Paperboard Substrates Research Articles

Effects of hydrophobic polyhedral oligomeric silsesquioxane coating on water vapour barrier and water resistance properties of paperboard

The substitution of fossil based packaging materials with materials from renewable sources is a topic of current interest. Polyhedral oligomeric silsesquioxanes with fatty acid moieties can have a renewable content of more than 90 % and are therefore called bio-POSS. In this study the bio-POSS octa-(ethyl erucamide) silsesquioxane was coated on a paperboard substrate as a liquid coating. The water resistance and the water vapour barrier properties of the paperboard were improved. Samples on which the bio-POSS coating layer was dried at 80 °C had a slightly higher water resistance and water vapour barrier than samples dried at room temperature. UV treatment of the coating layer had little effect. Solid state 1H-NMR of UV treated coatings showed no reaction of double bonds of bio-POSS in the coating layer. Multiple coating considerably enhanced the water resistance and water vapour barrier properties of the paperboard, due to an increase in the coating thickness and a reduction in number of pores on top coated surfaces.

Enhancing the barrier properties of paper board by a novel lignin coating

In this study, commercially available softwood lignin was esterified with tall oil fatty acid (TOFA) and studied as barrier material in fibre-based packaging material. The lignin was esterified to different degrees of substitution and the chemical analyses of the resulting samples were carried out by FTIR, TMAH thermochemolysis GC–MS, 31P NMR and SEC. After functionalization, the thermoplastic properties of the lignin were enhanced as shown by DSC. The novel thermoplastic lignin samples were applied with a bar coater forming an even coating on the paperboard substrate. The WVTR of the paperboard (840g/m2×24h) could be reduced to 260g/m2×24h with a TOFA lignin ester double coating of 3.9g/m2. Furthermore, a decrease in OTR value was observed for the TOFA lignin ester as well as the TOFA coated paperboard samples. In contrast to the TOFA coating, the modified lignin coatings exhibited a high and stable contact angle (80° for 2min). The coating material did not affect the tensile strength of the paperboard. According to the results, the demonstration of the conversion of lignin into a value added product has been shown. Furthermore, the novel coating material shows promising properties for the development as sustainable barrier material in fibre-based packaging material to replace oil-based barriers.

Printed supercapacitors on paperboard substrate

Printed supercapacitors were prepared to be applied as a part of a hybrid power source in printed electronics applications. The use of non-toxic materials was preferred. The supercapacitor structure consisting of current collectors and activated carbon electrodes was applied on paperboard substrate using silver, graphite and activated carbon inks. Aqueous electrolytes with NaCl salt limit the maximum potential to about 1.2V but are environmentally friendly and provide low equivalent series resistance (ESR).The capacitance values of our printed supercapacitors were typically 0.1–0.5F. With 2cm2 geometrical active area the ESR was below 1Ω which is acceptable for 50mA current output. The efficiency with 50mA charge and discharge current was typically about 90% and with 10mA about 95%.

Atmospheric synthesis of superhydrophobic TiO2 nanoparticle deposits in a single step using Liquid Flame Spray

Titanium dioxide nanoparticles are synthesised in aerosol phase using the Liquid Flame Spray method. The particles are deposited in-situ on paperboard, glass and metal surfaces. According to literature, titanium dioxide is supposed to be hydrophilic. However, hydrophobic behaviour is observed on paperboard substrates but not on metal or glass substrates. Here, the water contact angle behaviour of the deposits is studied along with XRD, XPS, BET and HR-TEM. The deposits are compared with silicon dioxide deposits having, as expected, hydrophilic properties synthesised with the same method. It seems probable that the deposition process combusts some substrate material from the paperboard substrate, which later on condenses on top of the deposit to form a carbonaceous layer causing the hydrophobic behaviour of the TiO2 deposit. The similar layer does not form when depositing the nanoparticles on a metal or glass surfaces. The observations are more than purely aerosol phenomena. However, they are quite essential in nanoparticle deposition from the aerosol phase onto a substrate which is commonly utilised.

Modifications of paper and paperboard surfaces with a nanostructured polymer coating

Organic nanoparticles synthesized by imidization of styrene-maleic anhydride copolymers are deposited as a top-coating onto paper and paperboard substrates from a stable aqueous dispersion with maximum solid content of 35wt.%. The morphology, physical characteristics and chemical surface properties of the coatings are discussed in this paper, using scanning electron microscopy, atomic force microscopy, contact angle measurements and Raman spectroscopy. Due to the high glass transition temperature of the polymer nanoparticles, a unique micro- to nanoscale structured coating is formed that favourably improves the gloss, printing properties (ink-jet printing test and off-set printing test), surface hydrophobicity (maximum water contact angle 140°) and water repellence (reduction of Cobb-values). The interaction of the nanoparticle coatings with the cellulosic paper web results in improvement of the mechanical paper strength and is attributed to hydrogen-bonding between the nanoparticles and the cellulosic fibers.

Effect of corona pre-treatment on the performance of gas barrier layers applied by atomic layer deposition onto polymer-coated paperboard

The effect of corona pre-treatment on the performance of Al 2O 3 and SiO 2 gas barrier layers applied by atomic layer deposition onto polymer-coated paperboards was studied. Both polyethylene and polylactide coated paperboards were corona treated prior to ALD. Corona treatment increased surface energies of the paperboard substrates, and this effect was still observed after several days. Al 2O 3 and SiO 2 films were grown on top of the polymer coatings at temperature of 100 °C using the atomic layer deposition (ALD) technique. For SiO 2 depositions a new precursor, bis(diethylamido) silane, was used. The positive effect of the corona pre-treatment on the barrier properties of the polymer-coated paperboards with the ALD-grown layers was more significant with polyethylene coated paperboard and with thin deposited layers (shorter ALD process). SiO 2 performed similarly to Al 2O 3 with the PE coated board when it comes to the oxygen barrier, while the performance of SiO 2 with the biopolymer-coated board was more moderate. The effect of corona pre-treatment was negligible or even negative with the biopolymer-coated board. The ALD film growth and the effect of corona treatment on different substrates require further investigation.

PHB/V in Extrusion Coating of Paper and Paperboard: Part I: Study of Functional Properties

Extrusion-coating experiments were carried out in the pilot line at Tampere Univesity of Technology (Institute of Paper Converting). Typical paper and paperboard substrates were coated with commercially produced 3-hydroxybutyrate/3-hydroxyvalerate. The resulting physical properties of extrusion-coated composite structures were studied. Adhesion between PHB/V and a fiber-based substrate was rather poor, regardless of typically used pretreatments (corona and flame). On the other hand, adhesion was sufficient (mode of failure was fiber tear as the materials were separated) when the substrate was primed with an acrylic-based primer. The surface energy and polarity of PHB/V were much higher than the respective ones of LDPE. Curling of PHB/V was reduced by the addition of wax or tall oil rosin into the base polymer.