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

Abstract

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 °C to >140 °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 °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.

Barrier, converting, and tray‐forming properties of paperboard packaging materials coated with waterborne dispersions

“…In particular, higher kaolin content generally led to increased water absorption. However, in terms of magnitude, such results differ from previous results 22,24 with the same coatings but different substrate, especially for experimental coatings, where higher dry coat grammage led to even worse relative performance.…”

“…Despite similar results achieved on paper substrates 22,24 , the testing conditions involved in this research were harsher because of higher penetration rates caused by higher test temperature (i.e., 60 C instead of 23 C). Overall, DCs achieved properties that were sometimes similar to…”

“…In this work, two commercial aqueous dispersions were investigated. Such dispersions were already part of previous research for singlelayer coated paper packaging 22,24 . Adopting a previous nomenclature, the specific grades studied in this context were:…”

“…Coating preparation followed the procedure described in previous publications 22,24 . PCC Exol SA (Brzeg Dolny, Poland) kindly provided Exolat C40 sodium polyacrylate, used as a dispersant (0.16% dry weight on dry pigment weight).…”

“…Besides a complete barrier properties characterization, the processing of fibre-based substrates might affect coating integrity, hence the final packaging performance [24][25][26][27] . Therefore, the evaluation of processing effects on the barrier properties, and the actual processability of such coatings is of extreme interest.…”