ASTM D871-96
(Test Method)Standard Test Methods of Testing Cellulose Acetate
Standard Test Methods of Testing Cellulose Acetate
SCOPE
1.1 These test methods cover procedures for testing cellulose acetate.
1.2 The test procedures appear in the following sections: Sections Ash 8 and 11 Color and Haze 68 to 72 Combined Acetyl or Acetic Acid Content Test Method A. Solution Method 17, 19 to 23 Test Method B. Heterogeneous Saponification Method 17, 24 to 26 Free Acidity 12 to 16 Heat Stability 47 to 56 Hydroxyl Content 27 to 33 Intrinsic Viscosity 57 to 62 Moisture Content 4 and 7 Primary Hydroxyl Content 34 to 39 Sulfur or Sulfate Content 40 to 45 Viscosity 63 and 66
General Information
Relations
Standards Content (Sample)
NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
Designation: D 871 – 96
Standard Test Methods of Testing
Cellulose Acetate
This standard is issued under the fixed designation D 871; 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 specifications are available. Other grades may be used, pro-
vided it is first ascertained that the reagent is of sufficiently
1.1 These test methods cover procedures for testing cellu-
high purity to permit its use without lessening the accuracy of
lose acetate.
the determination.
1.2 The test procedures appear in the following sections:
3.2 Unless otherwise indicated, references to water shall be
Sections
understood to mean reagent tared, low, wide-form weighing
Ash 8to11
Color and Haze 67 to 72
bottle and water, conforming to Specification D 1193.
Combined Acetyl or Acetic Acid Content
Test Method A. Solution Method 17, 19 to 23
MOISTURE CONTENT
Test Method B. Heterogeneous Saponification Method 17, 24 to 26
Free Acidity 12 to 16
4. Significance and Use
Heat Stability 47 to 56
Hydroxyl Content 27 to 33
4.1 Moisture content of the cellulose ester can be used to
Intrinsic Viscosity 57 to 62
estimate the dry weight of the cellulose ester. Since cellulose
Moisture Content 4 to 7
Primary Hydroxyl Content 34 to 39
esters are desiccants, their moisture content can vary greatly
Sulfur or Sulfate Content 40 to 45
depending on storage.
Viscosity 63 to 66
5. Procedure
This standard does not purport to address the safety con-
cerns, if any, associated with its use. It is the responsibility of
5.1 Transfer about5gofthe sample to a tared, low,
the user of this standard to establish appropriate safety and
wide-form weighing bottle and weigh to the nearest 0.001 g.
health practices and determine the applicability of regulatory
Dry in an oven for2hat105 6 3 C. Remove the bottle from
limitations prior to use.
the oven, cover, cool in a desiccator, and weigh.
2. Referenced Documents
6. Calculation
2.1 ASTM Standards:
6.1 Calculate the percentage of moisture as follows:
D 1193 Specification for Reagent Water
Moisture, % 5 ~A/B! 3 100
D 1343 Test Method for Viscosity of Cellulose Derivatives
by Ball-Drop Method
where:
D 2929 Test Method for Sulfur Content of Cellulosic Ma- A = weight loss on heating, g, and
terials by X-Ray Fluorescence B = sample used, g.
D 5897 Test Method for Determination of Percent Hydroxyl
7. Precision and Bias
on Cellulose Esters by Potentiometric Titration—
7.1 No statement on bias can be made as no reference
Alternative Method
material is available as a standard.
