Coatings formed by reaction of reactants with the help of radiation energy to give a rigid film. UV curable coatings and Electron beam (EB) curable coatings are the main two type of radiation curable coatings.

Radiation curable coatings

Coatings formed by reaction of reactants with the help of radiation energy to give a rigid film. UV curable coatings and Electron beam (EB) curable coatings are the two main types of radiation curable coatings.

Chemicals that dissolve organic coating binder and participate in the cross-linking reaction because of the functional groups they bear. Therefore, they are not volatile or hazardous to environment.

Refractive index of a substance is the ratio of speed of light in space to speed of light in that substance. It is also defined as the ratio of sinus of the angle between the light coming from space hitting the object surface and normal, to the sinus of the angle between refracted light and normal.

Percentage ratio of water vapour amount in a gas to maximum water vapor amount the gas can contain (saturation amount) at the same temperature. Relative humidity of air is frequently mentioned.

Resol resins are synthesized by reacting phenol compounds with formaldehyde with a phenol/formaldehyde ratio higher than the stoichiometric ratio but lower than the ratio used in novolac type resins. In resol resins part of phenol compounds are methylated.

Name given to slow evaporating solvents added to coating formulations to prevent surface defects such as brush marks, orange peel, pinholing and blushing etc. caused by “fast” evaporation of solvent blends during coating applications.

Brush mark

Fiber streaks can be observed right after the application of the paint by brush. If those streaks do not dissappear during drying process, a coating defect named “brush mark” arises. Brush marks can be overcome by lowering the surface tension or viscosity, or by adding slow solvents to the coating system.

Orange peel

This surface defect can be characterized by bumps and valleys resembling an orange skin texture of substrate.This orange skin texture is generally due to poor levelling and it is more common in spray and roller applications. If the surface tension differs at various points on the surface, the migration of paint can cause orange peel. It should be borne in mind that, high viscosity is another factor hindering the levelling.

Pinholing defect

Solvent vapour and other gas bubbles present in wet paint film, tend to make holes while leaving the film during drying process. Drying results in an increase in viscosity, in turn, makes it impossible for paint film to level this holes out and a paint defect called pinholing defect will occur.

Pinholing limit

When the film thickness of applied paint increases, release of solvent vapour and other gases will be retarded. Since paint film starts to get hardened during this period, the holes formed by solvent vapours and other gases become permanent if the thickness of the film is above a certain limit. The dry film thickness of paint film at which this defect starts to occur is called pinholing limit.

Blushing

A paint defect appearing as whitening on the paint and varnish surfaces when paint application is performed at high relative humidity. It is seen in solventborne coatings. After application, solvent evaporation lowers the substrate temperature causing moisture in the air to condense on the paint film which, in turn causes precipitation of organic binder.

The impact caused by falling of a weighed plunger from a gradually increased height onto the back of metal panel of a cured paint film is called reverse impact strength. 

Paint application method where the applicator rolls run in the opposite direction to the conveyor movement. In this application, better levelling is achieved on the surface because sheer stress exerted on the paint film is higher than in direct rolling application. Reverse roller application method is preferred especially in glossy topcoats. See Also Roller coating applications, Direct roller application

Roller coating applications

Paint application performed by using three parallel rollers named as pick-up, feeding and applicator. Pick-up roller immersed in paint pan, moves around its axis and transfers the paint to the feeding roller which it is in touch with. Feeding roller transfers the paint to the applicator roller in contact with it. Application roller, transfers the coating onto the material to be coated which is moving on a conveyor belt. See Also Direct roller application, Reverse roller application

Direct roller application

Type of roller applications, which are based on coating flat panels with rollers on a moving conveyer. In direct roller applications, rotation direction of “application roll” is the same as the conveyer’s moving direction. Having a lower shear than reverse roller application, direct roller application provides good results in primer and non-glossy top coat applications. See Also Reverse roller application, Roller coating applications

Science of flow and deformation of materials.

Chemorheology

Branch of science that investigates the changes in the rheology of a fluid, having components that undergo a chemical reaction, during the course of the reaction. It is also used to investigate the rheological behaviour of crosslinking organic coatings during the film formation process.

Rheology modifiers

Additives that modify the film behaviour of organic coatings during production, storage and application. These additives impart shear thinning and thixotropic behaviour to wet paint.

