Fatty Acid-Derived Diisocyanate and Biobased Polyurethane Produced from Vegetable Oil: Synthesis, Polymerization, and Characterization

Utilization of Plant Oils for Sustainable Polyurethane Adhesives: A Review

The utilization of plant oils as a renewable resource for the production of polyurethane adhesives presents a promising way to improve sustainability and reduce environmental impact. This review explores the potential of various vegetable oils, including waste oils, in the synthesis of polyurethanes as an alternative to conventional petroleum-based raw materials. The investigation highlights the environmental challenges associated with conventional polyurethane production and highlights the benefits of switching to bio-renewable oils. By examining the feasibility and potential applications of vegetable oil-based polyurethanes, this study emphasizes the importance of further research and development in this area to realize the full potential of sustainable polyurethane adhesives. Further research and development in this area are key to overcoming the challenges and realizing the full potential of plant-oil-based polyurethanes in various industrial applications.

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.

Preparation of Biobased Nonisocyanate Polyurethane/Epoxy Thermoset Materials Using Depolymerized Native Lignin

Polyurethane polymers are found in a wide range of material applications. However, the toxic nature of isocyanates used in their formulation is a major concern; hence, more environmentally friendly alternatives are of high interest in the search for new sustainable polymer materials. In this work, we present the preparation of isocyanate-free polyurethane/epoxy hybrid thermosets with a high biobased content (85-90 wt %). The isocyanate-free polyurethanes were based on polyhydroxyurethanes (PHUs) prepared from depolymerized native lignin, which we refer to as lignin hydrogenolysis oil (LHO). The LHO was functionalized with epichlorohydrin to yield the epoxidized structure (LHO-GE), which was in turn reacted with CO₂ to form the cyclocarbonated species (LHO-CC). Blends of the LHO-CC and glycerol diglycidyl ether (GDGE) were cured to produce hybrid PHU/epoxy (LHO-CC/GDGE) thermosets. Thermosetting materials with flexural moduli of 4.5 GPa and flexural strengths of 160 MPa were produced by optimizing the mass ratio of the two main components and the triamine hardener. These novel biobased hybrid materials outperformed the corresponding epoxy-only thermosets and comparable hybrid PHU/epoxy materials produced from petrochemicals.

Nonwoven Mats Based on Segmented Biopolyurethanes Filled with MWCNT Prepared by Solution Blow Spinning

To prepare nonwoven mats constituted by submicrometric fibers of thermally responsive biopolyurethanes (TPU) modified with multiwalled carbon nanotubes (MWCNT), solution blow spinning (SBS) was used. The TPU was the product of synthesis using poly(butylene sebacate)diol, PBSD, ethyl ester L-lysine diisocyanate (LDI), and 1,3-propanediol (PD) (PBSe:LDI:PD) as reactants. TPU was modified by adding different amounts of MWCNT (0, 0.5, 1, 2, and 3 wt.%). The effect of the presence and amount of MWCNT on the morphology and structure of the materials was studied using field-emission scanning electron microscopy (FESEM) and Fourier-transform infrared spectroscopy (FTIR), respectively, while their influence on the thermal and electric behaviors was studied using differential scanning calorimetry (DSC) and capacitance measurements, respectively. The addition of MWCNT by SBS induced morphological changes in the fibrous materials, affecting the relative amount and size of submicrometric fibers and, therefore, the porosity. As the MWCNT content increased, the diameter of the fibers increased and their relative amount with respect to all morphological microfeatures increased, leading to a more compact microstructure with lower porosity. The highly porous fibrous morphology of TPU-based materials achieved by SBS allowed turning a hydrophilic material to a highly hydrophobic one. Percolation of MWCNT was attained between 2 and 3 wt.%, affecting not only the electric properties of the materials but also their thermal behavior.

