Polyurethane Acrylate Oligomer Research Articles

Synthesis of vinyl functionalized polyurethane acrylate oligomers and their photopolymerization via thiol-ene click reaction

Functional polyvinylethylene glycols (PVEGs) with different central structures were synthesized by Pd/B synergistic catalysts and reacted with isophorone diisocyanate (IPDI) and 2-hydroxyethyl methacrylate(HEMA) to prepared pendent vinyl-functional polyurethane acrylates (VFPUAs). The photopolymerization of the obtained VFPUAs with pentaerythritol tetra(3-mercaptopropionate) (PETMP) in the presence of a photoinitiator proceeded smoothly via thiol-ene photo-click reaction to give a series of crosslinked materials by the variation of the chemical structure of VFPUAs and a ratio of thiols and enes. The curing behavior was studied by FT-IR and the properties of crosslinked materials were characterized by the test of gel content, swelling ratio and water absorption. The dynamic mechanical properties, mechanical properties, thermogravimetry and surface properties of the crosslinked materials were investigated and the performance of coating for the crosslinked film materials was also characterized. The crosslinked film materials can be further functionalized by post-crosslinking modification through thiol-ene photo-click reaction.

3D Printing of Branched Polyurethane with Tough Mechanical Properties for Stretchable Sensors

The poor mechanical properties and difficulties in manufacturing complex structures seriously limit the applications of elastomers especially in flexible electronic sensor. Herein, a series of polyether amine (PEA) grafted polyurethane acrylate oligomers (PUA‐g‐PEAs) and the corresponding low‐viscosity UV‐curable flexible 3D printing elastomers (PEA‐1/IDAs) are synthesized. The results show that a certain amount of PEA branch exactly has strengthening and toughening effect on polyurethane, resulting in 12% increase in tensile strength and 44% increase in elongation at break of PUA‐g‐PEA‐1. When mixed PUA‐g‐PEA‐1with acrylimorpholine and IDA in the ratio of 3:5:2, PEA‐1/IDA‐20 with best overall mechanical properties is obtained. Its tensile strength and elongation at break are 18.5 MPa and 297.4%, respectively. The unprecedented fatigue resistance of PEA‐1/IDA‐20 ensures that it can withstand 100 compression cycles at 80% strain without damage. Besides, piezoresistive sensors and wearable finger guard sensors are fabricated by laminating a layer of conductive hydrogel on the surface of the 3D‐printed devices. The impressive mechanical properties and 3D printing producing process of this branched PUA endow it with great potentials in advanced electronic sensors.

Polyurethane Acrylate Oligomer (PUA) Microspheres Prepared Using the Pickering Method for Reinforcing the Mechanical and Thermal Properties of 3D Printing Resin

Some photosensitive resins have poor mechanical properties after 3D printing. To overcome these limitations, a polyurethane acrylate oligomer (PUA) microsphere was prepared using the Pickering emulsion template method and ultraviolet (UV) curing technology in this paper. The prepared PUA microspheres were added to PUA-1,6-hexanediol diacrylate (HDDA) photosensitive resin system for digital light processing (DLP) 3D printing technology. The preparation process of PUA microspheres was discussed based on micromorphology, and it was found that the oil-water ratio of the Pickering emulsion and the emulsification speed had a certain effect on the microsphere size. As the oil-water ratio and the emulsification speed increased, the microsphere particle size decreased to a certain extent. Adding a suitable proportion of PUA microspheres to the photosensitive resin can improve the mechanical properties and thermal stability. When the modified photosensitive resin microsphere content was 0.5%, the tensile strength, elongation at break, bending strength, and initial thermal decomposition temperature were increased by 79.14%, 47.26%, 26.69%, and 10.65%, respectively, compared with the unmodified photosensitive resin. This study provides a new way to improve the mechanical properties of photosensitive resin 3D printing. The resin materials studied in this work have potential application value in the fields of ceramic 3D printing and dental temporary replacement materials.

