Bio-based Non-isocyanate Polyurethane Research Articles

High-Performance Bio-Based Non-Isocyanate Polyurethane Adhesive: A Solvent and Catalyst-Free Synthesis Approach

High-Performance Bio-Based Non-Isocyanate Polyurethane Adhesive: A Solvent and Catalyst-Free Synthesis Approach

Self-blowing, hybrid non-isocyanate polyurethane foams produced at room temperature

Self-blowing polyurethane foams are essential for several everyday applications, yet their traditional production involves fossil-derived products and hazardous isocyanate compounds. Thus, research into isocyanate-free polyurethane foams is receiving considerable attention. However, current approaches often rely on external blowing agents, and/or high temperatures with long polymerization times. This research presents a rapid, self-blowing, partially bio-based non-isocyanate polyurethane (NIPU) foams at room temperature, specifically poly(hydroxy-thio-urethane), with both rigid and flexible configurations. The method involves the partial conversion of an epoxy resin to an oligomer mixture composed of 85% bio-cyclic carbonate and 15% of non-converted epoxide. This oligomer undergoes a fast process, through reactions between the epoxy groups and the reactive components, that is then followed by simultaneous aminolysis and decarboxylation reactions, arising from the interaction of an amine and cyclic carbonate. An in-situ blowing agent (CO2) is generated from the interaction between thiols and cyclic carbonate. The glass transition temperature is modulated by the thiol/amine content in rigid foams and by the addition of aliphatic long chains in flexible foams. With almost 30% renewable carbon content, these foams provide a sustainable alternative to traditional isocyanate-based pathways. The resulting porous materials possessed densities between 0.158 and 0.201 g/cm3. Finally, the foams can be transformed into films, enhancing recyclability and sustainability at the end of their lifecycle. Thus, this development has the potential to facilitate the production of eco-friendly, recyclable polyurethane foams.

A review on vegetable oil-based non isocyanate polyurethane: towards a greener and sustainable production route.

The transition from conventional polyurethane (PU) to non isocyanate polyurethane (NIPU) is driven mainly by safety concerns, environmental considerations, and sustainability issues associated with the current PU technology. NIPU has emerged as a promising alternative, addressing limitations related to traditional PU production. There has been increasing interest in bio-based NIPU aligning with the aspiration for green materials and processes. One important biomass resource for the development of bio-based NIPU is vegetable oil, an abundant, renewable, and relatively low cost feedstock. As such, this review aims to provide insight into the progression of NIPU derived from vegetable oils. This article highlights the synthetic and green approach to NIPU production, emphasizing the method involving the polyaddition reaction of cyclic carbonates and amines. The review includes case studies on vegetable oil-based NIPU and perspectives on their properties. Further, discussions on the potential applications and commercial importance of PU and NIPU are included. Finally, we offer perspectives on possible research directions and the future prospects of NIPU, contributing to the ongoing evolution of PU technology.

Preparation and fire resistance modification on tannin-based non-isocyanate polyurethane (NIPU) rigid foams

Non-isocyanate polyurethane (NIPU) as a new type of polyurethane material has become a hot research topic in the polyurethane industry due to its no utilization of toxic isocyanates during the synthesis process. And the developing on recyclable biomass materials has also much attention in the industrial sector, hence the preparation and application of bio-based NIPU has also become a very meaningful study work. So, in this paper, tannin as a biomass material was used to synthesize tannin based non-isocyanate polyurethanes (TNIPU) resin, and then successfully prepared a self-blowing TNIPU foam at room temperature by using formic acid as initiator and glutaraldehyde as cross-linking agent. The compressive strength of this foam as high as 0.8 MPa, which is an excellent compressive performance. Meanwhile it will return to the state before compression when removing the pressure. This indicating that the foam has good toughness. In addition, formic acid can react with the amino groups in TNIPU to form amide substances, and generated enough heat to initiate the foaming process. Glutaraldehyde, as a crosslinking agent, reacts with the amino group in TNIPU to form a network structure system. By scanning electron microscope (SEM) observation of the cell shapes, it can be seen that the foam cells were uniform in size and shape, and the cell pores showed open and closed cells. The limiting oxygen index (LOI) tested value of this TNIPU foam is 24.45 % without any flame retardant added, but compared to the LOI value of polyurethane foam (17 %–19 %), TNIPU foam reveal a better fire resistance. It has a wider application prospect.

