follow physical changes in a sample,to indicate degree of uniformity among different sampling units or specimens,or to indicate the average density of a large item.
5.2Changes in density of a single specimen may be due to changes in crystallinity,loss of plasticizer,absorption of solvent,or to other caus.Portions of a sample may differ in density becau of difference in crystallinity,thermal history, porosity,and composition(types or proportions of resin, plasticizer,pigment,orfiller).
N OTE6—Reference is made to Test Method D1622.
5.3Density is uful for calculating strength-weight and cost-weight ratios.
6.Sampling
6.1The sampling units ud for the determination of spe-cific gravity(relative density)shall be reprent
ative of the quantity of product for which the data are required,in accordance with Practice D1898.
6.1.1If it is known or suspected that the sample consists of two or more layers or ctions having different specific gravities,either completefinished parts or complete cross ctions of the parts or shapes shall be ud as the specimens, or parate specimens shall be taken and tested from each layer.The specific gravity(relative density)of the total part cannot be obtained by adding the specific gravity of the layers, unless relative percentages of the layers are taken into account.
7.Conditioning
7.1Conditioning—Condition the test specimens at 2362°C and5065%relative humidity for not less than40 h prior to test in accordance with Procedure A of Practice D618,for tho tests where conditioning is required.In cas of disagreement,the tolerances shall be1°C and62%relative humidity.
7.2Test Conditions—Conduct tests in the standard labora-tory atmosphere of2362°C and5065%relative humidity, unless otherwi specified in the test methods or in this specification.In cas of disagreement,the tolerances shall be 1°C and62%relative humidity.
TEST METHOD A FOR TESTING SOLID PLASTICS IN WATER(SPECIMENS1TO50g)
8.Scope
8.1This test method involves weighing a one-piece speci-men of1to50g in water,using a sinker with plastics that are lighter than water.This test method is suitable for plastics that are wet by,but otherwi not affected by water.
9.Apparatus
9.1Analytical Balance—A balance with a precision within 0.1mg,accuracy within0.05%relative(that is,0.05%of the mass of the specimen in air),and equipped with a stationary support for the immersion vesl above the balance pan(“pan straddle”).
N OTE7—Assurance that the balance meets the performance require-ments should be provided by frequent checks on adjustments of zero point and nsitivity and by periodic calibration for absolute accuracy,using standard mass.
9.2Sample Holder,corrosion-resistant.
9.3Sinker—A sinker for u with specimens of plastics that have specific gravities less than1.000.The sinker shall:(1)be corrosion-resistant;(2)have a specific gravity of not less than 7.0;(3)
have smooth surfaces and a regular shape;and(4)be slightly heavier than necessary to sink the specimen.The sinker should have an opening to facilitate attachment to the specimen and wire.四级英语报名
9.4Immersion Vesl—A beaker or other wide-mouthed vesl for holding the water and immerd specimen.
9.5Thermometer—A thermometer with an accuracy of 61°C is required if the test is not performed in the standard laboratory atmosphere of Practice D618,(refer to17.4). 10.Materials
10.1Water—The water shall be substantially air-free and distilled or demineralized water.
N OTE8—Water may be rendered substantially air-free by boiling and cooling or by shaking under vacuum in a heavy-walled vacuumflask. (Precaution:U gloves and shielding.)If the water does not wet the specimen,a few drops of a wetting agent shall be added.If this solution does not wet the specimen,Method B shall be ud.
11.Test Specimen
11.1The test specimen shall be a single piece of the material under test of any size and shape that can conveniently be prepared and tested,provided that its volume shall be not less than1cm3and its
surface and edges shall be made smooth.The thickness of the specimen should be at least1mm for each1 g of weight.A specimen weighing1to5g usually will be found convenient,but specimens up to approximately50g may be ud(Note9).Care should be taken in cutting specimens to avoid changes in density resulting from compressive stress or frictional heating.
N OTE9—Specifications for certain plastics require a particular method of specimen preparation and should be consulted if applicable.
11.2The specimen shall be free from oil,grea,and other foreign matter.
12.Procedure
12.1Measure and record the water temperature.
12.2Weigh the specimen in air to the nearest0.1mg for specimens of mass1to10g or to the nearest mg for specimens of mass more than10to50g.
scapegoat12.3Attach to the balance a piece offine wire sufficiently long to reach from the hook above the pan to the support for the immersion vesl.Attach the specimen to the wire such that it is suspended about25mm above the vesl support.
