Isophorone Diisocyanate Research Articles

Fully self-healable, highly stretchable, and anti-freezing supramolecular gels for energy-harvesting triboelectric nanogenerator and self-powered wearable electronics

Deformable energy-harvesting devices that are self-repairable and possess broad working temperatures remain a challenge for autonomous flexible electronics. Herein, the self-healable, stretchable, and anti-freezing entirely gel-based triboelectric nanogenerator (TENG) with a wide working temperature range from − 40 to 80 °C is reported in this study. Initially, an electrode gel was prepared by mixing poly(lipoic acid) with supramolecular crosslinkers of Fe3+ and phytic acid (PA), and the conductive polymer poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) was added. Secondly, a triboelectric gel was synthesized using amino- and hydroxy-terminated poly(dimethylsiloxane) (PDMS) along with isophorone diisocyanate and silicone oil. These gel networks were constructed by supramolecular interactions of reversible physical bonds and able to contribute high stretchability up to 50 times strain with fast self-healability (4 min for electrode gel and 24 h for tribolayer gel). The resulting gel-based TENG maintained excellent performance even after 5000 cyclic operations and showed stable performance after multiple cut/self-healing processes. Its outputs were increased as it was biaxially stretched up to 150% strain to retain its elasticity, ensuring its applicability in flexible uses. Moreover, the energy-harvesting capability was verified to be applicable from − 40 to 80 °C. Last, the gathered energy from the gel-based TENG was demonstrated to power up commercial electronics.

Photocrosslinkable gelatin/collagen based bioinspired polyurethane-acrylate bone adhesives with biocompatibility and biodegradability

Hard or soft tissue adhesives have been presented as a promising candidate to replace traditional wound closure methods. However, there are mechanical strength problems in biological adhesives and biocompatibility problems in synthetic-based adhesives. At this point, we aimed to remove all these disadvantages and produce a single adhesive that contains all the necessary features and acrylate functionalized UV-curable polyurethane formulations were produced with high crosslink density, high adhesion strength, biocompatibility and injectable property for easy application as potential biomedical adhesives. Aliphatic isophorone diisocyanate (IPDI) was used as the isocyanate source and β-cyclodextrin was used for host-guest relationship with gentamicin by crosslinking. Proteins (gelatin (GEL), collagen (COL)) and PEGs of various molecular weight ranges (P200, P400, P600) were selected as the polyol backbone for polyurethane synthesis due to their multiple biological activities such as biocompatibility, biodegradability, biomimetic property. Several techniques have been used to characterize the structural, thermal, morphological, and various other physicochemical properties of the adhesive formulations. Besides, the possibility of its use as a hard tissue adhesive was investigated by evaluating the tissue adhesion strength in vitro and ex vivo via a universal testing analyzer in tensile mode. Corresponding adhesive formulations were evaluated by in vitro and in vivo techniques for biocompatibility. The best adhesion strength results were obtained as 3821.0 ± 214.9, and 3722.2 ± 486.8 kPa, for IPDI-COL-P200 and IPDI-GEL-P200, respectively. Good antibacterial activity capability toward Escherichia coli Pseudomonas aeruginosa, and Staphylococcus aureus were confirmed using disc diffusion method. Moreover, cell viability assay demonstrated that the formulations have no significant cytotoxicity on the L929 fibroblast cells. Most importantly, we finally performed the in vivo biodegradability and in vivo biocompatibility evaluations of the adhesive formulations on rat model. Considering their excellent cell/tissue viability, fast curable, strong adhesion, high antibacterial character, and injectability, these adhesive formulations have significant potential for tissue engineering applications.

Synthesis and research of polyfunctional silylureas used in electric deposition of tin-indium alloy

Polyfunctional silylureas were synthesized by the interaction of 3-aminopropyltriethoxysilane with isocyanates of various structures in an inert aromatic solvent. Commercially available diisocyanates such as isophorone diisocyanate, hexamethylene diisocyanate, 2,4-toluene diisocyanate were used as isocyanates. In this case, freshly distilled toluene was used as a solvent. The structures of the obtained compounds were confirmed by the data of IR and NMR1H spectroscopy. Using the synthesized compounds, formulations of compositions for electrodeposition of a tin-indium alloy on a copper wire were developed. The possibility of using silylureas of various structures as effective surfactants used in the electrodeposition of the tin-indium alloy is shown. The operational characteristics of the obtained wire were investigated, including the wire diameter, coating thickness, tensile strength, electrical resistance, and direct current electrical resistivity.

