A new fluidized bed coating process via photo‐initiated cationic polymerization

An ultraviolet (UV) photo‐polymerization particle coating process was developed by coupling the photo‐initiated cationic polymerization with the fluidized bed coating techniques. Unlike the conventional air‐suspension coating in the fluidized bed, the new process employs a UV curable composition instead of a solvent/water‐borne system as a coating material, which has a rapid curing rate and virtually no inhibition to oxygen and moisture. A modified fluidized bed coater equipped with a quartz window allows UV light to penetrate and to initiate the curing of photo‐sensitive polymerizable chemicals coated on the particles. A UV‐curable liquid composed of cycloaliphatic epoxide, oxetane, and triarylsulfonium cationic photo‐initiator was specifically formulated for the fluidized bed particle coating process. A systematic experimental approach including photo‐Differential Scanning Calorimetry, Fourier Transform Infrared Spectroscopy, and tackiness measurements has been developed to characterize the curing mechanism of the cationic UV curable formulations and to optimize the chemical compositions. The effects of the UV curable chemicals, viscosity of coating liquid, and the fluidization operating conditions on the physical properties of coated particles have been thoroughly investigated. Under optimized conditions, this novel process is very efficient as follows: particles can be coated very rapidly with ultra‐thin films of the cured chemicals, with little, if any, formation of particulate agglomeration. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers     

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     

Monomer conversion in a light‐cured dental resin containing 1‐phenyl‐1,2‐ propanedione photosensitizer

The efficiency of 1‐phenyl‐1,2‐propanedione (PPD) photosensitizer for the photopolymerization of a dental resin based on 2,2‐bis[4‐(2‐hydroxy‐3‐methacryloxyprop‐1‐oxy)phenyl]propane/triethylene glycol dimethacrylate was assessed. Experimental formulations containing PPD or/and camphorquinone (CQ) in combination with dimethylaminoethyl methacrylate (DMAEMA), ethyl‐4‐dimethylaminobenzoate (EDMAB), 4‐(N,N‐dimethylamino)phenethyl alcohol (DMPOH) and N,N‐3,5‐tetramethylaniline (TMA) at different concentrations were studied. The photopolymerization was carried out by means of a commercial light‐emitting diode (LED) curing unit. Near‐infrared spectroscopy was used to follow the consumption of double bonds versus irradiation time. No significant differences in the conversion values among formulations prepared with PPD in combination with DMAEMA, DMPOH and TMA were found. In contrast, the conversion was markedly increased by the presence of EDMAB. At low concentrations of photosensitizer, when used in combination with DMAEMA and EDMAB, PPD resulted in a final conversion equivalent to CQ. However, when DMPOH and TMA were used, PPD was found to be less efficient than CQ. In addition, at high photoinitiator concentration, the effectiveness of PPD was less than that of CQ independently of the co‐initiator used. The replacement of some CQ by an equivalent amount of PPD resulted in similar final monomer conversion as formulations having the same amount of CQ alone. The LED light source employed emitted in the wavelength range 410–490 nm with a peak around 470 nm, whereas the maximum molar absorbance of PPD was in the UV region. However, the small overlap of the spectral distribution of the LED curing lamp and the PPD absorption spectrum was compensated by the large extinction coefficient of PPD. Copyright © 2007 Society of Chemical Industry     

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.     

Synthesis and characteristics of photoactive‐hydrogenated rosin epoxy methacrylate for pressure sensitive adhesives

