SubscribePolypropylene was always considered to be one of the more difficult substrates to print as PP will always require some kind of treatment in order to make it printable.
The surface of the PP must be oxidized and roughened before printing in order to allow ink or glue adhesion.
3 Treatments were possible:
- Corona treatment
- Plasma treatment
- Flame treatment.
Corona treatment is the most common for rigid PP sheets and became the industry standard.
This treatment increases the surface tension and gives the substrate a shelf life of up to 6 month for screen printing, and 3 month for UV offset. Sometimes printing problems occurred during the treatment period, mainly adhesion and even ink spread.
For this reason Ex p and Ciba, both Swiss companies, have developed a "friendly PP" substrate called Prime - ex. Prime – ex is a PP substrate which is primed in line with Ciba "prime it".
The "prime it" was specially developed by Ciba to ease the printing process on difficult plastic substrates. Prime it is odorless totally transparent and can come into direct contact with food.
Ex p produces the PP which is primed in-line, with Prime it, immediately after the corona treatment.
The Prime-ex improves 4 properties:
- The prime – ex has an extended "shelf life" for UV offset and screen printing - up to 12 months.
- The results of the tape test show greatly improved adhesion when compared to the results on normal PP substrate. This is achieved as Prime it has photo-initiators that create a chemical bond between the ink and the polymer as opposed to a mechanical bond on standard PP substrates.
- The ink spread is more even over the entire sheet and only one pass on black is required to get the depth required.
The glossiness and sharpness of the printed image are better.
Prime-ex has already been tested commercially by many offset printers across Europe and the improvements found for those more difficult jobs. Prime-ex is immediately ready to print, saving both the need for a special run to prime and waiting for the primer to dry.
Why not order a sample pallet of prime-ex today and see the difference in quality for yourself!