1、Designation: D2851 98 (Reapproved 2015)Standard Specification forLiquid Optical Adhesive1This standard is issued under the fixed designation D2851; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A number
2、 in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This specification covers liquid optical adhesive for usein bonding glass to glass or other transparent adherends.1.2 The values stated in SI
3、 units are to be regarded asstandard. The values given in parentheses are provided forinformation purposes only.1.3 The following precautionary caveat pertains only to thetest method portion, Section 6, of this specification: Thisstandard does not purport to address all of the safety concerns,if any
4、, associated with its use. It is the responsibility of the userof this standard to establish appropriate safety and healthpractices and determine the applicability of regulatory limita-tions prior to use. Specific precautionary statements are givenin 6.1.1.2. Referenced Documents2.1 ASTM Standards:2
5、D542 Test Method for Index of Refraction of TransparentOrganic PlasticsD897 Test Method for Tensile Properties ofAdhesive BondsD904 Practice for Exposure of Adhesive Specimens toArtificial LightD907 Terminology of AdhesivesD1084 Test Methods for Viscosity of AdhesivesE308 Practice for Computing the
6、Colors of Objects by Usingthe CIE System3. Terminology3.1 DefinitionsMany terms in this specification are de-fined in Terminology D907.4. Significance and Use4.1 The bond strength tests provide reasonably accurateinformation with regard to the bond strength of the adhesives.Bond strength data may be
7、 suitable for specificationacceptance, service evaluation, manufacturing control,research, and development. Bond strength tests are not consid-ered significant for applications differing widely from the testin rate and type of loading.5. General Requirements5.1 The adhesive shall be in liquid form a
8、nd free of solventin order to avoid bubble formation in the adhesive layer. Eachcomponent shall be completely reactive (without residualvolatile products). The adhesive may be heat-, catalyst-, orradiation-cured.5.1.1 VolatilityVolatile content of the adhesive shall notexceed 0.5 %, unless otherwise
9、 agreed upon between themanufacturer and the purchaser.5.1.2 ViscosityThe viscosity of the adhesive shall bewithin a well-defined range as agreed upon between themanufacturer and the purchaser.5.1.3 ColorThe color of the adhesive shall not exceed thecolor of a platinum-cobalt standard solution No. 3
10、00.5.1.4 CleanlinessThe number and size of foreign particlesfound in 100 mL of the adhesive shall not exceed 5 particles inthe size range from 10 to 100 m (0.1 mm), and none largerthan 100 m. The number and size of foreign particles in thecatalyst required to cure 100 mL of the adhesive shall notexc
11、eed 2 particles in the size range from 10 to 100 m, andnone larger than 100 m.5.1.5 Refractive IndexThe refractive index of the curedadhesive shall be within a well-defined range as agreed uponbetween the manufacturer and the purchaser.5.1.6 StabilityThe liquid adhesive shall not change inviscosity
12、by greater than 20 % of its original viscosity norshow any formation of solids, when tested as described in 6.6.5.1.7 Light TransmissionVisible light transmissionthrough a bonded glass doublet (two glass disks bonded asdescribed in 6.8) shall not be less than 98.5 % of the total lighttransmitted thr
13、ough a single glass disk. There shall be nochange in light transmission of a glass doublet after theenvironmental test (see 6.9).5.1.8 Environmental TestSeparation within the adhesivelayer or from either glass surface of the glass doublet shall notexceed 1.0 mm in depth nor extend beyond 180 of thep
14、eriphery of the adhesive layer (see 6.9).1This specification is under the jurisdiction of ASTM Committee D14 onAdhesives and is the direct responsibility of Subcommittee D14.60 on AdhesiveMaterial Classification System.Current edition approved April 1, 2015. Published April 2015. Originallyapproved
15、in 1970. Last previous edition approved in 2009 as D2851 98 (2009).DOI: 10.1520/D2851-98R15.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document S
16、ummary page onthe ASTM website.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States15.1.9 Bond StrengthThe tensile strength of a bonded glassdoublet after being subjected to the environmental test (see 6.9)shall be greater than 200 psi (1.