It Takes Two to Tango: Synergistic Expandable Graphite–Phosphorus Flame Retardant Combinations in Polyurethane Foams

Due to the high flammability and smoke toxicity of polyurethane foams (PUFs) during burning, distinct efficient combinations of flame retardants are demanded to improve the fire safety of PUFs in practical applications. This feature article focuses on one of the most impressive halogen-free combinations in PUFs: expandable graphite (EG) and phosphorus-based flame retardants (P-FRs). The synergistic effect of EG and P-FRs mainly superimposes the two modes of action, charring and maintaining a thermally insulating residue morphology, to bring effective flame retardancy to PUFs. Specific interactions between EG and P-FRs, including the agglutination of the fire residue consisting of expanded-graphite worms, yields an outstanding synergistic effect, making this approach the latest champion to fulfill the demanding requirements for flame-retarded PUFs. Current and future topics such as the increasing use of renewable feedstock are also discussed in this article.

Eco-Friendly Ether and Ester-Urethane Prepolymer: Structure, Processing and Properties

This study concerns bio-based urethane prepolymers. The relationship between the chemical structure and the thermal and processing parameters of bio-based isocyanate-terminated ether and ester-urethane prepolymers was investigated. Bio-based prepolymers were obtained with the use of bio-monomers such as bio-based diisocyanate, bio-based polyether polyol or polyester polyols. In addition to their composition, the bio-based prepolymers were different in the content of iso-cyanate groups content (ca. 6 and 8%). The process of pre-polymerization and the obtained bio-based prepolymers were analyzed by determining the content of unreacted NCO groups, Fourier transform infrared spectroscopy, proton nuclear magnetic resonance, thermogravimetry, and rheological measurements. The research conducted facilitated the evaluation of the properties and processability of urethane prepolymers based on natural components. The results indicate that a significant impact on the processability has the origin the polyol ingredient as well as the NCO content. The thermal stability of all of the prepolymers is similar. A prepolymer based on a poly-ether polyol is characterized by a lower viscosity at a lower temperature than the prepolymer based on a polyester polyol. The viscosity value depends on the NCO content.

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.

Eco-friendly polyurethane acrylate (PUA)/natural filler-based composite as an antifouling product for marine coating

In the current study, the polyurethane acrylate (PUA) polymer was synthesized by the addition reaction between an isophorone diisocyanate (IPDI) and 2-hydroxyethyl acrylate and cured by polyol. Different properties of the synthesized PUA were determined through diverse analysis methods. The polyurethane acrylate (PUA)/natural filler-based composite (rhizome water extract of Costus speciosus) was prepared as an antifouling agent. The results revealed that the lowest weight loss percentages were detected at 2 wt% PUA/natural filler composite loadings with Escherichia coli (ATCC 23,282) and Pseudomonas aeruginosa (ATCC 10,145). The decreased weight loss percentage may be attributed to the well dispersed natural composite resulting in a slippery surface that can prevent fouling adhesion. It was concluded that the PUA/natural filler composite might be considered an eco-friendly and economical solution to the biofouling problem. KEY POINTS: • A novel strategy for anti-biofouling. • A new composite reduced Gram-negative bacteria.

Recent Developments in Lignin- and Tannin-Based Non-Isocyanate Polyurethane Resins for Wood Adhesives—A Review

This review article aims to summarize the potential of using renewable natural resources, such as lignin and tannin, in the preparation of NIPUs for wood adhesives. Polyurethanes (PUs) are extremely versatile polymeric materials, which have been widely used in numerous applications, e.g., packaging, footwear, construction, the automotive industry, the lighting industry, insulation panels, bedding, furniture, metallurgy, sealants, coatings, foams, and wood adhesives. The isocyanate-based PUs exhibit strong adhesion properties, excellent flexibility, and durability, but they lack renewability. Therefore, this study focused on the development of non-isocyanate polyurethane lignin and tannin resins for wood adhesives. PUs are commercially synthesized using polyols and polyisocyanates. Isocyanates are toxic, costly, and not renewable; thus, a search of suitable alternatives in the synthesis of polyurethane resins is needed. The reaction with diamine compounds could result in NIPUs based on lignin and tannin. The research on bio-based components for PU synthesis confirmed that they have good characteristics as an alternative for the petroleum-based adhesives. The advantages of improved strength, low curing temperatures, shorter pressing times, and isocyanate-free properties were demonstrated by lignin- and tannin-based NIPUs. The elimination of isocyanate, associated with environmental and human health hazards, NIPU synthesis, and its properties and applications, including wood adhesives, are reported comprehensively in this paper. The future perspectives of NIPUs’ production and application were also outlined.

