Sonochemical approach for synthesis of zinc oxide-poly methyl methacrylate hybrid nanoparticles and its application in corrosion inhibition

Hybrid nanoparticles (HNPs) with zinc oxide and polymethyl metha acrylate (inorganic/ polymer) were synthesized through the exploitation of ultrasound approach. The synthesized HNPs were further characterized employing transmission electron microscopy and x-ray diffraction. ZnO-PMMA based HNPs exhibit excellent protection properties to mild steel from corrosion when gets exposed to acidic condition. Electrochemical impendence spectroscopy (EIS) analysis was accomplished to evaluate the corrosion inhibition performance of MS panel coated with 2 wt% or 4 wt% of HNPs and its comparison with bare panel and that of loaded with only standard epoxy coating., Tafel plot and Nyquist plot analysis depicted that the corrosion current density (I_corr) decreases from 16.7 A/m² for bare material to 0.103 A/m² for 4% coating of HNPs. Applied potential (E_corr) values shifted from negative to positive side. These results were further supported by qualitative analysis. The images taken over a period of time indicated the increase in lifetime of MS panel from 2 to 3 days for bare panel to 10 days for HNPs coated panel, showing that ZnO-PMMA HNPs have potential application in metal protection from corrosion by forming a passive layer.     

表面喷砂对有机玻璃沿面闪络性能影响

绝缘子表面粗糙处理是提升其沿面闪络性能的重要途径,表面粗糙化处理方式不当,极易带来表面结构不均匀,难以获得稳定耐压性能的绝缘材料。为提升绝缘子表面粗糙处理的均匀性,本文利用表面喷砂技术对圆柱形有机玻璃(PMMA)绝缘子进行了粗糙化处理研究,以球形二氧化硅(SiO2)颗粒为工作介质,研究了不同喷砂粒径、氢氟酸后处理等因素对绝缘材料表面形貌和组分的影响,并利用短脉冲高压测试平台对喷砂处理前后有机玻璃绝缘子样品进行了真空沿面闪络性能测试。研究结果表明,喷砂处理在有机玻璃表面形成了较为均匀的凹坑,HF酸能够有效去除表面残留的SiO2颗粒,具有表面喷砂粗糙结构的绝缘子沿面闪络电压得到了稳定提升,相较于未处理的绝缘子闪络电压提升了约80%。     

On the use of edge cracked short bend beam specimen for PMMA fracture toughness testing under mixed-mode I/II

In this paper an inclined edge cracked short beam specimen subjected to symmetric three-point bend loading was designed and examined for conducting mixed-mode I/II fracture toughness experiments. The aspect ratio (i.e. length to width ratio) and the loading span distance are considered much lower than the other conventional cracked bend beam samples. Crack tip parameters such as stress intensity factors and T-stress were computed numerically for this specimen by several finite element analyses and it was demonstrated that the specimen is able to produce full combinations of mode I and II including pure mode II. The practical capability of the short bend beam specimen was studied experimentally by conducting a set of mixed-mode fracture tests on PolymethylMethacrylate (PMMA) as a well-known model brittle material. The critical stress intensity factors, the direction of fracture kinking and the path of fracture trajectory were investigated both experimentally and theoretically using two stress and strain-based fracture criteria. The fracture toughness of tested PMMA was decreased by moving towards mode II case due to the effect of T-stress on the fracture mechanism of the short bend beam specimen.     

Chlorhexidine Loaded Cyclodextrin Containing PMMA Nanogels as Antimicrobial Coating and Delivery Systems

Antimicrobial nanogels, aggregates, and films are prepared by complexation of the antiseptic and bacteriostatic agent chlorhexidine (CHX) for medical and dental applications. A series of α‐, β‐, and γ‐cyclodextrin methacrylate (CD‐MA) containing hydrophobic poly(methyl methacrylate) (PMMA) based nanogels are loaded quantitatively with CHX in aqueous dispersion. The results show that CHX is enhancedly complexed by the use of CD‐MA domains in the particles structure. β‐CD‐MA nanogels present the highest uptake of CHX. Furthermore, it is observed that the uptake of CHX in nanogels is influenced by the hydrophobic PMMA structure. CHX acts as external cross‐linker of nanogels by formation of 1:2 (CHX:CD‐MA) inclusion complexes of two β‐CD‐MA units on the surfaces of two different nanogels. The nanogels adsorb easily onto glass surfaces by physical self‐bonding and formation of a dense crosslinked nanogel film. Biological tests of the applied CHX nanogels with regard to antimicrobial efficiency are successfully performed against Staphylococcus aureus .

