Search

Passive cooling technology is currently a hot research topic because it can achieve cooling without external energy input, significantly reduce cooling costs and mitigate global warming. At present, passive cooling technology is mainly used in construction, transportation, electronic equipment, and other fields, but most passive cooling materials do not have gas barrier performance, which limits the application of passive cooling technology in inflatable structures such as gas film buildings, blimp bladders and other fields, so a material that has both passive cooling and gas barrier performance is needed. In this paper, PXTPU composites were prepared by melt blending mica‐TiO2 with thermoplastic polyurethane (TPU). PXTPU not only achieves passive cooling above 10°C with the excellent reflectivity of TiO2 in mica‐TiO2, but also achieves 61.1% or even 74.5% enhancement of gas barrier capacity with the high orientation of lamellar mica in mica‐TiO2. In addition, PXTPU also exhibited good thermal stability and mechanical properties exceeding 31.2 MPa breaking strength and 210.6% breaking elongation. Therefore, PXTPU composites show great potential in inflatable structures for outdoor work, expanding the application field of passive cooling technology. [ABSTRACT FROM AUTHOR]

Most self‐healing materials based on noncovalent bonding suffer from poor mechanical performance, which largely limits their further application. Herein, we designed and synthesized robust and healable polymers that can be healed under heating. They consist of a linear and three‐arm branched polyurethane mixture with triazole ligand end groups that are noncovalently linked through Fe–triazole interaction. The three‐arm branched polyurethane in the polymer mixture would imply parts of Fe‐triazole coordination bonds were replaced by covalent bonds and, as a consequence, yield materials with improved mechanical properties. Additionally, the mechanical properties of resulting polymers can be tuned by the number of Fe–triazole supramolecular crosslinks. Due to the dynamic nature of Fe–triazole interaction, all the metallopolymers exhibit excellent healable efficiency (over 90%) based on toughness. © 2020 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

To prepare a robust material with high self-healing capability under ambient conditions is still a great challenge. Herein, a novel self-healing polyurethane is developed via a dual-dynamic network design, in which multiple H-bonding and metal-coordinated bonds (zinc–imidazole interaction) were incorporated into a polyurethane matrix. Benefiting from the dual-dynamic network, the synthesized metallopolymers exhibit excellent mechanical properties, such as high tensile strength (from 6.68 MPa to 14.38 MPa), excellent stretchability (about 2000%) and superior toughness (from 55.61 MJ m−3 to 96.21 MJ m−3). Moreover, these metallopolymers show good self-healing capability. After healing under ambient conditions for 48 hours, the tensile strength and strain at break of PU-IZ/Zn-0.50 can reach up to 7.13 MPa and 1800%, respectively. The dual-dynamic crosslinked metallopolymers might provide a novel approach to design tough and self-healable materials for various industrial applications. [ABSTRACT FROM AUTHOR]

A dual crosslinked self‐healing polyurethane was prepared with robust mechanical properties through the dynamic reversible pyridine‐Fe3+ coordination bonds and Diels–Alder (DA) covalent bonds dual crosslinking strategy. Moreover, the mechanical properties and self‐healing ability of polyurethane can be tuned readily by different ratio of the coordination bonds and DA bonds. Under external load, the coordination bonds serve as sacrificial bonds are broken to dissipate energy, the DA bonds can keep the shape of sample. With the coordination bonds participation, the damaged samples can be healed under moderate heating treatment or with the aid of FeCl3 solution. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019, 57, 2228–2234 [ABSTRACT FROM AUTHOR]

Recently, self‐healing polymers have been one of the most intriguing academic fields due to the fact that they can increase their service lives and reduce the amount of waste. Here we designed and synthesized a novel telechelic polyurethane with dopamine (DA) end groups that are coordinated with Ca2+ to form dynamic non‐covalent bonds. The tensile stress of the designed polyurethanes increases with increase in the amount of metal cation added, while the strain at break slightly decreases. Rheological tests show that the ionic coordination between Ca2+ and catechol can dynamically break and recombine under the stimulation of seawater, endowing the polymer with superior self‐healing properties (up to 84% based on toughness). Therefore, the seawater‐triggered self‐healable, super tough polyurethane presented here is very intriguing as it has many potential applications especially in the marine environment. © 2019 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