Hydrogenated rosin epoxy methacrylate (HREM), based on hydrogenated rosin and glycidyl methacrylate (GMA), was synthesized for use as an advanced tackifier in the UV‐crosslinking pressure sensitive adhesives (PSAs) system. The HREM, as a tackifier, contained UV‐curing sites; thus, allowed photopolymerization to occur by UV irradiation. This UV‐curable tackifier, HREM, can improve the curing rate and adhesion performance of UV‐crosslinking PSAs. The characteristics of HREM were analyzed by GPC and DSC and its synthetic mechanism studied using FTIR and ¹H NMR; the characteristic peaks of hydrogenated rosin and GMA vanished, but new peaks for HREM appeared. The PDI and the T_g by DSC were 1 and ?25.6°C, respectively. The photopolymerization of HREM was studied using photo‐DSC. Heat flow was observed during UV irradiation, and the curing rate and conversion both increased with rising photoinitiator content. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Allyl ether‐modified unsaturated polyesters for UV/air dual‐curable coatings. II: UV and air‐curing behavior

The photoinduced and peroxide‐induced polymerization behavior of dual‐curable allyl ether‐modified unsaturated polyester (AUPE) and vinyl ether (VE) used as a reactive diluent for dual‐curable coating have been studied by infrared spectroscopy (IR). For UV curing systems in N₂ atmosphere, the maleate's conversion and total conversion decrease with the increasing of allyloxy content. However, the rate and of copolymerization and conversion of VE are independent of allyloxy concentration. The copolymerization of allyl ether (AE) and vinyl ether occurs in the presence of maleate (MA) under UV irradiation. For air curing, the rate of copolymerization increases with allyloxy content. The ultimate conversion is the same irrespective of the allyloxy concentration. Because the electron‐rich double bond of allyloxy would become an electron‐deficient one through oxidation, the conversion of maleate decreases with increasing of the allyloxy content due to the enhancement of copolymerization of AE with VE. The ATR‐IR showed that different curing mechanisms occur in AUPE/VE system during air‐curing process. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 2771–2776, 2004     

Small‐molecule‐induced miscibility of isosorbide‐based polycarbonate with bisphenol A polycarbonate

In this study, we investigated the influence of the small molecule 4,4′‐thiobis(6‐tert‐butyl‐m‐methyl phenol) (AO300) on the miscibility of poly(isosorbide‐co‐1,4‐cyclohexanedimethanol carbonate) (IcC–PC) with bisphenol A polycarbonate (BPA–PC) through the formation of hydrogen‐bonding networks. Differential scanning calorimetry and morphological observation revealed that the initially, immiscible BPA–PC/IcC–PC blends become miscible through the addition of small molecules. Fourier transform infrared spectroscopy confirmed that intermolecular hydrogen bonds formed between the hydroxyl groups of AO300 and the carbonyl groups of the studied polycarbonates. These polycarbonates exhibited different hydrogen‐bonding behaviors and various degrees of glass‐transition temperature composition dependence. Dynamic mechanical analysis demonstrated that AO300 played an antiplasticization role in the BPA–PC/IcC–PC blends with improved storage moduli. To our knowledge, this article is the first to describe the miscibility of isosorbide‐based polycarbonate with BPA–PC. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44537.     

Binary phase solid‐state photopolymerization behavior of acrylate cryogels under different light sources

Two types of cryogels were obtained using 2‐hydroxyethyl acrylate (HEA) and 2‐hydroxyethyl methacrylate (HEMA) by homogeneous mixing with poly(ethylene glycol) diacrylate (PEGDA) as crosslinker at subzero temperature followed by photopolymerization with two different light initiation sources (high‐pressure Hg arc lamp and UV‐LED).The solution was frozen unidirectionally at ?60 °C before polymerization and finally photopolymerized at the same temperature. The cryogels were characterized using photo‐DSC, UV–vis and Fourier transform infrared spectroscopy, and scanning electron microscopy techniques. The cryogels cured with an LED light showed a higher polymerization rate and better morphological characteristics than ones cured with a high‐pressure Hg arc. The water intake ratio of HEA/PEGDA was higher than HEMA/PEGDA for both curing sources. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46686.     

