Effects of small molecular weight silicon‐containing acrylate on kinetics,morphologies, and properties of free‐radical/cationic hybrid UV‐cured coatings

A series of UV‐curable, silicon‐containing mixtures were prepared by adding different micro amounts of small molecular weight silicon‐containing acrylate KH570 to an interpenetrating polymer network system composed of cycloaliphatic polyurethane acrylate, trimethylolpropane triacrylate, cycloaliphatic epoxy resin, free‐radical photoinitiator Irgacure 754 and cationic photoinitiator Irgacure 250 with a weight ratio of 15 : 15 : 65 : 1 : 4. Hybrid coatings with different addition amounts of KH570 (0.2, 0.6, 1.0 wt %) were cured from the mixtures by UV‐initiated free‐radical/cationic dual curing technique. Final reactant conversions and photopolymerization rates of the hybrid UV‐cured coatings were improved with the increase of KH570 content, as evaluated by conversion profiles. The morphologies and microstructures were characterized by scanning electron micro‐scopic, atomic force micrographic, and fourier transform infrared spectrophotometer measurements. Thermal, mechanical, and surface properties of the hybrid UV‐cured coatings were investigated. The increase in KH570 content caused a decrease in mechanical properties besides the breaking elongation. Thermo‐gravimetric analysis revealed that the incorporation of silicon into cross‐linked network structure resulted in high thermal stability. The surface properties of hybrid UV‐cured coatings, such as hardness, contact angle, flexibility, and glossiness were also examined. It is found that transparent hybrid coating with the addition of 1.0 wt % KH570 exhibited a relatively higher contact angle as a direct result of a relatively higher hydrophobic surface. These researches showed that micro amounts of small molecular weight silicon‐containing acrylate could greatly influence the morphologies of liquid nitrogen quenching cross sections and properties of hybrid UV‐cured coatings and could be used to modify UV‐cured coatings for some superior properties. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40655.     

Preparation and characterization of hybrid thiol‐ene/epoxy UV–thermal dual‐cured systems

Hybrid thiol‐ene/epoxy coatings were prepared by combining thiol‐ene photo‐curable formulations with epoxy monomers, through a dual UV–thermal curing process. An increase in glass transition temperature and in storage modulus was observed for the hybrid thiol‐ene/epoxy coatings when compared with the pristine thiol‐ene UV‐cured system. Also, the bisphenol A moieties introduced into the hybrid networks during the dual‐curing process induced an increase in thermal stability of the cured materials. It has been demonstrated that the addition of epoxy monomer to the thiol‐ene photo‐curable system is a good strategy to follow in order to improve the final properties of thiol‐ene‐based coatings leading to a wide range of possible applications for the hybrid materials. Copyright © 2010 Society of Chemical Industry     

Kinetics of UV‐initiated RAFT crosslinking polymerization of dimethacrylates

The UV‐initiated RAFT polymerizations of a series of poly(ethylene glycol) dimethacrylates (PEGDMA) were investigated using differential scanning photocalorimetry (DPC) at room temperature. The rate of the RAFT system was much lower than that of a conventional free radical polymerization. A mild autoacceleration occurred as the addition reaction became diffusion controlled. The influence of the spacer length (CH₂CH₂O)_x between the vinyl moieties of the dimethacrylates on the polymerization kinetics was examined. The polymerization rate of PEGDMA decreased with an increased x value from 4 to 9, but it increased with a further increased x value from 9 to 14. Mechanical properties of the resulting polymers were also examined by dynamic mechanical analysis (DMA). It was concluded that the presence of the RAFT agent during polymerization of multifunctional monomers did not have an effect on the heterogeneity of the polymer network. In comparison with three different PEGDMAs, the PEGDMA with the longest spacer formed the most homogeneous networks with a lower crosslinking density. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

UV‐activated silicone oligomer cross‐linking through photoacid and photobase organocatalysts

Diphenyl iodonium hexafluorophosphate salt and N‐alkyl morpholino acetophenone were shown to be effective photocatalyst generators for the cross‐linking of α,ω‐silanol terminated silicone oligomers. These two photoacid and photobase‐induced polycondensation pathways provided an attractive and efficient alternative to toxic and expensive organometallic catalysts. The utility of this novel UV‐curing process was demonstrated with a combination of time‐resolved infrared spectroscopy to follow the fast reaction kinetics and solid‐state ²⁹Si nuclear magnetic resonance to investigate the polysiloxane network. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39875.     

