Effect of nanosilica content on properties of polyurethane/silica hybrid emulsion and its films

Polyurethane/silica hybrid emulsion (PUSi) was synthesized by the reaction of isophorone isocyanate, polyether polyol, hydrophilic nanosilica (A200), dimethylol propionic acid, trimethylol propane, and 3‐aminopropyltriethoxysilane (KH550). The films of the waterborne polyurethane (WPU) were prepared. The structure of the polyurethane was characterized by Fourier transform infrared spectrometer (FTIR), thermogravimetry (TG), and differential scanning calorimetry (DSC). The particle size distribution and morphology of emulsion were examined. Influence of nanosilica content on the mechanical properties and solvent absorption of the cast films were also measured quantificationally. FTIR indicates that  NH₂ of KH550 reacted with  NCO of polyurethane. TG analysis indicates that nanosilica can improve thermal stability of polyurethane. There is no clear effect of nanosilica on the glass transition of soft segments. It was found that greater mechanical properties of WPU were obtained when chemical networks were formed by sol‐gel process. As the nanosilica content increases, water absorption and ethanol absorption decreased. The particle size increases with increase of A200 content. PUSi hybrid emulsions are endowed with pseudoplasticity. The apparent viscosity of emulsions increased and then decreased with addition of A200. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Synthesis and characterization of nanosilica/waterborne polyurethane end‐capped by alkoxysilane via a sol‐gel process

A novel method was used to synthesis nanosilica/waterborne polyurethane (WPU) hybrids by in situ hydrolysis and condensation of tetraethyl orthosilicate (TEOS) and/or 3‐aminopropyltriethoxylsilane bonding at the end of the WPU molecular chain. The hybrid was characterized by scanning electron microscopy, energy dispersive spectroscopy (EDS), transmission electron microscopy, Fourier transform infrared spectroscopy (FTIR), and X‐ray photoelectron spectroscopy (XPS). The results showed that the nanosilica/WPU hybrids with well‐dispersed nanosilica particles were synthesized, in which the particles had typical diameters of about 50 nm. In addition, XPS and FTIR analyses demonstrated that chemical interaction occurred between WPU and silica. The effects of TEOS on surface wettability, water resistance, mechanical strength, and thermal properties of the hybrid were also evaluated by contact angle measurements, water absorption tests, mechanical tests, and differential scanning calorimetry, respectively. An increase in advancing contact angles, water resistance, and tensile strength, as well as decrease in elongation at break and glass transition temperature, were obtained with the addition of TEOS. Water absorption decreased from 17.3 to 5.5%. The tensile strength increased to a maximum of 29.7 MPa, an increase of about 34%. Elongations at break of the hybrids decreased 191%. These results were attributed to the effects of the nanosilica and the chemical interaction between WPU and silica. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Crystallinity evolution of soft segments during the synthesis of polyester‐based waterborne polyurethane

Polyester‐based waterborne polyurethane (WPU) dispersions having poly(ethylene glycol) adipate diol, isophorone diisocyanate, and hexamethylene diisocyanate as the main raw materials were synthesized by an acetone process. In each step of the synthesis process, the intermediate products were collected, and the crystallization morphologies and relative crystallinity (X) of the soft segments (SSs) in their films were investigated by means of polarizing optical microscopy, differential scanning calorimetry, and X‐ray diffraction. The fracture surfaces and thermostability of the intermediate films were also investigated by scanning electron microscopy (SEM) and TGA, respectively. The results show that the crystalline dimensions of the SSs decreased substantially during the synthesis process of WPU. X of the SSs decreased after the prepolymerization reaction and increased after the hydrophilic chain‐extending reaction, then decreased after emulsification, and finally increased after the secondary chain‐extending reaction. Moreover, The SEM photos indicate that with decreasing crystalline dimensions, the fracture mechanisms of the intermediate films varied gradually from brittle failure to ductile fracture. The thermostability of the intermediates obtained in each step of the synthesis process was in accordance with the variation tendency of the X of the SSs. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40270.     

