Preparation and properties of polymer/LDH nanocomposite used for UV curing coatings

The thermal and mechanical properties of UV curing coatings consisted of urethane acrylates as an oligomer and a diacrylate monomer were reinforced by using layered double hydroxide (LDH). The LDH was organically modified by an ion-exchange process, in which the nitrate anions were replaced by long alkyl sulfate anions. With organic modification, the d-spacing of inorganic LDH layers was greatly enlarged to 2.75 from 0.78 nm, leading the LDH to be organophilic. During in situ photopolymerization process, the d-spacing of LDH layers was further enlarged to 4.29 nm, indicating the intercalation of polymer chains. For comparison, polymer/LDH nanocomposite filled with un-modified LDH was also prepared, and showed less enhancement in thermal and mechanical properties.     

Preparation of waterborne hyperbranched polyurethane acrylate/LDH nanocomposite

A series of novel waterborne hyperbranched polyurethane acrylate (WHPUA)/layered double hydroxide (LDH) nanocomposites based on hyperbranched aliphatic polyester Boltorn H20 (H20) and MgAl-LDH were successfully synthesized by in situ polymerization approach. The MgAl-LDH was firstly modified by sodium dodecyl sulfate (SDS) through the coprecipitation method, and then grafted by isophorone diisocyanate (IPDI), forming a complex with NCO groups at the surface and interlayer of LDH (LDH-DS-NCO). The residual hydroxyl groups after modification with succinic anhydride were crosslinked by the semi-adduct of IPDI reacted with HEA, and LDH-DS-NCO, followed by a neutralization reaction with triethylamine. The resulting water dispersible hyperbranched polyurethane acrylate WHPUA/LDH hybrid oligomer was then exposed to a medium pressure mercury lamp, forming a partially exfoliated WHPUA/LDH nanocomposite in the presence of a fragmental photoinitiator. The chemical structure, crystal configuration, morphology of WHPUA/LDH nanocomposite were characterized by Fourier transform infrared spectroscopy, X-ray diffraction, thermogravimetric analysis, and high resolution transmission electron microscopy. The experimental results indicated that both the intercalated and exfoliated structures were formed in the UV cured polymer/LDH nanocomposite. The TGA results showed that the thermal stability was improved. Moreover, the pencil hardness was greatly increased, and the flexibility remained at an acceptable level for the UV cured polymer/LDH nanocomposites.     

UV固化水性聚氨酯/层状双氢氧化物纳米复合乳液的研究

以聚碳酸酯二元醇为软段、异佛尔酮二异氰酸酯为硬段合成了UV固化非离子型水性聚氨酯.同时采用共沉淀法制备了十二烷基硫酸钠插层的层状双氢氧化物(LDH-DS).在乳化水性聚氨酯的同时滴加LDH-DS水分散液,制备绿色环保的水性聚氨酯/层状双氢氧化物复合乳液,随后在UV辐照下制备纳米复合乳液涂膜.通过X-射线衍射和傅里叶红外分析证明了层状双氢氧化物的插层改性结构,并发现随着LDH-DS填充量的增大,涂膜的硬度及拉伸强度均有所提高.     

Morphology and thermal stabilization mechanism of LLDPE/MMT and LLDPE/LDH nanocomposites

The morphology and thermal stabilization mechanism of polymeric nanocomposites prepared by solution intercalation of linear low density polyethylene (LLDPE) with montmorillonite (MMT), MgAl layered double hydroxide (LDH), and ZnAl LDH have been studied by X-ray diffraction (XRD), transmission electron microscopy (TEM), dynamic Fourier transform infrared (FTIR) spectroscopy, and thermogravimetric analysis (TGA). Both LLDPE/MMT and LLDPE/MgAl LDH nanocomposites exhibit mixed intercalated-exfoliated structures, whereas the LLDPE/ZnAl LDH nanocomposites exhibit completely exfoliated structures because the ZnAl LDH layers can be easily broken during the refluxing process. All nanocomposites show significantly enhanced thermal stability compared with virgin LLDPE due to the increases of the effective activation energy (E_α) during degradation process. However, LDHs nanocomposites show much higher thermal degradation temperatures than MMT nanocomposites with the same filler content because they have much higher E_α than MMT nanocomposites at the early degradation stage. The data of real time FTIR spectroscopy and morphological evolution reveal a catalytic dehydrogenation effect presents in MMT nanocomposites, which may decrease the E_α of degradation and thermal stability of MMT nanocomposites.     