A new one-component electrically conductive adhesive with excellent electrical conductivity and mechanical properties using tetra-functional polyurethane acrylate oligomers and silver particle fillers

Electrically conductive adhesives (ECAs) are mainly used in integrated circuit (IC) packaging, light-emitting diode (LED) packaging and other electronic industries to replace traditional solders and lead-free solders. The electrical conductivity and mechanical properties are contradictory with an increase in the content of conductive fillers. Therefore, there is a continuous need to improve electrical conductivity without serious damage to the mechanical properties of ECAs. In this work, a tetra-functional polyurethane acrylate oligomer was used as the main composition of silver filled one-component ECAs to improve performance. By introducing the tetra-functional oligomer, low volume resistivity with good adhesion characteristics was achieved. The volume resistivity and lap shear strength of the silver flake filled ECAs were studied systematically. The ECA with 30.6 vol% content of silver flakes exhibits low volume resistivity of 1.02 × 10−7 Ω m, with a lap shear strength of 8.995 MPa.

Castor oil‐based UV‐curable polyurethane acrylate resins for digital light processing (DLP) 3D printing technology

AbstractIn this work, a novel UV‐curable polyurethane acrylate (PUA) oligomer was developed from castor oil (CO). Reaction monitoring and structures of the PUA oligomer were characterized by Fourier transform infrared (FTIR) and 1H nuclear magnetic resonance (NMR). Subsequently, a series of UV‐curable resins were prepared by combining PUA with different reactive diluents, and their effect on thermal and mechanical properties was investigated. From the overall characterization trend, it was observed that the formulation containing trimethylolpropane triacrylate (TMPTA) showed the highest mechanical strength and thermal stability. Whereas the formulation containing isobornyl acrylate (IBOA) showed the least performance, and dipropyleneglycol diacrylate (DPGDA) showed properties ranging between TMPTA and IBOA. Furthermore, incorporating 1% TiO2 into the formulation increases the resin's viscosity and mechanical properties without disturbing its thermal stability. This work offered a simple method to prepare vegetable oil‐based high‐performance PUA resins that could be used in the 3D printing industry for general‐purpose prototyping applications to make architectural models, automotive components, and medical components.

Flame-Retardant Solid Polymer Electrolyte Based on Phosphorus-Containing Polyurethane Acrylate/Succinonitrile for Lithium-Ion Batteries

A flame-retardant solid polymer electrolyte (FR-SPE) membrane was successfully designed through UV-curing flame-retardant polyurethane acrylate (PUA) oligomers, succinonitrile, aluminum oxide (Al2O3), and lithium salt. The flame retardant PUA is formed by grafting reactive flame-retardant 9,10-dihydro-9-oxa-10-phenanthrene-10-oxide (DOPO) on the main chain of the oligomer. The cross-linked PUA ensures excellent mechanical properties and high flame retardancy of FR-SPE. Moreover, the flame retardancy of the FR-SPE can reach the V-0 level of the UL-94 test when the grafting rate of DOPO on PUA reached 39%, and the obtained FR-SPE achieves a high ionic conductivity of 2.66 × 10–4 S cm–1 at room temperature, a wide electrochemical stability window of 5 V, and a high lithium-ion transfer number of 0.55. Moreover, FR-SPE shows a stable lithium plating/stripping response for over 600 h under a constant current density of 0.1 mA cm–2. Meanwhile, the cell of LiFePO4/FR-SPE/Li4Ti5O12 has excellent cycling stability (144.6 mA h g–1 at 0.2 C after 100 cycles) and rate capability (107.4 mA h g–1 at 5 C). In addition, the electrolyte has no adverse effect on the cycle performance of batteries with graphite electrodes. Thus, such cross-linked flame-retardant SPEs are argued to provide an effective method for more broadly enhancing lithium battery safety and performance.