Thermogravimetric and Fourier‐transform infrared analyses on the cure behavior of polycardanol containing epoxy groups cured by electron beam

In this study, the curing behavior of polycardanol containing epoxy groups (diepoxidized polycardanol) was exploited in terms of thermal stability and the cure reaction conversion by means of thermogravimetric analysis and Fourier‐transform infrared spectroscopy, respectively. The effect of photo‐initiator type and concentration and electron beam absorption dose in the presence of cationic photo‐initiators (triarylsulfonium hexafluorophosphate (P‐type) and triarylsulfonium hexafluoroantimanate (Sb‐type) on the cure behavior of diepoxidized cardanol (DEC) resin was investigated. The thermal stability of DEC with Sb‐type photo‐initiator was higher than that with P‐type one, being increased with increasing the concentration and electron beam absorption dose. The conversion of cure reaction was gradually increased with increasing the dose, showing the maximum at 800 kGy. The results revealed that Sb‐type photo‐initiator, the concentration of 2 or 3 wt %, and electron beam absorption dose of about 800 kGy may be preferable for initiating epoxy ring opening in the DEC molecules as well as for efficiently curing the DEC resin by electron beam irradiation. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41599.     

Preparation of multifunctional thiol‐ and acrylate‐terminated polyurethane: A comparative study on their properties in UV curable coatings

The multifunctional thiol‐ and acrylate‐terminated polyurethane (PU) has been successfully prepared for using as the main resin in the UV curable coatings. The structure and molecule weight of prepared PUs were analyzed by fourier transformed infrared spectroscopy (FTIR) and gel permeation chromatography, respectively. The results showed that the different terminal multifunctional groups have been grafted onto the PU and their difference in molecule weight was significant. Used as the main resin in coatings, the curing kinetic and percentage conversion of the different UV curing coatings system were investigated by real‐time FTIR method, and the effects of terminal functional groups and photoinitiator on the final conversion percentage and conversion rate were also compared. It is observed that the thiol‐terminated PU had higher conversion speed and final conversion percentage due to the remarkable effect of mercapto groups on reducing oxygen inhibition during UV curing process. The shrinkage, viscosity, and adhesion of UV curable coatings with thiol‐ and acrylate‐terminated PUs were also investigated and compared, and the results indicated that the former exhibited lower shrinkage and higher adhesion performances than the latter, along with the lower viscosity. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40740.     

Synthesis of UV‐curable difunctional silane monomer based on 3‐methacryloxy propyl trimethoxysilane (3‐MPTS) and its UV‐curing characteristics and thermal stability

In the present investigation, silicon containing UV‐curable difunctional monomer was synthesized by reacting 3‐methacryloxy propyl trimethoxysilane (3‐MPTS) with acrylic acid using anhydrous ether as a solvent under inert atmosphere. The synthesized acryloxymethacryloxy silane monomer was characterized by FTIR, ¹H‐NMR, and ¹³C‐NMR spectroscopy. The silane monomer along with 4 wt % photoinitiator (Darocure 1173) was cured under UV‐light for different exposure time. The curing characteristic of the monomer was investigated using FTIR spectroscopy. The conversion of the double bond due to curing has been evaluated from the peak intensity of the C?C double bond (at 1636 cm^?1) in the FTIR spectrum considering the peak intensity at 1720 cm^?1 due to C?O as internal standard. The maximum double bond conversion is observed to be 72%. The optimum cure time for the silane monomer has been estimated to be 7.8 sec. The UV‐cured sample decomposes at 440°C. The char residue is 35% at 700°C. The synthesized UV‐curable silane monomer may be useful for UV‐coating formulations, for fabrication of 3D‐objects by lithographic technique and as a precursor for organic–inorganic hybrid materials. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Preparation and characterization of ultraviolet‐curable nanocomposite coatings initiated by benzophenone/n‐methyl diethanolamine

A series of ultraviolet‐curable nanocomposite coatings were prepared with condensed nanosilica particles and with benzophenone/n‐methyl diethanolamine as the initiator. The nanosilica that incorporated into the nanocomposites did not aggregate even when the nanosilica concentration was as high as 22.5%. Adding nanosilica increased the curing speed, thermal stability, and ultraviolet shielding properties of the nanocomposites without reducing the transparency of the ultraviolet‐curing coatings. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 912–918, 2005     