Bio-based non-isocyanate polyurethane(urea) waterborne dispersions for water resistant textile coatings

Currently, the resins used in industrial polyurethane coatings are made from petro-based polyols and isocyanate building blocks. In traditional coating formulations, polyurethane resins can be solubilized in solvents for their application on substrates, thus releasing possibly volatile organic compounds (VOCs) upon drying. To circumvent these issues, polyurethanes synthesized from non-isocyanate and bio-based building blocks are receiving more interest. However, only few references describe the development of waterborne non-isocyanate dispersions with a direct application.In this study, non-isocyanate polyurethane(urea)s of very high bio-based contents (>80 wt%) and having controlled amount of reactive hydroxyl ends were synthesized via transcarbamoylation. The obtained resins were used as cationic waterborne dispersions in a sustainable coating system. The influence of the functionality and hydrophobicity of the neutralization agent used to protonate the non-isocyanate polyurethane(urea) backbones, as well as the dicarbamate monomer structures were assessed. It was found that the combination of monofunctional and hydrophilic dl-lactic acid neutralization agent (for electrostatic repulsion) led to stable dispersions with better properties (particle size and zeta potential) than the commercial waterborne polyurethane dispersion reference. Those dispersions were cross-linked through their reactive hydroxyl end groups with tetramethylol acetylene diurea into freestanding films and adhesive layers for textile coatings. The freestanding films exhibited high cross-linking efficiency (gel content >90 %), low water uptake (down to 2 %) and high water and methyl ethyl ketone (MEK) resistance (≥200 rubs) as well as good mechanical properties (Young's modulus between 1.5 MPa and 3.1 MPa and elongation at break up to 300 %) to resist the deformation of the fabrics when applied on them. Finally, when used as an adhesive layer on textiles, good resistance to hydrolysis and heat aging were ensured by the coating system, thus potentially replacing isocyanate based adhesive layers.

Bio-based non-isocyanate polyurethane with closed-loop recyclability and its potential application

Developing bio-based non-isocyanate polyurethanes (NIPUs) to replace petroleum-based conventional polyurethanes (PUs) plays an essential role in green production and relieving energy pressure. However, the synthesis of NIPUs using renewable resources, and recycling after reaching service time remain to be solved. Herein, a novel structural cross-linked NIPU network with closed-loop recyclability was prepared, which is derived from abundant lignin-derived and carbon dioxide (CO2) resources. The obtained NIPUs with dual dynamic covalent bonds exhibit relatively low activation energy (70.34 kJ/mol) and remarkable remolding efficiency (∼100 %). Importantly, spiro bi-acetal structures in polymer chains impart closed-loop recyclability to the obtained NIPUs. The results showed that they can be degraded at room temperature followed by regeneration with nearly full recovery of properties. Moreover, bio-based NIPUs are used as supporting materials to produce phase change materials (PCMs) for the first time, and the latent heat reaches 128.2 J/g. The material has favorable form stability and is leakage-proof owing to ZnⅡ-carboxylates coordination interactions and stable cross-linked networks. This study demonstrates a method for the synthesis of closed-loop recyclable NIPUs from renewable resources, enriching synthetic diversity while providing an initial exploration of its potential as PCMs.

Latest Advancements in the Development of High-Performance Lignin- and Tannin-Based Non-Isocyanate Polyurethane Adhesive for Wood Composites.

