Polyurethane Molecules Research Articles

Impact-resistant, high-toughness, self-healable elastomers with physical-chemical dual-crosslinking networks for efficient energy absorption

The intense mechanical impact that causes serious hazards has made stringent requirements for protective materials. Supramolecular elastomers integrating high toughness, impact resistance, and self-healing properties are desired as intelligent energy-absorbing materials. Herein, we construct a physical-chemical dual-network polyurethane (PU), via the dissociation and reconfiguration of dynamic hierarchical hydrogen bonds enables energy dissipation and self-healing properties, and the chemical cross-linking network maintains the stability and recoverability of the elastomer network. By tuning the proportion of the physical-chemical network in the elastomer, the supramolecular PU elastomer not only exhibits extraordinary ductility (1922.71 %), and excellent toughness (22.10 MJ m−3), but also shows outstanding impact resistance (an energy absorption efficiency of 85.6 %). The dissociation of dynamic hierarchical hydrogen bonds under high frequency renders the elastomer with special strain-hardening properties, which allows the material to absorb tremendous impact energy. The presence of a covalent crosslinking network prevents the creeping of the PU molecules and assists in the recovery and reconstruction of hydrogen bonds, as well as the self-healing of the material. In addition, the supramolecular PU demonstrates remarkable capability to enhance the energy absorption performance of commercial thermoplastic PU foam. By incorporating 30 % of supramolecular PU, the composite foam prepared by supercritical CO2 foaming exhibits an outstanding energy absorption efficiency of 85.1 %, owing to the buffering property of the porous structure and the strain-hardening effect of the supramolecular PU. The physical-chemical dual-network elastomer provides a potential strategy for intelligent anti-impact materials and foams.

Synthesis, Morphology, and Particle Size Control of Acidic Aqueous Polyurethane Dispersions.

A range of charge-stabilized aqueous polyurethane (PU) dispersions comprising hard segments formed from hydrogenated methylene diphenyl diisocyanate (H12MDI) with dimethylolpropionic acid (DMPA) and ethylenediamine, and soft segments of poly(tetramethylene oxide) of different molecular weights are synthesized. Characterization of the dispersions by mass spectrometry, gel permeation chromatography, small-angle X-ray scattering, atomic force microscopy, and infrared spectroscopy shows that they are composed of PUs self-assembled into spherical particles (primary population) and supramolecular structures formed by hydrogen-bonded H12MDI and DMPA acid-rich fragments (secondary population). Analysis of the scattering patterns of the dispersions, using a structural model based on conservation of mass, reveals that the proportion of supramolecular structures increases with DMPA content. It is also found that the PU particle radius follows the predictions of the particle surface charge density model, originally developed for acrylic statistical copolymers, and is controlled by hydrophile (DMPA) content in the PU molecules, where an increase in PU acidity results in a decrease in particle size. Moreover, there is a critical fractional coverage of hydrophiles stabilizing the particle surface for a given polyether soft-segment molecular weight, which increases with the polyether molecular weight, confirming that more acid groups are required to stabilize a more hydrophobic composition.

Smart construction of metal chelating for enhancing waterborne polyurethane multi-crosslinked soybean meal adhesives

Developing low-cost renewable bio-based adhesives with excellent properties remains a challenge. Soybean meal (SM) adhesives have gained widespread attention for being green. However, it still has the problems of poor water resistance, low toughness, and easy to mildew. Herein, a waterborne polyurethane (TWPU) with carboxyl side chains was synthesized from tartaric acid (TA). It was used as chelating ligands to form the metal chelating to synergistically modify (SM) adhesives. This overall improved the adhesives bonding strength, toughness and water resistance. The coordination interactions between the polyurethane molecules and the protein molecules of SM were formed by multi-crosslinking via metal chelating, covalent bonding, and hydrogen bonding to enhance the adhesive's toughness, bonding strength and water resistance. As a result, the wet bond strength and toughness of the modified SM adhesives were 166.7 % and 275.3 % higher than blank sample, respectively, reaching 1.29 MPa and 0.61 J. Considering of the used raw materials and synthesis method in our process are simple and widely available, this study provides an eco-friendly and effective method for green, low-cost, and high-performance wood-based composite adhesives.