Preparation and performance of waterborne UV‐curable polyurethane containing long fluorinated side chains

Novel waterborne UV‐curable polyurethane containing long fluorinated side chains (WUVFPU) was prepared and the fluorinated component was incorporated by two novel fluorinated macromolecular diols (FDO) with different chain length as chain extender. FDO was synthesized via free radical polymerization of hexafluorobutyl methacrylate (HFBMA) using 1‐thioglycerol (TG) as chain transfer agent. Extremely low dosage of FDO incorporated could change the surface property significantly. The influence of both the content and chain length of FDO on the surface energy, surface composition and morphology were investigated by contact angle measurement, XPS and AFM. Surface energy significantly decreased at extremely low concentration of FDO. The hydrophobicity was enhanced with increasing both the content and the chain length of FDO. XPS and AFM results revealed the enhancing hydrophobicity was attributed to the enrichment of F atoms and rougher surface morphology. Gel content, pencil hardness, adhesion, and optical transmittance tests were employed to investigate the coating properties of the UV‐cured films. The preparation and investigation of WUVFPU might provide better understanding of the influence of fluorinated chain length on the properties of polyurethane for theory. Moreover, it might provide a facile and effective route to prepare polyurethane materials with low surface energy for engineering and industry. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44506.     

Efficient Benzodioxole‐based unimolecular photoinitiators: From synthesis to photopolymerization under UV‐A and visible LED light irradiation

The narrow emission spectra of light emitting diodides (LED) as irradiation source has brought great challenge for the development of efficient photoinitiators sensitive to LED light. This paper described a series of novel unimolecular type II photoinitiators, containing thioxanthones as chromophores and benzodioxoles as coinitiators. The structures of the photoinitiators were characterized by ¹H NMR, ¹³C NMR and high‐resolution mass spectrometer. Study on the photophysical properties of the photoinitiators indicated that electron donors/acceptors as spacers between thioxanthone and benzodioxole affected both the UV–Vis absorption and the fluorescence emission. The long wavelength absorptions from 385 nm to 402 nm as well as low fluorescence quantum yields make the investigated benzodioxole derivatives quite attractive as efficient photoinitiators under UV‐A and visible LED light irradiation. With a proper molecular design, the unimolecular photoinitiator exhibited higher initiation efficiency than the thioxanthone derivatives from the literature. Possible initiation mechanism was also proposed based on the photolysis study. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43239.     

Epoxy acrylate UV/PU dual‐cured wood coatings

For improving the finishing performances of complicated three‐dimensional coated wood products (e.g., furniture) with some shadow zones in the absence of ultraviolet (UV) light, resulting in incomplete curing of UV coatings, the aim of this study was to investigate the characteristics and effects of curing process on the properties of epoxy acrylate UV/PU dual‐cured resin for wood coatings when compared with traditional UV and polyurethane (PU) coatings. The epoxy acrylate oligomer was synthesized for providing a double bond of acryloyl group and a secondary hydroxyl group. The UV/PU dual‐cured coating was formulated with epoxy acrylate resin/tripropylene glycol diacrylate (TPGDA) monomer by the weight ratio of 80/20, 3% dosage of benzil dimethyl ketal as a photoinitiator, and the NCO/OH mole ratio of 1.0. The aromatic polymeric diphenylmethane diisocyanate was used as a hardener. The films of the dual‐cured coating, obtained from UV‐cured or room temperature‐cured process, showed an excellent tensile strength, elongation at break, impact resistance, and lightfastness when compared with traditional UV and PU coatings; especially, the adhesion of UV/PU dual‐cured coating by UV‐cured process was better than that of traditional UV coating. It can therefore be concluded that the epoxy acrylate oligomer‐based dual‐cured coating could readily be used for complicated wood products finishing. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Water‐repellent finishing of cotton fabrics by ultraviolet curing

Cotton fabrics were water‐repellent‐finished by radical ultraviolet curing of silicone and urethane acrylates with different formulations. The fabrics were impregnated with undiluted resins and with toluene solutions or water emulsions. Moreover, cationic ultraviolet‐curable systems were also investigated, such as an epoxy‐functional polysiloxane and mixtures of an epoxy resin with hydroxyl‐containing silicone additives. The gel content and polymerization yield were considered for the ultraviolet‐curing process evaluation. Water‐resistance properties were determined in terms of the contact angle, wettability, moisture adsorption, and water vapor permeability measurements, whereas the morphology and surface composition of treated fabrics were examined with scanning electron microscopy and energy‐dispersive X‐ray analysis. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Synthesis of an oxetane‐functionalized hemispiroorthocarbonate used as a low‐shrinkage additive in the cationic ultraviolet curing of oxetane monomers