The Curing Reaction Rate of the Rocket Motor Liner Based on the Aging of a Curing System

AbstractIn this study, the hardening reaction speed of a rocket motor liner based on the Aging of a curing system comprised of a hardener and hardening catalyst was investigated. With the increasing Aging time of the curing system, the liner viscosity build‐up was accelerated. The raw material having the biggest impact on the hardening reaction of the curing system's liner was triphenylbismuth (TPB). Stirring isophorone diisocyanate and TPB form an activated complex, and the activated complex facilitates the urethane reaction. If TPB is ligand bound with isocyanate, it forms a TPB‐isocyanate complex. This is a type of TPB's oxide, and the formation of the activated complex is visible through changes in its color. In addition, lining hardening time can be adjusted by the Aging period of the curing system through used in this study, and the adhesive strength with the liner and propellant can be improved.

Rubber Seed Oil-Based UV-Curable Polyurethane Acrylate Resins for Digital Light Processing (DLP) 3D Printing.

Novel UV-curable polyurethane acrylate (PUA) resins were developed from rubber seed oil (RSO). Firstly, hydroxylated rubber seed oil (HRSO) was prepared via an alcoholysis reaction of RSO with glycerol, and then HRSO was reacted with isophorone diisocyanate (IPDI) and hydroxyethyl acrylate (HEA) to produce the RSO-based PUA (RSO-PUA) oligomer. FT-IR and 1H NMR spectra collectively revealed that the obtained RSO-PUA was successfully synthesized, and the calculated C=C functionality of oligomer was 2.27 per fatty acid. Subsequently, a series of UV-curable resins were prepared and their ultimate properties, as well as UV-curing kinetics, were investigated. Notably, the UV-cured materials with 40% trimethylolpropane triacrylate (TMPTA) displayed a tensile strength of 11.7 MPa, an adhesion of 2 grade, a pencil hardness of 3H, a flexibility of 2 mm, and a glass transition temperature up to 109.4 °C. Finally, the optimal resin was used for digital light processing (DLP) 3D printing. The critical exposure energy of RSO-PUA (15.20 mJ/cm2) was lower than a commercial resin. In general, this work offered a simple method to prepare woody plant oil-based high-performance PUA resins that could be applied in the 3D printing industry.

Scratch-healable automotive clearcoats based on disulfide polyacrylate urethane networks

We report a novel scratch-resistant and healable automotive clearcoat that can not only protect the substrate surface but also facilitate scratch repair. A self-healable disulfide polyurethane diol adduct (DSPUDA) was synthesized via step-growth polymerization with bis(4-hydroxyphenyl) disulfide, isophorone diisocyanate, and poly(tetrahydrofuran). The reversibility of bond cleavages and associations of the synthesized DSPUDA was quantified through nuclear magnetic resonance analysis, and its healing properties were confirmed using a universal testing machine and a rheometer. The material properties of clearcoats were tuned by varying the amounts of the DSPUDA added to prepared control clearcoats. The scratch resistances of the resultant clearcoats were assessed using an Amtec-Kistler car-wash tester and a gloss-meter, and their scratch-healing performances were evaluated using a micro-scratch tester and an optical microscope. In addition, the healing efficiency was quantitatively scrutinized using a nano-scratch tester and an atomic force microscope. The thermal properties of the clearcoat samples specifically, the thermal decomposition temperature, glass-transition temperature, and degree of crosslinking were characterized by thermogravimetric analysis, differential scanning calorimetry, and dynamic mechanical analysis, respectively. The mechanical properties of the clearcoat surfaces were investigated using nano-indentation and pendulum hardness tests. The healing efficiency and mechanical properties of the prepared clearcoats exhibited an inverse trade-off relationship. Nevertheless, optimizing the proportion of reversible disulfide bonds of the DSPUDA in the polyacrylate-based urethane networks not only resulted in superior scratch healing and scratch resistance but also maintained sufficient mechanical properties for the coatings to be used as automotive clearcoats.

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.