The depletion of natural resources and increasing environmental apprehension regarding the reduction of harmful isocyanates employed in manufacturing polyurethanes (PUs) have generated significant attention from both industrial and academic sectors. This attention is focused on advancing bio-based non-isocyanate polyurethane (NIPU) resins as viable and sustainable substitutes, possessing satisfactory properties. This review presents a comprehensive analysis of the progress made in developing bio-based NIPU polymers for wood adhesive applications. The main aim of this paper is to conduct a comprehensive analysis of the latest advancements in the production of high-performance bio-based NIPU resins derived from lignin and tannin for wood composites. A comprehensive evaluation was conducted on scholarly publications retrieved from the Scopus database, encompassing the period from January 2010 to April 2023. In NIPU adhesive manufacturing, the exploration of substitute materials for isocyanates is imperative, due to their inherent toxicity, high cost, and limited availability. The process of demethylation and carbonation of lignin and tannin has the potential to produce polyphenolic compounds that possess hydroxyl and carbonyl functional groups. Bio-based NIPUs can be synthesized through the reaction involving diamine molecules. Previous studies have provided evidence indicating that NIPUs derived from lignin and tannin exhibit enhanced mechanical properties, decreased curing temperatures and shortened pressing durations, and are devoid of isocyanates. The characterization of NIPU adhesives based on lignin and tannin was conducted using various analytical techniques, including Fourier-transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), matrix-assisted laser desorption/ionization with time-of-flight (MALDI-TOF) mass spectrometry, and gel permeation chromatography (GPC). The adhesive performance of tannin-based NIPU resins was shown to be superior to that of lignin-based NIPUs. This paper elucidates the potential of lignin and tannin as alternate sources for polyols in the manufacturing of NIPUs, specifically for their application as wood adhesives.

Chemically Recyclable Biobased Non-Isocyanate Polyurethane Networks from CO2 -Derived Six-membered Cyclic Carbonates.

Non-isocyanate polyurethanes (NIPUs) are widely studied as sustainability potential, because they can be prepared without using toxic isocyanates in the synthesis process. The aminolysis of cyclic carbonate to form NIPUs is a promising route. In this work, a series of NIPUs is prepared from renewable bis(6-membered cyclic carbonates) (iEbcc) and amines. The resulting NIPUs possess excellent mechanical properties and thermal stability. The NIPUs can be remolded via transcarbamoylation reactions, and iEbcc-TAEA-10 (the molar ratio of tris(2-aminoethyl)amine in amines is 10%) still get a recovery ratio of 90% in tensile stress after three cycles of remolding. In addition, the obtained materials can be chemically degraded into bi(1,3-diol) precursors with high purity (>99%) and yield (>90%) through alcoholysis. Meanwhile, the degraded products can be used to regenerate NIPUs with similar structures and properties as the original samples. The synthetic strategy, isocyanate-free and employing isoeugenol and carbon dioxide (CO2 ) as building blocks, makes this approach an attractive pathway to NIPU networks taking a step toward a circular economy.

Preparation and characterization of non-isocyanate polyurethane resins derived from tannin of Acacia mangium bark for the modification of ramie fibers

Abstract The purpose of this research was to create bio-based non-isocyanate polyurethane (Bio-NIPU) resins derived from the tannin of Acacia mangium Willd. bark for the impregnation of ramie fibres (Boehmeria nivea L.) and to investigate the properties of impregnated fibres. Tannin was extracted from the bark of A. mangium using hot water. Tannin-bio-NIPU resin was created using dimethyl carbonate and hexamine. Based on the findings, it is possible to conclude that tannin extract from the bark of Acacia mangium can be used effectively as a renewable alternative to toxic polyols in the development of tannin-Bio-NIPU resins. FTIR spectroscopy was used to confirm the urethane bond formed on the tannin-Bio-NIPU resins. Thermal and mechanical analysis were used to investigate the properties of tannin-Bio-NIPU resins and ramie fibres before and after impregnation. This study shows that the impregnation time of ramie fiber using tannin-Bio-NIPU resins is 30 minutes. The reaction between tannin-Bio-NIPU resins with ramie fiber forms the C=O urethane group as confirmed by FTIR Spectroscopy. The characterization results show that tannin-Bio-NIPU resins has ability to modify ramie fiber via impregnation in order to increase its mechanical properties, thus enhancing its potential for wider industrial application as a functional material.