The morphology and helium-barrier properties of thermoplastic polyurethane (TPU)/ethylene-vinyl alcohol (EVOH) blends with and without dicumyl peroxide (DCP) were investigated by melting blending. A lamellar dispersion of EVOH with good helium-barrier properties was observed in the TPU matrix with DCP. The evolution of the morphology of the blends is mainly related to the variation of the viscosity ratio between the dispersed phase and the matrix phase. Compared with pure TPU, lamellar morphology increased the helium-barrier properties of the TPU/EVOH (60/40) blend by as much as 10-fold. We also explored the effects of composition, DCP content, and blending sequence on the morphology and helium-barrier properties of the TPU/EVOH blends. The morphology of the blends ranged from a droplet-matrix to a lamellar structure. We determined the optimum amount of DCP to improve the helium barrier of the blends. The helium-barrier properties of the blends prepared by direct blending were superior to those of the blends prepared by two-segment blending, and the blends prepared by direct blending exhibited a well-developed lamellar morphology. We compared the permeability of the samples with the theoretical results to explain the relationship between morphology and helium-barrier properties. POLYM. ENG. SCI., 56:922-931, 2016. © 2016 Society of Plastics Engineers [ABSTRACT FROM AUTHOR]

Polyurethane elastomers (PUEs) based on 4,4′-diphenylmethane diisocyanate (MDI), 1,4-butanediol (BDO) and two kinds of aliphatic polycaprolactone (PCL) diols with molecular weight of 1000 Da and 2000 Da have been synthesized and melt-blended with polycarbonate (PC). The compatibility of PC and PUEs was investigated by differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA) and scanning electron microscopy (SEM). The results indicated that the glass transition temperature ( T g) of PC decreased by 0-40°C when 0-10 wt % of PUEs incorporated into the PC matrix. Phase separation in the blends was not detected by means of DSC characterization, but measurements of DMA and SEM indicated that phase separation existed in the blends of PC and PUEs synthesized with 1000 Da PCL-diol. As for PUEs/PC blend in which 2000 Da PCL-diol as PUEs' soft segments, it turned from completely compatible to partially when the NCO/OH ratio for the PUEs prepolymer was increased from 2 : 1 to 4 : 1. The compatibilities of PC and PUEs were greatly influenced by the molecular weight of polyols and the ratio of NCO/OH in the PUE prepolymer, higher molecular weight of polyols and lower NCO/OH ratio resulted in better compatibility. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012 [ABSTRACT FROM AUTHOR]

Abstract: Compatibilized blends of poly(vinylidene fluoride) (PVDF) and thermoplastic polyurethane (TPU) were developed using maleated PVDF (PVDF-g-MA). Excellent compatibilization between PVDF and TPU was demonstrated by rheological, morphological, and mechanical measurements. The introduction of PVDF-g-MA into the PVDF/TPU blends caused an increase in viscosity and storage modulus. Much finer morphologiy was clearly observed by SEM. The tensile tests showed that the tensile strength and ultimate elongation achieved a significant improvement with addition of PVDF-g-MA. [Copyright &y& Elsevier]

We developed a polyurethane material has an excellent self-healing ability as well as mechanical strength. This system was achieved based on dual-crosslinked Diels-Alder (DA) covalent bonding reaction. The first cross-linking point is realized by the DA bonding of polyurethane chain. Because of grafted maleimide group, the maleimide functionalized GO (mGO) sheets can be regarded as analogous cross-linker and provide the second cross-linking point in the system. We investigated and compared the effects of as-produced GO and mGO loading and maleimide functionalization on the mechanical properties and healing efficiency of composites. As a result, compared with those of the pure polyurethane and composites filled with the GO, such maleimide functionalization is found to effectively improve the compatibility between mGO and polymer matrix, increasing mechanical properties and healing efficiency of polyurethane composites. The mechanical properties and healing efficiency of polyurethane can be tuned readily by varying mGO concentration. The healing efficiencies were up to 99% for the nanocomposite containing mGO. These results confirm maleimide functionalization improved dispersion and interfacial interaction between the fillers and the polyurethane matrix. [ABSTRACT FROM AUTHOR]

