Recent advances in vegetable oil-based polyurethanes

Preparation of Bio-Based Polyurethane Coating from Citrullus colocynthis Seed Oil: Characterization and Corrosion Performance

In this study, a new epoxidized oil from Citrullus colocynthis seed oil (CCSO) was obtained for a potential application in the formulation of polyurethane coatings. Initially, the fatty acid composition of CCSO was determined by gas chromatography-mass spectrometry (GC-MS). Subsequently, the epoxidation of CCSO was performed with in situ generated peracetic acid, which was formed with hydrogen peroxide (30 wt.%) and glacial acetic acid and catalyzed with sulfuric acid. The reaction was continued at a molar ratio of 1.50:1.0 of hydrogen peroxide to double bond (H2O2:DB) for 6 h at a controlled temperature of 60 °C. The resulting epoxidized oil was then used to produce a bio-based polyol by hydroxylation. The molar ratio of epoxy groups to methanol and distilled water was maintained at 1:11:2, and the reaction was carried out for 2 h at a controlled temperature of 65 °C. The major functional groups of the epoxidized oil and its polyol were validated by Fourier-transform infrared (FT-IR) and proton nuclear magnetic resonance (1H NMR) spectroscopies. A polyurethane (PU) coating was produced from the synthesized polyol and 3HDI isocyanurate, keeping the molar ratio of NCO:OH at 1:1. The resulting PU coating was then applied to glass and aluminum panels (Al 1001). After the film was cured, the properties of the PU coating were evaluated using various techniques including pencil hardness, pendulum hardness, adhesion, gloss, chemical resistance, and EIS tests. The results show that the PU coating obtained from CCSO is a promising new raw material for coating applications.

Recent Advances in Tailored Fabrication and Properties of Biobased Self-Healing Polyurethane

With the emergence of challenges in the environmental degradation and resource scarcity fields, the research of biobased self-healing polyurethane (BSPU) has become a prevailing trend in the technology of the polyurethane industry and a promising direction for developing biomass resources. Here, the production of BSPU from lignocellulose, vegetable oil, chitosan, collagen, and coumarin is classified, and the principles of designing polyurethane based on compelling examples using the latest methods and current research are summarized. Moreover, the impact of biomass materials on self-healing and mechanical properties, as well as the tailored performance method, are presented in detail. Finally, the applications of BSPU in biomedicine, sensors, coatings, etc. are also summarized, and the possible challenges and development prospects are explored to helpfully make progress in the development of BSPU. These findings demonstrate valuable references and practical significance for future BSPU research.

A high-efficient antibacterial and biocompatible polyurethane film with Ag@rGO nanostructures prepared by microwave-assisted method: Physicochemical and dermal wound healing evaluation

Wound infections are a significant issue that can hinder the wound healing process. One way to address this problem is by enhancing the antibacterial activity of wound dressings. Accordingly, this work focuses on developing a castor-oil-based antibacterial polyurethane nanocomposite film impregnated with silver nanoparticles (AgNPs) decorated on the surface of reduced graphene oxide (rGO) nanostructures (Ag@rGO). To this aim, rGOs act as a platform to stabilize AgNPs and improve their bioavailability and dispersion quality within the PU film. The microwave-assisted synthesis of Ag@rGO nanohybrids was proved by FTIR, XRD, TGA, FE-SEM, EDS, and TEM analyses. Compared to PU/GO, the effect of Ag@rGO nanohybrids on thermo-mechanical features, morphology, antibacterial activity, cytocompatibility, and in vivo wound healing was assessed. SEM photomicrographs revealed the enhanced dispersion of Ag@rGO nanohybrids compared to GO nanosheets. Besides, according to XRD results, PU/Ag@rGO nanocomposite film demonstrated higher microphase mixing, which could be due to the finely dispersed Ag@rGO nanostructures interrupting the hydrogen bonding interactions in the hard segments. Moreover, PU/Ag@rGO nanocomposite showed excellent antibacterial behavior with completely killing E. coli and S. aureus bacteria. In vitro and in vivo wound healing studies displayed PU/Ag@rGO film effectively stimulated fibroblast cells proliferation, migration and re-epithelialization. However, the prepared antibacterial PU/Ag@rGO nanocomposite film has the potential to be used as a biomaterial for dermal wound healing applications.

Recent advances in synthesis of polymers based on palm oil and its fatty acids

Palm oil is a versatile bio-renewable resource for consumer products, oleochemicals, and biofuels. The utilization of palm oil in polymer production as a bio-based polymer is considered a promising alternative to conventional petrochemical-based polymers due to its non-toxicity, biodegradability, and vast obtainability. Triglycerides and fatty acids in palm oil and their derivatives can be utilized as bio-based monomers for synthesizing polymers. This review summarizes the recent advancement in using palm oil and its fatty acids for polymer synthesis and their applications. Moreover, this review will overview the most commonly used synthesis pathways for producing palm oil-based polymers. Therefore, this review can be used as a reference for designing a new approach to synthesizing palm oil-based polymers with desired properties.

