Polyurethane Acrylate Matrix Research Articles

Construction of Photoinitiator Functionalized Spherical Nanoparticles Enabling Favorable Photoinitiating Activity and Migration Resistance for 3D Printing.

A straight-forward method was exploited to construct a multifunctional hybrid photoinitiator by supporting 2-hydroxy-2-methylpropiophenone (HMPP) onto a nano-silica surface through a chemical reaction between silica and HMPP by using (3-isocyanatopropyl)-triethoxysilane (IPTS) as a bridge, and this was noted as silica-s-HMPP. The novel hybrid-photoinitiator can not only initiate the photopolymerization but also prominently improve the dispersion of nanoparticles in the polyurethane acrylate matrix and enhance the filler-elastomer interfacial interaction, which results in excellent mechanical properties of UV-cured nanocomposites. Furthermore, the amount of extractable residual photoinitiators in the UV-cured system of silica-s-HPMM shows a significant decrease compared with the original HPMM system. Since endowing the silica nanoparticle with photo-initiated performance and fairly lower mobility, it may lead to a reduction in environmental contamination compared to traditional photoinitators. In addition, the hybrid-photoinitiator gives rise to an accurate resolution object with a complex construction and favorable surface morphology, indicating that multifunctional nanosilica particles can be applied in stereolithographic 3D printing.

Functionalized Cellulose Nanocrystals as Active Reinforcements for Light-Actuated 3D-Printed Structures.

Conventional manufacturing techniques allow the production of photoresponsive cellulose nanocrystals (CNC)-based composites that can reversibly modify their optical, mechanical, or chemical properties upon light irradiation. However, such materials are often limited to 2D films or simple shapes and do not benefit from spatial tailoring of mechanical properties resulting from CNC alignment. Herein, we propose the direct ink writing (DIW) of 3D complex structures that combine CNC reinforcement effects with photoinduced responses. After grafting azobenzene photochromes onto the CNC surfaces, up to 15 wt % of modified nanoparticles can be introduced into a polyurethane acrylate matrix. The influence of CNC on rheological properties allows DIW of self-standing 3D structures presenting local shear-induced alignment of the active reinforcements. The printed composites, with longitudinal elastic modulus of 30 MPa, react to visible-light irradiation with 30-50% reversible softening and present a shape memory behavior. The phototunable energy absorption of 3D complex structures is demonstrated by harnessing both geometrical and photoresponsive effects, enabling dynamic mechanical responses to environmental stimuli. Functionalized CNC in 3D printable inks have the potential to allow the rapid prototyping of several devices with tailored mechanical properties, suitable for applications requiring dynamic responses to environmental changes.

Covalent bonding effects on spectral, photophysical and generation properties of indocarbocyanine dyes in polyurethanes

Spectral, photophysical and generation properties of symmetrical cationic cyanine dyes have been investigated in the polyurethane matrices, similar by the structure, but different by the polymerization method. The cyanine dye doped polyurethane, synthesized by a polycondensation reaction, provides laser active elements with significantly improved photostability, efficiency and operation lifetime, compared to those for the polyurethane acrylate matrix, hardened by a radical photopolymerization method. Changing the liquid (ethanol) medium to polymers causes an increase of fluorescence quantum yield and efficiency. For the first time, covalent bonding between a cyanine dye and a polyurethane has been studied, and high fluorescence quantum yield and generation efficiency have been observed.

Anisotropic localized surface plasmon resonance of vanadium dioxide rods in flexible thermochromic film towards multifunctionality

Plasmonic thermochromic films are promising for smart window applications. Hereby, we develop a flexible plasmonic thermochromic film towards multifunctionality. The double-layer film consists of a bottom layer of W/Mg co-doped vanadium dioxide (VO 2 ) rods in a polyurethane acrylate matrix and a top layer of hollow silica spheres (HSSs). Based on the finite-difference time-domain (FDTD) method, we demonstrate for the first time, a transverse and a longitudinal mode of VO 2 localized surface plasmonic resonance (LSPR) in near- and mid-infrared bands, respectively, and only the transverse mode contributes to the solar energy modulation performance. The film shows a luminous transmittance of 46.2%, a solar energy modulation of 10.8%, and a critical transition temperature of 36.9 °C. The HSSs overcoating enhances the surface hydrophilicity and thermal insulation, which give rise to more favored functionalities for windows. • The first identification of anisotropic LSPR on VO 2 rods. • FDTD method proves only transverse mode of LSPR contributes to solar modulation. • Simultaneous improved flexibility, wettability, solar and thermal modulations. • The thermochromic film is promised for multifunctional smart windows.

