Effect of silica nanoparticles on structure and properties of waterborne UV-curable polyurethane nanocomposites

UV-curable waterborne polyurethane (WUPU)/silica nanocomposites were prepared using various silica by phase-inversion emulsification method. TEM examinations of nanostructured films indicated that the organic modified nanosilica was well dispersed in the WUPU matrix, while the acid and alkaline silica formed much less compact, or densely aggregated structure. DMA analysis demonstrated that the WUPU/silica nanocomposite films had a broadening of the tanδ peak and shifted to higher temperature. The WUPU/silica nanocomposite films displayed enhanced storage modulus, Shore A hardness, tensile strength without sacrificing high elongation at break compared to that of the pure WUPU film. The resulting nanocomposite films are possibly interesting for the generation of waterborne UV-curable transparent coatings with scratch-resistance.     

纳米二氧化硅水溶胶改性UWPU的研究

通过丙酮法合成光固化水性聚氨酯丙烯酸酯预聚体,用三乙胺中和后在乳化过程中原位引入纳米二氧化硅水溶胶(Wv33、R900、R301)制备二氧化硅/光固化水性聚氨酯(SiO2/UWPU)纳米复合乳液,并进一步通过紫外光固化制备了SiO2/UWPU复合膜。通过电子扫描显微镜(SEM)和电子拉力机研究了不同纳米二氧化硅水溶胶对UWPU/SiO2复合膜的微观结构和力学性能的影响。SEM分析表明表面有机改性的pH值接近中性的硅溶胶(Wv33)较pH为酸性或碱性的硅溶胶在聚氨酯基体中有较好的分散性;应力-应变曲线分析表明Wv33能有效实现对复合膜的增强,即提高了复合膜的储存模量、拉伸强度和邵A硬度。     

Newly UV-curable polyurethane coatings prepared by multifunctional thiol- and ene-terminated polyurethane aqueous dispersions mixtures: Preparation and characterization

A series of newly developed UV-curable polyurethane coatings were prepared by blending multifunctional thiol- and ene-terminated polyurethane aqueous dispersions. The composition, structure, solution stability and mechanical properties of the title coatings were characterized in detail by FT-IR, photo-DSC and DMA measurements. It was found that the resulting polyurethane coatings showed good solution stability and high photopolymerization activity even after a long time (i.e. 1 month). The incorporation of a waterborne polyurethane chain into the both multifunctional thiols and ene monomers promoted their solution stability and avoided any reaction between thiols and ene groups as a result of their high reacting activity in non-aqueous systems. UV-cured films prepared by this method were found to exhibit excellent physical properties with improvements over what can be attained directly with current UV-curable urethane-acrylate based systems. This method allows for the preparation of high performance UV-curable polyurethane aqueous coatings based on thiol-ene chemistry systems.     

Newly UV-curable polyurethane coatings prepared by multifunctional thiol- and ene-terminated polyurethane aqueous dispersions: Photopolymerization properties

A novel approach toward the preparation of newly UV-curable polyurethane coatings composed of multifunctional thiol- and ene-terminated polyurethane aqueous dispersions is presented. By a synergistic combination of polyurethane dispersions synthesis and thiol-ene chemistry, strategies for the preparation of newly UV-curable polyurethane coatings are developed. Photo-DSC, real-time FTIR, DMA and tensile tests measurements are used to investigate the photopolymerization and mechanical behaviors of newly UV-curable polyurethane coatings. The newly polyurethane coatings have 1.5 times higher polymerization rate and final 99% functional groups conversion in air conditions compared to current urethane-acrylate based UV-curable polyurethane dispersions coatings. UV-cured polyurethane films prepared by this method are also found to exhibit increase in Young's modulus and tensile strength at break by 25% and 10%, respectively. These experiment facts suggest that the incorporation of thiol-ene chemistry to the polyurethane dispersion coatings increase their polymerization rate, producing a high degree of cross-linking. This confirms the preparation of the targeted novel UV-curable polyurethane coatings and reveals the dramatic effect that changes in incorporation of thiol-ene chemistry can have on the photopolymerization behaviors of UV-curable polyurethane dispersions coatings systems.     

