Self-assembled fabrication and flame-retardant properties of reduced graphene oxide/waterborne polyurethane nanocomposites

The graphite oxide (GO) was prepared from expandable graphite by the pressurized oxidation method, and samples were characterized using XRD, UV–Vis, and TEM. GO is reduced in situ emulsion using hydrazine to achieve reduced graphene oxide/waterborne polyurethane (rGO/WPU) nanocomposites. The effect of rGO content on the stability, fracture morphologies, mechanical performance, thermal degradation, and flame-retardant properties of rGO/WPU composites was investigated by zeta potential analyzer, TEM, SEM, universal testing machine, TG, and Cone Calorimeter. The results of zeta potential, TEM, and SEM analysis indicate that rGO has a good stability and dispersibility in rGO/WPU nanocomposites. The results of mechanical tests showed that the mechanical properties of rGO/WPU nanocomposites increased consistently with increasing rGO content up to 2 mass%, and TG showed that the thermostability of rGO/WPU nanocomposites decreased slightly compared to pure WPU, but carbon residue increased from 0.99 to 1.99 % when the mass fraction of rGO in WPU is 2 %. Cone Calorimeter test indicated that the flame-retardant and smoke suppression properties of rGO/WPU composites showed significant improvement compared to the WPU alone. When the mass fraction of rGO is 1 %, the total smoke release and smoke factor decreased by 25 and 38 %, respectively, compared to those of pure WPU.     

Fabrication of functional waterborne polyurethane/montmorillonite composites by click chemistry method

"Click" chemistry method was used to fabricate novel waterborne polyurethane (WPU)/montmorillonite (MMT) composites based on alkyne-containing WPU and azide-modified montmorillonite. The morphology of these composites was characterized by x-ray diffractometer, scanning electron microscope. The mechanical properties, thermal stability, and flame resistance of the composites were investigated by tensile, thermogravimetry and cone calorimetric experiments, etc. The experimental results show that the tensile strength, water resistance and flame retardancy of the WPU/MMT composites have been reinforced efficiently owing to the linking of MMT by click reaction.     

Preparation and characterization of controlled heparin release waterborne polyurethane coating systems

In this study, to improve hemocompatibility of biomedical materials, a waterborne polyurethane (WPU)/heparin release coating system (WPU/heparin) is fabricated via simply blending biodegradable WPU emulsions with heparin aqueous solutions. The surface compositions and hydrophilicity of these WPU/heparin blend coatings are characterized by attenuated total reflectance infrared spectroscopy (ATR-FTIR) and water contact angle measurements. These WPU/heparin blend coatings show effectively controlled release of heparin, as determined by the toluidine blue method. Furthermore, the biocompatibility and anticoagulant activity of these blend coatings are evaluated based on the protein adsorption, platelet adhesion, activated partial thromboplastin time (APTT), thrombin time (TT), hemolysis, and cytotoxicity. The results indicate that better hemocompatibility and cytocompatilibity are obtained due to blending heparin into this waterborne polyurethane. Thus, the WPU/heparin blend coating system is expected to be valuable for various biomedical applications.     

基于CuAAC反应链间自交联有机-无机杂化水性聚氨酯的合成及性能

利用4,4’-二羟甲基-1,4-庚二炔功能单体作为扩链剂合成了一系列炔基接枝量不同的水性聚氨酯（WPU）,然后基于铜催化的叠氮-炔基环加成（CuAAC）反应,采用3-叠氮基丙基三乙氧基硅烷（APTES-N₃）改性炔基功能化WPU,制备了室温链间自交联有机-无机杂化WPU. 采用红外光谱（FTIR）和核磁氢谱（¹H NMR）表征了自交联有机-无机杂化WPU. 探讨了APTES-N₃接枝量对WPU膜性能和WPU乳液形态的影响. 结果表明,随着APTES-N₃含量增加,WPU膜的结晶性逐渐下降;耐水性、耐溶剂性和热稳定性逐渐增强;WPU乳液粒子黏连程度增加. 当APTES-N₃质量分数从0增大到12%时,WPU膜的拉伸强度从14.3 MPa增加到28.6 MPa.     