Spectral, photophysical and lasing properties of Rhodamine dyes in the polyurethane acrylate matrix

Effects of the solvents, different by physical parameters, on the spectral, photophysical, lasing properties and molecule associations of the Rhodamine dyes, incorporated to the polyurethane acrylate matrix were investigated. The role of the solvent polarity in the dye luminescence, photostability and generation of the dye-doped polymer active media was studied. Polarity characteristics of the solvents were founded out to affect considerably initial concentrations and aggregation processes of the organic dyes in the polymer matrices. The use of highly polar solvents for the development of the dye lasers provides improved photostability and generation parameters of the laser dye-doped solid-state active elements.

Chemical modification of graphene oxide to reinforce the corrosion protection performance of UV-curable polyurethane acrylate coating

An eco-friendly polyurethane acrylate (PUA) /functionalized graphene oxide nanocomposite coating with excellent corrosion resistance was prepared by UV curing technology. Graphene oxide (GO) was covalently modified by the reactive PUA molecules to improve its dispersibility and the interaction with the polymer matrix, which was verified by the results obtained from Fourier transformed infrared spectroscopy (FTIR), X-ray diffraction (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM) and atomic force microscopy (AFM). Subsequently, the PUA functionalized GO (denoted as PGO) nanosheets were doped into the PUA resin matrix. The structures and morphologies of the blank PUA coating, the PUA/GO nanocomposite coating and the PUA/PGO nanocomposite coating were characterized by field emission scanning electron microscope (FESEM), and their corrosion resistance was investigated via electrochemical impedance spectroscopy (EIS) and salt spray test. Results revealed that the incorporation of PGO nanosheets remarkably improved the corrosion resistance of the PUA matrix due to their good dispersion, outstanding barrier properties and strong bonding strength with the polymer matrix.

Polyurethane acrylate-supported rGO/TiO2 electrical conductive and antibacterial nanocomposites

Polyurethane acrylate (PUA)-supported rGO/TiO2 electrical conductive and antibacterial nanocomposites were synthesized via in-situ polymerization. The well-dispersed rGO/TiO2 can serve as photoinitiator and give PUA material antibacterial property at the same time. The excellent UV-curing and antibacterial activity could be explained that the synergistic effect of rGO and TiO2, which could promote the effective electron/hole separation and thus generate various reactive species. After dopped the rGO/TiO2 into the PUA matrix, the PUA film became electric conductive. The obtained nanocomposites will have promising applications in high performance antibacterial coatings.

Designing nanoporosity in a swollen polymer for the controlled release of a highly volatile fragrance

AbstractControlling the fragrance release profile, especially the highly volatile top note, can prolong the desired scent of the fragrance. Here, the porosity of a swollen cross‐linked polyurethane acrylate (PUA) polymer, which is tuned by the length of a modulator, can influence the evaporation rate of the top note. In particular, the evaporation rate of benzyl acetate (BA), a common top note, is reduced by a factor of 6.5 (from 134 to 17 mg m–2 min–1) when BA is released from the best‐performing PUA against a reservoir of BA. The average diameter of an opening in the fragrance‐loaded PUA is ~6 nm, as determined by the thermoporosimetry approach. Such a pore size can effectively control the evaporation rate of BA, as predicted by the theoretical model, which reveals that a pore diameter of <16 nm is required. Computational modelling reveals the optimal chain length for a modulator used for the sustained released of fragrance, confirming the experimental data. Finally, BA continues to be released from the PUA matrix for a prolonged period, even after 3 months, whereas the same quantity of BA would completely evaporate after 1 week in the absence of PUA matrix. Approximately 50wt% of BA remains after 60 days, making it one of the best techniques in sustaining the release of a top note.