UV curing and matting of acrylate coatings reinforced by nano-silica and micro-corundum particles

For UV curable coatings, the effect of the type of photoinitiator and of the photoinitiator content on surface properties has been studied. Increasing photoinitiator concentrations yielded higher acrylate conversion but a lowering of surface hardness. Thus, curing under oxygen-free conditions with 2 wt.% photoinitiator should be applied rather than 6 wt.% photoinitiator for irradiation in air. Compared to nanocomposite materials, UV-cured polyacrylate coatings reinforced by silica nanoparticles and corundum microparticles exhibit markedly improved scratch and abrasion resistance. By using various grades of corundum, a synergetic effect between nano- and microparticles has been observed. These nano/micro-hybrid composite materials are recommended as clear coat for parquet and flooring applications.     

Preparation and properties of layered double hydroxide/poly(ethylene terephthalate) nanocomposites by direct melt compounding

Thermal, rheological and mechanical properties of layered double hydroxide (LDHs)/PET nanocomposites were investigated. To enhance the compatibility between PET matrix and LDHs, organic modification of parent LDH having carbonate anion was carried out using various anionic surfactants such as dodecylsulfate (DS), dodecylbenzenesulfonate (DBS), and octylsulfate(OS) by rehydration process. Then, PET nanocomposites with LDH content of 0, 1.0, and 2.0 wt% were prepared by direct melt-compounding. The dispersion morphologies were observed by transmission electron microscopy and X-ray diffraction, indicating that LDH-DS were exfoliated in PET matrix. From the rheology study, there are some network structures owing to filler-filler and/or filler-matrix interactions in nanocomposite systems. Consequently, DS intercalated LDH provided good compatibility with PET molecules, resulting in exfoliated LDH-DS/PET nanocomposites having enhanced thermal and mechanical properties as compared to other nanocomposites as well as homo PET.     

Photopolymerization behavior and properties of highly branched polyester acrylate containing thioether linkage used for UV curing coatings

The highly branched polyester acrylate containing thioether linkage (HBAT) was synthesized using an “oligomeric A₂ + B₃” approach. The dithiol, 1,6-hexamethylene bis(3-mercaptopropionate) (HMBM), was prepared through the esterification between 1,6-hexanediol and 3-mercaptopropionic acid, and then underwent an amine-catalyzed thiol-Michael addition to the acrylic double bond of 1,6-hexamethylene diacrylate to obtain an oligomeric dithiol (oligomeric A₂), then further with trimethylolpropane triacrylate as a B₃ monomer. The molecular structure was characterized with FT-IR and ¹H NMR spectroscopy. A broader molecular weight distribution from 1.74 to 2.75 was obtained for different oligomeric dithiol chains by GPC measurements. The photopolymerization kinetics study by photo-DSC analysis showed that the HBAT greatly reduced the oxygen inhibition in radical photopolymerization of acrylates in air. The maximum polymerization rate decreased along with the addition of HBAT into the UV curable resin (EB605) containing bisphenol A epoxy diacrylate and tripropylene glycol diacrylate due to the reduced double bond density and increased viscosity, whereas the final unsaturation conversion in cured film increased because of the longer spacer chain in HBAT compared to that in EB605 and the reduced crosslinking density by HBAT addition. The dynamic mechanical thermal analysis results showed that both the elastic modulus in the rubbery plateau and glass transition temperature of cured film decreased along with the incorporation of HBAT into EB605. The water swelling test and thermogravimetric analysis indicated that the thioether linkage in HBAT can greatly improve the water absorption resistance and oxidative stability of cured film.     

