We use poly vinyl alcohol adhesive for our thin walled paper tubes. We’re looking to add a plasticizer to make the tube a bit pliable. What can be added and how?
pVOH can be softened by adding glycerin or propylene glycol after cooking and cooling. Addition rate is typically 5-10% of the dry pVOH weight in the cook. The tradeoff is set speed. Both glycerin and pg act as humectants (materials which hold onto water, and slow set), which can be detrimental to winding operations. Water -resistance of the finished tubes could be adversely affected as well. Another option is to purchase a plasticized resin emulsion from an adhesive supplier. The level of addition to the pVOH adhesive would be determined by the amount of flexibility required. In addition to providing flexibility, the resin base would improve specific adhesion (thus stronger, deeper bonds). Emulsion increases wet-pound cost of the adhesive mixture, but you will usually be able to apply a thinner film of adhesive with higher emulsion content (more active adhesive solids), which will mitigate the increased cost and help further with flexibility. Emulsion should be added to the pVOH cook after it has cooled below 120°F, and thoroughly blended.
I would recommend adding an (EVA) Ethylene-Vinyl Acetate Co-Polymer to the adhesive. Recommend maybe 15-20% on a wet basis. This should soften the glue line and make the dry film more pliable.