Anticorrosive epoxy coatings from direct epoxidation of bioethanol fractionated lignin

The development of lignin-based anticorrosive epoxy coatings for steel protection is beneficial for both alleviating the fossil resource depletion and value-added utilization of lignin but remains a challenge due to the inherent heterogeneous structure of lignin. Here, we selectively extract the low molecular weight (MW) fraction of a crop residue-derived enzymatic hydrolysis lignin (EHL) through a bioethanol fractionation process and prepare epoxy resin by direct epoxidation of the bioethanol fractionated lignin (BFL). The coatings are then fabricated using 20-100 wt% of BFL-based epoxy resin (LEp) as the commercial epoxy resin substitute. The low MW and high p-hydroxyphenyl content of the BFL offer high solubility and good workability for BFL and LEp during epoxidation and coating production, respectively. Lignin-based coatings with 20-40 wt% LEp exhibit good adhesion property (5B) and superior corrosion resistance, compared to the commercial epoxy coating. Although coating with high LEp concentrations (i.e., 60-100 wt%) resulted in decreased adhesion strength, the coating with 100 wt% LEp still displayed corrosion protection performance comparable to that of the commercial epoxy coating. Overall, this study provides a simple and effective approach to converting lignin to epoxy resins for a wide variety of surface coating applications.

Photo-Curable Lacquer Sap Resin Based on Urushiol-Mimicking, Tyrosine-Containing Additive

Oriental lacquer sap is attracting considerable attention as a renewable and eco-friendly natural resin with high durability, heat resistance, insulation, insect repellency, and antiseptic and antibacterial properties. However, to ensure excellent coating performance, it is necessary to improve the drying/curing process of lacquer sap with a time-consuming drying time at high humidity [relative humidity (RH), 70-90%] and ambient temperature (20-30 °C). Drawing on an understanding of the polymerization mechanism of urushiol, the main component of the lacquer sap consisted of a water-in-oil (W/O) emulsion, and this study presents an eco-friendly additive that mimics the structure-function of urushiol composed of a polar catechol head group and a nonpolar hydrocarbon tail. A photo-curable lacquer sap was thus developed by adding a tyrosine amino acid-based lipid agent (denoted as Y-ADDA), which allows faster and more effective drying/curing at lower humidity while maintaining the nature-derived properties of lacquer sap. Y-ADDA easily coassembles with urushiol in the W/O emulsion droplets, thereby significantly accelerating the formation of a polymer network along with urushiol during water evaporation leading to fast drying/curing under ultraviolet (UV) light irradiation at low humidity (∼50% RH). The UV-cured lacquer sap resins showed higher performance in terms of film processing and physicochemical properties compared with that of the lacquer containing only tyrosine amino acids without aliphatic tail conjugation, N-(9-fluorenylmethoxycarbonyl)-O-tert-butyl-l-tyrosine Fmoc-Tyr(tBu)-OH. Furthermore, the drying and curing times, film morphology, transmittance, hardness, and adhesion strength of the UV-cured lacquer were markedly superior compared to those of shellac, a general eco-friendly fast-drying primer. The study provides useful strategies and insights to promote the industrial application of lacquer sap resins by employing biocompatible nanoagents developed with an understanding of the curing mechanism of natural resins and from the viewpoint of green and sustainable chemistry perspective.

Two-dimensional lamellar polyimide/cardanol-based benzoxazine copper polymer composite coatings with excellent anti-corrosion performance

