Benzil Dimethyl Ketal Research Articles

The development of a highly efficient photo‐initiator system and its application in the photo‐immobilization of activated sludge

ABSTRACTIn this study, a highly efficient photo‐initiator system was developed, which contained potassium persulfate, N, N, N ′, N ′‐tetramethylethylethylenediamine plus benzil dimethyl ketal. The photo‐initiator system could successfully initiate poly (ethylene glycol) dimethyl‐acrylate prepolymer to polymerize and crosslink under the irradiation of UV rays, in the presence of concentrated activated sludge, finally leading to the formation of immobilized activate sludge pellet beads. The presence of O2 and thickness of the reaction solution did not influence the photo‐immobilization process. Respiratory measurement result demonstrated that most activated sludge kept alive during the photo‐immobilization. Mechanical strength of the immobilized cells could be improved by optimizing contents and ratio of the initiator system. The corresponding mechanism was also discussed. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 39838.

Simultaneous Measurement of Temperature and Strain Using a Single Bragg Grating in a Few-Mode Polymer Optical Fiber

A few-mode polymer optical fiber (POF) with a highly photosensitive core doped with benzil dimethyl ketal (BDK) was fabricated and used to write a Bragg grating using the modified Sagnac optical interference technique. Bragg gratings formed in the few-mode POF show multiple reflection peaks. The response characteristics of the temperature and the strain of the few-mode POF Bragg grating (POFBG) were theoretically analyzed and experimentally verified. The results show almost the same strain response but a different temperature response for all guided modes in the few-mode POFBG. A new method of measuring temperature and strain simultaneously was proposed and demonstrated experimentally by using a single few-mode POFBG.

Analysis of multimode BDK doped POF gratings for temperature sensing

We report a temperature sensor based on a Bragg grating written in a benzil dimethyl ketal (BDK) doped multimode (MM) polymer optical fiber (POF) for the first time to our knowledge. The thermal response was further analyzed in view of theory and experiment. In theory, with the order of the reflected mode increasing from 1st to 60th order, for MM silica fiber Bragg grating (FBG) the temperature sensitivity will increase linearly from 16.2pm/°C to 17.5pm/°C, while for MM polymer FBG the temperature sensitivity (absolute value) will increase linearly from −79.5pm/°C to −104.4pm/°C. In addition, temperature sensitivity of MM polymer FBG exhibits almost 1 order larger mode order dependence than that of MM silica FBG. In experiment, the Bragg wavelength shift will decline linearly as the temperature rises, contrary to that of MM silica FBG. The temperature sensitivity of MM polymer FBG is ranged from −0.097nm/°C to −0.111nm/°C, more than 8 times that of MM silica FBG, showing great potential used as a temperature sensor.

使用BDK掺杂光敏聚合物光纤布拉格光栅的高灵敏度温度传感器的研究

A single-mode polymer optical fiber (POF) with highly photosensitive core doped with benzil dimethyl ketal (BDK) is fabricated and used for writing Bragg grating through the two-beam interference method. The Bragg wavelength of the grating is about 1570 nm, while the full-width at half-maximum (FWHM) of the reflection peak is 0.3 nm. The temperature response of POF Bragg grating is theoretically analyzed and experimentally measured in contrast to silica optical fiber Bragg grating (FBG). The result shows that the temperature character of POF Bragg grating is negative, which is opposite to the silica optical FBG. The absolute value of the temperature response of POF Bragg grating is one order of magnitude higher than that of the silica optical FBG, making POF Bragg grating appear to be very attractive for constructing temperature sensors with high resolution.

Gratings fabrication in benzildimethylketal doped photosensitive polymer optical fibers using 355 nm nanosecond pulsed laser

We report writing polymer optical fiber (POF) gratings in photosensitive POFs doped with benzildimethylketal (BDK) (BPOF in short) using a 355 nm laser for what we believe to be the first time. Both multimode and single-mode FBGs were fabricated with relatively low writing intensity. The enhanced photosensitivity of the doped POFs is also evident by the observation of obvious change in the UV-visible absorption.

Photoinitiated crosslinking of EPDM/inorganic filler blends and characterization of related properties

Photoinitiated crosslinking of ethylene-propylene-diene terpolymer (EPDM) blends filled with calcium carbonate, talc and calcined kaolin (CK) in the presence of benzil dimethyl ketal as photoinitiator and trimethylolpropane triacrylate as crosslinker and their related properties have been studied by different analytical methods. The results from gel content and heat extension determination show that the efficiency of photocrosslinking of EPDM increases with increasing the content of diene and its molecular weight. The EPDM blends with 100 phr different inorganic fillers can be photocrosslinked to gel content of above 60% by 5 s UV-irradiation under optimum conditions. Under the same conditions of irradiation, the orders of photocrosslinking rate and final gel content are EPDM/CaCO3 > EPDM/talc > EPDM/CK. The data from thermogravimetric analysis, dynamic mechanical thermal analysis, electrical properties, mechanical tests and scanning electron microscopy show that UV irradiation crosslinking apparently enhances the thermal stability, mechanical properties and electrical properties of the photocrosslinked EPDM/inorganic filler samples. Although the attenuated total-reflection FTIR data show that inorganic fillers can promote the surface photo-oxidation of EPDM/inorganic filler samples with increasing the irradiation time, the above related properties of the photocrosslinked EPDM blends irradiated within 5 s are enough to satisfy many applications in the cable industry.