Polymer/silica nanohybrids by means of tetraethoxysilane sol–gel condensation onto waterborne polyurethane particles

Stable waterborne polyurethane/silica hybrid dispersions were obtained by sol–gel reaction of tetraethoxysilane added to previously synthesized waterborne polyurethane nanodispersions. Two series of polyurethane/silica nanostructures with different silica contents were synthesized using pure polyurethane particles and polyurethane particles previously functionalized with (3-aminopropyl)triethoxysilane (APTES) as colloidal templates. The optimum experimental conditions for tetraethoxysilane sol–gel reaction (T = 75 °C and semi batch polymerization conditions) leading to the formation of silica/polyurethane aqueous nanodispersions were established. The presence of silica was confirmed using TGA, FTIR, ²⁹Si NMR and TEM. TEM images showed an excellent final dispersion of the silica nanoparticles in the polymer matrix when silane functionalized polyurethane nanoparticles were used.     

Abrasion resistance of waterborne polyurethane films incorporated with PU/silica hybrids

We describe polyurethane (PU)/silica hybrids (PSHs) prepared through hydrolysis and condensation reactions of tetraethoxysilane (TEOS) with or without methyltriethoxysilane (MTES) in the presence of polyurethane dispersion, which were subsequently incorporated into waterborne polyurethane (WPU) to prepare composites. The effects of the solid mass ratio of PSHs/WPU on the particle size of composite emulsions, the dispersion of silica nanoparticles in composite films, and the hardness and abrasion resistance of the corresponding films were examined. Composite emulsions possess a nanoscale particle size when incorporated with PSHs prepared using TEOS and MTES as precursors, and are superior to those with PSHs prepared using TEOS alone. Transmission electron microscopy revealed that silica nanoparticles had a uniform distribution in the polymer matrix and agglomerates could be almost completely avoided through in situ modification of silica with Si-CH₃ groups in the polyurethane dispersion. Composite films prepared with this method exhibited a superior hardness and abrasion resistance even at a lower silica content compared with that containing unmodified silica. In particular, optical microscopy and scanning probe microscopy observations demonstrated wear behavior differences among these composite films from the macro- and nanoscale viewpoints, respectively. It is proved that abrasive wear occurs, and surface morphology studies are in accordance with the results of abrasion resistance tests.     

Hybrid polymer latexes: acrylics-polyurethane from miniemulsion polymerization: properties of hybrid latexes versus blends

Hybrid polymer latexes polyurethane/polyacrylic esters, are prepared through miniemulsion polymerization of polyurethane solutions in acrylic monomers. The polyurethanes are prepared by condensation of isophorone diisocyanate on polypropylene glycol (M_n=1000) and butane diol as chain extender. The NCO chain ends being reacted with water (which act as a further chain extender producing some urea bonds). They are miniemulsified in a mixture of methylmethacrylate and butylacrylate monomers, and the miniemulsion are polymerized using benzoylperoxide as initiator. Films were obtained for different hybrid latexes of various compositions. Their mechanical properties have been compared with those of films from the basic components (polyurethane and acrylic latexes), as well as films from blends of these components. Some specific features of the surface of these films are also discussed from microscope images (TEM and AFM) as well as from contact angle measurements.     

Preparation and characterization of waterborne polyurethane/silica hybrid dispersions from castor oil polyols obtained by glycolysis poly(ethylene terephthalate) waste

Castor oil polyols (COLs) have been synthesized from glycolyzed oligoester polyol in order to produce waterborne polyurethane (WPU)/silica hybrid dispersions. Soft drinks poly(ethylene terephthalate) (PET) bottles were depolymerized by glycolysis with different molar ratio of poly(ethylene glycol) ( PEG 400), in the presence of zinc acetate as catalyst. The obtained glycolyzed products were reacted with castor oil (CO) to attain castor oil polyols by the process of transesterification. Five castor oil polyols were used with hydroxyl values of 255, 275, 326, 366 and 426 mg KOH g⁻¹. Several castor oil-based, polyurethane/silica hybrid dispersions having soft segment content of 39.6% to 28.2% and two concentrations of SiO₂ nanoparticles (0.5 and 1.0) have been prepared.The incorporation effect of SiO₂ nanoparticles into the PU matrix and the hydroxyl functionality of the COLs on the thermal and mechanical properties of resulting polyurethane films has been examined by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), differential scanning calorimetry (DSC), thermal gravimetric analysis (TG) and measurement of the mechanical properties. The degree of phase separation (DPS) between oxide nanoparticles and hard segment, and particle size in the polyurethane, depends to some extent on nanosilica content and the hydroxyl functionality of the polyols employed in the polyurethane preparation process.Thermal stability of obtained hybrid materials depends on the hydroxyl functionality of the COLs and nanosilica content. The T_10% and T_50% (the temperature where 10 and 50% weight loss occurred) of WPU films decreased with the rise of OH functionality of castor oil polyols, caused by the increase of hard segment content. Glass transition temperature increased with increasing OH functionality and SiO₂ content. The hardness, adhesion and gloss quality of the polyurethane films were also determined with a view to assessing the effect of mole ratios of PET to glycol in glycolyzed products, the hydroxyl functionality and the SiO₂ content.     

