Adhesive knowledge is widespread, do you really understand adhesives?
xinstApr 02, 2020
Definition of adhesive
Adhesive knowledge Natural or synthetic, organic or inorganic substances that can connect two or more parts or materials together through the effects of interface adhesion and cohesion of substances, collectively referred to as adhesives ) Also called adhesive, customarily called glue.
① Adhesion (adhesion): refers to the state where two surfaces are held together by chemical, physical, or both forces
② The adhesive must first adhere to the surface of the adherend. This is due to the adhesion between the two phases, which is derived from the secondary or primary bond force.
Cohesion: That is, the state of each particle in a single substance is combined by primary valence (including ionic, covalent, coordination, metal, etc.) and secondary valence (including van der Waals, hydrogen bonding). The cohesive force of the adhesive is related to factors such as intermolecular force, relative molecular mass, degree of cross-linking, crystallization and molecular entanglement.
Adhesive requirements Adhesive knowledge
① Regardless of the state, it should be liquid when coating
② The surface of the adherend can be fully spread and fully wetted
③ Must be able to transform the liquid into a solid or gel state in some way to form a tough and stable glue layer
④ It should have a certain strength after curing. Able to connect reliably, transfer stress and resist damage
⑤ Can withstand temperatures above 0 ° C and withstand a certain period of time
Classification of adhesives
Classified by appearance: solvent-based emulsion type (aqueous); paste or paste; solid type; film type.
According to the curing method: water-based evaporation type, solvent evaporation type, hot melt type, chemical reaction type, pressure sensitive type.
Basic composition of adhesive
The basic composition of adhesives: the components of adhesives include base materials, curing agents, solvents, plasticizers, fillers, coupling agents, crosslinking agents, accelerators, tougheners, tackifiers, thickeners, diluents, Anti-aging agent, polymerization inhibitor, flame retardant, initiator, photosensitizer, defoamer, preservative, stabilizer, complexing agent, emulsifier.
Type of base material: The base material is the main component of the adhesive, the main agent or the main polymer, and plays an adhesive role. According to the chemical composition, the sources of the base material are inorganic compounds and organic compounds. Organic compounds are polymer binders for polymer synthesis.
① Common organic compounds: thermosetting synthetic resins: phenolic resin, epoxy resin, amino resin, polyurethane resin, unsaturated polyester and acrylic resin
② Thermoplastic synthetic resin: rubber base material, natural polymer material, water-based latex, base material
③ Rubber base adhesive
Selection principle of adhesive base material: According to the application object, application occasion and application performance of the adhesive. At the same time, the molecular structure of the molecular base is closely related to the adhesion properties.
① The polarity of polymer materials is related
② Crystallization of polymer materials
③ Molecular weight of polymer materials
Curing agent (hardening agent): The raw material in the ground state undergoes chemical reactions to undergo polymerization, polycondensation, or cross-linking reactions to change into linear polymers or network polymers. It is a substance that has mechanical strength and stability.
The role of solvents:
① Polymerization reaction medium: moderate reaction and easy temperature control
② Dissolving base material: preparing solvent-based adhesive knowledge
③ Thinner: Dilute the adhesive to a certain viscosity, which is good for wetting and coating.
④ Adjust the volatilization rate of the adhesive
⑤ Prevent gel, used to increase storage stability
⑥ Surface cleaning agent before bonding
⑦ Direct bonding, some plastics
⑧ Reduce costs and increase benefits