- Wood Coatings
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Van Technologies innovated pigmented UV curable technologies during the 1990’s and today our exclusive ASAC™ Technology has introduced GreenLight Coatings™ UV curable primers that coat a variety of wood species, sands easily and permits smooth, uniform coverage of applied topcoats with excellent adhesion.
Finish quality and beauty is a characteristic of our GreenLight Coatings™ UV curable topcoats. Whether you select one of our self-sealing topcoats, or apply them over our UV curable sealer, GreenLight Coatings™ UV curable topcoats will always provide an exceptional finish appearance with excellent adhesion.
Our exclusive ASAC™ Technology has enabled the development of high performance Waterborne UV Curable Self‐Sealing Topcoats that provide exceptional finish appearance with excellent adhesion. These coatings are available in clear or pigmented options and allow for close to the grain finishing for a very natural appearance.
Our exclusive ASAC™ Technology has enabled the development of a unique waterborne-UV curable adhesion promoting tiecoat for use with sap wood species and exotic woods that contain oils. Although lumber producers do their best to deliver quality wood substrate, there can occur in nature higher or lower content of free sap, pitch, and oils in these types of wood species.
GreenLight Coatings™ UV Curable Products are available in 100% (solids) or hybrid waterborne-UV curable compositions. There are significant differences from conventional coatings that will require an adjustment period to “come up to speed.” Patience and practice will help achieve the full benefit of these high tech wood coatings. The topics below have been determined to be best through actual experience with UV curable coating compositions.
GreenLight Coatings™ UV Curable Products are available in open or closed top drums (55 gallon; agitator heads are optionally available) and pails (5 gallon). It is highly recommended that adequate mixing be done to any product containing flatting, or gloss reduction additives, and fillers before application begins.
GreenLight Coatings™ 100% (solids) UV Curable Products are not susceptible to damage from freezing. The waterborne-UV curable coatings, however, should be protected from freezing. It is recommended to store products at room temperature or a cool holding area. Keep all product away from excessively hot conditions, specifically do not store at temperatures above 110o F. Product temperature will affect viscosity, thereby effecting spray, roll coat, flow coat, etc. characteristics. If product is below 60o F, let the product come to room temperature before applying.
Note: Some product compositions may contain solvent reducers that will require special storage rooms to comply with local and state fire codes.
REVIEW MATERIAL SAFETY DATA SHEET (SDS) BEFORE ANY USE AND POSSIBLE EXPOSURE! UV curable products contain ingredients that can be irritating to eyes, skin, respiratory, and digestive system. Follow all recommendations for personal and environmental protection.
Like all coating materials that contain suspended solids (flatting or gloss reduction additives and/or fillers), there is a chance that the solids may settle to the bottom of the container. Always check the bottom of the container by scraping the bottom with an inspection stick or spatula. Settled solids will appear to be thick and paste‐like when examined. It is recommended to mix all products thoroughly before use with the use of an appropriate mixer. The preferable method of mixing will use a variable speed mixer having a propeller shaped agitator. The propeller or agitator should be approximately one third the diameter of the container and positioned off the bottom of the container by a distance approximately equal to the diameter of the propeller or agitator. When mixing, operate at a RPM sufficient to create a rapid flow of surface fluid material with the formation of a slight vortex. Avoid any aeration of the product that may cause bubbles in the final coated surface. Consistent, smooth, lump free fluid should be seen when the product is fully mixed.
Once material is adequately mixed, an agitator is recommended to maintain suspension of solids for the entire duration of application. Typical agitators have much larger “paddle” like blades that slowly and gently mix or stir the coating. Typical agitator blade diameters are between 1/2 and 1/3 the diameter of the fluid reservoir or container serving the application equipment and are positioned close to the bottom. Often there may be more than one agitation blade assembly, one near the bottom and one approximately 1/2 of the distance to the top of the reservoir or container. With two agitator assemblies, it is essential to watch fluid height and agitator speed to avoid introducing air into the fluid.
All GreenLight Coatings™ products are pre‐filtered for optimum performance, but it is advised to install in‐line filtration between the fluid reservoir or container and the coating applicator system. Standard filters installed in many finishing lines are made of 100 mesh (150u mesh opening) stainless steel screen material. It is highly recommended to perform pre‐mixing and continuous agitation when using any product containing flatting or gloss reduction aids and/or fillers.
Use stainless steel or suitable non‐corrosive material for any wetted parts of the spray line or coating application equipment used.
Fluid Transfer Pumps:
-100% active UV curable coatings, by their nature, are highly susceptible to damage from fluid shear forces. We do not recommend the use of piston pumps, gear pumps, or any other pump that will apply high shear forces to the fluid.
-Waterborne-UV curable coatings are robust and can be pumped using most all industrial pumps available in the market.
Spray tips, tip pressure, and pot pressure will require adjustment to provide optimum performance and may not be the same as that used with other coatings used in the past. For example, the viscosity of available UV coating systems will vary and will, therefore, require different adjustment settings.
For 100% UV curable coatings, the grain raise observed is very similar to that experienced with conventional coatings and does not typically present any problems. Waterborne-UV curable coatings, however, will exhibit grain raise consistent with non-UV curable waterborne coatings. The GreenLight Coatings™ UV primers, sealers, and sealer topcoats will “lock in place” any raised fibers so that during the sanding process, a highly smooth, uniform surface is ready for topcoat application. After topcoat application, no secondary grain raise is seen and a high quality finish results.
Wood moisture content will influence the degree of grain raise seen and, therefore, the potential effort necessary to achieve the quality desired. Maintain a constant storage environment for wood stock to help eliminate any finish quality variations.
