General Tech Tips for VanUltra UV Curable Coatings 

The VanUltra UV Curable coatings, when used properly, will provide ultimate performance and quality.   To assist you in obtaining the best possible performance, the following tips are offered.

General VanUltra System Comments:

 UV curable coatings are typically high non-volatile (solids) or solvent reduced compositions.  Characteristically, they will behave similar to conventional coating systems.   However, there are significant differences that will require an adjustment period to “come up to speed.”  Patience and practice will help achieve the full benefit of these high tech coatings.  The topics below have been determined to be best through actual experience with UV curable coating compositions.

 Packaging:

 VanUltra UV Curable Products are available in open top drums (55 gallon) 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.

 Shipping and Storage Conditions:

 VanUltra UV Curable Products are not susceptible to damage from freezing.   No special handling is required during the winter shipping season.  It is recommended to store the product 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 effect 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. 

Safety:

 REVIEW MATERIAL SAFETY DATA SHEET (MSDS) 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. 

 Mixing:

 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 product 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. 

Agitation:

 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. 

Filtration:

 All VanUltra 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.

 Application Equipment:

 a.  Use stainless steel or suitable non-corrosive material for any wetted parts of the spray line or coating application equipment used.

 b.  Fluid Transfer Pumps:  By their nature, UV cured coating systems 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.  The following pumping methods are recommended:

i.  Roll Coating and Flow Coating:  Air pressure pots and diaphragm pumps

ii.  HVLP Spray Guns:  Air double diaphragm pumps

iii.  Airless and Air Assisted Airless Spray Guns:  Graco Co. Glutton style pumps

 c. 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 typical spray systems, we recommend the following for start-up:

 i.   HVLP guns are highly recommended for relatively low viscosity UV coatings.  We suggest using a fluid tip and needle size of 0.035” - 0.055” and air pressure of 45 - 60 psi to the gun.  Use a pressure pot of 9 - 12 psi to pressurize fluid.

ii.  Conventional spray equipment will result in greater overspray and a lower transfer efficiency.  When using this type of spray equipment, use a fluid tip and needle size of 0.035” - 0.055” and air pressure of 55 to 75 psi.  Again, a pressure pot of 9 - 12 psi is adequate to pressurize fluid.

iii.  For airless and air assisted airless systems, use a fluid tip and needle size of 0.009” - 0.015”.  For airless spray use pressure of 1000 - 1500 psi and for air assisted use 400 to 750 psi.

 Waste disposal: 

 Review the material safety data sheet (MSDS) 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 VanUltra 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 VanUltra UV curable product waste material will require hazardous waste handling procedures - ALWAYS check first!

 General Application Tips:

 1.  Coating Application:  All of the VanUltra products have been designed to coat uniformly.  Machine oils and other surface contaminants can interfere with coating application, so take care to prevent possible contact with these materials.

 2.  It has been observed, especially in spray lines, that the VanUltra products actually may remove residues of other types of coatings.  During start-up, it may be possible to observe “chunks”, “slugs”, and other particulate deposits on the surface after drying.  These are most likely to originate from residues in the fluid lines or tips from prior coatings used.  It is recommended to flush the system with appropriate cleaning solvents prior to using a VanUltra product.  For optimum performance, a final rinse or flush using acetone solvent is recommended.

 Intercoat Abrading or Sanding for Multiple Coat Applications: 

 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.

 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 either a rotary brush sander or 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.

 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.

 Drying and UV Curing: 

 Most often, only a UV curing process is required for the VanUltra UV curable products.  However, there are certain VanUltra UV curing products that contain reducing solvents and/or water that may require a preliminary drying step.  When it is necessary to evaporated 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.

 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 discoloring and degradation occurs.  When UV curing, it is recommended to use standard medium pressure mercury arc lamps, iron doped medium pressure arc lamps, and/or microwave energized mercury lamps of type “H” or type “D”.  The recommended wattage per inch ratings are 300 to 600 W/in and have 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.

Clean-Up: 

 Since high non-volatile (solid) VanUltra 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 shut down time is minimal (1 day or less), a black UV opaque cover or bag should be placed over exposed fluid and over spray gun tips to prevent premature cure of the UV curable product by stray light.   Normal application process 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:

1.  Flush system with cleaning solvent required and/or acetone until clean.

2.  Flush system with acetone or isopropyl alcohol (IPA) solvent.  NOTE:  These two solvents are solvent and water miscible and will act as an intermediate compatible solvent.