Additives that modify the film behaviour of organic coatings during production, storage and application. These additives impart shear thinning and thixotropic behaviour to wet paint.

Paint application performed by using three parallel rollers named as pick-up, feeding and applicator. Pick-up roller immersed in paint pan, moves around its axis and transfers the paint to the feeding roller which it is in touch with. Feeding roller transfers the paint to the applicator roller in contact with it. Application roller, transfers the coating onto the material to be coated which is moving on a conveyor belt. See Also Direct roller application, Reverse roller application

Direct roller application

Type of roller applications, which are based on coating flat panels with rollers on a moving conveyer. In direct roller applications, rotation direction of “application roll” is the same as the conveyer’s moving direction. Having a lower shear than reverse roller application, direct roller application provides good results in primer and non-glossy top coat applications. See Also Reverse roller application, Roller coating applications

Reverse roller application

Paint application method where the applicator rolls run in the opposite direction to the conveyor movement. In this application, better levelling is achieved on the surface because sheer stress exerted on the paint film is higher than in direct rolling application. Reverse roller application method is preferred especially in glossy topcoats. See Also Roller coating applications, Direct roller application

General name of very durable and elastic organic polymers. Natural rubber is the most frequently used type of rubber. Natural and synthetic rubbers are cross-linked through vulcanization so that their strength, elasticity and chemical resistance will improve. Rubbers, especially the vulcanized rubbers are also called as elastomers.

Natural Rubber

Remainder of the juice of rubber tree (Hevea brusiliensis) after evaporation. Rubber, chemically composed of polyisopyrene, crosslinks with sulfur compounds forming a high resistance elastomer. Process of crosslinking with sulfur compounds is called vulcanization, and rubber that undergoes vulcanization is called vulcanized rubber.

Chlorinated rubber

Hard thermoplastic resin that is obtained from reaction of natural rubber with chloride, containing approximately 65% chloride and that is soluble in aromatic solvents. It has superior chemical resistance and water resistance. There are also some commercial products obtained from chlorination of synthetic rubber.

A test performed to determine whether there is a pigment flocculation or flooding in the wet paint. The paint to be tested is applied on a panel. After a short drying time (flash-off) rub-out test is carried out by rubbing the paint film with a finger while it is still damp but already starting to dry. The pigment flocs, which may present in the paint film will be re-dispersed by rubbing and the active pigment surface will increase leading to an increase in color strength of pigments. Therefore, if defects described above exist in paint film, there would be a color difference between the rubbed and unrubbed area.

Passenger car

OICA (The International Organization of Motor Vehicle Manufacturers) defines the passenger cars as: Vehicles used for passenger transportation purposes with at least four wheels and 9 seats -including the driver seat- are defined as “passenger cars”. See Also Motor vehicles

Rust

Water insoluble metal oxides formed by oxidation of metals due to corrosion.

Paste

Viscous dispersions of abrasives in liquid phase that are used to eliminate defects and scratches or chalking, which occur over time on the glossy paints or clearcoats. Pastes are used in the first stage of polishing to smooth the rough surface.

Pigment paste

Paint semi-product which has a higher pigment content and generally a higher viscosity then the finished paint.
 

Paint production using monopigmented pigment pastes

In this paint production approach, a resin with a high compatibility range is selected as main dispersion resin and different pigments are dispersed separately to a certain grain size using this resin. Color matching is performed using this pigment pastes and letdown is done by adding remaining ingredients after a proper calculation. The main advantages of this approach are, better optimization of capacity of production equipment (especially the mills) and storage areas in addition to reduced production times. It is achieved by producing common pigment pastes, which can be used in various product groups owing to the compatible resin used. The drawback of this approach is the difficulties in sensitive color matching because of highly concentrated pigment pastes in addition to the possibility of decrease in color strength, gloss as well as haze and formation of particles due to pigment flocculation during storage.

Rutile is one of the natural forms of titanium oxide (TiO2) with the highest refractive index. When rutile titanium oxide is used with organic resins having a refractive index in between 1.40 and 1.60, white paints with the highest hiding power can be obtained. See Also Anatase

Anatase

Crystalline form of titanium dioxide with a lower refractive index (2,488) compared to that of rutile form (2,609) the other crystalline form. Therefore, considering the refractive index of organic binders are generally between 1,40 and 1,60, hiding power of films with anatase type is much less than that of films with rutile type titanium dioxide.