Paint film quality

Advantageous for temperature-sensitive workpieces Hardening at room temperature (energy saving) Better paint film quality High resistance to mechanical, chemical, and climatic influences Low content of organic solvents... 

Studies have been conducted on creep compliance tests in which paint films were subjected to tensile loads of 4-7 psi (27.2-47.6 x 10 N/m ) and to 6% ozone for 505 h. A typical result for a high-quality emulsion-base paint is shown in Figure 13-1. Creep compliance is reduced by exposure to 6% ozone. If the effect is linearly related to ozone concentration, we might expect the same reduction in creep compliance at 0.1-ppm ozone in 3 x 10 h, or some 30,(XX) yr. Thus, reduction in creep compliance is not viewed as having a serious ozone contribution. 

Blooming. The formation of a thin film on the surface of a paint film thereby causing the reduction of the luster or veiling its depth of color. This defect occurs mostly in stoving enamels (particularly blacks) in gas ovens. Lacquers also exhibit this defect, especially when used with low-quality thinners under certain ambient conditions. 

Dip coating (or tumble coating) is ideal for small, mass-produced articles requiring single coat paint application. Quality of finish is not as high as spray coating and control of film thickness is difficult. Solvents used tend to be relatively simple systems of either medium or slow-evaporating solvents, the exact choice... 

Table 1 shows results of various treatments aimed at the elimination of the paint film. The paint separation method specified in (a) is as follows. Making use of the difference in specific gravity between the paint film (1.1-1.6 g/cm ) and the TP resin (0.96-0.98 g/cm ), a painted TP bumper is crushed into fine pieces and placed in water in order to sort out material floating up to the surface. This is remelted in an extruder where the paint film is separated by means of a melt filter. This method does not result in adequate paint film separation, yielding a recycled material of poor quality. 

The chemical peeling method is to peel off the paint film by immersing the bumper in a solvent of alkaU, etc. TP resin may degenerate and the peeling may require a long time, depending on the type of the solvent, which means problems in terms of quality or productivity. Even if there is no problem in quality of productivity, the waste fluid treatments or the solvent itself is too expensive for an industrial line. All of these conventional treatments were proved to be unsuitable for the recycling of bumpers. 

Pigment volume concentration - While the weight ratio of pigment to binder roughly denotes the quality characteristics of a paint, the volume concentration of the pigments is a more accepted scientific method of predicting how a paint film will perform. 

It appears that during the drying of paint or varnish films the presence of solvent molecules interferes with the process of cross-linking consequently the films have a heterogeneous structure and films of improved protective quality arise when solvents are eliminated. 

Thixotropic Paint a paint which while free-flowing and easy to manipulate under a brush, sets to a gel within a short time when it is allowed to remain at rest. Because of these qualities a thixotropic paint is less likely to drip from a brush than other types and can be applied in rather thicker films without running or sagging. 

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