Film adhesives nylon

Glass, nylon, polyester, and cotton fabric or mat are often used as a carrier in tape or film adhesive systems. In addition to being a carrier and a reinforcement, the strands of the fabric offer an internal shim so that the bond line cannot be thinner than the thickness of these strands. Sufficient pressure need only be applied to cause the adhesive to flow so that the shims meet the substrate surfaces to provide a positive stop. Paper, mat, and other carrier materials may also be used for this purpose. 

A significant advantage of tape and film adhesives is the greater toughness that is available compared to other adhesive types. This is primarily due to the ease with which resinous modifiers can be added to the formulation via solvent solution. Thus, hybrid epoxy adhesives such as epoxy-nylon, epoxy-phenolic, etc., are often found in tape or film form. 

Typically tape or film epoxy adhesives are modified with synthetic thermoplastic polymers to improve flexibility in the uncured film and toughness in the cured adhesive. Epoxy resins can also be blended with phenolic resins for higher heat resistance. The most common hybrid systems include epoxy-phenolics, epoxy-nylon, epoxy-nitrile, and epoxy-vinyl hybrids. These hybrid film adhesives are summarized in Table 13.2, and structural properties are shown in Table 13.3. 

Epoxy-nylon film adhesive can be manufactured by solution casting processes. However, a more efficient and environmentally acceptable method is to calender dry blends of powdered nylon with a bquid epoxy resin with accelerators and other modifying resins directly... 

Many film adhesives have a supporting carrier or reinforcement fabric incorporated into the adhesive to improve handling of the film and provide control of bond line thickness. The carriers are usually glass, polyester, or nylon fabrics of knitted, woven, or nonwoven construction. The difficulty with such carriers is that they can provide an effective way of moisture entering the bulk of the adhesive. Moisture can wick along the fiber-adhesive interface. Nylon carriers should especially be reviewed since they have a strong tendency to absorb moisture. 

Structural adhesives that are commonly used for composites are supplied in two basic forms semisolid B-stage film and thixotropic pastes. The film adhesives are cast or extruded onto carrier fabrics or films and partially cured to a semisolid. They can easily be handled, cut, and applied to the joint area. There is no need for mixing, metering, or dispensing of liquid components. In use, these adhesive systems are activated by heat and pressure. The semisolid B-stage film liquefies briefly on application of heat and then cures to an insoluble state. Epoxy, polyimides, epoxy-nylons, epoxy-phenolic, and nitrile-phenolic adhesives are available as B-stage film. 

Common adhesives for sandwich construction include nitrile phenolic films, modified epoxy pastes and films, epoxy-nylon films, polyimide films, and modified urethane liquid... 

General Description Ethylene vinyl alcohol (EVOH) copolymers are an important component of high-barrier, multilayered packaging materials. They can be easily coextruded with nylons, but coextrusion with polyolefins, polyesters, and polycarbonates requires use of adhesives in which the layers are structured as follows base film, adhesive, EVOH, adhesive, and heat sealant. 

Comparison of Adhesion Properties Subjected to Ordinarv-and Over-Vulcanization. For RFL coated nylon 6 and 66 fibers used in tire cords, the reduction of adhesion properties, caused by overvulcanization was small and comparable to that subjected to the ordinary vulcanization. In the case of the armid fabric samples coated with the nylon thin films, adhesion properties such as peel strength and rubber coverage obtained after the overvulcanization were relatively high regardless of the nylon type, though a reduction was observed in some cases, as shown in Figure 7. 

The results for the 120 C-curing epoxy film adhesives are shown in Fig. 9. Marked differences are noted here. The AF-44 nylon-toughened epoxy has very poor durability at any load and adhesion failure predominates. AF-126-2, the first-generation nitr ile-r ubber-f lexibilized epojiy has somewhat better durability and the failure mode is at least partially cohesive. AF-163 and AF-163-2, the second-generation-toughened epoxies, show a substantial... 

