A simple approach to produce hydrophobic biobased coatings using methylcellulose and organosolv lignin.

Substituting plastics with circular and sustainable alternatives has increasingly become a priority. Protective coatings, crucial components in numerous industries, are now in demand for biodegradable options to replace their plastic-based counterparts. Being one of nature's most abundant components, lignin remains underutilized, and this study focuses on investigating its potential for the production of biobased coatings. The method used here involved formulating coating suspensions by mixing methylcellulose and organosolv lignin powders and adding water to the mixture. Glass wafers were coated with the formulated suspensions using spin-coating. The morphology of the coated surfaces was assessed using optical and scanning electron microscopy. In addition, the wettability of the surfaces was examined through water contact angle experiments, and a numerical model was introduced to predict the water contact angle evolution over time. The results revealed that the sample coated with a 2.5 wt% lignin suspension exhibited the highest initial contact angle (114°), with a decreasing trend as the lignin fraction increases. Moreover, coatings with 3.5 wt% lignin and above exhibited lower surface coverage due to lignin particle aggregation and surface defects. By approximating the water droplet on the surface as a spherical cap, the introduced numerical model successfully predicted the time-dependent evolution of the water contact angle by showing strong alignment with experimental results. Taken altogether, we have showcased here a method for modifying coating properties-in a practical sense from water-absorbent to splash-proof-using readily available forest-based materials. This advancement is paving the way for sustainable protective packaging, aiming to replace styrofoam in the electronics and food industries.

Electrical Conduction Mechanisms in Ethyl Cellulose Films under DC and AC Electric Fields.

This work reports the dielectric behavior of the biopolymer ethyl cellulose (EC) observed from transient currents experiments under the action of a direct current (DC) electric field (~107 V/m) under vacuum conditions. The viscoelastic response of the EC was evaluated using dynamic mechanical analysis (DMA), observing a mechanical relaxation related to glass transition of around ~402 K. Furthermore, we propose a mathematical framework that describes the transient current in EC using a fractional differential equation, whose solution involves the Mittag-Leffler function. The fractional order, between 0 and 1, is related to the energy dissipation rate and the molecular mobility of the polymer. Subsequently, the conduction mechanisms are considered, on the one hand, the phenomena that occur through the polymer-electrode interface and, on the other hand, those which manifest themselves in the bulk material. Finally, alternating current (AC) conductivity measurements above the glass transition temperature (~402 K) and in a frequency domain from 20 Hz to 2 MHz were carried out, observing electrical conduction described by the segmental movements of the polymeric chains. Its electrical properties also position EC as a potential candidate for electrical, electronics, and mechatronics applications.