Synthesis and thermal properties of antimony doped tin oxide/waterborne polyurethane nanocomposite films as heat insulating materials

The waterborne polyurethane (WPU) was synthesized from the polycondensation between isophorone diisocyanate (IPDI) and polyoxypropylene glycol (N‐210) and then dispersed into water. Subsequently, the WPU emulsion was modified with antimony doped tin oxide (ATO) nanoparticle by ultrasonic dispersion. The ATO/WPU emulsion was cast onto Teflon molds. After being dried, ATO/WPU films were prepared. TEM indicated that the ATO nanoparticles were homogeneously dispersed in the polymer matrix at the nanometer scale. DSC showed that the ATO/WPU nanocomposites displayed increased glass transition temperatures compared to the control WPU. The mechanical properties of the films were characterized by dynamic‐mechanical analysis (DMA). The higher glass transition temperature and storage modulus indicates the superior mechanical properties of WPU modified by ATO nanoparticles over the conventional unmodified WPU. The thermal behaviors of the films were evaluated by thermogravimetric analysis (TGA). It could be found that the incorporation of ATO into WPU can improve the thermal stability dramatically. The results from UV–visible–near infrared spectra indicated that the ATO/WPU films could decrease the infrared transmission effectively. The heat‐insulation measurements showed that glass coated with ATO/WPU films possessed better heat‐insulating effect than empty glass. Copyright © 2010 John Wiley & Sons, Ltd.     

Optical and mechanical properties of polyurethane/surface-modified nanocrystalline cellulose composites

in order to improve the optical and mechanical performances of waterborne polyurethane （WPU）, nanocrystalline cellulose （NCC）/WPU composites were synthesized in this study. NCC （prepared by acid hydrolysis of cotton fiber） was modified by （3-aminopropyl）triethoxysilane （APTES） to enhance its compatibility with WPU, and the surface-modified NCC was characterized by grafting ratio, crystallinity and contact angle （CA）. NCC/WPU composites were examined by scanning electron microscopy （SEM）, X-ray powder diffraction （XRD） and thermogravimetric analysis （TG）. The anti-yellowing property, specular gloss, pencil hardness, and abrasion resistance of NCC/WPU composites were investigated by the methods of Chinese National Standards GB/T 23999-2009, GB/T 9754-2007, GB/T 6739-2006 and GB/T 1768-2006, respectively. The results showed that the grafting ratio of NCC modified by 6% APTES was 36.01% and the crystallinity of modified NCC was decreased with the enhancement of APTES. CA of the modified NCC was decreased by 28.8% and the nanoparticles were homogeneously dispersed in the WPU matrix. The XRD patterns of the NCC/WPU composites were relatively steady, while the thermal stability of the composites was enhanced by 6.7% with 1.0 wt% modified NCC. Modified NCC affected the specular gloss of NCC/WPU composites more obviously than the anti-yellowing property. The pencil hardness of NCC/WPU composites was increased from 2H to 4H by addition of NCC and the abrasion resistance of the composites was enhanced significantly. In general, NCC/WPU composites showed significant improvements in the optical and mechanical performances.     

Effect of Molecular Weight of WPU on the Heterogenic PUA Composite Latex Prepared by Soap-Free Emulsion Polymerization

Aqueous acrylic-polyurethane (PUA) composite emulsion was prepared by soap-free seeded emulsion copolymerization. Waterborne polyurethane (WPU) was used as the seeded emulsion and functioned as surfactant. The effect of molecular weight of WPU on the heterogenic was investigated. The molecular weight of WPU was controlled by varying the NCO/OH mole ratio. The GPC results confirmed that the molecular weight of WPU presented double distribution. And the molecular weight of WPU decreased with the increasing NCO/OH mole ratio. Surface tension test indicated that the molecular weight had little influence on the surface activity of WPU. However, after emulsion copolymerization of acrylic monomers, the morphology and properties of the PUA composite were impacted markedly by the molecular weight of WPU. With an increase in the NCO/OH mole ratio, the morphology of PUA composite latex changed from core-shell structures to fish bowl structure, and the mechanical properties of PUA films changed correspondingly.     

Antibacterial and Alkali-responsive Cationic Waterborne Polyurethane Based on Modification of Aloe Emodin

Cationic water-based polyurethane(CWPU) was synthesized to explore aloe-emodin modifies to obtain CWPU materials with better comprehensive performance. It provides a simple way to synthesize antibacterial waterborne polyurethane, which is to introduce the end-blocking group of herbal extracts into the structure. It contains synergistic antibacterial effect of herbal antibacterial and quaternary ammonium ion on Escherichia coli. It makes the material resist the erosion of bacterial, and increase the service life of materials. When the pH value of the environment changes, the UV absorbance of the aloe-emodin modified cationic water-based polyurethane(AE-CWPU) also changes. Therefore, within a certain detection range, AE-CWPU has great applications in the field of smart response materials. The modified thermodynamic properties have been improved, and the mechanical properties basically maintained the maximum stress, and the elongation at break was reduced.     

