Micron-sized, water-dispersible polyester particles enabling strong, low-temperature sintering welding of PET films

Micron-sized non-crystalline glycol-modified poly(ethylene terephthalate) (PETG) particles dispersed in water is demonstrated as a patternable welding material for low temperature welding of PET films, enabling what is effectively a monomaterial PET with high recycling potential as a replacement for PE/PET multilayer foils for packaging. PETG particles were prepared with stabilizing groups consisting of either poly(ethylene glycol) methyl ether (MPEG), poly(vinyl alcohol) (PVA) or cetylpyridinium chloride (CPC), and the influence of stabilizer chemistry on weld strength was investigated. PVA-stabilized particles allowed welding at lower temperatures (160 °C) with a strength comparable to that of high-temperature-welded PET (>250 °C). The use of MPEG stabilized particles based on semicrystalline poly(caprolactone) (PCL) or poly(lactic acid) (PLA) instead of PETG showed no effects from crystallization and therefore indicates that interfacial chemistry is decisive for achieving high welding strength for these multi-phase systems. Extraction studies combined with LC-MS were used to estimate whether regulatory guidelines could be met when using PVA-stabilized particles for welding. The results indicated that the primary extracts were associated with the PVA stabilizer, which is approved for food contact. • Micron-sized, water-dispersible PETG particles enable low-temperature welding of PET films, supporting monomaterial recyclability. • Surface chemistry of stabilizers, especially PVA, is critical for achieving strong welds, surpassing the influence of crystallinity. • PVA-stabilized PETG particles yield weld strengths comparable to high-temperature welded PET, but at lower temperatures. • Migration and extractables analysis confirm that PVA-stabilized welds meet food-contact safety guidelines. • The approach offers a sustainable alternative to PE/PET multilayer packaging by localizing weld layers and minimizing material mixing.