Overcoming the Dilemma of In Vivo Stable Adhesion and Sustained Degradation by the Molecular Design of Polyurethane Adhesives for Bone Fracture Repair.

Bone adhesive is a promising candidate to revolutionize the clinical treatment of bone repairs. However, several drawbacks have limited its further clinical application, such as unreliable wet adhesive performance leading to fixation failure and poor biodegradability inhibiting bone tissue growth. By incorporating catechol groups and disulfide bonds into polyurethane (PU) molecules, an injectable and porous PU adhesive is developed with both superior wet adhesion and biodegradability to facilitate the reduction and fixation of comminuted fractures and the subsequent regeneration of bone tissue. The bone adhesive can be cured within a reasonable time acceptable to a surgeon, and then the wet bone adhesive strength is near 1.30MPa in 1h. Finally, the wet adhesive strength to the cortical bone will achieve about 1.70MPa, which is also five times more than nonresorbable poly(methyl methacrylate) bone cement. Besides, the cell culture experiments also indicate that the adhesives show excellent biocompatibility and osteogenic ability in vitro. Especially, it can degrade in vivo gradually and promote fracture healing in the rabbit iliac fracture model. These results demonstrate that this ingenious bone adhesive exhibits great potential in the treatment of comminuted fractures, providing fresh insights into the development of clinically applicable bone adhesives.

Study of viscoelastic damage and micromechanism of polyurethane in freeze-thaw cycle environment

To investigate the viscoelastic properties of polyurethane under the action of freeze-thaw cycles. Polyurethane specimens excessed examined using atomic force microscopy, nanoindentation tests, and differential scanning calorimetry (DSC) after 0, 3, 5, and 7 freeze-thaw cycles. The molecular structure and property damage process was also investigated using molecular dynamics. The findings of molecular simulations revealed that the freeze-thaw cycle causes the aggregated system to disperse within the polyurethane molecule, resulting in an increase in its modulus. The testing findings revealed that the roughness of the polyurethane surface steadily decreased as the number of freeze-thaw cycles increased, as did the adhesion to various substrates. In the test results of nanoindentation, the elastic modulus showed an increasing trend, and the contact indentation depth gradually decreased. This suggests that freeze-thaw cycles impair polyurethane's elastic and flexible characteristics. The freeze-thaw cycle raised the melting temperature of polyurethane in the differential scanning calorimetry experiment findings. This confirms the experimental findings of increased elastic modulus and hardness in nanoindentation. In conclusion, further study may be undertaken to change polyurethanes by adding water-repellent compounds to them, which can be accomplished by modifying the molecular structure inside the polyurethanes to withstand environmental harm. The findings of this research lay a theoretical foundation for the resilience of polyurethane materials to environmental deterioration in a variety of industries, such as construction, where freeze-thaw cycles exist.

Sustainable Strategies for Synthesizing Lignin-Incorporated Bio-Based Waterborne Polyurethane with Tunable Characteristics.

In this study, we introduce a novel approach for synthesizing lignin-incorporated castor-oil-based cationic waterborne polyurethane (CWPU-LX), diverging significantly from conventional waterborne polyurethane dispersion synthesis methods. Our innovative method efficiently reduces the required solvent quantity for CWPU-LX synthesis to approximately 50% of that employed in traditional WBPU experimental procedures. By incorporating lignin into the polyurethane matrix using this efficient and reduced-solvent method, CWPU-LX demonstrates enhanced properties, rendering it a promising material for diverse applications. Dynamic interactions between lignin and polyurethane molecules contribute to improved mechanical properties, enhanced thermal stability, and increased solvent resistance. Dynamic interactions between lignin and polyurethane molecules contribute to improved tensile strength, up to 250% compared to CWPU samples. Furthermore, the inclusion of lignin enhanced thermal stability, showcasing a 4.6% increase in thermal decomposition temperature compared to conventional samples and increased solvent resistance to ethanol. Moreover, CWPU-LX exhibits desirable characteristics such as protection against ultraviolet light and antibacterial properties. These unique properties can be attributed to the presence of the polyphenolic group and the three-dimensional structure of lignin, further highlighting the versatility and potential of this material in various application domains. The integration of lignin, a renewable and abundant resource, into CWPU-LX exemplifies the commitment to environmentally conscious practices and underscores the significance of greener materials in achieving a more sustainable future.

