Super‐Tough,Self‐Healing Polyurethane Based on Diels‐Alder Bonds and Dynamic Zinc–Ligand Interactions

Self‐healing polymer materials have attracted extensive attention and have been explored due to their ability of crack repairing in materials. This paper aims to develop a novel polyurethane‐based material with high self‐healing efficiency and excellent mechanical properties under 80 °C on the basis of reversible Diels–Alder bonds as well as zinc–ligand structure (DA‐ZN‐PU). By integrating DA bonds and zinc–ligand structure, as‐prepared DA‐ZN‐PU samples reach the maximum tensile strength as much as 28.45 MPa. After self‐healing, the tensile strength is 25.85 MPa, leading to the high self‐healing efficiency of 90.8%. In addition, by introducing carbonyl iron powder (CIP), a new polyurethane containing carbonyl iron powder (DA‐ZN‐CIP‐PU) can be achieved, exhibiting microwave‐assisted self‐healing property. And the self‐healing efficiency can be reached to 92.6% in 3 min. Due to high self‐healing efficiency and excellent mechanical properties of the prepared novel polyurethane, it has application attributes in crack repair of functional composite materials.     

Recyclable bio‐based crosslinked polyurethanes with self‐healing ability

We report the synthesis of a linear bio‐based polyurethane (bio‐PU) containing furan ring by using renewable polylactide copolymer diol and 2,5‐furandimethanol as a soft segment and chain extender, respectively, in which the reversible crosslinked covalent bonds between hard segments were incorporated via Diels–Alder (D‐A) reaction between the furan ring of the chain extender and bismaleimide (BM) crosslinker. By simply controlling the amount of BM, mechanical properties of the obtained crosslinked bio‐PUs (CBPUs) were varied widely. In particular, the CBPU100 sample shows the highest tensile strength of 10.8 MPa, Young's modulus of 193 MPa, and an elongation of 155%. The differential scanning calorimetry experiments verify the recycle property of the CBPUs by the D‐A/retro‐D‐A reaction at the proper temperature. The thermal recyclability and remolding ability of these materials are demonstrated by two kinds of polymer processing methods, i.e., solution casting and hot‐compression molding. The recycled CBPUs display almost identical elongation and slightly decreased tensile strength compared to the as‐synthesized samples. Furthermore, the CBPUs also exhibit excellent self‐healing ability. Therefore, the resulting CBPUs possess tunable mechanical properties, good thermal recyclability, re‐mending, and self‐healing ability, which makes the bio‐based materials more eco‐friendly. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46272.     

Facile Preparation of Polydimethylsiloxane Elastomer with Self‐Healing Property and Remoldability Based on Diels–Alder Chemistry

The polydimethylisioxane elastomer based on Diels–Alder (DA) chemistry is successfully prepared by directly crosslinking bis(3‐aminopropyl)‐terminated polydimethylsiloxane with the bisepoxide containing two DA bonds in one molecule via epoxy‐amine reaction. The elastomer prepared based on DA chemistry exhibits good mechanical property, high self‐healing, and remolded efficiencies. The as‐prepared elastomer can be stretched to over 400% and its tensile strength can reach 0.80 MPa. The self‐healing efficiency and remolded efficiency are up to 93% and 95%, respectively. This work provides a simple and efficient way to fabricate the self‐healing and remolded polydimethylsiloxane elastomer with good mechanical properties. The as‐prepared elastomer has a promising potential in artificial muscles, protective coatings, and intelligent flexible electronics.     