Synthesis and properties of networking waterborne polyurethane/silica nanocomposites by addition of poly(ester amine) dendrimer

The second‐generation poly(ester amine) dendrimer was prepared by Michael addition reaction and esterification reaction at first. Then, a series of novel waterborne polyurethane (WPU)‐based composites were prepared by the addition of poly(ester amine) dendrimer into the WPU. The structures and the morphology of the WPU composites were measured with Fourier transform infrared spectrometer, scanning electron microscopy, and X‐ray diffraction. SEM images revealed that the nanosilica was well dispersed in the WPU matrix. The mechanical properties of the WPU composites were improved with the addition of poly (ester amine) dendrimer. The dynamic mechanical thermal analysis results showed that the WPU composites had higher glass transition temperature than that of pure WPU, especially after incorporation of poly(ester amine) dendrimer. This conclusion is in good agreement with the differential scanning calorimetry results. The thermal properties of the pure WPU and its composites were investigated by thermogravimetric analysis. The results showed that the initial decompose temperature began from about 250°C, and had a little increase when introducing poly(ester amine) dendrimer into the WPU matrix. POLYM. COMPOS., 2012. © 2013 Society of Plastics Engineers     

氧化石墨烯改性磺酸型水性聚氨酯的制备与性能研究

首先对石墨进行氧化处理制备氧化石墨(GO),然后对GO进行超声处理得到氧化石墨烯(GOs),并通过共混法制备了水性聚氨酯(WPU)/GOs复合材料。讨论了超声分散以及GOs加入量对WPU/GOs复合材料力学性能和热稳定性的影响。结果表明,经过超声分散的复合材料的力学性能比未超声分散的好;随着GOs含量的增加,复合材料的拉伸强度先增大后减小,断裂伸长率逐渐减小;加入质量分数0.50%的GOs,其WPU/GOs复合材料的热分解温度可提高44.7℃,明显提高WPU的热稳定性。     

Ab initio reversible addition–fragmentation chain transfer emulsion polymerization of styrene/butyl acrylate mediated by poly(acrylic acid)‐block‐polystyrene trithiocarbonate

Ab initio reversible addition–fragmentation chain transfer (RAFT) emulsion polymerization of styrene/butyl acrylate was investigated with the trithiocarbonate macro‐RAFT agent poly(acrylic acid)‐block‐polystyrene (PAA‐b‐PS) as a stabilizer and a RAFT agent. Influences of the amount of ammonium persulfate (APS), the amount of PAA‐b‐PS and the mass ratio of monomers on emulsion polymerization and film properties are discussed. The particle morphology exhibited spherical‐like structure with particles of about 90 nm in diameter and relatively narrow particle size distribution characterized using transmission electron microscopy and dynamic laser scattering. Fourier transform infrared and ¹H NMR spectra showed that the styrene/butyl acrylate emulsion was successfully synthesized. The monomer conversion increased initially with increasing amount of APS, from 0.4 up to 0.8 wt%, and then decreased. The particle size increased and its distribution decreased gradually with increasing amount of APS. The monomer conversion increased from 76.83 to 94.21% as the amount of PAA‐b‐PS increased from 3 to 4 wt%, and then decreased with further increase of PAA‐b‐PS. The particle size decreased and its distribution increased with increasing amount of PAA‐b‐PS. The water resistance and solvent resistance of the polymer films initially increased and then decreased with decreasing mass ratio of butyl acrylate to styrene. © 2014 Society of Chemical Industry     

Synthesis and characterization of polyacrylate composite with thiol‐modified nanosilica as chain transfer agent

Polyacrylate composites with thiol‐modified nanosilica as chain transfer agent were prepared. The FTIR results indicated that the chemical bond has formed between polyacrylate and modified nanosilica. The change of molecular weight distribution proved that the thiol group on the nanosilica surface played the chain transfer agent role just as common thiol. A possible mechanism of modified nanosilica in the polymerization was proposed and the core‐shell may be formed finally. In addition, the dispersion of nanosilica in the polyacrylate also improved as a result of the organic bridge structure between the nanosilica and polyacrylate. The thermal decomposition temperature increased as much as 10°C for polyacrylate with 10 wt % modified nanosilica composites compared to polyacrylate. The coatings hardness increased from 2 to 6 H and the abrasion resistance improved from 28 to 10 mg under the same conditions. Especially, the gloss change of coatings with different content of modified nanosilica indicated that the polyacrylate composites have obviously better aging resistance performance compared to polyacrylate. It may be ascribed to the property that nanosilica can absorb large UV light. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42756.     

