Bio-based Polyurethane Coatings Research Articles

New biobased polyurethane coatings

New biobased polyurethane coatings

Biobased polyurethane coatings with fast self-healing and tunable mechanical properties derived from curcumin and castor oil

Biobased thermosetting polymers have attracted interest owing to their renewable source materials, long service life, and properties comparable to those of petroleum-based materials. However, the fabrication of those that merge exquisite mechanical properties with fast self-healing performance has not been demonstrated to date. In this work, a biobased polyurethane coating was constructed using curcumin dioxime (CD), castor oil (CO), and isophorone diisocyanate (IPDI) to fulfill these features. The biobased CD monomer was prepared using curcumin and hydroxylamine hydrochloride and confirmed by nuclear magnetic resonance, flourier-transform infrared (FT-IR) spectra, and high-resolution mass spectrometry (HR-MS). To investigate the correlation between the mechanical properties and self-healing performance, a series of polyurethane coatings were fabricated by varying the ratio of CO to CD. The results showed that the crosslinking density (ve), glass transition temperature (Tg), and Young modulus of these coatings increased with the decrease in the ratio of CO to CD, leading to tunable mechanical properties. In particular, the tensile strength and elongation of the COPU-4 coating were as high as 17.2 MPa and 295 %, respectively. The stress relaxation experiments revealed that these coatings exhibited low activation energy (Ea), as low as 28.3 kJ/mol for COPU-5. Besides, all COPU-X coatings demonstrated self-healing efficiency higher than 71 % within 1 min at 90 °C, and some of them even reached >90 % after 8 min. The results demonstrate the promising tunable mechanical and excellent self-healing properties of these novel biobased polyurethane coatings and pave the way for the development of bioderived sustainable thermosetting polymers.

Introduction of bio-based hard segment as an alternative strategy to environmentally friendly polyurethane coated urea

Improved degradation performance of bio-based polyurethane coatings has become a significant challenge for agricultural applications of controlled-release fertilizers. In this work, petroleum-based isocyanate components were innovatively replaced with lysine diisocyanate (LDI) ingredients in various ratios by the in-situ reaction with castor oil to synthesize high bio-based content polyurethane coating materials. The chemical structure and properties of the coatings were also investigated to propose the mechanism of LDI-mediated coatings controlled release and degradation performance. The experiment results indicate that as the LDI content increased, the coatings’ thermodynamic stability, cross-linking density, and controlled release performance decreased while their hydrophilicity and degradation performance increased. Compared to other coated ureas, the coated urea with the 1:1 replacement ratio of petroleum-based isocyanate performed well and had adjustable controlled release performance. Its release period was regulated by adjusting the coating rate and reached 60 days with the 3 % coating rate. With the increase of the lysine component, the degradation performance of the coating materials was improved till the replacing ratio of petroleum-based isocyanate was higher than 1:1. In all, the introduction of bio-based isocyanate is an alternative way further to enhance the degradation performance of the coating materials, and the coatings were non-toxic to rice seeds. The coordination of the controlled release and degradation performance of the coatings can be achieved by adjusting the content of LDI. This research designed a novel strategy to solve the bottleneck problem of bio-based polyurethane coating degradation in coated fertilizers.

Development of BioPolyurethane Coatings from Biomass-Derived Alkylphenol Polyols-A Green Alternative.

Bio-based polyols were obtained from the thermochemical liquefaction of two biomass feedstocks, pinewood and Stipa tenacissima, with conversion rates varying between 71.9 and 79.3 wt.%, and comprehensively characterized. They exhibit phenolic and aliphatic moieties displaying hydroxyl (OH) functional groups, as confirmed by attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR) and nuclear magnetic resonance spectroscopy (NMR) analysis. The biopolyols obtained were successfully employed as a green raw material to produce bio-based polyurethane (BioPU) coatings on carbon steel substrates, using, as an isocyanate source, a commercial bio-based polyisocyanate-Desmodur® Eco N7300. The BioPU coatings were analyzed in terms of chemical structure, the extent of the reaction of the isocyanate species, thermal stability, hydrophobicity, and adhesion strength. They show moderate thermal stability at temperatures up to 100 °C, and a mild hydrophobicity, displaying contact angles between 68° and 86°. The adhesion tests reveal similar pull-off strength values (ca. 2.2 MPa) for the BioPU either prepared with pinewood and Stipa-derived biopolyols (BPUI and BPUII). Electrochemical impedance spectroscopy (EIS) measurements were carried out on the coated substrates for 60 days in 0.05 M NaCl solution. Good corrosion protection properties were achieved for the coatings, with particular emphasis on the coating prepared with the pinewood-derived polyol, which exhibited a low-frequency impedance modulus normalized for the coating thickness of 6.1 × 1010 Ω cm at the end of the 60 days test, three times higher than for coatings prepared with Stipa-derived biopolyols. The produced BioPU formulations show great potential for application as coatings, and for further modification with bio-based fillers and corrosion inhibitors.

Life Cycle Environmental Impact Considerations in the Design of Novel Biobased Polyurethane Coatings

Substituting fossil-based with biobased chemical building blocks can potentially decrease the environmental impact of polyurethane (PU) coating production. This study applies life cycle assessment methods in the early development of three processes that incorporate biobased elements into PU coating production: a fully biobased coating made with organosolv lignin (OSL) and a biobased cross-linker from vanillic acid (VA) and two hybrid coatings made with a fossil-based cross-linker and either OSL or depolymerized OSL. Coatings with biobased elements had impacts of 1.5, 2.6, and 19.9 kg CO2eq/kgcoating for coatings made with OSL, depolymerized OSL, and the fully biobased coating, respectively. Emissions are mostly associated with the fossil-based cross-linker in hybrid coatings and with solvents and heat needed for the production of the biomass-derived cross-linker. While this study demonstrates that the use of biobased compounds in hybrid coatings can reduce the environmental impacts of PU coatings in comparison to fossil-based versions, additional development of biobased cross-linkers and research into end-of-life scenarios are needed to further reduce the environmental impacts of biobased PU coating production.