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.

Renewable Polyurethanes from Sustainable Biological Precursors

Due to the depletion of fossil fuels, higher oil prices, and greenhouse gas emissions, the scientific community has been conducting an ongoing search for viable renewable alternatives to petroleum-based products, with the anticipation of increased adaptation in the coming years. New academic and industrial developments have encouraged the utilization of renewable resources for the development of ecofriendly and sustainable materials, and here, we focus on those advances that impact polyurethane (PU) materials. Vegetable oils, algae oils, and polysaccharides are included among the major renewable resources that have supported the development of sustainable PU precursors to date. Renewable feedstocks such as algae have the benefit of requiring only sunshine, carbon dioxide, and trace minerals to generate a sustainable biomass source, offering an improved carbon footprint to lessen environmental impacts. Incorporation of renewable content into commercially viable polymer materials, particularly PUs, has increasing and realistic potential. Biobased polyols can currently be purchased, and the potential to expand into new monomers offers exciting possibilities for new product development. This Review highlights the latest developments in PU chemistry from renewable raw materials, as well as the various biological precursors being employed in the synthesis of thermoset and thermoplastic PUs. We also provide an overview of literature reports that focus on biobased polyols and isocyanates, the two major precursors to PUs.

Azelaic Acid/Expanded Graphite Composites with High Latent Heat Storage Capacity and Thermal Conductivity at Medium Temperature

A novel azelaic acid/expanded graphite (AA/EG) phase change composite (PCC) was fabricated as a shape-stabilized phase change material (PCM) for latent heat storage at medium temperatures. The composite exhibited a low supercooling degree and high heat storage capacity. Despite the impregnation of a high quantity of AA (85 wt %) in the porous network of EG, there was no leakage of liquid AA. This was attributed to the capillary forces and surface tension forces. The pure AA exhibited a melting temperature of 108.0 °C, with an intrinsically low supercooling degree of 5.8 °C. The melting temperature of AA in the PCC decreased slightly to 105.8 °C, and there was a significant decrease in the supercooling degree to 1.0 °C. The AA/EG PCC exhibited a high latent heat storage capacity of 162.5 J/g, and there was a significant gap between the decomposition temperature and the phase change temperature range. Therefore, the composite exhibited high thermal stability during operations. The results of an accelerated thermal cycling test (200 cycles) indicated the high cycling durability and chemical stability of the PCC. The thermal conductivity of AA increased by 15.7 times after impregnation in EG, as compared to that of the pure AA, and thus, thermal kinetics of the PCC was improved. The results of a heat storage/release test with 15 g of the PCM revealed that the melting and solidification of the AA/EG PCC were 5.0-fold and 7.4-fold faster, respectively, than those of the pure AA. This was attributed to the high thermal conductivity of the PCC.