The economic loss and environmental damage caused by metal corrosion is irreversible. Thus, effective methods, such as coating technologies are used to protect metal surfaces from corrosion. In this work, cardanol-based benzoxazine (CB) was synthesized by a solvent-free method using cardanol, paraformaldehyde and n-octylamine. A cardanol-based benzoxazine copper polymer (CBCP) with good mechanical properties was then prepared by CuCl2 catalysis and can be cured at room temperature. Subsequently, polyimide corrosion inhibitors with a two-dimensional sheet structure (pyromellitic dianhydride polyimide (PDPI) and 1,4,5,8-naphthalene tetracarboxylic dianhydride polyimide (NDPI)) were designed and prepared. Lastly, PDPI or NDPI was mixed with CBCP to obtain two-dimensional lamellar polyimide/cardanol-based benzoxazine copper polymer composite coatings. The Tafel curves and electrochemical impedance spectroscopy (EIS) measurements showed composite coatings with good corrosion resistance in different corrosive media. Compared to CBCP coating, the anticorrosion performance of the composite coatings improved obviously, especially the coating obtained with 0.5 wt% PDPI. It exhibits a high polarization resistance (3.874 × 109 Ω), a high protection efficiency (99.99% and 97.98%) and low corrosion rate (3.376 × 10-6 mm year-1). This work suggested a facile and eco-friendly strategy for preparing bio-based anticorrosive composite coatings from low cost and abundant cardanol and polyimide corrosion inhibitors, which will significantly promote their application in metal anticorrosion.

Preparation of Nanoscale Urushiol/PAN Films to Evaluate Their Acid Resistance and Protection of Functional PVP Films

Different amounts of urushiol were added to a fixed amount of polyacrylonitrile (PAN) to make nanoscale urushiol/PAN films by the electrospinning method. Electrospinning solutions were prepared by using dimethylformamide (DMF) as the solvent. Nanoscale urushiol/PAN films and conductive Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate)(PEDOT:PSS)/polyvinyl pyrrolidone (PVP) films were prepared by electrospinning. In order to prepare an electrospun sandwich nanoscale film, urushiol/PAN films were deposited as both the top and bottom layers and PEDOT:PSS/PVP film as the inner layer. When the PAN to urushiol ratio was 7:5, the fiber diameter ranged between 150 nm and 200 nm. The single-layer urushiol/PAN film could not be etched after being immersed into 60%, 80%, and 100% sulfuric acid (H2SO4) for 30 min, which indicated the improved acid resistance of the PAN film. The urushiol/PAN film was used to fabricate the sandwich nanoscale films. When the sandwich film was immersed into 80% and 100% H2SO4 solutions for 30 min, the structure remained intact, and the conductive PVP film retained its original properties. Thus, the working environment tolerability of the functional PVP film was increased.

In situ synthesis of high-performance 4,4′-diaminodiphenylsulfone modified oleo-alkyd nanocomposite coatings: role of hybrid nanofillers on physico-mechanical, hydrophobic and corrosion protective performance

Tung oil monoglyceride (TMG), 4,4′-diaminodiphenylsulfone modified (DDS-TO-alkyd) polypyrrole enveloped cerium oxide (PPy-PSCeO₂) nanofiller dispersed alkyd nanocomposites (alk-DDS-PPy-PSCeO₂-x) were synthesized.

Neodymium-decorated graphene oxide as a corrosion barrier layer on Ti6Al4V alloy in acidic medium

Ti6Al4V alloy is light weight and is used in construction, oil industries and airbus, automobile, and bio implant materials. The native oxide layers of the alloy are not stable at high temperatures and strong mineral acid environments. The conventional epoxy-based layers are porous and the alloy finally fails in the harsh environment in the long term. Therefore, the carbon-based functional materials are being proposed as coating materials to overcome the alloy degradation. In the present contribution, we have used the neodymium-decorated graphene oxide as the corrosion inhibiting barrier for the Ti6Al4V alloy. As a novelty, we found that the few-layer graphene decorated with neodymium acts as a self-cleaning coating. The Nd-decorated graphene oxide were studied by XRD, TEM, FESEM, FTIR, UV, and Raman spectroscopy. The corrosion inhibition efficiency was studied by electrochemical methods.