The synthesis of an hemispiroorthocarbonate functionalized with an oxetane group is reported. The obtained monomer was used as a slow shrinkable additive in the cationic ultraviolet curing of a commercially available dioxetane resin. We evidenced polymer network flexibilization by increasing the oxetane‐functionalized hemispiroorthocarbonate content in the photocurable formulation. It was demonstrated that spiroorthocarbonate acted as a shrinkage reduction additive and reached expansion on volume after polymerization in the presence of 50 wt % of the functionalized spiroorthocarbonate. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Preparation and characterization of UV‐cured hybrid coatings by triethoxysilane‐modified dimethacrylate based on bisphenol‐s epoxy

Novel hybrid oligomers based on a UV‐curable bisphenol‐S epoxy dimethacrylate (DBSMA) were synthetized. DBSMA was modified with various amount of (3‐isocyanatopropyl)triethoxysilane coupling agent. The modification degree of the hybrid oligomer was varied from 0 to70 wt %. The photopolymerization kinetics was monitored by a real‐time infrared spectroscopy. The conversion and rate of hybrid coatings increased with the increase in modification degree. UV‐curable, hard, and transparent organic–inorganic hybrid coatings were prepared. They were performed by the analyses of various properties such as surface and mechanical properties. Results from the mechanical measurements showed that the properties of hybrid coatings improved with the increase in modification degree. The thermal behavior of coatings was also investigated. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Crosslinking of poly(vinyl alcohol) and poly(vinyl acetate) using poly(maleic anhydride‐alt−2,4‐dimethyl‐1,3‐pentadiene) as polyfunctional crosslinker and decrosslinking by ozone degradation

Crosslinking and decrosslinking reactions of poly(vinyl alcohol) (PVA) and poly(vinyl acetate) (PVAc) using an alternating copolymer of maleic anhydride and 2,4‐dimethyl‐1,3‐pentadiene (PMAD) as the polyfunctional crosslinker and subsequent ozone degradation are reported. PVA and PVAc are heated at 200 °C for 0.5 to 3 h in the presence of 5 to 30 wt % of PMAD in the solid state to obtain the corresponding crosslinked polymers. The reactions of a hydroxy group of PVA and an acetate group of PVAc with an anhydride group of PMAD slowly proceed to give insoluble polymers with a loose crosslinking structure. Almost no change in the thermal decomposition temperatures and the IR spectra is observed during the crosslinking reactions. The crosslinked PVA produces hydrogels with a high swelling ratio of 500 to 1700%, which are readily degradable during a reaction with ozone in water at 0 °C. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44229.     

The effect of nonionic monomer HAM on properties of cationic surfactant‐free acrylic/alkyd hybrid emulsion

A series of cationic acrylic/alkyd resin (CPAAR) hybrid emulsions was successfully prepared through surfactant‐free emulsion polymerization, using methacryloxyethyltrimethyl ammonium chloride, methyl methacrylate, butyl acrylate and alkyd resin as reaction monomers. And nonionic N‐hydroxymethyl acrylamide (HAM) of different content was simultaneously incorporated into the CPAAR backbone. The structure of CPAAR copolymer was characterized by Fourier transform infared spectrometer, and then the effect of HAM content on properties of CPAAR emulsions was studied by particle size analyzer, transmission electron microscopy and rheometer. In addition, thermal properties, water absorption and contact angle of CPAAR latex films were also investigated. The results showed that the CPAAR emulsions prepared with 4.9 wt % HAM displayed smallest average particle size of 92.2 nm. As HAM content increased from 0 to 19.6 wt %, the initial viscosity of the emulsions increased from 22.48 to 53 mPa.s. At the same time, the emulsions transferred from Newtonian fluid to pseudoplastic fluid, and a transition from viscous liquid to elastic liquid was also detected. Meanwhile, the degradation temperature at 5% weight loss increased by 30.59°C. In addition, with increasing HAM content from 0 to 4.9 wt %, the water absorption and surface free energy of films increased by 4.42% and 5.02 mJ m^?2, respectively. However, the water absorption and surface free energy kept almost invariable with further increase in HAM content. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41406.     