High-Strength, Self-Healing, Recyclable, and Catalyst-Free Bio-Based Non-Isocyanate Polyurethane

Non-isocyanate polyurethanes (NIPUs) from renewable resources have attracted wide attention because of their remarkable benefits to sustainable development and green production. In this work, a strong, self-healing, and catalyst-free NIPU (ECMP) was prepared based on the hyperbranched bio-based cyclic carbonate (Ec-MTDA) synthesized through catalytic carbonization of 1,8-menthane diamine (MTDA) and CO2. The hyperbranched and rigid structures of ECMP enable improved mechanical properties that a high tensile strength of up to 34.9 MPa can be achieved. Benefiting from the dynamic transesterification reaction between the carbamate and hydroxyl groups, ECMP presents favorable self-healing, reprocessing properties, and shape memory. Notably, 91% of the original tensile strength can be recovered after self-healing behavior. In addition, abundant polar groups provide excellent adhesion properties for ECMP with a high shear strength of 7.09 MPa. This study provides a promising strategy for the design of bio-based NIPUs, which broadens their applications in printing, furniture, packaging, and other industries.

Studies on Biobased Non-Isocyanate Polyurethane Coatings with Potential Corrosion Resistance

This work deals with the development of non-isocyanate polyurethane (NIPU) composites with an aniline oligomer, viz., tetraniline (TANI) for corrosion-resistant coatings. Firstly, epoxidizedsoyabean oil was converted to carbonated oil by inserting CO2 under high temperature and pressure into the epoxy ring. Then, varying weights of oligoaniline—0.5, 1, 2 and 4 wt % (based on the weight of CSBO)—were added to CSBO and cured with tetraethylenepentamine (TEPA, 25 wt % based on CSBO) at 80 °C for 12–15 h. The effects of oligomer loading on the thermal, mechanical and surface wetting properties of the free standing films were studied. The ATR-FTIR spectra of the films exhibited peaks corresponding to the bis-carbamate linkages, confirming the formation of urethane linkages. TGA analysis showed that the addition of oligoaniline did not alter the initial degradation temperature much; however, the residue increased with increasing loading of tetraniline. Both tensile strength and elongation (at break) increased with increasing oligoaniline content. While the glass transition temperature of the films was observed at approximately room temperature, i.e., 20–30 °C, for all the compositions, the contact angles of the composites were found to be less than that of the bare NIPU films. However, all the compositions were hydrophobic, exhibiting contact angles in the 98–110° range. SEM analysis of the cross-sections of the films confirmed the uniform distribution of tetraniline particles and surface morphology showed that the roughness increased with the loading of tetraniline from 0.5 to 4%. MS panels coated with NIPU exhibited good barrier properties and as loading of TANI increased, the rate of corrosion decreased. Salt spray tests indicated that oligoaniline improved the adhesion of the coating to MS and corrosion resistance compared to the neat NIPU coating.

Design of biobased non-isocyanate polyurethane (NIPU) foams blown with water and/or ethanol

Design of biobased non-isocyanate polyurethane (NIPU) foams blown with water and/or ethanol

Preparation of flexible biobased non-isocyanate polyurethane (NIPU) foams using the transurethanization approach

A new process for the preparation of non-isocyanate polyurethane (NIPU) flexible foams has been implemented. Biobased amino-telechelic NIPU oligomers were prepared by an organo-catalyzed transurethane polycondensation reaction of fatty biscarbamates with fatty diols and diamines. The obtained oligomers were reacted with a biobased multi-epoxide molecule as crosslinking agent, in the presence of a poly(hydromethylsiloxane) or its copolymer as foaming agent and surfactant. The crosslinking and foaming reactions were monitored by rheometric, volumetric and FTIR studies. The foams can be obtained in <30 min at 100 °C or in 14.5 h at room temperature. The prepared foams displayed cell diameters in the range of 210 to 430 μm associated with densities in the range of 130 to 400 kg/m3. They also exhibited thermal stabilities above 300 °C, as well as a soft character attested by negative Tg values ranging from −10 to −28 °C, and low values of the Young modulus varying from 1.0 × 104 Pa to 6.3 × 104 Pa. The recovery time, hysteresis loss and the firmness of these foams were found to be dependent on their chemical structures.

