Sealant polysulfide

Polysulfide sealants Polysulfide units Polysulfonates Polysulfone... 

Besides water vapor and gas diffusion, other requirements for good edge sealants are water resistance, uv resistance, heat/cold resistance (—40 to 80°C), adhesion to glass and metal, and good characteristics for appHcation. Polysulfide sealants have maintained an exceUent record in use since the 1950s. Development of new polysulfides and sealant formulations continues in order to meet market needs of the 1990s. 

Sealants obtained by curing polysulfide liquid polymers with aryl bis(nitrile oxides) possess stmctural feature of thiohydroximic acid ester. These materials exhibit poor thermal stability when heated at 60°C they soften within days and liquefy in 3 weeks. Products obtained with excess nitrile oxide degrade faster than those produced with equimolar amounts of reagents. Spectroscopic studies demonstrate that, after an initial rapid addition between nitrile oxide and thiol, a second slower reaction occurs which consumes additional nitrile oxide. Thiohydroximic acid derivatives have been shown to react with nitrile oxides at ambient temperature to form 1,2,4-oxadiazole 4-oxides and alkyl thiol. In the case of a polysulfide sealant, the rupture of a C-S bond to form the thiol involves cleavage of the polymer backbone. Continuation of the process leads to degradation of the sealant. These observations have been supported by thermal analysis studies on the poly sulfide sealants and model polymers (511). 

Since the introduction of the first polysulfide sealants in the 1950s, the sealant market had grown by 1992 into a 1.4 billion industry. Sealant use is generally divided into four categories transportation, construction, consumer, and industrial. Table 9 lists the market segment value of each use as of 1992 and Table 10 the market share of the various material types. Continued growth is expected, especially for silicones, urethanes, and acrylics. Table 11 lists suppliers of sealants. 

An important application of calcium peroxide is for curing the polysulfide sealants used in double-glazing window units. Calcium... 

Titanates have been instrumental in the bonding of fluorinated resins to packaging films, poly(hydantoin)—polyester to polyester wire enamel, polysulfide sealant to polyurethane (a phosphated titanate is recommended), polyethylene to cellophane using a titanated polyethylenimine, and silicone mbber sealant to metal or plastic support using polysilane (Si—H) plus polysiloxane (Si—OR) and titanate as the adhesive ingredients (450—454). Polyester film coated first with a titanium alkoxide, then with a poly(vinyl alcohol)—polyethylenimine blend, becomes impermeable to gases (455). 

Lee, T, Rees, T. and Wilford, A. (1992) Polysulfide sealants in water-retaining structures, in Science and Technology of Building Seals, Sealants, Glazing and Waterproofing, ASTM STP 1168, American Society of Testing and Materials, Philadelphia, PA, pp. 47-56. 

Panek, J. and Cook, J. (1984) Polysulfide sealants, in Construction Sealants and Adhesives, 2nd edn, John Wiley, New York, pp. 106-19. 

Hanhela, P.J., Hook, R.J. and Paul, B. (1994) Polysulfide sealant compositions interactions between elemental sulfur and organosulfur compounds. Journal of Applied Polymer Science, 51(8), 1441-52. 

This chapter will deal with the chemistry and applications of epoxies, phenolics, urethanes, and a variety of current vogue high-temperature polymers. Applications in fiber-reinforced plastics will be discussed in the individual sections on resin chemistry where appropriate. Separate sections will deal with adhesives and sealants. Adhesives are most important because, as early history demonstrates, they led the way to the application of resins in aerospace. A section is also included on silicone and polysulfide sealants. Although these materials are elastomers rather than resins, no discussion of aerospace polymers would be complete without some mention. Some major thermosetting polymers have been omitted from this review. Among these are the unsaturated polyesters, melamines, ureas, and the vinyl esters. Although these products do find their way into aerospace applications, the uses are so small that a detailed discussion is not warranted. 

Cal-Seal. [Calbar] Butyl, acrylic, polysulfide sealants. 

The classes of fillers used in formulating polysulfide sealants include ... 

Many environmental factors such as moisture and temperature determine the long term adhesion of polysulfide sealants. It is necessary that the substrates be properly prepared surfaces must be clean and structurally sound. To wet the surface and permit the adhesion additives to migrate to the surface, the sealant must have the necessary rheology and cure properties. 

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