Buying questions
Why does print peel off some nonwoven and not others?
Polypropylene has low surface energy, so ink and adhesive cannot wet it properly. Corona treatment raises that energy, and without it the print looks fine on the roll and fails after packing.
At a glance
Specification at a glance
| Surface | Dyne level | Behaviour |
|---|---|---|
| Untreated PP | 29 to 31 dyn/cm | Ink beads, adhesive peels |
| Corona treated | 38 to 42 dyn/cm | Ink wets and bonds |
| Over treated | Above 46 dyn/cm | Blocking, brittle surface |
| Treated then aged | Falls over weeks | Print within the window |
What treatment does
Corona discharge oxidises the surface, adding polar groups that water based and solvent inks can bond to. It is a surface change measured in micrometres, so it does not alter tensile or hand feel.
The shelf life nobody writes down
Treated web loses dyne level over time, faster in warm storage. A roll treated in June and printed in September can fail. Specify the minimum dyne level at the point of printing, and print within the window the supplier states.
Send the question with your specification
Tell us the product, the weight you run now and the market it sells into. We answer with the grade, the test values and the documents you will need.
Questions
Common questions
Can it be treated on one side only?
Yes, and one-sided treatment is normal when only one face is printed.
How is dyne level checked?
With dyne pens or test inks. The number is the highest ink that does not bead within two seconds.
Does treatment help lamination?
Yes, for adhesive and extrusion lamination both. Untreated PP bonds poorly to most adhesives.