Principle analysis and seven methods to improve bonding strength
Source： Author： Release time：2021/05/25 Views：5828
Performance: epoxy resin adhesive is made of epoxy resin, curing agent and filler. It can be used as structural adhesive and building pouring material for metal, cement, ceramics, glass, stone, wood, thermosetting plastics and other materials.
Principle analysis: in the formula, epoxy resin and PVC resin are the main adhesive components; Dioctyl phthalate was used as plasticizer; Quartz powder and silica were used as fillers; Boron trifluoride glycerin, boron trifluoride aniline and triethylenediamine were used as curing agents; Phosphoric acid is used as acidifier, and it can promote curing and increase adhesion to metal.
Two component room temperature curable epoxy adhesive. Apply a certain amount of pressure to the surface to be bonded. It can be cured at room temperature. The curing conditions are: 14-16 seconds at 16.5 ℃, 7-9 seconds at 25 ℃, 4-6 seconds at 30 ℃. It is mainly used for the bonding of various metals, metals and nonmetals, as well as various hard plastic products, with high bonding strength.
Bonding strength enhancement method of epoxy adhesive
Although the bonding strength of epoxy adhesive is relatively high, it is still insufficient for some high-strength structures. It is necessary to further improve the bonding strength through the following ways.
01. High performance epoxy resin is used
Some high performance epoxy resins, such as AG-80, afg-90, phenolic epoxy resin, pan-f epoxy resin, bisphenol s epoxy resin, liquid crystal epoxy resin, TDE-85 (ij ()), 731, etc., have high adhesive strength when they are mixed with bisphenol A epoxy resin or mixed with them. Liquid crystalline epoxy resin is a kind of polymer network with high molecular order and deep molecular crosslinking. It can form self reinforcing structure and has excellent mechanical properties. A small amount of liquid crystal ring Maple resin and B144 epoxy resin were blended, and the tensile strength and impact strength of the cured product were obviously dropped.
02. Select reinforcing curing agent
Curing agent has an important influence on the bonding strength of epoxy adhesive. The curing agents that can make epoxy adhesive have high bonding strength after curing are selected, such as dicyandiamide, m-phenylenediamine, diaminodiphenylmethane, diaminodiphenylsulfone, low molecular polyamide (315, 3051), g-328, amino terminated polyether, 105 acetal, methylhexahydrophthalic anhydride, pyromellitic anhydride / phthalic anhydride (20 / 28) 2-ethyl-4-methylimidazole, linear phenolic resin, etc.
The epoxy resin was grafted with CTBN in advance, polyether amine was used as internal toughening curing agent, and the room temperature shear strength of epoxy adhesive cured at room temperature was 35 MPa by using dual toughening system. 90 ~ peel strength is more than 3.5kn/m.
03. Add reinforcing filler
The addition of fillers reduces the thermal expansion coefficient and curing shrinkage of the cured product, and reduces the internal stress. When the crack appears under overload, the adhesive layer with filler can also prevent the crack growth, thus improving the bonding strength. For example, epoxy adhesive used for metal structure bonding, adding appropriate amount of iron powder can improve the shear strength. The reinforcing fillers include silica powder, silica, wollastonite powder, alumina, ultra-fine aluminum silicate, light oxide, talc powder, sepiolite powder, attapulgite powder, ultra-fine calcined kaolin, iron oxide powder, iron powder, aluminum powder, zinc powder, glass flake, stainless steel flake, dolomite powder, etc.
04. Inorganic whisker reinforcement
Whiskers are very small diameter fibers grown in the form of single crystal under special conditions. They have highly ordered atomic arrangement structure, so they can approach the theoretical strength of valence bond between atoms. They have great potential for strengthening epoxy adhesives. The available whiskers are zinc oxide whisker, calcium sulfate whisker, calcium carbonate whisker, aluminum borate whisker, titanium based whisker, hydroxyapatite whisker, magnesium hydroxide whisker, basic magnesium sulfate whisker, silicon carbide whisker, etc.
05. Fiber reinforcement
Glass fiber, carbon fiber, aromatic polyamide fiber (Kevlar fiber), vinylon fiber, polyvinyl alcohol fiber, polyphenylene sulfide fiber, stainless steel fiber, basalt fiber and mullite fiber can all strengthen the epoxy adhesive.
06. Silane coupling agent reinforcement
Adding appropriate silane coupling agents, such as KH-560, KH-550, kh-580, kh-590, kh-792, nanda-42, nanda-73, a-186 and a-1160, can effectively improve the bonding strength of epoxy adhesive. For example, the shear strength of epoxy adhesive bonded aluminum with KH-550 (1%) is 11.6 MPa; 7 MPa without coupling agent.
07. Use membranous epoxy adhesive
Membrane epoxy adhesive is called epoxy adhesive film for short. Bisphenol a solid epoxy resin and multi-functional epoxy resin with high molecular weight are often used in the manufacture. When bonding, it is easy to ensure the uniform thickness of the adhesive film, so the bonding strength is very high.
Honm
Tel
Email