Solubility study of lignin in industrial organic solvents and investigation of electrochemical properties of spray-coated solutions

• Published in: Industrial crops and products 2020-06, Vol.148, p.112310, Article 112310
• Main Authors: Dastpak, Arman, Lourenҫon, Tainise V., Balakshin, Mikhail, Farhan Hashmi, Syed, Lundström, Mari, Wilson, Benjamin P.
• Format: Article
• Language: English
• Subjects: Corrosion protection; Lignin; Organic solvent; Solubility; Sustainable coatings
• ISSN: 0926-6690; 1872-633X
• DOI: 10.1016/j.indcrop.2020.112310

[Display omitted] •Dissolution of kraft and organosolv lignin in industrial solvents was investigated.•Dowanol™ PM and Butyl Carbitol™ demonstrate a high solvating power to dissolve lignin.•Lignin dissolutions were deposited on iron-phosphated steel by spray coating.•Coating anticorrosive characteristics were evaluated by 1 days immersion in 5% NaCl.•Kraft lignin/Dowanol™ PM coatings were found to have strong anticorrosive behavior. In the present study, six organic solvents that are commonly used in the paint industry (1-butanol, 1-methoxy-2-propanol, 2-propanol, butyl acetate, propylene glycol monomethyl ether acetate, and diethylene glycol monobutyl ether) were tested for their ability to dissolve two distinct lignins: an industrial kraft lignin (KL) and a pilot-scale organosolv lignin (OL). Among the solvents investigated, 1-methoxy-2 propanol (Dowanol™ PM, DPM) and diethylene glycol monobutyl ether (Butyl Carbitol™, BC) demonstrated high degrees of solubility (> 98 wt. % at 25 °C) that were comparable to the commonly used lignin solvent, dimethyl sulfoxide (DMSO). Lignin coatings were prepared by spray-coating the new lignin-solvent solutions on iron-phosphated steel, prior to investigation of their subsequent morphological and electrochemical performance characteristics. It was found that KL/DPM coatings demonstrate suitable short-term (1 h, 5% NaCl) anticorrosive characteristics with an increased charge transfer resistance (Rct) compared to the bare steel (1.5 × 105 Ω. cm2cf. 1.9 × 103 Ω. cm2). However, a prolonged (24 h) immersion resulted in a decrease in Rct values (1.1 × 104 Ω. cm2), which may indicate that the lignin coating alone is unable to provide long-term protection under these aggressive conditions.