Abstract In this work, multifunctional polyurethane-based phase change materials with zinc oxide (ZnO) and graphene aerogel (GA) were prepared through facile impregnation. ZnO and GA improved the latent heat of the system from 86.8 J/g to 108.1 J/g for the heterogeneous nucleation and chemical mitigations. Furthermore, the photo-/electro-thermal energy conversion efficiency of the system with ZnO and GA is 80.1%, 84.4%, respectively, for the efficient light absorption of ZnO and GA as well as the electrical conductivity of GA. The as-prepared materials with high latent heat, excellent form-stability, remarkable thermal stability as well as reliability, efficient light-/electro-thermal energy conversion, have great prospects for applying in energy harvesting, conversion and storage devices like solar heater, smart textile and greenhouse. Graphical abstract GA serves as supporting skeleton, light absorbent, electricity conductive pathways and thermal barrier. While ZnO acts as nucleation agent, crosslinking agent as well as UV absorbent. Thus, the system with high latent heat is form-stable, light/electro responsive and thermal stability. fx1 Highlights • The air-dried GA serves skeleton and electricity conductive pathways. • ZnO improved the performance of system for heterogeneous nucleating and effective UV absorption. • The thermal stability was improved a lot for the thermal barrier of GA. [ABSTRACT FROM AUTHOR]

Abstract In this study, polyurethane-based solid-solid phase change materials with halloysite nanotubes (HNTs)-hybrid graphene aerogel (GA) have been fabricated through vacuum impregnation. As a supporting skeleton, the air-dried HNTs-GA with continuous porous structure endows the system with excellent light-thermal (η = 75.6%) and electro-thermal (η = 67.2%) energy conversion and storage ability. HNTs not only improve the reduction degree of GA, but also enhance the latent heat of the system through heterogeneous nucleation effects. The synthesized materials with high latent heat, excellent thermal reliability and stability, remarkable light/electro-thermal energy conversion ability show great potentials in applications of energy storage devices. Graphical abstract When exposed to the solar heating or supplied by a power, the system could absorb the light quickly and convert it to heat, or transfer the electro to thermal energy, which make the crystals in the system to melt and the thermal energy is stored. Image 1 [ABSTRACT FROM AUTHOR]

Graphical abstract The crystallization of PEG parts could be continuously improved with the decrease of GO size owing to the increase of heterogeneous nucleation density and mitigation of the chemical and physical restrictions of segments. Highlights • The crystallization of PEG in system get a lot enhancement. • The phase change performance of the system is GO size-dependent. • The interaction among crosslinking network plays an important role. Abstract In this study, the size effects of graphene oxide (GO) sheets on the phase change behaviors of crosslinking polyurethane system have been investigated. The experimental results show that phase change performance of the system is connected closely to the heterogeneous nucleation, physical confinements from GO and interactions in the system, which are inseparable from the specific surface area and the contents of oxygen functional groups depending on the size. This work has a theoretical significance to design thermal energy storage materials with desired properties. [ABSTRACT FROM AUTHOR]

Crosslinking polyurethane-based solid-solid phase change materials with in situ reduced graphene oxide (GO) sheets were fabricated by a facile solvothermal treatment. GO sheets could give their full play to the enhancement of the system, which can endow the system with outstanding form-stability over 100 °C for the synergistic effect with hexamethylene diisocyanate biuret, and remarkable light-thermal conversion efficiency up to 78.7% due to the simultaneous in situ reduction of GO. The phase change enthalpy increases to 127.3 J/g from 86.8 J/g with 3.8 wt% GO for the nucleation and alleviating effects in the system. Meanwhile, the system has improved thermal stability and favorable thermal reproducibility. Therefore, the synthesized materials with comprehensive properties would be perspective to be used in energy storage devices such as solar energy collector system. [ABSTRACT FROM AUTHOR]

