Plasticizers silicone adhesives

Chem. Descrip. Silicone resin sol n. in xylene, IPA, butyl alcohol Uses Dry-tilm release coating tor molding ot plastics or rubber adherent coating tor conveyors, chutes, and handling equip, used in rubber, plastics, and adhesives mtg. release agent tor electronic circuit board mfg. particle binder... 

Silicone adhesives cure without the application of heat or pressure to form permanently flexible silicone rubber. The rubber remains flexible despite the exposure to high or low temperatures, weather, moisture, oxygen, ozone, or UV radiation. This makes them useful for joining and sealing joints in which considerable movement can be expected, such as intermediate layers between plastics and other materials of construction (e.g., acryUc glazing). Several types of silicone adhesives/sealants are available, including one-part and two-part systems. 

In the quest for the ideal adhesive system to suit an application needs, it is essential to understand the effect of the silicone properties on the mechanisms of Silicone adhesion. The primary requirement for good adhesion is the creation of an intimate interface through Wetting and spreading of the silicone onto the substrate. The low surface tension and viscosity range of silicones satisfy this necessary condition. Therefore, the mechanical mechanism of adhesion is operative and plays a key role in adhesion of silicones to many different substrates such as leather, textile fabrics, porous metals like anodized aluminium, porous plastic and composite materials, and specialty papers like glassine, super calendered kraft and clay-coated papers. 

Silicone adhesives, one-pack, setting under the influence of atmospheric moisture. Uses glass, metals, ceramics, plastics some substrates need a priming coat. 

Silicone adhesives are useful in bonding metals, glass, paper, plastics, and rubbers, including silicone, butyl rubber, and fluoroelastomers. 

Smith, J. C., Silicone Adhesives for Joining Plastics, Adhesives Age, 27 (June 1974). 

The alkoxy silicone often showed a strength of 1.4 N/mm for many of the plastics tested but in this case the adhesive has failed cohesively. A silicone adhesive is often used where sealing might be the main priority of the adhesive rather than structural strength. 

Smith JS. Silicone adhesives for joining plastics. Adhes Age 1994 17(6) 27—31. 

Another type of sealant uses a combination of chemistry to yield a product useful as a sealant. This chemistry is a marriage of silicone and organic chemistry known as a polyether silicone. The basic polymer for this type of sealant is the reaction product of a polyether diol with a diisocyanate followed by further reaction with an amino-functional alkoxy silane. Thus, the central portion of this polymer is a polyether that is terminated with a urethane linkage that leads to the terminal group which is an alkoxy silane. This polymer can cure by the methods described above for a standard silicone but it contains the properties of a polyether. As with the normal silicones described above, these materials also have to be reinforced in order to obtain the tensile properties desired for a sealant. The same list of fillers as described above can be used in polyether silicones. Adhesion promoters such as silane coupling agents, diluents of various sorts, plasticizers, and catalysts are also added to these materials. 

The cyanoacrylate adhesives were introduced in the late 1950s. Unlike the epoxy or silicone adhesives, these materials contain a monomer that undergoes rapid polymerization at room temperatnre. The monomer ethyl cyanoacrylate is stable with trace amounts of an acid inhibitor snch as polyphosphoric acid. The commercial formulations may contain methyl and higher cyanoacrylate esters, thickeners such as organic polymers, and plasticizers for increased final film tonghness. A slightly basic surface is needed for ionic polymerization to occur. Even the snrface moisture of an ostensibly dry metal or ceramic surface is sufficiently basic. 

---