Synthesis and properties of polyurethane acrylate oligomer based on polycaprolactone diol

Abstract The polycaprolactone diol (PCL diol) was prepared by ring-opening polymerization method, with hydroquinone bis(2-hydroxyethyl) ether as the reactive initiator and ε-caprolactone as the monomer. The polyurethane acrylate (PUA) was prepared with the self-made PCL diol. Then, PUA was used to prepare the ultraviolet curable coatings. The structure and molecular weight of PCL diol was characterized by Fourier transform infrared spectroscopy, gel-permeation chromatography, and hydroxyl value titration. The performance of the cured coating film was characterized by thermogravimetric analysis and scanning electron microscope. The flexibility and hardness of the cured coating film were tested. The results showed that the narrow molecular weight PCL diol was successfully synthesized. The UV curing coating film had the optimal performance with a hardness of 3H, flexibility of 1.5 mm, abrasion resistance of 0.028 g−1, and adhesion of grade 1, all coating films showed good thermal properties.

A modified TEGDMA-based resin infiltrant using polyurethane acrylate oligomer and remineralising nano-fillers with improved physical properties and remineralisation potential

ObjectivesThis study aimed to modify an experimental triethylene glycol dimethacrylate (TEGDMA) based resin infiltrant using PUA oligomer and two remineralising fillers, including fluorohydroxyapatite (FHA) and fluoride-doped bioactive glass (FD-BG), to improve the mechanical and physical properties and induce remineralising potential. Materials and methodsThe polyurethane acrylate oligomer (PUA) was synthesised and characterised. Experimental resin infiltrant was prepared by mixing 10% of synthesised PUA with 88% TEGDMA. Water contact angle, penetration coefficient, and penetration depth were then measured. The FHA and FD-BG fillers were synthesised and characterised. To prepare nano-filled resin infiltrant, 5% of each powder was mixed with the prepared resin infiltrant. The prepared resin infiltrants were characterised to evaluate their degree of conversion, mechanical properties, water sorption, and solubility. The ion release of filled resin was also assessed. The non-infiltrated and infiltrated enamel specimens underwent fourteen days of pH-cycling, and a surface microhardness was done to assess the resistance to demineralisation. ResultsThe results showed that the addition of PUA to TEGDMA increased the mechanical properties and decreased water sorption and solubility. The addition of synthesised FD-BG fillers to resin infiltrant significantly improved the resistance to demineralisation of enamel samples compared with other groups (p ≤ 0.001). The FHA fillers also improved the resistance to demineralisation; however, the produced changes were not statistically meaningful (p > 0.05). ConclusionsBased on the results, the PUA+TEGDMA+ FD-BG/FHA composite can be used as an alternative material for pure TEGDMA in enamel infiltration approaches owing to its better mechanical properties, lower water sorption and solubility, and also remineralisation potential. Clinical SignificanceA resin infiltrant with remineralisation potential, lower water sorption and solubility and higher mechanical properties may enhance the management of early caries lesions.

One-pot and solvent-free synthesis of castor oil-based polyurethane acrylate oligomers for UV-curable coatings applications

Due to the complex chemical modification, harsh synthesis conditions and imperative post-treatment, the industrial products of vegetable oil-based polymers are very rare. In this study, castor oil-based polyurethane acrylic resin (COPUA) was synthesizled by one-pot method from castor oil (CO), isophorone diisocyanate (IPDI), hydroxyethyl acrylate (HEA) and isobbornyl acrylate (IBOA). 1H NMR and FT-IR measurements were employed to verify the successful preparation of COPUA. Various UV curable films were prepared by mixing non-treated COPUA, photoinitiator (PI-1173), mono-functional active diluent hydroxyethyl methacrylate (HEMA) or bifunctional active diluent tripropylene glycol diacrylate (TPGDA). The mechanical performances of the cured films were studied. Besides, DMA and TGA analyses were used to determine the dynamic thermodynamic performances and the thermal stability of the cured films. As a result, the pure COPUA cured film exhibited excellent thermal stability, storage modulus (421 MPa at 25 °C), tensile strength (9.87 MPa) and high glass transition temperature (60.3 °C). The cross-linking density of films improved with increasing the content of active diluent, resulting in excellent overall performances. In addition, all films possessed excellent hardness, adhesion, solvent resistance and flexibility. In this study, it provides a green and environmentally friendly strategy for the synthesis of vegetable oil-based polymers, reducing our chemical dependence on petrochemical energy.