Synthesis,characterization, and properties of polystyrene/SiO2 hybrid materials via sol–gel process

Isocyanate‐functionalized polystyrene (P(St‐co‐TMI)) was successfully synthesized by solution free radical polymerization, which was then used to react with (3‐aminopropyl) triethoxysilane (APTES) to prepare a precursor of polystyrene/inorganic composites (PS/SiO₂). To obtain PS/SiO₂ composites with chemical bond, the precursor was mixed with triethoxysilane (TEOS) under the sol–gel reaction condition. The chemical bond between the PS and SiO₂ particles made the crosslink network more stable and avoided aggregation compared with the physical connection and barely mechanical mixing. The Fourier transform infrared (FT‐IR) results indicate that the isocyanate group ( NCO) was completely reacted with APTES. The field‐emission scanning electron microscopy results show that the morphology of composites and the distribution of the particles, which exhibit good compatibility between organic and inorganic phases, and the inorganic particles show good spatial uniformity. The differential scanning calorimetry shows that the glass transition temperature (T_g) of the PS/SiO₂ composites was shifted to high temperature when the amount of APTES increased. The thermal degradation temperature of the PS/SiO₂ composites increases with the increasing of APTES content. Master curves at 200°C are constructed for the storage and loss modulus as well as complex viscosity. POLYM. COMPOS. 36:482–488, 2015. © 2014 Society of Plastics Engineers     

Design strategy for waterborne polyurethane with sodium sulfonate groups on the soft segments

The field of waterborne polyurethane (WPU) is gaining a great deal of momentum from both a commercial and academic sense because of increasing environmental and sustainable awareness. For polyurethane (PU) to be dispersible in water, the hydrophilic groups are very important in the design of the polymer chains. Herein, we present a design strategy for WPU having hydrophilic groups on the soft segments through the reaction of as‐synthesized OH‐terminated poly(ε‐caprolactone) diols containing a sodium sulfonate group with diisocyanate. A stable aqueous dispersion was then obtained, and this was followed by a subsequent chain extension reaction and emulsification. We found that the PU dispersion particles were a core–shell structure with a good particle size distribution, and the obtained films exhibited a low tensile strength and a high elongation at break. This approach provided valuable information for fundamental research in the production, modification, property enhancement, and new applications of these materials. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39657.     

Nanosilica reinforced waterborne siloxane-polyurethane nanocomposites prepared via “click” coupling

In the work, click chemistry coupling reaction was used to modify waterborne polyurethane (WPU) with a silane coupling agent, and then the as-prepared waterborne siloxane-polyurethane dispersion was incorporated into the nanosilica moieties forming the nanosilica reinforced waterborne siloxane-polyurethane (WSPUSi) nanocomposites. WSPUSi was characterized by FTIR, ¹H NMR, X-ray diffraction analysis, mechanical property testing, transmission electron microscopy, and thermogravimetric analysis. In order to highlight the excellent performance of WSPUSi, the traditional WPU/nanosilica composites (TWPUSi) were also fabricated. Comparative study on the water sorption, scanning electron microscopy, acetone and toluene absorption and UV–visible transmission spectroscopy of WSPUSi and TWPUSi with the varying nanosilica was conducted. The research results indicate that WSPUSi nanocomposites with reinforced mechanical properties and thermal stability showed excellent comprehensive performance containing water resistance and solvent resistance in comparison with TWPUSi.     

The chain extender content and NCO/OH ratio flexibly tune the properties of natural rubber‐based waterborne polyurethanes

The effects of chain extender content (ethylene diamine, EDA) and NCO/OH ratio on the properties of natural rubber‐based waterborne polyurethanes (WPUs) were investigated experimentally. The particle size of WPU increased significantly with the NCO/OH ratio, in the presence of the EDA chain extender, while it was unaffected by the EDA content. The water uptake of WPU film increased with the EDA content, while the swelling in various solvents decreased. In a thermal analysis, the second decomposition stage of a WPU film increased with the EDA content and with the NCO/OH ratio that also positively affected the dynamic mechanical and mechanical properties. These factors in WPU films had no the effect on the T_g. The stress–strain curves clearly showed the change in WPU films from soft elastomeric materials to ductile and hard plastics. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42505.     

Preparation and characterization of a polydimethylsiloxane‐modified,epoxy‐resin‐based polyol dispersion and its crosslinked films

