Polysulfide curing agents

The second catalyst paste of the two-paste product is a curing agent. A wide variety of materials convert the Hquid polysulfide polymers to elastomeric products. Alkalies, sulfur, metallic oxides, metallic peroxides, organic peroxides, and many metal—organic salts, ie, paint driers, are all potential curing agents. 

Many curing systems bring about aHquid—to—soHd conversion of the polysulfide polymers. Most curing agents produce an initial soHd mass characterized by a high degree of plasticity and poor elasticity. The development of elastic properties is so slow that the materials are not suitable for the accurate reproduction of undercut areas found ia oral stmctures. 

Only two types of systems have found appHcation ia dentistry. Lead peroxide is the curing agent most frequently used for the polysulfide polymers that serve as dental impression materials. Lead peroxide converts the Hquid polymer to an elastic soHd within a time short enough for oral appHcations. 

Aliphatic aldehydes, 13 571 physical properties of, 2 60t syntheses of, 12 187 Aliphatic a-hydroxy acids, 14 130 Aliphatic amine/polysulfide co-curing agent systems, 10 410... 

Formulation. Polysulfide-based sealants are formulated with appropriate ingredients to obtain the desired properties for a particular application. A typical formulation contains liquid polysulfide polymer, curing agent, cure accelerators (bases) or retarders (acids), fillers, plasticizers, thixotropes, and adhesion promoters. 

Water Dispersions. Polysulfide products are offered as aqueous dispersions (Thiokol WD-6). These are useful for applying protective coatings to line fuel tanks, and for concrete, wood, and in some cases fabrics, felt, leather (qv), and paper (qv). It has been found that a stable emulsion can be made that contains both LP and manganese oxide curing agent. The emulsion can be thinned and applied as a spray coating. After it is applied, water evaporates and the LP cures to form a solid mbber (13). 

Polysulfide resin, on the other hand, does not have fast and low-temperature curing properties. It is used as more of a flexibilizer than a curing agent. However, polysulfide resins do have mercaptan groups, and these enter into the epoxy cure reaction. 

Starting formulation for a flexible epoxy adhesive containing polyamide curing agent and reactive diluent Starting formulation for a high-peel-strength adhesive Epoxy-polysulfide adhesive formulation Formulation for a flexible epoxy-polysulfide adhesive Epoxy-polysulfide adhesive formulations... 

LP-lOO, 200, 300, 400. [ e-Picher] Lead dioxide catalyst, curing agent for polysulfide, butyl and polyisoprene rubber oxidizer for mfg. of dyes. 

The polysulfide sealant must be specifically formulated to meet the desired requirements and to obtain optimum properties. Pot life, working properties, and sealant properties should be properly adjusted. Suitable fillers should be dispersed and suitable additives should be incorporated into the formulation. Curing agent, curing modifier, filler, plasticizer, and adhesion additive are diseussed briefly below. 

Precaution Oxidizer explosive reaction with warm K or Na violent reaction with N compds., ground sulfur, powd. Al, etc. can react vigorously with reducing materials Hazardous Decomp. Prods. Heated to decomp., emits toxic fumes of Pb Uses Catalyst, curing agent for polysulfide,... 

Triethylamine Trimethylolpropane trithioglycolate curing agent, polysulfide Lead dioxide... 

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