47 lines
15 KiB
JSON
47 lines
15 KiB
JSON
[
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{
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"id": 1,
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"chunk": "# UV-Curable Anti-Fog 医 Coatings \n\nA t c ertain t emperature aand h um d ty, water vap or i n a ir c ondenses on s olid surfaces. Because water has much higher surface energy t han most solid surfaces, the c ondensed w ater u sually t akes t he form of s mall d roplets, which scatter light and cause haziness. Fogging is a severe problem for a lot of optical devices, such as lenses, m irrors, w indshields and visors et al. Basically, there are two ways to avoid hazy water condensation. One i s t o c ontrol t he t emperature a nd h umidity s o t hat water c ondensation c an n ot hap pen. F or exa mple, s ome devices use heating elements to keep the temperature high enough th at w ater c annot c ondense; s ome d evices a re purged by inert gases or dry air to remove moisture. These approaches are very effective, but consume energy and they are ex pensive. The ot her approach i s t o u se a nti-fog c oatings on t he optical devices. A nti-fog c oatings c an p revent hazy water condensation and maintain the optical clarity. Obviously, this is a better approach, because anti-fog coatings are cheaper and consume no energy to operate. Considering the anti-fog mechanism, it is possible to categorize anti-fog coatings into three types. \n\nType I: The coatings remove water condensation by absorbing liquid water into the coating. Type I c oatings can b e s aturated whe n moi sture lev el i s t oo h igh, a nd do not respond to water condensation quickly; therefore they are not very effective. \n\nType I I: The c oatings lo wer t he s urface e nergy of water, a nd the condensed water evenly wets the surface. Usually, Type II anti-fog coatings carry extractable surfactants.1 W hen wa ter co ndenses o n t he coa ting surface, t he s urfactants di ssolve in to t he li quid w ater and br ing down its surface energy so that water w ill wet the s urface ev enly. T ype I I c oatings w ork e ffectively a s long a s e nough s urfactants c an b e ex tracted i nto w ater; however, surfactants can be washed away by water, and Type II anti-fog coatings will lose their anti-fog property gradually. I n ad dition, b ecause it t akes t ime fo r w ater t o dissolve surfactants, Type II coatings will not respond to water condensation very quickly. When suddenly exposed to high humidity, some Type II coatings can immediately get fogged and it will take some time for them to turn clear. \n\nType I II: The se c oatings ha ve a s uper-hydrophilic surface. Water has a very low contact angle, less than $5^{\\circ}$ , on s uperhydrophilic s urfaces, a nd w ater c ondensed on a s uper-hydrophilic s urface w ill ev enly s pread ou t v ery quickly. No s urfactants ne ed t o b e ex tracted f rom t he super-hydro hilic coatings; t ey work instantly with little d lay ttime. Sup er-hydrophilic c oatings2 p erform b tter than the other two types of anti-fog coatings. \n\nIn this paper, we discuss UV-curable super-hydrophilic anti-fog c oatings. UV -curable an ti-fog c oatings3 c an b e cured i nstantaneously. They c onsume le ss e nergy t o produce and, more importantly, they can be produced in a roll-to-roll process at high speed.",
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"category": " Introduction"
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},
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{
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"id": 2,
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"chunk": "# Experimental \n\nSilica na noparticles, a s a 1 $\\ensuremath{\\mathrm{0-15}}\\ensuremath{\\mathrm{n~m~p~}}$ article s ize, $3\\:0\\%$ dispersion in m ethanol, w ere u sed e ither dir ectly wi thout modification o r w ere m odified b y p olyethylene g lycolmodified silane and acrylate/methacrylate-modified silanes.",
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"category": " Materials and methods"
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},
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{
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"id": 3,