Preparation and properties of LDHs/polyimide nanocomposites

Layered double hydroxides/polyimide (LDHs/PI) nanocomposites were prepared from solution of polyamic acid (polyimide precursor) and LDH-amino benzoate using N,N-dimethylacetamide as a solvent. LDH-amino benzoate (LDH-AB) was obtained by coprecipitation method. The amino benzoate, grafted on the surface of the Mg/Al nanolayers, as a connector improved the compatibility between the inorganic Mg/Al nanolayers and the organic polyimide molecules. The dispersion behavior of Mg/Al nanolayers was investigated by transmission electron microscopy and X-ray diffraction, indicating that the Mg/Al nanolayers were exfoliated in PI matrix to form LDH-AB/PI nanocomposites. The maximum tensile strength and elongation of the LDH-AB/PI nanocomposites were found with the LDH-AB content of 5 and 4 wt%, respectively. The initial tensile modulus of these nanocomposites was increased with the LDH-AB content. These nanocomposites exhibited higher storage and loss moduli compared to those of pure PI. T_g of these nanocomposites increased with the LDH-AB content. Coefficients of thermal expansion (CTE, below and above T_g) of these nanocomposites deceased with the LDH-AB content. The thermal properties of these nanocomposites were enhanced by the incorporation of Mg/Al nanolayers in PI matrix.     

Preparation and film properties of tri(3,4-epoxycyclohexylmethyl) phosphate based cationically UV curing coatings

A facile synthesis of phosphorus-containing trifunctional cycloaliphatic epoxide resin, tri(3,4-epoxycyclohexylmethyl) phosphate (TECP), used for cationically UV curing coatings as a reactive-type flame retardant, was proposed. The molecular structure was confirmed by FTIR, ¹H NMR and ³¹P NMR spectroscopic analysis. A series of flame retardant formulations by incorporating into a commercial difunctional cycloaliphatic epoxide resin, CYRACURE™ UVR-6110, were prepared, and exposed to a medium pressure lamp to form the cured films under the presence of diaryliodonium hexafluorophosphate salt as a cationic photoinitiator. Their flame retardancy examined by the limiting oxygen index showed the improvement up to 27 for 50 wt% TECP addition compared with 21 for pure UVR-6110. The T_s and T_g decreased from 86 °C and 131 °C to 55 °C and 91 °C, respectively, by using dynamic mechanical thermal analysis, whereas the tensile strength showed a slight increase (11%) with 50 wt% TECP addition. The thermogravimetric analysis (TGA) and real-time Fourier transform infrared spectroscopy (RT-FTIR) measurement demonstrated the condensed-phase flame retardant mechanism.     

Design,synthesis, and nanoengineered modification of spherical graphene surface by layered double hydroxide (LDH) for removal of As(III) from aqueous solutions

In this study, new nano spherical graphene modified with LDH (Layered Double Hydroxide) was prepared and used to remove As(III) ion from aqueous solutions. At first, graphene oxide was synthesized from graphite using a well-known Hammer method. The obtained graphene oxide solution was sprayed in octanol solution under different temperatures and sprayed speed as influenced variables. The structure and physical characterization of synthesized spherical graphene oxide were determined by various techniques, including FT-IR, N₂ adsorption–desorption, SEM, TEM, and EDX. In the next step, the hydrothermal method was applied to deposition LDH on the spherical graphene oxide. The synthesized spherical graphene modified by LDH was used to remove As(III) as a toxic heavy metal ion. The effect of influenced variables including pH, contact time, amount of sorbent, and type eluent studied and the optimum values were as 8, 30, 50, and HCl (0.5 mol·L^-1), respectively. After optimization, the studied sorbent was shown a high adsorption capacity (149.3 mg·g^-1). The adsorption mechanism and kinetic models exhibited good agreement with the Langmuir isotherm and pseudo-second-order trends, respectively. Besides, the synthesized product was tested for seven times without significant loss in its sorption efficiency.     