Supramolecular structure, relaxation behavior and free volume of bio-based poly(butylene 2,5-furandicarboxylate)-block-poly(caprolactone) copolyesters

In the present study, a fully plant-based sustainable copolyester series, namely poly(butylene 2,5-furandicarboxylate)-block-poly(caprolactone)s (PBF-block-PCL)s were successfully synthesized by melt polycondensation combining butylene 2,5-furandicarboxylate with polycaprolactone diol (PCL) at different weight ratios. Differential scanning calorimetry (DSC) showed that only PBF underwent melting, crystallization from the melt, and cold crystallization. Thermogravimetric analysis (TGA) revealed outstanding thermal stability, exceeding 305 °C, with further improvement in thermal and thermo-oxidative stability with increasing PCL content. Broadband dielectric spectroscopy (BDS) revealed that at low temperatures, below the glass transition (T_g) all copolyesters exhibited two relaxation processes (β₁ and β₂), whereas the homopolymer PBF exhibited a single β-relaxation, which is associated with local dynamics of the different chemical bonds present in the polymer chain. Additionally, it was proved that an increase in PCL content affected the dynamics of the chain making it more flexible, thus providing an increase in the value of the room temperature free volume fractions (f_v) and the value of elongation at break. These effects are accompanied by a decrease in hardness, Young's modulus, and tensile strength. The described synthesis enables a facile approach to obtain novel fully multiblock biobased copolyesters based on PBF and PCL polyesters with potential industrial implementation capabilities.

Sustainable cycloaliphatic polyurethanes: from synthesis to applications

Polyurethanes (PUs) are a versatile and major polymer family, mainly produced via polyaddition between polyols and polyisocyanates. A large variety of fossil-based building blocks is commonly used to develop a wide range of macromolecular architectures with specific properties. Due to environmental concerns, legislation, rarefaction of some petrol fractions and price fluctuation, sustainable feedstocks are attracting significant attention, e.g., plastic waste and biobased resources from biomass. Consequently, various sustainable building blocks are available to develop new renewable macromolecular architectures such as aromatics, linear aliphatics and cycloaliphatics. Meanwhile, the relationship between the chemical structures of these building blocks and properties of the final PUs can be determined. For instance, aromatic building blocks are remarkable to endow materials with rigidity, hydrophobicity, fire resistance, chemical and thermal stability, whereas acyclic aliphatics endow them with oxidation and UV light resistance, flexibility and transparency. Cycloaliphatics are very interesting as they combine most of the advantages of linear aliphatic and aromatic compounds. This original and unique review presents a comprehensive overview of the synthesis of sustainable cycloaliphatic PUs using various renewable products such as biobased terpenes, carbohydrates, fatty acids and cholesterol and/or plastic waste. Herein, we summarize the chemical modification of the main sustainable cycloaliphatic feedstocks, synthesis of PUs using these building blocks and their corresponding properties and subsequently present their major applications in hot-topic fields, including building, transportation, packaging and biomedicine.

Polyurethane foams from vegetable oil-based polyols: a review

Polyurethane is a versatile material that can be converted into various forms according to applications. PU foams or PUFs are the most commonly used polyurethanes. These are materials of low density and low thermal conductivity that make them highly suitable for thermal insulating applications. Most of the synthesis of PUFs is still based on the petrochemical industry. There are issues associated with the oil industry, such as environmental pollution, sustainability, and market instability. More recently, we have experienced the COVID-19 pandemic which has destroyed the global supply chain of raw materials. Such sudden disruption of the supply chain affects the global economy. To eliminate the reliance on special ingredients, it is important to find and produce alternate and domestic raw materials. Vegetable oils are organic, cost-effective, and economically viable and present in abundant amounts. The oil consists of triglycerides. It can be functionalized to provide polyol for PU foam synthesis. Herein, we review the literature on factors influencing the properties of PUFs depending on polyols from vegetable oil as well as present a glimpse of the conversion of vegetable oils into polyols for PUF synthesis.