3. Purity of Reagents
ASH
3.1 Reagent grade chemicals shall be used in all tests.
Unless otherwise indicated, it is intended that all reagents shall
8. Significance and Use
conform to the specifications of the Committee on Analytical
8.1 Ash content gives an estimate of the inorganic content
Reagents of the American Chemical Society, where such
of cellulose ester samples. The presence of high levels of
These test methods are under the jurisdiction of ASTM Committee D-1 on Paint
and Related Coatings, Materials, and Applications and are the direct responsibility Reagent Chemicals, American Chemical Society Specifications, American
of Subcommittee D01.36 on Cellulose and Cellulose Derivatives. Chemical Society, Washington, DC. For suggestions on the testing of reagents not
Current edition approved Nov. 10, 1996. Published January 1997. Originally listed by the American Chemical Society, see Analar Standards for Laboratory
published as D 871 – 46. Last previous edition D871 – 91. Chemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeia
Annual Book of ASTM Standards, Vol 11.01. and National Formulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville,
Annual Book of ASTM Standards, Vol 06.03. MD.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
D871–96
inorganic content (ash) can be detrimental to the melt stability 14.2 Run a blank determination on the water, using the same
and optical clarity of a cellulose ester in melt processing or act volume as was used in extracting the sample.
as a potential source of insolubles when the ester is used in
15. Calculation
solution.
15.1 Calculate the percentage of acidity as free acetic acid
9. Procedure
as follows:
9.1 Dry the sample for2hat105 6 3°C and weigh 10 to 50
Free acetic acid, % 5 @~A 2 B!N 3 0.06 3 100#/W (1)
g, to the nearest 0.01 to 0.1 g, depending on its ash content and
the accuracy desired. An air-dried sample may be used and
where:
calculated to dry weight using the value for moisture deter-
A = NaOH solution used to titrate the sample, mL,
mined as in Sections 5 and 6. Burn directly over a flame in a
B = NaOH solution used to titrate the blank, mL,
N = normality of the NaOH solution, and
100-mL tared platinum crucible that has been heated to
W = sample used, g.
constant weight and weighed to the nearest 0.1 mg. Add the
sample in portions if more than 10 g is taken. The sample
16. Precision and Bias
should burn gently and the portions should be added as the
flame subsides. Continue heating with a burner only as long as
16.1 No statement on bias can be made as no reference
the residue burns with a flame. Transfer the crucible to a muffle
material is available as a standard.
furnace and heat at 550 to 600°C for 3 h, or longer if required,
to burn all the carbon. Allow the crucible to cool and then
COMBINED ACETYL OR ACETIC ACID
transfer it, while still warm, to a desiccator. When the crucible
CONTENT
has cooled to room temperature, weigh accurately to the
nearest 0.1 mg.
17. Scope
17.1 Two test methods are described for determining the
10. Calculation
combined acetyl or acetic acid content. The first, described in
10.1 Calculate the percentage of ash as follows:
Sections 19 to 22, is more precise, but less widely applicable,
Ash, % 5 ~A/B! 3 100
than the method described in Sections 24 to 26.
where:
18. Significance and Use
A = ash, g, and
18.1 Acetyl or acetic acid content is a measure of the
B = sample used, g.
amount of acetic acid esterified onto the cellulose backbone of
11. Precision and Bias the polymer. The amount of substitution of acetate ester has a
very strong effect on the polymer’s solubility and physical
11.1 No statement on bias can be made as no reference
properties.
material is available as a standard.
Test Method A—Solution Method
FREE ACIDITY
12. Significance and Use
19. Apparatus
12.1 Free Acidity is a measure of unesterified organic acid
19.1 Weighing Bottle, glass-stoppered, 15-mL capacity,
in the ester. The presence of high levels of free acid is
25-mm diameter by 50-mm high.
potentially detrimental to the melt processing of the ester and
19.2 Tray, copper or aluminum, approximately 5 ⁄8in.
can impact the odor of the ester.
(136.5 mm) square, containing 25 compartments 1 in. (25.4
mm) square. Each compartment shall have the correct dimen-
13. Reagents
sions to contain one weighing bottle. The entire tray shall fit
13.1 Phenolphthalein Indicator Solution (1 g/100 mL)— inside a desiccator and should have a basket-type handle to
Dissolve1gof phenolphthalein in 100 mL of ethyl alcohol
facilitate the introduction and removal of the tray (convenient
(95 %). but not essential).