Synthesis of cationic UV‐curable methacrylate copolymers and properties of the cured films of their composites with alicyclic epoxy resin

Cationic UV‐curable methacrylate copolymers consisting of glycidyl methacrylate, iso‐butyl methacrylate, and 2,2,3,4,4,4‐hexafluorobutyl methacrylate were synthesized, and their structures were characterized by FTIR, ¹H NMR, and ¹³C NMR. A series of UV‐cured composite films based on the synthesized copolymers and an alicyclic epoxy resin, 3,4‐epoxycyclohexylmethyl‐3,4‐epoxycyclohexanecarboxylate (CE) were obtained through photopolymerization. Their surface contact angle, chemical ability, gloss, light transmittance, thermal behavior, micromorphology, and shrinkage were investigated. Results indicated that these cured resins showed excellent gloss and visible light transmittance; after the combination of the copolymers and CE, and in the presence of fluorine in the curing systems they exhibited relatively fine water resistance, chemical, and thermal stability. It was observed that these copolymers could decrease the degree of the volume shrinkage to CE. The UV‐curable materials may have promising applications in optical fiber coatings, flip chip and Organic Light‐Emitting Diode (OLED) packing. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

A novel bio‐based phthalonitrile resin derived from catechin: synthesis and comparison of curing behavior with petroleum‐based counterpart

The development of bio‐based thermosetting resins with good thermal stability can potentially afford sustainable polymers as replacements for petroleum‐based polymers. We report a practical route to a novel catechin‐based phthalonitrile resin precursor (CA‐Ph), which contains free phenolic hydroxyl groups that result in ‘self‐curing’ at elevated temperatures to afford a thermostable polymer. Comparison of the performance of this CA‐Ph resin with that of a conventional petroleum‐based bisphenol A phthalonitrile resin (BPA‐Ph; containing 5 wt% of the curing agent 4,4′‐diaminodiphenylsulfone) revealed that CA‐Ph exhibits a lower melting point and curing temperature. Cured CA‐Ph resin retains 95% of its weight at 520 °C under a nitrogen atmosphere, which compares favorably with results obtained for BPA‐Ph resin that retains 95% of its weight at a lower temperature of 484 °C. Kinetic results indicated that the curing reactions of both CA‐Ph and BPA‐Ph systems follow an autocatalytic mechanism. These results suggest that catechin is a useful bio‐based feedstock for the preparation of self‐curing and thermally stable phthalonitrile resins for advanced technological applications. © 2017 Society of Chemical Industry     

Preparation and properties of bisphenol A‐based bis‐phthalonitrile composite laminates

A series of bisphenol A (BPA)‐based 2,2‐bis‐[4‐(3,4‐dicyanophenoxy)phenyl]propane (BAPh) prepolymers and polymers were prepared using BPA as a novel curing agent. Ultraviolet–visible and Fourier transform infrared spectroscopy spectrum were used to study the polymerization reaction mechanism of the BAPh/BPA polymers. The curing behaviors were studied by differential scanning calorimetry and dynamic rheological analysis, the results indicated that the BAPh/BPA prepolymers exhibit large processing windows (109.5–148.5°C) and low complex viscosity (0.1–1 Pa·s) at moderate temperature, respectively. Additionally, the BAPh/BPA/glass fiber (GF) composite laminates were manufactured and investigated. The flexural strength and modulus of the composite laminates are 548.7–632.8 MPa and 25.7–33.2 GPa, respectively. The thermal stabilities of BAPh/BPA/GF composite laminates were studied by thermogravimetry analysis. The temperatures at 5% weight loss (T_5%) of the composite laminates are 508.5–528.7°C in nitrogen and 508.1–543.2°C in air. In conclusion, the BAPh/BPA systems can be used as superior matrix materials for numerous advanced composite applications. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

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

In 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.     