Leads and hurdles to sustainable microbial bioplastic production

Indiscriminate usage, disposal and recalcitrance of petroleum-based plastics have led to its accumulation leaving a negative impact on the environment. Bioplastics, particularly microbial bioplastics serve as an ecologically sustainable solution to nullify the negative impacts of plastics. Microbial production of biopolymers like Polyhydroxyalkanoates, Polyhydroxybutyrates and Polylactic acid using renewable feedstocks as well as industrial wastes have gained momentum in the recent years. The current study outlays types of bioplastics, their microbial sources and applications in various fields. Scientific evidence on bioplastics has suggested a unique range of applications such as industrial, agricultural and medical applications. Though diverse microorganisms such as Alcaligenes latus, Burkholderia sacchari, Micrococcus species, Lactobacillus pentosus, Bacillus sp., Pseudomonas sp., Klebsiella sp., Rhizobium sp., Enterobacter sp., Escherichia sp., Azototobacter sp., Protomonas sp., Cupriavidus sp., Halomonas sp., Saccharomyces sp., Kluyveromyces sp., and Ralstonia sp. are known to produce bioplastics, the industrial production of bioplastics is still challenging. Thus this paper also provides deep insights on the advancements made to maximise production of bioplastics using different approaches such as metabolic engineering, rDNA technologies and multitude of cultivation strategies. Finally, the constraints to microbial bioplastic production and the future directions of research are briefed. Hence the present review emphasizes on the importance of using bioplastics as a sustainable alternative to petroleum based plastic products to diminish environmental pollution.

Fire retardancy, thermal, and physico-mechanical properties of semi-rigid water-blown polyurethane foam from palm oil-based polyol

This paper presents the experimental work undertaken to assess rigid palm oil-based polyurethane (PU) foam. The bio-composite foam was characterized to determine its foaming kinetics and morphology, as well as fire retardancy, thermal, and mechanical responses, which was later compared with its petrochemical-based counterpart. The palm oil-based foam displayed poor fire-retardancy performance based on Limiting Oxygen Index (LOI) and UL-94 Vertical Combustion Test. Although less char residue was produced, the palm oil-based PU foam exhibited higher onset degradation temperatures, indicating improved thermal stability. The Scanning Electron Microscopy (SEM) revealed finer cell sizes for the bio-based foam and a higher fraction of open cell structures, which affected its density and compressive properties. As a conclusion, the palm oil-based PU foam is a viable alternative to be utilized in low load-bearing and thermal environment applications.

Polynomial Multiple Regression Analysis of the Lubrication Effectiveness of Deep Drawing Quality Steel Sheets by Eco-Friendly Vegetable Oils

Ensuring adequate lubrication is a key task in the sheet metal forming process. The replacement of commonly used synthetic lubricants in metal forming operations by eco-friendly equivalents is a way to introduce sustainable manufacturing. In this paper, six kinds of vegetable oils (linseed, palm, sunflower, cotton seed, soybean and coconut) were used to study the effect of lubricant type on the value of the coefficient of friction (COF) in sheet metal forming. The strip drawing test was used to simulate the friction conditions. The tests were carried out for various lubrication conditions and pressures. The polynomial quadratic regression model was used to determine the relationship between the input variables (test conditions) and the COF. For the range of the nominal pressures considered (2–12 MPa), the following oils provided the highest lubrication efficiency: palm, sunflower and cotton seed. These oils decreased the value of the COF by about 11–16% depending on the nominal pressure. Linseed oil had the most unfavourable properties, reducing the COF by about 7–12%. For the whole range of pressures considered, the increase in the viscosity of the oil caused a reduction in the value of the COF. The effect of oil density on the COF value was similar. The most unfavourable friction conditions occurred when there was low density and low viscosity of the oil at the same time.

Advanced Methods for Hydroxylation of Vegetable Oils, Unsaturated Fatty Acids and Their Alkyl Esters

Vegetable oils and their derivatives have great potential as renewable and sustainable raw materials for the production of polyurethanes and bio-based polyols. For industry an important process is their modification. Chemical reactions that are carried out on vegetable oils and their derivatives are: transesterification, auto-oxidation, hydrogenation, epoxidation, hydroxylation, acrylation, isocyanation and others. One of the modifications are reactions performed on double bonds and/or carbonyl moieties of plants oils and their derivatives. These reactions result in products that are actively used as binders in coating materials due to their unique structural properties. In this manuscript, we describe important technological methods for the introduction of hydroxyl groups: opening of oxirane rings by nucleophilic reagents such as: water, alcohols, glycols, amino alcohols, carboxylic acids; direct hydroxylation of unsaturated bonds with carboxylic peracids in combination with hydrolysis of carboxyl groups and hydration; hydroformylation of unsaturated bonds with subsequent hydrogenation and alkoxylation; and ozonolysis of unsaturated bonds in combination with subsequent hydrogenation and alkoxylation.