3.  Flush system with water.

4.  Begin introduction of waterborne UV product.

 System contains waterborne UV product:

1. Flush system with water.

2.  Flush system with acetone or isopropyl alcohol (IPA) solvent.  NOTE:  These two solvents are solvent and water miscible and will act as an intermediate compatible solvent.

3.  Allow the acetone or IPA to remain in the system until further use.

a.  To go to further use of waterborne UV product:

i.  Flush system with water

ii.  Begin introduction of waterborne UV product.

b.  To go to the use of conventional solvent or high solids UV curable coating:

i.   Begin introduction of conventional solvent or high solids UV curable coating.

 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.

 Application Tips:

 1.  The VanUltra coatings include epoxy acrylate and urethane acrylate based systems.  Both provide excellent topcoat quality including exceptional abrasion and chemical resistance.

 2.  Apply the coating to the desired wet thickness and check for cure and adhesion.

 4.  If the final coating surface is not uniform, check for surface contaminants on the substrate and any possible contaminants from the application equipment.  Spray hoses must have a minimum of compressor oil and, as discussed above, it has been noted that residues in the fluid lines have been “cleaned” and removed with the use of the VanUltra coatings.

 5.  One coat application may be sufficient for quality results with a sealer pre-sanding to 220 grit.  Two coat applications will result in exceptional surface finish quality.

 Miscellaneous Topics: 

1.  Plugged Fluid Filters:  The most frequent cause is inadequate mixing prior to use.  Over time heavier solids will settle out of suspension and form a thicker, paste-like consistency at the bottom of the container.  Upon pumping and in-line filtration of this thick consistency, concentrated solids are delivered to the filter choking off flow.  Clean the filter with acetone, carefully inspecting for foreign matter and re-install.  Fully mix fluid and agitate prior to pumping.

 2.  Rough Orange Peel Finish:  This is typically due to insufficient intercoat sanding or improper coating application process conditions.   Use silicon carbide media paper.  Monitor wet thickness variation and adjust accordingly.  When roll coating, adjust doctor roll gap and speed relative to applicator roll to eliminate corduroy patterns.

 3.  Bumps:  Smooth raised bumps are usually caused from drips of UV product on to coated surfaces during automatic spraying operations.  Wipe down guns and internal spray booth surfaces and restart. 

 When drips are observed there are typically two sources possible.  One, loose fittings on hoses, air caps, tips, etc.  Tighten all fittings.  Second, excessive overspray.  Wipe down all surface area above the travel path of the work piece.  If excessive dripping continues, inspect air flow in the spray booth or cabinet.   Filters may need replacement, exhaust vents may be partially blocked, blower may not be working properly.

 4.  Very Small Bumps or Rough Surface:  This can be from a number of sources.  Before attempting any corrective action, try to identify the imperfection with the aid of a magnifying glass.

 a.  Airborne Contaminants:  Appearing as particles, usually the same color as the wood being processed.  Check filters and replace if needed.  Clean entire coating application area.  Check if dust collector is full.  Check if vacuum on sander is working properly.  When hand sanding, inform employees to take care on wiping dust or blow off operations.

b.  Clear Specks or Tiny Bumps:  This is likely to be a result of insufficient spray technique.  Be sure fluid is properly mixed.  Be sure filters are not clogging.  Check spray tips for adequate spray pattern and uniformity.  Look for guns that are “spitting” and not adequately atomizing fluid.

 c.  Raised Grain:  Seal coat too thin.  Inadequate sanding of seal coat, check board dimensions when using automatic sanders.

 d.  “Hair like” Particles:  Sanding problem where belt may be traveling too slow.  The wrong type of sanding media may be used, install silicon carbide media.

 7.  Topcoat Shows Dry Spots:  There are three most common causes for this:

 a.  Seal coat is too thin.  Increase seal coat thickness.

b.  Sanding operation is too aggressive, removing seal coat in areas.  Adjust sander to remove less seal coat.

c.  Too light of a topcoat.  Increase topcoat thickness.

 8.  Sanding Lines on Wood:  Usually this is from the sanding belt loading.  Inspect and/or replace sanding belt as needed.  Check with the sanding belt manufacturer to be sure you have the proper grit for the application.

9.  Surface Cracking:   Topcoat is too thick and insufficiently cured through it entire thickness.  Thick layers often exhibit surface cure before depth cure.  This formation of a hard surface over a soft surface will result in surface cracks when deeper regions of the layer begin to cure.  Reduce topcoat applied thickness.