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"chunk": "# Synthesis of Polyethylene Glycol-Modified Silane \n\nMonomethyl ether polyethylene glycol (mPEG) $(\\mathrm{Mw}=1100)$ ) was dissolved in toluene and the mixture was dried. At room temperature a nd u nder n itrogen, a mola r e quivalent (with respect to the mPEG) of 3-isocyantopropyl trimethoxysilane was added drop wise to the reaction mixture. A few d rops of dibutyl tin dilaurate were added as a c atalyst. The r eaction mixture w as t hen s tirred c ontinuously fo r $24\\mathrm{h}$ at $5\\ 0^{\\mathrm{{o}}}\\mathrm{{C}}$ . The r eaction w as mon itored by i nfrared s pectroscopy; the is ocyanate s ignal is a $\\mathrm{t}2271\\mathrm{cm}^{-1}$ . U pon c ompletion, approximately t wo t hirds of t he t oluene w as r emoved by rotary evap oration a nd t he m PEG t rimethoxysilane w as precipitated into hexane and washed several times. The resulting s olid w as d ried a nd cha racterized by 1 H N MR. Reaction yields of $>90\\%$ were obtained.",
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"category": " Materials and methods"
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},
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{
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"id": 4,
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"chunk": "# Silica Nanoparticle Surface Modification \n\nThe s urface of s ilica na noparticles w as f unctionalized with mPEG triethoxysilane and 3-(trimethoxysilyl)propyl \n\n \nFIGURE 1 | Polycarbonate sheet (left) and PET sheet (right) coated by a roll-to-roll process. \n\nTABLE 1 | Modification of silica nanoparticles. \n\n\n<html><body><table><tr><td rowspan=\"3\">Material</td><td colspan=\"2\">Modified Silicon Oxide Particle</td></tr><tr><td></td><td></td></tr><tr><td>A</td><td>B</td></tr><tr><td>Silicon oxide nanoparticles, 30% solid in methanol</td><td>29.0</td><td>28.8</td></tr><tr><td>3-(trimethoxysilyl)propyl acrylate</td><td>1.1</td><td></td></tr><tr><td>3-(trimethoxysilyl)propyl methacrylate</td><td></td><td>1.1</td></tr><tr><td>mPEG trimethoxysilane</td><td>2.1</td><td>3.0</td></tr><tr><td>Hydroquinone monoethyl ether</td><td>0.02</td><td>0.02</td></tr><tr><td>Methanol (solvent)</td><td>67.7</td><td>67.1</td></tr><tr><td>Total</td><td>100</td><td>100</td></tr></table></body></html> \n\nTABLE 2 | Anti-fog coating formulation. \n\n\n<html><body><table><tr><td rowspan=\"2\">Material</td><td colspan=\"4\">Formulation</td></tr><tr><td>C (%)</td><td>D (%)</td><td>E (%)</td><td>F (%)</td></tr><tr><td>Silicon oxide nanoparticle</td><td></td><td>20.4</td><td>-</td><td></td></tr><tr><td>Modified silicon oxide particle A</td><td>28.9</td><td>-</td><td>-</td><td>28.9</td></tr><tr><td>Modified silicon oxide particle B</td><td></td><td>-</td><td>29.7</td><td></td></tr><tr><td>PEG diacrylate</td><td>6.8</td><td>5.1</td><td></td><td>6.8</td></tr><tr><td>PEG dimethacrylate</td><td>-</td><td>-</td><td>7.0</td><td></td></tr><tr><td>Sulfo propyl acrylate potassium salt</td><td>0.3</td><td>0.2</td><td>-</td><td></td></tr><tr><td>Sulfo propyl methyacrylate potassium salt</td><td></td><td></td><td>0.3</td><td>-</td></tr><tr><td>Water</td><td>2.4</td><td>1.8</td><td>2.5</td><td>2.4</td></tr><tr><td>Irgacure184</td><td>0.4</td><td>0.3</td><td>0.3</td><td>0.4</td></tr><tr><td>Methanol (solvent)</td><td>61.3</td><td>72.2</td><td>60.4</td><td>61.6</td></tr><tr><td>Total</td><td>100</td><td>100</td><td>100</td><td>100</td></tr></table></body></html> \n\nTABLE 3 | Rating of anti-fogging performance. \n\n\n<html><body><table><tr><td>Antifogging Performance</td><td>Rating</td><td>Annotations</td></tr><tr><td>No</td><td>1</td><td>Zero visible, poor light transmission</td></tr><tr><td>No</td><td>2</td><td>Zero visible, poor light transmission</td></tr><tr><td>Poor</td><td>4</td><td>Poorvisible</td></tr><tr><td>Fair</td><td>6</td><td>Discontinuous film of water</td></tr><tr><td>Good</td><td>8</td><td>Discontinuous film of water, mostly transparent</td></tr><tr><td>Excellent</td><td>10</td><td>Completely transparent</td></tr></table></body></html> \n\nTABLE 4 | Performance of the anti-fog coatings. \n\n\n<html><body><table><tr><td rowspan=\"2\"></td><td colspan=\"2\">Anti-Fogging Rating</td></tr><tr><td>Before Water Wash</td><td>After Water