不同聚醚二元醇软段对光固化水性聚氨酯乳液性能的影响

以不同聚醚二元醇、异佛尔酮二异氰酸酯、2,2-双羟甲基丙酸、甲基丙烯酸-2-羟基乙酯为主要原料,通过丙酮法合成光固化水性聚氨酯(WPU)乳液,讨论了不同聚醚软段对光固化WPU乳液性能的影响.结果表明,由聚四氢呋喃醚二元醇PTMG1000和PTMG2000制备的光固化WPU乳液具有较小的粒径和粘度,其交联后的膜具有较高储...     

Synthesis of bis[(4-hydroxyethoxy)phenyl]sulfone containing urethane acrylates and their applications

UV-curing processes are used in industrial applications because of their advantages such as high speed applications and solvent-free formulations at ambient temperature. UV-curable sulfone containing polyurethane acrylates were synthesized from bis[(4-hydroxyethoxy)phenyl]sulfone (BHEPS), polyols, isophorone diisocyanate (IPDI) and 2-hydroxyethyl methacrylate (HEMA). The polyurethane acrylates characterized with ¹H NMR and FT-IR spectroscopies. The UV-cured coatings and films were formulated with polyurethane acrylates, reactive diluents such as dipropyleneglycol diacrylate (DPGDA), 1,6-hexanediol diacrylate (HDDA) and photoinitiator. The water wettability of the UV-cured films was investigated by measuring contact angle. Sulfone containing polyurethane acrylates increase mechanical properties such as pendulum hardness, pencil hardness, tensile strength, and e-modulus values. These mechanical properties and chemical-solvent resistance may have been strongly dependant on the sulfone content and crosslinking density.     

UV-curable PUDs based on sustainable acrylated polyol: Study of their hydrophobic and oleophobic properties

UV-curable polyurethane dispersions (UV-PUDs) are fast expanding commercial applications since they combine benefits of both water-borne as well as UV-curing technologies while addressing many technical, environmental and performance benefits. Varying the compositions and cross-link density of UV-PUD polymeric chain backbone can control the film properties of UV-PUDs. There are many design restrictions posed by availability of commercial materials. In the present research work we demonstrate synthesis and application of a multi-functional acrylate polyol derived from soybean oil, as soft-segment of UV-PUDs. A series of UV-PUDs have been designed for high performance coatings that are specifically hydrophobic and oil-resistant. To this end, UV-PUDs based on acrylated soy-polyol have been further modified by siloxane and perfluoro compounds and their films with varying cross-link density have been investigated. The UV-PUD films were characterized for their film properties, particle size, contact angle and solvent swelling ratio. The outcome of this study provides useful insights into design considerations for hydrophobic and oil-resistant UV-curable coatings.     

Characterization of UV curable hybrid hard coating materials prepared by sol-gel method

Using sol-gel method, UV-curable urethane acrylate resin system was hybridized with inorganic silicate network to produce hybrid coating materials with high anti-abrasive property. In preparation of acrylate/SiO₂ hybrid materials, various acrylic reactants with multi-functional groups in addition to urethane acrylate oligomer as the main network former were employed to obtain more densified organic network structure with a high degree of cross-linking. As a silane coupling agent, 3-methacryloxypropyl-trimethoxysilane (MPTMS) was used to promote interfacial attraction between UV-cured organic acrylate resin and inorganic silicate component in the hybrid. The addition of MPTMS offered significant effect on the improvement of phase compatibility between organic and inorganic phases, which resulted in stable and homogeneous morphology with a dispersion of nano-sized fine silica particles. The results of morphological observation, glass transition behavior, and optical transparency for the hybrid gels provided an evidence for the increased interfacial attraction between two phases. From the Taber abrasion test for the hybrid coating films, it was revealed that there existed optimal ranges of inorganic silicate precursor TEOS and silane coupling agent MPTMS contents for the preparation of UV cured acrylate/SiO₂ hybrid with high abrasion resistant property.     