Polyurethane-based solid-solid phase change materials were first synthesized using polyethylene glycol (PEG) and hexamethylene diisocyanate biuret (HDIB), and the influence of halloysite nanotubes (HNTs) on this system was investigated. HNTs can not only serve as crosslinking agent in synergy with HDIB, which reinforces the solid-solid phase change properties of the system that has no leakage even at the temperature that 40 °C higher above the melting temperature of PEG, but also greatly improve the latent heat of the system from 86.8 to 118.7 J/g, as a result of heterogeneous nucleation effect, which can make up partial latent heat loss caused by crosslinking. Also, HNTs endows the system with excellent thermal stability, where the temperature at 5% weight loss is increased by 53 °C. The synthesized PCMs have extensive applying prospects in thermal energy storage fields. [ABSTRACT FROM AUTHOR]

Graphene oxide (GO) crosslinked polyurethane-based solid–solid phase change materials, composed by polyethylene glycol (PEG) and hexamethylene diisocyanate biuret (HDIB), were fabricated in-situ polymerization. GO sheets could support the excellent solid framework at 100 °C and prevent the leakage of melt in synergy with HDIB by physical and chemical crosslinking network. Meanwhile, GO sheets act as heterogeneous nucleation agents that make the crystallization temperature of system rise to 34.0 °C from 24.8 °C with 14.5 wt‰ GO. Whereas, GO have little effect on the latent heat, which may be an offset of the nucleation and confinement. Besides, the tensile strength increased to 21. 7 from 10.2 MPa with 14.5 wt‰ GO and Young’s modulus increased to 471.5 from 180.1 MPa for 44.6 wt‰ one. Also, the strain at break has a slight promotion within 14.5 wt‰ GO. The synthesized system would be potential to be applied in thermal energy storage fields. [ABSTRACT FROM AUTHOR]

In recent years, bio-based covalent adaptable networks (CANs) and vitrimers have developed rapidly in order to meet the renewable and sustainable requirements. It should be emphasized that the performance of the network need be upgraded and optimized to substitute petroleum-based polymers. Herein, a series of high-performance bio-based polyurethane were synthesized containing castor oil, isosorbide, vanillin derivative and 4,4′-Dicyclohexylmethane diisocyanate. By fine-tuning the bio-based diols, the hydrogen bond distribution and the crosslink density of the network were adjustable. The thermal mechanical properties and stress relaxation properties of the bio-based polyurethane were optimized. The bio-based polyurethane CANs shows tensile strength of 38.1 MPa, elongation at break of 243% and toughness of 55.7 MJ m−3, which is outstanding among most reported bio-based CANs. In addition, the polymer has excellent water resistance, shape memory and re-deformability. Due to the dissociation of imine bonds under mild acid conditions, the carbon fiber composite can readily degrade in mixed solvent for 3 h at 60 °C and the properties of recycled carbon fibers are highly preserved. Fabrication of extraordinary mechanical properties, reprocessably, and degradable polyurethanes through network structure design. [Display omitted] • Nonplanar rigid ring of isosorbide brings extraordinary mechanical properties to bio-based polyurethane CANs. • Adjusting the ratio of diols can tune the degree of cross-linking and distribution of hydrogen bonds in the networks. • Isosorbide can also improve fluidity of the network and lower activation energy. • CF composites can be chemically degraded under mild conditions for non-destructive recycling of CF. [ABSTRACT FROM AUTHOR]

