Synthesis of novel plant oil-based isocyanate-free urethane coatings and study of their anti-corrosion properties

Microwave-Assisted Self-Healable Biovitrimer/rGO Framework for Anticorrosion Applications

Microwave-stimulated smart self-healable polymeric coatings with significant protective technology against corrosion have been developed in this work. Herein, a generous approach is strategized to generate linseed oil-derived epoxy composites embedded with reduced graphene oxide (rGO) as a nanofiller in the shielding network. The composite showed excellent self-healing and shape memory properties when irradiated with microwaves due to the dynamic reversible nature of the disulfide covalent bond exchange mechanism. The network also has improved thermomechanical properties and thermal stability, with a storage modulus of 20.8 GPa and a low activation energy of 79 kJ/mol, indicating a fast disulfide dynamic exchange reaction. The amine functionality in the composite contributes to excellent corrosion protection, with 99.9% protection efficiency, as validated via a Tafel plot. The composite also showed excellent hydrophobicity, with a 131° contact angle. This study provides insights into the engineering and application of smart materials as anticorrosive coatings.

Mild condition lignin modification enabled high-performance anticorrosive polyurethane coating

The diverse active hydroxyl groups of lignin pose challenges in the preparation of lignin-based polyurethane coatings with exceptional long-term anticorrosive properties. Here, the dense and defect-free lignin-based polyurethane coating with a thickness of 25 ± 5 μm was successfully synthesized using a mild hydroxypropyl lignin modification approach, exhibiting outstanding barrier properties (|Z| > 109 Ω cm2) and long-term anti-corrosion performance exceeding 120 d. Under ambient conditions (i.e., 25 °C and atmospheric pressure), propylene oxide was directly blended with the alkali solution of lignin to effectively convert phenolic hydroxyl groups into more reactive aliphatic hydroxyl groups, while also minimizing the significant increase in molecular weight caused by lignin condensation. As a result, the high crosslinking density of lignin polyurethane coatings effectively prevented the penetration of corrosive media and enhanced the long-term corrosion resistance of the coatings. Overall, the results demonstrate that a mild hydroxypropyl modification process is an effective and facile strategy to prepare highly reactive lignin-based polyols, which is crucial for the development of high-performance bio-based polyurethane anticorrosive coatings.

Eco-Friendly and High-Performance Bio-Polyurethane Adhesives from Vegetable Oils: A Review

Current petrochemical-based adhesives adversely affect the environment through substantial volatile organic compound (VOC) emissions during production, contributing to air pollution and climate change. In contrast, vegetable oils extracted from bio-resources provide a compelling alternative owing to their renewability, abundance, and compatibility with adhesive formulation chemistry. This review aimed to critically examine and synthesize the existing scholarly literature on environmentally friendly, sustainable, and high-performance polyurethane adhesives (PUAs) developed from vegetable oils. The use of PUAs derived from vegetable oils promises to provide a long-term replacement while simultaneously maintaining or improving adhesive properties. This quality renders these adhesives appropriate for widespread use in various sectors, including construction, automotive manufacturing, packaging, textile, and footwear industries. This review intended to perform a comprehensive assessment and integration of the existing research, thereby identifying the raw materials, strengths, weaknesses, and gaps in knowledge concerning vegetable oil-based PUAs. In doing so, it responded to these gaps and proposes potential avenues for future research. Therefore, this review accomplishes more than merely evaluating the existing research; it fosters the advancement of greener PUA technologies by identifying areas for improvement and innovation towards more sustainable industrial practices by showcasing vegetable oil-based PUAs as viable, high-performance alternatives to their petroleum-based counterparts.

A review on vegetable oil-based non isocyanate polyurethane: towards a greener and sustainable production route

The transition from conventional polyurethane (PU) to non isocyanate polyurethane (NIPU) is driven mainly by safety concerns, environmental considerations, and sustainability issues associated with the current PU technology. NIPU has emerged as a promising alternative, addressing limitations related to traditional PU production. There has been increasing interest in bio-based NIPU aligning with the aspiration for green materials and processes. One important biomass resource for the development of bio-based NIPU is vegetable oil, an abundant, renewable, and relatively low cost feedstock. As such, this review aims to provide insight into the progression of NIPU derived from vegetable oils. This article highlights the synthetic and green approach to NIPU production, emphasizing the method involving the polyaddition reaction of cyclic carbonates and amines. The review includes case studies on vegetable oil-based NIPU and perspectives on their properties. Further, discussions on the potential applications and commercial importance of PU and NIPU are included. Finally, we offer perspectives on possible research directions and the future prospects of NIPU, contributing to the ongoing evolution of PU technology.