Application of Different Vegetable Oils as Processing Aids in Industrial Rubber Composites: A Sustainable Approach

Rubber composites based on renewable vegetable oils are being increasingly developed, as these materials significantly reduce the use of petroleum-based carcinogenic oils as plasticizers in rubber products. Apart from renewability, vegetable oils have some major advantages, such as easy availability, biodegradability, and environmentally friendly nature. Until now, vegetable oils, such as palm oil, soybean oil, and linseed oil, have been successfully used as processing oils to replace petroleum-based oils in engineered rubber composites. So far, the concept of a vegetable-oil-based plasticizer has been applied to rubber composites containing different industrially important fillers, like carbon black, silica, calcium carbonate, and expandable graphite. In the near future, the trend of utilizing vegetable-oil-based plasticizers may bring considerable advancements in the performance of filled rubber composites in an environmentally acceptable and sustainable manner.

Enhancing Thermal and Mechanical Properties of Ramie Fiber via Impregnation by Lignin-Based Polyurethane Resin

In this study, lignin isolated and fractionated from black liquor was used as a pre-polymer to prepare bio-polyurethane (Bio-PU) resin, and the resin was impregnated into ramie fiber (Boehmeria nivea (L.) Gaudich) to improve its thermal and mechanical properties. The isolated lignin was fractionated by one-step fractionation using two different solvents, i.e., methanol (MeOH) and acetone (Ac). Each fractionated lignin was dissolved in NaOH and then reacted with a polymeric 4,4-methane diphenyl diisocyanate (pMDI) polymer at an NCO/OH mole ratio of 0.3. The resulting Bio-PU was then used in the impregnation of ramie fiber. The characterization of lignin, Bio-PU, and ramie fiber was carried out using several techniques, i.e., Fourier-transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), pyrolysis-gas-chromatography-mass-spectroscopy (Py-GCMS), Micro Confocal Raman spectroscopy, and an evaluation of fiber mechanical properties (modulus of elasticity and tensile strength). Impregnation of Bio-PU into ramie fiber resulted in weight gain ranging from 6% to 15%, and the values increased when extending the impregnation time. The reaction between the NCO group on Bio-PU and the OH group on ramie fiber forms a C=O group of urethane as confirmed by FTIR and Micro Confocal Raman spectroscopies at a wavenumber of 1600 cm⁻¹. Based on the TGA analysis, ramie fiber with lignin-based Bio-PU had better thermal properties than ramie fiber before impregnation with a greater weight residue of 21.7%. The mechanical properties of ramie fiber also increased after impregnation with lignin-based Bio-PU, resulting in a modulus of elasticity of 31 GPa for ramie-L-isolated and a tensile strength of 577 MPa for ramie-L-Ac. The enhanced thermal and mechanical properties of impregnated ramie fiber with lignin-based Bio-PU resins could increase the added value of ramie fiber and enhance its more comprehensive industrial application as a functional material.

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.

Plant oil-based polymers

Polymer materials derived from natural resources have gained increasing attention in recent years because of the uncertainties concerning petroleum supply and prices in the future as well as their environmental pollution problems. As one of the most abundant renewable resources, plant oils are suitable starting materials for polymers because of their low cost, the rich chemistry that their triglyceride structure provides, and their potential biodegradability. This chapter covers the structure, modification of triglycerides and their derivatives as well as synthesis of polymers therefrom. The remarkable advances during the last two decades in organic synthesis using plant oils and the basic oleochemicals derived from them are selectively reported and updated. Various methods, such as condensation, radical/cationic polymerization, metathesis procedure, and living polymerization, have also been applied in constructing oil-based polymers. Based on the advance of these changes, traditional polymers such as polyamides, polyesters, and epoxy resins have been renewed. Partial oil-based polymers have already been applied in some industrial areas and recent developments in this field offer promising new opportunities.

Biodegradable Polyurethanes Based on Castor Oil and Poly (3-hydroxybutyrate)

Biodegradable polyurethanes (PUs) were produced from castor oil (CO) and poly (3-hydroxybutyrate) diol (PHBD) using hexamethylene diisocyanate as a crosslinking agent. PHBDs of different molecular weights were synthesized through transesterification of bacterial PHB and ethylene glycol by changing the reaction time. The synthesized PHBDs were characterized in terms of Fourier transform infrared and proton nuclear magnetic resonance spectroscopy. A series of PUs at different NCO/OH and CO/PHBD ratios were prepared. The resulting CO/PHBD-based PUs were then characterized in terms of mechanical and thermal properties. Increasing PHBD content significantly increased the tensile strength of CO/PHBD-based PUs by 300% compared to neat CO-based PU. CO/PHBD-based PUs synthetized from short chain PHBD exhibited higher tensile strength compared to those produced from long chain PHBD. As revealed by scanning electron microscopy analysis, such improvement in stiffness of the resulting PUs is due to the good compatibility between CO and PHBD. Increasing PHBD content also increased the crystallinity of the resulting PUs. In addition, higher degradation rates were obtained for CO/PHBD-based PUs synthetized from long chain PHBD compared to neat CO PU and PUs produced from short chain PHBD.

