1、Designation: C912 17Standard Practice forDesigning a Process for Cleaning Technical Glasses1This standard is issued under the fixed designation C912; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A numb
2、er in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This practice covers information that will permit designof a rational cleaning procedure that can be used with a glassthat is somewhat solu
3、ble in many aqueous chemical solutions.Typically, this type of glass is used in applications such asoptical ware, glass-to-metal seals, low dielectric loss products,glass fibers, infrared transmitting products, and products resis-tant to metallic vapors.1.2 In most cases, this type of glass contains
4、 high concen-trations of oxides that tend to react with a number of aqueouschemicals. Such oxides include B2O3,Al2O3,R2O, RO, La2O3,ZnO, PbO, P2O5, and Fe2O3. The more conventional high-silica glasses are usually more chemically resistant, but thecleaning principles outlined here also apply to them.
5、1.3 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety, health, and environmental practices and deter-mine the applicability of regulatory limitations prior to use
6、.Specific hazard statements are given in Section 4 and Table 1.1.4 This international standard was developed in accor-dance with internationally recognized principles on standard-ization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recom-mendati
7、ons issued by the World Trade Organization TechnicalBarriers to Trade (TBT) Committee.2. Terminology2.1 Definitions of Terms Specific to This Standard:2.1.1 technical glass, nglasses designed with some spe-cific property essential for a mechanical, industrial, or scientificdevice.3. Significance and
8、 Use3.1 Many of the low-silica technical glasses which containsoluble or reactive oxides require processing or involve appli-cations that require cleaning. Very often these cleaning proce-dures have evolved over several decades and are considered anart. They usually contain numerous steps, some of q
9、uestionablevalidity. It is the premise of this practice that cleaning glass canbe more scientific. Design of a cleaning procedure shouldinvolve (1) a definition of the soil to be removed, (2)anawareness of the constraints imposed by the glass composition,and (3) a rational selection of alternative m
10、ethods that willremove the soil and leave the glass in a condition suitable forits intended application. This practice provides information toassist in step (3). General references on glass cleaning and onvarious methods of evaluating cleanliness and associatedinformation has been published.24. Haza
11、rds4.1 Many of the chemicals that can be used in cleaning glassare hazardous. This is true of most of the aqueous chemicalsdiscussed in Section 5 and shown in Table 1 as well as theorganic chemicals discussed in Section 6.4.2 Special care should be used with hydrofluoric acid (HF),which will react w
12、ith glass generating heat. HF destroysdermal tissue and exposure of the skin to the liquid orinhalation of the vapors can be fatal.4.3 Concentrated acids can react violently if water is addedinto them. When it is necessary to dilute acid, add the acid tothe water slowly and with constant stirring so
13、 that heat is neverallowed to concentrate locally in the solution.4.4 Organic solvents may be flammable or toxic, or both.Threshold limit values for some common solvents are shown inTable 2. Note that the fluorocarbons are most likely to exhibittoxic effects as a result of inhalation or skin absorpt
14、ion.Benzene is not recommended as a solvent since it is a knowncarcinogen.5. Aqueous Solvents5.1 SelectionIn using aqueous solvents for cleaning, gen-erally two extreme choices are available. One is to select anaqueous system that dissolves the soil to be removed, but haslittle effect on the glass.
