When printing with a process ink, the processing strength of the substrate needs to be 36 dynes/cm or more.
1, the processing strength of polyolefin film
(1) Films made of PE and PP are inactive on the surface and have poor adhesion to the ink. In order to improve their adhesion with the ink, corona treatment should be performed on the film surface. Give it activity.
(2) Processing intensity of OPP and CPP
1 Wet tension index is usually used to find the surface activity of OPP and CPP films. This wetting tension solution is 30-56 dyne/cm, which is used to detect the surface activity of the film.
2OPP, CPP corona treatment product processing level.
The corona treatment intensity is generally set at about 40 dyne/cm. Although this processing intensity can be exceeded, excessive processing strength brings about some other defects.
OPP: Untreated 30dyne/cm, after treatment 38-42dyne/cm
CPP: Untreated 30dyne/cm, after treatment 38-40dyne/cm
3 Time-dependent change of corona treatment intensity
After long-term inventories of corona-treated products, the treatment intensity will drop by itself. In a hot and humid place, the attenuation of the treatment intensity becomes more pronounced. Store in a well-managed warehouse for 6 months and consider it attenuating around 2-3 dyne/cm.
(3) Lowest processing intensity level
In the past, when the wetting index dropped below 36 dyne/cm, the adhesiveness of the ink deteriorated and printing was impossible. So 36dyne/cm is the lowest limit.
2. Corona treatment intensity of PET and ONY
(1) PET: The corona treatment was not performed when the PET film was first used in the packaging field. Later, it was proved that corona-treated products can ensure the stable adhesion of the ink, so now the PET film for packaging is usually subjected to single-sided corona treatment. The PET film can reach 38-40 dyne/cm without treatment, and the treatment intensity during processing is generally set at about 48 dyne/cm. In particular, corona treatment is necessary when aqueous acrylic agents (polyvinylamines, polybutadienes) are used.
(2) ONY: ONY is more adhesive than PET, but like PET film, the adhesiveness of the ink after corona treatment is relatively stable. General products such as retort pouches that need to withstand harsh conditions are all corona treated, untreated to 38-40 dyne/cm, and treated products set to approximately 40 dyne/cm.