Dual-functional photoinitiators and photo-grafting of cotton cellulose nanowhiskers

Novel dual-functional photoinitiators (DFP) of cotton cellulose nanowhiskers (CNW) were prepared and photo-grafted onto macromolecular networks by photolysis and photopolymerization. DFP were prepared with incorporating a fragmental photoinitiator, 2-hydroxyl-2-methyl-1-phenyl-1-propanone, onto isophorone diisocyanate modified CNW. Characterizations were conducted to verify the feasibility of the synthesis by Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, nuclear magnetic resonance spectroscopy, and X-ray powder diffraction, respectively. Thermal stability was investigated by thermogravimetric analysis. The photopolymerization kinetics of DFP in polyurethane acrylate (PUA) oligomers were investigated by real time Fourier transform infrared and UV–vis spectroscopy. Scanning electron microscope was performed to study the fracture surfaces of UV-cured PUA films. The mechanical properties of PUA/DFP films were studied, exhibiting that 5wt.% DFP significantly reinforced elongation at break of PUA matrix by 80%. It was found that DFP could simultaneously effectively initiate the photopolymerization and photo-graft CNW onto UV-cured PUA networks.

Polyurethane acrylate networks including cellulose nanocrystals: a comparison between UV and EB- curing

A water-based polyurethane (PUR) acrylate water emulsion was selected as a radiation curable matrix for preparing nanocomposites including cellulose nanocrystals (CNC) prepared by controlled hydrolysis of Ramie fibers. Cross-linking polymerization of samples prepared in the form of films or of 1mm-thick bars was either initiated by exposure to the 395nm light of a high intensity LED lamp or by treatment with low energy electron beam (EB). The conversion level of acrylate functions in samples submitted to increasing radiation doses was monitored by Fourier Transform Infrared Spectroscopy (FTIR). Differential Scanning Calorimetry (DSC) and Dynamic Mechanical Analysis (DMA) were used to characterize changes in the glass transition temperature of the PUR-CNC nanocomposites as a function of acrylate conversion and of CNC content. Micromechanical testing indicates the positive effect of 1wt% CNC on Young's modulus and on the tensile strength at break (σ) of cured nanocomposites. The presence of CNC in the PUR acrylate matrix was shown to double the σ value of the nanocomposite cured to an acrylate conversion level of 85% by treatment with a 25kGy dose under EB, whereas no increase of σ was observed in UV-cured samples exhibiting the same acrylate conversion level. The occurrence of grafting reactions inducing covalent linkages between the polysaccharide nanofiller and the PUR acrylate matrix during the EB treatment is advanced as an explanation to account for the improvement observed in samples cured under ionizing radiation.

Reinforcement of organo-modified molybdenum disulfide nanosheets on the mechanical and thermal properties of polyurethane acrylate films

Molybdenum disulfide (MoS2) nanosheets were non-covalently organo-modified by electrostatically interacting with cetylpyridinium chloride (CPC) and then were used to reinforce the properties of polyurethane acrylate (PUA) resin for the first time. Benefited from the alkyl chain of CPC, the modified MoS2 nanosheets can be well dispersed in PUA matrix. Notably, inclusion of 0.5 wt% CPC-MoS2 leads to a 11.7 °C increase in the temperature corresponding to 50 wt % weight loss, indicating the enhanced thermal stability of PUA nanocomposites. Moreover, the improvement in tensile strength, work of fracture and storage modulus (at −75 °C) of PUA/f-MoS2 nanocomposites can reach up to 37.4%, 41.9% and 102.0% respectively. This substantial nano-reinforcement is mainly attributed to the proper organic modification and inherent feature of MoS2 nanosheets. The strong interfacial adhesion within PUA/f-MoS2 nanocomposites can efficiently transfer the load from weak polymer chains to robust MoS2 nanosheets.

Preparation and property of UV-curable polyurethane acrylate film filled with cationic surfactant treated graphene

The preparation of nanocomposite films composed of UV-curable polyurethane acrylate (PUA) and modified graphene were demonstrated in this paper. Cetyl trimethyl ammonium bromide modified graphene (CTAB-G) was prepared via intercalation of cationic surfactant and subsequently incorporated into PUA by UV curing technology. Fourier transform infrared spectra, wide-angle X-ray diffraction, scanning electron microscopy and transmission electron microscopy were used to characterize the structure and morphology of CTAB-G, as well as CTAB-G/PUA nanocomposite films. The results revealed that the CTAB-G sheets were layer-by-layer structure and dispersed uniformly in PUA matrix. Thermal gravimetric analysis showed that the thermal stabilities of UV-curable PUA nanocomposite films in this work were much higher than that of PUA nanocomposites previously reported. Dynamic mechanical analysis indicated that the dynamic mechanical properties of nanocomposite films were greatly enhanced in the presence of modified graphene sheets. In addition, the CTAB-G/PUA nanocomposite films exhibited improved dielectric properties and electrical conductivities compared with the pure PUA.

