Reply to Hengky on CPP lamination

Dear sir,
We are CPP film manufacturer. One of our customer is having low bonding strength problem between LDPE and CPP on their product. The structure is OPP20/LDPE15/ALU7/LDPE15/CPP20. They used tandem extrusion lamination machine and coat the CPP film with primer offline. The primer used is polyethylenimine and the die temperature is 330 deg C. What can be the source of this problem? Can the CPP film be the source of this problem? Thank you and best regards.

Posted by: Hengky

Eldridge Replies,

Dear Hengky, 

Well the problem can be any of the parts of the process.  Trouble shooting the problem will require some analytical testing to be sure.  If you have been doing this process for some time and everything is the same then either the LDPE lamination resin or the CPP film is a potential source of the problem.  But you have to insure that the primer is made properly, that it was applied at the right coating weight and that the line speed, gap distance and melt temperature for the LDPE are all correct.

In my experience if everything is OK then I suspect the film surface being contaminated or over treated.  This can be determined by checking the surface chemistry of the CPP film.  First check the film by measuring the treatment then the slip concentration in the film.  If the slip concentration is in specification then it is likely that the CPP film was over treated or the wrong CPP film was used.

Comments

[jimmy]

why is it bad to overtreat the film and how we can tell, is it by dynes test.

[Eldridge M Mount III]

Jimmy, when a film is over treated it is over oxidized and generally results in a degraded film surface. This in turn means that the surface of the film is weakened because the molecular weight of the polymer is decreased due to the oxidation. Then when the film is printed, metallized laminated etc. The ink, metal or lamination is then sitting on a weak boundary layer of degraded polymer. This weak boundary layer will cause an adhesion failure of the ink, metal or lamination adhesive.