Flexible Polysaccharide Hydrogel with pH‐Regulated Recovery of Self‐Healing and Mechanical Properties

A self‐healable hydrogel with recoverable self‐healing and mechanical properties is reported. The hydrogel (coded as ACSH) crosslinked by Schiff base linkage contains two polysaccharides of acrylamide‐modified chitosan (AMCS) and oxidized alginate (ADA). Self‐healing and mechanical properties are heavily influenced by the crosslinking time. The hydrogel crosslinked for 2 h possesses better mechanical and self‐healing properties than hydrogel crosslinked for 24 h. Macroscopic test shows that hydrogel without self‐healing ability can recover the self‐repair and mechanical properties by adjusting the pHs. The recovery of self‐healing and mechanical properties relies on the pH sensitivity of the Schiff base linkage. Adjusting the pH to acid, the Schiff base linkage becomes unstable and breaks. Regulating the pH to neutral, reconstruction of Schiff base linkage leads to recovery of the self‐repair and mechanical properties. The recoverable self‐healing property can be cycled once breakage and reconstruction of the Schiff base linkage can be conducted. In addition, this study demonstrates that the hydrogel can be remodeled into different shapes based on self‐healing property of the hydrogel. It is anticipated that this self‐healable hydrogel with recoverable self‐healing and mechanical properties may open a new way to investigate self‐healing hydrogel and find potential applications in different biomedical fields.     

Preparation,mechanical properties of waterborne polyurethane and crosslinked polyurethane‐acrylate composite

The waterborne polyurethane (PU) prepolymer was first prepared based on isophorone diisocyanate, polyether polyol (NJ‐210), dimethylol propionic acid (DMPA), and hydroxyethyl methyl acrylate via in situ method. The crosslinked waterborne polyurethane‐acrylate (PUA) dispersions were prepared with the different functional crosslinkers. The chemical structures, optical transparency, and thermal properties of PU and PUA were confirmed by Fourier transform infrared spectrometry, ultraviolet–visible spectrophotometry, and differential scanning calorimetry. Some physical properties of the aqueous dispersions such as viscosity, particle size, and surface tension were measured. Some mechanical performances and solvent resistance of PUA films were systemically investigated. The experimental results showed that the particle sizes of the crosslinked PUA aqueous dispersions were larger than the PU and increased from 57.3 to 254.4 nm. When the ratios of BA/St, BA/TPGDA, and BA/TMPTA were 70/30, PUA films exhibited excellent comprehensive mechanical properties. The tensile strength and elongation at break of the film were 2.17 MPa and 197.19%. When the ratio of BA/St was 30/70, the film had excellent water resistance and was only 6.47%. The obtained PUA composites have great potential application such as coatings, leather finishing, adhesives, sealants, plastic coatings, and wood finishes. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Interpenetrating polymer networks of bismaleimide and polyether polyurethane–crosslinked epoxy

In this work, we prepared the interpenetrating polymer networks of bismaleimide and polyether-type polyurethane(polyoxypropylene)–crosslinked epoxy (BMI/PU(PPG)–EP IPNs) by employing the simultaneous bulk polymerization technique. The polyurethane (PU)–crosslinked epoxy was identified via infrared (IR) spectra analysis. Also investigated herein were the mechanical properties, including tensile strength, Izod impact strength, and fracture energy (G_IC) of the IPNs with various BMI contents in PU–crosslinked epoxy matrix. In addition, differential scanning calorimetry (DSC) analysis and the thermogravimetric analysis (TGA) were performed to examine the thermal properties of the BMI/PU(PPG)–EP IPNs. In addition, morphology and dynamic mechanical analysis (DMA) of the BMI/PU(PPG)–EP IPNs were also studied. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 70: 2635–2645, 1998     

Miscibility and properties of semi‐interpenetrating polymer networks based on polyurethane and nitroguar gum

Films from castor oil‐based polyurethane (PU) prepolymer and nitroguar gum (NGG) with different contents (10–70 wt %) were prepared through solution casting method. The networks of PU crosslinked with 1,4‐butanediol were interpenetrated by linear NGG to form semi‐interpenetrating polymer networks (semi‐IPNs) in the blend films. The miscibility, morphology, and properties of the semi‐IPNs coded as PUNG films were investigated with Fourier transform infrared spectroscopy, scanning electron microscopy, differential scanning calorimetry, dynamic mechanical thermal analysis, wide‐angle X‐ray diffraction, density measurement, ultraviolet spectroscopy, thermogravimetric analysis, tensile, and solvent‐resistance testing. The results revealed that the semi‐IPNs films have good miscibility over the entire composition ratio of PU to NGG under study. The occurrence of hydrogen‐bonding interaction between PU and NGG played a key role in improvement of the material performance. Compared with the pure PU film, the PUNG films exhibited higher values of tensile strength (11.7–28.4 MPa). Meanwhile, incorporating NGG into the PU networks led to an improvement of thermal stability and better solvent‐resistance of the resulting materials. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104, 4068–4079, 2007     