Review the material safety data sheet (SDS) and always check with your local sanitary treatment facility and/or waste disposal district! They will evaluate materials for you in their effort to help you properly dispose of waste. Do not discharge any waste to a septic system or storm water drain regardless of how harmless you believe it is! The EPA considers septic disposal as an underground injection and closely regulates discharges. Storm water drainage is also closely regulated. In the dry form, after UV curing, the waste from GreenLight Coatings™ UV curable products is not regulated and may be disposed of as normal solid waste. As a liquid it is quite common to find that GreenLight Coatings™ UV curable product waste material will require hazardous waste handling procedures ‐ ALWAYS CHECK FIRST!
This is a very critical step in finishing with any UV coating system. UV curable coating compositions exhibit high chemical resistance, even to the same un‐cured UV coating composition. Sanding performs two functions with UV coating systems. First, sanding will remove unwanted rough regions for smooth topcoat application. Second, sanding will roughen the surface on a micro scale and increase the surface area for best topcoat adhesion. Take note that, the higher the grit used in pre‐sanding, the better the smoothness of the final finish. It is cautioned, however, that it is possible to sand with too high of a grit media and the surface may not possess enough micro‐texture for adhesion promotion. Grit count higher than 300 should be avoided.
In general, it is advised to pre‐sand up to a minimum of 150 grit and it is preferred to reach 220 grit. Apply stain and sealer, and re‐sand to 220 grit when completely cured through action of UV light. It is recommended to always sand with the wood grain and, if using hand power sanders, to use a random orbit sander.
The application of one topcoat, over a sanded prime coat or seal coat layer, will be remarkably smooth and for many instances it will be sufficient as the final finish. A second application of topcoat, after light fine sanding, will further improve final finish quality.
Automatic flat panel sanders perform remarkably well and it is highly recommended to use a segmented pressure belt sanding process. It is essential to apply even pressure over the entire surface area, leaving no regions untouched. Untouched areas may exhibit fish‐eyes, crawling, and/or repel spots. Automatic sanders may also be too aggressive when not set up properly, sanding entirely through the applied seal coat. This will result in spots or craters where the topcoat absorbs into, and re‐seals exposed wood.
Silicon carbide sanding media is highly recommended due to the high degree of hardness of cured UV curable coatings. This type of sanding media on paper will perform much more efficiently and will also last longer, saving cost on replacement belts and paper.
For lineal mouldings and profile sanding it is recommended to employ the use of two initial brush sanding rolls that are constructed of 180 grit abrasive nylon bristles. These brush rolls should rotate with and then against the direction of the part. These should be followed by two additional Flex‐Trim type 150 grit sanding brushes, the first of which having ⅛” sanding strips and the second having ¼” sanding strips. Again, the brush head rotations are with and then against the direction of the part.
Most often, only a UV curing process is required for 100% UV curable GreenLight Coatings™ products. However, there are certain GreenLight Coatings™ UV curing products, including waterborne-UV curable coatings that contain water and/or reducing solvents that require a preliminary drying and/or flash off process. When it is necessary to evaporate reducing solvents and/or water, it is essential to maintain a drying temperature no higher than 80o C.
UV curable products will react only when exposed to UV light and extreme heat. Avoid any unwanted exposure to stray light or heat as these may cause serious coating quality problems to the UV curable product. Quality problems associated with stray light or excessive heat include:
a.) Gel formation in the liquid with potential to clog in‐line filters and spray gun tips,
b.) Irregular shaped particulates, lumps, slugs, etc. in the surface finish, and
c.) Fluid line plugging.
One commonly encountered phenomenon is the appearance of an irregular expression of gloss and/or the appearance of haze on a surface when curing low sheen UV curable coatings. This is the result of unbalanced cure conditions across the coated surface and can be corrected by lamp position and intensity. A radiometer is essential for troubleshooting and for quality control.
Most cure related problems are associated with under cure or situation where the UV coating does not receive enough UV light energy to cure completely. Under cure will result in soft, easily deformed coating surface, loss of adhesion, and/or sanding difficulties (clogging of sanding media). Excessive or long exposure to UV energy will not pose damage to the UV coating unless the surface temperature increases to the point where substrate discoloration and degradation occurs. When UV curing, it is recommended to use standard medium pressure mercury arc lamps, iron and/or gallium doped medium pressure arc lamps, and/or microwave energized mercury lamps of type “H”, “Q”, “V”, or type “D”. Please contact your technical representative for the specific lamp preference for the GreenLight Coatings™ product to be used. The recommended wattage per inch ratings is 300 to 600 W/in and has proven to be quite effective.
CAUTION: Protect all individuals from exposure to high intensity UV lamps. Safety goggles or eyeglass protection is required that will prevent eye exposure to UV light. Protect skin from possible exposure by wearing appropriate clothing. Follow UV lamp manufacturers’ instructions and precautions.
Since the GreenLight Coatings™ 100% UV curable products will not cure unless exposed to UV light or extreme heat, they will always remain in a liquid state. This makes cleaning quite easy by simply flushing the equipment and spray lines with clean acetone solvent. Under the circumstance that application shutdown time is minimal (3 day or less), a black UV opaque cover or bag should be placed over exposed fluid and over application equipment to prevent premature cure of the UV curable product by stray light. Normal application processes may then resume the next day. Longer shut down periods will require a system flush with acetone solvent.
When using waterborne-UV curable products follow the procedure below for performing a system change over from solvent, or other UV curable compositions, and for general cleaning:
System contains conventional solvent or high solids UV curable coating:
System contains waterborne UV product:
Cured UV product will be extremely difficult to remove. Caustic coating removers will be required using proper safety equipment and care for the surface the cured product is contaminating. Remember‐ SAFETY FIRST when using any cleaning solvent ‐ use appropriate precautions and disposal procedures.