Novel Biobased Non-Isocyanate Polyurethanes from Microbially Produced 7,10-Dihydroxy-8(E)-Octadecenoic Acid for Potential Packaging and Coating Applications

In this study, a green and sustainable strategy was opted for the synthesis of a novel biobased non-isocyanate polyurethane (NIPU) or polyhydroxyurethane (PHU). NIPU or PHU was synthesized from microbially converted hydroxy fatty acid-based cyclic carbonate and diamine cross-linker. Initially, oleic acid was biotransformed into 7,10-dihydroxy-8(E)-octadecenoic acid (DOD) using Pseudomonas aeruginosa. The cell-free approach was chosen for DOD production due to its high yield and productivity. Afterward, DOD was modified into DOD-based tricyclic carbonate by a two-step method. The prepared monomeric material was characterized using Fourier transform infrared (FTIR) spectroscopy, 1H nuclear magnetic resonance (1H NMR), and 13C NMR analyses. A series of DOD-based PHUs (DOD PHUs) were synthesized with different amine contents, and their structures were studied by FTIR and 1H NMR analyses. The morphological, mechanical, and thermal properties of DOD PHU were further analyzed. The tensile strength and elongation at break of the prepared DOD PHU were in the range of 2–6 MPa and 39–76%, respectively. The glass transition temperature of the material was in the range of 4–27 °C. Thermogravimetric analysis exhibited that thermal stability increases with the increase in amine content. The gel content was in the range of 73–100%, suggesting that the polymers are highly cross-linked. In addition, the synthesized DOD PHU displayed excellent ultraviolet and water resistance properties. The green synthesized DOD PHU depicts suitability for a wide range of applications, particularly in the coating and packaging industries.

Study of the carbamate/aldehyde reaction, a new pathway towards NIPU materials

An innovative alternative to the synthesis of non-isocyanate polyurethanes (NIPUs) thermoset materials was thoroughly investigated. This pathway, involving the reaction between primary carbamate functions and aldehyde functions, was studied using model reactions between ethyl carbamate and different aldehydes that lead to the highlights of the key parameters as well as the first reported proposed mechanism for this reaction. In a second time, polycarbamates synthesized from two different polyols were synthesized via transcarbamoylation before participating in a polycondensation reaction with different monoaldehydes. First a linear NIPU oligomer was synthesized using a dicarbamate derived from ethylene glycol and benzaldehyde. This product was analysed by NMR spectroscopy and MALDI-TOF mass spectrometry. This oligomer exhibited low molar masses attributed to many secondary termination reactions, mainly due to the presence of acetic anhydride used as solvent in the reaction. Cross-linked NIPU materials were then synthesized without solvent, from the reaction between a tricarbamate derived from trimethylol propane and vanillin, a biobased monoaldehyde, for the first time. The process parameters for the synthesis of these materials were optimized to obtain biobased NIPU thermosetting networks with gel fraction (GF) in dimethylsulfoxide (DMSO) up to 82%, with Tg values ranging between 39 °C and 65 °C depending on the GF value. This study brings a much needed highlight on the little-known carbamate/aldehyde reaction and demonstrates its potential for the synthesis of novel biobased NIPU thermosetting coatings using a simple monoaldehyde such as vanillin.

Biobased Nonisocyanate Polyurethanes as Recyclable and Intrinsic Self-Healing Coating with Triple Healing Sites.

Polymer coatings having high amounts of renewable carbon and self-healing properties are highly sought after in a sustainability perspective. We report here the development of bio-/CO2-derived nonisocyanate polyurethane (NIPU) coatings which are recyclable and healable via three different types of healing mechanisms. These NIPUs contain furan rings in their main chain which after cross-linking with bismaleimides form organogels having a thermo-reversible sol-gel transition and solvent-borne coatings with improved properties. Judicial selection of the bismaleimide cross-linker structure enabled us to produce recyclable and intrinsic healable coatings mediated by heat (thermo-healing), moisture (moisture-healing), and, more interestingly, dry conditions at room temperature (self-healing). The intrinsic moisture-healing property of NIPU-based coatings is unprecedented and is mainly due to the presence of hydroxyl functionalities in the NIPU structure. The uniqueness of these cross-linked biobased NIPU as recyclable coatings having triple healing sites present in their structure gives these materials potential for sustainable and functional applications.

