The atmospheric plasma pre-treatment process allows plastics manufacturers to prepare plastic surfaces without organic solvents, which makes it more environmentally friendly. With a view to circular economy, Plasmatreat, the plasma pre-treatment specialist is now tackling the treatment of products made from recycled plastic materials. He has just demonstrated how this type of preparation made it possible to obtain quality UV digital printing on recycled PP cups, without using an adhesive agent.
While the surface pre-treatment technology developed by Plasmatreat has been offered to plastics manufacturers for many years, the world leader in the field is now seeking to multiply applications related to the circular economy.
Surface activation by atmospheric plasma: how does it work?
Adhering a coating, glue, filler or paint to a material with low surface tension is inherently very difficult. This is unfortunately the case with plastics, which are mostly non-polar materials and therefore relatively hydrophobic.
To be able to be bonded or to receive a coating, a plastic must therefore undergo a surface preparation step to promote adhesion. To do this, several techniques exist: the use of primers, flame treatment, or plasma activation.
Plasma treatment thus enables manufacturers to avoid the use of primers, products made up of toxic substances and VOCs, the environmental impact of which is well known. When it is carried out under atmospheric conditions, the plasma treatment allows the formation of groups containing oxygen and nitrogen on the surface of the plastics, which increases their surface energy.
This improves both the adhesive strength of glues and coatings, but also the printability of the material. Nevertheless, for the most recalcitrant materials, it sometimes happens that the effect of the plasma is insufficient. Other complementary solutions can then be used, in particular those allowing the formation of surface nanostructures.
Plasma treatment of plastics: increased possibilities
At K 2022, which took place from October 19 to 26, 2022 in Düsseldorf (Germany), Plasmatreat presented new possibilities relating to the application of plasma and its in-house developed processes for the industrial processing of plastics.
According to the press release published by Plasmatreat, the advantages of this process are numerous for manufacturers specializing in the transformation of plastics:
- assembly of initially incompatible materials, such as PMMA and PP;
- replacement of certain technical plastics such as ABS with PP, which is less expensive;
- reproducible process, integrable in production lines and more efficient than chemical techniques;
- certain environmental benefit, by limiting the use of VOCs and making it possible to process materials containing recycled plastics (MPR).
Plasma treatment of materials incorporating MPRs
During this fair, Plasmatreat also presented a new application, developed in cooperation with a manufacturer of injection molding systems.
This involves using Plasmatreat’s Openair-Plasma® pre-treatment to enable consistent, high quality UV digital printing on injection molded recycled PP cups with a crinkle look.
After injection, the recycled cup is subjected to a plasma activation treatment, then printed directly in UV digital printing. Although the inks used are solvent-free and contain no adhesion promoting agent, the result obtained is perfectly satisfactory since the image obtained is of high quality, brilliant, sharp, while being resistant to abrasion and staining. humidity.
In addition to the aesthetic aspect, this type of marking on recycled cups is above all of technical interest. Indeed, the idea is to print on each cup a Data Matrix type code containing information on the material used, the implementation of traceability of these new materials being essential to facilitate their sorting and recycling.
