Polyurethane based anti-graffiti coatings have been developed by incorporating varying amounts of OH-functional Silicone modified polyacrylate. Optimization of Silicone polyacrylate concentration in neat PU was done b...Polyurethane based anti-graffiti coatings have been developed by incorporating varying amounts of OH-functional Silicone modified polyacrylate. Optimization of Silicone polyacrylate concentration in neat PU was done by testing its performance for graffiti resistance. Tests which include static contact angle measurements with water and spray paint, visual inspection of stain removal and color change measurements were performed. It was observed that 5 wt % of Silicone polyacrylate in the neat PU showed 95% stain removability. These coatings showed excellent graffiti resistance but poor mechanical properties. Hence modification of these coatings was done by nano-particle incorporation. Nano-silica particle concentration was optimized for surface mechanical properties such as surface hardness, elastic modulus and scratch resistance. FEG-TEM revealed that nano-silica particles were uniformly distributed over the surface. 5 wt % nano-silica particle additions in PU-5 wt % silicone polyacrylate base showed superior mechanical properties than other concentrations. Color change measurements showed that nano-silica particle addition had no effect on its graffiti resistance. Hence PU-5 wt % silicone polyacrylate, 5 wt % nano-silica showed excellent graffiti resistance and mechanical properties.展开更多
The hardness, elastic modulus, nano-scratch resistance and wear depth for a bulk metallic glass of and its partial crystallization alloys have been measured by using nanoindentation method. The results showed that par...The hardness, elastic modulus, nano-scratch resistance and wear depth for a bulk metallic glass of and its partial crystallization alloys have been measured by using nanoindentation method. The results showed that partial crystallization did not influence the reduced elastic modulus but increased the hardness, and then increased the scratch coefficient. The scratch coefficient increased linearly with increasing the hardness H but decreases when W>6.2GPa. Partial crystallization decreased evidently the wear depth, and when the load was large the wear depth decreased with increasing the hardness.展开更多
The previous research of precision grinding optical glasses with electrolytic in process dressing （ELID） technology mainly concentrated on the action of ELID and machining parameters when grinding, which aim at gene...The previous research of precision grinding optical glasses with electrolytic in process dressing （ELID） technology mainly concentrated on the action of ELID and machining parameters when grinding, which aim at generating very ＂smoothed＂ surfaces and reducing the subsurface damage. However, when grinding spectrosil 2000 and BK7 glass assisted with ELID technology, a deeply comparative study on material removal mechanism and the wheel wear behaviors have not been given yet. In this paper, the micro/nano indentation technique is initially applied for investigating the mechanical properties of optical glasses, whose results are then refereed to evaluate the machinability. In single grit diamond scratching on glasses, the scratching traces display four kinds of scratch characteristics according to different material removal modes. In normal grinding experiments, the result shows BK7 glass has a better machinability than that of spectrosil 2000, corresponding to what the micro/nano indentation vent revealed. Under the same grinding depth parameters, the smaller amplitude of acoustic emission （AE） raw signals, grinding force and grinding force ratio correspond to a better surface quality. While for these two kinds of glasses, with the increasing of grinding depth, the variation trends of the surface roughness, the force ratio, and the AE raw signals are contrary, which should be attributed to different material removal modes. Moreover, the SEM micrographs of used wheels surface indicate that diamond grains on the wheel surface after grinding BK7 glass are worn more severely than that of spectrosil 2000. The proposed research analyzes what happened in the grinding process with different material removal patterns, which can provide a basis for producing high-quality optical glasses and comprehensively evaluate the surface and subsurface integrity of optical glasses.展开更多
In the present investigation, the effect of two different mineral nano clays and a synthetic nano layered silicate on the properties of a transparent polyurethane resin has been studied. Both high rotator Torusmill an...In the present investigation, the effect of two different mineral nano clays and a synthetic nano layered silicate on the properties of a transparent polyurethane resin has been studied. Both high rotator Torusmill and high intensity ultrasonic deagglomerator are utilized for the dispersion process. Observations by means of the X-ray diffraction technique indicate the presence of different dispersion status of nano layers in polymer matrix. The optical effect of nano-filled clear coat was studied using goniospectrophotometer and compared with a blank clear coat to determine if it can be identified by human eye. Scratch and mar resistance tests presented considerable improvement. Gloss retention against rubbing increased significantly in the presence of merely 3 wt% of synthetic nano-filler.展开更多