Waterborne polydimethylsiloxane‐modified epoxy‐resin‐based polyol dispersions were synthesized by the reaction of 2,4‐toluene diisocyanate with 2,2‐bis(hydroxymethyl) propionic acid, hydroxypropyl‐terminated polydimethylsiloxane (HTPDMS), and bisphenol A epoxy resin based polyol. These HTPDMS‐modified polyol dispersions exhibited a small particle size and an excellent dispersion stability. Two‐component waterborne polyurethane (2K‐WPU) was prepared from the HTPDMS‐modified polyol dispersion and a hydrophilic‐modified polyisocyanate. The structure of the HTPDMS‐modified polyol and its crosslinked 2K‐WPU films (SEFs) were characterized with Fourier transform infrared and NMR spectroscopies. The effects of the HTPDMS content on the mechanical and thermal properties of the resulting SEFs were investigated. The results show that the thermal stability of the crosslinked SEFs was enhanced with increasing HTPDMS content, whereas the modulus, tensile strength, and pencil hardness values of the films decreased with increasing HTPDMS content. Siloxane segments migrated onto the surface during the film‐formation process. The contact angle of the films increased from 71 to 96 °, and the water absorption ratio of the films decreased from 6.6 to 5.0% when the HTPDMS content in the films increased from 0 to 10%. These results indicate that the water resistance of the films was enhanced by the introduction of HTPDMS into the 2K‐WPU networks. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 44342.     

端羟基聚丁二烯改性水性聚氨酯的合成与性能

以端羟基聚丁二烯(HTPB)、聚醚二元醇(N-220)、异佛尔酮二异氰酸酯(IPDI)为主要原料,制备了改性水性聚氨酯(WPU)。研究了端羟基聚丁二烯(HTPB)的含量对聚氨酯乳液粒径、贮存稳定性,以及对涂膜耐水性、力学性能、低温柔韧性的影响。结果表明:在预聚反应中,固定总n(—NCO)∶n(—OH)为1.3,w(DMPA)为6%,HTPB添加量在40%(占聚醚N-220的量)以下时,粒径变化不大,乳液稳定性较好;针对不同HTPB添加量,控制好亲水基团的含量,可以获得分散性良好、贮存稳定的聚氨酯乳液;随着HTPB添加量逐渐增大,涂膜的拉伸强度逐渐增大后变小,断裂伸长率和吸水率逐渐减小后变大,低温柔韧性变好。当HTPB添加量在30%左右,涂膜的综合性能最佳。     

Surface and bulk properties of waterborne polyurethane modified with fluorinated siloxane

Two series of polyester and polyether waterborne polyurethanes (WPUs) modified with poly[(3,3,3‐trifluoropropyl)methylsiloxane] (PTFPMS) were synthesized by prepolymerization method and the effect of PTFPMS on surface and bulk properties were investigated by a variety of experimental methods. FTIR and DSC results showed that the polyester WPU has better compatibility between soft segments and hard segments than polyether WPU in bulk and the degree of phase separation increased in polyester WPU but decreased in polyether WPU with increasing PTFPMS. ARXPS analysis revealed the migration of PTFPMS to WPU surface and the migration ability of Si element was better than F element. AFM images demonstrated that the surface of WPU films became rougher as PTFPMS content increased. The enrichment of PTFPMS with low surface energy and roughened surface imparted good hydrophobicity and oleophobicity to WPU films and polyether WPU has better surface properties compared with polyester WPU. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46473.     

葡萄糖改性水性聚氨酯的合成与表征

采用预聚体合成法,以二羟甲基丙酸（DMPA）、葡萄糖（PG）为亲水扩连剂和交联剂制备一种水性聚氨酯乳液。利用FTIR对胶膜结构进行表征,证实葡萄糖已引入聚氨酯主链。TG分析得出PG改性后的聚氨酯胶膜热稳定性增强。研究了PG用量对该聚氨酯胶膜力学性能的影响,结果表明：随着PG用量的增加,胶膜力学强度得到改善。当PG的用量由0增加至4.68%时,断裂伸长率从529.9%降至276.4%,拉伸强度从10.9 MPa增加至24.2 MPa。     

Synthesis and adhesion properties of waterborne polyurethane dispersions with long‐branched aliphatic chains

In this study, a series of waterborne polyurethanes (WPUs) with different contents of long‐branched aliphatic chains were synthesized through variation of the amount of diol chain extender trimethylol propane monooleate (TMPM). The effects of the TMPM content on the adhesion properties of the WPUs were investigated in terms of their surface tension, interfacial tension, contact angle, and adhesion strength. Fourier transform infrared and ¹H‐NMR spectra demonstrated the successful incorporation of TMPM into the polyurethanes. An increase in the TMPM content produced decreases in the surface tension of the WPUs and the interfacial tension and contact angle between the WPUs and plastic films. This indicated that the wetting properties of the WPUs on the plastic films was improved. The improved wettability enhanced the adhesion strength of the WPUs, and this showed that the long‐branched aliphatic chains could effectively improve the adhesion performance of the WPUs on the plastic films. Moreover, TMPM, with its hydrophobic aliphatic chains, increased the hydrophobicity and thermal stability of the WPU films. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41688.     

