition triethylenetetramine dimethylaminopropylamine curing temperature c 2595145 4095145 curing time 3 days 15 days 30 minutes 16h 16h 5h 30 minutes MPa 8.2 11.9 22.4 24.2 4 4.9 5.9 22.8 28.6

e Strength characteristics of adhesive

adhesive shear resistance, tensile peeling, bending, twisting, punching, creep fatigue, epoxy 0 *** 0 * phenolic resin 0 \ * * * * 0 * cyanoacrylate 0

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