Wash*</td></tr><tr><td>Formulation C</td><td>10</td><td>10</td></tr><tr><td>Formulation D</td><td>10</td><td>10</td></tr><tr><td>Formulation E</td><td>10</td><td>10</td></tr><tr><td>Formulation F</td><td>2</td><td>2</td></tr></table></body></html>\n\n\\* The coated samples were washed with water for 10 seconds. \n\nTABLE 5 | Properties of anti-fog coatings produced by roll-to-roll process. \n\n<html><body><table><tr><td>Properties</td><td>Value</td></tr><tr><td>Pencil hardness</td><td>H on PET, 2B on polycarbonate</td></tr><tr><td>Refractive index</td><td>1.48</td></tr><tr><td>Thickness</td><td>6 μm</td></tr><tr><td>Transmittance (%)</td><td>93.4</td></tr><tr><td>Clarity</td><td>99.8</td></tr><tr><td>Yellownessindex</td><td>No change from the uncoated substrate</td></tr><tr><td>Haze</td><td>0.27</td></tr><tr><td>Steelwoolabrasion*△Haze</td><td>1.87</td></tr></table></body></html>\n\n$\\ast_{250~9}$ load, #0000 steel wool, 10 double rub, and then measure haze value \n\nacrylate or 3- (trimethoxysilyl)propyl methacrylate. Table 1 sho ws t he a mount of e ach c omponent u sed i n t he reaction. The m ixtures were stirred at r oom temperature overnight to finish the reaction.",
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"category": " Materials and methods"
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},
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"id": 5,
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"chunk": "# Coating Formulation \n\nFormulations were prepared by mixing modified or unmodified s ilicon o xide na noparticles w ith r eactive diluents, polyethylene glycol diacrylate $\\mathrm{(Mw=575~g~moF^{1}}$ ), sulfopropyl ac rylate p otassium salt, a nd a phot oinitiator, 1-hydroxycyclohexyl b enzophenone. The s ulfopropyl acrylate potassium salt was added as a s olution in water. The exact weights used for coatings are shown in Table 2. All the liquid coatings have a solid content of about $12\\%$ . \n\nCoatings were applied on PE T or p olycarbonate she ets using # 16 w ire w ound r od. The c oatings w ere d ried for ha lf a m inute, a nd t hen c ured u nder a $3\\ \\mathrm{~00~W~p~}$ er inch me rcury vap or la mp at a do se of 1 J/ $\\mathrm{cm}^{2}$ in a nitrogen at mosphere. The t hicknesses of t he c ured coatings were ab out $5\\mathrm{m}$ icrometers. The c oated s amples were cha racterized by c ross-hatch ad hesion t est, p encil hardness, optical properties and steel wool scratch test.",
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"category": " Materials and methods"
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},
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"id": 6,
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"chunk": "# Results and Discussion \n\nAll c ured c oatings ha ve $100\\%$ ad hesion on t reated PE T and polycarbonate substrate, $99\\%$ optical clarity and over $90\\%$ transmittance. The anti-fog properties of the coatings were t ested by hold ing a c oated substrate for 15 seconds above warm water at $50^{\\circ}\\mathrm{C}$ . The c oating p erformance i s rated to the degree of fogging/transparency. If the coating fogs c ompletely, ha ving n o t ransparency, it i s rat ed a s 1. I f t he c oating do es n ot fog at a ll, s taying c ompletely transparent, it is rated as 10. A complete description of the rating and degree of fogging is given in Table 3. \n\nAnti-fog p erformance o f c oatings i s li sted in T able 4. A ll t he c oatings w ith t he s ulfonate s alt ha ve p erfect anti-fog p roperties; t he c oating w ithout s ulfonate s alt has p oor an ti-fog p roperties. Typ ically, i onic gr oups are mo re h ydrophilic t han e thylene g lycol g roups, a nd that is p robably th e r eason th at c oatings c ontaining sulfonate s alt h ave b etter p erformance in t he f ogging test. B ecause a ll t he c omponents a re c rosslinked i nto a p olymer ne twork, a fter t he c oatings w ere w ashed by water t heir a nti-fog p erformance d id n ot cha nge. It a lso has n o e ffect on a nti-fog p erformance whe ther ac rylates or met hacrylates w ere u sed. H owever, met hyacrylates polymerize much slower than acrylates. When coating E i s cured i n a ir, t he c oating i s very t acky b ecause of t he oxygen inhibition. There is no obvious difference between