Epoxy acrylate UV/PU dual‐cured wood coatings

AbstractFor 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

Photoinitiators with double and triple bonds

In continuation of our research on new chromophores for photoinitiators (PIs) we investigated a series of double and triple bond containing PIs based on benzophenone (BP), thioxanthone, benzil (BZ), benzildimethylketal (BDK), and hydroxyalkylphenone. UV-Vis spectroscopy revealed an absorption shifted up to 50 nm to the visible range of the spectrum. With steady state photolysis experiments, the rates of decomposition (Rd) were determined. Compared to the commercially available reference PIs the Rd of the new PIs were nearly identical. By quenching reactions with 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO), α-cleavage was identified for Type I initiators. Generally, all new compounds are suitable as PI especially for longer wavelengths. Nevertheless it has to be noted that the PI concentration has to be selected carefully to achieve optimum reactivity. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 289–301, 2008

Synthesis of a novel photosensitive prepolymer with trimethylolpropane triglycidylether and acrylic acid as starting materials

A novel photosensitive prepolymer of trimethylolpropane triglycidylether triacrylate was synthesized by utilizing trimethylolpropane triglycidylether and acrylic acid as two starting materials, triphenyl phosphine as catalyst and p-hydroxyanisole as inhibitor. The optimum synthesis conditions were that the concentration of triphenyl phosphine was 0.85wt% of reactants, the concentration of p-hydroxyanisole was 0.3wt% of reactants, and the reaction temperature was at 90–110°C. Benzil dimethyl ketal of a UV-cured initiator was added to the synthesized trimethylolpropane triglycidylether triacrylate to prepare a kind of UV-cured coating. The mechanical properties of the UV-cured films were determined, giving 28. 43 MPa of tensile strength, 965. 59 MPa of Young’s modulus and 4.10% of elongation at tear.

Photocrosslinking of an ethylene–propylene–diene terpolymer and the characterization of its structure and mechanical properties

AbstractAn ethylene–propylene–diene terpolymer (EPDM) was photocrosslinked under UV irradiation with benzil dimethyl ketal (BDK) as a photoinitiator and trimethylolpropane triacrylate (TMPTA) as a crosslinker. The efficiency of the photoinitiated crosslinking system EPDM–BDK–TMPTA, various factors affecting the crosslinking process (the photoinitiator and crosslinker and their concentrations, the irradiation time, the temperature, the atmosphere and UV‐light intensity, and the depth of the UV‐light penetration), and the mechanical properties of photocrosslinked EPDM were examined extensively through the determination of the gel contents, infrared spectra, and mechanical measurements. EPDM samples 3 mm thick were easily crosslinked with a gel content of about 90% after 30 s of UV irradiation under optimum conditions. The photoinitiating system of a suitable initiator combined with a multifunctional crosslinker such as BDK–TMPTA enhanced the efficiency of the photocrosslinking reaction, especially by increasing the initial rate of crosslinking. The gel content of photocrosslinked EPDM, which was determined by the content of diene in EPDM, the depth of the UV‐light penetration, and the light intensity, played a key role in increasing the mechanical properties of the photocrosslinked samples in this work. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 1837–1845, 2004

Fabrication of channel waveguides by photochemical self-developing in doped sol-gel hybrid glass

Sol-gel derived inorganic-organic hybrid glass (HYBRIMER) films doped with benzildimethylketal (BDK) were prepared. Refractive index and film thickness increase by UV exposure due to photoinduced polymerization and photolocking of high refractive index BDK. This enables the channel waveguides in HYBRIMER film to be fabricated without using a developing process, which is called photochemical self-developing (PSD). The waveguides consist of three layers with under-cladding and over-cladding of undoped HYBRIMER films and core of BDK-doped HYBRIMER film. A 1 × 4 splitter of waveguides was fabricated and demonstrated.

Photoinduced condensation of sol-gel hybrid glass films doped with benzildimethylketal

Sol-gel hybrid glass films doped with benzildimethylketal (BDK) were prepared from [(methacryloxy)propyl]trimethoxysilane, methacrylic acid, and zirconium n-propoxide. Polymerization of methacryl groups and polycondensation of alkoxides by UV illumination and baking were observed using Fourier-transformed infrared spectroscopy. Polymerization kinetics and refractive index increase depend on UV illumination time. The refractive index increase is sensitive to BDK concentration and agrees well with photodecomposition of BDK. Thus, it is found that the refractive index increase is made by incorporation of the radicals produced by photodecomposition of BDK in the network as well as polymerization of methacryl groups.