A study on the bonding performance of PU/AC interface

The tensile debonding process of a polyurethane (PU)-asphalt concrete (AC) adhesion system under different temperature fields was simulated in this paper using LAMMPS molecular simulation software, and the interfacial energy, radial distribution function, mean square displacement, number density curve, and force-displacement curve of the system were calculated. When the temperature was below 280 K, adsorption occurred between PU and asphalt, asphalt and silica, and PU and silica, but the interfacial energy between PU and silica and PU and asphalt was larger than that between asphalt and silica. A large number of PU molecules exist in the range of 5Å from the silica and the MSD curve of PU has a low value as a function. During the tensile process, the silica crystals and asphalt in PU-AC systems travel with the PU, and the final fracture location emerges inside the asphalt molecule rather than at the PU/AC contact. When the temperature rises over 280 degrees Celsius, only asphalt and silica remain after the stretching action, and adsorption between asphalt and PU occurs, but adsorption between PU and silica vanishes. Distance from the silica is 5Å range only a small amount of PU molecules, stretching model, PU molecules gradually detached from the asphalt and silica, the final damage section close to the PU/AC interface. The mechanical characteristics of PU/AC bonded specimens at different temperatures were evaluated in this work to validate the correctness of molecular simulation, and the test findings were in good agreement with the conclusions of molecular simulation. The results of this paper provide molecular-scale insights into the debonding mechanism of PU/AC interfaces.

Facile fabrication of robust and universal UV‐curable polyurethane composite coatings with antibacterial properties

AbstractThe colonization of bacteria and biofilm formation on the surface of medical devices is one of the main causes of nosocomial infections. The development of antimicrobial functional materials with robust and universal properties has been a hot research topic in this field. In this paper, a novel type of polyurethane composite coating was developed by a complementary combination of polyurethane and antibacterial agents. A photocurable anionic waterborne polyurethane was first synthesized using polycarbonate diol (PCDL), isophorone diisocyanate (IPDI), 2,2‐dimethylolpropionic acid (DMPA), and hydroxyethyl acrylate (HEA) as raw materials. Polyurethane composite coatings were prepared by associating cationic antibacterial agents with polyurethane molecules through electrostatic assembly, hydrophobic interactions and hydrogen bonding, and the mechanical properties, adhesion, and antibacterial properties of the polyurethane composite coatings were studied. The results showed that the polyurethane composite coatings had good mechanical properties, and the introduction of cationic antibacterial agents significantly improved the antibacterial ability of the polyurethane material. The antibacterial efficiency of polyurethane against E. coli and S. aureus reached 99% and exhibited durable antibacterial performance as well. Moreover, the polyurethane composite coatings showed excellent adhesion to a variety of substrates, demonstrating their potential application as a universal antimicrobial coating in the medical field.Highlights Construction of polyurethane composite with electrostatic self‐assembly method. Surface coating technology with fast curing, robustness, and universality. Excellent mechanical and antibacterial properties of composite coatings.

Laboratory Study and Molecular Dynamics Simulation of High- and Low-Temperature Properties of Polyurethane-Modified Asphalt

This study investigated the modification mechanism of polyurethane (PU) on the high- and low-temperature properties of asphalt based on experimental and molecular dynamics (MD) simulations. PU-modified asphalt was prepared using an in situ polymerization method. The high- and low-temperature properties of asphalt containing various PU contents were investigated via a series of laboratory tests. The asphalt molecular model, the PU molecular model, and the PU–asphalt mixes system were modeled using software. Based on reasonable models, the influence of PU content on the physical modulus and molecular motion of asphalt at high temperatures was researched using MD simulations. The glass transition temperature of PU-modified asphalt with different contents was obtained using software, and the free volume theory and molecular diffusion movement were used to interpret the improvement mechanism of PU content on the low-temperature performance of asphalt. The results indicate that PU effectively can improve the high- and low-temperature properties of asphalt. PU has a significant positive effect on the physical modulus of asphalt, and the effect becomes more significant with the increase of PU content. In addition, PU can form a tight structure with asphalt and increase the stability of the asphalt system. The free volume ensures the free movement of PU molecules in the asphalt, allowing PU to be dispersed homogeneously in the asphalt. However, the free volume decreases when the PU content exceeds 15% by weight, which limits the improvement of the low-temperature performance of asphalt. The results of molecular simulation can explain the enhancement mechanism of PU, providing a reference for the performance enhancement of PU-modified asphalt.