Preparation and properties of the self‐crosslinked acrylic rubber via gamma ray initiated emulsion polymerization

In this study, a series of self‐crosslinked acrylic rubbers were prepared by gamma ray initiated emulsion copolymerization. Acrylic acid and N‐hydroxymethl acrylamide were used as the cure‐site monomers. The vulcanizing properties, tensile properties, and dynamic mechanical analysis of the self‐crosslinked acrylic rubbers were investigated. It was found that the curing characteristics could be influenced significantly by the content and species of the cure‐site monomers. Improvement in mechanical properties like tensile strength, modulus and elongation at break was observed in the prepared self‐crosslinked rubber. The structure‐property correlation of the self‐crosslinked acrylic rubber was discussed. POLYM. ENG. SCI. 46:1748–1753, 2006. © 2006 Society of Plastics Engineers.     

Thermal and mechanical properties of multiple‐component aliphatic degradable polyurethanes

Macroscopic thermal and mechanical properties of complex aliphatic polycarbonate‐based polyurethane (PU) films containing degradable ester units in PU backbone were studied by a combination of several experimental techniques. Differential scanning calorimetry (DSC) revealed that the synthesized oligomeric diol (DL‐L) contributes (in addition to polycarbonate diol) to the formation of soft‐segment domains, while the hard‐segment domains are formed from 1,6‐diisocyanatohexane (HDI) and butane‐1,4‐diol (BD). Three main phase transitions were detected by DSC and by dynamic mechanical thermal analysis. Thermogravimetric analysis (TGA) of two‐component PUs showed that the PU made from DL‐L and HDI is the least thermostable product, while the PU made from polycarbonate diol and HDI is the most stable one. The differences in the thermal stability of different four‐component PUs are not important. Tensile properties very sensitively reflect the changes in composition and in microstructure of PU samples; the best tensile properties exhibits the degradable sample containing the equimolar ratio of hydroxyl groups of macrodiol, oligomeric diol DL‐L and butane‐1,4‐diol. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41872.     

Recyclable,shape‐memory,and self‐healing soy oil‐based polyurethane crosslinked by a thermoreversible Diels–Alder reaction

The recyclable, shape‐memory, and self‐healing soy oil‐based polyurethane (S‐PU) networks were constructed by the thermoreversible Diels–Alder (DA) reaction between S‐PU (sealed with furfuryl alcohol) and 1,5‐bis(maleimido)‐2‐methylpentane. The DA and retro‐DA reactions between furan and maleimide were investigated by Fourier transform infrared spectroscopy, differential scanning calorimetry, solubility, and recycle testing. Moreover, the shape‐memory properties of the S‐PU networks were studied by qualitative recovery testing and quantitative cyclic tensile testing. Furthermore, the self‐healing properties of S‐PU networks were confirmed by cut, scratch, and tensile testing. The results showed that, compared to the traditional S‐PU, the novel S‐PU prepared in this work was recyclable and self‐healing. And although both of them have shape‐memory effect, the novel S‐PU has a higher shape fixed rate and shape recovered rate than the traditional S‐PU. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46049.     

