Papers coated with crosslinked natural rubber latex and phosphorylated cellulose microfibrils for industrial packaging applications

In the packaging industry, petroleum-based polymers modify papers' barrier and surface properties. However, coatings of natural or modified biopolymers are an environmentally sustainable alternative. This study aimed to evaluate if biodegradable coatings based on natural rubber latex (NR), natural rubber latex cross-linked (CNR) by the photoinitiator Darocur 1173, cellulose microfibrils (CMFs), and phosphorylated cellulose microfibrils (PCMFs) improve the barrier properties of paperboard. Latex suspensions containing 5 % (m/m) of CMFs or PCMFs (based on latex solid content) were tested. The suspensions were evaluated regarding solid content, pH, and viscosity. The thickness, grammage, scanning electron microscopy (SEM), water vapor transmission rate (WVTR), water vapor permeability (WVP), water absorption capacity (Cobb 120 test), contact angle, wettability, and resistance to oils of coated paperboards were evaluated. The WVP for the NR/PCMFs (46.97 ± 0.74 g.mm/day.m2kPa) and CNR/PCMFs (47.89 ± 0.18 g.mm/day.m2kPa) coatings were 43 % and 42 % and below that of the reference paper. Regarding the contact angle, the coatings were hydrophobic (99.41 ± 1.66°). The wettability of the samples with CMFs or PCMFs was lowest (0.014 ± 0.002° s−1), except for the NR/PCMF treatment (0.103 ± 0.023° s−1). The formulations conferred maximum oil permeation resistance (oil kit 12). Latex crosslinking improved suspension dispersion homogeneity and the PCMFs' miscibility, improving the paperboard's barrier and surface properties. [Display omitted] •Phosphorylation pretreatment reduced energy consumption in the production of CMFs.•The crosslinking of the natural rubber latex was effective.•The penetration of water vapor into card paper was reduced with the application of formulations with PCMFs.•All formulations tested showed maximum oil permeation resistance.•Latex crosslinking improved suspension dispersion homogeneity and improved PCMFs miscibility in card paper.