15、The other is to select a system thatdissolves the glass uniformly, thus undercutting the soil andleaving a chemically polished glass surface. It is best to avoid1This practice is under the jurisdiction of ASTM Committee C14 on Glass andGlass Products and is the direct responsibility of Subcommittee
16、C14.02 on ChemicalProperties and Analysis.Current edition approved Nov. 1, 2017. Published November 2017. Originallyapproved in 1979. Last previous edition approved in 2013 as C912 93 (2013).DOI: 10.1520/C912-17.2Campbell, D. E., and Adams, P. B., “Bibliography on Clean Glass: Supplement1,” Journal
17、of Testing and Evaluation, Vol 14, No. 5, September 1986, pp. 260265.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United StatesThis international standard was developed in accordance with internationally recognized principles on standardization
18、established in the Decision on Principles for theDevelopment of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.1TABLE 1 Relative Solubility of Various Glass Component Oxides in HF, Other Inorganic Acids, and NaOH
19、, in Concentrated Solutions atRoom TemperatureNOTE 1Macro or minor/trace levels will determine degree of precipitation, especially in acids, for example, HNO3(Sn, Sb, Mo).NOTE 2W is soluble in acid but heat may precipitate it, for example, H2WO4.NOTE 3Sn+4is soluble in hot H2SO4;Sn+2is soluble in ot
20、her reagents as well.NOTE 4Most alkali solutions must be hot to effect solution.NOTE 5PbSO4is soluble in hot concentrated H2SO4.NOTE 6Sb and Bi form insoluble oxychlorides in dilute HCl.NOTE 7Ba is insoluble in concentrated HNO3.Oxides ofHF49 %H2SO496 %HNO370 %HCl37 %HBr HIH3PO485 %NaOH50 %Al sAs ss
21、iiisSb iAi i sssiAs sssssBa se s s ssssiiB s sssssCd s sa ie i iiiiiCr io s s s ssssiuEr is s ssssiGda se s s sssssAu i i i iiiiiHf sFe s s ssssiLa iPb i iiissi s s s sssssMg i ssssinMo s s iBsssssNd i s ssssiib s i i iiiiiPd ss ssssst i i i iiiiiK s sPr s ssssim iRh sb s ssssiu iSm se s s sssssi i
22、i iiiisAg s iiisiNa s s sssssSr i i i iiiiiTe s s s sssssTl s s s s i i s iTh s sBi iiiiiSn sssssTi s sBsiiiiW i i iiiisU siiiiiV s s sssssYb i ssssisZn s s sssssZr s sBi iiiiiAs = relatively soluble, i = relatively insoluble.BhotC912 172a solvent that selectively attacks the glass, dissolving onlys
23、ome components, or a solvent that produces a precipitate thatadheres to the surface to be cleaned.5.2 Minimum Glass Dissolution:5.2.1 Water is the most frequently used aqueous solvent.Even this can attack some glasses appreciably.5.2.2 Try to choose an aqueous system that completelyremoves the soil
24、with minimal effect on the underlying glass.Obviously, to achieve this the glass composition must beknown. However, one cannot simply calculate glass solubilityin a specific reagent. Reference to Table 1 will then helpdetermine if an aqueous solvent exists that will not attack theglass. The table pr
25、ovides guidance in selecting a solvent, buttrial and error will usually be necessary also. Individual glasscomponents do not act independently with specific solvents, inmost cases, as described in 5.2.3.5.2.3 It is not necessary that the glass contain absolutelynone of the components that are solubl
26、e in the chosen reagent.For instance, a glass containing 80 % SiO2and 5 % Na2Ocould be cleaned in H2SO4without appreciable glass attackeven though Na2O is very soluble in H2SO4; however a glasscontaining 50 % SiO2and 25 % Na2O would probably showconsiderable attack by H2SO4. Often this can only be d
27、eter-mined by trial.5.3 Uniform Glass Dissolution:5.3.1 It may be necessary to select a system that uniformlyattacks the glass either because there is no other solvent for thesoil or there is no solvent available that does not attack theglass. For glasses containing substantial concentrations ofsili
28、ca, HF or HF plus some other reagent may be a good choice.HF can often be used for cleaning provided there are no glasscomponents that form insoluble fluorides. For non-silicateglasses, some other reagent would probably be appropriate.Table 1 is a general guide to selection of such reagents.5.3.2 Th
29、ere are two further modifications that can allow thesuccessful use of HF even if insoluble products form. One is tocombine chemical cleaning with a mechanical cleaning processeither simultaneously or sequentially. The other is to mix theHF with another acid to achieve complete solution of allproduct
30、s.5.3.3 Alkali solutions can be used as a glass solvent forcleaning, but, in most cases, it will be necessary to use themhot to achieve a sufficiently rapid reaction.5.3.4 Many glasses can be cleaned by the uniform dissolu-tion process without the use of HF or alkali. Reference to Table1 will sugges
31、t the types of glasses to which this approach isapplicable. For instance, a glass containing 60 % PbO and lessthan 15 % SiO2could probably be cleaned in this way withHNO3, particularly if mechanical action by polishing orrubbing is used.5.4 Other Possibilities:5.4.1 When all else fails, organic comp
32、lexing agents, eitheralone or in combination with other chemicals, may succeed inremoving soil without damaging the glass. For instance,alkaline EDTAis a powerful complexing agent for a number ofelements, such as calcium, magnesium, silicon, aluminum,lead, zinc, and barium.5.4.2 Sometimes it is nece