Behavior of UV‐cured print inks on LDPE and PBAT/TPS blend substrates during curing,postcuring, and accelerated degradation

During radiation curing, a reactive formulation is converted into a highly crosslinked coating film by means of polymerization reactions. This three‐dimensional (3D) network is resistant to external degrading factors as it cannot be undone by any physical–chemical means. In this study, various ultraviolet (UV)‐curable ink formulations with different pigments were developed. The behavior of the UV‐curable inks was evaluated during UV curing in a photocalorimeter or in a UV tunnel. Inks were exposed to accelerated aging in an accelerated weathering chamber and their physical–chemical properties were investigated. The presence of residual fractions of unreacted species trapped in the 3D network formed during UV curing interferes with the degradation of the main structure during exposure in the weathering chamber. The ink formulations that did not easily absorb UV light increased in gloss and hardness, indicating that residual crosslinking is taking place at the same time that degradation is occurring. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 41116.     

Synthesis and ultraviolet‐curing behaviors of vinyl ether functionalized polyurethane oligomers

The vinyl ether functionalized oligomer is one of the most basic components of vinyl ether functionalized materials for cationic UV‐curable coatings. In this study, three types of vinyl ether functionalized polyurethane oligomers (i.e., polyether, polyester, and polydimethylsiloxane) were synthesized with diisocyanate, diol, and hydroxyethyl vinyl ether. These oligomers were characterized by IR, ¹H‐NMR, and ¹³C‐NMR spectroscopy. The effect of the raw material ratio on the oligomer, UV‐curing behaviors, and thermal properties of these oligomers were investigated. The UV‐curing behavior was analyzed by real‐time Fourier transform infrared spectroscopy. The vinyl ether terminated polyester urethane oligomer exhibited better UV curing, with a higher final conversion and maximum UV‐curing rates. In addition, the light intensity was enhanced for oligomers with better UV‐curing properties. Research on these vinyl ether functionalized oligomers is essential to the development and applications of cationic vinyl ethers systems. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40501.     

Synthesis and UV curing kinetics of rapidly UV‐curable hyperbranched polycarbosiloxanes

Hyperbranched polycarbosiloxanes with peripheral photo‐crosslinkable groups were synthesized through controllable hydrosilylation reaction from A₂‐type and CB₃‐type monomers. The polymerization of the monomer pairs was monitored using Fourier transform infrared spectroscopy, from which it was found that vinyl silane and methacrylate groups reacted with hydride silane from the beginning of the reaction. The results thus suggest a step‐by‐step polymerization rather than a two‐step process for this system. The polycarbosiloxanes could be cured rapidly in either nitrogen or air atmosphere, this feature making them attractive for potential application as precursors of advanced ceramic devices with complex structures. The effects of light intensity, reaction temperature and atmosphere on the UV curing rate (R_p) and conversion (α) of the photo‐crosslinkable groups were characterized carefully, and the curing kinetics was also investigated systematically. The results show that R_p and α increased with an increase of light intensity or temperature, and that the inhibiting effect of oxygen in air could be suppressed by enhancing the irradiation intensity. Copyright © 2010 Society of Chemical Industry     

Single component self‐curable aqueous‐based PU system with new aziridinyl curing agent

The self‐emulsified aqueous‐based polyurethane (PU) consists of carboxyl group, which is an ionic center not only stabilizing the aqueous polymer dispersion but also serving as the curing site toward aziridinyl curing agent. Two new aziridinyl curing agents, HDI‐AZ and ADA‐AZ, are prepared from an addition reaction of aziridine to hexamethylene diisocyanate (HDI) and adipic acyl chloride (ADA), respectively. These curing agents are added separately into NCO‐terminated PU prepolymer before or after the water dispersion process. The resulting PU dispersion becomes a single component self‐curable aqueous‐based PU system. The cured PU is obtained from this single component PU dispersion on drying at ambient temperature. The improved PU properties demonstrate the feasibility of this convenient single component self‐curable aqueous‐based PU system. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91:1997–2007, 2004