Bio-based Polyols Research Articles

Chemically recyclable polyurethanes based on bio-renewable γ-butyrolactone: From thermoplastics to elastomers

The large-scale production and disposal of petroleum-derived commercial polyurethane materials have caused severe enviroment problem. Although the bio-based or biodegradable polyols have attracted considerable attention to prepare sustainable polyurethanes, the chemical recycling of polyurethanes via controlled bond scission reactions to recover monomer or value-added building blocks still remains as a big challenge. In this contribution, we address this challenge by preparation of biodegradable and chemically recyclable polyurethanes using bio-based telechelic hydroxyl terminated poly(γ-butyrolactone) (PγBL) diols as precursors. The obtained polyurethanes exhibited thermoplastic or elatomeric properties depending on the molar mass of used PγBL diol precursors. The thermal, mechanical and hydrolytic properties of PγBL based polyurethanes are systematically investigated. Remarkably, the polyurethanes are capable of chemical recycling to recover γBL with high purity in an almost quantitative yield by a simple vacuum distillation procedure.

The Effect of Crosslink Density on the Physical and Mechanical Properties of Bio‐Based Polyurethane Foams

AbstractRigid low‐density closed‐cell polyurethane foams with different crosslink densities have been produced using biobased polyols derived from tall oil. Mechanical and dilatometric tests reveal that the transverse stiffness and tensile strength of the foams increased with growing crosslink density both at the room and cryogenic temperatures, while the coefficient of linear thermal expansion exhibited an opposite trend. Cryogenic safety factors, estimated based on the foam properties obtained, reveal no consistent trend with changing crosslink density of the polyurethane polymer.

Spent coffee ground oil as a valuable source of epoxides and epoxidation derivatives: Quantitation and characterization using low-field NMR

Coffee waste, commonly referred to as spent coffee grounds (SCG), is currently discarded and has a negative impact on the environment. However, SCG are rich in valuable ingredients including 15–20% oil, which has a profile comparable to the vegetable oils used in the production of epoxides, biobased polyols, and polymers. Our first objective was to evaluate the efficiency of three different methods, namely Soxhlet, pressurized fluid extraction, and supercritical CO2 (scCO2) on SCG oil extraction. Additionally, we aimed to test the potential of low-field (LF) NMR to analyze SCG oil and monitor the formation of epoxides and biobased polyols. Finally, we evaluated epoxidized SCG oil as a plasticizer for improving the properties of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) bioplastic. Overall, SCG showed a promising potential as a source of biopolymer precursors, while LF NMR can be an efficient and economic tool for oil evaluation and reaction monitoring.

Toughness Improvement of Epoxy Composites Using a Kind of Environment-Friendly Bio-Based Polyester Polyol

Epoxy resin (EP) is a thermosetting resin with prominent performances and wide applications. However, the inherent brittleness limits its development in the engineering materials area. A liquid bio-based polyester polyol (LLP) with flexible long chains was synthesized in this study by melt polycondensation of corn straw lignin. After being compounded with EP (LLP/EP), the mechanical property, micromorphology and thermal behavior of the composite were evaluated. The experimental result indicated that the fracture brittleness of EP composite was decreased by importing the LLP. The bending and impact strength were up to 113.67 MPa and 51.29 kJ/m2 for 10%-LLP/EP, which were 5.25% and 27% higher than those of unmodified EP. The results of this work build new avenues for the efficient utilization of lignin and the development of low-cost, high-performance and well environmentally adaptable EP composite by renewable resources.Graphical Abstract

UV resistance, anticorrosion and high toughness bio-based waterborne polyurethane enabled by a Sorbitan monooleate

Sorbitan monooleate (SP) is considered to be a promising renewable polyol with unique molecular structures for the development and design of bio-based waterborne polyurethane (WPU) with versatility and excellent mechanical properties. In this study, SP was used as a bio-based polyol in combination with castor oil to design and prepare a series of bio-based WPU with anti-ultraviolet, corrosion resistance and excellent mechanical properties. The influence of the hydroxyl ratios between SP and castor oil on the chemical structures and properties of bio-based WPU dispersions and the resulting WPU films was systematically studied. The resulting WPU films exhibited excellent mechanical properties and thermo-physical properties due to the presence of large amounts of hydrogen bonding and rigid furan ring, and high crosslinking densities. The bio-based WPU films could lift heavy objects 10,330 times their own weight. The resulting WPU coatings could resist ultraviolet radiation in the region (200–400 nm) and exhibited excellent UV resistance in outdoor practical application tests. In addition, these WPU coatings demonstrated effectively anticorrosive effect in which the anticorrosion period of the coating on the tinplate outdoors could be as long as 6 months in terms of corrosion potential, corrosion current and corrosion protection efficiency of the coating reached −0.507 V, 2.92 × 10−6 A, and 95.39%, respectively. This study provides a new and simple method for preparing bio-based WPU with excellent anti-ultraviolet performance, anti-corrosion performance and excellent mechanical properties.

