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How to choose a suitable conductive glue?
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The adhesives used now are all multi-component synthetic resin adhesives, single-component adhesives can no longer meet the requirements in use.
Synthetic adhesives from the main agent and additives, the main agent is also known as the main material, base material or adhesive; additives have curing agent, diluent, plasticizer, filler,
coupling agent, initiator, thickener, antioxidant, polymerization inhibitor, stabilizer, complexing agent, emulsifier, etc.
According to the requirements and uses can also include flame retardants, foaming agents, defoamers, colouring agents and mould inhibitors and other components.
1. Main agent
The main agent is the main component of the adhesive, the dominant adhesive bonding performance, but also an important symbol to distinguish the type of adhesive.
The main agent is generally composed of one or two, or even three polymers, and requires good adhesion and wettability. Usually used adhesive materials are:
-Natural polymer compounds
Such as protein, hide glue, fish glue, rosin, peach gum, bone gum, etc.
2) Synthetic polymer compounds (e.g. BERGQUIST GF3500S35, GAP FILLER 3500S35, GAP FILLER TGF 3600)
① Thermosetting resins, such as epoxy resins, phenolic resins, polyurethane resins, urea-formaldehyde resins, silicone resins, etc.
②Thermoplastic resins, such as polyvinyl acetate, polyvinyl alcohol and acetal resins, polystyrene, etc.
③ elastic materials, such as nitrile rubber, neoprene, polysulfide rubber, etc.
④A variety of synthetic resins, synthetic rubber mixture or graft, inlay and copolymer, etc.
2. Additives (e.g. BERGQUIST GAP FILLER 4000, BERGQUIST LIQUI-FORM 3500)
The various auxiliary components added to meet specific physicochemical properties are called auxiliaries, e.g. to form a net or
body structure for the main adhesive, to increase the cohesive strength of the layer.
curing agents (which react with the main adhesive and produce cross-linking) in order to increase the cohesive strength of the adhesive layer;
curing accelerators or catalysts in order to accelerate curing and reduce the reaction temperature.
To improve the resistance to atmospheric ageing, thermal ageing, arc ageing, ozone ageing and other properties and the addition of antioxidants;
in order to give the adhesive some specific properties, reduce costs and the addition of fillers.
To reduce the rigidity of the rubber layer, increase the toughness and add toughening agents; in order to improve the process to reduce viscosity,
extend the service life of adding diluent. Including.
(1) curing agent
Curing agent, also known as hardener, is to promote the bonding of material through chemical reactions to speed up the curing of components,
it is the most important adhesive with the material.
Its role is directly or through the catalyst and the main polymer reaction, after curing the curing agent molecules into the resin,
so that the original is a thermoplastic linear polymer into a tough and hard body-shaped network structure.
There are many different types of curing agent, and different resins and different requirements use different curing agents. The process of gluing and
its use of performance is determined by the performance of the curing agent and the number of people to add
2) Toughening agents
Toughening agent of the active group directly involved in the curing reaction of the adhesive, and into the final formation of the curing product of
a large molecule in the chain structure.
Without the addition of toughening agent adhesive curing, its performance is more brittle, easy to crack, poor practicality.
Add toughening agent adhesive, have better impact strength and peel resistance.
Different toughening agents can also reduce its internal stress, curing shrinkage to varying degrees, to improve low-temperature performance.
Commonly used toughening agents are polyamide resin, synthetic rubber, acetal resin, polysulfone resin, etc.
(3) Diluent
Diluents, also known as solvents, the main role is to reduce the viscosity of adhesives, increase the ability of adhesives to wet,
improve process performance. Some can reduce the activity of the adhesive, thereby extending the use period.
However, adding too much, will reduce the adhesive bonding strength, heat resistance, media resistance performance.
Commonly used diluents are acetone, lacquer and other solvents compatible with the adhesive.
(4) filler
Fillers generally do not occur in the adhesive chemical reaction, the use of fillers can improve the strength of the adhesive joint,
impact toughness, wear resistance, aging resistance, hardness, the
Maximum use temperature and heat resistance, reduce the coefficient of linear expansion, curing shrinkage and cost, etc. Commonly
used fillers include copper oxide, magnesium oxide, silver powder, porcelain powder, mica powder, asbestos powder, talcum powder, etc.
(5) modifier
Modifier is to improve the performance of a particular aspect of the adhesive to meet the special requirements and the addition of some components,
such as to increase the strength of the bond, can be added to the coupling agent.
Can also add preservatives, anti-mildew agents, flame retardants and stabilizers.
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