Tailoring the properties of waterborne polyurethanes by incorporating different content of poly(dimethylsiloxane)

A series of novel waterborne polyurethanes (WBPUs) was synthesized using α,ω-dihydroxypropyl poly(dimethylsiloxane) (PDMS), isophorone diisocyanate (IPDI), 2,2-bis-(hydroxymethyl) propionic acid (DMPA) and triethylamine (TEA). Different DMPA/PDMS molar ratio (from 0.2 to 0.7) and fixed –NCO/–OH molar ratio of 1.7, has been applied for the synthesis of six different WBPU films, without utilization of chain extension step during the synthesis. The structure of the prepared WBPUs was examined and confirmed by FTIR and NMR spectroscopy. The particle size of the prepared WBPU dispersions and molecular weight of WBPU films decrease with increasing DMPA content. In order to investigate the effect of the DMPA/PDMS ratio on thermal, mechanical and morphological properties, as well as the water resistance of the prepared WBPUs, diverse experimental techniques, such as thermogravimetric analysis, dynamic mechanical analysis, tensile tests, X-ray diffraction analysis (XRD), atomic force microscopy (AFM), scanning electron microscopy (SEM) and water contact angle measurements have been carried out. This research has shown that the incorporation of PDMS in WBPUs led to the appearance of microphase separation and provided surface hydrophobicity, good thermal and mechanical properties, which allow application of these WBPUs as coatings for various purposes.

Hydrophobic UV-Curable Powder Clear Coatings: Study on the Synthesis of New Crosslinking Agents Based on Raw Materials Derived from Renewable Sources.

Methods for the synthesis of urethane acrylates used as new crosslinking agents for hydrophobic UV-curable powder clear coatings were developed. In the synthesis of urethane acrylates, isophorone diisocyanate, glycerin, xylitol, polyethylene glycol and polysiloxane KF-6000, as well as 2-hydroxyethyl acrylate or 2-hydroxyethyl methacrylate, were used. In order to increase the functionality of urethane acrylates, glycerin and xylitol derived from renewable sources were introduced. The chemical structure of the urethane acrylates was verified by IR spectroscopy. UV-curable powder clear coatings were obtained through a combination of urethane acrylates with unsaturated polyester resins. The thermal behavior and crosslinking density were examined using DMA. The obtained coatings were evaluated by performing the following tests: roughness, gloss, scratch resistance, hardness, adhesion to steel and water contact angle. As part of this research, high hydrophobicity and scratch resistance of UV-curable powder clear coatings were developed, which are a VOC-free and economically attractive alternative method for low thermal resistance surface protection, such as for composites, wood and wood-based materials.

Hindered phenolic antioxidant passivation of black phosphorus affords air stability and free radical quenching

As an antioxidant, hindered phenol scavenges free radicals. Due to the oxidative degradation of black phosphorus (BP) in the presence of water and oxygen, free radical quenching of hindered phenol antioxidants can solve this issue and improve the environmental stability and flame retardant efficiency of BP. Herein, hydroxyl-modified BP (BP-OH) with active groups on the surface was obtained by hydroxylation, and then the hindered phenol antioxidant was grafted onto the surface of BP-OH through an isophorone diisocyanate bridging covalent reaction to obtain hindered phenol-modified BP (BP-HPL). The fire hazard of thermoplastic polyurethane (TPU) can be significantly reduced by introducing BP-HPL into TPU. Adding 2 wt% BP-HPL can reduce the heat release rate and total heat release values of TPU by 49.9% and 49.0%, respectively. In addition, the reductions in smoke volume and carbon monoxide production were also significant. Compared with BP-OH, the environmental stability of BP-HPL is significantly improved. This work provides a reference for the application of BP in the field of fire safety and simultaneously achieves the improvement of the environmental stability and flame retardant performance of BP.

Preparation of basalt fibers grafted with amine terminated urea-based oligomer and its application in reinforcing conventional glass ionomer cement