Tertiaryamine linked and polysiloxane modified polyurethane acrylate oligomer and its effects of migration/co-initiation on photo-curable inkjet printing

To resolve the issue of handle-softness inadequacy in current polyurethane acrylate (PUA) oligomers for photo-curable inkjet printing on flexible substrates, and to improve the ability of anti-oxygen inhibition and photo-initiation efficiency of the tertiaryamine macromolecular co-initiator, the hydroxyl-terminated polydimethylsiloxane co-polymerized with tertiaryamine modified polyurethane acrylate (SiPUA) oligomer was designed and synthesized by using a sequential polymerization process. The structure of the SiPUA oligomer was confirmed by titration test and FTIR analysis, and the properties of the oligomers and the resultant photo-cured films were characterized by a range of analytical and measurement techniques. During the photo-curing process, the polysiloxane chain segment moved to the surface of the photo-cured SiPUA-HEA film due to the similar "surfactant critical micelle effect", forming an interconnected microphase structure of 50-70 μm thickness enriched with siloxane. The tertiaryamine group linked with polysiloxane segment was also enriched in the surface accordingly due to the migration of polysiloxane, thus improving the ability of anti-oxygen inhibition and photo-initiation efficiency. Benefiting from the both polysiloxane and tertiaryamine enriched surface and the retained PUA-HEA framework bulk in the cured film, a soft, flexible and strong photo-cured film with water-resistance and high photo-initiating efficiency was obtained.

Facile synthesis and characterization of renewable dimer acid-based urethane acrylate oligomer and its utilization in UV-curable coatings

A UV-curable polyurethane acrylate (PUA) oligomer was prepared from dimer acid (DA) based polyester polyol (DAPEP) with a monofunctional acrylate precursor which was developed upon isophorone diisocyanate (IPDI) reacted with 2-hydroxyethyl methacrylate (HEMA). The structural elucidation of synthesized dimer acid based PUA (DAPUA) oligomer was verified through Fourier-transform infrared spectroscopy (FT-IR) and Proton nuclear magnetic resonance (1H NMR). A series of UV cured coatings were prepared by adding trimethylolpropane triacrylate (TMPTA) and 1,6-hexanediol diacrylate (HDDA) reactive diluents in varying percentages (10−30 wt%) to PUA oligomer. The bio-coatings exhibited exceptional results, including the highest thermal degradation temperature of 382–422 °C, glass transition temperature (Tg) of 56.38–66.27 °C, the tensile strength of 17.3–30.6 MPa, volume shrinkage of 6.19–9.13 %, and surface roughness of 4.89–28.21 nm. Compared to vegetable oil based UV-curable coatings, long chain dimer acid based PUA oligomer coatings exhibited excellent flexibility, impact, hydrophobicity, and resistance to volume shrinkage.

High-performance UV-curable Polyurethane Acrylate Resins Derived from Low-iodine Woody Plant Oils

In this study, we report the preparation of high-performance UV-curable polyurethane acrylate (PUA) materials from two low-iodine woody plant oils, rubber seed oil (RSO) and wilsoniana seed oil (WSO). First, high-functionality oil-based PUA oligomers were synthesized via isocyanate polyurethane reaction between hydroxylated woody plant oils, isophorone diisocyanate, and pentaerythritol triacrylate, in which the hydroxylated oils were obtained by ring opening of epoxidized oils with ethylene glycol. Chemical structures of the obtained RSO-based and WSO-based PUA oligomers (RSO-PUA and WSO-PUA) were confirmed by FT-IR and 1H NMR. The 1H NMR results indicated that the RSO-PUA and WSO-PUA oligomers reached a C = C functionality up to 20.9 and 15.2 per triglyceride, respectively. The obtained oil-based PUA oligomers were then blended with hydroxyethyl methacrylate (HEMA) to form UV-curable resins and ultimate properties of the resultant materials were investigated. The oil-based PUA materials showed excellent performance after UV-curing. For example, the RSO-based PUA film containing 30% of HEMA demonstrated the tensile strength of 22.2 MPa, tensile modulus 1.78 GPa, glass transition temperature of 118.1 °C, adhesion of 2 grade, pencil hardness of 2H, and flexibility of 2 mm. In general, the developed woody plant oil-based PUA resins are very promising to be applied as green UV-curable coatings.