Environment‐friendly synthesis of sustainable chitosan‐based nonisocyanate polyurethane: A biobased polymeric film

AbstractSustainable, biobased nonisocyanate polyurethane (NIPU) films having excellent water absorption characteristics were synthesized by a green‐chemistry approach, eliminating the use of any toxic component. An environment‐friendly bulk polyaddition reaction was carried out between a natural amine‐containing polysaccharide, chitosan, and carbonated soybean oil (CSBO) to prepare the NIPUs. Epoxidized soybean oil was reacted with carbon dioxide to obtain CSBO and the conversion was confirmed by Fourier transform infra‐red and 1H nuclear magnetic resonance spectroscopies. NIPUs synthesized via this method did not involve the use of any curing agent and the crosslinking density of the polymer could be varied by altering the amine content. NIPUs with higher chitosan content showed better thermal and chemical properties, and superior water absorption characteristics. FTIR studies confirmed the typical linkages of polyurethane and the swelling behavior justified its enhanced resistance to organic solvents. Karl Fischer titration study proved the excellent water‐absorption capacity by absorbing ~90% moisture from toluene. These properties enable NIPUs to have diverse probable applications in the fields of chemical‐resistant coating, sealant, and also as an inorganic plant growth substrate because of its high water holding capacity.

Bio-based healable non-isocyanate polyurethanes driven by the cooperation of disulfide and hydrogen bonds

Novel bio-based non-isocyanate polyurethanes with tunable mechanical and self-healing properties are successfully synthesized.

Non-isocyanate polyurethane thermoset based on a bio-resourced star-shaped epoxy macromonomer in comparison with a cyclocarbonate fossil-based epoxy resin: A preliminary study on thermo-mechanical and antibacterial properties

This study focued on the synthesis and investigation of a bio-based non-isocyanate polyurethane (NIPU) introduced as st-NIPU in comparison with a fossil-based NIPU. First, a star-shaped macromonomer was synthesized through bulk condensation reaction of glycerol and succinic acid using microwaves. Second, the star-shaped macromonomer was epoxidized using epichlorohydrin. Finally, the attained macromonomer was converted to cyclocarbonate star-shaped macromonomer (C-st-G-SA) via CO2 fixation reaction. All of the abovementioned macromonomers were characterized by 1H NMR and FTIR spectroscopies. The st-NIPU network containing 47% bio-resourced part was obtained by the reaction of C-st-G-SA and the amine curing agent. A commercial diglycidylether bisphenol A (DGEBA) epoxy was also CO2 fixed to obtain cyclocarbonate DGEBA (C-DGEBA) and after amine curing a NIPU was achieved (DGEBA-NIPU). The amine curing trends of C-st-G-SA as well as C-DGEBA were studied by differential scanning calorimetry (DSC) to adjust the curing conditions. Also, DSC was utilized to investigate the thermal transitions of the st-NIPU and DGEBA-NIPU networks and the results presented two glass transition temperatures (Tg) for st-NIPU. The appearance of these two Tgs were confirmed by dynamo-mechanical thermogram. Thermal degradation trend of st-NIPU displayed a degradation pattern similar to other polyurethanes. St-NIPU network showed a significant potential of film formation and it could be used in the surface coating applications. The antibacterial activity of st-NIPU films against E.coli and S.aureus bacteria was evaluated and the results showed an acceptable and significant antibacterial property especially against S. aureus bacterium.

Solvent- and Catalyst-free Synthesis, Hybridization and Characterization of Biobased Nonisocyanate Polyurethane (NIPU).

Nonisocyanate polyurethane (NIPU) is a research hotspot in polyurethane applications because it does not use phosgene. Herein, a novel method of solvent- and catalyst-free synthesis of a hybrid nonisocyanate polyurethane (HNIPU) is proposed. First, four diamines were used to react with ethylene carbonate to obtain four bis(hydroxyethyloxycarbonylamino)alkane (BHA). Then, BHA reacted with dimer acid under condensation in the melt to prepare four nonisocynate polyurethane prepolymers. Further, the HNIPUs were obtained by crosslinking prepolymers and resin epoxy and cured with the program temperature rise. In addition, four amines and two resin epoxies were employed to study the effects and regularity of HNIPUs. According to the results from thermal and dynamic mechanical analyses, those HNIPUs showed a high degree of thermal stability, and the highest 5% weight loss reached about 350 °C. More importantly, the utilization of these green raw materials accords with the concept of sustainable development. Further, the synthetic method and HNIPUs don’t need isocyanates, catalysts, or solvents.