N OTE10—The specimen may be weighed in air after hanging from the wire.In this ca,record the mass of the specimen,a5(mass of specimen+wire,in air)−(mass of wire in air).
12.4Mount the immersion vesl on the support,and completely immer the suspended specimen(and sinkers,if ud)in water(10.1)at a temperature of2362°C.The vesl must not touch wire or specimen.Remove any bubbles adhering to the specimen,wire,or sinker,paying particular attention to holes in the specimen and sinker.Usually the bubbles can be removed by rubbing them with another wire.
If
the bubbles cannot be removed by this method or if bubbles are
continuously formed (as from dissolved gas),the u of
vacuum is recommended (Note 12).Determine the mass of the
suspended specimen to the required precision (12.2)(Note 11).
Record this apparent mass as b (the mass of the specimen,
哒哒英语收费sinker,if ud,and the partially immerd wire in liquid).
Unless otherwi specified,weigh rapidly in order to minimize
absorption of water by the specimen.
N OTE 11—It may be necessary to change the nsitivity adjustment of
the balance to overcome the damping effect of the immerd specimen.
N OTE 12—Some specimens may contain absorbed or dissolved gas,
or irregularities which tend to trap air bubbles;any of the may affect the
density values obtained.In such cas,the immerd specimen may be
subjected to vacuum in a parate vesl until evolution of bubbles has
substantially cead before weighing (e Test Method B).It must also be
demonstrated that the u of this technique leads to results of the required
degree of precision.12.5Weigh the wire (and sinker,if ud)in water with immersion to the same depth as ud in the previous step (Notes 13and 14).Record this height as w (mass of the wire in liquid).N OTE 13—It is convenient to mark the level of immersion by means of a shallow notch filed in the wire.The finer the wire,the greater the tolerance which may be permitted in adjusting the level of immersion between weighings.With wire Awg No.36or finer,disregard its degrees of immersion and,if no sinker is ud,u the mass of the wire in air as w.N OTE 14—If the wire is left attached to the balance arm during a ries of determinations,the mass a may be determined either with the aid of a tare on the other arm of the balance or as in Note 12.In such cas,care must be taken that the change of mass of the wire (for example,from visible water)between readings does not exceed the desired precision.12.6Repeat the procedure for the required number of specimens.Two specimens per sample are recommended.Determine acceptability of number of replicate test specimens by comparing results with precision data given in Tables 1and 2of Section 23.Additional specimens may
be required to give the desired precision.13.Calculation 13.1Calculate the specific gravity of the plastic as follows:Sp gr 23/23°C 5a/~a 1w 2b !
where:a 5apparent mass of specimen,without wire or sinker,in air,b 5apparent mass of specimen (and of sinker,if ud)completely immerd and of the wire partially im-merd in liquid,and w 5apparent mass of totally immerd sinker (if ud)and of partially immerd wire.13.2Calculate the density of the plastic as follows:D 23C ,kg/m 35sp gr 23/23°C 3997.614.Report 14.1Report the following information:14.1.1Complete identification of the material or product tested,including method of specimen preparation and condi-tioning,14.1.2Average specific gravity (relative density)for all
specimens from a sampling unit,reported as sp gr 23/
23°C 5___,or average density reported as D 23C 5___kg/m 3,
14.1.3A measure of the degree of variation of specific
gravity or density within the sampling unit such as the standard
deviation and number of determinations on a homogeneous
material or the averages plus the measures of dispersion on
different layers or areas of a nonhomogeneous product,
14.1.4Report the temperature of the water.
14.1.5Any evidence of porosity of the material or speci-
men,
14.1.6The method of test (Method A of Methods D 792),
and
14.1.7Date of test.
15.Precision and Bias
15.1See Section 23.
mba报考要求TEST METHOD B FOR TESTING SOLID PLASTICS
IN LIQUIDS OTHER THAN WATER (SPECIMENS 1
TO 50g)
16.Scope
16.1Test Method B us a liquid other than water for testing
one-piece specimens,1to 50g,of plastics that are affected by
water or which are lighter than water.
