ASTM C581-00
(Practice)Standard Practice for Determining Chemical Resistance of Thermosetting Resins Used in Glass-Fiber-Reinforced Structures Intended for Liquid Service
Standard Practice for Determining Chemical Resistance of Thermosetting Resins Used in Glass-Fiber-Reinforced Structures Intended for Liquid Service
SCOPE
1.1 This practice is designed to evaluate, in an unstressed state, the chemical resistance of thermosetting resins used in the fabrication of reinforced thermosetting plastic (RTP) laminates. This practice provides for the determination of changes in the properties, described as follows, of the test specimens and test reagent after exposure of the specimens to the reagent: hardness of specimens, weight change thickness, appearance of specimens, appearance of immersion media, and flexural strength and modulus.
1.2 The values stated in inch-pound units are to be regarded as the standard. The values in parentheses are given for information only.
Note 1--This practice may also be used to evaluate other factors, such as surfacing veils, the effect of resin additives, and fabrication variables on the chemical resistance of the resin.
Note 2--There is no similar or equivalent ISO standard.
1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
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Standards Content (Sample)
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An American National Standard
Designation: C 581 – 00
Standard Practice for
Determining Chemical Resistance of Thermosetting Resins
Used in Glass-Fiber-Reinforced Structures Intended for
Liquid Service
This standard is issued under the fixed designation C 581; 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 (e) indicates an editorial change since the last revision or reapproval.
1. Scope 3. Significance and Use
1.1 This practice is designed to evaluate, in an unstressed 3.1 The results obtained by this practice shall serve as a
state, the chemical resistance of thermosetting resins used in guide in, but not as the sole basis for, selection of a thermo-
the fabrication of reinforced thermosetting plastic (RTP) lami- setting resin used in an RTP structure. No attempt has been
nates. This practice provides for the determination of changes made to incorporate into the practice all the various factors that
in the properties, described as follows, of the test specimens may enter into the serviceability of an RTP structure when
and test reagent after exposure of the specimens to the reagent: subjected to chemical environments. These factors may include
hardness of specimens, weight change thickness, appearance of stress, different resin-to-glass ratios, and multiple veils.
specimens, appearance of immersion media, and flexural
4. Apparatus
strength and modulus.
4.1 Hardness Testing Instrument—This shall be as de-
1.2 The values stated in inch-pound units are to be regarded
as the standard. The values in parentheses are given for scribed in Test Method D 2583.
4.2 Flexural Properties Testing Apparatus, in accordance
information only.
with Test Methods D 790.
NOTE 1—This practice may also be used to evaluate other factors, such
4.3 Thickness Measurement—A micrometer suitable for
as surfacing veils, the effect of resin additives, and fabrication variables on
measurement to 0.001 in. (0.025 mm).
the chemical resistance of the resin.
4.4 Containers, of sufficient size, capacity, and inertness to
NOTE 2—There is no similar or equivalent ISO standard.
allow total immersion of reinforced thermosetting plastic
1.3 This standard does not purport to address all of the
specimens in the specific corrosives chosen for testing. These
safety concerns, if any, associated with its use. It is the
containers shall, when necessary, be capable of maintaining
responsibility of the user of this standard to establish appro-
liquid levels of volatile solutions, that is, solvents. This can be
priate safety and health practices and determine the applica-
accomplished by the use of reflux condensers.
bility of regulatory limitations prior to use.
4.5 Heating Apparatus—A constant temperature oven, heat-
ing mantle, or liquid bath capable of maintaining temperature
2. Referenced Documents
within range of 64.0°F (62.2°C). Proper precautions should
2.1 ASTM Standards:
be taken if the corrosives selected are flammable liquids.
D 790 Test Methods for Flexural Properties of Unreinforced
4.6 Analytical Balance, suitable for accurate weighing to
and Reinforced Plastics and Electrical Insulating Materi-
2 0.001 g.
als
D 2563 Practice for Classifying Visual Defects in Glass-
5. Reagents
Reinforced Plastic Laminate Parts
5.1 The test media shall consist of the reagents or solutions
D 2583 Test Method for Indentation Hardness of Rigid
to which the RTP laminates are to be exposed.
Plastics by Means of a Barcol Impressor
D 2584 Test Method for Ignition Loss of Cured Reinforced
6. Test Specimens
Resins
6.1 Standard Laminates—Prepare standard fiber-reinforced
laminates using identical reinforcement in all of the laminates.
The laminates shall be constructed of the following materials:
This practice is under the jurisdiction of ASTM Committee D20 on Plastics and
6.1.1 Surfacing Mat (Veil)—A thin mat of fine fibers used
is the direct responsibility of Subcommittee D20.23 on Reinforced Plastic Piping
Systems and Chemical Equipment.
primarily to produce a smooth, resin-rich surface on a rein-
Current edition approved July 10, 2000. Published September 2000. Originally
forced plastic. The surfacing veil helps determine the thickness
published as C 581 – 65 T. Last previous edition C 581 – 94.