Thermal-driven cationic waterborne polyurethane crosslinker with oxime-based and catechol structure for the preparation of soybean protein-based adhesive with excellent adhesion properties

Recently, the research of waterborne polyurethane (WPU) as toughening matrix of soybean protein-based adhesives has attracted much attention. However, the intermolecular interaction between polyurethane and protein molecules is too weak to construct a compact crosslinking system to achieve strengthening and toughening adhesive systems. In this work, a thermal-driven cationic waterborne polyurethane (CWPOU) with oxime-isocyanate groups and catechol groups was synthesized. The obtained CWPOU emulsion was introduced into soybean meal (SM) matrix to fabricate a SM/CWPOU bio-adhesive. Thermal-driven elements in polyurethane molecules released isocyanate groups, increasing covalent crosslinking between crosslinker and protein molecules, synergies with non-covalent forces formed between catechol structures to improve the comprehensive bonding properties of the adhesives. As a result, the dry/wet bonding strengths of the modified adhesives were noticeably enhanced with the highest values observed (SM/CWPOU-4) reaching 169.6% and 191.4% that of pure SM adhesives, respectively. Furthermore, the hydrogen bonding provided by hard segments of polyurethane and noncovalent forces between catechol groups and wood substrates contributed to excellent cold-pressing performance of the bio-adhesives with a maximum value pleasantly reaching 298% that of pure SM. The mildew resistances of SM/CWPOU adhesives were attributed to bactericidal performance of the cationic structures and catechol groups in CWPOUs. This work provides an effective method to prepare the “green” and high-performance protein-based adhesives.

Waterborne organic silicone polyurethane with excellent self-healing performance for oil/water-separation and oil-recovery applications

While superhydrophobic coatings have been widely used for surface modification and protection, most suffer from relatively short service life due to the lack of self-healing mechanisms. Herein, a new self-healable coating formulation based on waterborne organic silicone polyurethane has been proposed by integrating disulfide groups into polyurethane molecules. The bulk polyurethane material with disulfide groups shows high self-healing efficiency of up to 90.8%. The polyurethane coating on cotton fabric showed high superhydrophobic performance even after severe damage. Furthermore, the coating showed excellent self-healing ability. The damaged surface could self-heal after heating at 80 °C for half an hour. The coating also exhibited excellent superhydrophobicity and extremely high oil/water-separation efficiency, even after experiencing 80 washes or being worn 800 times. The combination of superior self-healing ability and superhydrophobic properties of the waterborne organic silicone polyurethane coating provides a general approach for the long-term application of such coatings in harsh environments.

Bio-based and self-catalyzed waterborne polyurethanes as efficient corrosion inhibitors for sour oilfield environment

Sunflower oil was used as environmentally friendly source to develop novel self-catalyzed waterborne polyurethanes (WPUs) as efficient corrosion inhibitors for sour oilfield solution. A comprehensive experimental and computational analysis was performed to evaluate the inhibition effect of WPUs. The results of electrochemical measurements indicated that 200 µM of WPUs were effectively protected mild steel from sour corrosion by 95% and 94.6% at 25 °C and 60 °C, respectively. Furthermore, it was found that the best inhibition efficiency was provided by WPU when pyrrolidine was included in its structure, particularly at 60 °C. Additionally, a smoother steel surface was observed in the presence of WPUs, indicating the adsorption of the polyurethane molecules on the metal surface. The results of X-ray photoelectron spectroscopy further confirmed the chemical adsorption of WPUs on the surface of mild steel. Moreover, scanning Kelvin probe microscopy revealed that the potential distribution of the steel surface was shifted to the negative values, which show the adsorption of the inhibitor on the surface and inhibition of the corrosion process. Besides, high values of adsorption energy were achieved for WPUs using molecular dynamic simulation, indicating their spontaneous adsorption to the Fe (110) surface. The maximum adsorption energy of −794.9 kcal/mol was obtained for WPU3, which is consistent with experimental data. These results show that sunflower oil can be considered a potential source to develop self-catalyzed polyurethanes under mild conditions as effective corrosion inhibitors for sour environment.

