Silicone rubber primers

Uses Filler for coatings (metal finishes, primers, interior/exterior architectural, marine, protective, maintenance), plastic film antiblocks, silicone rubber, adhesives... 

These are generally bonded with silicone adhesives, either silicone rubber or silicones. Primers should be used before bonding. 

Fluorosilicone and silicone rubbers must be primed before bonding. The primer acts as an intermediate interface, providing good adhesion to the rubber and a more wettable surface for the adhesive. 

Liquid silicone rubbers (LSRs) are two-part grades which can be coinjection-molded with thermoplastics to make door locks and flaps for vents.1 LSRs can be biocompatible and have low compression set, low durometer hardness, and excellent adhesion. One-part silicones are cured by ambient moisture. They are used for adhesives and sealants with plastic, metal, glass, ceramic, and silicone mbber substrates. A solventless, clear silicone/PC has been developed which requires no mixing, and can be applied without a primer. ... 

Polychloroprene, nitrile, natural rubber (polyisoprene), styrene butadiene rubber (SBR) and butyl are amongst the types of rubber that can be readily bonded with cyanoacrylates. Ethylene propylene diene monomer (EPDM) and fluroelastomers (Viton, registered trade mark of DuPont) can also be bonded, although only with specific grades of cyanoacrylate. Silicone rubber and thermoplastic rubber (Santoprene, registered trade mark of Advanced Elastomer Systems) can be bonded with the aid of a primer. Typical applications and techniques for bonding different grades of rubber are discussed in Section 10.11. 

Examples in industry include attaching a silicone rubber seal to an aluminium parachute container. A primer is brushed on to the silicone rubber and the cyanoacrylate is applied to the aluminium. Once fully cured the bonded seal assembly prevents dust or moisture entering the safety critical box. 

Silicone rubber is often used in medical devices as it offers good flexibility, a degree of softness (for face masks, etc.) and good resistance to both EtO and gamma radiation sterilisation processes. Silicone rubber can be bonded with the aid of a primer (see Section 10.6). 

The bonding is achieved by different methods. The hard component can contain undercuts where the rubber is anchored during its vulcanisation, a primer on the hard component or even using self-adhesive silicone rubber will give sufficient anchorage. 

This chapter will focus on LR, because it is the most sophisticated material among silicone rubbers used in moulded parts. It shows very productive processability (short cycle times, no post-treatment like deflashing is needed), it allows use of complex geometry and, moreover, waste free production of two component applications (soft and hard or soft and soft) in only one machine without the need for a primer. In order to combine silicone... 

In such cases the processor basically has the choice between undercuts, primers or primerless self-adhesive silicone rubber. 

The application of primers does not allow for the injection moulding of the substrate on the same machine as the silicone rubber part. 

When working with standard silicone rubbers stronger adhesion to smooth surfaces is observed. However, cohesive failure is never found when separating the rubber from a substrate which has not previously been primered. 

In this case self-adhesive HTV is used as a substitute to the primer. As it is chemically different from primers, which are not silicone rubbers, it is considered in this section. 

Compound, caulking, conductive Compound, polyurethane Compound, heat sink, silicone Compound, sealing, poly sulfide rubber Compound, plastic polyurethane Primer, silicone rubber sealant Primer, polyurethane Primer, silicone... 

Sealant, ablative, silicone base, room temperature curing and primer Sealant, silicone rubber, room temperature vulcanizing Sealing compound, high tear strength Sealant, electrically conductive... 

Prism 757 Polyolefin Primer enables the polyolefins polythene and polypropylene to be succesfully bonded as well as silicone rubber and claims to also bond to PTFE. 

Prime coating is either a two-pack, zinc-rich epoxy primer with a DFT of ca. 30-40 pm, or a chromate-free, two-pack epoxy primer. Topcoats based on PVC copolymerisates, chlorinated rubber, silicone-reinforced epoxy esters, or alkyds were used for many years. Now, the standard European topcoat is based on acrylic resins with terminal epoxy groups that are cross-linked with amine adducts or aminoamide resins. 

Uses Pesticide intermediate mfg. of phenol, chloronitrobenzene, aniline, DDT, silicone resins, dyes, perfumes, polysulfone solvent carrier for methylene diisocyanate solvent for paints, pesticides, degreasing processes, pharmaceuticals heat transfer medium adhesive rubbers and adhesives primer or adhesive additive for adhering elastomeric coatings to syn. fiber fabrics coated with syn. rubber surf, coating dry cleaning intermediate for halogen synthesis in food-pkg. adhesives adjuvant for PC food-pkg. resins solvent in food-contact polysulfone rGsins... 

The adhesives will bond almost all materials (though a primer may be needed with some), except polyolefin plastics (eg Polythene) and other low surface-energy types such as fluoropolymers (eg Teflon) and silicone-based rubbers. Alkaline glass may cause premature bond failure and all glasses should be silane primed if at all possible, as this considerably improves the joint s humidity resistance. May stress crack stressed mouldings or susceptible plastics - polycarbonate, for example. 

Figure 11.4 Silicone roller with primer - rubber peeled off entirely...

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