Synthesis of vitrimer with dynamic covalent bond is a surprising solution to overcome the inherent limitations of traditional thermosets. A bio-based vitrimer-like polyurethane formed by castor oil, vanillin, m-xylylenediamine and 4,4′-dicyclohexylmethane diisocyanate in the preparation has superior mechanical properties, good solvent resistance, good thermal stability. Furthermore, the existence of dynamic imine bond in the vitrimer-like polyurethane is prone for polyurethane to rapid stress relaxation behavior, remoldability, weldability, antibacterial ability. With the hydrolysis of the imine bond, the material can be rapidly degraded at 60 °C for 1 h. In addition, it's commendable that the material exhibits excellent reprocessability that can be maintained at 86% even after 3 consecutive smash/mold pressing cycles. This work provides a promising method to manufacture bio-based polyurethane thermosets with excellent reprocessability, rapidly-degradable and antibacterial property, which has also promoted the high-value utilization of biomass materials. [Display omitted] • A novel bio-based vitrimer-like polyurethane containing castor oil and vanillin with high-strength has been synthesized. • Imine exchange reaction in the networks exhibits fast relaxation behavior and thermal processability. • The bio-based vitrimer-like polyurethane can be chemically degraded quickly under mild conditions. • Antibacterial performance was verified with an antibacterial rate of up to 86.63%. [ABSTRACT FROM AUTHOR]

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. PCL-HM prepared by two different kinds of alicyclic isocyanates, which is hard and tough and can be quickly repaired at 50 °C. [Display omitted] • Hard and tough thermoplastic polyurethane. • Thermoplastic polyurethane was prepared from mixed isocyanates. • Young's modulus, tensile strength and elongation at break of PCL-HM can reach 76 MPa, 11.8 MPa and 841%, respectively. • PCL-HM can quickly recover to 92% of its original tensile strength within 1 h at 50 °C. [ABSTRACT FROM AUTHOR]

It is still a huge challenge that integrating excellent mechanical performance and high healing efficiency into self-healing materials at the same time, even if numerous dynamic bonds have been explored in preparing of self-healing materials in the last 20 years. Herein, we reported a novel titin-inspired strategy to prepare the polyurethanes via introducing dual dynamic network which contained the physical cross-linking of quadruple hydrogen bonds formed by 5-(2-hydroxyethyl)-6-methyl-2-aminouracil (UPy) dimers and the covalent cross-linking of Diels-Alder (D-A) bonds. Specially, relying on the synergistic effect of the dual dynamic network, the resulting polyurethane F 50 U 50 -PU exhibited admirable mechanical performance, such as a super-high strength of 51.9 MPa, a superb toughness of 166.7 MJ/m3 and a large elongation at break of 930%. Meanwhile, on account of the dynamic feature of quadruple hydrogen bonds and D-A bonds, the resulting polyurethane showed a high heat-induced healing efficiency of 91.2%. More importantly, the polyurethanes could be recycled by hot-pressing process to regain their initial mechanical properties and integrity. And it was also used as substrate to construct self-healing conductive device, which displayed splendid self-healing of electrical conductivity after damage. It can be envisioned that the polyurethanes with both superior mechanical performance and high healing efficiencies have great application prospect in multifarious fields. [Display omitted] • Novel titin-inspired self-healing polyurethanes with dual dynamic network were prepared. • The optimal sample F 50 U 50 -PU showed a super-high strength of 51.9 MPa with a healing efficiency of 91.2%. • The materials can be recycled by cutting/hot-pressing process. • A self-healing conductive device with self-healing ability was explored. [ABSTRACT FROM AUTHOR]