Latest Advancements in the Development of High-Performance Lignin- and Tannin-Based Non-Isocyanate Polyurethane Adhesive for Wood Composites

The depletion of natural resources and increasing environmental apprehension regarding the reduction of harmful isocyanates employed in manufacturing polyurethanes (PUs) have generated significant attention from both industrial and academic sectors. This attention is focused on advancing bio-based non-isocyanate polyurethane (NIPU) resins as viable and sustainable substitutes, possessing satisfactory properties. This review presents a comprehensive analysis of the progress made in developing bio-based NIPU polymers for wood adhesive applications. The main aim of this paper is to conduct a comprehensive analysis of the latest advancements in the production of high-performance bio-based NIPU resins derived from lignin and tannin for wood composites. A comprehensive evaluation was conducted on scholarly publications retrieved from the Scopus database, encompassing the period from January 2010 to April 2023. In NIPU adhesive manufacturing, the exploration of substitute materials for isocyanates is imperative, due to their inherent toxicity, high cost, and limited availability. The process of demethylation and carbonation of lignin and tannin has the potential to produce polyphenolic compounds that possess hydroxyl and carbonyl functional groups. Bio-based NIPUs can be synthesized through the reaction involving diamine molecules. Previous studies have provided evidence indicating that NIPUs derived from lignin and tannin exhibit enhanced mechanical properties, decreased curing temperatures and shortened pressing durations, and are devoid of isocyanates. The characterization of NIPU adhesives based on lignin and tannin was conducted using various analytical techniques, including Fourier-transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), matrix-assisted laser desorption/ionization with time-of-flight (MALDI-TOF) mass spectrometry, and gel permeation chromatography (GPC). The adhesive performance of tannin-based NIPU resins was shown to be superior to that of lignin-based NIPUs. This paper elucidates the potential of lignin and tannin as alternate sources for polyols in the manufacturing of NIPUs, specifically for their application as wood adhesives.

Tailor-Made Bio-Based Non-Isocyanate Polyurethanes (NIPUs)

Non-isocyanate polyurethanes (NIPUs) based on biobased polyamines and polycarbonates are a sustainable alternative to conventional polyurethanes (PU). This article discloses a novel method to control the crosslinking density of fully biobased isocyanate-free polyurethanes, synthesized from triglycerides carbonated previously in scCO₂ and different diamines, such as ethylenediamine (EDA), hexamethylenediamine (HMDA) and Priamine^TM-1075 (derived from a dimerized fatty acid). As capping substances, water or bioalcohols are used in such a way that the crosslinking density can be adjusted to suit the requirements of the intended application. An optimization of the NIPU synthesis procedure is firstly carried out, establishing the polymerization kinetics and proposing optimal conditions set for the synthesis of the NIPUs. Then, the influence of the partial blocking of the active polymerization sites of the carbonated soybean oil (CSBO), using monofunctional amines, on the physical properties of the NIPUS is explored. Finally, the synthesis of fully biobased NIPUs with a targeted crosslinking density is achieved using hybrid NIPUs, employing partially carbonated oil and H₂O or ethanol as blockers to achieve the desired physical properties in a very precise manner.

Sustainable smart anti-corrosion coating materials derived from vegetable oil derivatives: a review

Sustainable development is a critical concern in this fast-paced technological world. Therefore, it is essential to employ renewable resources to move towards sustainable development goals (SDGs). The polyols attained from renewable resources, including lignin, chitosan, vegetable oils, cellulose, etc. and the polymers derived from them have attracted the attention of the majority of researchers, both in academia and industry. The development of bio-based polymers from vegetable oils start emerging with different properties to generate a value-added system. This review will give an impression to readers about how coatings generated from vegetable oils can find a way towards better protective properties against corrosion either by using fillers or by using molecular structure modifications in the system, thus covering a range of vegetable oil-based self-healing polymers and their application in anti-corrosion coatings.

Nonedible Vegetable Oil-Based Polyols in Anticorrosive and Antimicrobial Polyurethane Coatings

This review describes the preparation of nonedible vegetable oil (NEVO)-based polyols and their application in anticorrosive and antimicrobial polyurethane (PU) coatings. PUs are a class of versatile polymers made up of polyols and isocyanates. Renewable vegetable oils are promising resources for the development of ecofriendly polyols and the corresponding PUs. Researchers are interested in NEVOs because they provide an alternative to critical global food issues. The cultivation of plant resources for NEVOs can also be popularized globally by utilizing marginal land or wastelands. Polyols can be prepared from NEVOs following different conversion routes, including esterification, etherification, amidation, ozonolysis, hydrogenation, hydroformylation, thio-ene, acrylation, and epoxidation. These polyols can be incorporated into the PU network for coating applications. Metal surface corrosion and microbial growth are severe problems that cause enormous economic losses annually. These problems can be overcome by NEVO-based PU coatings, incorporating functional ingredients such as corrosion inhibitors and antimicrobial agents. The preferred coatings have great potential in high performance, smart, and functional applications, including in biomedical fields, to cope with emerging threats such as COVID-19.