Cellulose and Graphene Based Polyurethane Nanocomposites for FDM 3D Printing: Filament Properties and Printability

3D printing has exponentially grown in popularity due to the personalization of each printed part it offers, making it extremely beneficial for the very demanding biomedical industry. This technique has been extensively developed and optimized and the advances that now reside in the development of new materials suitable for 3D printing, which may open the door to new applications. Fused deposition modeling (FDM) is the most commonly used 3D printing technique. However, filaments suitable for FDM must meet certain criteria for a successful printing process and thus the optimization of their properties in often necessary. The aim of this work was to prepare a flexible and printable polyurethane filament parting from a biocompatible waterborne polyurethane, which shows potential for biomedical applications. In order to improve filament properties and printability, cellulose nanofibers and graphene were employed to prepare polyurethane based nanocomposites. Prepared nanocomposite filaments showed altered properties which directly impacted their printability. Graphene containing nanocomposites presented sound enough thermal and mechanical properties for a good printing process. Moreover, these filaments were employed in FDM to obtained 3D printed parts, which showed good shape fidelity. Properties exhibited by polyurethane and graphene filaments show potential to be used in biomedical applications.

Eco-friendly Route for Thermoplastic Polyurethane Elastomers with Bio-based Hard Segments Composed of Bio-glycol and Mixtures of Aromatic-Aliphatic and Aliphatic-Aliphatic Diisocyanate

Application of bio-based diisocyanates with low volatility instead petrochemical diisocyanates has positive impact on environment by reduction of hazardous effects on living organisms and lead to bio-based polyurethanes (bio-PUs) with good usage properties. This work was focused on the synthesis and chosen properties examination of partially bio-based thermoplastic polyurethane elastomers (bio-PUs) obtained using diisocyanate mixtures, polytetrahydrofurane (PolyTHF) and bio-1,3-propanediol (bio-PDO). Two types of diisocyanate mixtures were prepared as follows: aliphatic-aliphatic based on hexamethylene diisocyanate with partially bio-based aliphatic diisocyanate Tolonate™ X FLO 100 (HDI-FLO) and aromatic-aliphatic based on diphenylmethane diisocyanate with partially bio-based diisocyanate (MDI-FLO) with reduction of 25 mass% of petrochemical diisocyanate. Bio-PUs were obtained via prepolymer method. Thermoplastic polyurethane elastomers have been examined in the terms of chemical structure and thermal, thermomechanical, mechanical and physicochemical properties. Bio-PU based on HDI-FLO diisocyanate mixture exhibited higher thermal stability. The beginning of thermal decomposition took a place at lower temperature ca. 30 ºC) and lower rate than the MDI-PU based materials. DMA analysis showed that HDI-FLO based polyurethanes exhibited greater capacity to accumulate energy and higher stiffness. Both materials characterized similar tensile strength and hardness, but with difference that TPU based on HDI-FLO relieved greater elongation at break about 360% reached 813%. Taking into account versatile properties of bio-TPU, these material can find application in many branches of industry.

PEG-POSS Star Molecules Blended in Polyurethane with Flexible Hard Segments: Morphology and Dynamics

A star polymer with a polyhedral oligomeric silsesquioxanne (POSS) core and poly(ethylene glycol) (PEG) vertex groups is incorporated in a polyurethane with flexible hard segments in-situ during the polymerization process. The blends are studied in terms of morphology, molecular dynamics, and charge mobility. The methods utilized for this purpose are scanning electron and atomic force microscopies (SEM, AFM), X-ray diffraction (XRD), differential scanning calorimetry (DSC), and to a larger extent dielectric relaxation spectroscopy (DRS). It is found that POSS reduces the degree of crystallinity of the hard segments. Contrary to what was observed in a similar system with POSS pendent along the main chain, soft phase calorimetric glass transition temperature drops as a result of plasticization, and homogenization of the soft phase by the star molecules. The dynamic glass transition though, remains practically unaffected, and a hypothesis is formed to resolve the discrepancy, based on the assumption of different thermal and dielectric responses of slow and fast modes of the system. A relaxation α′, slower than the bulky segmental α and common in polyurethanes, appears here too. A detailed analysis of dielectric spectra provides some evidence that this relaxation has cooperative character. An additional relaxation g, which is not commonly observed, accompanies the Maxwell Wagner Sillars interfacial polarization process, and has dynamics similar to it. POSS is found to introduce conductivity and possibly alter its mechanism. The study points out that different architectures of incorporation of POSS in polyurethane affect its physical properties by different mechanisms.