Synthesis of Thermoplastic Polyurethanes Containing Bio-Based Polyester Polyol and Their Fiber Property.

Among the starting materials of thermoplastic polyurethanes (TPUs), it was confirmed that succinic acid-based polyester biopolyols having different molecular weights (Mn = 1000, 2000, and 4000) affect the physicochemical properties of the final polymer significantly. Bio-TPUs synthesized through a solvent-free one-shot polymerization process were synthesized with a polyester polyol, 1,4 butanediol (BDO), and 4,4′-methylene diphenyl diisocyanate (MDI) in a molar ratio of 1:1:2. As a control group, one typical petroleum-based TPU was synthesized and characterized along with other bio-based TPUs. Representative petroleum-based and bio-based TPUs synthesized were manufactured as monofilaments with a diameter of about 0.2 mm through an extrusion process with different draw ratios (4, 5, and 6 times). The molecular weight and structural properties of the TPUs were characterized by GPC and FT-IR analysis and thermal characterization by DSC and TGA analysis. Petroleum-based TPU and bio-based TPU having the same molecular weight soft segment (SS) tended to have similar molecular weight and hard segment (HS) content. TPUs with high HS content had excellent thermal stability, enabling stable extrusion of TPUs. In addition, it was confirmed that the bio-based TPU fibers produced in this way had a tensile strength corresponding to the physical properties of petroleum-based TPU fibers and an excellent elastic recovery rate of almost 100 %. These results indicate the application potential of bio-TPU.

Sustainable Rigid Polyurethane Foam from Partial Substitution with Bio-Based Polyol

Sustainable Rigid Polyurethane Foam from Partial Substitution with Bio-Based Polyol

Bio-polyols based waterborne polyurethane coatings reinforced with chitosan-modified ZnO nanoparticles

The development of environmentally friendly waterborne polyurethane (WPU) coatings from bio-based polyols has received much attention due to increasing environmental concern and the depletion of petroleum resources. In this study, the WPU coatings derived from castor oil and soy polyol were modified by chain extender [bis(2-hydroxyethyl)amino]-methyl-phosphonic acid dimethyl ester. The effect of chitosan-modified ZnO (CS-ZnO) nanoparticles content on the properties of WPU/CS-ZnO coatings and their films were systematically investigated. The results indicated that WPU/CS-ZnO coatings displayed excellent storage stability and the particle sizes firstly decreased and then increased with CS-ZnO loading. CS-ZnO could improve tensile strength and Young's modulus but reduce the optical transparency of WPU/CS-ZnO films. CS-ZnO has a prominent reinforcement effect on the WPU/CS-ZnO matrix. With the addition of 2 wt% CS-ZnO, the tensile strength and Young's modulus of the WPU/CS-ZnO2 film reached 13.4 and 112.1 MPa, 1.68 and 2.6 times over neat WPU film, respectively. TGA results showed that the thermal stability of WPU/CS-ZnO films improved with increased CS-ZnO content. Furthermore, the WPU/CS-ZnO films' wettability decreased with the introduction of CS-ZnO. This work provides a simple and efficient strategy for preparing environmentally friendly bio-based WPU coatings, which are promising for application in the surface coating industry.

Cover Feature: Perspectives for the Upgrading of Bio‐Based Vicinal Diols within the Developing European Bioeconomy (ChemSusChem 5/2022)

The Cover Feature shows sourcing of important industrial building blocks from bio-based polyols. More information can be found in the Review by C. Muzyka and J.-C. M. Monbaliu.

Antimicrobial Lignin-Based Polyurethane/Ag Composite Foams for Improving Wound Healing.