In‐situ curing analysis of photoreplicated objective lenses using Raman and IR spectroscopy

Optical pick‐up lenses are used in optical storage devices such as CD, DVD, and Blu‐Ray Disc. The production of such lenses is based on UV‐induced polymerization of a mixture of a dimethacrylate monomer and an initiator on a spherical glass substrate. The shape of the polymer layer is defined with an aspherical transparent mold. This means that the coating is completely surrounded by glassy materials during processing. Raman spectroscopy is applied in situ to monitor the polymerization reaction under conditions that closely resemble the actual production process. As a result improvements can be made to the reaction conditions if necessary. Data are compared to results obtained with IR spectroscopy in an off‐line approach. The value of the in situ characterization using Raman spectroscopy is illustrated by the observation that contrary to expectation, the local rate of polymerization is not influenced by shrinkage effects caused by local variations in volume relaxation in the wedge‐shaped sample volume. Instead, even quartz glass mold plates with a thickness of 30 times that of liquid monomer were deformed to accommodate for thermodynamically required volume shrinkage. The assumption of isochoric polymerization in a confined volume turned out to be incorrect. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 1287–1295, 2006     

Effects of different polymerization protocols on the degree of conversion of two dual‐cured core buildup composites polymerized by light‐emitting diode and halogen light‐curing units

The aim of study was to investigate the effects of various curing protocols with quartz–tungsten halogen (QTH) or light‐emitting diode (LED) light‐curing units on the degree of conversion (% DC) of two dual‐cured core buildup resin composites. Two dual‐cured core buildup resin composites, Clearfil Dc Core Automix (CLF) and Grandio Core Dc (GR), were selected. Specimens were exposed to the polymerization protocols as follows: there was immediate photoactivation or photoactivation delayed by 2 or 5 min by a QTH or LED source, and one group was allowed to chemically polymerize and served as a control (n = 6). The % DC of the specimens was determined with attenuated total reflectance–Fourier transform infrared spectroscopy. The GR samples polymerized with QTH for the 5‐min‐delayed photoactivation had higher % DC values than those self‐cured, and the Clearfil Dc Core Automix (CLF) samples with immediate or delayed curing protocols with halogen yielded higher % DC values than the samples that were chemically polymerized. The comparison of the two resin composites polymerized with halogen showed a higher % DC for CLF than for GR in the 2‐min‐delayed photoactivation. On the other hand, when they were cured with LED, the % DC values of GR significantly increased after the 2‐min‐delayed photoactivation. In light of the results, it might be stated that CLF polymerized with QTH, could be the better option. GR provided adequate chemical polymerization; therefore, it might be useful in areas in which light curing is not possible. Clinicians should consider the polymerization characteristics of dual‐cured resin composites. The use of different composites may require the modification of the application procedures recommended by the manufacturer. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40560.     

Acrylic resins resisting oxygen inhibition during free‐radical photocuring. I. Formulation attributes

A resin system was found to be resistant to the formation of an oxygen‐inhibited layer when cured in air via conventional free‐radical photopolymerization. The resins, containing multifunctional acrylates and a high concentration of a photoinitiator, were applied as thin film coatings and photocured with either visible light (400–500 nm) or UV light (254 nm). Fourier transform infrared spectroscopy with an attenuated total reflection attachment and pencil hardness were used to assess the surface double‐bond conversion and the surface hardness of the coatings cured in air and without air, respectively. The surfaces of many tested resins could produce similar conversions under both curing conditions. Optimally formulated resins had a high conversion and hardness even when the irradiance was as low as 50 mW/cm² for the visible light and 4 mW/cm² for the UV light. The requirements for possessing such a unique curing property are presented. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Course of degradation and build‐up reactions in isotactic polypropylene during peroxide decomposition

In the investigation of the course of degradation and build‐up reactions during the decomposition of the tert‐butyl perbenzoate (TBPB) (at eight different concentrations) in isotactic polypropylene (iPP), it was found that, at the beginning of the peroxide decomposition at all investigated peroxide concentrations from 4.62–200 mmol/kg iPP, the degradation reactions of iPP prevailed. At the TBPB concentration of ≤37.0 mmol/kg iPP during the whole period of peroxide decomposition, degradation reactions leading to a lower of molecular mass of PP prevailed. But at higher peroxide concentrations of TBPB ≥74.4 mmol/kg iPP and at the later stage of peroxide decomposition, a predominance of the build‐up reactions, that is, an increase the molecular mass, was observed. The degradation and build‐up reactions were determined from the measurements of the melting‐flow indexes of the peroxide‐treated iPP samples. The reaction mechanism of the degradation and build‐up reactions in iPP is discussed. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 886–893, 2000     

Influence of pigment properties on UV‐curing efficiency

The curable formulations containing monomer‐diacrylate, photoinitiator‐p‐methoxybenzoyldiphenylphosphine oxide/benzyldimethylketal, additive reactive‐triethylamine, and inorganic thermoresistant pigments‐white, red, green, and blue were cured by UV exposure films. A series of experiments was carried out to investigate the relationship between the particle size distribution of the inorganic pigment and the colorimetric and mechanical properties of the UV acrylic curable coatings. Pendulum hardness and appearance of the films depend on the content and particle size distribution of the pigment. Optimal particle size distribution and pigment content were established to obtain the best films concerning their pendulum hardness and chromatic parameters. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 247–252, 2007     

