Display omitted
•The utilization of vegetable oil for polyurethane synthesis has been researched and documented in the past decade.•Derivatives of vegetable oil are also known to be an excellent ...feedstock for polyurethane coatings.•Challenges continue to remain in terms of properties, performance and reaction conditions of polyurethane.•The review focuses on various synthesis routes that transform triglycerides and derivatives into polyurethane precursors.•Different types of polyurethane coatings have also been studied in this review.
The scientific community has been pooling all its resources, for the past decade, towards the development of “sustainable development” to usher into an eternally green and sustainable tomorrow. As part of this endeavor, the conventional petroleum-based polyurethane (PU) coatings have been replaced by their green counterparts, i.e., bio-based polyurethane coatings. These green alternatives provide a suitable replacement for the coating industry due to their easy availability, biodegradability, low cost, and lesser environmental impact. The production of such green PU coatings is further facilitated by the utilization of bio-based materials, including vegetable oils and their derivatives such as methyl ester, fatty acid, and other bio-renewable sources. This review discusses the different chemical modifications used to convert these bio-based precursors into desired polyols and isocyanates. Furthermore, the formulation of different PU coatings and their subsequent potential applications are also elaborated on in this review. The coatings sector has already been introduced to the notion of eco-friendly technologies such as UV-curable, less or zero solvent, waterborne, hyperbranched, and high solids coatings, complemented by the incorporation of renewable feedstock in monomer synthesis. The review examines the future hurdles that hinder the utilization of these materials in a wide range of applications and presents technologies that facilitate potential solutions and mention key players in the coating sectors that are at the forefront of bringing these revolutionary changes.
Polyurethane (PU) coatings were prepared using polyesteramide polyols based on different types of vegetable oils and itaconic acid. Long chain fatty diethanolamides were synthesized using the ...amidation of linseed/castor/karanja oils and the desired hydroxyl group was introduced via esterification reaction with itaconic acid to yield polyesteramide polyols. Its structural elucidation was carried out using Fourier-transform infrared spectroscopy (FT-IR) and proton nuclear magnetic resonance (1H NMR). The study of crosslinking these polyols with hexamethylene diisocyanate (HDI-trimer and HDI-biuret) shows that the isocyanate structure and functionality contribute to the final polyurethane coatings properties. Various optical, mechanical, and durability performance of the cured PU metal coating films were examined. The gel content method was used to compare the crosslink density of various PU films. The thermal properties of the PU coating, including stability and glass transition temperature (Tg), were assessed using thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The corrosion resistance of PU coatings was analyzed by employing electrochemical impedance spectroscopy (EIS). PU metal coatings display superior gloss, adhesion, and chemical resistance properties. Differences in fatty acid compositions of linseed/castor/karanja oils were found to influence the air curing and mechanical and corrosion resistance properties of PU metal coatings. The use of itaconic acid and vegetable oils in the synthesis of these polyols contributes to their bio based characteristics and permits replacing the currently used petroleum-based polyols.
Display omitted
•Use of vegetable oils and bio-based itaconic acid for synthesis of polyesteramide polyols.•Preparation of air cured polyurethane coatings from crosslinking of bio-based polyols with HDI-trimer and HDI-biuret.•Effect of hydroxyl functionalities and unsaturation on the performance of PU coatings.•Polyurethane metal coatings showed superior gloss, adhesion, chemical resistance and corrosion resistance properties.
Display omitted
•Green synthesis of dimer fatty acid based polyurethane acrylate (PUA) oligomer.•Preparation of UV curable coatings from PUA with HDDA and TMPTA reactive diluents.•UV cured PUA ...coatings showed superior flexibility, impact, hydrophobicity and resistance to volume shrinkage.•Renewable dimer acid are excellent candidate for future polyurethane coatings.
