Epoxy Coatings Based on Modified Vegetable Oils for Wood Surface Protection against Fungal Degradation

Sustainable biobased flame-retardant epoxy thermoset derived from renewable phytic acid and itaconic-acid for high-performance rubber wood coatings

Developing a green and sustainable bio-based coating is a feasible approach to improve safety and usability of rubber wood. In this study, a phytate-based flame-retardant curing agent, PAIM, was synthesized through neutralization reaction between phytic acid (PA) and imidazole (IM). This curing agent was co-cross-linked with trifunctional biobased epoxy resin (TEIA) derived from itaconic acid. The results showed that the cured PAIM-TEIA composites exhibited outstanding thermal stability, water resistance and solvent resistance. When the PAIM content was 15 wt% (the P content is 1.7 %), the glass transition temperature (Tg) of PAIM-15-TEIA-W reaches 99.3 °C. Subsequently, a series of PAIM-TEIA resin coatings of rubber wood were prepared. The PAIM-15-TEIA-W coating achieved V-0 rating in UL-94 test and displayed a limiting oxygen index (LOI) value of 30.1 %. Compared to pure rubber wood and IM-6-TEIA-W, the peak heat release rate (PHRR) and total heat release (THR) of PAIM-15-TEIA-W decreased by 16.30 % and 28.27 %, and 42.62 % and 10.6 %, respectively. Furthermore, PAIM exhibited gas and condensed flame-retardant action, forming an intumescent char layer while releasing phosphorus radicals and non-flammable gases to protect the wood. This sustainable strategy enhances rubber wood's flame resistance for diverse applications.

Vegetable Oils for Material Applications - Available Biobased Compounds Seeking Their Utilities

Materials derived from natural sources are demanded for future applications due to the combination of factors such as sustainability increase and legislature requirements. The availability and efficient analysis of vegetable oils (triacylglycerides) open an enormous potential for incorporating these compounds into various products to ensure the ecological footprint decreases and to provide advantageous properties to the eventual products, such as flexibility, toughness, or exceptional hydrophobic character. The double bonds located in many vegetable oils are centers for chemical functionalization, such as epoxidization, hydroxylation, or many nucleophile substitutions using acids or anhydrides. Naturally occurring castor oil comprises a reactive vacant hydroxyl group, which can be modified via numerous chemical approaches. This comprehensive Review provides an overall insight toward multiple materials utilities for functionalized glycerides such as additive manufacturing (3D printing), polyurethane materials (including their chemical recycling), coatings, and adhesives. This work provides a complex list of investigated and studied applications throughout the available literature and describes the chemical principles for each selected application.

Self-healing, flame retardant and UV resistant lignin-derived epoxy wood coating with a Schiff base structure

The traditional epoxy resin not only is flammable and non-recyclable and but also heavily dependents on petroleum resources, which cannot meet the requirements of fire prevention and sustainable development. In this study, a vanillin intermediate (VAP) with dynamic imine bond (C=N) was prepared by schiff base reaction between the lignin derivative vanillin (-CHO) and the cage-like polyhedral oligomeric silsesquioxane OA-POSS(-NH2). Then, a biomass-based P-N-Si flame retardant (VAPD) was synthesized by adding 9,10-Dihydro-9-Oxa-10-Phosphaphenanthrene-10-Oxide (DOPO) into the VAP. Subsequently, the VAPD acted as curing agent of epoxy resin to prepare epoxy wood coatings (VAPDs/EP). The results showed that the VAPD-5/EP coating not only exhibited excellent self-healing property and was able to achieve 100 % healing within 35 min, but also presented distinctive UV-shielding performance. In addition, the VAPD-5/EP coating reached V-0 level of UL-94 test and got 29.3 % of limiting oxygen index (LOI). Compared with EP coating, the peak heat release rate (pHRR) decreased by 38 %. Furthermore, the VAPD-5/EP coating reached 6H level of hardness test and 4B level of adhesion test. A simple strategy for preparing self-healing flame retardant epoxy coatings with comprehensive properties for protection of wood materials was proposed in this study.

From Waste Vegetable Oil to a Green Compatibilizer for HDPE/PA6 Blends

When properly compatibilized, the blending of polyethylene (PE) and polyamide (PA) leads to materials that combine low prices, suitable processability, impact resistance, and attractive mechanical properties. Moreover, the possibility of using these polymers without prior separation may be a suitable opportunity for their recycling. In this work, the use of an epoxidized waste vegetable oil (EWVO) was investigated as a green compatibilizer precursor (CP) for the reactive blending of a high-density PE (HDPE) with a polyamide-6 (PA6). EWVO was synthesized from waste vegetable cooking oil (WVO) using ion-exchange resin (Amberlite) as a heterogeneous catalyst. HDPE/PA6 blends were produced with different weight ratios (25/75, 75/25, 85/15) and amounts of EWVO (1, 2, 5 phr). Samples with WVO or a commercial fossil-based CP were also prepared for comparison. All the blends were characterized by scanning electron microscopy (SEM), differential scanning calorimetry (DSC), rheology, and mechanical tests. In the case of HDPE/PA6 75/25 and 85/15 blends, the addition of EWVO at 2 phr showed a satisfactory compatibilizing effect, thus yielding a material with improved mechanical properties with respect to the blend without compatibilizer. On the contrary, the HDPE/PA6 25/75 ratio yielded a material with a high degree of crosslinking that could not be further processed or characterized. In conclusion, the results showed that EWVO had a suitable compatibilizing effect in HDPE/PA6 blends with high HDPE content, while it resulted in unsuitable for blends with high content of PA6.