Bio-based polyurethane aqueous dispersions

With the advances of green chemistry and nanoscience, the synthesis of green, homogenous bio-based waterborne polyurethane (WPU) dispersions with high performance have gained great attention. The presented chapter deals with the recent synthesis of waterborne polyurethane with the biomass, especially the vegetable oils including castor oil, soybean oil, sunflower oil, linseed oil, jatropha oil, and palm oil, etc. Meanwhile, the other biomasses, such as cellulose, starch, lignin, chitosan, etc., have also been illustrated with the significant application in preparing polyurethane dispersions. The idea was to highlight the main vegetable oil-based polyols, and the isocyanate, diols as chain extenders, which have supplied a class of raw materials in WPU. The conversion of biomasses into active chemical agents, which can be used in synthesis of WPU, has been discussed in detail. The main mechanisms and methods are also presented. It is suggested that the epoxide ring opening method is still the main route to transform vegetable oils to polyols. Furthermore, the nonisocyanate WPU may be one of the main trends for development of WPU using biomasses, especially the abundant vegetable oils.

Lignin as a Partial Polyol Replacement in Polyurethane Flexible Foam

This study was focused on evaluating the suitability of a wide range of lignins, a natural polymer isolated from different plant sources and chemical extractions, in replacing 20 wt.% of petroleum-based polyol in the formulation of PU flexible foams. The main goal was to investigate the effect of unmodified lignin incorporation on the foam’s structural, mechanical, and thermal properties. The hydroxyl contents of the commercial lignins were measured using phosphorus nuclear magnetic resonance (³¹P NMR) spectroscopy, molar mass distributions with gel permeation chromatography (GPC), and thermal properties with differential scanning calorimetry (DSC) techniques. The results showed that incorporating 20 wt.% lignin increased tensile, compression, tear propagation strengths, thermal stability, and the support factor of the developed PU flexible foams. Additionally, statistical analysis of the results showed that foam properties such as density and compression force deflection were positively correlated with lignin’s total hydroxyl content. Studying correlations between lignin properties and the performance of the developed lignin-based PU foams showed that lignins with low hydroxyl content, high flexibility (low T_g), and high solubility in the co-polyol are better candidates for partially substituting petroleum-based polyols in the formulation of flexible PU foams intended for the automotive applications.

Fully Bio-Based Thermosetting Polyurethanes from Bio-Based Polyols and Isocyanates

The trend towards the utilization of bioresources for the manufacturing of polymers has led industry players to bring to the market new monomers. In this work, we studied 3 polyisocyanates and 2 polyols with high renewable carbon contents, namely L-lysine ethyl ester diisocyanate (LDI), pentamethylene-diisocyanate (PDI) isocyanurate trimer, and hexamethylene-diisocyanate (HDI) allophanate as the isocyanates, as well as castor oil and polypropanediol as the polyols. These monomers are commercially available at a large scale and were used in direct formulations or used as prepolymers. Thermosetting polymers with T_g values ranging from -41 to +21 °C and thermal stabilities of up to 300 °C were obtained, and the polymerization was studied using NMR, DSC, and rheology. Cured materials were also characterized using FTIR, DMA, gel content, and swelling index determinations. These high bio-based content materials can successfully be obtained and could be used as alternatives to petro-based materials.

Flexible Polyurethane Foams from Epoxidized Vegetable Oils and a Bio-Based Diisocyanate

Bio-polyols from epoxidized soybean and linseed oils and caprylic acid or 3-phenyl butyric acid were prepared using an environmentally friendly, solvent-free method evaluating the presence of triethylamine as catalyst. Side reactions, leading to a cross-linking structure with high density, were reduced, introducing the catalyst and properly tuning the reaction conditions. A medium functionality value of around 3 along with a hydroxyl number up to around 90 mg KOH/g, narrow polydispersity index, and relatively low molecular mass up to 2400 g/mol were the experimental targets. From selected bio-polyols and an aliphatic partially bio-based isocyanate, a series of water blown polyurethane (PU) foams was produced, estimating the effect of the chemical nature of substituents in the polyol backbone on the PU properties. The apparent density of the foams was in the range of 79–113 kg/m³, with higher values for foams from the aromatic acid. Flexible polyurethane foams with open cell structure from bio-based polyols were obtained, with higher cavity size and lower pore sizes for foams from caprylic acid. The bio-based flexible PU foams showed comparable Young’s moduli (14–18 kPa) and compression deflection values (4.6–5.5 kPa) and exhibited an almost complete recovery of their initial size.