Hydrogen‐bonding,crystallinity, and morphological properties of poly(silicic acid)/waterborne polyurethane nanocomposites

Unique nanocomposites consisting of poly(silicic acid) nanoparticles (PNs) and waterborne polyurethane (WPU) were prepared. The aliphatic WPU prepared in this study was end‐capped with a silanol group, which could react with PNs via a sol–gel process. PNs were modified with phenyltrimethoxysilane (PTMS) and 3‐(trimethoxysilyl)propyl ester (TMPE) and then blended with WPU. The structure–property relationships were examined. Solid‐state ²⁹Si NMR spectra of WPU showed that structures T₁, T₂, and T₃ of WPU decreased and structures Q₃ and Q₄ of PN/WPU nanocomposites increased gradually. When the PN concentration increased to 10 wt %, PN/WPU nanocomposites exhibited the maximum fraction of hydrogen‐bonded carbonyl groups. In the PTMS–PN and TMPE–PN systems, the fraction of hydrogen‐bonded carbonyl groups fluctuated stably when the concentrations of PTMS–PN and TMPS–PN exceeded 5 wt %. The X‐ray diffraction results revealed that α‐form, γ‐form, or triclinic crystallization could be found in the WPU matrix. A differential scanning calorimetry spectrum showed that the crystalline structure of the hard segment of WPU was influenced by the nanoparticle concentration. The degrees of crystallinity were 88% for the PN/WPU nanocomposites, 41% for the PTMS–PN/WPU nanocomposites, and 54% for the TMPE–PN/WPU nanocomposites when the PN, PTMS–PN, and TMPE–PN concentrations were 5 wt %. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 1076–1089, 2005     

Preparation and characterization of waterborne polyurethane/attapulgite nanocomposites

In this paper, waterbrone polyurethane (WPU)/attapulgite (AT) nanocomposites have been prepared by direct emulsion blending. The WPU was synthesized from poly(tetramethylene glycol), 4,4-diphenylmethane diisocyanate, dimethylol butanic acid, and neutralized by triethylamine. SEM examination of fractured surfaces showed that AT particles were irregularly dispersed in the WPU matrix. FTIR analysis suggested no major chemical structural changed in the presence of a small amount of AT. DMA results showed that the storage modulus of WPU/AT nanocomposites was increased and the glass transition temperatures of both soft and hard segments shifted to higher temperature compared to the pristine WPU. Thermal resistance of the samples measured by TGA was improved with the addition of AT. The mechanical properties of the nanocomposites, examined by tensile tests, showed higher tensile strength and elongation at break than that of the pristine WPU.     

Effects of flower-like ZnO nanowhiskers on the mechanical, thermal and antibacterial properties of waterborne polyurethane

A novel waterborne polyurethane/flower-like ZnO nanowhiskers (WPU/f-ZnO) composite with different f-ZnO content (0-4.0 wt%) was synthesized by an in-situ copolymerization process. The f-ZnO consisting of uniform nanorods was prepared via a simple hydrothermal method. In order to disperse and incorporate f-ZnO into WPU matrix, f-ZnO was modified with γ-aminopropyltriethoxysilane. Morphology of f-ZnO in WPU matrix was characterized by scanning electron microscope. The properties of WPU/f-ZnO composites such as mechanical strength, thermal stability as well as water swelling were strongly influenced by the f-ZnO contents. It was demonstrated that appropriate amount of f-ZnO with good dispersion in the WPU matrix significantly improved the performance of the composites. The mechanical property was enhanced with an increase of f-ZnO content up to the optimum content (1 wt%) and then declined. Incorporation of f-ZnO enhanced the water resistance of the composites remarkably. It was amazing to observe that the thermal degradation temperatures of the composites initially decreased significantly and then leveled off with content increase of f-ZnO, which was different from the results of other WPU composite systems reported. Antibacterial activity of WPU/f-ZnO composite films against Escherichia coli and Staphylococcus aureus was also tested. The results revealed that the antibacterial activity enhanced with the increasing f-ZnO content, and the best antibacterial activity was obtained at the loading level of 4.0 wt% f-ZnO.     