Preparation and characteristics of a water‐soluble chitosan–heparin complex

To improve the wound‐healing ability of chitosan, heparin, known to be effective in wound healing, was complexed with water‐soluble chitosan (WSC) by chemical reaction. The chemical structure of the water‐soluble chitosan–heparin (CH) complex was analyzed, and CH complex formation was confirmed with an FTIR spectrometer. The mechanical and thermal properties of the CH complex were measured by a tensile tester and thermal analyzers (DSC and TGA). Within the heparin content up to ≈470 IU/g in the aqueous CH complex solution, the intrinsic viscosity and tensile strength of the water‐soluble CH complex gradually increased, but thermal stability slightly decreased by introducing the heparin into the WSC. When the heparin content was greater than these values (470 IU/g), the water‐insoluble CH complex, which is supposed to have a multisubstituted or crosslinked structure, precipitated in the aqueous water‐soluble CH complex solution. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 87: 1784–1789, 2003     

Physical properties of water‐borne polyurethane blended with chitosan

Water‐borne polyurethanes based on 4,4‐diphenylmethane diisocyanate, poly(butylene adipate), and chain extender N‐methyldiethanolamine (MDEA) that provided tertiary amine groups were synthesized. The polyurethane–chitosan (PU/CS) blends can be dissolved in the acetic acid and cast into films. The mechanical properties including tensile strength and elongation, as well as the water absorption and thermal properties of the PU/CS films were evaluated. The tensile strength increased with the increased amount of chitosan, but the elongation decreased accordingly. The chitosan in the blends promoted the water absorption. Chitosan was more thermally‐stable than PU, as shown in the thermal gravity analysis. Chitosan also had higher crystallinity, as demonstrated by differential scanning calorimetry. The blends were partial compatible mixtures, based on the data obtained from a dynamic mechanical analysis. Biocompatibility test was conducted utilizing immortalized rat chondrocytes (IRC). After IRC were seeded onto the PU/CS films for 1.5 and 120 h, the number of cells was counted and the morphology of cells was observed by light microscopy and scanning electron microscopy. Blends containing 30% chitosan had more cells attached initially. However, the blends containing more than 70% chitosan appeared to promote the cell proliferation. IRC were round on PU/CS films with more PU, but spread when the chitosan content in blends was higher. Overall, PU/CS films with more chitosan had better mechanical properties as well as biocompatibility. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 2683–2689, 2007     

聚氨酯/纳米金刚石纳米复合材料的性能研究

通过原位反应法制备了聚氨酯(PU)/纳米金刚石(ND)纳米复合材料,采用X射线衍射(XRD)、热失重分析(TGA)、扫描电子显微镜(SEM)和力学性能测试等手段系统研究了PU/ND纳米复合材料的力学性能、热性能和形态。研究结果表明,ND能够显著提高聚氨酯的力学性能。随着ND用量的增加,PU/ND纳米复合材料的拉伸强度、100%定伸应力、500%定伸应力和断裂伸长率先增加后减少。当ND质量分数为0.5%时,PU/ND纳米复合材料的力学性能最佳,拉伸强度和断裂伸长率分别提高了61.5%和39.1%。PU/ND纳米复合材料的T-剥离强度和耐热性也有提高。     

Polyether–maleimide‐based crosslinked self‐healing polyurethane with Diels–Alder bonds

The Diels–Alder (DA) reaction is particularly desirable for the preparation of heat‐stimuli self‐healing polymeric materials because of its thermal reversibility, high yield, and minimal side reactions. Some attempts were conducted to synthesize polyether–maleimide‐based crosslinked self‐healing polyurethane with DA bonds (C‐PEMIPU–DA) through the reactions of the prepolymer (polymeric MDI/PBA‐1000) functionalized by furfuryl amine and polyether–maleimide without benzene in this study. The structures of intermediates and C‐PEMIPU–DA were first confirmed by ¹H‐NMR, Fourier transform infrared spectroscopy, and differential scanning calorimetry. Next, the thermal reversibility and the self‐healing performance of C‐PEMIPU–DA were studied by ¹H‐NMR, polarizing optical microscopy, tensile testing, and a sol–gel process. The results show that C‐PEMIPU–DA exhibited interesting properties of thermal reversibility and self‐healing. The polymers could be applied to self‐healing materials or recyclable materials in the fields of the repair of composite structures and aging parts because of their thermosetting properties at room temperature and thermoplasticity at higher temperatures. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41944.     