Behaviour of concrete specimens retrofitted with bio-based polyurethane coatings under dynamic loads

Experimental investigation was conducted using concrete specimens to assess the effectiveness of bio-based polyurethane (PU) coating synthesized from palm kernel oil in enhancing the dynamic mechanical response of concrete specimens under quasi-static and dynamic loads. The dynamic loading condition was simulated by conducting three-point bending tests at a strain rate of 0.067 s−1, and simultaneously, under quasi-static loading (strain rate of 0.00033 s−1) conditions. The application of PU layer(s) (either on the impact face, rear face, or on both faces of the concrete specimens) increases the dynamic resistance of the concrete element, which can be enhanced by increasing coating thickness on either face of the concrete element. Under dynamic conditions, with 10% of total coating thickness compared to the beam depth, strain during ultimate failure, and strain energy density were enhanced significantly with marginal enhancement in the ultimate flexural strength. PU coating does not debond during ultimate failure of the test specimens which implies good adhesion characteristics, and even with minimum coating thickness (2.5%), drastic fragmentation effects can be reduced. Bio-based PU is a green material and application of PU coating provides a viable and sustainable technique for protecting concrete structures against dynamic loads.

Self-healing ability based on hydrogen bonds in organic coatings for corrosion protection of AA1200

Biobased polyurethane coatings derived from vegetable oils, with 2 different compositions, were prepared and applied on the AA1200 aluminum alloy to confer corrosion protection. The influence of the ratio between the polyester (flexible segment) and the prepolymer (rigid segment) was investigated. Infrared spectroscopy studies evidenced the difference between the areas of the bands (NH) and optical and scanning electron microscopy evidenced the morphological features of the coating surface before and after immersion in aggressive medium. The barrier properties and anti-corrosion performance of the coatings were evaluated by electrochemical impedance spectroscopy and the results revealed an increase of impedance over the immersion time. Localized corrosion studies confirmed the self-healing effect in coatings formulated with the highest content of polyester.

Utilization of oleic acid in synthesis of epoxidized soybean oil based green polyurethane coating and its comparative study with petrochemical based polyurethane

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 × 107) 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.

Biobased Polyurethane Coatings with High Biomass Content: Tailored Properties by Lignin Selection

New biobased polyurethane (PU) coatings with high lignin content were developed and characterized in this work. These materials were based on a ?,?-diisocyanate monomer (1,4-bis(4-isocyanato-2-methoxyphenoxy)butane, VA-NCO) obtained from lignin-derived vanillic acid and its further cross-linking reaction with three different nonchemically modified technical lignins obtained from different pulping processes, namely, mild acetone organosolv, kraft, and soda. After determining the optimal VA-NCO/lignin mass ratio for each type of lignin, an in-depth characterization of the obtained PU coatings highlighted their high biomass content, effective cross-linking, improved thermal stability, hydrophobic character, good adhesion performance on different types of substrates, and tunable mechanical response. These properties were found to be well-correlated to the chemical-physical features of the parent lignins used (namely, molecular weight, glass transition temperature, distribution of phenylpropane subunits, and -OH content), thereby suggesting the possibility to predictively tailor the characteristics of such biobased PU coatings by lignin selection. The results of this study demonstrate that the reaction of a lignin-derived biobased diisocyanate with different chemically unmodified technical lignins represents an interesting pathway for the production of thermosetting PU coatings with a high biomass content that can find application as high-performance biobased materials alternative to traditional petroleum-based platforms. © 2019 American Chemical Society.

Synthesis and anticorrosion study of bio-based polyurethane coatings

In the present work, bio-based polyol resin was prepared from the non-edible castor oil with reaction of diethanol amine. The prepared polyol was utilized in polyurethane synthesis by using different types of diisocynates. The spectral study of synthesized polyol was performed by FTIR. The prepared polyurethanes were coated on mild steel panel and glass plate. The coating properties such as gloss, corrosion, electrochemical, mechanical properties were performed on mild steel plates. While coating films were obtained by peeling out from glass plates. TGA of coated films was performed for their thermal stability.

Synthesis of bio-based polyurethane coatings from vegetable oil and dicarboxylic acids

Bio-based thermoset polyurethane (PU) coatings comprised of polyesteramides were prepared from Gossypium arboreum (cotton seed) plant oil as a renewable source. Oil was first converted into fatty amide that was transformed into a series of polyesteramide polyols upon esterification with different dicarboxylic acids and anhydride. In the preparation of polyesteramide polyols, to increase bio-based content five different dicarboxylic acids of renewable nature were used to replace petroleum counterparts. Structures of polyols were confirmed using NMR and FT-IR spectroscopic techniques. Molecular weights of polyols were determined using gel permeation chromatography. Bio-based polyesteramide polyols were used to prepare thermoset PU by treating with aromatic diisocyanate. The thermal behavior of all prepared polyurethane coatings was determined using a thermogravimetric analyzer and differential scanning calorimeter. Coatings prepared using renewable source based polyesteramides were with high suitable curing, mechanical/chemical performances, alkali/acid resistance, and hydrophobicity. Compared to conventional PU coatings, the prepared coatings possess the superior properties such as gloss, adhesion, and pencil hardness. Thus present work demonstrates Gossypium arboreum plant oil and dicarboxylic acids as newer eco-friendly raw materials for PU coatings and compared with standard petro based polyols.