Characterization and properties of activated nanosilica/polypropylene composites with coupling agents

In this work, nanosilica/polypropylene composites containing 1 wt% of silica nanoparticles were prepared by melt mixing in a Thermo Haake internal mixer. Prior compounding, nanosilica was subjected to surface activation using sodium hydroxide (NaOH) solution. The effectiveness of the activation process was evaluated by measuring the amount of hydroxyl groups ( OH) on the surface of nanosilica via titration method and supported by FTIR analysis. Two coupling agents namely 3‐aminopropyl triethoxysilane (APTES) and neopentyl (diallyl)oxy, tri(dioctyl) phosphate titanate (Lica 12) were used for surface treatment after activation process. The mechanical properties of polypropylene matrix reinforced with silica nanoparticles were determined by tensile and impact test. Hydroxyl groups on the nanosilica surface played an important role in enhancing the treatment with silane coupling agents. To increase the amount of hydroxyl groups on the nanosilica surface, the optimum concentration of NaOH is 1 mol%. Tensile strength, tensile modulus, and impact strength of nanosilica/PP composites improved with activation process. As the coupling agent is concerned, APTES coupling agent is more pronounced in enhancing the mechanical properties of the composites when compared with Lica 12 coupling agent. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers     

Maleopimaric acid‐modified two‐component waterborne polyurethane for coating applications

Maleopimaric acid (MPA), an important rosin derivative, was used to partially substitute isophthalic acid for the preparation of an anionic polyol (MPP) dispersion. The MPP dispersion was then applied to prepare a novel maleopimaric acid‐modified two‐component waterborne polyurethane (MPP‐2K‐WPU). The influences of NCO:OH molar ratio on the thermal properties, water absorption, surface free energy, and application properties of MPP‐2K‐WPU films were investigated. With increasing NCO:OH molar ratio, the thermal stability, pencil hardness, and ethanol resistance of MPP‐2K‐WPU films were improved, but the water resistance was enhanced firstly and then weakened. The surface free energy of MPP‐2K‐WPU films mainly depended on the dispersion interaction which was related to the structure of macromolecules. In addition, compared with the control sample of PP‐2K‐WPU(1.5:1) film, the MPP‐2K‐WPU(1.5:1) film exhibited improved thermal stability, water resistance, gloss, pencil hardness, and ethanol resistance. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43292.     

Effects of polydimethylsiloxane concentration on properties of polyurethane/polydimethylsiloxane hybrid dispersions

A series of waterborne polyurethane (WPU) derived from isophorone isocyanate and poly(tetramethylene glycol) were modified by hydroxyl‐terminated polydimethylsiloxane (HPMS). The solutions were then cast into films named as PUHS. Rheological behavior of the emulsions were studied using Rheometer and morphology was studied with transmission electron microscope. Meanwhile, the casting films were prepared from the WPU/HPMS hybrid dispersions, and their glass transition behavior, miscibility, water resistance, and medium resistance were studied with differential scanning calorimeter (DSC), wide‐angle X‐ray diffraction (WAXD), and so on. The results revealed that the emulsions' particle size decreases with increasing HPMS content and the particles are more easily affixed to each other when the HPMS content is more than 15%, and emulsions are endowed with pseudoplasticity and thixotropy. WAXD and DSC figures manifested that the casting films all exhibited a certain degree of miscibility. The degrees of crystallinity (x_c) decreased with increasing HPMS content, and the PUHS films were almost amorphous. It is noticed that water and medium absorption increased in the HPMS/PU compared to pure PU, which demonstrate that the membrane surfaces have excellent water and chemical medium repellency. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102:5538–5544, 2006     

尿素对水性聚氨酯性能的影响

以异佛尔酮二异氰酸酯（IPDI）、聚醚220、聚酯二元醇为主要原料,二羟甲基丙酸（DMPA）为亲水性扩链剂,并分别用乙二胺和尿素作扩链剂,合成阴离子型水性聚氨酯乳液。对比2种扩链剂对水性聚氨酯乳液黏度、膜吸水性及玻璃化转变温度（Tg）的影响.结果表明,增加乙二胺的用量,能提高聚氨酯乳液黏度,降低其膜的吸水性,增大聚合物Tg．而增加尿素的用量对聚氨酯乳液黏度和聚合物Tg没有明显影响,但提高了膜吸水性。说明尿素没有起到扩链作用,但可以作为封端剂在聚氨酯分子末端引入胺基。