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Preparation and surface modification of magnetic poly(methyl methacrylate) microspheres

Science China Chemistry 2004年第4期47卷 349-354页

作者： YANG Chengli GUAN Yueping XING Jianmin LIU Junguo AN Zhentao LIU Huizhou Laboratory of Separation Science and Engineering State Key Laboratory of Biochemical Engineering Institute of Process EngineeringChinese Academy of Sciences Beijing 100080 China

A novel method for preparation of magnetic polymer microspheres by spraying suspension polymerization (SSP) was developed. Relatively uniform magnetic poly(methyl methacrylate) microspheres were prepared by the spraying suspension polymerization (SSP) using methyl methacrylate (MMA) as monomer, divinylbenzene (DVB) as cross-linking agent, benzoyl peroxide (BPO) as initiator and polyvinyl alcohol (PVA) as stabilizer in the presence of hydrophobic Fe3O4 magnetic fluid. The microspheres prepared were modified by surface chemical reaction. The magnetic properties and morphology of the microspheres were examined by SEM and VSM respectively. The active functional groups of microspheres were examined by infrared spectra. The results showed that microspheres with saturation magnetization of 16.8 emu/g showed distinct superparamagnetic characteristics and the magnetic microspheres with a size of 10 μm were relatively uniform.

关键词： methylmethacrylate superparamagnetic spraying suspension polymerization surface modification preparation characterization

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A Comparative Assessment of the Surface Roughness of Thermoplastic Denture Base Resins Following Adjustment and Re-Polishing

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Open Journal of Stomatology 2017年第4期7卷 250-263页

作者： Shivaughn M. Marchan Anna Kay Bishop William A. J. Smith Paul Seerattan David Hinds Unit of Restorative Dentistry School of Dentistry Faculty of Medical Sciences The University of the West Indies St Augus-tine Trinidad and Tobago School of Dentistry Faculty of Medical Sciences the University of the West Indies St Augustine Trinidad and Tobago Department of Physics Faculty of Science and Technology the University of the West Indies St Augustine Trinidad and Tobago

Purpose: This study assessed the roughness of two injection-molded, thermoplastic materials used for denture bases compared with a polyamide material and compression molded Polymethylmethacrylate (PMMA) after the adjustment and re-polishing with either a laboratory protocol or a chair side protocol. Methods: Forty specimens, each of PMMA, Valplast, DuraFlex, Dura Cetal were fabricated and finished according to individual manufactures’ instructions. These materials were adjusted with tungsten carbide (TC) burs to mimic gross adjustments, and then re-polished either on a lathe or bonded silicon carbide (B-SC). Following instrumentation, the specimens were assessed using contact profilometry and scanning electron microscopy. Two-factor ANOVA was used to determine significant differences in mean surface roughness (Ra and Rmax), with included factors being material type and re-polishing regimen. Results: Mean Ra values ranged from 0.26 (DuraFlex control) to 1.82 (Valplast adjusted with TC burs). Mean Rmax values ranged from 1.88 (Dura Flex control) to 13.76 (Valplast adjusted with TC burs). Two-factor ANOVA revealed that interaction of both factors was significant (p Ra and Rmax. There was a statistically significant increase in both Ra (p Rmax (p < 0.05) for all material types following the gross adjustment. With the exception of DuraFlex, re-polishing of samples that were previously adjusted with TC burs, on the dental lathe produced surfaces that were comparable to control samples. Conclusion: Adjustment of DuraFlex should be kept to a minimum since the adjustment produced the significant surface detriment that could not be corrected with either of the polishing regimens.

关键词： DuraFlex DuraCetal Valplast Poly methylmethacrylate Surface Roughness

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