Precision synthesis of 3-substituted urushiol analogues and the realization of their urushiol-like performance

Urushiol is a resource-limited natural coating material with diverse applications; however, the synthesis of urushiol analogues and the realization of their urushiol-like performance remain challenging. Herein, four urushiol analogues, namely, 3-((4-alkenoylpiperazin-1-yl)methyl)catechols with the precise 3-substitution pattern on a catechol as that found in urushiol were synthesized by employing the Mannich reaction of catechol with formaldehyde and N-Boc-piperazine as the key step in a two-step route. By using optimization, the advantages of convenience in operation, cost-effectiveness, and scalability could be obtained. The electropolymerization of these analogues on copper was found to be practical due to their higher aerobic stability than urushiol, affording robust coatings with desirable hardness, adhesion strength, hydrophobicity, and thermal stability. Furthermore, the coatings exhibited effective corrosion protection on copper with initial anticorrosion efficiency up to 99.9% and comparatively higher efficiency (more than 97%) after 4 weeks of immersion in 3.5 wt% NaCl solution. The evidence from the electrochemical and infrared spectroscopic characterization data revealed that the electropolymerization process mechanically involved the free radical coupling of phenoxyl radicals to themselves and to the C Created by potrace 1.16, written by Peter Selinger 2001-2019 ]]> C bonds in the side chain, forming a robust crosslinking coating. This work paves a way for the synthesis of high-performance urushiol analogues with potential applications as metal protection materials.

Regioselective Mannich reaction was performed on catechol, yielding 3-substituted urushiol analogues that could be electropolymerized to achieve the desirable urushiol-like performance.

From Waste to Valuable Resource: Lignin as a Sustainable Anti-Corrosion Coating

In this study, a waste of biorefinery—lignin—is investigated as an anticorrosion coating on stainless steel. Corrosion behavior of two lignin types (hardwood beech and softwood spruce) was studied by electrochemical measurements (linear sweep voltammetry, open circuit potential, potentiostatic polarization, cyclic potentiodynamic polarization, and electrochemical impedance measurements) during exposure to simulated body fluid (SBF) or phosphate buffer (PBS). Results from linear sweep voltammetry of lignin-coated samples, in particular, demonstrated a reduction in corrosion current density between 1 and 3 orders of magnitude cf. blank stainless steel. Furthermore, results from cross cut adhesion tests on lignin-coated samples demonstrated that the best possible adhesion (grade 0) of ISO 2409 standard was achieved for the investigated novel coatings. Such findings suggest that lignin materials could transform the field of organic coatings towards more sustainable alternatives by replacing non-renewable polymer coatings.

Effect of Silane on the Active Aging Resistance and Anticorrosive Behaviors of Natural Lacquer

Environmentally friendly and renewable hybrid lacquer coatings with excellent aging resistant and anticorrosion properties were studied. The coatings were prepared using raw lacquer coupled with the silane agent 3-aminopropyltriethoxysilane or N-(2-aminoethyl)-3-aminopropyltrimethoxysilane via an eco-friendly sol-gel preparation process. The physical-mechanical properties, thermal stability, aging resistance, and anticorrosion properties of the as-prepared coatings were analyzed. Additionally, the surface of the coatings before and after an accelerated aging treatment was studied by scanning electron microscopy and X-ray photoelectron spectroscopy. The results revealed that the hybrid lacquer coating A (with a raw lacquer-to-APTES mass ratio of 1.8:1) resulted in films with a significantly enhanced antiaging effect (e.g., six times higher than that of lacquer at a gloss loss rate of 30%). Besides, this film revealed an exceptional anticorrosion performance (with the lowest corrosion current I _corr = 2.476 × 10^-10 A·cm^-2) and a high protection efficiency (99.99 and 94.10%), as demonstrated by its electrochemical characteristics. Furthermore, all films exhibited a good barrier because of their dense structure, which prevents the corrosive medium from penetrating the coating during the salt spray test analysis after 1000 h. And the coating A relatively layered was distributing any significant cancaves, integrity better than all coatings studied, indicating that the based electrolyte was easier to penetrate it after salt spraying 2000 h.

Lignin nanoparticles: synthesis, characterization and corrosion protection performance

Lignin nanoparticles were synthesized in natural polyols for the first time with high yield and were used as anticorrosive nanofillers.