UV-curable nano-silver containing polyurethane based organic–inorganic hybrid coatings

The preparation of nano-silver containing polyurethane based UV-curable organic–inorganic hybrid coatings that have antibacterial activity is presented in this paper. Trimethoxysilane end-capped bis[(4-β-hydroxyethoxy)phenyl] methyl phosphine oxide urethane was synthesized as a coupling agent and used to improve the compatibility between the organic and inorganic phases of the hybrid coating. Due to its strong antibacterial activity, silver nanoparticles were prepared and added to the nanocomposite formulations. The relationships between the amount of coupling agent and the final coating properties were investigated. The hybrid coatings presented good thermal stability. Tests for abrasion, hardness, gloss, and adhesion of the coatings were also performed. The morphological investigation was performed by SEM to determine the size of the silver nanoparticles. The nano-silver containing coatings exhibited good antibacterial activity against E. coli and S. aureus.     

Hybrid ternary organic-inorganic films based on interpolymer complexes and silica

Homogeneous transparent hybrid films consisting of chitosan (CHI), poly(monomethyl itaconate) (PMMI) and silica were obtained indicating the absence of microphase separation. These ternary hybrid materials are very interesting since materials with high functionality can be obtained presenting different properties from those of the starting materials but with the advantage of preserving the inherent property of each component. The inorganic phase was prepared by sol-gel process of tetraethoxysilane (TEOS). Most of the amine groups from CHI (pK_b 7.7) are quaternized in the acidic medium used in the preparations (pH=2), where a physical crosslinking via hydrogen bonding could occur through carboxyl groups from PMMI. Silica gel obtained from TEOS has been intercalated as a very fine dispersion in the polymer complex formed between CHI and PMMI. Transmission electron microscopy and atomic force microscopy was used to examine the homogeneity of the ternary polymer hybrids (CHI/PMMI/SiO₂), obtained as self-supported films. The results support the nanometer scale dispersion of the phases. Porous silica films with high BET area were obtained by calcination of the hybrid films. The mean pore diameter of these silica films corresponds to the dimension of the polymer domains observed in the pristine hybrid films. Moreover, it was found that the swelling behavior of the samples was influenced by the organic and inorganic phases, where the inorganic phase tends to diminish the swelling.     

Synthesis and cryogenic properties of polyimide-silica hybrid films by sol-gel process

Polyimide-silica hybrid films were prepared from tetraethoxysilane (TEOS) and polyamic acid (PAA) via sol-gel process in the solution of N,N-dimethylacetamide (DMAc). The cryogenic mechanical and electrical properties of polyimide-silica hybrid films were studied taking into account the effects of silica content. The results indicated that the cryogenic modulus increased with the increase of silica content while the tensile strength and failure strain had a maximum value at proper silica contents. Moreover, the tensile strength and modulus of the hybrid films at cryogenic temperature (77 K) were obviously higher than those at room temperature, while the failure strain of the hybrid films was much lower at cryogenic temperature (77 K) than that at room temperature. The mean electrical breakdown strength of the hybrid films was shown to range from 151 to 225 kV/mm at cryogenic temperature (77 K).     

Preparation and characterization of UV-curable urethane acrylate oligomers modified with cycloaliphatic epoxide resin

The UV-curable urethane acrylate oligomers modified with cycloaliphatic epoxide resin, including polyether-modified cycloaliphatic polyurethane acrylate (CE-MP-UA) and oleic acid-modified cycloaliphatic polyurethane acrylate (CE-OA-UA), have successfully been synthesized and characterized by ¹HNMR and FTIR. The kinetics of the synthesis processes are studied in this paper. The effects of the molecular structure of the oligomers on the properties of cured film, including pencil hardness, impact resistance, adhesion and boiling water resistance, are discussed in detail. The experimental results indicate that the films formed by CE-OA-MP oligomers show good comprehensive performance, especially good adhesion and boiling water resistance due to the numerous hydroxyl groups, flexible segment and alicyclic structure of the oligomers. The results reveal that the alicyclic structure in the oligomer molecular make-up can effectively improve the adhesion of UV-curable coatings.     

