Nitrile Rubber Adhesive

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. 

Nitrile rubber adhesives. The main application corresponds to laminating adhesives. PVC, polyvinyl acetate and other polymeric films can be laminated to several metals, including aluminium and brass, by using NBR adhesives. NBR adhesives can also be used to join medium-to-high polarity rubbers to polyamide substrates. The adhesive properties of NBR rubbers can be further improved by chemical modification using polyisocyanate or by grafting with methyl methacrylate. 

Plasticizer migration from the vinyl part into the adhesive bond line can degrade the strength of the joint. Adhesives must be tested for their ability to resist the plasticizer. PVC can be made with a variety of plasticizers. An adhesive suitable for a certain flexible PVC formulation may not be compatible with a PVC from another supplier. Nitrile rubber adhesives have been found to be very resistant to plasticizers and are often the preferred adhesive for flexible PVC films. However, certain epoxy adhesive formulations have also been found to provide excellent adhesion to flexible PVC substrates. Several such starting formulations are presented in Table 16.7. A comparison of the performance of several classes of adhesive when bonding PVC to itself and to various other materials is given in Table 16.15. 

Acrylonitrile 1,3-Butadiene HjOCHCN H2C=CHCH=CHa Nitrile rubber Adhesives, gasoline hoses... 

Polyvinyl Chloride (PVC) With PVC plasticizer migration to the adhesive bond line can cause difficulties, especially in the softer, highly plasticized materials. Adhesives must be tested for their ability to resist the plasticizer. Nitrile-rubber adhesives are resistant to plasticizers. Polyurethanes and neoprenes are also used. Even rigid PVC contains up to 5% plasticizer. Most vinyl materials are fairly easy to... 

Latex adhesives, of which there are many types (Nitrile rubber adhesives (NBR), SBR, Ethylene-vinyl acetate copolymers, acrylics, polyvinylidene chloride, etc.), should ideally be cross-linkable (for wash and dry-clean resistance), preferably with a low cure (reaction) temperature (see Reaction setting adhesives), as some fibres, such as polypropylene, may be damaged by high temperatures. The binder (adhesive) type can markedly affect physical properties and performance the amount of hard and soft polymer in the binder controls the sofmess of the finished product. Most binders impart adequate dry-state adhesion and so the choice of adhesive is usually governed by secondary requirements such as the method and conditions of application and costs. 

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. 

The complexity of the effects that can occur may be judged from a study of the mould release of nitrile-butadiene rubbers (NBR) (see Nitrile rubber adhesives), where a complex interfacial layer including emulsifier and coagulant residues controlled the release properties. The adhesion was affected by a large number of factors, some associated with the mould surface, some with the rubber compound used and some with the base NBR (Fig. 1). 

Nitrile rubber adhesives The main application corresponds to the laminating adhesives. PVC, polyvinyl acetate and other polymeric films can be laminated to several metals... 

In summary, like Nitrile rubber adhesives polychloroprene adhesives use a polar mb-ber and their properties complement one another. 

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. 

Acrylonitrile-butadiene rubber (NBR) (also called nitrile or nitrile butadiene rubber) shows high oils and plasticizer s resistance, excellent heat resistance, good adhesion to metallic substrates, and good compatibility with several compounding ingredients (see Nitrile rubber adhesives). 

Nitrile rubber adhesives J M MARTIN MARTfNEZ Nature and properties... 

Since the stress distribution across the bonded area is not uniform and depends on joint geometry, the failure load of one specimen cannot be used to predict the failure load of another specimen with different joint geometry. The results of a particular shear test pertain only to joints that are exact duplicates. To characterize overlap joints more closely, the ratio of overlap length to adherend thickness l/t can be plotted against shear strength. A set of l/t curves for aluminum bonded with a nitrile-rubber adhesive is shown in Fig. 7.11. 

Figure 7.11 Vt curves at three test temperatures for aluminum joints bonded with nitrile-rubber adhesive. ...

Nitrile rubber adhesives have been used to bond medium-to-high polarity rubbers with polyamide substrates. In an early work, nitrile rubber in solvent was treated with 10-20 parts of phosphoric acid at 50-100°C and subsequently neutralized. In more recent work, acrylic acid, methacrylic acid, dicumyl peroxide and phenol ether were added to a mixture of nitrile and formaldehyde-phenol oligomer to give a mbber-to-polyamide adhesive. 

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