Biobased Polyurethane Coatings with High Biomass Content: Tailored Properties by Lignin Selection

Abstract

New biobased polyurethane (PU) coatings with high lignin content were developed and characterized in this work. These materials were based on a α,ω-diisocyanate monomer (1,4-bis­(4-isocyanato-2-methoxyphenoxy)­butane, VA-NCO) obtained from lignin-derived vanillic acid and its further cross-linking reaction with three different nonchemically modified technical lignins obtained from different pulping processes, namely, mild acetone organosolv, kraft, and soda. After determining the optimal VA-NCO/lignin mass ratio for each type of lignin, an in-depth characterization of the obtained PU coatings highlighted their high biomass content, effective cross-linking, improved thermal stability, hydrophobic character, good adhesion performance on different types of substrates, and tunable mechanical response. These properties were found to be well-correlated to the chemical–physical features of the parent lignins used (namely, molecular weight, glass transition temperature, distribution of phenylpropane subunits, and −OH content), thereby suggesting the possibility to predictively tailor the characteristics of such biobased PU coatings by lignin selection. The results of this study demonstrate that the reaction of a lignin-derived biobased diisocyanate with different chemically unmodified technical lignins represents an interesting pathway for the production of thermosetting PU coatings with a high biomass content that can find application as high-performance biobased materials alternative to traditional petroleum-based platforms.

Brief Overview on Bio-Based Adhesives and Sealants

“…Vegetable oils present versatile chemical options for different applications since they host reactive sites, such as ester groups, double bonds, and allylic hydrogens [68,69,70]. On the other hand, the use of vegetable oils as a raw material has many advantages, such as availability, price stability, sustainability, physico-chemical properties, and ecological reasons (e.g., sequestration of carbon dioxide by plants) [21].…”

Tuning Lignin Characteristics by Fractionation: A Versatile Approach Based on Solvent Extraction and Membrane-Assisted Ultrafiltration

“…High-value lignin applications, such as the production of polymers and fine chemicals, typically require strict specifications of the starting material, particularly in terms of the chemical composition and molecular mass distribution. Variations in these characteristics due to different lignin origins and processing/extraction methods can cause significant alterations in the performance of the final product [24]. A critical dependence on lignin properties was found for several high-value applications [25][26][27][28], such as the production of polymers [16], antioxidants [29], aromatic compounds [30], the synthesis of vanillin [31], and the development of high-performance concrete water-reducing agents [32].…”

Bamboo-Based Biofoam Adsorbents for the Adsorption of Cationic Pollutants in Wastewater: Methylene Blue and Cu(II)

“…The broad band at around 3690 cm –1 corresponded to the −OH stretching vibration. 28 − 30 After alkali and bleach treatments, the peaks of acetyl and uronic ester groups in hemicellulose at 1730 cm –1 and the aromatic ring vibration in lignin at 1450 cm –1 were absent from α-cellulose and nanocellulose. 31 , 32 The peak at 1300 cm –1 was assigned to O–H plane bending in cellulose.…”