Butyl rubber primers

Laminated tapes In more general use now than pressure sensitive tapes are tapes consisting of polyvinyl chloride or polyethylene films in conjunction with butyl rubber. These tapes are applied with an adhesive butyl rubber primer. Thicknesses of up to 0-75 mm are in use and loose protective outer wraps of p.v.c. or polyethylene sheet are commonly applied. Tape quality control is exercised with reference to ASTM standard test methods and may include water vapour transmission rate and elongation. 

Generally, systems developed in the USA favour a combination of polyethylene with either butyl-rubber or hot-applied mastic adhesives, the latter consisting of a blend of rubber, asphalt and high molecular weight resins. In European and Far East coating plants, epoxy type primers and hard ethylene copolymer adhesives have been successfully employed. 

Substrates, Paints and Coatings. Both flash rusting and underfilm darkening studies exployed a white, pH 4.5, primer formulation (see Appendix), designated as Standard, based upon Haloflex 202, a chlorine-containing vinyl acrylic latex. A zinc phosphate free formulation, designated as Non-Standard, of pH6 was prepared by substitution of zinc phosphate for barytes. The comparison paints were a commercial butyl acrylate-methyl methacrylate water borne primer, formulated at pH 9, and a solvent based chlorinated rubber primer. 

Rubber range - vulcanised butyl rubber, CP, EPDM, CSM, NR, NBR and SBR rubbers. Substrate range - using Chemosil 211 primer, the PV bonding agents will bond ferrous and non-ferrous metals and plastics. They can be used as one-coat systems to bond vulcanised rubbers to themselves or to other vulcanised rubbers. 

Windshield sealants - One part polymethane sealants are the main product used in sealing auto windshields at the factory. They are used in conjunction with a silane primer to increase their adhesion to the metal frame. Butyl rubber tapes are used by repair shops to replace broken windshields. 

Surface Primers (Dick, 1987) - A surface primer is a coating applied to an adherend to improve an adhesive bond or subsequent coating. It is typically used where die adhesive and adherend have widely differing polarities, a butyl rubber adhesive on a steel surface for example. Primers are of two general types ... 

Chemical compatibility among the various materials used in a sealant joint is also paramount to a long life for the joint. The sealant and substrates must not only be chemically compatible but the choice of primer, bond breaker, and backing materials, where used, must also take into consideration chemical compatibility. The most typical offenders when it comes to chemical compatibility are plasticized sealants that contain species that are not chemically bound within the sealant and are free to diffuse into other surrounding materials (e.g., butyl rubber) and solvated sealants. 

Polychloroprene, nitrile, natural rubber, styrene butadiene rubber and butyl rubber can all be readily bonded with cyanoacrylates. EPDM and fluoroelastomers (such as Viton) can also be bonded, although only with specific grades of cyanoacrylate. The silicone rubbers and thermoplastic elastomers will usually require a primer but will also bond with cyanoacrylates. 

Uses Coupling agent esp. for polyolefins and polyolefin elastomers, min.-and glass-filled formulations, sealants (acrylic, SBR), rubbers (butyl, neoprene, isoprene, fluorocarbon), as primer coal for metals in insert molding... 

Uses Reinforcing agent, extender for plastics (acrylics, epoxy, nylon, phenolics, PC, polyester, PVC, urethane), rubbers (butyl, EPR, neoprene, nitrile, SBR, urethane), non-aq. coatings, adhesives and inks Features Provides additional barrier props, when used in primers and build coats... 

One-Component Polymerization Adhesives. Cyanoacrylate Adhesives. Methyl, ethyl, butyl, and methoxyethyl esters of cyanoacrylic acid are used for cyanoacrylate adhesives [44] soluble polymers and plasticizers are incorporated to regulate viscosity and for elastification. Cyanoacrylate adhesives rapidly polymerize by an ionic reaction mechanism initiated simply by weak bases to form high molecular mass, but largely uncross-linked polymers. In most cases, atmospheric moisture or the film of moisture on the substrate is sufficient to initiate polymerization, because the adhesives are applied in very thin layers. However, this sensitivity to atmospheric moisture means that the adhesives must be stored in tightly sealed form, usually in polyethylene bottles. Cyanoacrylates are used for bonding small items of nearly all substrates. In case of polyethylene or polypropylene special primers are available. Setting is complete with rubbers in seconds, with aluminum in less than one minute. 

Butyl Bonding rubber to itself and metals forms good bonding widi most plastic films such as polyediylene terephthalate and polyvinylidene chloride Excellent aging characteristics chemically cross-Unked materials have good thermal prc rties Metals should be treated with an appropriate primer before bonding attacked by hydrocarbons... 

---