Nitrile rubber phenolic adhesive

When preparing nitrile rubber/phenolic adhesives, the higher the nitrile content of the rubber, the greater its compatibility with phenolic resins. High acrylonitrile content rubbers thus produce adhesives with superior bonding and film properties, although lower acrylonitrile content rubbers will produce adhesives with better low temperature properties. Table 17 illustrates the effect of acrylonitrile content on the tensile properties of nitrile rubber/phenolic resin blends. ... 

Some of the more important applications for nitrile rubber/phenolic adhesives are described below. 

Various literature references discuss the use of nitrile rubber/phenolic adhesives for the bonding of metals.Tanaka discussed a two part liquid adhesive system based on solutions of nitrile rubber dissolved in methyl methacrylate. Aluminum plates were bonded together with the resulting adhesive. Kubo reported that the adhesive composition of Table 19 was good for bonding steel plates. 

Nitrile rubber/phenolic adhesives are also quite useful in adhering rubber to various met-als, " e.g., in the manufacture of rubber covered metal rollers. Huber reported that a nitrile/phenolic adhesive composition provided excellent bonding of rubber to a magnesium roll (Table 20). Other metal bonding applications with nitrile rubber/phenolic adhesives include laminating aluminum foil to paper and then to wood, bonding abrasives to metal, and bonding polyamide to metal. 

Bonding PVC to Steel, Aluminum Foil, Copper, and Polyurethane. Nitrile rubber/ phenolic adhesives have been utilized to bond PVC to a variety of substrates, including steel, " aluminum foil, and copper. Contact adhesives have been reported for plasticized PVC. A heat-resistant adhesive has... 

Applications have been reported for the use of nitrile rubber/phenolic adhesives in the bonding of wood and polyurethane foam to various substrates. Mitsubishi Electric Corp. patented a two-part adhesive composition for Nomex paper (Table 25). 

Automotive trim and clips have been bonded with nitrile rubber/phenolic adhesives and polyamide has been bonded to rubbei and to pavement in a road marking application. Plastic/paper laminates for printing blankets have been prepared. Finally, grit tiles have been bonded to paperboard and other substrates to produce prefabricated tile structures which are stable on application to buildings. 

Sealant Applications. The repair of engine bodies has been reported using a nitrile rubber/ phenolic composition as a sealant. The wing fuel tanks of Cl30 aircraft have also used nitrile rubber/phenolic materials to seal the tanks.Finally, electrolyte leakage in a sheet battery has been prevented using nitrile rubber/ phenolic adhesives. 

Applications of NBR adhesives can be divided in three groups (1) solely nitrile rubber (2) nitrile rubber/phenolic blends (3) nitrile rubber/epoxy blends. 

Nitrile rubber/phenolic resin blends. Blends of equal parts by weight of a nitrile rubber and a phenolic resin in methyl ethyl ketone (at a 20-30 wt% total solids content) is suitable for many adhesive purposes. The more phenolic resin in the formulation, the greater the bond strength and brittleness of the NBR adhesive [67]. Table 10 shows the effect of phenolic resin on nitrile rubber properties. On the other hand, the higher the acrylonitrile content in the rubber. 

General formula for a nitrile rubber-phenolic tape adhesive... 

Fig. 13.7 The TEM image of the nanophase-separated structural epoxy adhesive containing nitrile rubber/phenolic polyurethane liquid rubber blends (cure with dicyandiamide at 180°C).

Fig. 13.8 The T-peel resistance as a function of the crosshead speed for nitrile rubber/phenolic polyurethane liquid rubber blend toughened epoxy (upper curve) and conventional nitrile rubber-toughened epoxy structural adhesives (lower curve).

Suggested adhesives include modified acrylics, epoxies, polyesters, resorcinol-formaldehyde, furane, phenol-formaldehyde, polyvinyl formal-phenolic, polyvinyl butyral, nitrile rubber-phenolic, polyisobutylene rubber, polyurethane rubber, reclaimed rubber, melamine-formaldehyde, epoxy-phenolic, and cyanoacrylates. For maximum adhesion primers should be used. Nitrile-phenoUcs give excellent bonds if cured under pressure at temperatures of 149 C. Lower-strength bonds are obtained with most rubber-based adhesives. 

Nitrile rubber/phenolic resin produces one of the most durable and toughest elastomeric materials developed in the adhesive industry. Further, its resistance to water as to organic solvents is excellent. For these reasons, the nitrile rubber/phenolic resin laminates are used in printed circuit board manufacturing, to bond metallic substrates between themselves (aluminium, steel) and to bond rubber to magnesium. Films of nitrile rubber/phenolic blends have also been used in the aircraft industry for bonding metal-to-metal surfaces in both plain and honeycomb sandwich constructions. 

Most phenolic adhesives are based on resoles, novolacs (or resorcinol-modified novolacs), and phenolic alloys. The last mentioned class includes the important blends of phenolic resins with epoxies, vinyl, polyamide, and nitrile rubber. Phenolic-based adhesives perform well on various types of surfaces the more common substrates are shown in Table III. 

Rubber-to-metal bonding agents are used for the production of vibration-damping members of rubber and metal, developing their adhesion to the metal during vulcanization of the rubber. The same applies to the production of shaft seals. Clutch and brake linings are applied by means of nitrile rubber - phenolic resin adhesives. 

The more phenolic resin employed, the greater the bond strength and the more brittle the adhesive. The increase of bond strength with resin content for nitrile rubber/phenolic resin cements is illustrated by the data in Table 16." The rubber and resin were dissolved separately in methyl isobutyl ketone as 20% total solids solutions and then blended. The adhesive was coated on steel and the cloth was bonded after tack developed. 

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. 

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 is compatible with phenol-formaldehyde resins, resorcinol-formaldehyde resins, vinyl chloride resins, alkyd resins, coumarone-indene resins, chlorinated rubber, epoxies and other resins, forming compositions which can be cured providing excellent adhesives of high strength, high oil resistance and high resilience. On the other hand, NBR adhesives are compatible with polar adherends such as fibres, textiles, paper and wood. Specific formulations of NBR adhesives can be found in [12]. 

In addition to epoxy-phenolic adhesives three-part epoxy-phenolic-nitrile rubber systems are used in metal-metal edge joints and honeycomb constructions [208], These add toughness not available in most EP systems and improve peel strengths. When used on honeycomb, the NR-P is normally applied to the aluminum skin and the EP to the honeycomb for assembly. Service temperature limitations are those imposed by the NR-P part. 

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