Preparation and properties of photo-curable coatings based on synthesis of self-photocuring polyurethane acrylate oligomer for pre-coated metal

In this study, we synthesized a self-photocurable intermediate by Michael addition reaction and synthesized a polyurethane acrylate oligomer. Photo-curable coatings were prepared by mixing the synthesized oligomer and HDDA/TMPEOTA ratio with a reactive diluent. The films were coated onto glass plates and base treatment metal plates using bar coaters with thicknesses of 120 μm and 30 μm, respectively. The mechanical properties increased with increasing crosslink density. The pencil hardness test was the best when the TMPEOTA content was 6 or 8 wt%, and the adhesion and banding test showed excellent physical properties when the TMPEOTA content was less than 10 wt%. MEK rubbing was all excellent.

Design and Preparation of Tertiary Amine Modified Polyurethane Acrylate Oligomer with Co‐Initiation/Polymerization Bifunctions for Photo‐Curable Inkjet Printing of Textiles

AbstractIn order to resolve the conflict issues existing in currently available polyurethane acrylate (PUA) oligomers for photo‐curable inkjet printing of textile, and to avoid the safety problems caused by the immigration of small molecule amine co‐initiator, a series of tertiary amine modified PUA oligomers are delicately designed and synthesized. The chemical structures of the synthesized PUA oligomers are confirmed by FTIR and 1H‐NMR analyses. The optimized PUA oligomer/hydroxyethyl acrylate based polymerization system show a low viscosity, high storage stability and good compatibility with various functional segments. Furthermore, the modified PUA oligomer acts as both the photopolymerization constituent and the macromolecular co‐initiator assisting to achieve high photopolymerization rate and conversion rate, and avoiding the disadvantages caused by the migration of small amine co‐initiators. Benefitting from the semi‐IPN formed by this polymerization system with suitable crosslinking density and phase separation degree, a soft, strong and flexible cured film is obtained. The high photo‐reactivity with low viscosity of the polymerization system and the good flexibility with high strength of the resultant photo‐cured film ensures the applications of the modified PUA oligomer, and the printed fabrics achieve 4 grade of colorfastness with improved handle properties, as well as brilliant color and fine patterns.

Preparation and properties of ultraviolet/thermal dual-curable polyurethane acrylate

Ultraviolet (UV)/thermal dual-curable polyurethane acrylate (PUA) mixtures were prepared using a PUA oligomer, tripropylene glycol diacrylate (TPGDA), benzoyl peroxide (BPO), 2,4,6-trimethylbenzoyldiphenyl phosphine oxide (TPO), and cobalt isooctanoate. For purposes of comparison, a UV-curable PUA mixture was prepared by mixing the PUA oligomer, TPGDA, and TPO. When placed under a UV lamp (400 W, 50 mW/cm2), the surface drying time of each curable mixture was approximately 2 s. The content of volatiles during UV curing (the intensity of the lamp was 100 mW/cm2) was less than 0.3 wt%, and the content of potential volatiles (the test condition was heating at 110 °C for 1 h after UV curing) was below 1.0 wt%. Compared with the UV-cured sample, the UV/thermal dual-cured sample containing cobalt isooctanoate had more favorable properties, that is: (1) better acid and alkali resistance; and (2) better thermal stability and higher gel content. The temperature at 5 wt% weight loss (T5wt.%) and the gel fraction of the UV-cured sample (the curing condition was 1 min of UV irradiation) were 269.4 °C and 94.6%, respectively. The T5wt.% and the gel fraction of the UV/thermal dual-cured sample (cured at 100 °C for 10 min after 1 min of UV irradiation) were 318.2 °C and 99.8%, respectively. BPO and cobalt isooctanoate had little effect on the surface drying rate of the curable mixtures, and the performance of the cured samples was improved by thermal treatment following irradiation with UV. Considering the dyeing effect of BPO, this system provides a more practical approach to the complete curing of colored UV-curable resins.

