Packaging Freshly Painted Parts

Question:

I have worked with the finishing group for my company for more than 10 years now and today I have a question for you. We apply a medium/high-solids liquid urethane on our snowmobile hoods. We have always shipped our snowmobiles in disposable wooden crates to the dealers from the manufacturing plant but have recently changed to a returnable steel crate (collapsible skeleton crate wrapped in an external heat shrink bag). The snowmobile assembly group discovered some chafing/abrasion issues with the new style of crating, which affected the urethane finish on the snowmobile hoods. The group decided on their own to begin applying strips of low-tack self-adhesive bubble wrap to the areas of the hood that were being exposed to abrasion in the new crates during shipping. They did not consult the finishing group before doing so. The bubble wrap film is leaving an imprint on the painted surface as would be expected. We cure our urethane finish in a convection oven, which ramps up to an average high temp of 150°F and ramps back down to ambient temp and travels a cool down cycle before unloading/handling. We have a harder cured finish right now with the new higher solids product than we have ever had out of the oven but the snow assembly group still wants to pursue a protective contact film of some sort. Do you know of a product that is suitable for our needs? I have advised against any product that will maintain surface contact with this freshly painted surface as I fear we will see a staining/hazed surface impression where residual solvents are trapped at the surface. Any suggestions for me? D. S.

Answer:

I agree with your assessment of the problem to not allow anything to touch freshly coated surfaces. Film hardness is not necessarily the important parameter in marking resistance. We had a marking problem with paint on fractional horsepower motors packed in cardboard cartons at the end of the assembly line. In that case, it was solved by delaying packaging.
This is really a packaging problem rather than a paint problem. The automotive people use a film to cover sensitive painted surfaces of motor vehicles during transit. I am not familiar with these products. Therefore, I suggest you find out what they use.