Colloidal Lignin Particles and Epoxies for Bio-Based, Durable, and Multiresistant Nanostructured Coatings

Abstract

There is a need for safe and sustainable alternatives in the coating industry. Bio-based coatings are interesting in this perspective. Although various oils and waxes have been used as traditional wood coatings, they often lack sufficient durability. Lignin is an abundant natural polyphenol that can be used to cure epoxies, but its poor water solubility has impeded the use of unmodified lignin in coatings in the past. To address this issue, water-dispersible colloidal lignin particles (CLPs) and an epoxy compound, glycerol diglycidyl ether (GDE), were used to prepare multiprotective bio-based surface coatings. With the GDE/CLP ratios of 0.65 and 0.52 g/g, the cured CLP–GDE films became highly resistant to abrasion and heat. When applied as a coating on wooden substrates, the particulate morphology enabled effective protection against water, stains, and sunlight with very thin layers (less than half the weight of commercial coatings) while retaining the wood’s breathability excellently. Optimal hydrophobicity was reached with a coat weight of 6.9 g(CLP)/m 2 , resulting in water contact angle values of up to 120°. Due to their spherical shape and chemical structure, the CLPs acted as both a hardener and a particulate component in the coating, which removed the need for an underlying binding polymer matrix. Light interferometry measurements showed that while commercial polymeric film-forming coatings smoothened the substrate noticeably, the particulate morphology retained the substrate’s roughness in lightweight coatings, allowing for a high water contact angle. This work presents new strategies for lignin applications in durable particulate coatings and their advantages compared to both currently used synthetic and bio-based coatings.

Optimization of the Warpage of Fused Deposition Modeling Parts Using Finite Element Method

“…It is reported that decreased coating weight generates higher hydrophobicity and surface roughness while thick layers come with fewer empty spaces between the layers, resulting in a reduced hydrophobic effect. In addition, thin layers of filament are most likely to retain the intrinsic unevenness of the surface [34,35]. From Table 5, the predictions of the finite element method were found to be close to the experimental results in some simulations but diverged in others.…”

“…It is reported that decreased coating weight generates higher hydrophobicity and surface roughness while thick layers come with fewer empty spaces between the layers, resulting in a reduced hydrophobic effect. In addition, thin layers of filament are most likely to retain the intrinsic unevenness of the surface [34,35]. Some studies reported on the extensive hydrophobic nature of thin coating related to the higher roughness [36], while other studies [37] suggested decreased surface roughness as well as hydrophobicity due to filled up voids and formation of large aggregate in the case of multiple layers.…”

Interfacial catalysis and lignin nanoparticles for strong fire- and water-resistant composite adhesives

“…Compared to kraft lignin, both EKL and EKL:LNP showed significantly increased thermal stability (Table 2) especially at temperatures above 400 °C, which is unseen in studies where an epoxy with longer chain length is used. 27,57 One reason may be the high density of thermally stable aromatic structures that the short cross-link bridges enable. The low mass loss of EKL: LNP composites upon heating suggested that the material may possess flame resistance, which was hence tested with a Bunsen burner at close range to wooden surface coated with EKL:LNP.…”

Cascade (Dithio)carbonate Ring Opening Reactions for Self‐Blowing Polyhydroxythiourethane Foams

“…[ 29 ] Beyond the foam synthesis, some other studies showed a total conversion of PHU with fast kinetics and catalyst‐free. [ 45–47 ] Additionally, thio‐cyclic carbonate or dithiocarbonate (DTC) have been first synthesized using carbon disulfide instead of CO 2 , in one step synthesis, by Endo et al. [ 48 ] who demonstrated their high reactivity.…”