The effect of temperature on the kinetics of diacrylate photopolymerizations studied by Real-time FTIR spectroscopy

Real-time FTIR spectroscopy was used to study the effect of temperature on the kinetics of photopolymerization from room temperature up to 160°C. A highly viscous epoxy diacrylate and tripropylene glycol diacrylate (TPGDA) as systems of lower viscosity were used to study the influence of viscosity on the polymerization rate, the induction period, and the ultimate conversion. Different behaviour was observed at temperatures below and above ca. 90°C. In the epoxy diacrylate, the polymerization rate first distinctly increases with temperature due to the drop of viscosity, whereas in TPGDA the polymerization rate only little increases or is even independent of temperature depending on the photoinitiator used. The induction period decreases due to the decreasing solubility of oxygen in the reactive formulation. At higher temperatures, termination processes lead to a decrease of the polymerization rate if morpholino ketones are used for initiation. Simultaneously, the induction period re-increases. In contrast, systems initiated by a hydroxy alkylphenone or benzildimethyl ketal continue the trends from below 90°C.

Design of eutectic photoinitiator blends for UV/visible curable acrylated printing inks and coatings

The optimisation of photoinitiator systems used in UV printing inks and coatings has been carried out by means of Design of Experiments (Mixture designs). Mixture designs have been used to improve the reactivity of photoinitiator blends in order to design cost effective, synergistic, near eutectic photoinitiator blends for curing UV printing inks. Both the reactivity and bulk stability of photoinitiator blends have been studied. The photoinitiator blends consisted of three commercial photoinitiators, benzophenone (BP), isopropyl thioxanthone (ITX), which are Type II photoinitiators and benzil dimethyl ketal (BDK) a Type I photoinitiator. Ethyldimethylamino benzoate (EPD), a commercial aromatic tertiary amine, which is an efficient electron/proton donor was used to enhance the reactivity of the Type II photoinitiators. The results highlighted that the EPD content plays a crucial role in the final reactivity of the photoinitiator blends. Relatively high proportions of EPD with respect to the overall centroid (25% each component) were required to design photoinitiator blends of enhanced reactivity. These results agreed with mechanistic studies published in the literature where it was observed that with Type II photoinitiators, such as BP and ITX, the tertiary amine synergist acted as the main initiating radicals of the polymerisation process. On the other hand, from the stability point of view, high proportions of EPD decreased the stability (eutectic properties) of the photoinitiator blends. BP showed good solvating properties in the photoinitiator blends and had the highest influence on stability of the photoinitiators studied. Relatively high proportions of BP enhanced the stability of photoinitiator blends. Multiple response optimisation for stability and reactivity resulted in photoinitiator blends that exhibited both enhanced reactivity and stability.

Photograft polymerization of acrylate monomers and macromonomers on photochemically reduced PTFE films

The objective of this study was to explore and optimize the photograft polymerization of acrylate monomers and macromonomers upon premodified poly(tetrafluoroethylene) (PTFE) substrates, with a view toward applying these grafted materials as biomaterials. PTFE films were photochemically reduced by exposure to short wavelength ultraviolet (UV) light in the presence of the reducing agents, i.e., diphenyl ketyl radical anion, generated from a solution of benzophenone and sodium hydride in dimethylformamide (Noh et al., J. Polym. Sci. A, Polym. Chem., 35, 1499 (1997)). The photochemically reduced PTFE films were subsequently modified by photograft polymerization of acrylic acid, acrylamide, and poly(ethylene glycol) monoacrylate (PEG-Ac) by employing long wavelength UV irradiation with benzil dimethyl ketal as an initiator. The photochemically reduced PTFE films were good substrates for photograft polymerization, leading to surfaces with chemical compositions close to those of the respective homopolymers as determined by electron spectroscopy for chemical analysis. Photograft polymerization of PEG-Ac on the photochemically reduced surface was also explored with different concentrations (1, 2, 4, 6, and 8%; v/v) and molecular weights (200, 400, 1000, and 2000 g/mol) of PEG-Ac, different durations (5, 10, and 20 min) of long wavelength UV irradiation, and different concentrations (0.1, 0.2, 0.4, and 0.8%; v/v) of benzil dimethyl ketal. Higher concentrations and lower molecular weights of PEG-Ac generally led to more extensive photograft polymerization, whereas the concentration of benzil dimethyl ketal and duration of UV irradiation did not substantially influence the extent of photograft polymerization. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 3467–3482, 1997