PHB/V in Extrusion Coating of Paper and Paperboard, Study of Functional Properties, 1998 Polymers, Laminations & Coatings Conference Proceedings

Extrusion coating experiments were carried out in the pilot line at Tampere University of Technology (Institute of Paper Converting). Commercially produced 3-hydroxybutyrate/3-hydroxyvalerate copolymer (PHB/V, BIOPOL TM ) was provided by Monsanto plc, USA. Commercial Finnish paper and paperboard qualities were utilised as substrates. Functional properties, such as adhesion, contact angle and surface energy, curling, heat-sealing and hot tack properties, pinhole-density and water vapour transmission rate were determined. Adhesion between PHB/V and a fibre-based substrate was rather poor regardless of typically used pretreatments (corona and flame). On the other hand, adhesion was perfect (mode of failure was fibre 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 low density polyethylene (PE-LD). PHB/V-coatings exhibited approximately 4-6 times higher water vapour transmission rates (WVTR) than the corresponding PE-LD coatings, but instead, 3-5 times lower values than the poly(lactic acid) (PLLA) coatings. The incorporation of wax or tall oil rosin into PHB/V improved its water vapour barrier. Curling of PHBN was reduced by the addition of wax or tall oil rosin into base-polymer. PHB/V provided good heat-sealing characteristics at rather high sealing temperatures. Pinhole-density was substantially reduced by using higher molecular weight PHB/V and by incorporating plasticiser into PHB/V.