3D Printing Mechanically Robust and Transparent Polyurethane Elastomers for Stretchable Electronic Sensors.

Advanced stretchable electronic sensors with a complex structure place higher requirements on the mechanical properties and manufacturing process of the stretchable substrate materials. Herein, three kinds of polyurethane acrylate oligomers were synthesized successfully and mixed with a commercial acrylate monomer (isobornyl acrylate) to prepare photocurable resins with a low viscosity for a digital light processing three-dimensional (3D) printer without custom equipment. Results showed that the resin containing poly(tetrahydrofuran) units (PPTMGA-40) exhibited optimal mechanical properties and shape recoverability. The tensile strength and elongation at break of PPTMGA-40 were 15.7 MPa and 414.3%, respectively. The unprecedented fatigue resistance of PPTMGA-40 allowed it to withstand 100 compression cycles at 80% strain without fracture. The transmittance of PPTMGA-40 reached 89.4% at 550 nm, showing high transparency. An ionic hydrogel was coated on the surface of 3D-printed structures to fabricate stretchable sensors, and their conductivity, transparency, and mechanical performance were characterized. A robust piezoresistive strain sensor with a high strength (∼6 MPa) and a wearable finger guard sensor were fabricated, demonstrating that this hydrogel-elastomer system can meet the requirements of applications for advanced stretchable electronic sensors and expand the usage scope.

Assessment of vinyl acetate polyurethane-based graft terpolymers for emulsion coatings: Synthesis and characterization

Hybrid oligomers composed of polyurethane methacrylate (PUMA) and polyurethane acrylate (PUA) were synthesized by poly addition polymerization of polypropylene glycol (PPG 1000), 2,4- and 2,6-toluen diisocyanate (TDI 80/20) and 2-hydroxyethyl methacrylate or 2-hydroxyethyl acrylate. Isopropanol was served as the isocyanate blocking agent. The grafting of either PUMA or PUA oligomers to the vinyl acetate monomer was implemented for the first time for improving the properties of the produced PU-co-VAc or (PUPMA or PUPA) terpolymers as new binders for emulsion coating formulations. The synthesized terpolymers were characterized with Fourier-transform infrared spectroscopy (FTIR), proton nuclear magnetic resonance (1H NMR), scanning electron microscope (SEM), gel permeation chromatography (GPC), minimum film forming temperature (MFFT), thermal gravimetric analysis (TGA), Zeta potential and mechanical properties. It has been shown that properties of the terpolymers and their corresponding films were greatly influenced by the grafting of PUMA and PUA at a low concentration level (5 wt%). Cured films of PU based vinyl acetate (PUPMA or PUPA) exhibited higher thermal stability and less weight loss compared to the vinyl acetate copolymer (PVAC). The synthesized PUPMA and PUPA terpolymers revealed enhanced efficiency as binders for emulsion paints in comparison to the PVAC copolymer.

Synthesis and Properties of UV-Curable Polyfunctional Polyurethane Acrylate Resins from Cardanol.

A novel UV-curable polyurethane acrylate (PUA) oligomer was synthesized by modifying cardanol with a polyfunctional acrylate precursor obtained through reacting pentaerythritol triacrylate with isophoronediisocyanate. Chemical structures of the obtained cardanol-based PUA (C-PUA) oligomer were confirmed by Fourier transform infrared and 1H NMR. Subsequently, viscosity and gel content of the C-PUA resins containing different quantities of hydroxymethyl methacrylate (HEMA) were characterized. The C-PUA oligomer possessed a viscosity of 8360 mPa s, which reduced to 115 mPa s when 40% of the HEMA diluent was added. Furthermore, thermal, mechanical, coating, and swelling properties of the resulting UV-cured C-PUA/HEMA materials were investigated. The ultimate biomaterials showed excellent performance, including a glass transition temperature (Tg) of 74–123 °C, maximum thermal degradation temperature of 437–441 °C, tensile strength of 12.4–32.0 MPa, tensile modulus of 107.2–782.7 MPa, and coating adhesion of 1–2. In conclusion, the developed C-PUA resins show great potential to be applied in UV-curable materials like coatings.