Polyurethane‐acrylic hybrid emulsions with high acrylic/polyurethane ratios: Synthesis,characterization, and properties

Allyl polyoxyethylene ether (APEE) was used as coupling agent between polyurethane (PU) and acrylic polymer (AC) to synthesize stable waterborne polyurethane‐acrylic (PU‐AC) hybrid emulsions with high AC/PU weight ratio ranged from 45/55 to 70/30. The effect of the AC/PU weight ratio and the acrylate type including methyl methacrylate (MMA), butyl acrylate (BA) and mixture of them on the properties of the synthesized emulsions and resultant films were investigated. The research results showed that the colloidal particle of the emulsions behaved core‐shell structure, and the copolymers were not crosslinked. An increase in the AC/PU weight ratio led to an increase in the average particles size and the particle size distribution, but decrease in the viscosity of the emulsions. Meanwhile, the molecular weight distribution of the copolymers became wide, and the tensile stress, shore A hardness, storage modulus, glass transfer temperature, water resistance, and water contact angle of the resultant films increased, except that the films of PU‐BA were too soft to determine their mechanical properties. MMA and BA can provide the PU‐AC hybrid emulsions with very different properties, and which can be adjusted according to the special application. It was suggested that APEE can not only built up chemical bonds between PU and AC, but also increase the self‐emulsifying ability in the emulsion polymerization due to its hydrophilic ethylene oxide and carboxylic groups, resulting in that PU‐AC hybrid emulsions with high AC/PU ratio can be obtained by this method. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44488.     

BPS/有机氮磷复合阻燃增强增韧PA66材料的性能

以溴化聚苯乙烯(BPS)和自制的有机氮磷阻燃剂(NPR)为尼龙(PA)66的阻燃剂,以短切玻璃纤维为增强剂,加入增韧剂三元乙丙橡胶,制备了阻燃增强增韧PA66材料,研究了阻燃剂的加入及复配对材料力学性能、极限氧指数(LOI)、垂直燃烧性能、最大烟密度、热稳定性等性能的影响。结果表明,相对于BPS,NPR对材料力学性能的不利影响更大,单独使用BPS时材料的阻燃效果较差,而单独使用NPR可明显提升材料的阻燃性能,当NPR质量分数为15%时,材料的LOI为34%,垂直燃烧等级达到V–0级,拉伸强度、弯曲强度和缺口冲击强度分别为161,224 MPa和12 kJ/m~2。在阻燃剂总质量分数为15%的条件下,与单独使用NPR相比,BPS与NPR的复配进一步降低了材料的拉伸与弯曲强度,但在保持阻燃性能的同时降低了材料成本。NPR的加入导致材料最大烟密度有所增大,热降解提前,而BPS与NPR的复配进一步增大了材料的最大烟密度,使热降解有所延后。     

Enhanced adhesion force based on microphase separation induced by complexation of ferric ions and polyurethane matrix

Waterborne polyurethane elastomer (WPU) has been widely used as a glue, but it still has some drawbacks, including a long cure time and weak adhesive force. In order to overcome these drawbacks, a new composite [PU/ferric ion complexation (Fe/PU)] with high adhesive strength was successfully prepared using ferric ion (Fe³⁺) as a complexing agent. Fourier transform infrared spectroscopy, differential scanning calorimetry, dynamic mechanical analysis, and tensile testing were used to characterize the chemical structure and mechanical properties of the as‐obtained composites. Introduction of the ferric ion induces a certain degree of microphase separation, resulting in better mechanical strength and interfacial adhesion. The mechanical properties of the PU composite with ferric ions are higher than that of pure PU. The adhesive strength of the 25%‐Fe/PU composite is 32.46 ± 3.1 MPa, exhibiting superior adhesive strength. The tensile strength was enhanced 34%, and the elongation was enhanced 23.6% compared to pure PU. Furthermore, the Fe/PU composite, coordinated with ferric ions, exhibits an enhanced storage modulus and reduced loss coefficient compared to PU. We can foresee that Fe/PU composites will play an important role in the building and engineering areas. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46069.     