A Novel Resorbable Composite Material Containing Poly(ester-co-urethane) and Precipitated Calcium Carbonate Spherulites for Bone Augmentation-Development and Preclinical Pilot Trials

Polyurethanes have the potential to impart cell-relevant properties like excellent biocompatibility, high and interconnecting porosity and controlled degradability into biomaterials in a relatively simple way. In this context, a biodegradable composite material made of an isocyanate-terminated co-oligoester prepolymer and precipitated calcium carbonated spherulites (up to 60% w/w) was synthesized and investigated with regard to an application as bone substitute in dental and orthodontic application. After foaming the composite material, a predominantly interconnecting porous structure is obtained, which can be easily machined. The compressive strength of the foamed composites increases with raising calcium carbonate content and decreasing calcium carbonate particle size. When stored in an aqueous medium, there is a decrease in pressure stability of the composite, but this decrease is smaller the higher the proportion of the calcium carbonate component is. In vitro cytocompatibility studies of the foamed composites on MC3T3-E1 pre-osteoblasts revealed an excellent cytocompatibility. The in vitro degradation behaviour of foamed composite is characterised by a continuous loss of mass, which is slower with higher calcium carbonate contents. In a first pre-clinical pilot trial the foamed composite bone substitute material (fcm) was successfully evaluated in a model of vertical augmentation in an established animal model on the calvaria and on the lateral mandible of pigs.

Fabrication of silane-grafted graphene oxide and its effect on the structural, thermal, mechanical, and hysteretic behavior of polyurethane

Incorporation of nanofillers into polyurethane (PU) is a promising technique for enhancing its thermal and mechanical properties. Silane grafting has been used as a surface treatment for the functionalization of graphene oxide (GO) with numerous reactive sites dispersed on its basal plane and edge. In this study, amine-grafted GO was prepared using silanization of GO with (3-aminopropyl)triethoxysilane. The functionalized graphene oxide (fGO) was characterized by Fourier transform infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy. Next, it was introduced in PU fabricated using polycaprolactone diol, castor oil, and hexamethylene diisocyanate. The fGO-PU nanocomposites were in turn characterized by FT-IR, X-ray diffraction, scanning electron microscopy, differential scanning calorimetry, thermogravimetric analysis, and a universal testing machine. The results obtained from these analyses showed changes in structural thermal properties, as well as improved thermal stability and mechanical properties because of the strong interfacial adhesion between the fGO and the PU matrix.

Electrospun nanofiber-reinforced three-dimensional chitosan matrices: Architectural, mechanical and biological properties

The poor intrinsic mechanical properties of chitosan hydrogels have greatly hindered their practical applications. Inspired by nature, we proposed a strategy to enhance the mechanical properties of chitosan hydrogels by construction of a nanofibrous and cellular architecture in the hydrogel without toxic chemical crosslinking. To this end, electrospun nanofibers including cellulose acetate, polyacrylonitrile, and SiO₂ nanofibers were introduced into chitosan hydrogels by homogenous dispersion and lyophilization. With the addition of 30% cellulose acetate nanofibers, the cellular structure could be maintained even in water without crosslinking, and integration of 60% of the nanofibers could guarantee the free-standing structure of the chitosan hydrogel with a low solid content of 1%. Moreover, the SiO₂ nanofiber-reinforced chitosan (SiO₂ NF/CS) three-dimensional (3D) matrices exhibit complete shape recovery from 80% compressive strain and excellent injectability. The cellular architecture and nanofibrous structure in the SiO₂ NF/CS matrices are beneficial for human mesenchymal stem cell adhesion and stretching. Furthermore, the SiO₂ NF/CS matrices can also act as powerful vehicles for drug delivery. As an example, bone morphogenetic protein 2 could be immobilized on SiO₂ NF/CS matrices to induce osteogenic differentiation. Together, the electrospun nanofiber-reinforced 3D chitosan matrices exhibited improved mechanical properties and enhanced biofunctionality, showing great potential in tissue engineering.