UV curing and matting of acrylate nanocomposite coatings by 172 nm excimer irradiation

For UV-curable acrylate coatings reinforced by silica nanoparticles, the effect of 172 nm excimer irradiation on the surface roughness has been studied. A dual UV lamp set-up consisting of a 172 nm excimer lamp and a mercury arc lamp allowed obtaining gloss levels down to 0.5 units (at 60°) depending on the acrylate formulation and curing conditions. Moreover, UV matt-finished sample showed enhanced surface hardness and increased chemical resistance. It is assumed that 172 nm excimer irradiation resulted in a higher network density via additional cross-linking reactions.To study the depth profile of acrylate conversion for coatings cured by the combination of a 172 nm excimer lamp (accountable for surface curing) and a mercury arc lamp (responsible for through curing), FTIR microscopy as well as (Ge)ATR-FTIR having an IR penetration depth of less than 0.5 μm have been applied. Providing the presence of a photoinitiator as well as the absence of oxygen inhibition, similar degrees of double bond conversion of about 90% were observed on the entire area of the cross-section of the coating, i.e. the wavelength of UV irradiation was found to have no significant impact on acrylate conversion.     

Intercalation of 2,4-dihydroxybenzophenone-5-sulfonate anion into Zn/Al layered double hydroxides for UV absorption properties

Zn/Al-layered double hydroxides (LDHs) containing the organic anion of 2,4-dihydroxybenzophenone-5-sulfonate (DHBS) have been synthesized by co-precipitation method. Surface, structural, thermal and absorption properties of the ZnAl-DHBS-LDHs nanohybrids were characterized by BET analysis, scanning electron microscope, X-ray diffraction, Fourier transform infrared spectroscopy, thermogravimetry and differential thermal analysis and UV–visible spectroscopy. The results revealed that organic UV absorbent-DHBS has been intercalated into the interlayer spaces of ZnAl-LDHs and the intercalation of DHBS in LDHs interlayer galleries resulted to higher thermal stability and better UV absorption ability; these show that the hybrid ZnAl-DHBS-LDHs phase has potential applications as a UV absorber.     

The effect of graphene oxide on UV curing kinetics and properties of SU8 nanocomposites

In the present study SU8 nanocomposites were prepared by incorporating graphene oxide (GO ), and its effect on the UV curing kinetics, morphology, electrical, hardness and thermal properties of the nanocomposites were investigated at different loading levels of GO (0.1 ? 3 wt%). Studying the reaction kinetics of the UV curing process by means of real‐time infrared spectroscopy showed that the polymerization rate and the final conversion of epoxy groups was related to the loading level of GO in the nanocomposites. An autocatalytic kinetics model of the curing reaction confirmed the effect of GO nanoparticles on the curing rate constant (k ), the order of the initiation reaction (m ) and the ultimate conversion of the UV ‐cured nanocomposites. Appropriate experimental observations indicated that dispersion of GO within the resin plays a critical role on the cure kinetics and final conversion. The results of the kinetics modeling and morphological observations showed that the curing rate constant of the nanocomposites is highly dependent on the GO content and its dispersion state, indicating that GO prevents epoxy resin crosslinking by photoinitator deactivation. Moreover, oxygen functionalities, such as hydroxyl and carboxyl groups, on the surface of GO facilitate interfacial interactions between epoxy groups from the matrix and GO . Electrical conductivity measurements demonstrated that the UV ‐induced photo‐cured GO filled resins are conductive SU8 nanocomposites. It was observed that the thermal stability of the nanocomposites is enhanced due to the dispersion of GO in the matrix. Moreover, the microhardness analysis showed that addition of GO to neat SU8 increases the mechanical hardness of the nanocomposite. © 2016 Society of Chemical Industry     

UV curing behavior of hyperbranched polyphosphate acrylate/di(hydroxylpropyl methacrylate) piperazine and properties of the cured film

