Corona Treatment of Filled Dual-polymer Dispersion Coatings: Surface Properties and Grease Resistance

Abstract

Dispersion coating layers consisting of hydroxypropylated starch, 0–30 pph of barrier-grade talc and 0–10 pph of styrene-butadiene latex were subjected to both positive and negative direct-current corona treatments utilizing a specially developed dynamic treatment unit. The effects of the surface composition (barrier coating) on the response to the direct current corona treatment were evaluated by measuring contact angles and determining the surface energy. The effects of corona treatment on the properties of the barrier coating were further determined by measuring the contact angle of rapeseed oil and the grease resistance. It was found that the grease resistance of the corona-treated barrier coatings was substantially lower than that of untreated samples, which was ascribed to holes caused by corona discharge strike-through and to chemical changes on the treated surfaces. The corona treatment lowered the surface energy of the coatings, as indicated by an increase in the contact angles of water and rapeseed oil. Changes in the dispersion part of the surface energy were recorded, particularly after positive treatment voltage, whereas a negative discharge led to greater changes in the polar part of the surface energy. X-ray photoelectron spectroscopy (XPS) tests revealed an increase in the proportion of talc at the surface after corona treatment, which indicates a migration caused by the applied electric field. The peak force tapping mode of an atomic force microscope revealed moderate topographical changes in the coatings and a decrease in surface elasticity, supporting the migration of talc particles. In addition, significant changes in the physicochemical properties of the untreated reverse side were observed.

Surface Modification of Polymers: Methods and Applications

“…Corona discharge penetrates partially through the substrate via pores, consequently ionizing the air between the backing roll and substrate. c) Reproduced with permission . Copyright 2016, DEStech Publications.…”

“…At high power, nonoriented PP is found to show permanent tear drop waviness in the form of about 5–10 mm wide strips along the direction of machine due to high temperature causing localized heating. On a dual‐polymer dispersion coating containing styrene‐butadiene latex, the reverse side oxygen/carbon (O/C) ratio changes from 0.35 to 0.38 for negative corona and to 0.45 for positive corona suggesting negative polarity to negate the effect . The overheating of the substrates can be effectively reduced by cooling the treatment roller and distributing the power over larger surface areas …”

Barrier, converting, and tray‐forming properties of paperboard packaging materials coated with waterborne dispersions

“…This might lead to higher fibre recycling yields 2,3 . Indeed, previous studies 4–6 reported how DCs can be recycled, showing lower reject fractions. However, it was only recently that testing methodologies were standardized or developed for a European harmonization 7,8 ; besides, such recycling methodologies are constantly adapting to address issues linked to the new packaging sold on the market.…”

Improved Oil Resistance of Cellulose Packaging Paper by Coating with Natural Polymer Derived Materials

“…The air permeability of the resulting paper changed, the coating surface energy and the content polar content increased, and the oil resistance also improved. Ovaska (Ovaska et al 2017) performed a corona treatment on hydroxypropyl starch coated paper. After a negative corona treatment, the polar content and oil resistance of the coated paper decreased.…”