The purpose of this study was to improve interfacial interaction between basalt fibers (BF) and glass ionomer cement (GIC) matrix with grafting amine terminated urea-based oligomer (DIEDA) onto the surface of BF. The DIEDA-BF was prepared by the reaction between 3-aminopropyl- triethoxysilane (APS) modified BF with Isophorone diisocyanate (IPDI) and followed with ethylenediamine (EDA). The reaction was repeated to obtain three generations of DIEDA-BF which were marked as DIEDA-BF-G1, DIEDA-BF-G2, and DIEDA-BF-G3, respectively. X-ray photoelectron spectroscopy (XPS) was used to characterize DIEDA-BF. 3D morphology analysis was taken to investigate the variation of BF after being treated with EDA. Three-point bending-test, compressive strength (CS) test, and fracture toughness (FT) were used to evaluate the reinforcement effect of DIEDA-BF on commercial GIC (GC Fuji IX). Water sorption (WS) and solubility (SL) were measured according to the mass variation at fixed time intervals. The changes of flexural strength (FS) and modulus (FM) after water immersion were used to evaluate the water-aging resistance of DIEDA-BF reinforced GIC. Pure GIC and APS reinforced GIC (APS-GIC) were used as double control groups. The XPS analysis indicated that DIEDA was successfully grafted onto the surface of BF. 3D morphology analysis revealed that BF could be corroded in EDA, thus DIEDA-BF-G3 had lower N content on the surface than DIEDA-BF-G2. The results of mechanical tests showed that DIEDA-BF-G1 and DIEDA-BF-G2 had the best reinforcement effect. The DIEDA-BF-G1 reinforcement GIC (DIEDA-BF-G1-GIC) was chosen for WS, SL, and water aging resistance test further. The results showed that all fiber reinforced GICs had higher WS than pure GIC, and the relationship in SL between fiber reinforced GICs and pure GIC varied with immersion time. The FS of DIEDA-BF-G1-GIC decreased after one week of water immersion, and had no variation after prolonging the immersion time. After three months of water immersion, DIEDA-BF-G1-GIC still had much higher FS than pure GIC and APS-BF-GIC. DIEDA could improve the interfacial interaction between BF and GIC matrix. After long term of water immersion, DIEDA-BF reinforced GIC still had FS higher than 50 MPa, which even met the ISO requirement in FS for dental resin composite. Therefore, GIC/DIEDA modified BF composite had potential to be used in stress bearing areas in dentistry.

Construction of Mechanically Reinforced Thermoplastic Polyurethane from Carbon Dioxide-Based Poly(ether carbonate) Polyols via Coordination Cross-Linking.

Using carbon dioxide-based poly(propylene ether carbonate) diol (PPCD), isophorone diisocyanate (IPDI), dimethylolbutyric acid (DMBA), ferric chloride (FeCl3), and ethylene glycol (EG) as the main raw materials, a novel thermoplastic polyurethane (TPU) is prepared through coordination of FeCl3 and DMBA to obtain TPU containing coordination enhancement directly. The Fourier transform infrared spectroscopy, 1H NMR, gel permeation chromatography, UV−Vis spectroscopy, tensile testing, dynamic mechanical analysis, X-ray diffraction, differential scanning calorimetry, and thermogravimetric analysis were explored to characterize chemical structures and mechanical properties of as-prepared TPU. With the increasing addition of FeCl3, the tensile strength and modulus of TPU increase. Although the elongation at break decreases, it still maintains a high level. Dynamic mechanical analysis shows that the glass-transition temperature moves to a high temperature gradually along with the increasing addition of FeCl3. X-ray diffraction results indicate that TPUs reinforced with FeCl3 or not are amorphous polymers. That FeCl3 coordinates with DMBA first is an effective strategy of getting TPU, which is effective and convenient in the industry without the separation of intermediate products. This work confirms that such Lewis acids as FeCl3 can improve and adjust the properties of TPU contenting coordination structures with an in-situ reaction in a low addition amount, which expands their applications in industry and engineering areas.

Flame Retardant Waterborne Polyurethanes: Synthesis, Characterization, and Evaluation of Different Properties

A series of flame retardant waterborne polyurethanes (WBPUs) with varying NCO:OH mole ratio, i.e., isocyanate:hydroxyl groups, was synthesized using phosphorus-based polyester polyol and isophorone diisocyanate (IPDI). The phosphorus moiety was kept in the polymeric chain, which improves flame retardancy of the WBPU films. The prepolymer mixing process was adopted for the synthesis route of WBPU systems. The presence of structural-functional groups was confirmed by Fourier transform infrared spectroscopy and nuclear magnetic resonance spectroscopy. The thermal stability and percentage char yield were observed by TGA analysis. As a consequence of the existence of phosphorous moiety, these WBPUs also exhibit flame retardancy, which was examined by limiting oxygen index (LOI) and UL-94 test. All the samples show an increment in thermal stability with an increase in NCO:OH ratio. Maximum flame retardancy was obtained in FWP5 and FWP6 systems with LOI value of 32%.