The hyperbranched polyphosphate acrylate (HPPA) was blended with di(hydroxylpropyl methacrylate) piperazine (DHMP) to form a photopolymerizable flame retardant resin. The photopolymerization kinetics was investigated and showed that as DHMP added, the polymerization rate increased greatly while the final unsaturation conversion in the cured film decreased moderately. The thermal degradation and flame retardant behaviors of the cured HPPA/DHMP film showed that although the initial decomposition temperature raised, both the char residue and the limiting oxygen index largely decreased due to the reduction of phosphorus in the film with increasing the DHMP content. From the results by the dynamic mechanical thermal analysis DHMP has good miscibility with HPPA. The crosslink density and glass transition temperature of the cured film increased along with the content of DHMP in the blend. The mechanical property measurements indicated that the addition of DHMP led to a decrease in elongation-at-break and an increase in tensile strength.     

Synthesis of 5‐sulfosalicylic acid‐intercalated layered double hydroxide and its effects on wood flour/polypropylene composites during accelerated UV weathering

In this study, 5‐sulfosalicylic acid (SA) anions have been intercalated into Mg₃Al‐NO₃ layered double hydroxide (LDH) to synthesize SA‐intercalated Mg₃Al‐NO₃‐LDH (LDH‐SA) by ion‐exchange reaction. Then, the effects of LDH, SA, and LDH‐SA on the photostability of wood flour/polypropylene (WF/PP) composites during accelerated ultraviolet (UV) weathering were investigated. The surface color, surface gloss, and mechanical properties of the composites during weathering were tested, accompanied by characterizations using SEM, ATR‐FTIR, and TG. The results showed that (1) SA anions completely replaced the anions in LDH and the thermal stability of LDH‐SA was considerably enhanced; (2) composites with LDH or LDH‐SA exhibited less color change, fewer surface cracks, better thermal stability, and less losses of mechanical properties than the control group; (3) LDH‐SA showed a long‐term efficiency and alleviated the photo‐oxidation of WF/PP composites successfully; (4) LDH‐SA blocked UV light by physical shield effect of the layer sheets, as well as the chemical absorbability of the interlayer anions. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44597.     

Structure and conductive properties of poly(ethylene oxide)/layered double hydroxide nanocomposite polymer electrolytes

The oligo(ethylene oxide) modified layered double hydroxide (LDH) prepared by template method was added as a nanoscale nucleating agent into poly(ethylene oxide) (PEO) to form PEO/OLDH nanocomposite electrolytes. The effects of OLDH addition on morphology and conductivities of nanocomposite electrolytes were studied using wide-angle X-ray diffractometer, polarized optical microscopy, differential scanning calorimetry and ionic conductivity measurement. The results show that the exfoliated morphology of nanocomposites is formed due to the surface modification of LDH layers with PEO matrix compatible oligo(ethylene oxide)s. The nanoscale dispersed OLDH layers inhibit the crystal growth of PEO crystallites and result in a plenty amount of intercrystalline grain boundary within PEO/OLDH nanocomposites. The ionic conductivities of nanocomposite electrolytes are enhanced by three orders of magnitude compared to the pure PEO polymer electrolytes at ambient temperature. It can be attributed to the ease transport of Li⁺ along intercrystalline amorphous phase. This novel nanocomposite electrolytes system with high conductivities will be benefited to fabricate the thin-film type of Li-polymer secondary battery.     

Preparation and properties of in‐situ polymerized polyurethane/stearate intercalated layer double hydroxide nanocomposites

The present work deals with the effect of stearate intercalated layered double hydroxide (St‐LDH) loadings on the morphological, mechanical, thermal, adhesive and flame retardant properties of polyurethane (PU)/St‐LDH nanocomposites prepared by the in situ polymerization method. X‐ray diffraction and transmission electron microscopy studies confirmed that exfoliation takes place at 3 wt% loading followed by intercalation at higher filler loadings in the PU matrix. The exfoliated structure has been further verified by atomic force microscopy. The measurements of stress‐strain, thermogravimetric analysis, dynamic mechanical analysis, lap shear strength and peel strength analysis showed that the nanocomposites containing 3 wt% St‐LDH exhibit excellent improvement in tensile strength (ca 175%) and log storage modulus (ca 14%), while PU/St‐LDH (5 wt%) possesses optimum improvement in glass transition temperature (ca 6 °C), lap shear strength (200%) and peel strength (130%) over neat PU. In addition, the gradual improvements in limiting oxygen index value with St‐LDH loading indicated the higher effectiveness in providing better barrier properties as well as better flame retardant behavior. Copyright © 2012 Society of Chemical Industry     