Catalyst-free, highly sensitive and adjustable photo-responsive azobenzene liquid crystal elastomers based on dynamic multiple hydrogen bond

Photo-responsive liquid crystal elastomers (LCEs) containing azobenzene components have received great attention and are in great demand gap for the development of smart materials. Herein, we have prepared a novel azobenzene photo-responsive liquid crystal elastomer (HAzo-LCEs) through simultaneously introducing azobenzene molecules and 2-ureido-4-pyrimidone (UPy) units into main chain of polyurethane molecule. Utilizing polyurethane system into this HAzo-LCEs has a trade-off between the exceptional mechanical performance and quick response. Especially, the transformation of photo-responsive HAzo-LCEs from polydomain to monodomain liquid crystal structures has been achieved under the catalyst-free and low temperature conditions by exploiting the dynamic nature of multiple hydrogen bond between UPy units. This synthetic method breaks the dilemma that the conventional photo-responsive LCEs require the preparation of monodomain liquid crystal structures at high temperatures or with the help of a large number of catalysts. Importantly, the HAzo-LCEs sample can bend rapidly in response to the UV light, and the maximum bending angle of the sample could reach 144°. Intriguingly, the blended HAzo-LCEs sample can rapidly straighten and finally extended under green light, showing the high sensitivity and flexible adjustability. It is valuable to integrating the high sensitivity, flexible adjustability and complete reversibility into one photo-responsive elastomers of this HAzo-LCEs. Furthermore, the multiple hydrogen bonds from UPy units allows the HAzo-LCEs to regulate its dynamics and stability by increasing the number and binding sites through the advantages of adjustable strength, high selectivity and abundant formation modes, providing great design and application scope for photo-responsive liquid crystal elastomers. This design route of non-toxic PU-based HAzo-LCEs provides a novel approach to broaden photo-responsive LCEs application in sensor and actuator.

Effect of diffusion on interfacial properties of polyurethane-modified asphalt–aggregate using molecular dynamic simulation

Abstract In order to understand the diffusion behavior of polyurethane (PU) in asphalt and the adhesion between modified asphalt and aggregate, the diffusion system of PU-modified asphalt was studied by molecular dynamics simulation software. Asphalt molecular model, PU molecular model, and PU-modified asphalt molecular model were established, respectively, and were geometrically optimized. The interface model between original asphalt molecule and aggregate, modified asphalt molecule and aggregate, PU molecule and asphalt molecule are established. The diffusion coefficient is calculated from the mean square displacement curve of asphalt and PU, so as to characterize the diffusion ability of asphalt and PU. The adhesion between modified asphalt and aggregate is characterized the interface energy between modified asphalt and aggregate. The results show that the molecular movement of the two substances is relatively active, and the micro-holes in the system structure can be filled in a short time. The interface energy between PU-modified asphalt and aggregate is more significant than that between original asphalt and aggregate. PU-modified asphalt has good diffusion ability and better adhesion with aggregate.

Study on the compatibility between polyurethane and asphalt based on experiment and molecular dynamics simulation

Compatibility between asphalt and polyurethane (PU) additives is the most challenging issue affecting the performance of PU modified asphalt. This study aims to investigate the influence of shearing temperature and PU content on compatibility between PU and asphalt via experiments and molecular dynamics (MD) simulation. Herein, the molecular models of base asphalt, PU molecules, and PU/asphalt blends were first constructed in Materials Studio (MS) software. Based on a reasonable model, the influence of shearing temperature on the storage stability of PU modified asphalt was measured by calculating the solubility parameters (δ) and diffusion coefficient. In addition, the effect of PU content on the compatibility of PU and asphalt was evaluated through cohesive energy density (CED), hydrogen bonding, and radial distribution function (RDF). Finally, the simulation results were compared with results from the segregation test and fluorescence microscope (FM). The simulation results indicate that PU and asphalt obtain optimal compatibility when the temperature is 135 °C, at which the diffusion coefficient of PU modified asphalt is enhanced significantly. The CED of modified asphalt is enhanced with the increase of PU content. Meanwhile, PU shows a significant effect on the RDF of each asphalt component. All these changes in asphalt molecules demonstrate that PU plays a positive role in improving the tightness of asphalt molecular structure, and the optimal content is 15 wt%. The simulation results are consistent with experimental results.