17.Apparatus
17.1The apparatus shall include the balance,wire,and
immersion vesl of Section 8,and,optionally,the following:TABLE 1Test Method A
Specific Gravity Tested in Water Material
Mean S r A S R B r C R D Polypropylene
0.90070.001960.002970.005550.00841Cellulo Acetate Butyrate
1.19730.002320.003040.006570.00860Polyphenylene Sulfide
1.17080.005400.007380.015280.02089Thermot
1.31360.002710.003130.007670.02171Polyvinyl Chloride
1.33960.002430.006150.006880.01947A S r is the within laboratory standard deviation for the individual material.It is obtained by pooling the within-laboratory standard deviations of the test results from all of the participating laboratories:
S r 5[[(s 1)2+(s +(s n )2]/n]1/2
B S R is the between-laboratories reproducibility,expresd as standard deviation:S R 5[S r 2+S L 2]1/2where S L is the standard deviation of laboratory means.
C r is the within-laboratory critical interval between two test results 52.83S r .
D R is the between-laboratories critical interval between two test results 52.83S R
.
17.2Pycnometer with Thermometer —A 25-mL specific
gravity bottle with thermometer,or
17.3Pycnometer —A pycnometer of the Weld type,prefer-
ably with a capacity of about 25mL and an external cap over
the stopper.
17.4Thermometer —A thermometer having not fewer than
four divisions per °C over a temperature range of not less than
5°C or 10°F above and below the standard temperature,and
efficienthaving an ice point for calibration.A thermometer short
enough to be handled inside the balance ca will be found
convenient.ASTM Thermometer 23C (e Specification E 1)tag什么意思
and Anschütz-type thermometers have been found satisfactory
for this purpo.
17.5Constant-Temperature Bath —An appropriate constant-
temperature bath adjusted to maintain a temperature of
2360.1°C.
18.Materials
18.1Immersion Liquid —The liquid ud shall not dissolve,
swell,or otherwi affect the specimen,but should wet it and
should have a specific gravity less than that of the specimen.In
addition,the immersion liquid should be nonhygroscopic,have
a low vapor pressure,a low viscosity,and a high flash point,
and should leave little or no waxy or tarry residue on
evaporation.A narrow cut distilled from kerosine meets the
requirements for many plastics.The specific gravity 23/23°C
of the immersion liquid shall be determined shortly before and
after each u in this method to a precision of at least 0.1%
relative,unless it has been established experimentally in the
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particular application that a lesr frequency of determination
can be ud to assure the desired precision.
N OTE 15—For the determination of the specific gravity of the liquid,the
u of a standard plummet of known volume (Note 15)or of Method A,
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音乐专业美国留学C,or D of Test Methods D 891,using the modifications required to give
specific gravity 23/23°C instead of specific gravity 60/60°F,is recom-
mended.One suggested procedure is the following:
If a constant-temperature water bath is not available,deter-
mine the mass of the clean,dry pycnometer with thermometer
to the nearest 0.1mg on an analytical balance.Fill the
pycnometer with water (10.1)cooler than 23°C.Inrt the
thermometer-stopper,causing excess water to be expelled
through the side arm.Permit the filled bottle to warm in air
until the thermometer reads 23.0°C.Remove the drop of water
at the tip of the side arm with a bit of filter paper,taking care
not to draw any liquid from within the capillary,place the cap
over the side arm,wipe the outside carefully,and determine the
mass of the filled bottle again to the nearest 0.2mg.Empty the pycnometer,dry,and fill and determine the mass with the other liquid in the same manner as was done with the water.Calculate the specific gravity 23/23°C of the liquid,d,as follows:d 5~b 2e !/~w 2e !where:e 5apparent mass of empty pycnometer,w 5apparent mass of pycnometer filled with water at 23.0°C,and b 5apparent mass of pycnometer filled with liquid at 23.0°C.If a constant-temperature water bath is available,a pycnom-eter without a thermometer may be ud (compare 30.2).N OTE 16—One standard object which has been found satisfactory for this purpo is the Reimann Thermometer Plummet.The are normally supplied calibrated for measurements at temperatures other than 23/23°C,so that recalibration is necessary for the purpos of the methods.19.Test Specimen 19.1See Section 11.20.Procedure 20.1The procedure shall be similar to Section 12,except for the choice of immersion liquid,and the temperature during the immerd weighing (12.3)shall be 2360.5°C.21.Calculation 21.1The calculations shall be similar to Section 13,except that d,the specific gravity 23/23°C of the liquid,shall be placed in the numerator:Sp gr 23/23°C 5~a 3d /~a 1w 2b !22.Report 22.1See Section 14.23.Precision and Bias 23.1Tables 1and 2are bad on an interlaboratory study 7conducted in 1985in accordance with Practice E 691,involv-ing 5materials tested with Test Method A by 6laborator
ies or 4materials tested with Test Method B by 6laboratories.Each test result was bad on two individual determinations and each laboratory obtained four test results for each material.7Supporting data are available from ASTM Headquarters.Request RR:D20-
1133.