Impact of Different Epoxidation Approaches of Tall Oil Fatty Acids on Rigid Polyurethane Foam Thermal Insulation

A second-generation bio-based feedstock-tall oil fatty acids-was epoxidised via two pathways. Oxirane rings were introduced into the fatty acid carbon backbone using a heterogeneous epoxidation catalyst-ion exchange resin Amberlite IR-120 H or enzyme catalyst Candida antarctica lipase B under the trade name Novozym^® 435. High functionality bio-polyols were synthesised from the obtained epoxidated tall oil fatty acids by oxirane ring-opening and subsequent esterification reactions with different polyfunctional alcohols: trimethylolpropane and triethanolamine. The synthesised epoxidised tall oil fatty acids (ETOFA) were studied by proton nuclear magnetic resonance. The chemical structure of obtained polyols was studied by Fourier-transform infrared spectroscopy and size exclusion chromatography. Average molecular weight and polydispersity of polyols were determined from size exclusion chromatography data. The obtained polyols were used to develop rigid polyurethane (PU) foam thermal insulation material with an approximate density of 40 kg/m³. Thermal conductivity, apparent density and compression strength of the rigid PU foams were determined. The rigid PU foams obtained from polyols synthesised using Novozym^® 435 catalyst had superior properties in comparison to rigid PU foams obtained from polyols synthesised using Amberlite IR-120 H. The developed rigid PU foams had an excellent thermal conductivity of 21.2-25.9 mW/(m·K).

Exploration of Sunflower Oil As a Renewable Biomass Source to Develop Scalable and Highly Effective Corrosion Inhibitors in a 15% HCl Medium at High Temperatures

The feasibility study of utilizing sunflower oil as renewable biomass source to develop highly effective inhibitors for mild steel corrosion (MS) in the 15% HCl medium was done by weight loss, potentiodynamic polarization (PDP), dynamic electrochemical impedance spectroscopy (DEIS), and electrochemical impedance spectroscopy (EIS), supported with energy-dispersive X-ray (EDX), atomic force microscopy (AFM), and field-emission scanning electron microscope (FESEM) techniques. Moreover, a complementary theoretical investigation was carried out to clarify the inhibition mechanism of inhibitors by density functional theory (DFT), density functional based tight-binding (DFTB), and molecular dynamics (MD) simulation approaches. The obtained results confirm that sunflower-oil-based corrosion inhibitor (SFOCI) has a significant anticorrosion property toward the dissolution of MS in 15% HCl solution in the temperature range 20-80 °C. In addition, the results show that SFOCI could provide an inhibition efficiency of 98 and 93% at 60 and 80 °C, respectively. The inhibition mechanism of SFOCIs was mixed-type and their adsorption on the surface of MS was mainly chemisorption. The FESEM and EDX studies proved the presence of SFOCI molecules on the surface of MS. In addition, the adsorption energy of SFOCI indicated an intense interaction between the inhibitor and surface of Fe. The results of this study could open a new window for the design and development of scalable and effective eco-friendly vegetable-oil-based corrosion inhibitors for highly corrosive solutions at high temperatures.

Structure–properties relationship of the polyurethanes that contain Schiff base in the main chain

This article studies the diversification of useful properties of polyurethane (PU) structures by the inclusion of new components. PUs containing a Schiff base in the main chain were synthesized by using N, N′-bis(salicylidene)-1,3-propanediamine as a chain extender. Novel Schiff base PUs were synthesized via a two-step polymerization starting from a Schiff base derivative diol chain extender with different molar ratios or by cross-linking with various natural raw materials. The sought after structures was confirmed by Fourier transform infrared spectra that showed the disappearance of the signals of both the hydroxyl and isocyanate groups. The thermal properties of these PUs were investigated by thermogravimetric analysis (TGA) and dynamic mechanical analysis (DMA). The initial degradation temperatures of the obtained PUs were found to be in the range of 300–350°C. Based on the results from DMA, the rigid structure of the Schiff base from the backbone of the PUs presented a higher storage modulus, results which may be connected to the physical cross-linking process of the macromolecules. Their optical properties were determined by fluorescence spectroscopy. The incorporation of Schiff base structures into the main PU chain generates new PU structures with improved thermomechanical properties, which includes possible bioactive Schiff base moieties, widening the range of practical applications for such polymers.

