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A Continuous Synthesis of Polymethylmethacrylate Using a Microreactor Plant
摘要： We applied a microreactor to the synthesis of polymethylmethacrylate (PMMA) using a laboratory microreactor system with a production volume of 2–3 t per year, which enabled pseudo-continuous feeding by syringe pumps. When using a tube made of stainless steel, the values of the yield, number average molecular weight (Mn), and polydispersity index (PDI) reached 75.2%, 9.4×103, and 1.88, respectively. These results were in good accordance with the reported ones and a product with comparable properties was obtained. Then, we performed a continuous synthesis of PMMA for 8 h using a medium scale microreactor plant with a production volume of 100 t per year, which provided continuous feeding by triple cam driven pumps. When using a tube made of polytetrafluoroethylene (PTFE), it was confirmed that a product was continuously obtained for 8 h, whose yield, Mn, and PDI were on average 66.2%, 8.8×103, and 1.95, respectively. The variation in the yield, Mn, and PDI was within 5.7%, 4.5%, and 1.0%, respectively. For comparison, when using the laboratory microreactor system under the same reaction condition with a tube made of PTFE, the corresponding values of the yield, Mn, and PDI were 66.5%, 8.4×103, and 2.04, respectively. The difference in the results between the above two microreactor systems was 4.8% at a maximum (in Mn). Therefore, the synthesis of PMMA was continuously performed using the medium scale microreactor plant and the comparability of the reaction performance between the above two microreactor systems was ensured.
关键词： Microreactor Plant,Microreactor,Polymethylmethacrylate,Polymerization Reaction
更新于2025-09-23 15:23:52
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Tunable laser emissions in freestanding high-Q polymethylmethacrylate microbubbles
摘要： A freestanding dye-doped polymethylmethacrylate microbubble laser based on high-Q whispering gallery mode (WGM) is demonstrated. Low threshold tunable laser emissions are observed in microbubbles with different sizes fabricated by a volumetric pipette. The whispering gallery mode laser emissions in the 944 nm diameter microbubble have a low laser threshold of about 15 μJ pulse?1 and a 0.083 nm free spectral range. The smooth wall of the microbubble ensures a high quality factor of approximately 24 120. In addition, 590 nm–610 nm laser emission is achieved by the reabsorption effect of the dye. This work provides an efficient way to implement a freestanding, easily doped and low cost tunable WGM micro-laser.
关键词： polymethylmethacrylate,laser,microbubbles,whispering gallery mode
更新于2025-09-23 15:19:57
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Effect of ultrasonic treatment on the properties of multiwalled carbon nanotubes – polymethylmethacrylate composites: Effect of applied voltage and pressure on conductivity of the composites
摘要： The effect of sonication time during the synthesis of multiwalled carbon nanotubes – polymethylmethacrylate (MWCNT/PMMA) composites by coagulation technique on the MWCNT distribution in the bulk of the composites close to the percolation threshold was systematically studied by SEM and by measurements on specific resistivity in a wide range of voltages and external pressure. It was found that the resistivity of composites is irreversibly reduced up to 105 times during the first 1–3 measurements, while further measurements are characterized by high repeatability. Change of the composite resistivity during the measurements is discussed assuming that several types of contacts between the nanotubes changing during the measurement are present. It was found that an increase of the sonication time changed the ratio between ohmic and non-ohmic contacts. It affected the type of changes in the sample resistivity during the voltage variation in the range of 0–103 V/mm and resulted in a nonuniform dependence of the composite specific resistivity on the sonication time. An increase of the composite volume during the resistivity measurements was observed at the current densities above 4·10–8 A/cm2. New ohmic contacts were found to form when external pressure was applied due to squeezing of the polymer matrix from the space between adjacent nanotubes.
关键词： multiwalled carbon nanotube,nanocomposites,contacts between nanotubes,current-voltage characteristic,polymethylmethacrylate
更新于2025-09-16 10:30:52
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Mechanoluminescence of a composite based on polymethylmethacrylate and fine-disperse powder of SrAl <sub/>2</sub> O <sub/>4</sub> :(Eu <sup>2+</sup> , Dy <sup>3+</sup> ) phosphor
摘要： The paper deals with photoluminescence and deformation (mechanoluminescence) of a composite material based on fine-disperse powder of phosphor SrAl2O4:(Eu2+, Dy3+) and polymethylmethacrylate that is transparent in the visible region. The luminescent (sensory) layer responsive to mechanical action was formed in the surface layer of the polymethylmethacrylate. To excite of photoluminescence the short pulses of a nanosecond laser were used. Mechanoluminescence was excited by the short acoustic impulses generated by a nanosecond laser. New information about the energy levels of impurities was obtained.
关键词： Dy3+),SrAl2O4:(Eu2+,composite material,polymethylmethacrylate,mechanoluminescence,photoluminescence
更新于2025-09-11 14:15:04
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TiO2-SiO2-PMMA Terpolymer Floating Device for the Photocatalytic Remediation of Water and Gas Phase Pollutants
摘要： Floating photocatalytic devices are highly sought-after as they represent good candidates for practical application in pollutant remediation of large water basins. Here, we present a multilayer floating device for the photocatalytic remediation of contaminants present in water as well as of volatile species close to the water surface. The device was prepared on a novel tailored ter-polymer substrate based on methylmethacrylate, α-methylstyrene and perfluoroctyl methacrylate. The ad hoc synthesized support presents optimal characteristics in terms of buoyancy, transparency, gas permeability, mechanical, UV and thermal stability. The adhesion of the TiO2 top layer was favoured by the adopted casting procedure, followed by a corona pre-treatment and by the deposition of an intermediate SiO2 layer, the latter aimed also at protecting the polymer support from photocatalytic oxidation. The device was characterized by contact angle measurement, UV-vis transmittance and scanning electron microscopy. The final device was tested for the photocatalytic degradation of an emerging water pollutant as well as of vapors of a model volatile organic compound. Relevant activity was observed also under simulated solar irradiation and the device showed good stability and recyclability, prospecting its use for the photocatalytic degradation of pollutants in large water basins.
关键词： titanium dioxide,tetracycline,ethanol,composite,photocatalytic oxidation,polymethylmethacrylate
更新于2025-09-09 09:28:46