A novel and general method of modifying hydrophobic polysulfone (PSF) to produce highly hydrophilic surfaces was developed. This method is the low‐temperature plasma technique. Graft polymer‐modified surfaces were characterized with the help of Fourier transform infrared attenuated total reflection (FTIR–ATR) and X‐ray photoelectron spectroscopy (XPS). Study results demonstrated that poly(ethylene glycol) (PEG) could be grafted onto the PSF membrane surface by low‐temperature plasma. The hydrophilic character of the modified surfaces was increased in comparison with that of the parent membrane. The contact angle for a modified PSF membrane was reduced apparently. We analyzed the effectiveness of this approach as a function of plasma operating variables including plasma treatment power and treatment time. Hence, plasma‐induced graft polymer modification of membranes can be used to adjust membrane performance by simultaneously controlling the surface hydrophilicity and hemocompatibility. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 979–985, 2000
SUMMARY Objectives To investigate the influence of various factors on air-turbine handpiece bearing failure through developing standard protocols for testing the bearing longevity. Methods Groups of four air-turbine assemblies (Synea TA-98, W&H, Dentalwerk, Bürmoos, Austria) were subjected repeatedly to a full binary combinatorial set of operating conditions: with and without lubrication, simulated clinical loading, and corrosion protection, all with autoclaving, to the point of failure. A control set was lubricated only. Lubrication (Assistina, W&H), autoclaving (ST-Im30b, Eschmann Bros & Walsh, West Sussex, England), simulated clinical loading (0.56 N at 45° to the turbine axis, after autoclaving), and corrosion protection during autoclaving (magnesium sacrificial anode) were used as required. Free-running speed (Hz) and bearing resistance (μNm) were determined (Darvell-Dyson testing machine) at baseline and after every 10 cycles until turbine failure. Three-way analysis of variance (lubrication × loading × corrosion protection) of log(cycles to failure), with α = 0.05, was used. Results All autoclaved turbines had failed by 560 cycles, while the controls failed at 960-1000 cycles. All three main effects were significant: loading (p<10−6), lubrication (p<0.0002), and corrosion protection (p<0.02), as was the interaction lubrication × loading (p<10−6). No other interaction attained significance. Conclusions Running under load was the most important factor affecting bearing longevity. While autoclaving clearly has a detrimental effect, lubrication effectively increases longevity. A sacrificial anode may be economically worthwhile to extend life further, but low-load usage patterns, as generally instructed, are confirmed as beneficial.
Polypropylene (PP) is considered a competitive candidate to replace widely used cross-linked polyethene (XLPE) in cable material application, as it can potentially withstand higher operating temperature and has excellent electrical properties. Besides, it is a more environment-friendly material, since PP does not require crosslinking and, therefore, can be easily recycled at the end of its life. This paper investigated the influence on the tensile strength, space charge and breakdown behaviours of the PP by adding polyolefin elastomer (POE) and Magnesium Oxide (MgO) nanoparticles. 10 or 20 wt. % of POE and 5 or 10 wt. % of nano-MgO were introduced into PP. Results show that the PP with 10 wt. % of PE02 and 5 wt. % of surface treated-MgO has the highest breakdown strength among all systems. Also, the introduction of POE and nano-MgO can significantly improve the mechanical flexibility. In combination with the observed suppression of space charge accumulation, which shows that PP/POE/MgO nanocomposites are a viable option for high voltage (HV) cable insulation material in the future.
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