Polychloroprene rubber adhesives: applications

Further information on rubber-based adhesives is to be found in specialized articles Natural Rubber-Based Adhesives, Nitrile Rubber Adhesives, Polychloroprene Rubber Adhesives Applications and Properties and Polychloroprene Rubber Adhesives Modifiers and Additives. 

It is interesting to compare the properties of NBR adhesives with those of another polar rubber Polychloroprene rubber adhesives applications and properties. 

Most Rubber-based adhesives may be cured by a sulphur-based vulcanizing system (see Rubber-based adhesives compounding), however, as mentioned in Polychloroprene rubber adhesives applications and properties, CR adhesives are cross-linked by various reactions involving the labile chlorine atoms in the repeat unit. This is reflected in the additives used, as discussed below. ... 

During the World War II, several new synthetic elastomers were prodnced, and new types of adhesives (mainly styrene-butadiene and acrylonitrile copolymers (see Nitrile rubber adhesives)) were manufactured to produce adequate performance in joints produced with new difficult-to-bond substrates. Furthermore, formulations to work under extreme enviromnental conditions (high temperature, resistance to chemicals, improved resistance to ageing) were obtained using polychloroprene (Neoprene) adhesives (see Polychloroprene rubber adhesives applications and properties and Polychloroprene rubber adhesives modifiers and additives). Most of those adhesives need vnlcanization in order to perform properly. 

Polychloroprene rubber (CR) is the most popular and versatile of the elastomers used in adhesives see Polychloroprene rubber adhesives applications and properties and Polychloroprene rubber adhesives modifiers and additives. 

The polychloroprene latex determines the initial tack and open time, the bond-strength development and hot bond strength, the application properties, and the adhesive s viscosity. Because most latices have low viscosities by compounding, most of the water-borne polychloroprene rubber adhesives are sprayable. Thickeners such as fumed silicas can be added to increase viscosity and thixotropy. 

Butyl phenolic resin is a typical tackifier for solvent-borne polychloroprene adhesives. For these adhesives, rosin esters and coumarone-indene resins can also be used. For nitrile rubber adhesives, hydrogenated rosins and coumarone-indene resins can be used. For particular applications of both polychloroprene and nitrile rubber adhesives, chlorinated rubber can be added. Styrene-butadiene rubber adhesives use rosins, coumarone-indene, pinene-based resins and other aromatic resins. 

Several elastomers can be used in rubber-based adhesives. The elastomer provides the backbone of the adhesive, so the main performance of the adhesive is provided by the rubber properties. However, several specific properties for application are imparted by adding other ingredients in the formulations. The most common elastomers used in rubber-based adhesives are natural rubber (NR), butyl rubber (BR) and polyisobutylenes, styrene-butadiene rubber (SBR), nitrile rubber (NBR) and polychloroprene rubber Neoprene) (CR). 

Polychloroprene rubbers find use in such applications as cable-sheaths, hose and weather strips. Latices are used in the production of dipped goods, such as gloves and balloons, foams, adhesives and corrosion-resistant coatings. 

Structural applications of rubber base adhesives were also obtained using rubber-thermosetting resin blends, which provided high strength and low creep. The most common formulations contain phenolic resins and polychloroprene or nitrile rubber, and always need vulcanization. 

During World War II, polychloroprene was chosen as a replacement for natural rubber because of its availability. Two copolymers of chloroprene and sulphur which contain thiuram disulphide were available (Neoprene GN and CG). One of the first successful applications of these polychloroprene adhesives was for temporary and permanent sole attachment in the shoe industry. However, these polychloroprene cements show a decrease in viscosity on ageing and a black discolouration appears during storage in steel drums. Discolouration was produced by trace amounts of hydrochloric acid produced by oxidation of polychloroprene... 

Ethylenethiourea has a wide variety of uses in addition to vulcanization, a principal application since 1948. The curing process converts most of the ETU to other compounds, but traces of it are still found in the rubbers. Neoprene (polychloroprene) is found largely in automotive parts, wire and cable insulation, construction and adhesives. Consumer products containing neoprenes include container seals (e.g., aerosol dispensers) and shoes. It is also an intermediate in the manufacture of antioxidants, dyes, fungicides, insecticides, pharmaceuticals, synthetic resins, and a constituent of plating baths. 

Chloroprene rubber, polychloroprene (CR). A syniheXic rubber produced by polymerization of chloroprene (2-chlorobutadiene, CH2=CCl—CH = CH 2). High weather and chemical resistance, better oil resistance than that of natural rubber products. Some applications building sheets, belts, cable insulations, technical rubber goods, contact adhesives. Trade names Baypren (FRG), Neoprene (USA). 

Bonding Soles to the Lasted Uppers. Polychloroprene and polyurethane solvent adhesives, occasionally also dispersions of the same polymers, are used for this purpose. Various pretreatments are used to improve the bond application of a thin first coat of adhesive, especially for absorbent surfaces priming, in particular the halogenation of vulcanized rubber and thermoplastic rubber soling the use of base-coat primers for nylon and other synthetics, as well as UV-curing primers for EVA and other substrates in athletic footwear. 

With the development of synthetic elastomers during World War II, new types of adhesives appeared for application to a broader range of substrates and for use at higher temperatures. Styrene-butadiene and butadiene-acrylonitrile copolymers found application in new adhesives. There were also significant concurrent developments in adhesives based on chlorinated rubber, polychloroprene (neoprene), and poly sulfide rubber. Development of carboxylic elastomers, silicone rubbers, and polyurethanes followed. 

Solvent cements encompass a wide range of performance properties, from the simple natural rubber based cements which are widely used for low performance applications in homes and schools to the structural applications of contact adhesives based on polychloroprene and reactive phenolic resins. 

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