Photocurable inkjet inks based on cationically curable materials are a promising new technology with many advantages and some problems yet to be solved. One of the latter is the long-term stability of liquid inks. Reactive monomers are stable in the dark at room temperature for a long time. When a photoinitiator (iodonium salt) is added, premature gelation takes place within several days, depending on the temperature. Tertiary amine, hindered amine, hindered phenol, a quinone derivative, a sulphur-based antioxidant, beta-carotene and their selected mixtures were tested as potential inhibitors of premature cationic polymerization by being subjected to accelerated ageing at higher temperatures. The influence of additives on photoinitiated polymerization was studied by means of FTIR spectroscopy. The inhibition effect of additives was ascertained by monitoring the changes in viscosity during long-term temperature exposition as well. The system used for the study was a model system containing a cycloaliphatic epoxide monomer, oxetane monomers and a diaryliodonium salt photoinitiator. Amines, in contrast to antioxidants, proved to be effective as premature polymerization inhibitors. 相似文献
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. 相似文献
We have previously shown that in HeLa cells treated with a variety of agents there is an increase in cell surface peptidase (CSP) activity in those cells undergoing apoptosis. The increase in CSP activity observed in UVB-irradiated cells undergoing apoptosis was unaffected when the cultures were treated with the aminopeptidase inhibitor bestatin, and matrix metalloprotease inhibitor BB3103, but greatly enhanced when treated with the caspase 3 inhibitor-DEVD, and reduced in the presence of the poly(ADP-ribose) polymerase (PARP) inhibitor-3-aminobenzamide (3AB). Neither 3AB nor DEVD had an effect on the gross morphology of the apoptotic cells observed under electron microscopy, nor did they have an effect on phosphatidylserine eversion on the cell membrane, or that of PARP cleavage. All the agents except for DEVD had no effect on the level of caspase 3 activity in the cells. The results suggest that other caspases may cleave PARP in these cells. Both 3AB and DEVD treatment reduced the level of actin cleavage seen in the apoptotic cells. The increase in CSP activity observed in cells undergoing UVB-induced apoptosis appears to involve PARP but not caspase 3. 相似文献
Surface properties of epoxy coatings are modified by PDMS additives in cationic UV curing of a cycloaliphatic epoxy resin. The cured films show a very high hydrophobicity that does not depend on PDMS concentration, indicating that a threshold is reached even at 0.3 wt% additive. A slight increase of the water contact angle as a function of PDMS molecular weight is observed. The additive selectively modified the air‐side of the film, while the glass‐side retains the surface properties of the pure resin. This segregation phenomenon permits to obtain highly hydrophobic films with still good adhesion properties on polar substrates, which is an important advantage over common surface‐modified resins.
Ultraviolet (UV) irradiation is commonly applied as a secondary disinfection process in chlorinated pools. UV-based systems have been reported to yield improvements in swimming pool water and air chemistry, but to date these observations have been largely anecdotal. The objectives of this investigation were to evaluate the effects of UV irradiation on chlorination of important organic-N precursors in swimming pools.Creatinine, L-arginine, L-histidine, glycine, and urea, which comprise the majority of the organic-N in human sweat and urine, were selected as precursors for use in conducting batch experiments to examine the time-course behavior of several DBPs and residual chlorine, with and without UV254 irradiation. In addition, water samples from two natatoria were subjected to monochromatic UV irradiation at wavelengths of 222 nm and 254 nm to evaluate changes of liquid-phase chemistry. UV254 irradiation promoted formation and/or decay of several chlorinated N-DBPs and also increased the rate of free chlorine consumption. UV exposure resulted in loss of inorganic chloramines (e.g., NCl3) from solution. Dichloromethylamine (CH3NCl2) formation from creatinine was promoted by UV exposure, when free chlorine was present in solution; however, when free chlorine was depleted, CH3NCl2 photodecay was observed. Dichoroacetonitrile (CNCHCl2) formation (from L-histidine and L-arginine) was promoted by UV254 irradiation, as long as free chlorine was present in solution. Likewise, UV exposure was observed to amplify cyanogen chloride (CNCl) formation from chlorination of L-histidine, L-arginine, and glycine, up to the point of free chlorine depletion. The results from experiments involving UV irradiation of chlorinated swimming pool water were qualitatively consistent with the results of model experiments involving UV/chlorination of precursors in terms of the behavior of residual chlorine and DBPs measured in this study.The results indicate that UV254 irradiation promotes several reactions that are involved in the formation and/or destruction of chlorinated N-DBPs in pool settings. Enhancement of DBP formation was consistent with a mechanism whereby a rate-limiting step in DBP formation was promoted by UV exposure. Promotion of these reactions also resulted in increases of free chlorine consumption rates. 相似文献