Chain extension of dimer fatty acid- and sugar-based polyurethanes in aqueous dispersions

Exploring the synergistic effect of carboxymethyl cellulose and chitosan in enhancing thermal stability of polyurethanes through statistical mixture design approach

The thermal stability of polyurethanes, known for its limitations, was addressed in this research by seeking improvement through the introduction of carbohydrate-based chain extenders. In this research paper, we systematically sought to improve the thermal resistance of polyurethanes by incorporating carboxymethyl cellulose and chitosan, representing a pioneering application of the mixture design approach in their preparation. In this synthesis, hydroxyl-terminated polybutadiene and isophorone diisocyanate (IPDI) were reacted to prepare -NCO terminated prepolymer, which was subsequently reacted with varying mole ratios of CMC and CSN to develop a series of five PU samples. The prepared PU samples were characterized using the Fourier-transformed infrared spectroscopic technique. Thermal pyrolysis of PU samples was examined using thermal gravimetric analysis (TGA). It was observed that, among all the samples, PUS-3 showed remarkable thermal stability over a wide temperature range. A comprehensive statistical analysis was conducted to substantiate the experimental findings. It was estimated that CMC and CSN significantly enhance the thermal stability of the samples when involved in an interaction fashion. The ANOVA Table for the mixture design demonstrates that over 90 % of the total variation in thermal stability is explained by the mixture model across a wide temperature range. Moreover, PSU-3 exhibited 4 % more thermal stability over a wide range of temperatures on average, as compared to contemporary samples.

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.

Chitin Nanofiber-Reinforced Waterborne Polyurethane Nanocomposite Films with Enhanced Thermal and Mechanical Performance

To attain eco-friendly polyurethane composites with enhanced thermal and mechanical properties, in this study, a series of cationic waterborne polyurethane (cWPU) nanocomposite films reinforced with 1-50 wt% chitin nanofiber (ChNF) loadings was fabricated by a facile aqueous dispersion casting. The microstructure, thermal and mechanical properties of the nanocomposite films were investigated by considering the loading content and the interfacial interaction of ChNF in the cWPU matrix. For the purpose, a hard/soft segmented cWPU with an average particle size of ∼151 nm in aqueous dispersion was synthesized by using poly(tetramethylene glycol), isophorone diisocyanate, N-methyldiethanolamine, and 1,4-butanediol. The FT-IR spectra confirmed the existence of specific hydrogen-bonding interactions between hydroxyl/acetyl amine/ammonium groups of ChNFs and urethane/protonated amine groups of cWPU hard segments. Accordingly, the thermal decomposition temperatures of cWPU/ChNF nanocomposite films increased with increasing the ChNF content. In addition, the storage moduli of cWPU/ChNF nanocomposite films increased significantly with the increment of ChNF content up to ∼7 wt%, which stems from the restricted chain mobility of cWPU backbones composed of semicrystalline soft segments and hard segments interacting with ChNFs via multiple hydrogen-bonding interactions.

Au@polydopamine nanoparticles/tocilizumab composite as efficient scavengers of oxygen free radicals for improving the treatment of rheumatoid arthritis

Rheumatoid arthritis (RA) is the most common chronic autoimmune disorder associated with high-cost, side effects, and low therapeutic effects. To improve the treatment of RA, we originally developed a novel anti-RA Au@polydopamine nanoparticles (PDANPs)/TCZ composite using PDANPs as the binding sites of gold nanoparticles (AuNPs) and the drug carries of tocilizumab (TCZ) through a facile and environmentally-friend method, aiming to effectively scavenge oxygen free radicals (OFR) and inhibit the formation of related inflammatory factors. Characterizations showed that AuNPs with the size of 11.4 ± 2.9 nm randomly distributed onto the surface of PDANPs (145.8 ± 31.9 nm), meanwhile TCZ was chemically cross-linked to PDANPs through Schiff base linkage. The synthesized composite had good biocompatibility that can promote the proliferation and growth of chondrocytes and fibroblasts. More importantly, Au@PDANPs/TCZ composite showed more excellent abilities to scavenge OFR and inhibit the related inflammatory factors in vitro and in vivo than that of AuNPs and PDANPs owing to the synergistic scavenging effect, ensuring its best therapeutic effect in RA therapy. This new composite will have application potential in the treatment of RA related disease.