It is necessary to develop polymer materials with excellent mechanical properties and can be quickly repaired under reasonable conditions. However, it is difficult to simultaneously optimize the mechanical properties and repair conditions as they have conflicting realization requirements. In this study, we prepare a thermoplastic polyurethane (I-4-P-HM) containing two kinds of alicyclic isocyanate with a tensile strength and toughness of 11.35 MPa and 64.1 MJ m−3, respectively. The mechanical properties of the cut and spliced I-4-P-HM films can be completely restored to their original values at near body temperature (40 °C) in only 2 h. In I-4-P-HM, isophorone diisocyanate (IPDI) directly connect to aromatic disulfide that enables a more efficient exchange of the aromatic disulfides, while dicyclohexylmethane 4,4′-diisocyanate (HMDI) with a symmetrical alicyclic structure endows the TPU with better mechanical properties. The two work together to make polyurethane have good mechanical properties and can be repaired quickly under mild condition. Furthermore, we carried out the scratch recovery experiments on I-4-P-HM covered with a layer of conductive silver paste, and the results indicate that this TPU has the potential to be applied in the flexible electronics industry. I-4-P-HM prepared by two different kinds alicyclic isocyanates not only have excellent mechanical properties, but also can be quickly repaired at near body temperature (40 °C). Image 1 • Polyurethanes are prepared from mixed isocyanates. • The mechanical strength and toughness of I-4-P-HM can be achieved 11.35 MPa and 64.1 MJ m3, respectively. • I-4-P-HM can be completely repaired in 2 h at 40 °C. • The polyurethanes obtained in this paper have certain repairing ability at near body temperature. [ABSTRACT FROM AUTHOR]

Polypyrrole nanoparticles (PPy) are widely used in cancer treatment because of its excellent photo-thermal effect. To our best knowledge, the application of such property in self-healing polymers have rarely been reported. Here, thermoplastic polyurethanes (TPU) were prepared by two-step method, and then TPU/PPy nanocomposites were prepared by solution blending. The stress and strain of TPU were increased from 8.20 MPa to 1540% to 13.50 MPa and 1650% with 0.25 wt% PPy respectively. Meanwhile, the thermal stability was also improved significantly. After the composite film was cut and spliced together, the fracture was irradiated with NIR, the mechanical strength of the composite material could be restored to over 80% in only 30 s. The strengthening effect of PPy in polyurethane and the rapid repair performance of composite materials can well solve the contradiction that self-repairing materials cannot improve the repair efficiency and mechanical properties simultaneously, and at the same time broaden the application area of PPy. Polypyrrole (PPy) can well disperse in polyurethane, which significantly improve the mechanical properties and thermal stability of composites. Meanwhile, the material can be repaired quickly under near-infrared light (NIR). Image 1 • PPy are used in NIR light-induced self-healing materials. • PPy can enhance mechanical strength and thermal stability of TPU. • PPy can promote the crystallization of TPU. • TPU/PPy nanocomposites can be repaired quickly under NIR. [ABSTRACT FROM AUTHOR]

Graphene and modified Graphene often can be used as effective reinforcer or cross-linker in self-healing materials. However, the influence of fillers sheets size on the self-healing materials remained unclear. In this report, we investigate the effect of different graphene oxide (GO) sheets size in the properties of self-healing Polyurethane. The different sizes of graphene oxide (GO) were prepared from various sizes of graphite via the improved Hummers' method. Furthermore, the corresponding maleimide functionalized GO (mGO) sheets were synthesized from maleimide modification processing. The X-Ray photoelectron spectroscopy (XPS) analysis shows that the smaller size GO, the higher oxidation and functionalization. We systematically investigated the influence of size GO and mGO on the mechanical and self-healing performance of Polyurethane/Graphene Oxide (PG) and Polyurethane/maleimide modified Graphene Oxide (PM) with the dynamic thermal reversible Diels-Alder bonds. The results show that GO sheets in smaller size produce an advantage on the mechanical and self-healing behavior. Moreover, the PM nanocomposites exhibited superior mechanical and self-healing properties compared to PG nanocomposites at the same loading. Image 1 • Different size of GO and mGO were prepared to reinforce the self-healing Polyurethane composites. • The mGO have an advantageous effect on improving the mechanical and self-healing properties of composites. • The smaller size of fillers can result to a significant effect on improving the self-healing efficiency. [ABSTRACT FROM AUTHOR]