文摘Polyurethane based anti-graffiti coatings have been developed by incorporating varying amounts of OH-functional Silicone modified polyacrylate. Optimization of Silicone polyacrylate concentration in neat PU was done by testing its performance for graffiti resistance. Tests which include static contact angle measurements with water and spray paint, visual inspection of stain removal and color change measurements were performed. It was observed that 5 wt % of Silicone polyacrylate in the neat PU showed 95% stain removability. These coatings showed excellent graffiti resistance but poor mechanical properties. Hence modification of these coatings was done by nano-particle incorporation. Nano-silica particle concentration was optimized for surface mechanical properties such as surface hardness, elastic modulus and scratch resistance. FEG-TEM revealed that nano-silica particles were uniformly distributed over the surface. 5 wt % nano-silica particle additions in PU-5 wt % silicone polyacrylate base showed superior mechanical properties than other concentrations. Color change measurements showed that nano-silica particle addition had no effect on its graffiti resistance. Hence PU-5 wt % silicone polyacrylate, 5 wt % nano-silica showed excellent graffiti resistance and mechanical properties.
基金support by the special funds for the major state basic research(2002AA331080).
文摘The hardness, elastic modulus, nano-scratch resistance and wear depth for a bulk metallic glass of and its partial crystallization alloys have been measured by using nanoindentation method. The results showed that partial crystallization did not influence the reduced elastic modulus but increased the hardness, and then increased the scratch coefficient. The scratch coefficient increased linearly with increasing the hardness H but decreases when W>6.2GPa. Partial crystallization decreased evidently the wear depth, and when the load was large the wear depth decreased with increasing the hardness.
基金supported by National Key Science and Technology Projects of China (Grant No. 2009ZX04001-101, Grant No. 2009ZX01001-151)New Century Excellent Talents in University of China (Grant No. NCET-07-0246)Pre-Research Project of General Armament Department of China (Grant No. 9140A18070209HT0138)
文摘The previous research of precision grinding optical glasses with electrolytic in process dressing （ELID） technology mainly concentrated on the action of ELID and machining parameters when grinding, which aim at generating very ＂smoothed＂ surfaces and reducing the subsurface damage. However, when grinding spectrosil 2000 and BK7 glass assisted with ELID technology, a deeply comparative study on material removal mechanism and the wheel wear behaviors have not been given yet. In this paper, the micro/nano indentation technique is initially applied for investigating the mechanical properties of optical glasses, whose results are then refereed to evaluate the machinability. In single grit diamond scratching on glasses, the scratching traces display four kinds of scratch characteristics according to different material removal modes. In normal grinding experiments, the result shows BK7 glass has a better machinability than that of spectrosil 2000, corresponding to what the micro/nano indentation vent revealed. Under the same grinding depth parameters, the smaller amplitude of acoustic emission （AE） raw signals, grinding force and grinding force ratio correspond to a better surface quality. While for these two kinds of glasses, with the increasing of grinding depth, the variation trends of the surface roughness, the force ratio, and the AE raw signals are contrary, which should be attributed to different material removal modes. Moreover, the SEM micrographs of used wheels surface indicate that diamond grains on the wheel surface after grinding BK7 glass are worn more severely than that of spectrosil 2000. The proposed research analyzes what happened in the grinding process with different material removal patterns, which can provide a basis for producing high-quality optical glasses and comprehensively evaluate the surface and subsurface integrity of optical glasses.
文摘In the present investigation, the effect of two different mineral nano clays and a synthetic nano layered silicate on the properties of a transparent polyurethane resin has been studied. Both high rotator Torusmill and high intensity ultrasonic deagglomerator are utilized for the dispersion process. Observations by means of the X-ray diffraction technique indicate the presence of different dispersion status of nano layers in polymer matrix. The optical effect of nano-filled clear coat was studied using goniospectrophotometer and compared with a blank clear coat to determine if it can be identified by human eye. Scratch and mar resistance tests presented considerable improvement. Gloss retention against rubbing increased significantly in the presence of merely 3 wt% of synthetic nano-filler.