13.2 Sodium Hydroxide, Standard Solution (0.01 N)—
19.3 Buret, automatic zero, 35-mL, 25-mL bulb, stem
Prepare and standardize a 0.01 N solution of sodium hydroxide graduated from 25 to 35 mL in 0.05-ml increments; or pipet,
(NaOH).
automatic zero, 30-mL, for 1.0 N NaOH solution.
19.4 Buret, automatic zero, 15-mL, 10-mL bulb, stem
14. Procedure
graduated from 10 to 15 mL in 0.05-mL increments, for 1 N
14.1 Shake5gofthe sample, ground to pass a No. 20 (850 H SO .
2 4
μm) sieve and corrected for moisture content if necessary, in a 19.5 Buret, 5-ml, in 0.01 or 0.1-mL divisions, for back
250-mL Erlenmeyer flask with 150 mL of freshly boiled, cold titration with 0.1 N NaOH solution.
water. Stopper the flask and allow it to stand for 3 h. Filter off 19.6 Magnetic Stirrer, for single flask.
the cellulose acetate and wash it with water. Titrate the 19.7 Magnetic Stirrer, capacity twelve or more flasks.
combined filtrate and washings with 0.01 N NaOH solution, 19.8 Stirring Bars, stainless steel Type 416, length 50 mm,
using phenolphthalein indicator solution. diameter 5 to 6 mm, or equivalent, dimensions not critical.
D871–96
20. Reagents agitation that will not splash the solution is recommended.
When solution appears to be complete, add 50 mL of acetone
20.1 Acetone—Add one 30-mL portion of 1.0 N NaOH
and swirl or stir for 5 min. Proceed in accordance with 21.4.
solution to a mixture of 150 mL acetone and 100 mL hot water,
21.3.2 Dimethyl sulfoxide is the preferred solvent, but if it
allow to stand with frequent swirling for 30 min, and titrate
is not available, spread the sample in a thin layer over the
with 1.0 N H SO . Add another 30-mL portion of 1.0 N NaOH
2 4
bottom of the flask, add 15 mL of acetone, swirl to wet the
solution to 100 mL of hot water, allow to stand for 30 min, and
particles with acetone, stopper the flask, and allow the mixture
titrate. The difference between the two titrations shall not
to stand undisturbed for 20 min. Add 75 mL of pyridine
exceed 0.05 mL.
without shaking or swirling, and allow to stand for 10 min.
20.2 Dimethyl Sulfoxide.
Heat the solution just to boiling and swirl or stir for 5 min.
20.3 Pyridine.
Again heat to boiling and swirl or stir for 10 min. Continue to
20.4 Sodium Hydroxide Solution (40 g/L)—Dissolve 40 g of
heat and stir until the mixture is homogeneous and all large gel
sodium hydroxide (NaOH) in water and dilute to 1 L.
masses are broken down into individual highly swollen par-
20.5 Sodium Hydroxide, Standard Solution (0.1 N)—
ticles. When these highly swollen gel particles are well
Prepare and standardize a 0.1 N solution of NaOH.
dispersed and are not fused together in large gel masses, no
20.6 Sulfuric Acid (1.0 N)—Prepare and standardize a 1.0
further heating is necessary. Cool the flask, add 30 mL of
N solution of sulfuric acid (H SO ).
2 4
acetone, and swirl or stir for 5 min. Proceed in accordance with
20.7 Phenolphthalein Indicator Solution (1 g/100 mL)—
21.4.