Fabrication of UV-curable polyurethane acrylate composites containing surface-modified boron nitride for underwater sonar encapsulant application

UV-curable polyurethane acrylate (PUA) is currently used as an encapsulant for undersea sonar devices, and new, desirable polymeric materials should have lower swelling ratios when in contact with seawater and paraffin oil, along with better mechanical strength, when compared to PUA after impregnation. We blended PUA with boron nitride (BN) to fabricate these desirable composites for sonar encapsulants. PUA-coated BN was prepared and was found to have better interfacial adhesion between the PUA matrix and the BN filler. The surface-modified filler showed enhanced dispersibility and affinity due to the surface treatment with functional groups that affected the surface free energy and the structural similarity of the doped crystallized diisocyanate molecule in the matrix. Studies of these composites showed that the swelling ratios decreased with increasing BN–PUA content. The tensile strength of the BN–PUA/PUA composite in either seawater or paraffin was higher than that of the BN/PUA composite as the immersion time increased. We conclude that these composites are promising materials for use as sonar encapsulants and can significantly improve both mechanical strength and long term stability.

Grafting photosensitive polyurethane onto colloidal silica for use in UV-curing polyurethane nanocomposites

The colloidal silica was modified with 3-aminopropyltrimethoxysilane (APTES), and then further treated with NCO-terminated poly (ethylene glycol) methacrylate based oligomer to yield a photosensitive polyurethane modified silica (PU-silica). IR and TGA results confirmed the existence of grafted PU chains at the surface of silica. In compared to silica modified with the silane coupling agents (APTES, MEMO), the grafted PU chains enhanced interfacial interaction and compatibility between silica and polyurethane acrylate (PUA) matrix, which was further proved by rheological behavior and DMA analysis. The SEM showed that small PU-silica clusters were homogeneously dispersed in PUA matrix. The PU-silica nanoparticles functioned effectively as a multifunctional cross-linker as well as a reinforcing filler and significantly enhanced the Young's modulus, tensile strength, and thermal stability of PUA nanocomposites.

Properties of crosslinked polyurethanes obtained by acrylic side-group polymerization and of their blends with various plant oils

Novel polyurethane elastomers have been developed to incorporate plant oil into their matrix. Bisphenol A glycerolate diacrylate was used as a chain extender for the polyurethane prepolymer obtained from poly(tetramethylene oxide) glycol and 1,6-hexane diisocyanate. The curing of the polyurethane acrylate matrix in the presence of the plant oil results in a network matrix which includes renewable resources in their structure. The effects of the inclusion of different vegetable oil (such as soybean oil, rapeseed oil, cotton oil, or sunflower oil) into the crosslinked polyurethane acrylates matrix were studied by evaluating various properties of the films such as the thermal behavior, the tensile properties, and the surface properties. The increases in chain extender content determine an increase of the thermal stability (the 10% weight loss decomposition temperatures increase from 325 to 375°C) and mechanical strength (from 3 to 9 MPa). Contact angle measurements have shown that the hydrophobic property of the films surface slightly increased with the incorporation of plant oil into the crosslinked polyurethane matrix. In addition, polyurethane/plant oil blends exhibit enhanced mechanical strength (from 3 to 9.8 MPa), as well as an increased roughness reaching a maximum average (113 nm) in the case of cotton oil. All polyurethane/plant oil blend present higher values for glass transition temperature and slightly enhanced values for thermal stability. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

UV-Curable Functionalized Graphene Oxide/Polyurethane Acrylate Nanocomposite Coatings with Enhanced Thermal Stability and Mechanical Properties

Functionalized graphene oxide (FGO) was synthesized and subsequently incorporated into polyurethane acrylate (PUA) by UV curing technology. The structural and morphological features of FGO/PUA nanocomposite coatings were characterized by FTIR, XRD, and TEM. The results showed that FGO sheets were uniformly dispersed into the PUA matrix and formed the strong interfacial adhesion with PUA owing to the formation of the cross-linking networks between FGO and PUA after UV curing. The incorporation of FGO effectively enhanced the thermal stability and mechanical properties of host polymer. The initial degradation temperature of the PUA composite with 1.0 wt % FGO was increased to 316 °C from 299 °C for neat PUA. Meanwhile, the storage modulus and tensile strength of the PUA composite with 1.0 wt % FGO were also improved by 37% and 73%, respectively, compared with those of neat PUA. The slight increase in glass transition temperature (Tg) of the composites was observed upon the incorporation of FGO. By contrast,...