17、38 MPa) or any value agreedupon between the manufacturer and the purchaser.6. Test Methods6.1 Volatility:6.1.1 Thoroughly clean three petri dish bottoms, 95-mmoutside diameter, by washing with detergent and a scrub brush.Rinse with warm running tap water. Place petri dishes in anair-circulating oven
18、 for 30 min at 65 6 2C (150 6 4F). Raisetemperature to 110 6 2C (230 6 4F) for 1 h. Remove petridishes from oven and place in a desiccator. After petri disheshave cooled to room temperature, approximately 2 h, weigheach dish to the nearest 0.1 mg. (WarningIn addition toother precautions, do not hand
19、le petri dishes with bare hands.Use tongs.)6.1.2 Replace each petri dish in the oven at 110 6 2C (2306 4F) for 1 h. Repeat cool-down procedure. Reweigh eachpetri dish to the nearest 0.1 mg. If weight agrees to within 60.2mg of initial weight, proceed to 6.1.3. If weight exceeds this60.2-mg range, re
20、peat process until a constant weight for eachpetri dish is obtained.6.1.3 To each petri dish add approximately 10 g of adhesive,and mix with catalyst or any component part required forcuring. Weigh each dish to the nearest 0.1 mg. Cure theadhesive by following the procedure described by the manu-fac
21、turer. Then place each sample in an oven at 105 6 2C (2206 4F) to a constant weight (same procedure as in 5.1.1 but at105C). Reweigh each sample to the nearest 0.1 mg andcalculate the percent volatile matter as follows.Volatile matter, % 5 A 2 B!/A# 3100 (1)where:A = weight of original sample, andB
22、= weight of cured adhesive taken to constant weight.6.2 ViscosityMeasure the viscosity of the adhesive inaccordance with Test Methods D1084. (Brookfield, Method B,or any other suitable viscometer may be used.)6.3 ColorDetermine the color of the adhesive by compar-ing it with platinum-cobalt (Pt-Co)
23、standards. Place 100 mL ofadhesive in a 100-mL Nessler tube. Make color observationsby placing the adhesive-filled Nessler tube vertically over asheet of white paper while looking down and through the filledtube. Compare the color observed with a standard Nessler tube,containing 100 mL of the Pt-Co
24、standard held in the samemanner.6.3.1 Prepare the Pt-Co standard solutions by dissolving1.246 g of potassium platinic chloride and 1000 g of cpcrystalline cobaltous chloride hexahydrate in a solution of 300mL of distilled water and 100 mL of concentrated hydrochloricacid. Dilute to 1000 mL in a volu
25、metric flash using distilledwater. This shall be the concentrated stock solution that has aPt-Co number of 500. Dilute the concentrated stock solutionwith distilled water as shown below to obtain the desired Pt-Costandard.Pt-Co Stock Solution Distilled H2ONumber of Pt-Co 500, mL to Be Added, mL500 1
26、00 0450 90 10400 80 20350 70 30300 60 40250 50 50200 40 60150 30 70100 20 8075 15 8550 10 900 0 100Store the stock solutions in clean glass bottles and stopperthem to prevent evaporation loss.6.4 Foreign Particle ContentInspect a 100-mL sample ofthe liquid adhesive and a sample of its catalyst for c
27、leanlinessby filtering each through a low-form Gooch crucible fitted witha filter membrane of 5.0 to 10.0-m pore size and a colorsuitable to easily detect and examine foreign particles. Measurethe size of the particles by means of a calibrated traversingmicroscope (10) or other equivalent means. If
28、the viscosity ofthe sample is too high, dilute it with any clean and suitablesolvent to permit easy flow of the liquid through the filtermembrane.6.5 Refractive IndexPrepare a solid adhesive specimen bymeasuring approximately 6.3 by 12.7 by 12.7 mm (0.25 by 0.5by 0.5 in.). Make two adjacent surfaces
29、 measuring 6.3 by 12.7mm flat (0.25 by 0.5 in.), smooth, and perpendicular to eachother. Polish by means of a rotating (500 r/min) felt-coveredpolishing wheel wetted with a solution of cerium oxide(polishing grade) in water. Use the polished surface in contactwith the prism. Determine the index of r
30、efraction in accordancewith the refractometric method described in Test MethodD542. The contacting fluid between the prism and the adhesivesurface may be bromonaphthalene. A fluid with a closermatching refractive index can be prepared by diluting thebromonaphthalene with refined mineral oil (medicin
31、al grade).6.6 StabilityPlace the adhesive in an air-circulating ovenat 57 6 1.1C (135 6 2F) for 168 h or at any temperature ortime agreed upon between the manufacturer and the user.6.7 Light TransmissionDetermine the visible light trans-mission in accordance with Practice E308. The specimen shallcon