33、ssary to use a multicomponentaqueous system to achieve the desired results. Obviously,concentrations of various reagents and temperatures at whichthe process can be carried out are important. It is not the intentof this practice to explore all these possibilities, but, byknowing the glass compositio
34、n, the correct solvent-concentration-temperature-time conditions to affect the desiredresult can be devised.5.5 Residues and Defects:5.5.1 Any reaction between a solvent and a complex mix-ture of oxides affects the possibility of formation of someinsoluble reaction products. Agitation may help preve
35、nt theiradherence to the glass. Additionally, the reagent itself ispotentially a “residue.”5.5.2 Reaction with the glass may also leave a roughenedsurface (selective reaction with certain glass components),streaks (selective reaction with nonhomogeneous “cords”), orwith latent grinding marks hidden
36、by a previous polishing step.6. Detergents6.1 Surface Active Agents:6.1.1 Surface active agents accelerate the cleaning action ofaqueous solutions and provide mechanisms of cleaning thatwater does not have by itself. Many compounds are available,usually under trade names that give no hint of their c
37、hemicalnature. Selection of the best compound for a particular use isusually a matter of experimentation, since the available litera-ture gives few clues to aid in prediction.6.1.2 Generally, however, such “agents” consist of long-chain organic molecules, one end of which is attracted to thesoil or
38、the substrate, or both, the other end of which is “watersoluble.” They “wet” the glass surface by lowering the surfacetension of water; thus decreasing the contact angle betweensolvent and glass and between solvent and soil. The net effectis that the particle or oily film is dislodged. They “surroun
39、d”the particle or droplet to suspend or emulsify and prevent itsredeposition.6.1.3 The activity of surface active agents is usually en-hanced by the blending of two or more and by the addition ofnon-surface active agents (called “builders”). A compoundwith good emulsification will be blended with a
40、good wetter,and built with a polyphosphate for water softening, dispersion,and micelle formation. EDTA and similar compounds are usedfor water softening and solubilizing of inorganic compounds,TABLE 2 Threshold Limit Values for Some Common SolventsSolvent TLV, ppmA1,1,2-trichloro-1,2-trifluorethane
41、1000Acetone 500Ethyl alcohol 1000n-Hexane 20Isopropyl alcohol 400Methyl chloroform 2Perchloroethylene 50Trichloroethylene 50Methylene chloride 50Carbon tetrachloride 0.1AThe TWA values establish parts per million by volume of solvent vapors allowedin air for a normal work week of8haday,5days a week.
42、 These are standards setby the Ministry of Business, Innovation and Employment, and the values shown inthis table were effective February 2013, 7thEdition. Published by the Ministry ofBusiness, Innovation and Employment, P.O. Box 3705, Wellington, NZ 6011.C912 173soda ash, and ammonia for pH regulat
43、ion and sodium silicatesfor achieving high alkalinity while inhibiting attack on theglass.6.1.4 The builders can either promote or inhibit solution ofglasses, depending on whether the reaction products or thebuilder and the glass components are soluble or insoluble.Polyphosphates and EDTA, in partic
44、ular, will chelate with andsolubilize metallic ions, promoting a preferential leaching andleaving a porous or etched surface on the glass.6.1.5 Water-soluble surface active agents are usually long-chain organic molecules with a hydrophobic end and a hydro-philic end. The ionic nature of the hydrophi
45、lic end determinesthe broad basic classification of the materialif negative, it isanionic, if positive, cationic, and if the material is not ionized,it is nonionic. There are a few amphoteric materials available,and these hybrids can be either cationic or anionic, dependingon the pH of the solution.
46、6.2 Anionic AgentsThe oldest, and one of the most effec-tive anionic detergents if used in “soft” water, is soap. Thelargest class of synthetic anionic detergents is the sulfonatedhydrocarbons such as sodium dodecyl benzene sulfonate.Sulfated alcohols and polyethers, such as sodium lauryl sulfate,ar
47、e also used extensively.6.3 Cationic AgentsThe cationic detergents are usuallyquaternary ammonium salts. The classic cation active surfaceactive agent has an aryl group, a long-chain alkyl group, andtwo methyl groups bonded to the nitrogen atom. The cationicsare not usually found in glass-cleaning d
48、etergents, probablybecause they might be adsorbed, causing difficulty in rinsing.6.4 Nonionic AgentsThe nonionics are usually producedby ethoxylating various base molecules with ethylene oxide.The ethylene oxide adduct of nonyl or isooctyl phenol is themost popular of these. Water solubility, oil so
49、lubility,detergency, surface tension reduction, and other characteristicscan be adjusted by the length of the ethoxy chain, which is atthe hydrophilic end of the molecule.6.5 Amphoteric CompoundsThe amphoterics are usuallyamine sulfonates, and have not had as broad use as the anionicsand nonionics, probably because of the greater cost of produc-ing them.6.6 Other AdditivesAdditives that enhance the cleaningaction of organic solvents have not received as much attentionas water-soluble additives. The dry cleaning industry usescoupling agents and water-in-oil emulsifier
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