Coating stiffness

The bonding strength also depends upon coating thickness as shown in Fig. 11. This tendency can be explained qualitatively if we consider the disturbance of the stress near the interface due to application of the coating disturbed portion of stress increases with increase of the coating stiffness, which increases with the coating thickness. This tendency is believed to be predictable theoretically and now we are trying to clarify by use of a commercial FEM cord. 

High density storage (PEN) Sublayer for magnetic coating Stiffness... 

Because coating stiffness affects the stresses that cause delamination, strain rate and temperature can have a significant effect on results with organic coatings. With this restriction, the techniques for adhesion measurement work equally well for organic and inorganic coatings. 

A major advance in force measurement was the development by Tabor, Win-terton and Israelachvili of a surface force apparatus (SFA) involving crossed cylinders coated with molecularly smooth cleaved mica sheets [11, 28]. A current version of an apparatus is shown in Fig. VI-4 from Ref. 29. The separation between surfaces is measured interferometrically to a precision of 0.1 nm the surfaces are driven together with piezoelectric transducers. The combination of a stiff double-cantilever spring with one of a number of measuring leaf springs provides force resolution down to 10 dyn (10 N). Since its development, several groups have used the SFA to measure the retarded and unretarded dispersion forces, electrostatic repulsions in a variety of electrolytes, structural and solvation forces (see below), and numerous studies of polymeric and biological systems. 

Stiffness of the films and sheeting can be measured as the tensile modulus of elasticity. Droop or drape tests may be used, particularly for multilayer products. The stiffness is strongly influenced by thickness (to the third power) and temperature, and is important to the processing of film in printing, coating, or end use appHcations where it affects the "hand" of the product. 

Some cast (unoriented) polypropylene film is produced. Its clarity and heat sealabiUty make it ideal for textile packaging and overwrap. The use of copolymers with ethylene improves low temperature impact, which is the primary problem with unoriented PP film. Orientation improves the clarity and stiffness of polypropylene film, and dramatically increases low temperature impact strength. BOPP film, however, is not readily heat-sealed and so is coextmded or coated with resins with lower melting points than the polypropylene shrinkage temperature. These layers may also provide improved barrier properties. 

The method used to apply and dry a fixative affects the degree of stiffness and hold it imparts to the hairstyle. If appHed and then manipulated with a comb, bmsh, or fingers as the polymer forms its film, the adhesive bonds between the hair are broken, the film coating the hair is broken, and the end result is a soft feel with Htde set retention. If the fixative is allowed to dry undisturbed, then the result is a firmer feel and better hold. 

The constmction of vinyl-coated fabrics varies according to its appHcation. A vinyl-coated fabric used for automobile seat covers is shown in Figure 3 a woven fabric is the substrate. The material is durable but stiff and heavy. Incorporating an expanded foam stmcture into the coating layer reduces the weight (Fig. 4), and replacing the woven substrate fabric with a soft knit fabric improves fiexibihty. 

Air and Oil Filters. Liquid resole resins are used to coat and penetrate the cellulose fibers of filters and separators in order to increase strength and stiffness and protect against attack by the environment. The type of phenoHc to be used depends on both the final property requirements and the papermaking process. 

Amino resins are used by the paper industry in large volume for a variety of apphcations. The resins are divided into two classes according to the mode of appHcation. Resins added to the fiber slurry before the sheet is formed are called wet-end additives and are used to improve wet and dry strength and stiffness. Resins appHed to the surface of formed paper or board, almost invariably together with other additives, are used to improve the water resistance of coatings, the sag resistance in ceiling tiles, and the scuff resistance in cartons and labels. 

Low DS hydroxyethyl starches are used as paper coatings and sizes to improve sheet strength and stiffness. They are also employed as paper-coating color adhesives, and to increase fiber bonding in paper products. Hydroxyethylstarches are also used as textile warp sizes. 

Poly(vinyl acetate) emulsions are used to prime-coat fabrics to improve the adhesion of subsequent coatings or to make them adhere better to plastic film. Plasticized emulsions are appHed, generally by roUer-coating, to the backs of finished mgs and carpets to bind the tufts in place and to impart stiffness and hand. For upholstery fabrics woven from colored yams, PVAc emulsions may be used to bind the tufts of pile fabrics or to prevent sHppage of synthetic yams. 

Fig. 4. The effect of blade loading on the wet-coating thickness in flexible blade coating where ( ) represents a less stiff blade (B) represents a stiffer...

It has been also shown that when a thin polymer film is directly coated onto a substrate with a low modulus ( < 10 MPa), if the contact radius to layer thickness ratio is large (afh> 20), the surface layer will make a negligible contribution to the stiffness of the system and the layered solid system acts as a homogeneous half-space of substrate material while the surface and interfacial properties are governed by those of the layer [32,33]. The extension of the JKR theory to such layered bodies has two important implications. Firstly, hard and opaque materials can be coated on soft and clear substrates which deform more readily by small surface forces. Secondly, viscoelastic materials can be coated on soft elastic substrates, thereby reducing their time-dependent effects. 

Solutions of the two recipes were blended in varying proportions to provide tie coats of continuously varying composition. The patent shows an example of eight plies or layers of graded composition between the rubber and the metal substrate. Because of the high fraction of reactive filler, the material closest to the metal substrate would be the most rigid and polar. The stiffness and polarity... 

In the coating of continuous metal coils, reverse roller coating is often used. In this technique the web is moving counter to the application roller direction, so that the paint is partly wiped off by the moving coil. Shear leads to better flowout. Another type of reverse roller coating is used for the application of stiff paste fillers to chipboard. Application is by forward roller, but this is immediately followed by a reverse roller, which presses the filler into the board and doctors it smooth. 

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