     

Interaction potential models for bulk Zns,Zns nanoparticle,and Zns nanoparticle‐PMMA from first‐principles

An ab initio derived transferable polarizable force‐field has been developed for Zinc sulphide (ZnS) nanoparticle (NP) and ZnS NP‐PMMA nanocomposite. The structure and elastic constants of bulk ZnS using the new force‐field are within a few percent of experimental observables. The new force‐field show remarkable ability to reproduce structures and nucleation energies of nanoclusters (Zn₁S₁‐Zn₁₂S₁₂) as validated with that of the density functional theory calculations. A qualitative agreement of the radial distribution functions of Zn? O, in a ZnS nanocluster‐PMMA system, obtained using molecular mechanics molecular dynamics (MD) and ab initio MD (AIMD) simulations indicates that the ZnS–PMMA interaction through Zn? O bonding is explained satisfactorily by our force‐field. © 2015 Wiley Periodicals, Inc.     

Comparison of PVDF/MWNT,PMMA/MWNT,and PVDF/PMMA/MWNT nanocomposites: MWNT dispersibility and thermal and rheological properties

Pristine multi-walled carbon nanotubes (MWNTs) were incorporated into poly(vinylidene fluoride) (PVDF), poly(methyl methacrylate) (PMMA), and PVDF/PMMA blends to achieve binary and ternary nanocomposites. MWNTs were more compatible with the PVDF matrix than with the PMMA-containing matrices. MWNT addition did not alter the development of α-form PVDF crystals in the binary/ternary composites. Nucleation and overall isothermal crystallization of PVDF were enhanced by the presence of MWNTs, and enhancements were optimal in the PVDF/MWNT binary composites. Avrami analysis revealed that addition of MWNTs led to more extensive athermal-type nucleation of PVDF, and that PMMA slightly decreased the crystal growth dimension of PVDF. The equilibrium melting temperature (T_m°) of PVDF increased in the binary composites but remained nearly constant in the ternary system. Thermal stability was enhanced in the binary/ternary composites, and enhancements were more evident in the air environment than in nitrogen. Rheological property measurements revealed that the intensely entangled chains of high-molecular weight PVDF dominated the rheological response of PVDF-included samples in the melt state. A (pseudo)network structure was developed in each of the PVDF-included samples as well as in the 1 phr MWNT-added PMMA/MWNT composite. The storage moduli of the PVDF, PMMA, and PVDF/PMMA:1/1 blend increased to 37%, 22% and 34%, respectively, at 40 °C after addition of 1 phr MWNT.     

旋涂速度对制备P3HT有机场效应晶体管性能的影响

采用溶液化的方法制备了以PMMA为绝缘层、P3HT为有源层的有机场效应晶体管.研究了P3HT有源层和PMMA绝缘层的旋涂速度对器件性能的影响.实验结果表明,当P3HT和PMMA的旋涂速度均为2 000 r/min时,器件的性能最佳.峰值场效应迁移率为6.84×10^-2 cm²·V^－1·s^－1.结果表明,选择适当的旋涂速度是一种有效提高溶液化制备有机场效应晶体管性能的方法.     

Limitation on crack speed for a strip-craze model applied to PMMA

A strip-craze model is proposed to study crack propagation in polymers. A nonlinear differential equation is derived to govern the dynamic process of crack propagation. The viscous feature of the material in the craze zone is taken into account by means of an experimentally determined relationship between the craze stress and crack speed. By fitting experimental data of PMMA into the model, some parameters including the strip-craze length are deduced. A non-singular stress is introduced to control the crack propagation with a strip craze at its tip. Variations of the crack length and the crack speed with time are computed and their dependence on the non-singular stress is investigated. For PMMA, three stages of crack propagation are identified in terms of initial non-singular stress σ_ns0. When σ_ns0<60 MPa, the crack speed mm/s and the crack is basically stationary; when 60 <σ_ns0<95 MPa, then mm/s the crack is in slow propagation; when σ_ns0>95 MPa, then mm/s and the crack is in rapid propagation. The proposed model is applicable only in slow crack propagation.     

The investigation on the effect of surface radiation oxidation of bamboo fiber‐filled PMMA composite

The aim of this investigation was to study the effect of surface thermal oxidation of bamboo/poly(methyl methacrylate) composite by irradiation. Thermal oxidative effects on the surface energy of bamboo fiber were measured by radiation as a function of exposure time and temperature. Oxidized bamboo/poly(methyl methacrylate), after exposure to air at temperatures of 100°C and 110°C, had a range of maximum surface energies from 38 to 41 mJ/m². Comparisons between Fourier transform infrared carbonyl peak growth and the surface energy showed that both methods detect oxidation, though the increase in surface energy was detected before the carbonyl peak growth was noticeable. The work of adhesion predicted by the surface free energies obtained in this work between a coated calcium carbonate and bamboo fiber changes by 10% due to the oxidation of the polymer at 110°C. The structural results were discussed in the oxidation chemistry of the macromolecule.