TABLE 2Test Method B Specific Gravity Tested in Liquids Other Than Water
Material
Mean S r A S R B r C R D Polypropylene
0.90230.001390.002390.003930.00676LDPE
0.92150.001090.001950.003080.00552HDPE
0.96780.001260.001890.003560.01007Thermot
1.31300.001600.002170.004530.01282A S r is the within laboratory standard deviation for the individual material.It is obtained by pooling the within-laboratory standard deviations of the test results from all of the participating laboratories:
S r 5[[(s 1)2+(s +(s n )2]/n]1/2
B S R is the between-laboratories reproducibility,expresd as standard deviation:S R 5[S r 2+S L 2]1/2where S L is the standard deviation of laboratory means.
C r is the within-laboratory critical interval between two test results 52.83S r .
D R is the between-laboratories critical interval between two test results 52.83S R
.
N OTE 17—Caution:The explanations of r and R are only intended to
prent a meaningful way of considering the approximate precision of
the test methods.The data of Tables 1and 2should not be applied to
acceptance or rejection of materials,as the data apply only to the
materials tested in the round robin and are unlikely to be rigorously
reprentative of other lots,formulations,conditions,materials,or labo-
ratories.Urs of this test method should apply the principles outlined in
Practice E 691to generate data specific to the materials and laboratory (or
between specific laboratories).The principles of 23.2-23.2.3would then
be valid for such data.
23.2Concept of r and R in Tables 1and 2—If S r and S R have been calculated from a large enough body of data,and for
test results that were averages from 4test results for each
material,then:
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23.2.1Repeatability —Two test results obtained within one
laboratory shall be judged not equivalent if they differ by more
than the r value for that material.The concept r is the interval
reprenting the critical difference between two test results for the same material,obtained by the same operator using the same equipment on the same day in the same laboratory.23.2.2Reproducibility —Two test results obtained by differ-ent laboratories shall be judged not equivalent if they differ by more than the R value for that material.The concept R is the interval reprenting the critical difference between two test results for the same material,obtained by different operators using different equipment in different laboratories.23.2.3Any judgment in accordance with 23.2.1or 23.2.2would have an approximate 95%(0.95)probability of being correct.23.3There are no recognized standards by which to esti-mate bias of this test method.24.Keywords 24.1density;relative density;specific gravity
SUMMARY OF CHANGES
Committee D-20has identified the location of lected changes to the test methods since the last issue that may impact the u of the test methods.
D 792–98:
(1)An ISO equivalency statement (Note 2)was added and
subquent notes were renumbered.
(2)Practice E 380was added to the text.
(3)Paragraph 9.2was revid to include the identification of a
sample holder.(4)“And”was added to 10.1.(5)Paragraphs 12.1and 14.1.4were added and subquent paragraphs were renumbered.(6)“I r ”and I R were changed to “r ”and “R ”in Tables 1and 2.(7)Section 23was rewritten.
The American Society for Testing and Materials takes no position respecting the validity of any patent rights asrted in connection with any item mentioned in this standard.Urs of this standard are expressly advid that determination of the validity of any such patent rights,and the risk of 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 and if not revid,either reapproved or withdrawn.Your comments are invited either for revision of this standard or for additional standards and should be addresd to AS
TM Headquarters.Your comments will receive careful consideration at a meeting of the responsible technical committee,which you may attend.If you feel that your comments have not received a fair hearing you should make your views known to the ASTM Committee on Standards,at the address shown below.
This standard is copyrighted by ASTM,100Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959,United States.Individual reprints (single or multiple copies)of this standard may be obtained by contacting ASTM at the above address or at 610-832-9585(phone),610-832-9555(fax),or rvice@astm (e-mail);or through the ASTM website
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