Direct Hot-Injection Synthesis of Lead Halide Perovskite Nanocubes in Acrylic Monomers for Ultrastable and Bright Nanocrystal-Polymer Composite Films.

In recent years, lead halide perovskite nanocrystals (NCs) have attracted significant attention in both fundamental research and commercial applications because of their excellent optical and optoelectrical properties. However, the protective ligands on the surface of the perovskite NCs could be easily removed after the tedious process of centrifugation, separation, and dispersion, which greatly hampers their stability against light, heat, moisture, and oxygen and limits their practical applications. Here, we report a new post-processing free strategy (i.e., without centrifugation, separation, and dispersion process) of using an ultraviolet (UV)-polymerizable acrylic monomer of lauryl methacrylate as the solvent to synthesize CsPbBr3 NCs, and then adding polyester polyurethane acrylate oligomer, monomer (IBOA), and initiator for direct UV polymerization to fabricate NC-polymer composite films. These films exhibited an improved photoluminescence quantum yield (85-90%) than classic NC films (40-50%), which were processed using octadecene (ODE) as the solvent for NC synthesis and postprocessed for UV polymerization. Significantly, the as-fabricated films by post-processing free strategy exhibited excellent photostability against strong Xe lamp illumination; while the other films using classic methods were quickly photodegraded. Meanwhile, these NC-polymer composite films showed good stability against moisture and heating when aging in water at 50 °C for over 200 h. These films, along with K2SiF6:Mn4+ (KSF) phosphor emitters, were used as downconverters for blue light-emitting diodes in liquid-crystal displays with a wide color gamut of 115% in the International Commission on Illumination (CIE) 1931 color space. This work provides a facile and effective strategy for the preparation of ultrastable and bright color-conversion NC films for the development of the next-generation wide color gamut displays.

Preparation, characterization, and properties of novel ultraviolet-curable and flame-retardant polyurethane acrylate

A series of flame-retardant polyurethane acrylate oligomer (FRPUA)–nhexa- phenoxy-cyclotriphosphazene (HPCP) (n = 0, 10, 15, and 20, where n is the amount of HPCP added to a 100 g mixture of FRPUA and other additives) ultraviolet (UV)-cured samples have been prepared. FRPUA was synthesized by the reaction of poly(glycidyl methacrylate) (an unsaturated polyether), a derivative of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) (2DOPO–4,4′- dihydroxy-benzophenone (DHBP)), and isophorone diisocyanate. As a control sample, the polyurethane acrylate (PUA) oligomer and cured PUA sample were also prepared. Surface drying of the PUA and FRPUA–nHPCP curable mixtures required a few seconds under UV irradiation (400 W lamp). The effects of 2DOPO–DHBP and HPCP on the flame retardancy and thermal stability of the PUA system were also investigated. For the FRPUA–nHPCP series, as n increases from 0 to 20, the limiting oxygen index (LOI) increases from 21.1% to 23.3% and the total heat release (THR) slowly decreases from 32.4 to 26.4 kJ/g, while the PUA cured sample possesses the LOI and THR values of 19.0% and 29.2 kJ/g, respectively. Besides, the PUA system can achieve better flame retardant properties when using both 2DOPO-DHBP and HPCP. Thermogravimetric analysis indicates that the amount of char residue of the FRPUA–nHPCP (n = 0, 10, 15, and 20) cured samples ranges from 15.1 to 21.9 wt.%, which are much are higher than 10.5 wt.% for the PUA cured sample. Improving the flame retardancy of the PUA system will expand its applications, such as for paper manufacturing and architectural coatings, while simultaneously retaining the feature of fast surface drying.