32、sist of a bonded glass doublet prepared as described in 6.8.Make a comparison with the light transmission through oneglass disk similar to the one used for preparing the doublet.Clean the glass disk as described in preparing the disk forbonding. All three doublets shall pass. Retain for environmen-t
33、al test (see 6.9).6.8 Glass Doublet PreparationThe flat and polished plateglass (silvering grade) disks shall be 31.756 0.8 mm (1.25 60.03 in.) in diameter and 6.35 mm (0.25 in.) thick, with edgeslightly ground to remove their sharpness. Clean with a camelshair brush that is wet with ethanol. Rinse
34、the flat surface to bebonded in a stream of clean ethanol and then allow it to dry ina desiccator for 1 h. Apply the adhesive, prepared in accor-dance with manufacturers instructions, dropwise to the centerof one of the clean and dry disks. Place a second disk over thedrop of adhesive with a rotary
35、motion so that the adhesiveD2851 98 (2015)2spreads thinly and uniformly between the two glass surfaceswithout trapping air bubbles. Wipe excess adhesive from theperiphery of the assembly and cure the film as recommendedby the adhesive manufacturer. Three doublets are required fortests.6.9 Environmen
36、tal TestUse the specimens for the environ-mental test that passed the light transmission test as describedin 5.1.7. The environmental test shall consist of the followingexposure tests, in the order indicated.(a) Immersion in distilled water at 38 6 1.1C (100 6 2F)for 20 h.(b) Exposure to 54 6 1.1C (
37、65 6 2F) for 20 h.(c) Exposure to 71 6 1.1C (160 6 2F) and 100 %relative humidity for 20 h.(d) Exposure to accelerated weathering for 20 h in accor-dance with Practice D904.6.9.1 Subject three glass doublets that passed the lighttransmission test to the environmental test. In performing thetest, coo
38、l or heat the doublets gradually, over a period of notless than 2 h, and return them to room temperature in the samegradual manner. Examine each doublet for edge separation orother imperfection. All three doublets shall pass the environ-mental test for separation and light transmission. Retain theth
39、ree glass doublets for bond strength determination (6.10).6.10 Bond StrengthBond each of the three glass doubletspassing the test described in 6.9 to metal tensile specimens,described in Test Method D897, to form a metal-to-doublet-to-metal bonded assembly. Use a room temperature curingadhesive, suc
40、h as an epoxy, having a tensile bond strengthbetween metal and glass of approximately 2000 psi (13.8 MPa)to bond the doublet to the metal surface. Three assemblies shallbe prepared and tested in tension as described in Test MethodD897, and all shall pass. Bond strengths at temperatures otherthan roo
41、m temperature shall be made upon agreement betweenthe manufacturer and the purchaser.7. Keywords7.1 adhesive; liquid; opticalASTM International takes no position respecting the validity of any patent rights asserted in connection with any item mentionedin this standard. Users of this standard are ex
42、pressly advised that determination of the validity of any such patent rights, and the riskof infringement of such rights, are entirely their own responsibility.This standard is subject to revision at any time by the responsible technical committee and must be reviewed every five years andif not revi
43、sed, either reapproved or withdrawn. Your comments are invited either for revision of this standard or for additional standardsand should be addressed to ASTM International Headquarters. Your comments will receive careful consideration at a meeting of theresponsible technical committee, which you ma
44、y attend. If you feel that your comments have not received a fair hearing you shouldmake your views known to the ASTM Committee on Standards, at the address shown below.This standard is copyrighted by ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959,United Sta
45、tes. Individual reprints (single or multiple copies) of this standard may be obtained by contacting ASTM at the aboveaddress or at 610-832-9585 (phone), 610-832-9555 (fax), or serviceastm.org (e-mail); or through the ASTM website(www.astm.org). Permission rights to photocopy the standard may also be secured from the Copyright Clearance Center, 222Rosewood Drive, Danvers, MA 01923, Tel: (978) 646-2600; http:/ 98 (2015)3