Eco-Friendly Castor Oil-Based Delivery System with Sustained Pesticide Release and Enhanced Retention

The deposition of pesticides and their retention on plant surfaces are critical challenges for modern precision agriculture, which directly affect phytosanitary treatment, bioavailability, efficacy, and the loss of pesticides. Herein, a novel and eco-friendly waterborne polyurethane delivery system was developed to enhance the spray deposition and pesticide retention on plant surfaces. More specifically, biobased cationic and anionic waterborne polyurethane dispersions were synthesized from castor oil. Both cationic and anionic polyurethane dispersions exhibited remarkable microstructural, amphiphilic, and nanoparticle morphologies with a core-shell structure that served to encapsulate a biopesticide (azadirachtin) in their hydrophobic cores (WPU-ACT). The results indicated that the cationic WPU-ACT carriers exhibited a better sustained release behavior and a better protective effect from light and heat for azadirachtin. In addition, the simultaneous spray of anionic and cationic WPU-ACT significantly enhanced the spray deposition and prolonged the retention of pesticides due to the reduced surface tension and surface precipitation induced by the electrostatic interaction when two droplets with opposite charges come into contact with each other. A field efficacy assessment also indicated that the simultaneous spray of anionic and cationic WPU-ACT could control the infestation of brown planthopper in rice crops. Castor oil-based waterborne polyurethanes in this study work as an efficient pesticide delivery system by exhibiting enhanced deposition, rainfastness, retention ability, protection, and sustained release behavior, holding great promise for spraying pesticide formulations in modern and environmentally friendly agricultural applications.

Production of Biodegradable Palm Oil-Based Polyurethane as Potential Biomaterial for Biomedical Applications

Being biodegradable and biocompatible are crucial characteristics for biomaterial used for medical and biomedical applications. Vegetable oil-based polyols are known to contribute both the biodegradability and biocompatibility of polyurethanes; however, petrochemical-based polyols were often incorporated to improve the thermal and mechanical properties of polyurethane. In this work, palm oil-based polyester polyol (PPP) derived from epoxidized palm olein and glutaric acid was reacted with isophorone diisocyanate to produce an aliphatic polyurethane, without the incorporation of any commercial petrochemical-based polyol. The effects of water content and isocyanate index were investigated. The polyurethanes produced consisted of > 90% porosity with interconnected micropores and macropores (37-1700 µm) and PU 1.0 possessed tensile strength and compression stress of 111 kPa and 64 kPa. The polyurethanes with comparable thermal stability, yet susceptible to enzymatic degradation with 7-59% of mass loss after 4 weeks of treatment. The polyurethanes demonstrated superior water uptake (up to 450%) and did not induce significant changes in pH of the medium. The chemical changes of the polyurethanes after enzymatic degradation were evaluated by FTIR and TGA analyses. The polyurethanes showed cell viability of 53.43% and 80.37% after 1 and 10 day(s) of cytotoxicity test; and cell adhesion and proliferation in cell adhesion test. The polyurethanes produced demonstrated its potential as biomaterial for soft tissue engineering applications.

Structural Insights of Humins/Epoxidized Linseed Oil/ Hardener Terpolymerization

Bio-based thermosetting resins were synthesized from a ternary composition: humins; epoxidized linseed oil (ELO); and an industrial hardener, Capcure3-800 (CAP). Humins are in a focused attention in the last years, as biorefinery by-product, therefore its valorization through materials design is very important. Here we present a structural study of terpolymerization of humins/ ELO/CAP. The reactivity of these systems was highlighted by in situ FT-IR and ¹H and ¹³C NMR. The integration of humins in thermosetting resins gives alternatives to new feedstocks for future bio-based materials.

Comparative Study of Aromatic and Cycloaliphatic Isocyanate Effects on Physico-Chemical Properties of Bio-Based Polyurethane Acrylate Coatings

Crude jatropha oil (JO) was modified to form jatropha oil-based polyol (JOL) via two steps in a chemical reaction known as epoxidation and hydroxylation. JOL was then reacted with isocyanates to produce JO-based polyurethane resin. In this study, two types of isocyanates, 2,4-toluene diisocyanate (2,4-TDI) and isophorone diisocyanate (IPDI) were introduced to produce JPUA-TDI and JPUA-IPDI respectively. 2,4-TDI is categorised as an aromatic isocyanate whilst IPDI is known as a cycloaliphatic isocyanate. Both JPUA-TDI and JPUA-IPDI were then end-capped by the acrylate functional group of 2-hydroxyethyl methacrylate (HEMA). The effects of that isocyanate structure were investigated for their physico, chemical and thermal properties. The changes of the functional groups during each synthesis step were monitored by FTIR analysis. The appearance of urethane peaks was observed at 1532 cm⁻¹, 1718 cm⁻¹ and 3369 cm⁻¹ while acrylate peaks were detected at 815 cm⁻¹ and 1663 cm⁻¹ indicating that JPUA was successfully synthesised. It was found that the molar mass of JPUA-TDI was doubled compared to JPUA-IPDI. Each resin showed a similar degradation pattern analysed by thermal gravimetric analysis (TGA). For the mechanical properties, the JPUA-IPDI-based coating formulation exhibited a higher hardness value but poor adhesion compared to the JPUA-TDI-based coating formulation. Both types of jatropha-based polyurethane acrylate may potentially be used in an ultraviolet (UV) curing system specifically for clear coat surface applications to replace dependency on petroleum-based chemicals.