Preparation and characterization of UV‐curable MPS‐modified silica nanocomposite coats

A series of UV‐curable nanocomposites were prepared with 3‐(trimethoxysilyl) propyl methacrylate (MPS) modified nanosilica under the initiation of 2,2‐dimethoxy‐1,2‐diphenylethan‐1‐one. It was found that MPS‐modified nanosilica together with free MPS could form transparent nanocomposite coats. As the particle size of nanosilica increased, the photopolymerization rate, final double bond conversion, and tack‐free time of nanocomposites increased while the surface roughness, glass‐transition temperature, and UV absorbance of nanocomposites decreased. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 2274–2281, 2005     

Selection of quaternary ammonium groups for optimizing properties of water‐soluble,photosensitive phenolic resins and study of their postcuring mechanism

This article deals with the selection of quaternary ammonium groups for synthesis of water‐soluble, photosensitive phenolic resins, containing acrylate and different quaternary ammonium salt groups (AQSPRs), via ring‐opening reactions of epoxy phenolic resin (EPR) with acrylic acid and with different tertiary amine‐protonic acid salts. Conversion of epoxy groups, solubility, photosensitive properties, and thermal decomposition of the different AQSPRs were compared. Modification of AQSPR with methanol solution of KOH to form phenolic resin containing both quaternary ammonium hydroxide groups and acrylate groups (AQHPR) was also studied. Characterization by IR spectrum, DSC, and thermal gravimetric analysis was carried out. The results showed that in the synthesis of AQSPRs containing different quaternary ammonium salt groups, the efficiency of ring‐opening reaction of epoxy phenolic resin with tertiary amine salt in terms of conversion of epoxy groups decreases in the following order: for the tertiary amine, N,N‐dimethyl benzylamine (DMBA) > triethylamine (TEA) > trimethylamine (TMA) > N,N‐dimethyl aniline (DMA) > triethanolamine (TENA) > tri(n‐butylamine) (TBA); for the protonic acid, HCl > HBr > HCOOH > HI > NaHSO₃ > Cl₃CCOOH > HClO₄ > HBF₄. All the AQSPRs except that from HClO₄ can be dissolved in water, methanol, DMF, or DMSO. The gel content formed during UV exposure decreases in the following order of acids used in forming quaternary ammonium salt groups: HCl > HCOOH > NaHSO₃ > Cl₃CCOOH; or decreases in the following order of tertiary amines or hydrohalic acids used in forming the quaternary ammonium groups: TMA. > TEA > DBMA; HCl > HBr > HI. During thermal decomposition of EPR with about half epoxy groups of EPR ring‐opened with tertiary amine salt at 160°C for 0.5 h, water‐insoluble product was formed. The insoluble content and the % decrease of epoxy groups or halide ions increase in the following order: TMA < TEA < DMBA; HCl < HBr < HI. The % decrease of epoxy groups for the insoluble residue is nearly equal to the % decrease of halide ions. A crosslinking reaction mechanism occurred in the thermal decomposition was thus proposed. During the modification of AQSPR with KOH, conversion of quaternary ammonium chloride groups can reach above 90%. The decomposition temperature of the quaternary ammonium groups was lowered from 204 to 120°C after modification of AQSPR with KOH. The photosensitive properties of the resin after modification became lower. It is better to react DMBA · HCl with EPR so as to obtain a product with higher conversion of epoxy groups, good water solubility, moderate photosensitivity, lower decomposition temperature, and better postcuring. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 91: 2914–2922, 2004     

Highly efficient antifouling property based on self‐generating hydrogel layer of polyacrylamide coatings

Pursuit of robust antifouling coatings is a persistent objective for marine materials. We present here the experimental realization of a series of polyacrylamide‐based resins with a self‐generating hydrogel layer, arising from the polymerization of acrylamide (AM), butyl acrylate, methacrylic acid, and AM derivatives. The mechanical strength and thermal stability are markedly enhanced due to the change of the structure of modified resins. The preliminary results indicate that resultant resins with crosslinking structure show satisfactory abrasion resistance and swelling properties. The results of antifouling panel testing in shallow submergence for three months reveal that the addition of AM derivatives leads to generation of a thin soft and dynamic layer of hydrogel, which enhances antifouling properties. The formation of hydrogel and self‐generating property make it promising in various antifouling applications. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 44111.