Cure accelerators

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

The manufacture of the majority of fluorocarbon elastomer gums includes the addition of an incorporated cure system comprising an organic onium cure accelerator, such as triphenylbenzylphosphonium chloride [1100-88-5] and a bisphenol cross-linking agent, such as... 

Resoles are usually those phenolics made under alkaline conditions with an excess of aldehyde. The name denotes a phenol alcohol, which is the dominant species in most resoles. The most common catalyst is sodium hydroxide, though lithium, potassium, magnesium, calcium, strontium, and barium hydroxides or oxides are also frequently used. Amine catalysis is also common. Occasionally, a Lewis acid salt, such as zinc acetate or tin chloride will be used to achieve some special property. Due to inclusion of excess aldehyde, resoles are capable of curing without addition of methylene donors. Although cure accelerators are available, it is common to cure resoles by application of heat alone. 

A new process to develop interface vulcanization is grafting of selective accelerators onto a polymer chain, which in the subsequent process of vulcanization acts as an effective cure accelerator for the second polymer component in the blend. Beniska et al. [6] prepared SERFS blends where the polystyrene phase was grafted with the accelerator for curing SBR. Improved hardness, tensile strength, and abrasion resistance were obtained. Blends containing modified polystyrene and rw-1,4-polybutadiene showed similar characteristics as SBS triblock copolymers. 

Cross-linking agents and cure accelerators (rubber) 585... 

The gluability of the lignin-epoxy resin adhesives was found to be improved by the addition of calcium carbonate (50% by weight) to the liquid resin. This must be attributed to the nature of the weak alkali in calcium carbonate as a cure accelerator, and to the reinforcement effect of fillers. Since wood surfaces are acidic, the addition of alkaline fillers effectively alters the pH of the glue line. 

In the US the, Thiokol Chemical Corp, Trenton, NJ proposed it as a curing accelerator in some of their Polysulfide Composite Propellants . The composition and properties of these propints are given in conf Propint Manual SPIA/M2 (1962) (Unit Nos 618, 619,... 

A composition is prepared by dissolving the MMBS modified thermoset resin in acetone. To the resulting solution, additives may be added, for example, pigments, flame retardants, lubricants or cure accelerators, e.g., hexamethylenetetramine. 

ZnO is of considerable commercial importance and applications relevant to this chapter include a variety of uses in the rubber industry as a curing accelerator, adhesive and stabilizer. It is also important in the manufacture of other zinc compounds and is increasingly being used in photocopying.121 For its applications as a pigment see Chapter 58. ZnS is an important phosphor. Zinc borate is used in fireproofing fabrics and in fire-retarding paints.121... 

The cyclic alkylene carbonates have also been applied as the cure-accelerators of phenol-formaldehyde (PF) [262-266] and sodium silicate [267] resin systems, which are widely used in foundry sand and wood binder applications. 

Gilman, J, Davis, R, and Montgomery, C. 2004. High throughput screening methods for military aircraft topcoat cure accelerator, 2004 Coatings Project Final Report, http //fire.nist.gov/bfrlpubs/... 

Two-layered GRPs for copper clad laminates are obtained with one layer consisting of the three-component system (e.g. BPA/DC, BMI, brominated epoxide resin, Zn octoate and triethylenediamine in methylethylketone). The other layer has the usual epoxy matrix (brominated epoxide resin, dicyandiamide as a hardener and 2-ethyl-4-methylimidazole as curing accelerator) [119]. As similar two-layered laminate contains BPA/DC, BMI, epoxynovolak resin, Zn acetate and triethylenediamine in the first layer and BPA/DC only with the same catalysts in the second layer [120]. 

Accelerators are often used to increase the reactivity of epoxy-anhydride systems. The proper amount of cure accelerator is empirically determined and varies according to the material being used as the accelerator, the anhydride and epoxy resin used, and the desired cure speed and end properties. 

Solvent Solutions. Certain solvent solutions of aromatic amines have been noticed to polymerize epoxy resins at room temperature.11 The effect of the solvent is probably to allow sufficient mobility of the polymer chains for an adequate degree of crosslinking to occur before the viscosity becomes so high that the molecules are immobilized. The aromatic amine solutions are usually used with a cure accelerator to achieve practical cure rates at room temperature. 

A typical cationic uv adhesive formulation contains an epoxy resin, a cure-accelerating resin, a diluent (which may or may not be reactive), and a photoinitiator. The initiation step results in the formation of a positively charged center through which an addition polymerization reaction occurs. There is no inherent termination, which may allow a significant postcure. Once the reaction is started, it continues until all the epoxy chemistry is consumed and complete cure of the resin has been achieved. Thus, these systems have been termed living polymers. 

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