Influences of cellulose nanofibril on microstructures and physical properties of waterborne polyurethane-based nanocomposite films

We herein report the effects of carboxymethylated cellulose nanofibril (c-CNF) on the microstructure, thermal and mechanical properties of waterborne polyurethane (WPU)-based nanocomposite films. For the purpose, an aqueous dispersion of hard/soft segmented WPU with a mean particle size of ∼169 nm was manufactured by using poly(propylene glycol), isophorone diisocyanate, 2,2-dimethylolpropionic acid and 1,4-butanediol. WPU nanocomposite films with 1-50 wt% c-CNF loadings were then manufactured via an efficient casting method. The FT-IR spectra revealed the presence of hydrogen-bonding interactions between the urethane/urea groups of WPU hard segments and the carboxymethyl/hydroxyl groups of c-CNF. Accordingly, the thermal and thermo-oxidative stability of the nanocomposite films was noticeably enhanced by the introduction of c-CNF. In addition, the storage moduli of the nanocomposite films as well as the glass transition temperatures of WPU hard segments increased significantly with increasing the c-CNF content by ∼7 wt% owing to the specific interactions between c-CNF and WPU hard segments.

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.

Sustainable coatings from bio-based, enzymatically synthesized polyesters with enhanced functionalities

Renewable coatings have been prepared from sorbitol-derived aliphatic polyesters with enhanced functionalities, i.e. pendant and terminal hydroxyl groups, synthesized via enzymatic catalysis.

Waterborne polyurethanes based on macrocyclic thiacalix[4]arenes as novel emulsifiers: synthesis, characterization and anti-corrosion properties

1,3-alternate derivatives of thiacalix[4]arenes were employed as new macrocyclic emulsifiers to synthesize waterborne polyurethanes as environmental friendly anti-corrosive coatings for mild steel.

Research on the post-chain extension of aqueous polyurethane dispersions

The post-chain extension efficiency of APUDs were influenced by the particle size and the “cage effect” whatever the water or polyamine as the chain extender. The post-chain reaction mechanism: (a) small particle size; (b) big particle size.

Phosphonic Acid-Functionalized Polyurethane Dispersions with Improved Adhesion Properties

A facile route to phosphorus-functionalized polyurethane dispersions (P-PUDs) with improved adhesion properties is presented. (Bis)phosphonic acid moieties serve as adhesion promoting sites that are covalently attached via an end-capping reaction to isocyanate-reactive polyurethane particles under aqueous conditions. The synthetic approach circumvents solubility issues, offers great flexibility in terms of polyurethane composition, and allows for the synthesis of semicrystalline systems with thermomechanical response due to reversible physical cross-linking. Differential scanning calorimetry (DSC) is used to investigate the effect of functionalization on the semicrystallinity. The end-capping conversion was determined via inductively-coupled plasma optical emission spectroscopy (ICP-OES) and was surprisingly found to be almost independent of the stoichiometry of reaction, suggesting an adsorption-dominated process. Particle charge detection (PCD) experiments reveal that a dense surface coverage of phosphonic acid groups can be attained and that, at high functionalization degrees, the phosphonic adhesion moieties are partially dragged inside the colloidal P-PUD particle. Quartz crystal microbalance with dissipation (QCMD) investigations conducted with hydroxyapatite (HAP) and stainless steel sensors as model surfaces show a greatly enhanced affinity of the aqueous P-PUDs and furthermore indicate polymer chain rearrangements and autonomous film formation under wet conditions. Due to their facile synthesis, significantly improved adhesion, and variable film properties, P-PUD systems such as the one described here are believed to be of great interest for multiple applications, e.g., adhesives, paints, anticorrosion, or dentistry.

Hydrophobe-free miniemulsion polymerization: towards high solid content of fatty acid-based poly(urethane-urea) latexes

High solid content of aqueous fatty acid-based PU latexes.

Synthesis and characterization of solvent-free waterborne polyurethane dispersion with both sulfonic and carboxylic hydrophilic chain-extending agents for matt coating applications

Self-extinction and solvent-free waterborne polyurethane resin without the addition of extra matting agents.