Investigation of isophorone diisocyanate microcapsules to improve self-healing properties and sulfate resistance of concrete

Sulfate attack causes internal cracking of concrete and affects the durability of concrete structures. The durability of concrete under sulfate attack is crucial to structural safety and serviceability. Microcapsules can self-heal microcracks in concrete and improve its durability. Microcapsules with isophorone diisocyanate (IPDI) as the healing agent and paraffin wax, polyethylene wax, and nano silica as shells were prepared to improve the sulfate resistance and self-healing properties of concrete. The mass loss, mechanical properties, impermeability, and pore size distribution of the concrete after sulfate dry-wet cycles were determined. Ultrasonic testing was used to evaluate concrete sulfate resistance and self-healing properties, as a prominent nondestructive testing technique. The results showed that the addition of microcapsules significantly improved the sulfate resistance and self-healing properties. Concrete containing nano silica/paraffin wax/polyethylene wax encapsulated IPDI microcapsules exhibited good sulfate resistance and self-healing properties. Scanning electron microscopy revealed that concrete containing microcapsules exposed to sulfate attack produced healing products with a mesh-like structure in the pores after a 14-d self-healing. These healing products can improve microstructure and self-healing properties.

A Robust Self-healing Polyurethane Elastomer Enabled by Tuning the Molecular Mobility and Phase Morphology through Disulfide Bonds

Elastomer with outstanding strength, toughness and healing efficiency is highly promising for many emerging fields. However, it is still a challenge to integrate all these beneficial features in one elastomer. Herein, an asymmetric alicyclic structure adjacent to aromatic disulfide was tactfully introduced into polyurethane (PU) elastomer. Specifically, such elastomer (PU-HPS) was fabricated by polycondensing polytetramethylene ether glycol (PTMEG), isophorone diisocyanate (IPDI) and p-hydroxydiphenyl disulfide (HPS) via one-pot method. The molecular mobility and phase morphology of PU-HPS can be tuned by adjusting the HPS content. Consequently, the dynamic exchange of hydrogen and disulfide bonds in the hard segment domains can also be tailored. The optimized sample manifests outstanding tensile strength (46.4 MPa), high toughness (109.1 MJ m-3), high self-healing efficiency of fractured samples (90.3 %), complete scratch recovery (100 %) and good puncture resistance. Therefore, this work provides a facile strategy for developing robust self-healing polymers.

Structural and Rheological Properties of Nonedible Vegetable Oil-Based Resin.

Jatropha oil-based polyol (JOL) was prepared from crude Jatropha oil via an epoxidation and hydroxylation reaction. During the isocyanation step, two different types of diisocyanates; 2,4-toluene diisocyanate (2,4-TDI) and isophorone diisocyanate (IPDI), were introduced to produce Jatropha oil-based polyurethane acrylates (JPUA). The products were named JPUA-TDI and JPUA-IPDI, respectively. The success of the stepwise reactions of the resins was confirmed using 1H nuclear magnetic resonance (NMR) spectroscopy to support the Fourier-transform infrared (FTIR) spectroscopy analysis that was reported in the previous study. For JPUA-TDI, the presence of a signal at 7.94 ppm evidenced the possible side reactions between urethane linkages with secondary amine that resulted in an aryl-urea group (Ar-NH-COO-). Meanwhile, the peak of 2.89 ppm was assigned to the α-position of methylene to the carbamate (-CH2NHCOO) group in the JPUA-IPDI. From the rheological study, JO and JPUA-IPDI in pure form were classified as Newtonian fluids, while JPUA-TDI showed non-Newtonian behaviour with pseudoplastic or shear thinning behaviour at room temperature. At elevated temperatures, the JO, JPUA-IPDI mixture and JPUA-TDI mixture exhibited reductions in viscosity and shear stress as the shear rate increased. The JO and JPUA-IPDI mixture maintained Newtonian fluid behaviour at all temperature ranges. Meanwhile, the JPUA-TDI mixture showed shear thickening at 25 °C and shear thinning at 40 °C, 60 °C and 80 °C. The master curve graph based on the shear rate for the JO, JPUA-TDI mixture and JPUA-IPDI mixture at 25 °C, 40 °C, 60 °C and 80 °C was developed as a fluid behaviour reference for future storage and processing conditions during the encapsulation process. The encapsulation process can be conducted to fabricate a self-healing coating based on a microcapsule triggered either by air or ultra-violet (UV) radiation.