Antimicrobial materials are an urgent need for modern wound care in the clinic. Although traditional polyurethane foams have proven to be clinically valuable for wound treatment, their petroleum-originated preparation and bioinert nature have restricted their efficacy in biomedical applications. Here, we propose a simple one-step foaming method to prepare lignin-based polyurethane foams (LPUFs) in which fully biobased polyether polyols partially replace traditional petroleum-based raw materials. The trace amount of phenolic hydroxyl groups (about 4 mmol) in liquefied lignin acts as a direct reducing agent and capping agent to silver ions (less than 0.3 mmol), in situ forming silver nanoparticles (Ag NPs) within the LPUF skeleton. This newly proposed lignin polyurethane/Ag composite foam (named as Ag NP-LPUF) shows improved mechanical, thermal, and antibacterial properties. It is worth mentioning that the Ag NP-LPUF exhibits more than 99% antibacterial rate against Escherichia coli within 1 h and Staphylococcus aureus within 4 h. Evaluations in mice indicate that the antimicrobial composite foams can effectively promote wound healing of full-thickness skin defects. As a proof of concept, this antibacterial and biodegradable foam exhibits significant potential for clinical translation in wound care dressings.

Instant catapult steam explosion pretreatment of wheat straw liquefied polyols to prolong the slow-release longevity of bio-based polyurethane-coated fertilizers

The direct liquefaction product of crop straws for bio-based polyurethane-coated fertilizers (BPCFs) has low hydroxyl values and complicated composition types, resulting in poor crosslinking degree, high hydrophilicity, and short release longevity. This study created an efficient physicochemical instant catapult steam explosion pretreatment wheat straw (SEWS) technology to remove small molecular hemicellulose and difficult-to-film-forming ions, improve straw liquefied polyol quality, and extend the release longevity of BPCFs. The results revealed that the steam explosion process (2.0 MPa for 5 min) broken the straw cell wall, hydrolyzed hemicellulose, and significantly decreased the difficult-to-film-forming ions (K+, Ca2+, and Mg2+). The SEWS liquefied residue rate dropped 38.1% to 5.5%, while the hydroxyl value increased 36.51% to 125.32 mg KOH g−1. The liquid polyol of SEWS and diphenyl-methane-diisocyanate formed a tightly cross-linked, homogenous bio-based membrane with no visible holes. Under the condition of 3% weight of the core fertilizer, the release longevity of SEWS increased from 14 to 32 days. The use of instant catapult steam explosion technology for high-efficiency pretreatment of biomass materials is conducive to improving the quality of bio-based polyols and the industrial production of bio-based controlled-release fertilizers. Furthermore, the pretreatment technology promotes the use of biomass for sustainable agriculture.

Bio-Based 2K PU Coating for Durable Textile Applications

Polyurethane (PU) coatings are often applied on high added value technical textiles. To date, most PU textile coatings are solvent based or water based. Recent advances are made in applying high solid and two-component (2K) PU on textiles. Currently, polymers made from renewable raw materials are experiencing a renaissance, owing to the trend to reduce CO2 emissions and switch to CO2-neutral renewable products. There is also the tendency towards the “bio, eco, natural” consciousness-awakening of the end consumer and the market-driven question to implement renewable materials. However, the application of bio-based coatings on textiles is limited. In this regard, the present study is conducted to develop bio-based 2K PU coating specifically designed for waterproof textiles. A 2K PU coating formulation, composed of bio-based polyol and bio-based isocyanate Desmodur Eco N7300, was made and directly applied on a polyester fabric prior to thermal curing in an oven. The coating was characterized via Fourier-transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The coatings were not thermoplastic and had a glass transition temperature of approximately 50 °C. Since a bio-based pentamethylene diisocyanate trimer (PDI-trimer), Desmodur Eco N7300 was used as an isocyanate source and not a diisocyanate derivative, and the resulting bio-based 2K coating was a thermoset instead of a thermoplastic. The effect of the additives and content of isocyanate on the elongation and stress at break was studied by performing tensile tests (ISO 13934-1) on 50 µm 2K PU films and comparing the obtained values. The performance of the coating was studied by evaluating the resistance to hydrostatic pressure initially and after washing, the Q-panel Laboratory UltraViolet (QUV) aging and the hydrolysis test. The developed bio-based 2K PU coating had excellent hydrostatic pressure, QUV aging resistance, hydrolysis resistance and wash fastness at 60 °C.

Thiol-Ene Coupling of High Oleic Sunflower Oil towards Application in the Modification of Flexible Polyurethane Foams.