Modification of polyurethane‐coated fabrics by sol–gel thin films

Sol–gel derived silica and hybrid films from tetraethoxysilane (TEOS) and 3‐glycidyloxypropyltrimethoxysilane (GLYMO) were deposited by dip‐coating, in order to find the best treatment. GLYMO‐based treatments preserved textile feel of the material. The coatings were characterized by infrared spectroscopy (IR), scanning electron microscopy (SEM), energy‐dispersive X‐ray spectroscopy, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and water contact angle measurement. IR spectra confirmed the existence of silicate network and successfully conducted modification for both precursors. DSC and TGA showed that the conditions of hydrolysis had greater influence on TEOS than GLYMO‐based treatments. Both treatments shifted the degradation onset to higher temperatures. SEM images showed that polyurethane surface and pores were completely covered and filled by silica or hybrid thin films forming a composite organic–inorganic coating. Hydrophobic effect was preserved for all the samples, except for a single treatment of the GLYMO, due to its polar epoxy group. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39914.     

Polydimethylsiloxane (PDMS)-based antibacterial organic–inorganic hybrid coatings

UV-curable antibacterial organic–inorganic hybrid coatings were prepared by sol–gel method. Triethoxysilane-terminated poly(dimethylsiloxane) (TESi-PDMS) as a new coupling agent to improve the compatibility between organic and inorganic phases was synthesized. PDMS-based urethane methacrylate oligomer was obtained by reacting isophorone diisocyanate with hydroxyethyl methacrylate and hydroxyl-terminated PDMS. The formulations were applied onto polycarbonate panels and then cured by UV radiation. Physical properties of UV-cured free films such as gel content, stress–strain, and conversion of acrylate double bond were examined. In addition, the antibacterial effects of the coatings were investigated. Nanosilver-containing formulations exhibited high antibacterial effect against Escherichia coli and Staphylococcus aureus. Thermogravimetric analysis indicated that thermal stability of the hybrids was significantly higher than the organic polymer. Contact angle measurement showed that addition of silane precursor increased the contact angle from 95° to 110°.     

Polyamide-6,6/in situ silica hybrid nanocomposites by sol-gel technique: synthesis, characterization and properties

The organic-inorganic hybrid nanocomposites comprising of poly(iminohexamethyleneiminoadipoyl), better known as Polyamide-6,6 (abbreviated henceforth as PA66), and silica (SiO₂) were synthesized through sol-gel technique at ambient temperature. The inorganic phase was generated in situ by hydrolysis-condensation of tetraethoxysilane (TEOS) in different concentrations, under acid catalysis, in presence of the organic phase, PA66, dissolved in formic acid. Infrared (IR) spectroscopy was used to monitor the microstructural evolution of the silica phase in the PA66 matrix. Wide angle X-ray scattering (WAXS) studies showed that the crystallinity in PA66 phase decreased with increasing silica content. Atomic force microscopy (AFM) of the nanocomposite films revealed the dispersion of SiO₂ particle with dimensions of <100 nm in the form of network as well as linear structure. X-ray silicon mapping further confirmed the homogeneous dispersion of the silica phase in the bulk of the organic phase. The melting peak temperatures slightly decreased compared to neat PA66, while an improvement in thermal stability by about 20 °C was achieved with hybrid nanocomposite films, as indicated by thermogravimetric analysis (TGA). Dynamic mechanical analysis (DMA) exhibited significant improvement in storage modulus (E′) for the hybrid nanocomposites over the control specimen. An increase in Young's modulus and tensile strength of the hybrid films was also observed with an increase in silica content, indicating significant reinforcement of the matrix in the presence of nanoparticles. Some properties of the in situ prepared PA66-silica nanocomposites were compared with those of conventional composites prepared using precipitated silica as the filler by solution casting from formic acid.     

Surface and mechanical properties of hydrophobic silica contained hybrid films of waterborne polyurethane and fluorinated polymethacrylate

The surface and mechanical properties of hybrid films of waterborne polyurethane (WPU) and fluorinated polymethacrylate (FPMA), and high-hydrophobic silica (SiO₂) contained hybrid films of FPMA/WPU were investigated. X-ray photoelectron spectroscopy confirmed that the surfaces of hybrid films exhibited notable fluorine enrichment. Scanning electron microscopy observation demonstrated that micro-scale rough structures consisted of sub-micro papillae and micro-scale wrinkles formed on the surfaces of FPMA/WPU. This was attributed to the enhanced phase separation of WPU and the incompatibility of low-surface-energy FPMA and WPU. Colloidal SiO₂ was modified by polydimethylsiloxane and the modified SiO₂ was reactive and high-hydrophobic. After the addition of reactive SiO₂, the rough structures became micro-scale striped wrinkles studded with nano- and sub-micro papillae formed by the high-hydrophobic SiO₂. The combination of the fluorine enrichment and the rough structures accounted for the high hydrophobic FPMA/WPU film and superhydrophobic SiO₂/FPMA/WPU film.