Preparation and properties of amino-terminated anionic waterborne-polyurethane-silica hybrid materials through a sol-gel process in the absence of an external catalyst

A series of polymer-silica hybrid materials consisting of amino-terminated anionic waterborne-polyurethane (WPU) and inorganic silica particles have been prepared through a sol-gel process in the absence of an external catalyst. Typically, amino-terminated anionic WPU was first synthesized from polycaprolactone, dimethylol propionic acid, and 4,4′-methylenebis(cyclohexyl isocyanate) with specific molar ratios, followed by further reaction with triethylamine and triethylene tetramine to give as-prepared WPU. The WPU obtained was characterized by FTIR spectroscopy and gel permeation chromatography. Subsequently, a series of hybrid materials with different silica contents were prepared by performing sol-gel reactions with tetraethyl orthosilicate (TEOS) in an amino-terminated WPU matrix without the addition of an external catalyst. This was followed by examination by transmission electron microscopy and ²⁹Si solid-state NMR. The terminated primary amine groups attached to the as-prepared WPU chains functioned as an internal base catalyst for the sol-gel process of TEOS. The effect of composition on the thermal stability, mechanical strength, surface wettability, and optical clarity of the hybrid materials was evaluated by the thermogravimetric analysis, dynamic mechanical analysis, contact angle measurement, and UV-visible transmission spectroscopy, respectively.     

Monocomponent Waterborne Polyurethane Adhesives: Influence of the Crosslinking Agent on Their Properties

To improve the properties of the monocomponent waterborne polyurethane (WPU) adhesives, a series of crosslinked WPU were prepared with trifunctional polyester polyol (P210) as crosslinking agent. The crosslinked WPU dispersions and their films were characterized by conventional methods. The adhesion property of the samples was measured from T-peel test of leather/WPU adhesive/leather joints. Compared with the linear one, the crosslinked WPU exhibited low viscosity, small particle size, and low surface tension. For crosslinked films, the thermal stability, water resistance and mechanical properties were remarkably enhanced. The experimental data of T-peel test indicated that the adhesive strength significantly increased to 4.8 KN/m by crosslinking up to the optimum crosslink index of 1.2 and then showed a small decrease with excess.     

软段含离子的含氟水性聚氨酯的制备

以单羟基氟碳链一元醇为有机氟改性剂,将含氟基团引入聚氨酯主链中,通过分子设计的方法制备出软段含有离子基团的有机氟阴离子型水性聚氨酯。 比较了传统水性聚氨酯、硬段含氟的水性聚氨酯和软段含氟的水性聚氨酯在合成方法、耐水性、 热稳定性以及结晶性方面的差异;实验证明了软段含氟聚氨酯的水性聚氨酯的性能最为优良。 通过红外光谱的表征确定了氟化聚氨酯的结构,并证明了含氟基团的引入对聚氨酯软硬段间氢键作用的影响;水接触角由73°增加至107°,吸水溶胀率降低了66%,胶膜耐水性提高;热重分析结果表明,含氟聚氨酯的最大热失重温度提高了30 ℃,热稳定性增加;广角X射线衍射结果表明,胶膜的结晶度增加,结晶形式发生了微小程度的转变;扫描电子显微镜结果证明存在不均匀的多相结构。     

四甲基苯二甲基二异氰酸酯基水性聚氨酯的合成和性能

采用四甲基苯二甲基二异氰酸酯、聚酯二元醇和二羟甲基丙酸为原料,合成了一系列具有不同异氰酸根与羟基摩尔比（n(-NCO)/n(-OH)）的聚氨酯乳液。 研究了n(-NCO)/n(-OH)对水性聚氨酯性能的影响。 结果表明,当该比值增加时,乳液的粒径增大,分布变宽,结晶性降低,耐热性下降,耐水性能呈现降低的趋势。 当异氰酸根与羟基摩尔比为3时,四甲基苯二甲基二异氰酸酯基水性聚氨酯的乳液粒径为10～30 nm,膜的分解温度达到275 ℃,24 h吸水率低于10%。     

The polyurethane/polyacrylate soap-free emulsion formation: effects of hydrophilic polyurethane

The vinyl group terminated water-borne polyurethanes (WPU) with different DMPA content were prepared. Subsequently the core-shell polyurethane/polyacrylate (PUA) composite emulsions were synthesized by soap-free emulsion copolymerization. The WPU as sole surfactant was used in copolymerization, and the lowest surface tension could be achieved to 38.8?mN m^?1. Furthermore, the final conversion of acrylic monomer was reached to 98% in the case of WPU reactive seed. The FTIR-ATR indirectly confirmed the core-shell structure of PUA, simultaneously combined with DSC results found that the compatibility of WPU and PA was enhanced by growing grafting efficiency. The TEM results further indicated that the amount of DMPA in WPU had a great significant role in polymerization and final morphology structure. The PUA composite particles changed from scattered structure, core-shell structure to multi-core structure with increasing DMPA content. Correspondingly, the reinforcing and toughening effects were also found in PUA films with the increase content of DMPA by tensile testing.     

