A systematic study of maghemite/PMMA nano-fibrous composite via an electrospinning process: Synthesis and characterization

In this study, maghemite/PMMA nano-fibrous composites have been successfully fabricated by using the electrospinning process. PMMA nano-fibres have been selected to be used as the matrix; the PMMA was dissolved in three diverse solvents (Acetone, THF and DMF) in order to obtain fine PMMA nano-fibres. As a result, the PMMA–DMF proved to be the most appropriate polymer solution among the three solvents, with its impressive defect-free surface morphology results. The production of maghemite using Massart’s procedure resulted in nano-particles with an average diameter of 4.98 ± 0.13 nm (using transmission electron microscopy (TEM)). Maghemite nano-particle were then mixed with a prepared polymer solution in order to fabricate maghemite/PMMA nano-fibrous composite. Furthermore, the investigation of the morphology and structure of the composite was carried out using field emission scanning electron microscopy (FESEM), Energy-dispersion X-ray spectroscopy (EDX), Alternating Gradient Magnetometer (AGM), Fourier transform infrared spectrometer (FTIR), X-ray diffraction (XRD) and tensile strength measurement devices. The results indicated that there was a great amount of maghemite, both in and on the composite’s surface, which can be utilized in the purpose of magnetic applications.     

Experimental and thermomechanical analysis of friction stir welding of poly(methyl methacrylate) sheets

In the present work, the feasibility of friction stir welding (FSW) of poly(methyl methacrylate) sheets was studied experimentally and theoretically by employing thermomechanical simulations. The effect of processing parameters including tool plunge depth, tilt angle, tool rotational speed (w), and transverse velocity (v) was investigated to determine suitable conditions to attain sound and defect-free joints. It is shown that a low tool plunge depth of 0.2?mm and a tilt angle of 2° provide suitable material flow to gain sound joints. By controlling the heat input into stir zone by increasing the tool rotational speed and decreasing linear velocity, the formation of defects can be minimised. Mechanical examinations in both longitudinal (LS) and transverse (TS) directions indicate that the highest joint strength of 57?MPa (for LS) and 42?MPa (for TS) are obtained at processing conditions of w?=?25?mm?min^?1 and v?=?1600?rev?min^?1. The measured tensile strengths are 81 and 60% of the base polymer, respectively.     

反相微乳液制备AgCl/PMMA复合胶乳及其抗菌性能

以聚乙二醇辛基苯基醚(OP)为表面活性剂,甲基丙烯酸甲酯(MMA)为油相构筑的反相微乳液合成纳米Ag Cl粒子,然后通过微乳液聚合制备Ag Cl/PMMA复合胶乳。利用紫外-可见吸收光谱(UV-vis)和透射电镜(TEM)研究微乳液中表面活性剂浓度(cop)、水相中盐浓度(csalt)对纳米Ag Cl粒子的形成及形貌影响,结果发现合成的Ag Cl粒子近似球状,粒径在5 nm左右;在反相微乳液中随cop、csalt的增加,形成的纳米Ag Cl粒子数增多、平均粒径有所减小。Ag Cl/PMMA复合胶乳对大肠杆菌表现出明显的抗菌活性。通过反相微乳液及其聚合技术制备包含有纳米Ag Cl的复合胶乳,方法简便、易于放大,所制备的Ag Cl/PMMA复合胶乳作为抗菌剂具有良好的应用前景。     

沥青对PMMA热分解及燃烧性能的影响研究

采用自由基聚合法制备了纯的和添加了1.5%(质量分数)沥青的聚甲基丙烯酸甲酯(PMMA),用热重(TG)分析和锥形量热仪测试了其热分解和燃烧性能并研究了其热分解动力学。TG分析结果表明,添加质量分数为1.5%的沥青,PMMA在氮气中和空气中的失重速率最大时温度分别由纯PMMA的379.2℃和308.9℃提高至386.2℃和354.7℃,热降解表观活化能显著提高;锥形量热仪测试结果表明沥青使PMMA的点燃时间缩短,燃烧更平稳,加入沥青后,点燃后300 s内的质量损失速率和热释放速率平均值分别由纯PMMA的0.212 g/s和569 k W/m2降至0.191 g/s和514 k W/m2,CO产率和烟释放速率平均值分别由0.009 9 kg/kg和0.027 0 m2/s增至0.012 0 kg/kg和0.036 8 m2/s。沥青提高PMMA燃烧性能的主要原因是抑制了PMMA的热分解。     

Optical parameters and absorption studies of UV‐irradiated azo dye‐doped PMMA films