Benchmark Study of Epoxy Coatings with Selection of Bio-Based Phenalkamine versus Fossil-Based Amine Crosslinkers

The phenalkamines (PK) derived from cardanol oil can be used as a bio-based crosslinker for epoxy coatings as an alternative for traditional fossil amines (FA). First, the reaction kinetics of an epoxy resin with four PK and FA crosslinkers are compared by differential scanning calorimetry, illustrating a fast reaction rate and higher conversion of PK at room temperature in parallel with a moderate exothermal reaction. Second, the performance of coatings with various concentrations of PK and PK/FA ratios indicates good mixing compatibility between crosslinkers resulting in higher hardness, scratch resistance, hydrophobicity, and abrasive wear resistance of coatings with PK. The superior performance is confirmed over a broad range of resin/crosslinker ratios, facilitating the processing with viscosity profiles depending on the PK type. Although fossil- and bio-based crosslinkers have different chemical structures, the unique linear relationships between intrinsic mechanical properties (i.e., ductility and impact resistance) and coating performance indicate that the degree of crosslinking is a primary parameter controlling coating performance, where PK simultaneously provides high hardness and ductility. In conclusion, the optimization of the processing range for bio-based PK as a crosslinker for epoxy coatings delivers suitable processing conditions and superior mechanical performance compared to traditional amine crosslinkers.

Activation of Vegetable Oils by Reaction with Maleic Anhydride as a Renewable Source in Chemical Processes: New Experimental and Computational NMR Evidence

Vegetable oils are bio-based and sustainable starting materials that can be used to develop chemicals for industrial processes. In this study, the functionalization of three vegetable oils (grape, hemp, and linseed) with maleic anhydride was carried out either by conventional heating or microwave activation to obtain products that, after further reactions, can enhance the water dispersion of oils for industrial applications. To identify the most abundant derivatives formed, trans-3-octene, methyl oleate, and ethyl linoleate were reacted as reference systems. A detailed NMR study, supported by computational evidence, allowed for the identification of the species formed in the reaction of trans-3-octene with maleic anhydride. The signals in the 1H NMR spectra of the alkenyl succinic anhydride (ASA) moieties bound to the organic chains were clearly identified. The reactions achieved by conventional heating were carried out for 5 h at 200 °C, resulting in similar or lower amounts of ASA units/g of oil with respect to the reactions performed by microwave activation, which, however, induced a higher viscosity of the samples.

Effect of Number of Impregnations of Microberlinla sp with Microcapsule Emulsion on the Performance of Self-Repairing Coatings on Wood Surfaces

Embedding melamine-formaldehyde (MF) resin-coated shellac microcapsules in waterborne coatings can extend the service longevity of waterborne coatings on a wood surface to a certain extent. Due to the content limitation of self-repairing microcapsules in waterborne coatings, the effective self-healing performance time is short. With the aim of improving the self-repairing properties of self-repairing coatings on the surface of a Microberlinla sp substrate, a more effective self-healing mechanism was achieved by impregnating the ebony wood substrate several times with an MF resin-coated transparent shellac-rosin microcapsule emulsion. After the impregnation of the ebony boards with microcapsules, a waterborne acrylic resin coating containing 3.0 wt.% transparent shellac microcapsules was applied to the surface of the wood boards. The influence of the number impregnations on the surface coating’s physical properties, chemical properties, and self-repairing properties was explored. The results showed that the hardness of the surface coating on the ebony boards changed little under different numbers of impregnations. With the increasing number of impregnations, the surface coatings’ adhesion and impact strength slowly increased, the chromatic difference value was increased, and the roughness first increased and then decreased. Impregnating ebony boards with the microcapsule emulsion contributes to enhancing the aging resistance and repair performance of surface coatings on the ebony boards. When the number of impregnations was eight, the width change rate of cracks on surface self-healing coatings was 28.4%, which suggested the best repair performance among all samples. By impregnating the wood substrate with the self-healing microcapsule emulsion, the effect of the interaction between microcapsules and wood on the self-repairing properties of the surface coating was studied, contributing to the theory for further improving the self-repairing properties of waterborne coatings on wood surfaces and promoting the application and development of self-healing microcapsules.