Structural insight into the viscoelastic behaviour of elastomeric polyesters: effect of the nature of fatty acid side chains and the degree of unsaturation

Increase in unsaturation of fatty acid side chains results in decrease of zero-shear viscosity, degree of entanglement and resilience of polyesters. Cis double bonds act as kinks that prevent molecular packing of polymer chains.

From the Synthesis of Biobased Cyclic Carbonate to Polyhydroxyurethanes: A Promising Route towards Renewable Non-Isocyanate Polyurethanes

With a global production of around 18 million tons (6th among all polymers) and a wide range of applications, such as rigid and soft foams, elastomers, coatings, and adhesives, polyurethanes (PUs) are a major polymer family. Nevertheless, they present important environmental and health issues. Recently, new and safer PUs, called non-isocyanate polyurethanes (NIPUs), have become a promising alternative to replace conventional PUs. Sustainable routes towards NIPUs are discussed herein from the perspective of green chemistry. The main focus is on the reaction between biobased carbonates and amines, which offers an interesting pathway to renewable polyhydroxyurethanes (PHUs). An overview of different routes for the synthesis of PHUs draws attention to the green synthesis of cyclic carbonate (CC) compounds and the aminolysis reaction. Current state-of-the-art of different biobased building blocks for the synthesis of PHUs focuses on CC compounds. Three classes of compounds are defined according to the feedstock: 1) vegetable fats and oils, 2) starch and sugar resources, and 3) wood derivatives. Finally, biobased PHU properties are discussed.

A review on versatile applications of blends and composites of CNC with natural and synthetic polymers with mathematical modeling

Cellulose is world's most abundant, renewable and recyclable polysaccharide on earth. Cellulose is composed of both amorphous and crystalline regions. Cellulose nanocrystals (CNCs) are extracted from crystalline region of cellulose. The most attractive feature of CNC is that it can be used as nanofiller to reinforce several synthetic and natural polymers. In this article, a comprehensive overview of modification of several natural and synthetic polymers using CNCs as reinforcer in respective polymer matrix is given. The immense activities of CNCs are successfully utilized to enhance the mechanical properties and to broaden the field of application of respective polymer. All the technical scientific issues have been discussed highlighting the recent advancement in biomedical and packaging field.

Effect of Evening Primrose Oil-Based Polyol on the Properties of Rigid Polyurethane⁻Polyisocyanurate Foams for Thermal Insulation

The article presents the results of research on the synthesis of a new biopolyol based on evening primrose oil, and its use in the production of rigid polyurethane⁻polyisocyanurate foams intended for thermal insulation. The obtained biopolyol was subjected to analytical, physicochemical, and spectroscopic tests (Fourier transform infrared (FTIR), ¹H NMR, 13C NMR) to confirm its suitability for the synthesis of polyurethane materials. Then, it was used for the partial replacement of the petrochemical polyol in the polyurethane formulation. Obtained rigid polyurethane⁻polyisocyanurate foams are characterized by a lower apparent density, brittleness, water absorption, and thermal conductivity coefficient λ. In addition, foams modified by biopolyols had a higher content of closed cells and higher aging resistance. The results of the conducted research showed that the use of the biopolyol based on evening primrose oil may be an alternative to petrochemical polyols. The research presented herein is perfectly consistent with the trends of sustainable development and the philosophy of green chemistry.

