Atmospheric pressure plasma treatment of amorphous polyethylene terephthalate for enhanced heatsealing properties

Abstract

An atmospheric pressure plasma system has been used to treat amorphous polyethylene terephthalate (APET) to enhance its healseal properties to a polyethylene terephthalate (PET) film. The plasma treated APET sheet material was thermoformed into trays for use in the food packaging industry and heatsealed to a PET film. The heatsealing properties of the resulting package were assessed using the burst test technique. It was found that the plasma treatment significantly enhanced the adhesive properties and an increase in burst pressure from 18 to 35 kPa was observed for plasma treated food trays. The APET surface chemistry was assessed after plasma treatment where it was found that the plasma treatment had affected an increase in oxygen and an addition of nitrogen species to the polymer surface. The surface roughness (R a ) of the plasma treated samples was also observed to increase from 0.4 to 0.9 nm after plasma treatment. IntroductionHeatsealed polymer trays are widely used for packaging food products, particularly meat and fish [1]. In the heat sealing process a polymer top film is applied to the polymer tray under elevated temperature and pressure in order to enclose the food product in an airtight environment [2]. The conventional method for creating a strong bond between a food tray and a top film is to use a co-extruded heatseal layer ( Figure 1).

Effect of BOPET film surface treatments on adhesion performance of biodegradable coatings for packaging applications

“…According to corona treated surface, this behavior can be explained by the presence of more polar functional groups produced by the oxidation occurring because the electrical discharge. These results are also confirmed by the literature data reporting the significant effect that corona treatment have on the polymeric films surface tension [35,36]. Chemical treatment is less effective in increase of surface energy.…”

Plasma Processing for Tailoring the Surface Properties of Polymers

“…Extreme durability of wettability changes on polyolefin surfaces by atmospheric pressure plasma torch 2010 [20] Treatment of PET and PU polymers by atmospheric pressure plasma generated in dielectric barrier discharge in air 2010 [21] Surface modification of polycarbonate by atmospheric-pressure plasma jets 2012 [22] Atmospheric plasma torch treatment of polyethylene/boron composites: effect on thermal stability 2014 [23] Effect of atmospheric pressure plasma treatment on wettability and dryability of synthetic textile fibres 2013 [24] Atmospheric pressure plasma treatment of amorphous polyethylene terephthalate for enhanced heatsealing properties 2012 [25] Effect of surface wettability and topography on the adhesion of osteosarcoma cells on plasma modified polystyrene 2011 [26] to prevent arcing, grounded surfaces cannot be near these field emission points, as a result the discharge is, by nature, non-uniform: plasma density drops off rapidly with increasing distance from the electrode [33]. In a similar mechanism to flame treatments, a corona treatment causes surface oxidation of polymers.…”

“…The basic sealing methodology is the bonding together of two polymer surfaces by bringing them into intimate contact while they are in a partially molten state [70]. Heat-sealed polymer trays are widely used for packaging food products, particularly meat and fish [25]. The advantage of plasmas pre-treating the polymers prior to heat sealing is a reduction in the required sealing temperature to achieve full bond strength [71].…”

Surface Processing Using Cold Atmospheric Pressure Plasmas

“…The use of the PlasmaStreamÔ system for plasma activation of polymers prior to heat-sealing and adhesive bonding has been successfully demonstrated (23,24). The application of the PlasmaTreatÔ source for the plasma activation of polymers (25), adhesive bonding (26,17), and textile polymer treatments (18) has also been reported.…”