PMMA and PMMA films doped with different contents of azo dye have been made by using the casting technique. The absorption spectral analysis showed that the doped films have two absorption bands attributed to the π‐π* and n‐π* transition of chromophore groups. These bands disappear upon UV‐irradiation, suggesting that the studied system undergoes a photo degradation process. The absorption coefficient and optical energy gap (E_g) have been obtained from the absorption edge in the 200–900 nm range. It was found that E_g decreases with increasing doping levels, whereas it increases with increasing irradiation time. The width of the tail of localized states in the band gap (ΔE) was evaluated using the Urbach edge method. Some optical parameters were determined from the reflection and transmission spectra in the spectral range of 200–2500 nm. The dependence of the refractive index on irradiation time and doping level have been discussed. It was found that the photo‐induced refractive index changes are very large. These changes suggest the applicability of the studied system in optical devices. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Glass transition temperature enhancement of PMMA through copolymerization with PMAAM and PTCM mediated by hydrogen bonding

A series of poly(methyl methacrylate-co-methacrylamide-co-tricyclodecyl methacrylate) (PMMA-co-PMAAM-co-PTCM) copolymers possessing high glass transition temperatures and high transparency are prepared. By incorporating the aliphatic tricyclodecyl methacrylate moiety into the PMMA-co-PMAA main chain results in high glass transition temperature and high transparency of PMMA-based polymeric material. The TCM content affects the fraction of hydrogen bonding in these terpolymers, small content of TCM does not sacrifice the fraction of hydrogen-bonded association in and does not cause T_g decrease. The extent of free amide group plays the major role in dictating moisture absorption of terpolymers. The incorporation of TCM significantly reduces the moisture absorption of terpolymers due to its hydrophobic and bulky tricyclodecyl group. In addition, the TCM plays the role of inert diluent to convert portion of the strong self-associated hydrogen bonded amide groups into inter-associated hydrogen bonding between carbonyl groups of ester units and MAAM.     

偏振激光诱导的薄膜表面周期性自组织结构

本文研究了激光诱导的周期性表面结构(LIPSS)在聚甲基丙烯酸甲酯(PMMA)薄膜表面的形成过程。在导电玻璃衬底上制备得到PMMA薄膜,经p偏振的XeCl准分子激光照射后形成周期性的褶皱结构。用原子力显微镜(AFM)观察发现,形成的褶皱结构周期具有纳米量级,且当引入外加电场时,褶皱形成所需的激光脉冲数减少到2。当外加电压增加到30V时,褶皱的周期间隔明显减小,LIPSS变得不可控,出现了柱状的自组织结构。与直接用准分子激光照射的薄膜样品相比,外加辅助电压的引入改变了PMMA样品表面褶皱结构形成的时间和周期大小,褶皱形成的内部驱动力也发生了变化。     

PMMA液体现场浇筑膜及其应用前景

介绍了聚甲基丙烯酸甲酯(PMMA)液体现场浇筑膜的概念和性能,对其特点、应用前景和注意事项等进行了讨论.     

From plastic-waste to H2: A first approach to the electrochemical reforming of dissolved Poly(methyl methacrylate) particles

The development of sustainable processes for the recycling of plastic is a major environmental issue to reduce the pollution by this kind of waste. The electro-oxidation of plastic wastes in electrolysers powered by renewable energies is a promising option to produce hydrogen at low temperature while diminishing the energy demand compared to Oxygen Evolution Reaction (OER). Poly (methyl-methacrylate) (PMMA) particles, a widely used polymer, were dissolved (0.1–2% wt.) in an isopropanol(IPA)/H₂O binary solvent and electro-oxidized on Pt/C-based electrodes in a liquid batch electrochemical cell at 70 °C in acidic media. Despite the dissolution strategy, polymer macromolecules partially block the accessibility of the active sites of a commercial electrode and strongly degrades its electrochemical performances mainly linked to IPA electro-oxidation. The preparation of a more porous electrode supported on carbon paper was found to strongly hinder this deactivation. Furthermore, the electrooxidation of PMMA or PMMA-derived molecules can be performed during cyclic voltammetries up to 1.4 V and chrono-amperometries at 1.4 V.     

The effects of gas-phase and in-depth radiation absorption on ignition and steady burning rate of PMMA

Although well studied, there are still interesting features about the ignition and steady burning rate behaviour of PMMA when heated by thermal radiation. In this contribution, the dependence on external heat flux of ignition delay time and steady mass flux of PMMA are investigated numerically. Ignition is modelled by the critical mass flux criterion. The heat transfer model includes effects of heat lost by out gassing, change of volume during degradation and absorption of radiation in both condensed and gaseous phases. Model results are compared to experimental data for both ignition delay time and quasi-steady mass flux across a range of heat fluxes from 20 to 210 kW m⁻² and the importance of both gas-phase and condensed-phase radiation absorption effects are discussed.