2 of the resin-rich layer, reduces microcracking and provides a
Annual Book of ASTM Standards, Vol 08.01.
non-wicking chemically–resistant layer. The surfacing veil
Annual Book of ASTM Standards, Vol 08.02.
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NOTICE: This standard has either been superceded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
C 581
shall be compatible with the resin, and manufactured with ing mat on a flat surface covered with plastic release film or
uniform fiber distribution and non-bundled fibers. The dry veil treated with a suitable release agent and roll to distribute resin.
layer(s) shall be a minimum 10 mils in thickness and produce
NOTE 4—The following formula may be used as a guide to determine
a 10 to 15 mil resin-saturated veil layer per 10 mils of dry veil.
the total weight of resin to be used. This is equivalent to 12.5 volume %
To eliminate the surfacing veil as a variable in corrosion tests,
glass fiber in the laminate. Grams resin equals grams glass fiber material
prepare each laminate within a test group with the same
per 6.2.3 times 2.82 G. Where G equals specific gravity of cured resin.
Excess resin may be used due to loss by adhering to mixing containers,
surfacing veil.
rollers, and other factors. A suggested amount of excess resin is 10 to 15 %
6.1.2 Chopped Strand Mat—Type E glass fiber with sizing
by weight.
and binder compatible with the resin. Other glass fiber com-
6.3.2 Follow with three plies of 1.5 oz/ft chopped strand
positions may be used but should be considered as variables for
mat and resin. Roll after each ply to distribute and wet-out the
comparison to the standard.
chopped strand mat. Rolling with a serrated roller may be done
6.1.3 Resin—Catalyzed and promoted in accordance with
after each ply to remove entrapped air but shall be done in
the resin manufacturer’s recommendation.
accordance with 6.3.4. The mat weight shall be within 65%of
1.5 oz/ft upon weighing the full 26 by 33-in. cut (660 by
NOTE 3—Fillers, such as antimony trioxide for improved fire retardancy
or thixotropes for viscosity control, may be added, but may detract from
838-mm) piece, (or other full dimension used, 6.2.1.).
the corrosion resistance of the test laminate.
NOTE 5—Chopped strand mat should be cut so that the 26-in. dimen-
6.2 Dimensions and General Properties—The laminates sion is across the width of the roll and the 33-in. dimension is along the
machine direction of the mat. Mat weight variation will most commonly
shall conform to the required dimensions and general proper-
occur across the width of the mat. If a wide roll of mat, 52 in. (1320 mm)
ties of 6.2 and be fabricated in accordance with 6.3.
or greater, is used, the two plies of mat should be placed in the laminate
6.2.1 Laminate Size—A suitable laminate size has been
such that the center cut of one ply is placed over the outside edge of the
found to be 26 by 33 in. (660 by 838 mm) after trimming. This
second ply. If narrower width mat is used, the second ply should be
laminate size is not restrictive and other dimensions may be reversed 180° in the machine direction and laid on top of the first ply to
minimize weight variations.
used.
6.2.2 Thickness—The thickness of the cured standard lami- 6.3.3 Follow with a 10-mil (0.25-mm) surfacing mat as in
6.3.1.
nate shall be between 0.130 and 0.140 in. (3.30 and 4.40 mm).
6.3.4 Remove the air by rolling over the surface with a
6.2.3 Reinforcement Content—The glass fiber and binder
2 2
serrated metal or plastic roller. Take care not to expel enough
shall be 0.945 6 0.09 oz/ft (three layers of 1.5 oz/ft chopped
resin to raise the glass content above the permissible maxi-
strand mat–0.591 oz/ft having a nominal binder content of
mum. The laminate is considered within the range of allowable
3.5 % and two layers of 10 mil surfacing mat–0.044 oz/ft
levels of resin and glass if the thickness of the laminate is
having a nominal binder content of 7 %)—determined by
within 0.120 and 0.130 in., as described in 6.2.2.
preweighing the materials prior to construction of the laminate.
6.3.5 After the lay-up is completed, cover the laminate with
This is equivalent to 23.6 weight % (12.5 volume %) glass
a plastic release film to prevent air inhibition or to provide a
fiber when using a resin having a cured specific gravity of 1.15.
uniform smooth glossy surface, or both. Carefully smooth
Such a laminate will have a thickness of 0.125 in. (3.18 mm).
down to remove entrapped air.