High oleic sunflower oil-based polyol was obtained by thiol-ene coupling and applied in the preparation of flexible polyurethane foams. The photochemically initiated thiol-ene click reaction was carried out under UV irradiation using 2-mercaptoethanol. Bio-based polyol with hydroxyl value of 201.4 mg KOH/g was used as 30 wt% substituent of petrochemical polyether polyol in the formulations of flexible foams. Both reference foams, as well as foams modified with bio-based polyol, were formulated to have various isocyanate indices (0.85, 0.95, 1.05). Flexible foams were compared in terms of their thermomechanical properties and analyzed using FT-IR and SEM microscopy. Modification with bio-based polyol resulted in foams with superior compression properties, higher support factor, and lower resilience than reference foams. TGA and FT-IR curves confirmed the presence of urethane/urea and ether linkages in the polyurethane matrix. Moreover, double glass transition temperature corresponding to soft and hard segments of polyurethane was observed by DSC proving the phase-separated morphology.

Sustainable Reactive Polyurethane Hot Melt Adhesives Based on Vegetable Polyols for Footwear Industry.

The aim of this work is to develop sustainable reactive polyurethane hot melt adhesives (HMPUR) for footwear applications based on biobased polyols as renewable resources, where ma-croglycol mixtures of polyadipate of 1,4-butanediol, polypropylene and different biobased polyols were employed and further reacted with 4-4′-diphenylmethane diisocyanate. The different reactive polyurethane hot melt adhesives obtained were characterized with different experimental techniques, such as Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), softening temperature and melting viscosity. Finally, their adhesion properties were measured from T-peel tests on leather/HMPUR adhesives/SBR rubber joints in order to establish the viability of the used biobased polyols and the amount of these polyols that could be added to reactive polyurethane hot melt adhesives satisfactorily to meet the quality requirements of footwear joints. All biobased polyols and percentages added to the polyurethane adhesive formulations successfully met the quality requirements of footwear, being comparable to traditional adhesives currently used in footwear joints in terms of final strength. Therefore, these new sustainable polyurethane adhesives can be considered as suitable and sustainable alternatives to the adhesives commonly used in footwear joints.

Synthesis of vegetable oil-based hyperbranched polyol via thiol-yne click reaction and their application in polyurethane

A novel bio-based hyperbranched polyol (HBP) with high functionality was prepared from grapeseed oil (GSO) through the following sequential steps: i) epoxidation, ii) propargylation and iii) thiol-yne click reaction. Structural analysis confirmed that the GSO-based HBP was synthesized successfully; and the hydroxyl value of the synthesized HBP was 612 mg KOH/g, which is close to that of commercialized HBP. Furthermore, the prepared HBP was employed as a crosslinker to fabricate bio polyurethane (PU) films via a two-step prepolymer polymerization. The successful synthesis of hyperbranched PUs was confirmed by Fourier transform infrared analysis. Moreover, according to the results of X-ray diffraction analysis, the crystallinity of the prepared hyperbranched PUs decreased because the crosslinked networks hindered the formation of crystalline structures. Based on the mechanical property analysis, it was confirmed that the tensile strength and elongation of PU using HBP reached 27 MPa and 2315%, respectively. From these results, it can be confirmed that the tensile strength and tensile elongation of the PUs significantly increased upon the introduction of a crosslinker with a hyperbranched structure.

Enhanced Water Resistance Performance of Castor Oil—Based Waterborne Polyurethane Modified by Methoxysilane Coupling Agents via Thiol-Ene Photo Click Reaction

Nowadays, waterborne polyurethanes (WPUs) prepared from renewable resources has attracted more and more attention. However, due to its structure, the prepared films easily swells in water and greatly affects the application range of WPUs. Therefore, solving the problem of water resistance is a way to improve the application range of WPUs. In this study, a series of WPU dispersions were prepared using castor oil as the bio-based polyol. Besides, the thiol-ene photo click reaction was carried out on the WPU films for silane modification. The effect of the silane modification on the chemical structures of the WPU dispersions and the properties of the WPU films was investigated and discussed. The results revealed that the WPU dispersions had a smaller particle size and potential, showing excellent stability. In addition, the modified WPU films showed highly water resistance which 72 h water absorption could be reduced to 1.94% and the contact angle was up to 99.34°. Moreover, the modified WPU films also exhibited excellent solvent resistance (in acid and salt solution) and thermal stability. This study can provide a new way to improve the water-resistance, hydrophobicity, and thermal stability of bio-based waterborne polyurethane for potential application in painting, adhesives and inks.