Synthesis,morphology, and properties of waterborne m-TMXDI-based anionic polyurethane and hybrids

In this study, waterborne polyurethane (WPU) hybrid emulsions with a weight ratio of 2/1 were prepared by emulsion polymerization using a mixture of styrene (St) and/or butyl acrylate (BA) monomers with WPU dispersion. WPU dispersion was synthesized with isocyanic acid and m-tetramethylxylene diisocyanate (m-TMXDI)-based anionic poly(urethane-urea) dispersions using the prepolymer mixing process. The structures of WPU and hybrids were characterized by FTIR spectroscopy. The size and morphology of the latex particles were investigated using dynamic light scattering and transmission electron microscopy, respectively. The stability of the emulsions was determined according to their shelf life and particle size using the dispersion analyser LUMiSizer® with STEP?-Technology. The thermal and mechanical properties of these films were examined by thermogravimetric analysis and strain-stress curves.     

水性聚氨酯阻燃纳米复合材料的Click反应制备及性能

以4,4'-二羟甲基-1,4-庚二炔功能单体作为扩链剂制备了端炔基功能化聚氨酯, 与叠氮基改性纳米蒙脱土(MMT-N₃)、 纳米氢氧化铝(ATH-N₃)和纳米氢氧化镁(MH-N₃)通过Click反应制备了水性聚氨酯(WPU)阻燃纳米复合材料. 采用红外光谱(FTIR)、 核磁氢谱(¹H NMR)和扫描电子显微镜(SEM)对WPU阻燃纳米复合材料的结构进行了表征, 对比研究了纳米阻燃剂配比和制备方法对WPU阻燃纳米复合材料的氧指数、 动态燃烧行为和热稳定性的影响. 阻燃性能研究结果表明, 当MMT-N₃, MH-N₃和ATH-N₃的质量分数分别为7%, 2%和1%时, 采用Click反应制备的复合材料的氧指数比纯WPU高7%, 点燃时间从10 s延长到29 s, 峰值热释放速率和烟释放速率分别降低了41%和42%. 热失重分析结果表明, 当MMT-N₃质量分数为10%时, 与WPU相比, 采用Click反应制备的MMT/WPU复合材料在热失重50%时的温度提高了21 ℃. 复合材料断面和燃烧后残渣的SEM分析证明在聚合物基体中Click反应是分散纳米材料的一种有效方法.     

WPU预聚体中羧基含量及其位置对树脂的粒径及其耐水性之影响的研究

本文先将马来酸酐与多元醇作用，然后再与其它单体反应，合成了含有羧基的聚氨酯预聚体，并用丁酮稀释后，在普通搅拌条件下使预聚体分散于三乙醇胺的水溶液中，合成出以水为分散介质的聚氨酯分散体系（WPU）。并通过改变羧基在预聚体中的含量和位置，发现随着羧基含量的增加，WPU的粒径减小，而耐水性下降。同时发现，在一定的羧基含量下，同侧羧基相比，端羧基更有利于预聚体的乳化，制得的WPU不仅颗粒较小，而且树脂耐水性明显优于侧基羧预聚体制备的WPU，从而提出羧基的运动自由度是影响羧基乳化活性和树脂耐水性的重要因素。     

水性聚氨酯硬段含量对其氢键相互作用及性能的影响

异佛尔酮二异氰酸酯（IPDI）、二羟甲基丙酸(DMPA)作为硬段,合成了水性聚氨酯。 研究了硬段含量（质量分数）对乳液稳定性、膜耐热和力学性能等的影响。 当硬段质量分数低于26%时,乳液贮存稳定性较差。 随着硬段含量增加,聚氨酯膜拉伸强度迅速增加,断裂伸长率略有降低;红外光谱显示,自由的N-H伸缩振动峰强度减弱,氢键化N-H的振动峰强度增加;同时C=O伸缩振动峰整体向低波数方向移动,C=O伸缩振动峰峰形有明显的变化;DSC测试在50～125 ℃出现明显的氢键解离现象,吸热峰增强,证实了氢键作用力随着硬段含量的增加逐渐增强。 TG测试表明,水性聚氨酯硬段和软段分步解离,随着硬段含量的增加,硬段分解温度降低,水性聚氨酯耐热性能下降。