Polyolefin film for Food Packaging
It is necessary to improve the barrier properties of polyolefin films to use them as materials for food packaging.
The flame treatment allows to cover them also with lacquers very difficult to apply as those water-based
Surface Activation of Polyolefin Substrates, by Flame Treatment
The flame treatment, a valuable alternative to corona treatment, allows to cover them also with lacquers very difficult to apply as those water-based. These are the results of the researchers team of Distam – Department of Food and Microbiologic Sciences and Technologies, Università degli Studi in Milan, who studied the effect of the flame treatment depending on the kind of used gas and of the wrinkles on the polyolefin substrate.
More in details, in the first part of testing the flame treatment was made on polypropylene cast small plates (thickness 1mm) using three different fuels (methane, butane and propane) raw or mixed with air. Afterwards it was decided to consider the influence of the substrate topography using small plates with 3 different levels of wrinkles. The samples under examination were then flame treated keeping the three main process parameters steady (distance from the flame, mixture air/gas, treatment time).
In any case the effect of the treatment was quantified setting the contact angle to the interface solid/liquid/air and defining the surface energy expressed in dyne cm-1.
Analysis of the Flame Treatment Results
The results obtained up to now show how the flame treatment allows to increase drastically the surface energy of materials hard to wet as polypropylene. However the kind of gas to use and the topography of the sample to treat turned to be two main parameters to consider. Other variables linked to the process conditions (and in particular to the combustion phenomenon) should be considered to maximize the treatment. Among these the air/gas relation of the mixture, the treatment time and the flame area used for the treatment would merit further study.
Flame Treatment for Polyolefin Surface
Anyway flame treatment turns to be a valid option to corona treatment for polyolefin surfaces.
There are many reasons: its stability in the course of time, the quick material activation, the absence of mechanical damages (microholes) and of ozone and the fact that the treatment is only on the surface that avoids the back side effect.
E x p e r i m e n t a t i o n
Evaluation of the effect of a flame treatment in function of the type of gas used and the roughness of the substrate polyolefin.
The treatment of a flame allows to drastically increase the energy of Shallow come poorly wettable polypropylene materials. Therefore it arises as an alternative to the CORONA treatment for polyolefin surfaces.
S. Farris, S. Pozzoli, P. Biagioni, S. Mancinelli, A. Angeli, L. Piergiovanni
DiSTAM – Department of Food Science and Technology and Microbiology, University of Milan;
LNESS, Department of Physics, Politecnico di Milano;
Esseci srl – Narni (TR)
PP-fusion plates (70 mm x 70 mm x1mm)
Flame Treater (laboratory prototype)
Gases: methane, propane (LPG), butane
Contact angle and surface energy (OCA 15 + Video-Based Optical Contact Angle Meter, Germany);
Roughness (atomic force microscopy, Alpha-SNOM, WiTEC GmbH, Germany)