A study on coconut fatty acid diethanolamide-based polyurethane foams.

The possibility of using coconut fatty acid diethanolamide, a derivate from coconut oil as a bio-based polyol for the synthesis of polyurethane foam was explored. The intrinsic tertiary amine moiety in this polyol (p-CFAD) endowed an auto-catalytic effect in the synthesis process of polyurethane foams, combined with a shorter cream and gelation time compared to the fossil-based polyol 3152. H-nuclear magnetic resonance (1H-NMR) and Fourier transform infrared spectrometry (FTIR) were conducted to characterize the chemical structural features of the p-CFAD, and rheology measurement showed the shear-thinning behavior due to the branched structure. A thermal conductivity comparable to the commercial rigid polyurethane foam was achieved when 40wt% fossil-based polyol 3152 was substituted with the bio-based p-CFAD. With the increased content of the p-CFAD, a transition of the physical properties from rigid PU foam to soft PU foam was observed. Scanning electron microscopy (SEM) revealed the occurrence of the interconnected pores on the cell walls with the increase of the added p-CFAD, implying the possibility of regulating the cellular structure and foam properties via the incorporation of the p-CFAD. Results showed the feasibility of using p-CFAD as a potential polyol in the development of bio-based polyurethane foams with high performance.

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.

A novel polyfunctional polyurethane acrylate prepolymer derived from bio-based polyols for UV-curable coatings applications

In recent decades, the sustainability, availability and low toxicity of biomass polyols have attracted more and more attention. Biomass polyols were used to prepare polyfunctional polyurethane acrylates, which can effectively improve the green performance of UV-curable coatings. Herein, a multifunctional polyurethane acrylate containing a variety of biomass was synthesized and characterized. Firstly, itaconic acid (IA), ricinoleic acid (RA) and oleic acid (OA) reacted with glycidyl methacrylate (GMA) respectively to obtain itaconic acid acrylate (IAG), ricinoleic acid acrylate (RAG) and oleic acid acrylate (OAG). Determination of the synthesis of IAG, RAG and OAG was conducted by proton nuclear magnetic resonance (1H NMR) and Fourier transform infrared spectroscopy (FTIR). Then IAG, RAG, OAG and castor oil (CO) were mixed and reacted with isophorone diisocyanate (IPDI) to prepare polyurethane acrylate. The effects of IAG, RAG, OAG and CO on the thermal and mechanical properties of polymers were studied. The results showed that when the content of IAG was increased, the double bond conversion rate, the glass transition temperature, tensile strength, Young's modulus and gel content of polyurethane increased significantly. In addition, by adjusting the contents of IAG, RAG, OAG and CO, the thermal stability of polymers also showed regular changes. Among them, the thermal stability of polymers increased most with the increase of IAG content, followed by RAG, OAG and CO.

Synthesis and characterization of biopolyols through biomass liquefaction of wood shavings and their application in the preparation of polyurethane wood composites

The sustainability of production systems in wood processing, wood industry, and wooden waste disposal is an important issue for European industry and society. Proper development of products based on renewable wood resources gives an opportunity to provide materials with long-term environmental, social, and economic sustainability. This study aims to establish a new way of forestry and agricultural waste materials utilization by synthesis of bio-based polyols and manufacturing of polyurethane wood composites (PU-WC). The first part of this paper describes the liquefaction of wood shavings at a temperature of 150 °C for 6 h in three different solvents—glycerol, poly (ethylene glycol) and their mixture in a 1:1 ratio. The second part deals with the synthesis of polyurethane (PU) resins containing 90% of biopolyol. Eight sets of materials with different NCO:OH ratios were obtained in a one-step method using a hydraulic press. These materials were characterized, and the material with the most promising properties was selected for polyurethane wood composites production. Composites with 40%, 50%, 60%, and 70% of wood shavings were obtained. The addition of filler caused an increase in flexural strength, Young`s modulus, hardness, and impact strength. Scanning electron microscopy (SEM) showed good adhesion between the polymer and the filler. The optimum filler content is between 50 and 60% by weight of the composite. The presented study provides a significant step toward a greener alternative for materials produced mainly from non-renewable resources.