ASTM D2851-15(2023)

This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: D2851 − 15 (Reapproved 2023)
Standard Specification for
Liquid Optical Adhesive
This standard is issued under the fixed designation D2851; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope Rheology Apparatus
1.1 This specification covers liquid optical adhesive for use
3. Terminology
in bonding glass to glass or other transparent adherends.
3.1 Definitions—Many terms in this specification are de-
1.2 The values stated in SI units are to be regarded as
fined in Terminology D907.
standard. The values given in parentheses are provided for
information purposes only.
4. Significance and Use
1.3 The following precautionary caveat pertains only to the
4.1 The bond strength tests provide reasonably accurate
test method portion, Section 6, of this specification: This
information with regard to the bond strength of the adhesives.
standard does not purport to address all of the safety concerns,
Bond strength data may be suitable for specification
if any, associated with its use. It is the responsibility of the user
acceptance, service evaluation, manufacturing control,
of this standard to establish appropriate safety, health, and
research, and development. Bond strength tests are not consid-
environmental practices and determine the applicability of
ered significant for applications differing widely from the test
regulatory limitations prior to use. Specific precautionary
in rate and type of loading.
statements are given in 6.1.1.
1.4 This international standard was developed in accor- 5. General Requirements
dance with internationally recognized principles on standard-
5.1 The adhesive shall be in liquid form and free of solvent
ization established in the Decision on Principles for the
in order to avoid bubble formation in the adhesive layer. Each
Development of International Standards, Guides and Recom-
component shall be completely reactive (without residual
mendations issued by the World Trade Organization Technical
volatile products). The adhesive may be heat-, catalyst-, or
Barriers to Trade (TBT) Committee.
radiation-cured.
5.1.1 Volatility—Volatile content of the adhesive shall not
2. Referenced Documents
exceed 0.5 %, unless otherwise agreed upon between the
2.1 ASTM Standards:
manufacturer and the purchaser.
D542 Test Method for Index of Refraction of Transparent
5.1.2 Viscosity—The viscosity of the adhesive shall be
Organic Plastics
within a well-defined range as agreed upon between the
D897 Test Method for Tensile Properties of Adhesive Bonds
manufacturer and the purchaser.
D904 Practice for Exposure of Adhesive Specimens to
5.1.3 Color—The color of the adhesive shall not exceed the
Artificial Light
color of a platinum-cobalt standard solution No. 300.
D907 Terminology of Adhesives
5.1.4 Cleanliness—The number and size of foreign particles
D1084 Test Methods for Viscosity of Adhesives
found in 100 mL of the adhesive shall not exceed 5 particles in
E308 Practice for Computing the Colors of Objects by Using
the size range from 10 μm to 100 μm (0.1 mm), and none larger
the CIE System
than 100 μm. The number and size of foreign particles in the
E1953 Practice for Description of Thermal Analysis and
catalyst required to cure 100 mL of the adhesive shall not
exceed 2 particles in the size range from 10 μm to 100 μm, and
none larger than 100 μm.
This specification is under the jurisdiction of ASTM Committee D14 on
5.1.5 Refractive Index—The refractive index of the cured
Adhesives and is the direct responsibility of Subcommittee D14.60 on Adhesive
adhesive shall be within a well-defined range as agreed upon
Material Classification System.
between the manufacturer and the purchaser.
Current edition approved May 1, 2023. Published May 2023. Originally
5.1.6 Stability—The liquid adhesive shall not change in
approved in 1970. Last previous edition approved in 2015 as D2851 – 15. DOI:
10.1520/D2851-15R23.
viscosity by greater than 20 % of its original viscosity nor
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
show any formation of solids, when tested as described in 6.6.
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
5.1.7 Light Transmission—Visible light transmission
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. through a bonded glass doublet (two glass disks bonded as
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D2851 − 15 (2023)
described in 6.8) shall not be less than 98.5 % of the total light mL of distilled water and 100 mL of concentrated hydrochloric
transmitted through a single glass disk. There shall be no acid. Dilute to 1000 mL in a volumetric flash using distilled
change in light transmission of a glass doublet after the water. This shall be the concentrated stock solution that has a
environmental test (see 6.9). Pt-Co number of 500. Dilute the concentrated stock solution
5.1.8 Environmental Test—Separation within the adhesive with distilled water as shown below to obtain the desired Pt-Co
layer or from either glass surface of the glass doublet shall not standard.
exceed 1.0 mm in depth nor extend beyond 180° of the
periphery of the adhesive layer (see 6.9).
5.1.9 Bond Strength—The tensile strength of a bonded glass
doublet after being subjected to the environmental test (see 6.9)
shall be greater than 200 psi (1.38 MPa) or any value agreed
upon between the manufacturer and the purchaser.
6. Test Methods
6.1 Volatility:
6.1.1 Thoroughly clean three petri dish bottoms, 95 mm
outside diameter, by washing with detergent and a scrub brush.
Rinse with warm running tap water. Place petri dishes in an
air-circulating oven for 30 min at 65 °C 6 2 °C (150 °F 6
4 °F). Raise temperature to 110 °C 6 2 °C (230 °F 6 4 °F) for
1 h. Remove petri dishes from oven and place in a desiccator.
After petri dishes have cooled to room temperature, approxi-
mately 2 h, weigh each dish to the nearest 0.1 mg.
(Warning—In addition to other precautions, do not handle
petri dishes with bare hands. Use tongs.)
6.1.2 Replace each petri dish in the oven at 110 °C 6 2 °C
(230 °F 6 4 °F) for 1 h. Repeat cool-down procedure. Reweigh
each petri dish to the nearest 0.1 mg. If weight agrees to within
60.2 mg of initial weight, proceed to 6.1.3. If weight exceeds
this 60.2 mg range, repeat process until a constant weight for
each petri 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 for
curing. Weigh each dish to the nearest 0.1 mg. Cure the
adhesive by following the procedure described by the manu-
facturer. Then place each sample in an oven at 105 °C 6 2 °C
(220 °F 6 4 °F) to a constant weight (same procedure as in
5.1.1 but at 105 °C). Reweigh each sample to the nearest 0.1
mg and calculate the percent volatile
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