High Functionality Bio-Polyols from Tall Oil and Rigid Polyurethane Foams Formulated Solely Using Bio-Polyols

High-quality rigid polyurethane (PU) foam thermal insulation material has been developed solely using bio-polyols synthesized from second-generation bio-based feedstock. High functionality bio-polyols were synthesized from cellulose production side stream—tall oil fatty acids by oxirane ring-opening as well as esterification reactions with different polyfunctional alcohols, such as diethylene glycol, trimethylolpropane, triethanolamine, and diethanolamine. Four different high functionality bio-polyols were combined with bio-polyol obtained from tall oil esterification with triethanolamine to develop rigid PU foam formulations applicable as thermal insulation material. The developed formulations were optimized using response surface modeling to find optimal bio-polyol and physical blowing agent: c-pentane content. The optimized bio-based rigid PU foam formulations delivered comparable thermal insulation properties to the petro-chemical alternative.

Synthesis and Antimicrobial Activity of Metal-Containing Linseed Oil-Based Waterborne Urethane Oil Wood Coatings

In this study, the antimicrobial agents of mono(hydroxyethoxyethyl)phthalate (M(HEEP)₂) with different metal of M = Zn, Mn, Pb, and Ca were synthesized from diethylene glycol (DEG), phthalic anhydride (PA), and divalent metal acetates including calcium acetate, zinc acetate, manganese acetate, and lead acetate, respectively. The waterborne urethane oil (WUO) dispersions synthesized from linseed oil, diisocyanates (hexamethylene diisocyanate (HDI) and isophorone diisocyanate (IPDI)), dimethylolpropionic acid at NCO/OH molars of 0.9, by acetone processing method were described as in our previous report. The M(HEEP)₂ antimicrobial agents as well as the commercial nanosilver powder were added into WUO dispersions as the antimicrobial coatings. The effects of various antimicrobial agents and dosages (0.0, 0.2, 0.6, 0.8, 1.0, 2.0, and 4.0 phr) on antimicrobial activity of WUO films against gram-negative bacterium of Escherichia coli, gram-positive bacterium of Staphylococcus aureus, brown-rot fungus of Gloeophyllum trabeum, and white-rot fungus of Lenzites betulina were assessed. In addition, the film properties of the best antimicrobial WUO coatings were also examined. The results showed that the antimicrobial agents of mono(hydroxyethoxyethyl) phthalate M(HEEP)₂ (M = Zn, Mn, Pb, and Ca) powders should certainly be synthesized by FTIR, ¹H-NMR, ¹³C-NMR, and energy-dispersive X-ray spectroscopy (EDS) identifications and the yields of them were 43–55%. The results also revealed that the WUO film synthesizing with HDI films containing Zn(HEEP)₂ of 2.0 phr and Pb(HEEP)₂ of 0.4 phr had the best antibacterial activity for E. coli and S. aureus, respectively. The IPDI films containing Zn(HEEP)₂ of 1.0 phr had the best antibacterial activity for both E. coli and S. aureus. For antifungal activity, the WUO film synthesizing with HDI films containing Pb(HEEP)₂ of 0.8 phr and Zn(HEEP)₂ of 2.0 phr as well as IPDI films containing Mn(HEEP)₂ of 0.2 phr and Zn(HEEP)₂ of 4.0 phr had the best performances against G. trabeum and L. betulina, respectively. Comparing with commercial nanoAg powder, the Zn(HEEP)₂ and Pb(HEEP)₂ had a superior antifungal efficiency for G. trabeum and L. betulina, while it had a slightly inferior efficiency in the antibacterial activity for E. coli and S. aureus. On the properties of WUO films, adding metal-containing antimicrobial agents could slightly enhance the thermal stability, but lowered the gloss of all films, however, the T_g value increased for HDI film and decreased for IPDI film. In addition to this, they had no significant difference in the film properties including hardness, impact resistance, bending resistance, adhesion, mass retention, and light-fastness between the WUO films with and without adding antimicrobial agents.