A UV-curable polyurethane acrylate (PUA) oligomer was prepared from dimer acid (DA) based polyester polyol (DAPEP) with a monofunctional acrylate precursor which was developed upon isophorone diisocyanate (IPDI) reacted with 2-hydroxyethyl methacrylate (HEMA). The structural elucidation of synthesized dimer acid based PUA (DAPUA) oligomer was verified through Fourier-transform infrared spectroscopy (FT-IR) and Proton nuclear magnetic resonance (1H NMR). A series of UV cured coatings were prepared by adding trimethylolpropane triacrylate (TMPTA) and 1,6-hexanediol diacrylate (HDDA) reactive diluents in varying percentages (10−30 wt%) to PUA oligomer. The bio-coatings exhibited exceptional results, including the highest thermal degradation temperature of 382–422 °C, glass transition temperature (Tg) of 56.38–66.27 °C, the tensile strength of 17.3–30.6 MPa, volume shrinkage of 6.19–9.13 %, and surface roughness of 4.89–28.21 nm. Compared to vegetable oil based UV-curable coatings, long chain dimer acid based PUA oligomer coatings exhibited excellent flexibility, impact, hydrophobicity, and resistance to volume shrinkage.
Bio-based polyurethane (PU) coatings were prepared from novel branched isostearic acid (ISA) and long chains dimer fatty acid. Fatty amide was synthesized by the amidation of ISA with diethanolamine ...and the required hydroxyl functionality was developed via condensation polymerization with dimer fatty acid to produce polyesteramide polyol. The structure of the synthesized ISA based fatty amide (ISAFA) and polyesteramide polyol (ISAPEP) were identified using Fourier-transform infrared spectroscopy (FT-IR) and proton nuclear magnetic resonance (
1
HNMR). The number average molecular weight of prepared polyesteramide polyol was assessed by gel permeation chromatography (GPC), while the rheological behavior was examined by the rheometer. Polyurethane metal coatings were developed from polyesteramide polyol, which crosslinks with hexamethylene diisocyanate (PU-H) and toluene diisocyanate (PU-T) and studied the influence of isocyanate structure on final PU coatings. A comparison in the crosslinks density of PU films was investigated by the gel content method. Differential scanning calorimetry (DSC) and thermo gravimetric analysis (TGA) were performed to evaluate the glass transition temperature (T
g
) and thermal stability of the PU coatings. The surface roughness of prepared PU coatings was examined by Atomic force microscopy (AFM). The PU coated metal panels and films were examined for swelling resistance, hydrophobicity, mechanical, and coating properties. Results confirmed that bio-based long chain fatty acids provided hydrophobicity, flexibility and impact resistance to final PU coatings. It also noted that PU-T coating resulted in increasing thermal, mechanical, and coating properties compared to PU-H coating and this resulted from the structure of TDI, which contribute to higher crosslink density (i.e. presence of aromatic ring).
Graphical Abstract
The focus of the present study is to utilize a by‐product obtained during extraction of tocopherols, a valuable vitamin E compound, from sea buckthorn (SBT) oil and in doing so find a reliable ...alternative to petrochemical based polyols. Bio‐based polyurethane (PU) is prepared by using SBT oil based fatty acid methyl ester polyesteramide polyols (SBTPEP) with toluene diisocyanate (TDI). The fatty acid methyl ester is converted to the corresponding fatty amide by reaction with diethanolamine. The formed fatty amide is then esterified with phthalic anhydride to synthesize polyesteramide polyol. Characterization techniques used to evaluate polyesteramide polyol are Fourier‐transform infrared spectroscopy (FTIR) and NMR. The cured PU coating is also put through various mechanical tests to analyze the physical properties. The cured PU coating shows good surface and mechanical properties. It shows a gloss value of 87.4 and passes impact, adhesion, and chemical resistance tests. It is hydrophobic which is evident from its contact angle of 100.2°. It has good thermal stability which is evident by its glass transition temperature of 53.9 °C. Use of phthalic anhydride contributes to the bio‐based characteristics of synthesized PU.
