Painting curing

These are supplied as separate components which are mixed together and then applied. The paints cure by chemical reaction —a process which also occurs in the can and so limits the time available for application after mixing. The films are tough and have good chemical resistance. There are three main types of these coatings ... 

In general the SIMPLEX program adjusts variables subject to supplied constraints to minimize a given object function. The object function must be an explicit function of the variables. In the case where paint cure uniformity was optimized, the oven was divided into three zones and the variables were the three oven... 

Figure 5. Paint cure uniformity versus minimum heating rate constant for the low solids paint (Q), high solids 1 (Q), high solids 2 and high solids 3 ( ). The open symbols are for a 17 minute bake and the closed symbols are for a 25 minute bake.

Figure 7. Relative oven throughput versus paint cure window for values of Z -n of 0.25 (Q), 0 2 (C]) 0 15 (A), and 0.10 min-1 ( 7.

A network structure model has been developed from which a parameter that correlates well with physical measures of paint cure can be calculated. This model together with a kinetic model of crosslinking as a function of time and temperature has been used to evaluate the cure response of enamels in automotive assembly bake ovens. It is found that cure quality (as measured by the number and severity of under and overbakes) is good for a conventional low solids enamel. These results are in agreement with physical test results. Use of paints with narrower cure windows is predicted to result in numerous, severe under and over bakes. Optimization studies using SIMPLEX revealed that narrow cure window paints can be acceptably cured only if the bake time is increased or if the minimum heating rate on the car body is increased. 

Typically a full cure will take less than 1 min and can occur with certain adhesives in 15 to 30 s. The partial cure process is usually employed on larger, more difficult to fixture parts. Heat times for sufficient handling strength can be as low as 3 to 10 s. A secondary heat source such as a final paint cure oven will then fully cure the adhesive. 

Editorial, "Paint Curing Saving 27.8 Billion BTUs/Year". Products Finishing, March 1977, pp 77-79. 

Ultimately, sufficient resistance to sag and distortion at on-line paint temperatures to allow on-line painting with the part mounted on the auto. At present shooting for 163 C, but future paint cure temperatures will come down. For initial fenders, automotive is willing to paint off-line. 

Discontinuous Load. Continuous thermal processing of discrete material occurs in operations such as painting, curing, and food processing. The processing of a general, discontinuous load has received some attention [195], If the load of Fig. 18.38 is in discrete form, the analysis is complicated by the presence of moving boundaries and the need for continuous... 

The thin films or coatings can be studied nondestructively, with no sample preparation other than deposition on a polished metal surface if necessary. Specular reflectance has been used to study lubricant films on computer disks, oxide layers on metal surfaces, paint curing as a function of time, and molecules adsorbed on surfaces. For example, the IR absorption spectrum of proteins adsorbed onto a polished gold surface can be studied. This spectrum from an adsorbed layer can form the basis of sensors for compounds that will bind to the proteins and change the spectrum. Use of a polarizer in conjunction with grazing angle analysis can provide information about the orientation of molecules adsorbed onto surfaces. 

Classification material Form of liquid paint Curing... 

Polyisocyanates differ as regards their chemical structure, reactivity, functionality, and isocyanate content. They are the principal curing constituent of two-pack polyurethane paints. Curing agent solutions have an isocyanate content of 5-16 wt%. Solvent-free, liquid curing agents may contain up to 30 wt% isocyanate. 

Curing with Radiation. See also Section 3.7. Radiation curing methods have become increasingly important in the last few years. Paint curing proceeds more rapidly than in circulating air curing since the whole workpiece does not have to be heated. However, only large flat parts can be satisfactorily treated. 

The analysis of coating materials is often employed in the investigation of complaints and substandard batches, or to evaluate competing products. Analysis also plays an important role in the assessment of raw materials, occupational safety and hygiene, and the emission of solvents and decomposition products during paint curing. 

In the drive toward lighter, less-cosdy cars, PP and TPO will be called on for more automotive exterior and interior moldings and panels. Current exterior applications are typically painted, and as mentioned above, less-add-inhibited HALS are being developed to resist addic paint-cured systems used in automotive. But there will be increasing pressure to remove this paintprocessing cost and use pigmented PO compounds that are directly exposed... 

Painted TPO Add paint-curing systems used in automotive can Interact with conventional, basic HALS. Ciba s less-basic Tlnuvln XT 850 NOR HALS is said to allow good paint adhesion in acid-cured systems, allowing partially... 

Features Paints cure by atmospheric moisture protects steel from corrosion in aggressive industrial and coastal atmospheres, high temps, (to 420 C), in presence of chems. 

Ester and ketone solvents, which react with amines, must not be present. The adduct is a polyamine and can therefore be used to crosslink epoxy resins. It has advantages in that it is odourless (simple amines are unpleasant to handle), part-reacted (which speeds up drying) and free from simple amines (which cause exudation). It can be seen now why it is an advantage to age paints cured by simple amines amine adducts are formed during the ageing. 

Drying or curing of the paint film occurs by simple evaporation of the solvent in which the binder is dissolved (carried out at room temperature using air or accelerated by increasing the temperature), or by chemical reactions between the binder components (oxidation, addition, and condensation reactions have been employed in paint curing). 

The volatiles emitted from white amide-cured epoxy powder paints, cured and manufactured by the solution method are listed in Table 9.17. The most abundant compounds detected were isobutyl methyl ketone (4-methylpentan-2-one) and the various isomers of xylene which are typical solvents used in the production of resins. The volatiles characteristic of all three amide-cured epoxy powders studied were an unidentified compound and melamine. 

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