Preparation and characterization of UV-cured polyurethane acrylate/ZnO nanocomposite films based on surface modified ZnO

A series of polyurethane acrylate (PUA)/ZnO nanocomposite films with different ZnO contents were prepared via a UV-curing system. To ensure good dispersion in the PUA matrix, ZnO nanoparticles were modified with a silane coupling agent and confirmed by FT-IR analysis. The morphological structures, thermal properties, mechanical properties and water transfer properties of the prepared films were investigated as a function of their ZnO concentration. WAXD and SEM analyses showed that the surface-modified ZnO nanoparticles were homogeneously dispersed in the PUA matrix and the molecular ordering increased with increasing ZnO content. Compared with neat PUA, the hardness and elastic modulus in films increased from 0.03 to 0.056GPa and from 2.75 to 3.55GPa, respectively. Additionally, the water uptake and WVTR in the PUA/ZnO nanocomposite films decreased as the ZnO content nanoparticles increased, which may come from enhanced molecular ordering and hydrophobicity in films. UV light below approximately 450nm can be efficiently absorbed by incorporating ZnO nanoparticles into a PUA matrix, indicating that these composite films exhibit good weather ability and UV-shielding effects. The enhanced physical properties achieved by incorporating modified ZnO nanoparticles can be advantageous in various applications, whereas the thermal stability of the composite films should be increased.

Enhancement of electro-optical properties in holographic polymer-dispersed liquid crystal films by incorporation of multiwalled carbon nanotubes into a polyurethane acrylate matrix

Holographic polymer-dispersed liquid crystal (HPDLC) films were fabricated with varying amounts of multiwalled carbon nanotubes (MWCNTs) to optimize the electro-optical performance of the HPDLC films. The MWCNTs were well dispersed in the prepolymer mixture up to 0.5 wt%, implying that polyurethane acrylate (PUA) oligomer chains wrap the MWCNTs along their length, resulting in high diffraction efficiency and good phase separation. The hardness and elastic modulus of the polymer matrix were enhanced with increasing amounts of MWCNTs because of the reinforcement effect of the MWCNTs with intrinsically good mechanical properties. The increased elasticity of the PUA matrix and the immiscibility between the matrix and the liquid crystals (LCs) gradually increased the diffraction efficiency of the HPDLC films. However, the diffraction efficiency of HPDLC films with more than 0.05 wt% MWCNTs was reduced, caused by poor phase separation between the matrix and LCs because of the high viscosity of the reactive mixture. HPDLC films showing a low driving voltage (<3 V µm−1), a fast response time (<10 ms) and a high diffraction efficiency (>75%) could be obtained with 0.05 wt% MWCNTs at 40 wt% LCs. Copyright © 2010 Society of Chemical Industry

Morphological analysis of photocured polyurethane acrylate networks. Correlation with viscoelastic properties

In this paper, we investigate the final morphology of photocured polyurethane acrylates based on polypropylene oxide by means of Transmission Electron Microscopy (TEM), Small Angle X-ray Scattering (SAXS), and dynamic mechanical measurements. Two interrelated structural features on two different size scales can occur in these systems. TEM analysis demonstrates the presence of inhomogeneities on the length scale of 10–200 manometers, mostly constituted by clusters of small hard units (diacrylated diisocyanate) connected by polyacrylate chains. The bimodal shape of the dynamic mechanical relaxation spectra corroborates this two-phase structure. Besides, a suborganization of the reacted diisocyanate hard segments inside the polyurethane acrylate matrix is revealed by SAXS measurements, depending on the nature of the hydroxylacrylate used for the synthesis of the precursor. Finally, UV-exposure time is found to induce modifications on the viscoelastic properties of the final network, even at high double-bond conversion: this effect can be due to a postreaction and to an increase of the crosslinking density inside the hard segments domains. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 919–937, 1999

Spectral-luminescence and lasing properties of the pyrromethene dye PM-567 in ethanol and in a polymer matrix

An investigation was made of the spectral-luminescence and lasing properties of the pyrromethene dye PM-567 in ethanol and in a polyurethane acrylate matrix. A high lasing efficiency (up to 65%) of PM-567 in the polymeric medium was demonstrated in a dispersive two-prism cavity under nanosecond pumping with the second harmonic of an Nd3+:YAG laser. An analysis was made of the reasons for the high efficiency of this dye and its operational lifetime in the polymeric matrix was determined.