Enhancement of PLA-PVA Surface Adhesion in Bilayer Assemblies by PLA Aminolisation

Abstract

Poly(lactic acid) (PLA) and poly(vinyl alcohol) (PVA) present complementary barrier properties, and their combination in multilayer assemblies (laminates) could provide materials with more effective barrier capacity for food packaging purposes. However, their low chemical affinity compromises adequate polymer adhesion. Surface free energy modification of thermoprocessed PLA films through treatment with 1,6-hexanediamine was used to enhance adhesion with polar PVA aqueous solutions. Treatments of 1 and 3 min increased the polar component of the solid surface tension, while treatments above 10 min provoked a corrosive effect in the films' structure. Extensibility analyses of PVA solutions loaded with carvacrol (15 wt.%) and different Tween 85 ratios on PLA-activated surfaces allowed the selection of the 1-min aminolysed surface for obtaining PLA-PVA bilayers, by casting PVA solutions on the PLA films. This study revealed that despite aminolisation enhancing the PLA surface affinity for aqueous PVA solutions, casting-obtained bilayers presented limited oxygen barrier effectiveness due to heterogeneous thickness of PVA layer in the laminates.

Epoxidised sesame oil as a biobased coupling agent and plasticiser in polylactic acid/thermoplastic yam starch blends

“…TPS and PLA films showed WVP values of 9.43 g mm (kPa⋅h⋅m 2 ) À1 and 0.36 g mm (kPa⋅h⋅m 2 ) À1 , respectively (Table 2). Similar results were for cassava starch (13.2 g mm (kPa⋅h⋅m 2 ) À1 ) (Valencia-Sullca et al, 2018) and PLA (0.44 g mm (kPa⋅h⋅m 2 ) À1 ) films (Tampau et al, 2020). PLA 75 /TPS 25 films showed higher WVP values than the PLA ones.…”

Biodegradable materials based on poly(vinyl alcohol) (PVA) and poly (lactic acid) (PLA) with antioxidant and antimicrobial activity for food packaging applications

“…The degradation mechanisms of PVA and PLA (Hassouna et al, 2011) generated overlapped patterns, due to the fact that the degradation temperature ranges were very similar. This behaviour was also observed in PVA-PLA bilayers obtained from PVA solutions cast on thermoformed PLA sheets (Tampau, González-Martínez, Vicente, et al, 2020). The multilayers presented a main degradation event at between 180 °C and 390 °C, followed by two subsequent thermal events at above 400 °C; the degradation continued up to 650 °C, from which no residue was observed.…”

“…Therefore, improving the barrier properties against water vapour and oxygen is desirable in the development of useful materials in the food industry. The lamination of two or more materials in a single structure has been used as a successful strategy with which to obtain high barrier capacity materials (Tampau, González-Martínez, Vicente, et al, 2020). In the current study, PLA and PVA sheets, with a high barrier capacity as regards water vapour and oxygen, respectively, were arranged in parallel to form a three-layer film with adequate barrier capacity.…”

Improvement of lamination process of banana pseudo stem/polylactic acid: mechanical-thermal and biodegradation analysis

“…This indicates that the use of unmodi ed PVA may result in secondary bonding between the hydroxyl groups on the vinyl alcohol structure itself, or between PVA and cellulose, etc. [13] while the modi cation of PVA with methacrylate silane where it replaces the hydroxyl groups on the PVA structure, thereby reducing the mole equivalent of the active group hydroxyl groups. The physical crosslink was reduced, then reducing the ratio of elastic in the pulp sheet.…”