In some film adhesives, a cover or knitted fabric is used to support the polymer film. It will also carry a part of the load and will provide improved bond strength by more efficient distribution of the applied forces. Film adhesives are produced in two forms unsupported, or alternatively, supported on a flexible carrier such as glass, cloth, nylon, or paper. The carrier will usually have little effect on adhesive properties. " The adhesive polymer is usually elastomeric, blended with curing agents, fillers, and other ingredients and is usually extruded, calendered, or cast into 0.1-0.4 mm thick unsupported films. This type is called film adhesive. When the mixture... 

Nylon-epoxy film adhesives have the tendency of picking up substantial amounts of water before use. They also tend to lose bond strength rapidly after use on exposure to water or moist air. After 18 months of exposure to 95% RH, conventional nitrile-phenolic adhesive loses only a fraction of its initial strength, going from 21 to 18 MPa in tensile shear. On the other hand, one of the best nylon-epoxy adhesives available degraded from about 34 to 6.8 MPa in just two months under the same test conditions. A considerable effort has been made to solve this moisture problem, but nitrile-epoxy or acetal-toughened epoxy film adhesives are still superior in durability. "" ... 

Tape and film adhesives are terms used loosely and interchangeably for adhesives in sheet form. More correctly, tapes are supported on a web of paper or nonwoven fabric or on an open-weave scrim of cotton or nylon. Snpporting fibers are useful in that they provide a positive stop under bonding pressure. This can be nsed to control bond line thickness and often to help distribute stresses. Films on the other hand, are free of reinforcing fibers and consist only of the adhesive in thin, sheet form. 

Many film adhesives have a supporting scrim, or carrier, incorporated into the adhesive to improve handling of the film and provide control of the bondline thickness. The carriers are usually either nylon or polyester... 

A grey high strength modified epoxy non-tacky film adhesive containing a knitted nylon carrier, and supplied on a release paper backing with polythene interleaving. 

A series of modified epoxy film adhesives curing at 175 C, available both supported on a woven nylon carrier, or unsupported, at areal weights of between 180 and 400g/ml... 

A supported film adhesive curing at 120, available at areal weights of 150 300 g/m, both containing a knitted nylon carrier for peel strength enhancement and.glueline thickness control. 

Carrier - a thin textile material (either woven or non-woven) on which an adhesive is placed to form a film adhesive. Film adhesives are often offered with a choice of carrier type (material, e.g. nylon or glass, depending on the service temperature form - matt or woven). The carrier aids bondline control and acts as a support for the adhesive. 

Film adhesives They resemble hot melts and heat-activated adhesives in the sense that heat is used for activation with a subsequent cure schedule, which may include additional heat application under pressure. They may contain lightweight fabrics, nylon, polyester, glass mats in the form of carrier cloth. Thus, the adhesive thickness may be controlled uniformly. Epoxies, phenolics, nitrile-elastomers, polyamides, PVC, polyvinyl butyl, ethylene-carbolic acid copolymers are available in film form with or without carrier cloths. 

Thermosetting adhesives are also available in film form of various thicknesses. These films may be provided in composite reinforced form as supported by synthetic, woven or nonwoven fabrics of nylon, polyesters, etc. Such films are flexible and their drape ability allows them to conform to a particular joint subsequent to cutting or punching to shapes. Film adhesives are typically supplied containing latent hardeners which are dormant at low temperatures but become active and initiate cure when brought to cure temperature. Refrigeration increases storage life for this type of adhesive. 

Another method using a grit-blast and ultrasonic cleaning, was used by General Electric. In this method, polysulfone parts were prepared for bonding to niobium with AF-42 epoxy-nylon film adhesive (3M Co). The procedure is as follows ... 

The use of coatings applied in the form of tape is also increasing. Polyethylene and polyvinyl chloride films, either self adhesive or else supporting films of butyl adhesive, petrolatum or butyl mastic are in use as materials applied cold at ambient temperatures. Woven glass fibre or nylon bandage is also used to support films of filled asphalt or coal tar and these are softened by propane gas torches and applied to the steel surface hot, cooling to form a thick conforming adherent layer. 

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