Properties film adhesives

Film Adhesion. The adhesion of an inorganic thin film to a surface depends on the deformation and fracture modes associated with the failure (4). The strength of the adhesion depends on the mechanical properties of the substrate surface, fracture toughness of the interfacial material, and the appHed stress. Adhesion failure can occur owiag to mechanical stressing, corrosion, or diffusion of interfacial species away from the interface. The failure can be exacerbated by residual stresses in the film, a low fracture toughness of the interfacial material, or the chemical and thermal environment or species in the substrate, such as gases, that can diffuse to the interface. 

Table 1 contains the metal-to-metal engineering property requirements for Boeing Material Specification (BMS) 5-101, a structural film adhesive for metal to metal and honeycomb sandwich use in areas with normal temperature exposure. The requirements are dominated by shear strength tests. Shear strength is the most critical engineering property for structural adhesives, at least for the simplistic joint analysis that is commonly used for metal-to-metal secondary structure on commercial aircraft. Adhesive Joints are purposefully loaded primarily in shear as opposed to tension or peel modes as adhesives are typically stronger in shear than in Mode I (load normal to the plane of the bond) loading. 

Laswell et al., 1971 Arato, 1974). All were prone to excessive dissolution and only one had adequate strength and film thickness. Their working characteristics were found to be unduly sensitive to changes in temperature and humidity (Simmons, D Anton Hudson, 1968). All were inferior to conventional zinc phosphate cements. No further development of these cements has taken place, nor is it likely that interest in them will be revived. The modem water-activated glass-ionomer cement has filled this niche and has vastly superior properties including adhesion to tooth material. 

These differences in film morphology were also reflected as differences in film formation conditions, film adhesion, and in electrochemical properties. The pyrazoline beads readily formed films from solvents such as benzene. For the phenoxy TTF system, however, only CH2Cl2 was effective in forming films. In general, the TTF cross-linked polymers were found to be less adherent to the metallized substrates than the pyrazoline cross-linked polymers. Electro-chemically, it was found that the pyrazoline films showed complete activity after one potential sweep. The TTF polymer films, on the other hand, required from 5 to 20 cycles to reach full electrochemical activity as evidenced by a constant voltammogram with cycling. Furthermore, it was observed that the TTF polymer films were much less electroactive than the pyrazoline materials as shown by optical densities and total coulombs passed which were several times less for the TTF systems. 

Packaging Paper, cardboard, plastics, films, adhesives Raw materials screening Physical properties, such as crystallinity - polymers Quality control... 

Corrosion can be controlled by Isolation of the metal from the corrosive environment by suppression of the anodic dissolution of metal and by suppression of the corresponding cathodic reaction. Isolation of corrosion prone metals from corrosive environments is probably the most general mechanism of the corrosion protection afforded by paint films, sealers, and similar polymer-based materials. Effective isolation requires that polymeric materials have good barrier properties and remain adherent in the presence of water and the products of metallic corrosion. Barrier properties and adhesion aspects of corrosion control are discussed in detail in subsequent sections. 

Specifications and Standards. Borax stability is an important property in adhesives, paper, and textile applications. Ollier emulsion properties tabulated by manufacturers include tolerance to specific solvents, surface tension, minimum film-forming temperature, dilution stability, freeze-thaw stability, percent soluble polymer, and molecular weight. 

After deposition, the films are cured by heating at a controlled rate in a convection oven, hot plate, or tube furnace to evaporate solvents and reaction products (primarily H20) and to convert the polyamic acid to the polyimide. The final properties and adhesion of polyimide films depend on the curing rate and final curing temperature, which can range from 300 to 450 °C. 

This study consisted of applying coating or films of dressing material on agar plates to determine the applicability of wounded tissue which is moist and very hydrophilic, conditions that usually do not provide good properties for adhesive substrates (i.e., adherent). 

As a result of the latency and excellent properties produced by DICY cured epoxies, DICY is used in many B-staged supported film adhesives. DICY is also probably the leading catalyst used in one-component, elevated-temperature curing epoxy adhesives. 

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. 

Extended exposure of the uncured material to temperatures or conditions outside those recommended by the manufacturer will cause change in physical properties of the uncured material and will likely reduce its resulting cohesive and adhesive strength. The reactions that occur due to ambient storage conditions are described in Chap. 3. Figure 17.5 shows the effect of aging conditions on the tensile shear strength of an epoxy film adhesive. 

The PET substrate was argon ion etched before Ni deposition to enhance film adhesion without altering the properties of the substrate. Values of l were then measured, and x was calculated... 

Mehregany, M., Allen, M. G., and Senturia, S. D., "Use of Micromachined Structures for the Measurement of Mechanical Properties and Adhesion of Thin Films", IEEE 1986 Workshop on Solid-State Sensors, Hilton Head NC, June 1986. 

Lin S-Y, Lee C-J, Lin Y-Y. The effect of plasticizers on compatibility, mechanical properties, and adhesion strength of drug-free Eudragit E films. Pharm Res 1991 8 1137-1143. 

As may be expected, many factors affect polyurethane properties which are important in practical apphcations. For example, films, adhesives, and foamed resins can be obtained by suitable formulation, particularly by variation in the nature of the polyol (72). 

Once the PSiPI has been patterned, thermal tempering converts the crosslinked modified polyamic acid to the SiPI lmlde. The crosslinks are expelled during thermal ring closure. The resulting SiPI film has been shown to be more than adequate for electronic applications and has some properties, particularly adhesion, which are better than commercial polyimides (6). 

The adhesive properties of thin films are a crucial material property, because mi-cromachined structures generally consist of several layers deposited on top of one another. Insufficient adhesion inevitably leads to device failure. Only a few methods for measuring adhesion strength are mentioned in the literature. A widespread qualitative test of film adhesion is the tape test, in which a piece of adhesive tape is pressed on the surface and then pulled off. If the film adhesion is good, no material... 

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