Barrier properties and heat sealability/failure mechanisms of dispersion‐coated paperboard

Abstract

Plate-like ®llers are often added to improve barrier properties and to prevent blocking of dispersion coatings on paper and board. We have studied the effects of clay addition, neutralizing agent and drying conditions on water vapour permeability, water absorption, oxygen permeability and heat sealability of carboxylated styrene/butyl acrylate dispersion coatings on a pilot scale. The barrier dispersions were applied on a pre-coated side of a three-ply board, using a pre-metering roll coater. Coated strips were sealed under speci®ed conditions of temperature, time and pressure and the sealability was assessed by measuring the peak load necessary to break the joints. The surface composition of the barriercoated board was analysed and the mode of failure was characterized by ESCA. The occurrence of pinholes in the barrier coatings was assessed by both staining tests and ESEM/EDX analysis of the surface topography. The resulting barrier properties were satisfactory as far as resistance to water transport in both liquid and vapour form is concerned. The oxygen permeability was similar to that of similar amorphous polymers. Heat-sealing tests showed that the mode of failure was mainly cohesive in nature, as ®bre tear occurred when sealed strips were separated. Neutralization with sodium hydroxide gave poor adhesion and had a negative effect on the seal strength. Barrier measurements and ESEM/EDX analysis both showed that the pinholes present extended only through the barrier coating.

Biopolymer Coatings for Paper and Paperboard

“…Most composite films studied to date combine one or several lipid compounds with one polysaccharide-based structural matrix [18,29,31]. Several polysaccharide biopolymers have the ability to form films with a relatively high degree of crystallinity and with low permeability to oxygen [3,19,32,33], thus making them interesting for use in packaging applications. The polysaccharide polymers in particular will be highlighted in this review.…”

“…Examples are Lyckeby St€ arkelsen Industrial Starches AB Ò (potato), Roquette Ò (maize, wheat and potato) and National Starch and Chemical Ò (maize, potato). Potato is the major source of starch for use in the paper industry in Europe [32], whereas corn starch is more common in the United States. Starch with different amylose/amylopectin ratios and hydroxypropylated starch have been used in food packaging and for edible films [9,33].…”

“…As a consequence of the high degree of crystallinty ($ 63% [20]), high cohesive energy density and excellent film-forming properties of nanocellulose, this material is believed to have potential in packaging applications where high gas barrier properties are required. Research in the area of oxygen barrier materials from nanocellulose is ongoing [19,32,87] and seems to hold great promise for future applications. MFC has also been suggested to work as a reinforcing component in paper coatings [110][111][112].…”

A new approach to studying sponge cake aroma after storage in treated paper and plastic packaging by direct gas chromatography–olfactometry (D‐GC–O)

“…29 The barrier properties of treated-papers would be lower than those of BOPP because first, BOPP is a dense material, like most plastic films, whereas treated papers would still contain some residual porosity, although they were both impregnated and then coated by substances filling up their pores and were both submitted to a calendering treatment which compressed the cellulose fibres and reduced porosity. [30][31][32] Second, the coating made up of latex polymer contains no crystalline region to act as a barrier for diffusion, such as in polyolefins. 30 This work demonstrates that SPME coupled to D-GC-O is a rapid and sensitive method for comparing the aroma compound barrier properties of various packaging films with flavouring mixtures at concentrations close to the p.p.m.…”

New ways to enhance the functionality of paperboard by surface treatment – a review

“…35 An adhesive failure of the seal in the fi bre layer, rather than a cohesive failure in the coating, is indicative of a suffi ciently strong seal. 30,36 Board coated with thermoplastic polymers can be closed by heat sealing, which involves melting of the polymer by application of heat, followed by joining of the surfaces under pressure. Coating fi lm properties that govern heat sealability are low melting point, low melt viscosity, wide seal temperature range, reasonable hot tack and cohesive strength.…”