Practical Application: The present study presents a synthesis route which has minimal dependence on hazardous feedstock by utilization of green feedstock. The results obtained from physical and mechanical evaluations favor the use of this PU formulation in the coating sector. The adhesion and impact strength test results show potential application in the industrial sector coatings where the applied coat must be able to withstand high levels of physical stress and strain. The presence of aromatic rings and oil‐based moiety, that is the fatty acid hydrocarbon chain, contributes to the hydrophobic nature of the PU coating. Hydrophobic coatings have tremendous application in various fields such as marine coatings, automotive, electronics, and decorative coatings. These are potential fields of application for the synthesized green PU coating obtained from tocopherol extraction by‐products.
Utilization of oil byproducts helps to develop sustainable synthesis routes. One such byproduct is fatty acid (which is then esterified with methanol) during the tocopherol extraction from sea buckthorn oil. This fatty acid methyl ester is further subjected to chemical modifications of amidation and esterification to yield polyester polyol which is used to form polyurethane resin by crosslinking with an isocyanate.
Dimer fatty acid (DA)-based polyester polyols (DAP and DAP-Gs) were prepared successfully by DA and 1,6-hexanediol-glycerol through an esterification reaction. The structure elucidation of DAP and ...DAPGs was analyzed by Fourier transform infrared (FTIR), Nuclear magnetic resonance (NMR) and acid and hydroxyl values. To study the effect of chain extender on the final coating properties, a series of dimer acid-based PU (DAPU-G) coatings was prepared by incorporating glycerol in varying percentages (10 − 30 wt%) to DAP and crosslinked with hexamethylene diisocyanate-biuret (HDI-B). The motive of this finding was to study the effect of chain extender with DAP polyol on physico-mechanical, chemical resistance, crystallinity, and thermal performance of PU coatings. The results show that the incorporation of chain extender improved the final properties of PU coatings. Upon evaluating chemical resistance and coating properties, it was established that DAPU-G (10 − 30 wt%) coatings showed excellent performance compared to DAPU due to its higher crosslink density network. The thermal analysis outcomes exhibit that the glass transition temperature (T
g
) and thermal stability of PU coatings increased by adding a chain extender. Furthermore, the addition of a chain extender increased the chemical and water resistance property of PU coatings. Tensile properties of PU coatings increased from 14.7 − 30.68 MPa; meanwhile, elongation at break decreased from 8.3 to 4.8% with increment in glycerol content. This study exhibited that glycerol can substitute a partial petrochemical chain extender as a bio-based chain extender to prepare PU with an excellent coating performance.
Polymeric researchers are trying to use renewable resources for polymeric resins in the coating industry to reduce fossil or petroleum feedstock reliance significantly. The present research attempts ...to develop a polyurethane (PU) coating for the first time from Niger seed oil (NSO). The polyesteramide polyols are synthesized by amidation of Niger seed oil with diethanolamine and further esterification with different biobased dicarboxylic acids (phthalic, itaconic, and dimer) to introduce a required functionality of hydroxyl group. Spectroscopic studies of Niger‐seed‐oil‐based fatty diethanolamide and polyesteramide polyols are carried out by Fourier‐transform infrared spectroscopy and proton nuclear magnetic resonance. The polyurethane coatings are prepared from synthesized polyesteramide polyols and hexamethylene diisocyanate biuret (HDI‐B). The cross‐link density of PU coatings demonstrated by gel content method and the corrosion study is carried by salt water immersion technique. The PU coatings are also studied for glass transition temperature (Tg) and thermal stability by differential scanning calorimetry and thermogravimetric analysis.
Practical Applications: The long aliphatic chain provides flexibility, whereas the rigid structure of polyols enhances the hardness of PU coating. The phthalic‐based PU metal coatings depict excellent hardness, gloss, hydrophobicity, and chemical resistance compared to itaconic and dimer‐acid‐based PU.
Graphical reflects the amidation of Niger seed oil by using diethanolamine which results into diethanolamide. The diethanolamide further reacts with the dicarboxylic acids to form polyesteramide polyols. The polyesteramide polyol further cross‐links with the hexamethylene diisocyanate biurate (HDI‐B) to form a polyurethane (PU) coating. The PU coatings exhibit the anticorrosive nature. The biobased content demonstrates the importance of this green PU coating.