Thermosetting characteristics and performances of polyurethane material on airport thin-overlay

The slow curing speed of traditional cement materials for airport pavement maintenance tended to cause unacceptable delays on the daily operations of airport aircraft. It was indispensable to select organic polymer materials to achieve rapid maintenance effect with high quality. At present, polyurethane had been adopted to achieve special demands for functional pavements. However, the application of polyurethane on rapid thin-overlay maintenance technology for airport pavement had not been researched extensively and there were also no standardized material design and construction procedures. This research conducted investigations on the thermosetting characteristics, component optimization and performance evaluation of polyurethane as rapid thin-overlay maintenance material for airport concrete pavement. First, the effects of micro-phase separation with different component ratios on polyurethane binder were analyzed. Three kinds of polyols were compared and selected comprehensively with corresponding optimal content ratio. Then, the thermosetting characteristics of polyurethane binder were evaluated, in terms of curing duration and curing temperatures. The curing process model of polyurethane molecules with gelation point was illustrated. The optimum polyurethane binder content was determined according to the properties of polyurethane-bonded mixtures and the optimal interlayer structure of the PUM composite overlay was considered. The characteristics of cement concrete and polyurethane-bonded mixture were compared, including mechanical property, durability and permeability. Finally, the internal structural details of cement concrete and polyurethane-bonded mixture were reconstructed and analyzed through X-ray CT scan. This research promoted the application potential of polyurethane as the rapid maintenance material with thin-overlay technology for airport pavement.

Modification of asphalt using polyurethanes synthesized with different isocyanates

To study the effect of isocyanates on the properties of polyurethane (PU) modified asphalt, three kinds of polyurethane with different hard segments were synthesized, by the reaction of polyethylene adipate (PEA) with diphenylmethane diisocyanate (MDI), toluene diisocyanate (TDI) and polyaryl polymethylene isocyanate (PAPI), respectively. These three kinds of polyurethane were used to modify the asphalt and study the effects of isocyanate on the performance of polyurethane modified asphalt by experiments. The Fourier transform infrared spectrometer (FTIR), and the gel permeation chromatography (GPC) were used to analyse PU samples. The dynamic shear rheology (DSR), bending beam rheology (BBR), multiple stress creep test (MSCR), Fourier transform infrared spectroscopy (FTIR), atomic force microscope (AFM), and differential scanning calorimetry (DSC) were used to research rheological properties, modification mechanism and microstructure of the asphalts, respectively. The results show that isocyanates influence the structure of polyurethane molecules, the distribution of soft and hard segments and the content of hard segments, and affect the distribution of asphaltenes in asphalt, resulting in different modification effects on asphalt. Of the three isocyanates, the PU synthesized by TDI provides the best improvement to the asphalt in terms of resistance against permanent deformations, low-temperature property and storage stability. Improvement effects of PU synthesized by PAPI on resistance against the permanent deformations and storage stability are better than that of MDI, but the effects on low-temperature property are worse with that of MDI.