Synthesis and properties of semi-crystalline hyperbranched poly(ester-amide) grafted with long alkyl chains used for UV-curable powder coatings

A series of semi-crystalline hyperbranched poly(ester-amide)s by modifying hydroxyl end groups of hyperbranched poly(ester-amide) (HP) with IPDI-C18 and IPDI-HEA in different ratios were synthesized and characterized by FTIR, NMR and GPC. Their crystallization behaviors and thermal properties determined by X-ray diffraction (XRD) and differential scanning calorimetry (DSC) showed that the high substitution degree of hydroxyl groups of hyperbranched poly(ester-amide) (HP) with IPDI-C18 resulted in higher degree of crystallization and thus glass transition temperature (T_g) up to 43 °C. The photopolymerization kinetics investigated by photo-DSC showed that the obtained semi-crystalline hyperbranched resins have high photopolymerization rate and final unsaturation conversion, which is very promising for UV-curable powder coating applications.     

Mechanical and optical properties of clay-based nanocomposites coatings for wood flooring

Clay-based nanocomposites coatings cured by UV light were prepared by four different types of dispersion equipment: a high-speed mixer, a ball mill, a bead mill and a three-roll mill. For each treatment, formulations were prepared at 1, 3 and 10 wt% of clay. A previous study had established the dispersion efficiency of each treatment and the effect of clay dispersion on UV curing. The present study relates to the effect of clay dispersion on mechanical and optical properties. The mechanical properties studied included abrasion resistance, direct and reverse impact resistance as well as Persoz hardness. Optical properties, such as haze, gloss, color and optical clarity were assessed. An analysis of variance (ANOVA) was conducted to evaluate the effect of clay loading and process type on mechanical and optical properties. A statistical analysis revealed that each property varied with the percentage of clay loading in every treatment. It was found that the quality of the clay dispersion strongly affected both mechanical and optical properties.     

Synthesis and properties of hyperbranched polyurethane acrylate used for UV curing coatings

The hyperbranched polyurethane acrylate (HPUA) was synthesized through the addition of hyperbranched polyurethane endcapped by hydroxyl groups (HPU-OH), with the semiadduct urethane monoacrylate (IPDI-HEA). The HPU-OH was prepared by the amidation reaction of diethanolamine with isophorone diisocyanate. The molecular structure of HPUA was characterized by FTIR and ¹H NMR analyses. The number average molecular weight and its polydispersity index were measured by GPC to be 7714 g mol⁻¹ and 1.24, respectively. The HPUA was blended with epoxy acrylate EB600 and difunctional monomer TPGDA in different ratios, and exposed to a UV lamp for photopolymerization in the presence of Runtecure 1104 as a photoinitiator at room temperature. The photopolymerization rate and final unsaturation conversion reached to the highest values with only 5 wt% HPUA addition, whereas decreased as further added. The tensile strength of UV-cured films was improved by adding less than 10 wt% HPUA without damaging the modulus, having the value of 62.56 MPa for EB₉₀HPUA₁₀ film. Besides, the elongation at break increased continuously with the addition of HPUA, reaching to 130% for EB₇₀HPUA₃₀ film. Moreover, the impact strength was greatly enhanced by the addition of HPUA, possessing nearly two times high for EB₇₀HPUA₃₀ film compared with pure EB600 film. However, the T_g decreased as HPUA was added from the DMTA measurements. According to the ratios of T_s/T_g the HPUA has good compatibility with EB600/TPGDA resin.