Synthesis and characterization of polyurethane hybrids: Influence of the polydimethylsiloxane linear chain and silsesquioxane cubic structure on the thermal and mechanical properties of polyurethane hybrids

The structural effects of polydimethylsiloxane (PDMS) or polyhedral oligosilsesquioxanes (POSSs) on the thermomechanical properties of polyurethane (PU) networks were studied. An ester–amine‐functionalized silsesquioxane and a PDMS macromer were synthesized, and the macromer (10 wt %) was crosslinked with the PU prepolymer to obtain PU networks. The synthesized macromers and hybrids were characterized with Fourier transform infrared, ¹H‐NMR, ¹³C‐NMR, and ²⁹Si‐NMR spectroscopy techniques. The influence of POSS cubes on the thermal and mechanical properties of the polymer network films was studied comparatively with the similarly functionalized PDMS linear chain via thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and dynamic mechanical analysis (DMA) measurements. The degradation pattern of the POSS‐incorporated PU nanocomposites was almost the same as that of the PU network synthesized from the linear PDMS macromer. The differences in the char yields and activation energies of the hybrids reflected the enhancement of the thermal properties of the nanohybrids. The TGA and DSC curves of the macromers suggested that the thermal properties of the macromers not only depended on either the PDMS or POSS inorganic core but also depended on the organic peripheral attached to the inorganic core. The glass‐transition temperatures of the nanohybrids were higher than those of the linear‐PDMS‐incorporated hybrids. The storage modulus values increased 3‐fold upon the incorporation of POSS rigid groups into the PU hybrids in comparison with the flexible PDMS‐chain‐incorporated PU hybrids. The DMA measurements showed a long‐range rubbery plateau region for all the PU hybrids, with high storage modulus and tan δ values showing the structural homogeneity of the crosslinked networks. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Polyurethanes from benzene polyols synthesized from vegetable oils: Dependence of physical properties on structure

Asymmetric and symmetric aromatic triol isomers were synthesized from erucic acid. The pure asymmetric and symmetric triols were crosslinked with MDI into their corresponding polyurethane sheets. The physico‐chemical properties of these polyurethanes were studied by Fourier transform infrared (FTIR) spectroscopy, X‐ray diffraction (XRD), differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), thermogravimetric analysis coupled with Fourier transform infrared (TGA‐FTIR) spectroscopy, and tensile analysis. The A‐PU and S‐PU demonstrated differences in their glass transition temperatures (T_g) and crosslinking densities. The difference in T_g of these polyurethanes could be explained by the differences in crosslinking densities, which could be related to the increase in steric hindrance, to the crosslinking MDI molecules, between adjacent hydroxyl groups of the asymmetric triol monomers. Overall, it was found that both polyurethanes had similar mechanical and thermal properties. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

AB‐type crosslinked polymer networks from vinyl terminated polyurethane and poly(methyl methacrylate)

Vinyl terminated polyurethanes (VTPUs) were prepared by endcapping isocyanate terminated prepolymers with vinylbenzyl alcohol (VBA). AB‐type crosslinked polymer (ABCP) networks were generated by crosslinking the telechelic polyurethane with methyl methacrylate (MMA) in the presence of 2,2′‐azobisisobutyronitrile (AIBN) as free radical initiator. The spectral, thermal and mechanical properties of ABCPs were studied using Fourier Transform IR, thermogravimetry, dynamic mechanical analysis and stress‐strain analysis. The FTIR results confirm the formation of VBA, TP and ABCPs. Thermal behaviour of crosslinked polymers showed no significant weight loss up to 300 °C, indicating improved thermal stability. Dynamic mechanical tests revealed confinement of phase separation and good damping behaviour for the crosslinked networks. Stress‐strain analysis showed that tensile strength increases with increasing amounts of methyl methacrylate. © 2001 Society of Chemical Industry