Epoxidation of soybean oil (ESBO) was carried out using Amberlyst 15 catalyst followed by ring opening using bio-based oleic acid to yield polyester polyol (ESOAP). Polyurethane (PU) coating was ...prepared by utilizing synthesized polyester polyol with hexamethylene diisocyanate (HDI) in the presence of dipentene as a green solvent. To meet industrial standards, biobased polyurethane coatings (Bio-PU) must match the performance of petroleum based polyurethane (Petro-PU) and hence a comparative study is carried out between synthesized bio based polyurethane coating and a petroleum based polyurethane coating. The characterization techniques like Fourier-transform infrared spectroscopy (FT-IR) and Nuclear magnetic resonance (NMR) used for structural elucidation of epoxidized soybean oil and polyester polyol. The cured Bio-PU coating shows good optical and mechanical properties compared to Petro-PU coating. Differential scanning calorimetry (DSC) and Thermo gravimetric analysis (TGA) analysis were carried out to analyse the glass transition temperature (Tg) and thermal stability of the PU coatings. The Electrochemical impendence spectroscopy (EIS) study revealed that the Bio-PU coating exhibited high corrosion resistance (1.23 × 10
7
) against Petro- PU coating. The bio-based content of synthesized polyurethane was calculated to 88.43%. The contribution of oleic acid grants a novel approach to this scheme along with making the end application of coatings more environment friendly.
The present study deals with the extraction of karanjin from Karanja leaves with the help of ultrasonic extraction. Karanjin is an important bioactive compound present in Karanja seed and leaves oil. ...The effect of various parameters such as solvents, temperature, time, ultrasonic power, duty cycle, stirring speed, and solute-to-solvent ratio on karanjin yield was investigated. The identification of extracted karanjin was assessed by high-performance liquid chromatography. The experimental results indicated that the extraction yield by ultrasound-assisted extraction (UAE) has increased by two times than the conventional (soxhlet) method. It is also found that for achieving the same amount of yield, soxhlet required 24 h, while UAE takes only 30 min. The yield of karanjin increased with the solute-to-solvent ratio, whereas an increase in temperature leads to a reduction in karanjin yield. Particle size distribution and scanning electron microscope images of the plant cells after UAE treatment indicate microfractures on the plant cell's surface by the cavitation phenomenon. It also gives the visuals confirmation of the sonication effect. During the sonication, 12.03 kJ/g of energy was delivered, while 48 kJ/g of energy is required for the soxhlet method. Karanjin can be a promising biopesticide or bioinsecticide material in a wide range of applications. Thus, the developed UAE method provides a better process intensification approach to extract karanjin and makes it an exciting alternative for downstream processing.
Graphic abstract
A new approach for synthesized amine functionalized graphene oxide (AFGO) was used by diethylenetriamine as a reducing or functionalizing agent. The purpose of this work is to determine the effect of ...AFGO on the mechanical and thermal properties of epoxy nanocomposites. In addition, the optimization of various weight percentages of AFGO was carried out. Physical and chemical characterizations were also reported to determine the effects of AFGO. The structure and morphology of the AFGO nanosheets were confirmed by fourier transform infrared spectroscopy, energy dispersive spectroscopy, X-ray diffraction analysis, and field emission scanning electron microscopy. Successful formation of amide bonds through graphene oxide (GO) sheet functionalization was proved by characterizations. Solution blending, as a simple method, was used for composite formation. The mechanical and thermal properties of the epoxy/AFGO composites were assessed. There was increment in tensile strength by 67%, flexural strength by 51%, and impact strength by 152% at 0.3 wt% loading of AFGO in epoxy composites. Similarly, the increment in hardness was also observed from 0.1 to 0.3 wt% of AFGO loading. The glass transition temperature of epoxy/AFGO nanocomposites effectively improved from 88.4 to 97.3 °C. The thermal stability of epoxy/AFGO nanocomposite increased from 351 to 358 °C.
