We are facing the bad smell (odour) problem in our metallized OPP film.
What is the reason?
Answer
Without knowing the type of smell, i.e. rubber, polymer, paint, sulphurous, etc it is very hard to suggest what it might be. Below are some thoughts.
One common problem is if you are depositing zinc sulphide to make high refractive index coatings for transparent holograms by evaporation of the zinc sulphide. The zinc sulphide may undergo some dissociation, which releases some sulphur into the system. Humans can detect sulphur at very low levels and so it is common to think that there is a huge problem but usually there is only a very small amount of dissociation that is insignificant to the coating refractive index and stoichiometry.
If you were simply depositing aluminium onto OPP then I would look carefully at the system. Is the system showing signs of excessive backstreaming causing oil to reach the evaporation boats and decomposing? Is the OPP a homopolymer or is it coextruded with another polymer that is a very low melting point polymer that is being damaged by the heat load during deposition? Is there a failure of one of the water-cooling lines causing something on the system to overheat?
Sometimes you can have an idea of where to look because of the type of smell. If the smell is of burning paint then look to things like a failure of the water cooling on items such as the diffusion pumps where the hot oil could be heating the body of the pump and causing the paint to char. If the smell is a polymeric smell then look within the vacuum system and see if any water lines are getting too hot or if the web is showing signs of damage because of heat. Or if the smell is rubbery then again look to the water-cooling pipes getting hot. It depends on t he composition of the cooling water flexible pipes in the vacuum system.
Also check what has changed between the system not smelling and the system now smelling. If the system was serviced then check what was done during the servicing. What was disturbed, was everything put back where it was meant to go was anything difficult to put back? If a flexible pipe was hard to put back and got put back in the wrong position it may now be touching a hot spot in the system and gradually being burnt through and so soon will end in a water leak.
Within these suggestions may be enough information for you to find the problem. If not I would need more information to try to help further.
Make sure that your evaporator boats are not getting wet/damp prior to installing them in the machine. Evaporator boats, when wet, will give off an amonia smell which is produced when moisture makes contact with Boron Nitride.
Posted by: Adrian May | December 03, 2007 at 09:14 AM