Rubber in adhesives

Used industrially as a chemical intermediate in the production of rayon, carbon tetrachloride, xanthogenates, flotation agents, and pesticides used in the cold vulcanization of vulcanized rubber, in adhesive compositions for food packaging as a solvent for phosphorus, sulfur, selenium, bromine, iodine, fats, resins, rubbers, waxes, lacquers, camphor, resins and in the production of optical glass, paints, enamels, varnishes, paint removers, tallow, putty preservatives, rubber cement, soil disinfectants, explosives, rocket fuel, and electronic vacuum tubes. 

Developments in cellulose ester adhesives and alkyd resin adhesives Cyclized rubber in adhesives (Fischer-Goodrich Co.)... 

Uses Modifier of PP, PVC, PE, PS, and high-performance engineering resins antioxidant heat stabilizer UV stabilizer vise, depressant antiblocking agent in rubbers in adhesives for food pkg. emollient, protective film-former for skin in cosmetic creams and lotions used in hot-melt and solv.-based coatings textile/leather lubricants and finishes chemical intermediate defoamerfor pulp/paper processing... 

Uses rubber vulcanization accelerator for natural rubber, styrene-butadiene, and butyl rubber in adhesives including those used in food packaging, paper coats for non-food contact, industrial cooling water, latex-coated articles, neoprene, paper and paperboard, plastics (polyethylene and polystyrene), and textiles agricultural fungicide for seed, plants, and fruits repellant to birds and rodents. 

Hycar Manual HM-12, Hycar Nitrile Rubber in Adhesives, BFGoodrich Company, Elastomers and Latex Division. 

The behavior of thermoplastic rubber in adhesives is dependent on (1) the morphology or geometry of the submicroscopic endblock phase as it is dispersed in the rubber matrix, and (2) the compatibility of added ingredients with the two phases present. These topics are discussed in subsequent sections. 

The situation did not change until 1942, soon after the start of World War II. At that time, a critical shortage of natural rubber developed because it was allocated chiefly for the war effort. Neoprene was chosen as a replacement for natural rubber in adhesives because it was the only other synthetic rubber available. Animal glue and other water-soluble materials available at the time were unsatisfactory because of their slow drying rates, poor adhesion to many surfaces, inflexible films, and rusting of metals. The two Neoprene polymers available at the time were Neoprene GN, a general purpose type, and Neoprene CG, a fast-crystallizing type. Both are copolymers of chloroprene and sulfur which contain a thiuram disulfide modifier. 

Harlan, J.T. and Petershagen, L.A., 1977, "Thermoplastic Rubber in Adhesives", Handbook of Adhesives, 2nd ed., I. Skeist(ed.), Van Nostrand Reinhold, New York, pp 304-330. Kilchesty, A.A., 1986, "Oleo Resinous and Oil-Base Caulking Compounds", Caulks and Sealants Short Course, Adhesive md Sealant Council, Washington, E)C, Dec.,pp 13-23. Kilchesty, A.A., 1986A, "Solvent Aeryhcs", ibid, pp 77-84. 

Butyl mbber, a copolymer of isobutjiene with 0.5—2.5% isoprene to make vulcanization possible, is the most important commercial polymer made by cationic polymerization (see Elastomers, synthetic-butyl rubber). The polymerization is initiated by water in conjunction with AlCl and carried out at low temperature (—90 to —100° C) to prevent chain transfer that limits the molecular weight (1). Another important commercial appHcation of cationic polymerization is the manufacture of polybutenes, low molecular weight copolymers of isobutylene and a smaller amount of other butenes (1) used in adhesives, sealants, lubricants, viscosity improvers, etc. 

The poly(vinyl ethers), whieh were first made available in Germany before 1940, are not of importance in the plastics industry but have applications in adhesives, surfaee coatings and rubber technology. Of the many vinyl ether polymers prepared, only those from the vinyl alkyl ethers and some halogenated variants are of interest. Two methods of monomer preparations may be used. 

The work of adhesion was determined from the a versus P measurements (see Eq. 11). The work of adhesion between two rubber spheres was found to be 71 4 mJ/m. The work of adhesion reduced to 6.8 0.4 mJ/m in the presence of 0.01 M solution of dodecyl sulfate. Using these measurements of adhesion between rubber in air and a surfactant solution, Johnson et al. [6] provided the first direct experimental verification of the Young s equation (Eq. 40). They also measured... 