Mechanical performance analysis of polyurethane‐modified asphalt using molecular dynamics method

AbstractIn this study, the mechanical performance of polyurethane (PU)‐modified asphalt was investigated. To this end, the molecular dynamics method was adopted to study the influence of the PU modifier on the compatibility, mechanical properties, and structure of asphalt. Using the Materials Studio software, a four‐component molecular model of asphalt, a PU molecular model, and an asphalt–PU mixed system model were constructed, and the molecular density and glass transition temperature () were used to verify the performance of the aforementioned models. Molecular dynamics simulations of the three molecular models were conducted under different temperatures, and the solubility parameter (), interaction energy, mechanical properties, and radial distribution functions (RDFs) were obtained. The results showed that at 413.15 K (140°C), the difference between the solubility parameters of the asphalt and PU molecules () is the smallest, and their interaction reaches the most optimal phase state. The effects of the PU modifier on the Young's modulus, bulk modulus, and shear modulus of asphalt were studied. Finally, the RDF analysis showed that the PU modifier has a direct effect on the degree of swelling and dispersion between the aromatic–aromatic and saturate–saturate components in the asphalt, reducing the aggregation of both molecules. This verifies the PU modification effect.

Synthesis and properties of novel triazine-based fluorinated chain extender modified waterborne polyurethane hydrophobic films

A novel triazine-based fluorinated diol, CC-F, was synthesized from cyanuric chloride (CC), octafluoropentanol (OFP), and ethanolamine (MEA). Subsequently, a series of fluorinated waterborne polyurethanes (CC-FPUF-n, n expressed as mass percentages of CC-F in product formula) were synthesized using CC-F as the chain extender. The chemical structure of the product was verified using the Fourier transform infrared (FTIR) spectroscopy and nuclear magnetic resonance (NMR) spectroscopy techniques. The influence of the CC-F contents on the properties of the latex particles, surface properties, thermal stabilities, and mechanical properties of CC-FPUF films was determined using the transmission electron microscopy (TEM), dynamic light scattering (DLS), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), atomic force microscopy (AFM), water contact angle (WCA), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and X-ray diffraction (XRD) techniques. Mechanical tests were also conducted for the same. The results revealed that the hydrophobic and mechanical properties of the CC-FPUF films were improved. Water contact angle and tensile strength values of the CC-FPUF-8 film were 125.8° and 36.63 MPa, respectively, which were, respectively, 34.1° and 24.47 MPa higher than those of the CC-FPUF-0 film. Thus, the embedding of CC-F into polyurethane molecules could significantly improve the hydrophobic and mechanical properties of the waterborne polyurethane films. Therefore, these novel fluorinated waterborne polyurethanes can be potentially used for hydrophobic coatings in the future.

Polycaprolactone-based biodegradable acrylated polyurethanes: Influence of nanosilica amount on functional properties

A series of nontoxic acrylated waterborne polyurethane/silica hybrid composites were synthesized from 1,6-hexamethylene diisocyanate (HDI), polycaprolactone diol (PCL), dimethylolpropionic acid (DMPA), a mixture of 3-aminopropyltriethoxysilane (APTES) and 2-hydroxyethyl methacrylate (HEMA) as chain extender. To control crosslink density the mono-functional HEMA was incorporated into the biodegradable polyurethanes. Different amounts of nanosilica were incorporated into acrylic-based polyurethanes to prepare polyurethane/silica hybrid composites. The structures of the acrylated waterborne polyurethane/silica hybrid composites were characterized by Fourier-transform infrared spectroscopy (FTIR), 1H NMR,13C NMR analysis and scanning electron microscopy (SEM). The effect of the amount of nanosilica on the thermal properties of polyurethane nanocomposite films was investigated by means of thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). Wide-angle X-ray scattering (WAXS) was used to investigate the degree of crystallinity of PCL as a soft segment into polyurethane hybrid composites.It is established that all samples containing PCL as a part soft segment with different silica loading are crystallisable polymers. The results from WAXS analysis have shown that the highest degree of crystallinity (37%) is reached in polyurethanes based on 1 wt% content of Aerosil OX50.The highest crystallization enthalpy (ΔHc) value for the sample with 1% nanosilica was 9.77 J/g confirmed by DSC analysis. The decrease of crystallinity of the PCL soft segment in polyurethanes indicates that the restriction of the crystallization of the PCL soft segment depends on the silica content. The incorporation of nanosilica into waterborne polyurethanes increases the thermal stability of the hybrid composite films. It was found that greater thermal and mechanical properties of waterborne polyurethane-silica hybrid composites were obtained due to a condensation process between triethoxysilane groups in the side chains of polyurethane molecules and silanols group on the surface of nanosilica.