Heat-Seal Ability and Fold Cracking Resistance of Kaolin-Filled Styrene-Butadiene-Based Aqueous Dispersions for Paper-Based Packaging

Dispersion coatings are offered as alternative solutions to extrusion coating technology for paper-based packaging. In addition to providing barrier properties, waterborne dispersions may implement the processing and converting properties of coated substrates, which are of extreme interest for an effective transfer to the industry. In this work, styrene-butadiene-based aqueous dispersions were formulated considering different amounts of kaolin as pigment. The authors assessed the heat-seal ability, fold cracking resistance, and blocking tendency, comparing the results against commercial dispersion coating grades. Kaolin content dominated the sealing behavior of experimental formulations, changing the minimum heat-seal temperature from 80 & DEG;C to >140 & DEG;C for 0% and 60% kaolin solid content, respectively. On the contrary, commercial grades were mostly affected by temperature. Additionally, despite the low latex glass temperature (0 & DEG;C), experimental formulations generally showed little, if any, blocking. On the downside, increasing kaolin content eases fold cracking, showing a different magnitude according to fold direction and coat orientation yet achieving a higher moisture barrier compared to commercial grades for both folded and unfolded samples.