The use of resins having different specific gravities will result
in different weight percentages of glass fiber, but the volume
NOTE 6—The application of the release film may be accomplished by
percentage of glass fiber will remain the same. When using any convenient method. Regardless of how it is applied, it is critical that
any entrapped air between the film and the laminate be entirely removed.
synthetic organic fiber surfacing veil, the glass content shall be
2 One method of application is done by previously wrapping the film around
0.885 oz/ft ( three layers of 1.5oz/ft. chopped strand mat. (two
a metal rod. Starting at one edge of the laminate, slowly unroll the film
layers of 1.5 oz/ft chopped strand mat having a nominal
from the rod, keeping a bead of resin ahead of the rod as you cross the
binder content of 3.5 %).
laminate. Any entrapped air remaining can be removed by rubbing a
tongue depressor across the release film surface. Carefully pull the film
6.2.4 Hardness—The hardness shall be at least 90 % of that
taut and fasten at the edges to prevent wrinkling of the film. Placing stops
of a fully-cured clear casting of the resin, or of a similarly
(neoprene has been found to be suitable) around the edges of the laminate
constructed laminate as defined by the resin manufacturer.
and passing a heavy metal roller over the laminate helps to insure uniform
Hardness shall be determined in accordance with s4.1. It
controlled thickness.
should be noted that the use of synthetic veil will result in
6.3.6 Cure as recommended by the resin manufacturer. The
significantly lower hardness values. The hardness value will
cure schedule shall be reported.
vary with the type of resin and number of plies of synthetic
6.3.7 Trim edges as required.
veil. The resin manufacturer should be contacted for the
6.4 Record of Standard Laminate Construction—Record the
allowable Barcol hardness value of a laminate containing
properties of the standard laminate as follows:
synthetic veils with the specific resin.
6.4.1 Hardness—Determine Barcol hardness on the strip as
6.2.5 Laminate Condition—The laminate shall meet Accep-
described in 6.2.4 in accordance with Test Method D 2583.
tance Level I of Table I of Practice D 2563.
6.3 Fabrication of Standard Laminate—The sequence of
lay-up shall be as follows:
3 to 5 mil standard oriented polyester film (MYLARt—Types A, S, or D, or
6.3.1 Apply catalyzed resin and a 10-mil (0.25-mm) surfac- MELINEXt—Types S, 0, or 442) has been found suitable for this purpose.
NOTICE: This standard has either been superceded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
C 581
6.4.2 Laminate Conditions—Visually examine the laminate. 7.3.1 Note any indication of surface attack on a coupon, any
The laminate shall meet Acceptance Level I of Table 1 of
discoloration of the test solution, and the formation of any
Practice D 2563. sediment.
6.4.3 If the laminate meets the requirements of this speci-
7.3.2 After final blotting, immediately measure the coupon
fication, retain the laminate sections for preparation of test
thickness to the nearest 0.001 in. (0.025 mm) in the geometric
specimens.
center of each intended 1 by 3 in. (25 by 76.2 mm) specimen.
Measure the coupon to the nearest 0.01g. The Barcol hardness
NOTE 7—The major criteria for accepting a laminate is thickness and
can then be checked, taking an average of ten readings on each
not glass content. If glass content is desired, cut eight 1 by 1 in. specimens
from the center of the laminate and test in accordance with Test Method
coupon, a minimum of 0.50 in. (12.7 mm) from the edge.
D 2584.
7.3.3 After washing and measuring thickness, weight, and
6.5 Individual Test Specimens:
Barcol hardness, place the coupons in an air-tight polyethylene
6.5.1 Specimens for immersion in test solutions shall be
bag for conditioning or shipping as described in 7.4.1.
approximately 4 by 5 in. (101.6 by 127 mm), cut from the
7.4 Flexural Testing—Determine the flexural strength and
standard laminate.
modulus for: (1) two sets of three specimens immediately
6.5.2 Identity of specimens shall be maintained by suitable
following the curing period, and (2) one set of three specimens
means.
after each inspection, for each solution, and each test tempera-
6.5.3 Cut edges and drilled holes, if used for suspension,
ture. Calculation of flexural strength and modulus after expo-
shall be sanded smooth and coated with paraffinated resin.
sure should use the coupon thickness determined at the time of
6.5.4 The number of specimens required is dependent on the
flexural testing as measured in 7.3.2. The two pretested sets
number of test solutions to be employed, the number of
shall be taken from the center of the laminate as described in
different temperatures at which testing is performed, and the
6.2.1. The flexural strengths for these two sets shall be
number of test intervals. In addition, at least two 4 by 5 in.
averaged together for use in calculating the retained flexural
(101.6 by 127 mm) specimens shall be available for test (see
strength in 8.2. The flexural modulus values shall also be
7.4) following the curing period, prior to immersion.
averaged for use in 8.2.
7. Procedure
7.4.1 Flexural tests shall be conducted in accordance with
7.1 Measurement of Specimens—Immediately following the Procedure A of Test Methods D 790, except for the condition-
curing period, measure the thickness of the specimens to the
ing parameters specified in this document. Coupons being
nearest 0.001 in. (0.025 mm) at the geometric center of each of tested at the exposure location shall be placed in the condi-
the intende
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