Dissolve1gof phenolphthalein in 100 ml of ethyl alcohol
21.4 Add 30 mL of NaOH solution (40 g/L) with constant
(95 %).
swirling or stirring to the solution of the sample and also to the
blank. Use of a magnetic stirrer is recommended (Note 2). It is
21. Procedure
absolutely necessary that a finely divided precipitate of regen-
21.1 Dry 1.9 6 0.05 g of the ground well-mixed sample in
erated cellulose, free from lumps, be obtained. Stopper the
a weighing bottle for2hat105 6 3°C and weigh the dried
flask and let the mixture stand with occasional swirling, or stir
sample by difference to the nearest 1 mg into a 500-mL
on the magnetic stirring unit. Allow 30 min for saponification
wide-mouth Erlenmeyer flask. Prepare a blank by drying
of lower acetyl samples, 2 h for high acetyl samples when
approximately 3.8 g of potassium acid phthalate and weighing
dimethyl sulfoxide is the solvent, and 3 h when pyridine is the
it by difference into a flask as described. Carry the blank
solvent. At the end of the saponification period, add 100 mL of
through the entire procedure.
hot water, washing down the sides of the flask, and stir for 1 or
2 min. Add 4 or 5 drops of phenolphthalein indicator solution
NOTE 1—Potassium acid phthalate is used so that the concentration of
the NaOH in contact with the solvent in the blank will be approximately
and titrate the excess NaOH solution with 1.0 N H SO (Note
2 4
the same as that in contact with the sample and so that the titration of the
3). Titrate rapidly with constant swirling or stirring ring until
blank will be approximately the same as the titration of the sample, thus
the end point is reached; then add an excess of 0.2 or 0.3 mL
avoiding errors caused by using a different buret for the titration of the
of H SO . Allow the mixture to stand with occasional stirring
2 4
blank and the sample or by refilling the 15-mL buret. If desired, however,
or preferably stir on the magnetic stirrer for at least 10 min.
the potassium acid phthalate may be omitted.
Then add 3 drops of phenolphthalein indicator solution to each
21.2 If the acetyl content is 32 to 41 % or the acetic acid
flask and titrate the small excess of acid with 0.1 N NaOH
content is 45 to 57 %, put the sample into solution as follows:
solution to a persistent phenolphthalein end point. Take ex-
Add 150 mL of acetone and 5 to 10 mL of water and swirl to
treme care to locate this end point; after the sample is titrated
mix. Stopper the flask and allow it to stand with occasional
to a faint pink end point, swirl the mixture vigorously or place
swirling until solution is complete. Solution may be hastened
it for a moment on the magnetic stirrer. If the end point fades
by magnetic stirring or by any suitable mechanical shaking that
because of acid soaking from the cellulose, continue the
will provide a gentle rocking type of agitation to avoid
addition of 0.1 N NaOH solution until a faint persistent end
splashing the solution on the stopper. It is essential that
point remains after vigorous swirling or stirring. Titrate the
complete solution be effected. Proceed in accordance with
blank in the same manner as the sample.
21.4.
NOTE 2—While the amount of magnetic stirring is somewhat optional,
21.3 If the acetyl content is 41 to 44.8 % or the acetic acid
such stirring during the entire period of the determination is strongly
content is 57 to 62.5 %, dissolve the sample by either of the
recommended. Solution is more rapid, titrations are more rapid, and the
following two methods:
end point can be approached directly and without a back titration.
21.3.1 Gently rotate the flask by hand to distribute and
NOTE 3—It is important to correct all 1.0 N H SO buret readings for
2 4
spread the sample in a thin layer over the bottom of the flask.
temperature and buret corrections.
Add 70 mL of acetone to the flask and swirl gently until the
sample particles are completely wetted and evenly dispersed. 22. Calculation
Stopper the flask and allow it to stand undisturbed for 10 min.
22.1 Calculate the percentage by weight of acetyl and acetic
Carefully add 30 mL of dimethyl sulfoxide from a graduate to
acid as follows:
the flask, pouring the solvent down the sides of the flask to
Acetyl or acetic acid, % (2)
wash down any sample particles clinging
...
Questions, Comments and Discussion
Ask us and Technical Secretary will try to provide an answer. You can facilitate discussion about the standard in here.