Synthesis, characterization and dispersion stabilities of novel ionic and nonionic diol modified waterborne polyurethane dispersions with different polyols

Several high solid content waterborne polyurethane dispersions (WPUDs) with the combination of anionic and nonionic stabilization were synthesized by polyaddition reaction using isophorone diisocyanate (IPDI), trimethylol propane (TMP) and 1,6-hexanediol (HDO) as the hard segments, polypropylene glycol with molecular weight of 2000 Da (PPG-2000), and polytetramethylene ether glycol with molecular weight of 2000 Da (PTMG-2000) as the soft segments, anionic diol dimethylol propionic acid (DMPA) and nonionic diol Y-mer N 120 (NID) as the donors of hydrophilic groups. The chain extension reaction between residual NCO groups was made by using hydrazine (HYD). The effects of the combination of anionic and nonionic monomer and macrodiol types on the performance of the WPUDs were studied in terms of particle size distribution and dispersion stability. The results showed that the WPUDs exhibited narrow particle size distribution, good appearance and good mechanical properties.

One-pot and solvent-free synthesis of castor oil-based polyurethane acrylate oligomers for UV-curable coatings applications

Due to the complex chemical modification, harsh synthesis conditions and imperative post-treatment, the industrial products of vegetable oil-based polymers are very rare. In this study, castor oil-based polyurethane acrylic resin (COPUA) was synthesizled by one-pot method from castor oil (CO), isophorone diisocyanate (IPDI), hydroxyethyl acrylate (HEA) and isobbornyl acrylate (IBOA). 1H NMR and FT-IR measurements were employed to verify the successful preparation of COPUA. Various UV curable films were prepared by mixing non-treated COPUA, photoinitiator (PI-1173), mono-functional active diluent hydroxyethyl methacrylate (HEMA) or bifunctional active diluent tripropylene glycol diacrylate (TPGDA). The mechanical performances of the cured films were studied. Besides, DMA and TGA analyses were used to determine the dynamic thermodynamic performances and the thermal stability of the cured films. As a result, the pure COPUA cured film exhibited excellent thermal stability, storage modulus (421 MPa at 25 °C), tensile strength (9.87 MPa) and high glass transition temperature (60.3 °C). The cross-linking density of films improved with increasing the content of active diluent, resulting in excellent overall performances. In addition, all films possessed excellent hardness, adhesion, solvent resistance and flexibility. In this study, it provides a green and environmentally friendly strategy for the synthesis of vegetable oil-based polymers, reducing our chemical dependence on petrochemical energy.

Hard, tough and fast self-healing thermoplastic polyurethane

It's necessary to develop self-healing polymers, which will significantly improve the safety and service life of artificial materials. Although extensive research efforts have been devoted to the field, it is still a challenge to synthesize hard and tough polymers, which own self-healing ability under mild conditions. In this work, we fabricated a hard and tough thermoplastic polyurethane (TPU, PCL-HM) and the wound of PCL-HM can be quickly healed under mild conditions (50 °C). Comprehensive characterization results suggest that the Young's modulus, tensile strength and elongation at break of PCL-HM can reach 76 MPa, 11.8 MPa and 841%, respectively, which is better than most recently reported TPUs. PCL-HM prepared with aromatic disulfide bonds as dynamic covalent bonds, polycaprolactone diol (PCL-2000) as soft segment, isophorone diisocyanate (IPDI) and dicyclohexylmethane-4,4′-diisocyanate (HMDI) as hard segment, can quickly recover to 92% of its original tensile strength within 1 h at 50 °C. Due to the better segment movement and looser packing of aromatic disulfide in PCL-HM, the PCL-HM displays better healing properties compared with other types of TPUs (PCL-I, PCL-H, PCL-M, PCL-HM′) prepared in this work. In addition, the fast healing properties of PCL-HM under mild conditions endow it with great application prospects in the field of protective coatings. The successful preparation of PCL-HM also provides a new idea for the synthesis of hard and tough TPU.

Hydrophobic polyurethane powder clear coatings with lower curing temperature: Study on the synthesis of new blocked polyisocyanates

The method of the synthesis of blocked polyisocyanates (bPIC) used as a crosslinking agent for hydrophobic and low temperature curing powder coatings was developed. In the synthesis of polyisocyanates (PIC) isophorone diisocyanate, glycerine, xylitol, polyethylene glycol and polysiloxane KF-6000 as well as two different blocking agents, i.e. acetone oxime and butanone oxime were used. The chemical structure of the obtained blocked polyisocyanates was confirmed by IR and NMR spectroscopy and the molecular mass distribution was investigated using gel permeation chromatography (GPC). The thermal behavior and the deblocking process were investigated by means of TG, DSC and DMA. The obtained coatings were evaluated by performing the following tests: roughness, gloss, scratch resistance, hardness, adhesion to the steel and water contact angle. As part of this research, the hydrophobic and high scratch resistance coatings cured at 150 °C were developed.