Microbial Conversion of Vegetable Oil to Hydroxy Fatty Acid and Its Application to Bio-Based Polyurethane Synthesis

New polyurethanes were synthesized based on dihydroxy fatty acid obtained by the microbial conversion of olive oil. Monounsaturated 7,10-dihydroxy-8(E)-octadecenoic acid (DOD) was produced from olive oil by Pseudomonas aeruginosa PR3 and reacted with hexamethylene diisocyanate (HMDI) at different ratios to form polyurethanes. Fourier transform infrared spectroscopy and gas chromatography/mass spectrometry confirmed the synthesis of DOD. The thermal and tensile properties of the polyurethanes were investigated by differential scanning calorimetry, thermogravimetric analysis, and a universal testing machine. At an isocyanate/hydroxyl ratio of 1.4, the polyurethane exhibited an elongation at break of 59.2% and a high tensile strength of 37.9 MPa. DOD was also mixed with polycaprolactone diol or polyethylene glycol at different weight ratios and then reacted with HMDI to produce new polyurethanes of various properties. These polyurethanes displayed higher elongation at break and good thermal stability. This is the first report on the synthesis of polyurethanes based on DOD produced by the microbial conversion of vegetable oil.

Design and development of low cost polyurethane biopolymer based on castor oil and glycerol for biomedical applications

In the current study, we present the synthesis of novel low cost bio-polyurethane compositions with variable mechanical properties based on castor oil and glycerol for biomedical applications. A detailed investigation of the physicochemical properties of the polymer was carried out by using mechanical testing, ATR-FTIR, and X-ray photoelectron spectroscopy (XPS). Polymers were also tested in short term in-vitro cell culture with human mesenchymal stem cells to evaluate their biocompatibility for potential applications as biomaterial. FTIR analysis confirmed the synthesis of castor oil and glycerol based PU polymers. FTIR also showed that the addition of glycerol as co-polyol increases crosslinking within the polymer backbone hence enhancing the bulk mechanical properties of the polymer. XPS data showed that glycerol incorporation leads to an enrichment of oxidized organic species on the surface of the polymers. Preliminary investigation into in vitro biocompatibility showed that serum protein adsorption can be controlled by varying the glycerol content with polymer backbone. An alamar blue assay looking at the metabolic activity of the cells indicated that castor oil based PU and its variants containing glycerol are non-toxic to the cells. This study opens an avenue for using low cost bio-polyurethane based on castor oil and glycerol for biomedical applications.

Renewable polyols for advanced polyurethane foams from diverse biomass resources

This review highlights recent advances in the synthesis of renewable polyols, used for making polyurethane foams, from biomass.

Complete Depolymerization and Repolymerization of a Sugar Poly(orthoester)

The capability of a polymer to depolymerize, regenerating its original monomer for further polymerization, is very attractive in terms of sustainability. Recently discovered sugar poly(orthoesters) are an important class of glycopolymer. The high sensitivity of the backbone orthoester linkage toward acidolysis provides a valuable model to study the depolymerization. Herein, a sugar poly(orthoester) is shown to be completely depolymerized under acidic conditions. Interestingly, instead of the original monomer, the depolymerization gave a stable cyclic product (1,6-anhydro glucopyranose) in most cases, which was kinetically and thermodynamically favored. However, this pathway could be inhibited by chemically deactivating a key intermediate and thus favoring the formation of the original monomer. Efficient repolymerizaton of the regenerated monomer is also demonstrated.

Designing of cardanol based polyol and its curing kinetics with melamine formaldehyde resin

Commercially used industrial baking enamels consist of alkyd or polyester resin with melamine formaldehyde. These resins are mainly derived from fossil resources. Considering growing environmental legislation regarding use of petroleum based raw materials, utilization of renewable resources to synthesize various chemistries can be the only obvious option as far as academia and industries are concerns. The present work deals with exploration of one of the natural resources (Cardanol) for polyol synthesis, its characterization (FTIR and NMR) and its curing behavior with melamine formaldehyde resin by differential scanning calorimetry (DSC). The optimized formulations from DSC study were further evaluated for general coating properties to study the suitability of developed polyol for industrial coating application. The experimental studies revealed that melamine content in the curing mixtures and thereby developed crosslinking density played an important role in deciding the coatings properties.