1、Designation: C 912 93 (Reapproved 2003)Standard Practice forDesigning a Process for Cleaning Technical Glasses1This standard is issued under the fixed designation C 912; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of l
2、ast revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) 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 glass
3、that is somewhat soluble 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 t
4、ype of glass contains 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 her
5、e also apply to them.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 and health practices and determine the applica-bility of regulatory limitations prior t
6、o use. Specific hazardstatements are given in Section 4 and Table 1.2. Terminology2.1 Definitions of Terms Specific to This Standard:2.1.1 technical glassglasses designed with some specificproperty essential for a mechanical, industrial, or scientificdevice.3. Significance and Use3.1 Many of the low
7、-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 questionablevalidity. It
8、 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 methods that willremove
9、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. Hazards4.1 Many of the chem
10、icals 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 6.34.2 Special care should be used with hydrofluoric acid (HF),which will react with glass generating h
11、eat. The vapors as wellas the liquid destroy dermal tissue and can be fatal if inhaled.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 that heat is neverallowed to concentrate lo
12、cally 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 absorption.Benzene is not recommended as a solvent
13、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. The other is to select a system thatdissolve
14、s the glass uniformly, thus undercutting the soil andleaving a chemically polished glass surface. It is best to avoida solvent that selectively attacks the glass, dissolving onlysome components, or a solvent that produces a precipitate thatadheres to the surface to be cleaned.5.2 Minimum Glass Disso
15、lution: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 with minimal effect on the underlying glass.1This practice is under the jurisdiction of ASTM Committee C14 on Glass andGl
16、ass Products and is the direct responsibility of Subcommittee C14.02 on ChemicalProperties and Analysis.Current edition approved Oct. 1, 2003. Published October 2003. Originallyapproved in 1979. Last previous edition approved in 1997 as C 912 93 (1997).2Campbell, D. E., and Adams, P. B., “Bibliograp
17、hy on Clean Glass: Supplement1,” Journal of Testing and Evaluation, Vol 14, No. 5, September 1986, pp. 260265.3A useful reference is the Handbook of Laboratory Safety, ed., CRC Press, Inc.,2255 Palm Beach Lakes Blvd, West Palm Beach, FL 33409.1Copyright ASTM International, 100 Barr Harbor Drive, PO
18、Box C700, West Conshohocken, PA 19428-2959, United States.TABLE 1 Relative Solubility of Various Glass Component Oxides in HF, Other Inorganic Acids, and NaOH, in Concentrated Solutions atRoom TemperatureNOTE 1Macro or minor/trace levels will determine degree of precipitation, especially in acids, f
19、or 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 other reagents as well.NOTE 4Most alkali solutions must be hot to effect solution.NOTE 5PbSO4is soluble in hot concentrated H2SO4.NOTE 6Sb and B
20、i form insoluble oxychlorides in dilute HCl.NOTE 7Ba is insoluble in concentrated HNO3.Oxides ofHF49 %H2SO496 %HNO370 %HCl37 %HBr HIH3PO485 %NaOH50 %Al sAs ssiiisSb 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 ss
21、ssiLa 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 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
22、i ssssisZn s s sssssZr s sBi iiiiiAs = relatively soluble, i = relatively insoluble.BhotC 912 93 (2003)2Obviously, 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 aqueou
23、s solvent exists that will not attack theglass. The table provides 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 gl
24、ass contain absolutelynone of the components that are soluble 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 probabl
25、y showconsiderable attack by H2SO4. Often this can only be deter-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 thegla
26、ss. For glasses containing substantial concentrations ofsilica, 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
27、 1 is a general guide to selection of such reagents.5.3.2 There 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
28、with another acid to achieve complete solution of allproducts.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 with
29、out the use of HF or alkali. Reference to Table1 will suggest 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
30、 Other Possibilities:5.4.1 When all else fails, organic complexing 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
31、, aluminum,lead, zinc, and barium.5.4.2 Sometimes it is necessary 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
32、all these possibilities, but, byknowing the glass composition, the correct solvent-concentration-temperature-time conditions to effect 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
33、of someinsoluble reaction products. Agitation may help prevent 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 n
34、onhomogeneous “cords”), orwith latent grinding marks hidden 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 avai
35、lable,usually under trade names that give no hint of their chemicalnature. 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 org
36、anic molecules, one end of which is attracted to thesoil or 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 effecti
37、s that the particle or oily film is dislodged. They “surround”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”)
38、. A compoundwith good emulsification will be blended with a good wetter,and built with a polyphosphate for water softening, dispersion,and micelle formation. EDTA and similar compounds are usedfor water softening and solubilization of inorganic compounds,soda ash, and ammonia for pH regulation and s
39、odium 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 theTABLE 2 Threshold Limit Values for Some Common SolventsTLV, ppmA1,1,2-trichloro-1,2-trifluorethane 10
40、00Acetone 750Ethyl alcohol 1000n-Hexane 50Isopropyl alcohol 400Methyl chloroform 350Perchloroethylene 50Trichloroethylene 50Methylene chloride 100Carbon tetrachloride 5AThe TLV values establish parts per million by volume of solvent vapors allowedin air for a normal work week of8haday,5days a week.
41、These are standards setby theAmerican Conference of Governmental Industrial Hygienists, and the valuesshown in this table were effective in 19841985. The most recent recommendedvalues should be consulted in “TLVsRThreshold Limit Values for ChemicalSubstances and Physical Agents in the Work Environme
42、nt and Biological Expo-sure Indices with Intended Changes for 19841985,” published by ACGIH, 6500Glenway Ave., Bldg D-5, Cincinnati, OH 45211.C 912 93 (2003)3builder and the glass components are soluble or insoluble.Polyphosphates and EDTA, in particular, will chelate with andsolubilize metallic ion
43、s, 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 hydrophilic end determinesthe broad basic classification o
44、f 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.6.2 Anionic AgentsThe oldest, and one of the moste
45、ffective 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,are also used extensively.6.3 Cationic AgentsThe catio
46、nic 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 detergents, probablybecause they might be adsorbed, c
47、ausing 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 solubility, deter-gency, surface tension reduction, an
48、d other characteristics canbe adjusted by the length of the ethoxy chain, which is at thehydrophilic 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
49、 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 emulsifiers to incorporatewater in solvents for the purpose of removing water-solublesolids from fabrics; detergents have been developed for lubri-cating oils; and amines are used to accelerate the action of paintstrippers; but otherwise there are few such materials commer-cially available.6.7 ResiduesAll detergent compounds could potentiallyleave residue