Many applications of XPS to problems in adhesion science have been reported in the literature. One interesting example is provided by the work of Tsai et al. on the use of XPS to investigate reactions between model rubber compound and plasma polymerized acetylene films that was discussed above [22,23], Consideration of that system permits some interesting comparisons to be made regarding the type of information that can be obtained from RAIR and XPS. 

Rubber base adhesives, also called elastomeric adhesives, are widely used in industrial and household applications. In fact, about one-third of the adhesives used in the World are made from natural or synthetic rubbers. Some of the elastomeric adhesive systems showing industrial importance in recent years are the following ... 

Some rubber base adhesives need vulcanization to produce adequate ultimate strength. The adhesion is mainly due to chemical interactions at the interface. Other rubber base adhesives (contact adhesives) do not necessarily need vulcanization but rather adequate formulation to produce adhesive joints, mainly with porous substrates. In this case, the mechanism of diffusion dominates their adhesion properties. Consequently, the properties of the elastomeric adhesives depend on both the variety of intrinsic properties in natural and synthetic elastomers, and the modifying additives which may be incorporated into the adhesive formulation (tackifiers, reinforcing resins, fillers, plasticizers, curing agents, etc.). 

The chemical nature and molecular weight of the rubber will greatly determine the properties of elastomeric adhesives. However, some common characteristics can be found in most of the rubber base adhesives. The elastomeric adhesives show the following specific features in assembly operations. 

Variety of form. Rubber base adhesives can be supplied for assembly operations as solvent or water-borne dispersions, hot melts, precast films, extruded tapes or reinforced films. In addition solvent and water-borne dispersions can be supplied as single or two-components systems. 

Rubber base adhesives develop strength faster than most other polymeric types. Fig. 1 [3J shows the differences in the development of peel strength for several rubber polymers (without additional additives, except an antioxidant). Natural... 

In the next sections, the manufacture, chemistry and properties of the main ingredients of the rubber base adhesives will be considered. 

Several elastomers can be used in rubber base adhesives. The elastomer used is the backbone of the adhesive, so the performance of the adhesive is provided... 

Some properties of elastomers used in rubber base adhesives... 

The elastomers considered in this section have been selected considering the most commonly used in rubber base adhesives natural rubber butyl nibber and polyisobutylenes styrene-butadiene rubber nitrile rubber polychloroprene rubber (neoprene). Typical properties of these rubbers are shown in Table 2. 

Butyl rubber (BR) and polyisobutylene (PIB) are widely used in adhesives as primary elastomeric binders and as tackifiers and modifiers. The main difference between these polymers is that butyl is a copolymer of isobutylene with a minor amount of isoprene (which introduces unsaturation due to carbon-carbon double bonds), while polyisobutylene is a homopolymer. 

Polychloroprene rubber (CR) is the most popular and versatile of the elastomers used in adhesives. In the early 1920s, Dr. Nieuwland of the University of Notre Dame synthesized divinyl acetylene from acetylene using copper(l) chloride as catalyst. A few years later, Du Pont scientists joined Dr. Nieuwland s research and prepared monovinyl acetylene, from which, by controlled reaction with hydrochloric acid, the chloroprene monomer (2-chloro-l, 3-butadiene) was obtained. Upon polymerization of chloroprene a rubber-like polymer was obtained. In 1932 it was commercialized under the tradename DuPrene which was changed to Neoprene by DuPont de Nemours in 1936. 

Resins used in rubber base adhesive fonnulations have the following characteristics [16] ... 

Rosins and rosin derivatives. The resins more commonly used in rubber base adhesives are rosin esters, particularly glycerol and pentaerythritol esters, as well as rosins modified by disproportionation and hydrogenation. The glycerol ester of hydrogenated rosin has been reported to be an excellent tackifier for polychloroprene adhesives (see pp. 344-357 in [17]). 

Plasticizers reduce hardness, enhance tack and reduce cost in rubber base adhesive formulations. A plasticizer must be easily miscible and highly compatible with other ingredients in the formulations and with the surfaces to which the adhesive is applied. The compatibility and miscibility of plasticizers can be estimated from the solubility parameter values. Most of plasticizers have solubility parameters ranging between 8.5 and 10.5 hildebrands. However, the high miscibility and compatibility also lead to easier diffusion of the plasticizer to the surface, decreasing the adhesion properties. Therefore, plasticizers should be carefully selected and generally combinations of two or more of them are used. 

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