ASTM C793-91(1997)e1

e1
Designation:C793–91(Reapproved 1997)
Standard Test Method for
Effects of Accelerated Weathering on Elastomeric Joint
Sealants
This standard is issued under the fixed designation C793; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
e NOTE—Keywords were revised editorially in June 1997.
1. Scope 5. Significance and Use
1.1 This test method covers a laboratory procedure for 5.1 It is known that ultraviolet radiation contributes to the
determining the effects of accelerated weathering on cured-in- degradation of sealants in exterior building joints.The use of a
place elastomeric joint sealants (single- and multicomponent) laboratory accelerated weathering machine with ultraviolet
for use in building construction. radiation and intermittent water spray appears to be a feasible
1.2 The values stated in SI units are to be regarded as the means to give indications of early degradation by the appear-
standard. The values in parentheses are for information only. ance of sealant cracking. However, other factors such as UV
1.3 This standard does not purport to address all of the exposure in combination with extension may produce more
safety concerns, if any, associated with its use. It is the severe degradation than UV alone. The effect of the test is
responsibility of the user of this standard to establish appro- made more sensitive by the addition of the bending of the
priate safety and health practices and determine the applica- specimen at cold temperature.
bility of regulatory limitations prior to use.
6. Apparatus
2. Referenced Documents
6.1 Exposure Apparatus—An accelerated weathering ma-
2.1 ASTM Standards: chine, twin-enclosed carbon arc with 102-18 light/water spray
C717 Terminology of Building Seals and Sealants cycle (102 min of light followed by 18 min of light and
G 23 Practice for Operating Light-Exposure Apparatus deionized water). It shall conform to Type D of Practice G23.
(Carbon-Arc Type) With and Without Water for Exposure
NOTE 1—There are several other weathering machines described in
of Nonmetallic Materials
Practice G23 available for use, and these may or may not give different
results from the one described under Type D. Instruments that have a
3. Terminology
means of humidification should operate without the humidifier.
3.1 Definitions—See Terminology C717 for applicable
6.2 Freezer or Cold Box, having a temperature controlled
definitions of the following terms: cure, elastomeric, joint,
at−26 6 2°C (−15 6 3.6°F).
sealant, and substrate.
6.3 Rectangular Brass Frame, with inside dimensions 130
1 1
by40by3mm(5by1 ⁄2 by ⁄8 in.).
4. Summary of Test Method
6.4 Aluminum Plates,three,each152by80by0.3mm(6by
4.1 Three sealant specimens are spread on aluminum plates
3 by 0.01 in.).
and exposed to 250 h of ultraviolet radiation with intermittent
6.5 Steel Mandrel, 12.7 mm ( ⁄2 in.) in diameter and about
water spray in a standard accelerated weathering machine.
102 mm (4 in.) long.
Followingthistreatmentthespecimensareexposedfor24hin
6.6 Thin-Bladed Knife.
a freezer maintained at−26 6 2°C (−15 6 3.6°F). At the end
6.7 Straightedge, metal or plastic, about 152 mm (6 in.)
of the cold exposure the specimens are bent over a mandrel
long.
within1satthe specified temperature.
6.8 Spatula, steel, about 152 mm (6 in.) long.
7. Standard Test Conditions
This test method is under the jurisdiction of ASTM Committee C-24 on
7.1 Unless otherwise specified by those authorizing the test,
BuildingSealsandSealantsandisthedirectresponsibilityofSubcommitteeC24.32
on Chemically Curing Sealants.
standard conditions of temperature and relative humidity shall
Current edition approved April 15, 1991. Published June 1991. Originally
be 23 6 2°C (73.4 6 3.6°F) and 50 6 5%, respectively.
published as C793–75. Last previous edition C793–75(1986).
Annual Book of ASTM Standards, Vol 04.07.
Annual Book of ASTM Standards, Vol 14.02.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
e1
C793–91 (1997)
frame until the sealant is sufficiently set that it will retain its rectangular
8. Procedure
shape.
8.1 Test of Multicomponent Sealants:
8.2 Test of Single-Component Sealants:
8.1.1 Condition at least 200 g o
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