The Effect of Different Vegetable Oils on Cedar Wood Surface Energy: Theoretical and Experimental Fungal Adhesion

Despite having been used for ages to preserve wood against several effects (biological attack and moisture effects) that cause its degradation, the effect of vegetable oils on the cedar wood physicochemical properties is poorly known. Thus, in this study, the hydrophobicity, electron-acceptor (γ⁺), and electron-donor (γ⁻) properties of cedar wood before and after treatment with vegetable oils have been determined using contact angle measurement. The cedar wood has kept its hydrophobic character after treatment with the different vegetable oils. It has become more hydrophobic quantitatively with values of surface energy ranged from −25.84 to −43.45 mJ/m² and more electron donors compared to the untreated sample. Moreover, the adhesion of four fungal strains (Penicillium commune (PDLd”), Thielavia hyalocarpa, Penicillium commune (PDLd10), and Aspergillus niger) on untreated and treated cedar wood was examined theoretically and experimentally. For untreated wood, the experimental adhesion showed a positive relationship with the results obtained by the extended Derjaguin–Landau–Verwey–Overbeek (XDLVO) approach which found that all fungal strains could adhere strongly to the cedar wood material. In contrast, this relationship was not always positive after treatment. The Environmental Scanning Electron Microscopy (ESEM) has shown that P. commune (PDLd10) and A. niger were found unable to adhere to the wood surface after treatment with sunflower and rapeseed oils. In addition, the results showed that the four fungal strains' adhesion was decreased with olive and linseed oils treatment except that of P. commune (PDLd10) treated with linseed oil.

Trends in Chemical Wood Surface Improvements and Modifications: A Review of the Last Five Years

Increasing the use of wood in buildings is regarded by many as a key solution to tackle climate change. For this reason, a lot of research is carried out to develop new and innovative wood surface improvements and make wood more appealing through features such as increased durability, fire-retardancy, superhydrophobicity, and self-healing. However, in order to have a positive impact on the society, these surface improvements must be applied in real buildings. In this review, the last five years of research in the domain of wood surface improvements and modifications is first presented by sorting the latest innovations into different trends. Afterward, these trends are correlated to specifications representing different normative, ecologic and economic factors which must be considered when expecting to introduce a wood treatment to the market. With this review, the authors hope to help researchers to take into consideration the different factors influencing whether new innovations can leave the research laboratory or not, and thereby facilitate the introduction of new wood surface treatments in the society.

Polymers and Composites Derived from Castor Oil as Sustainable Materials and Degradable Biomaterials: Current Status and Emerging Trends

Recent years have seen rapid growth in utilizing vegetable oils to derive a wide variety of polymers to replace petroleum-based polymers for minimizing environmental impact. Nonedible castor oil (CO) can be extracted from castor plants that grow easily, even in an arid land. CO is a promising source for developing several polymers such as polyurethanes, polyesters, polyamides, and epoxy-polymers. Several synthesis routes have been developed, and distinct properties of polymers have been studied for industrial applications. Furthermore, fillers and fibers, including nanomaterials, have been incorporated in these polymers for enhancing their physical, thermal, and mechanical properties. This review highlights the development of CO-based polymers and their composites with attractive properties for industrial and biomedical applications. Recent advancements in CO-based polymers and their composites are presented along with a discussion on future opportunities for further developments in diverse applications.

Highly Hydrophobic and Self-Cleaning Heat-Treated Larix spp. Prepared by TiO2 and ZnO Particles onto Wood Surface

The deposition of TiO2/ZnO on heat-treated wood was prepared by a hydrothermal reaction and sol-gel method. Highly hydrophobic wood was successfully prepared with low surface free energy. The surface-modified wood samples were characterized by 3D-laser shape measurement microscopy, scanning electron microscopy, energy-dispersive spectroscopy, and Fourier transform infrared spectroscopy for the microstructure and chemical composition investigation. The deposited TiO2 or ZnO markedly made the wood surface brighter, which was demonstrated by visual observation and spectrophotometer. The TiO2/ZnO particles were successfully loaded onto the surface of the wood, proven by SEM-EDS and FTIR analyses. The contact angle of TiO2 and ZnO-modified wood reached 123.9° and 134.1° respectively, which is obviously higher than that of the control at 88.9°. The hydrophobic properties of the TiO2/ZnO modified wood samples were directly related to the shapes of clusters and spheres of particles, which increased the roughness of the wood surface. This study shows the hydrophobic properties of the TiO2/ZnO-modified wood and provides the color and roughness changes for the painting process of heat-treated wood.

Innovation in Wood Preservation

The wood preservation industry has depended on toxicity as a mechanism of effectiveness against decay fungi to extend the life of wood used in adverse conditions. An alternative to toxicity, however, is to study and understand the mechanism of fungal attack and stop it before it can start. Knowing that fungi need moisture for colonization, a new approach to wood preservation is to lower the cell wall moisture content below that needed for fungal attack. Acetylation chemistry is known to reduce the moisture content in the cell wall, and it was used to study moisture levels in the bulk cell wall and in the isolated cell wall polymers. Resistance to brown-rot was determined using a 12-week soil block test with Gloeophyllum trabeum. Weight loss was measured and an analysis of what was lost was determined.