coating C and coating E, when they are cured in nitrogen. \n\nThe mo dification of s ilica na noparticles ha s n o e ffect on a nti-fog p erformance of t he c oatings. B ecause t he modified s ilica n anoparticles ar e c ovalently link ed in to the p olymer ne twork, t he mo dified s ilica na noparticles should g ive t he c oating b etter s cratch r esistance. Si nce silica nanoparticles without modification can already give good mechanical properties, surface modification of silica nanoparticles is not always necessary. \n\nThe c oating w ith n on-modified s ilica p articles w as applied by a roller coater on flexible PET and polycarbonate sheet. The c oating w as ap plied a nd c ured c ontinuously at $5\\mathrm{m}$ /min i n a r oll-to-roll p rocess. A s sho wn i n T able 5 a nd Figure 1 , t he c oated t ransparent she ets ha ve g ood op tical a nd mechanical properties and uniform thickness. \n\n \n\nAnti-fog coatings were also tested at both high and low temperatures, a nd t hey w orked v ery w ell b etween - $20~^{\\mathrm{o}}\\mathrm{C}$ and $90^{\\mathrm{{o}}}\\mathrm{{c}}$ . A s sho wn i n F igure 2 , a p iece of $\\mathrm{\\Deltap}$ artially c oated polycarbonate plat e w as plac ed on a c up of $90^{\\mathrm{{o}}}\\mathrm{{C}}$ c offee. The plate w as i nitially at r oom t emperature. Whe n it w as ex posed to the moisture from $90~^{\\mathrm{~o~c~}}$ coffee, the uncoated area was immediately fogged, while the coated area always stayed clear. In t he lo w-temperature t est, t he c oated s amples w ere c ooled down t o - $20^{\\mathrm{o}}\\mathrm{C}$ , a nd t hen w ere ex posed t o $60\\%$ h umidity room temperature air. The coated area stayed clear, while the uncoated area was quickly fogged.",
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"category": " Results and discussion"
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"id": 7,
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"chunk": "# Conclusion \n\nUV-curable anti-fog coatings were developed. The coatings comprise i norganic na noparticles a nd U V-curable h ydrophilic materials. The c oatings c an p revent fogg ing at t emperatures between $-20{}^{\\mathrm{o}}\\mathrm{C}$ a nd $90^{\\mathrm{{o}}}\\mathrm{{c}}$ . The c oatings sho w exc ellent op tical clarity, good hardness and scratch resistance. \u0002",
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"category": " Conclusions"
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},
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"id": 8,
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"chunk": "# References \n\n1 Radisch, Helmer; Scholz, Werner. US Patent, 4,609,688. 2 Cebeci, F .Ç.; W u, Z .; Z hai, L .; C ohen, R .E.; R ubner, M .F. Langmuir 2006, 22, 2856-2862. 3 Meijers, Guido, Thies, Jens Christoph; Nijenhuis, Atze Jan. International Patent Application, 2009, WO 2009/118415. \n\nThis p aper w as p resented a t t he R adTech 20 10 T echnology E xpo a nd Co nference, Baltimore, MD, www.radtech.org. \n\n",
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"category": " References"
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},
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{
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"id": 9,
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"chunk": "# Elcometer 456 Coating Thickness Gauge. One gauge–A world full of applications. \n\nThe key to the superiority of the 456 is its measurement system featuring a range of interchangeable probes \n\nAll Ferrous models will accept ANY Ferrous 456 probe \nAll Non-Ferrous models will accept ANY Non-Ferrous 456 probe \nAll Dual FNF models will accept ANY 456 probe High speed accurate readings Three memory options–Basic, Standard,Top Easy to use menu driven display-available in 22 languages Standard and pre-defined calibration options \nIntegral and separate probe options \n\nUS & Canada 800.521.0635 $\\cdot$ www.elcometer.com \n\nCopyright of Paint & Coatings Industry is the property of BNP Media and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use.",
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"category": " Materials and methods"
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}
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] |