A Complete Guide to Silicone Adhesives

Component

Main Types / Ingredients

Functions & Description

Base Polymer

Siloxane polymers, methyl silicone rubber, methyl vinyl silicone rubber, phenyl silicone rubber, p-phenylene silicone rubber, phenylene ether silicone rubber, nitrile silicone rubber, fluorosilicone rubber; commonly used α,ω-dihydroxypolydimethylsiloxane (107 gum), methyl block room-temperature vulcanized silicone rubber (103 gum), silicone resin

The main component of adhesives that determines fundamental properties. 107 gum undergoes polycondensation with crosslinkers to form 3D elastomers, which can be used long-term at -70～200℃; incorporating methylphenylsiloxane segments improves heat resistance; silicone resin base materials are mainly applied for bonding metals and heat-resistant non-metallic materials.

Fillers

Nano calcium carbonate, light/heavy calcium carbonate, fumed silica (most commonly used, dosage: 5%～45% of base polymer), flame retardants, titanium dioxide, talc, quartz sand; special functional fillers: carbon nanotubes, graphene, nano alumina, hexagonal boron nitride, etc.

Reduce costs and enhance tear resistance (inhibit crack propagation and absorb energy); adjust density, heat resistance, permeability, adhesion, rheology and mechanical properties. Special fillers can endow the sealant with electrical conductivity, thermal conductivity or thermal insulation properties.

Curing Agent (Crosslinker)

Silanes with hydrolyzable groups, such as triacetoxysilane, tri / tetramethoxysilane, tri / tetraethoxysilane, tri / tetrabutanone oxime silane, etc.

Store hermetically under anhydrous conditions; hydrolyse and condense upon contact with moisture in air to rapidly cure the compound and form a three-dimensional network structure.

Tackifier

Silane coupling agents, silicone resins, titanates, boric acid or boron-containing compounds (dosage: ~2%～10% of base polymer)

Modify filler surfaces, improve compatibility between fillers and base polymer, and significantly boost the adhesive strength of the sealant to substrates.

Catalyst

Organometallic salts, including dibutyltin dilaurate, dibutyltin diacetate, stannous isooctanoate, organic titanium chelates (dosage: 0.1%～5% of base polymer)

Catalyse the polycondensation reaction between silanol groups and alkoxy groups to regulate vulcanisation speed; the curing rate of two-component RTV silicone rubber mainly depends on the type and dosage of catalyst.

Other Additives

Antioxidants, thermal stabilizers, colorants, etc.

Added according to specific application scenarios to improve auxiliary performances such as ageing resistance, thermal stability and colour appearance.