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ASTM D792-13 用位移法测定塑料密度和比重的标准试验方法

ASTM D792-13 用位移法测定塑料密度和比重的标准试验方法

Designation:D792?13

Standard Test Methods for

Density and Speci?c Gravity(Relative Density)of Plastics by Displacement1

This standard is issued under the?xed designation D792;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.

This standard has been approved for use by agencies of the Department of Defense.

1.Scope*

1.1These test methods describe the determination of the speci?c gravity(relative density)and density of solid plastics in forms such as sheets,rods,tubes,or molded items.

1.2Two test methods are described:

1.2.1Test Method A—For testing solid plastics in water,and 1.2.2Test Method B—For testing solid plastics in liquids other than water.

1.3The values stated in SI units are to be regarded as the standard.

1.4This 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 appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.

N OTE1—This standard is not equivalent to ISO1183–1Method A.This test method provides more guidelines on sample weight and dimension. ISO1183-1allows testing at an additional temperature of2762°C. 2.Referenced Documents

2.1ASTM Standards:2

D618Practice for Conditioning Plastics for Testing

D891Test Methods for Speci?c Gravity,Apparent,of Liquid Industrial Chemicals

D4968Guide for Annual Review of Test Methods and Speci?cations for Plastics

D6436Guide for Reporting Properties for Plastics and Thermoplastic Elastomers

E1Speci?cation for ASTM Liquid-in-Glass Thermometers E12Terminology Relating to Density and Speci?c Gravity

of Solids,Liquids,and Gases(Withdrawn1996)3

E691Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method

IEEE/ASTM SI-10Practice for Use of the International System of Units(SI)(the Modernized Metric System) 3.Terminology

3.1General—The units,symbols,and abbreviations used in these test methods are in accordance with IEEE/ASTM SI-10.

3.2De?nitions:

3.2.1speci?c gravity(relative density)—the ratio of the mass of a given volume of the impermeable portion of the material at23°C to the mass of an equal volume of gas-free distilled or de-mineralized water at the same temperature;the form of expression shall be:

Specific gravity~relative density!23/23°C

~or sp gr23/23°C!

N OTE2—This de?nition is essentially equivalent to the de?nition for apparent speci?c gravity and apparent density in Terminology E12, because the small percentage difference introduced by not correcting for the buoyancy of air is insigni?cant for most purposes.

3.2.2density—cubic metre of impermeable portion of the material at23°C.The form of expression shall be:

D23,kg/m3

N OTE3—The SI unit of density,as de?ned in IEEE/ASTM SI-10,is kg/m3.To convert density in g/cm3to density in kg/m3,multiply by1000.

N OTE4—To convert speci?c gravity23/23°C to density23°C,kg/m3, use the following equation:

D23C,kg/m35sp gr23/23°C3997.5

Where997.5kg/m3is the density of water at23°C.

4.Summary of Test Method

4.1Determine the mass of a specimen of the solid plastic in air.It is then immersed in a liquid,its apparent mass upon immersion is determined,and its speci?c gravity(relative density)calculated.

1These test methods are under the jurisdiction of ASTM Committee D20on Plastics and are the direct responsibility of Subcommittee D20.70on Analytical Methods(Section D20.70.01).

Current edition approved Nov.1,2013.Published November2013.Originally approved http://www.wendangku.net/doc/355839baddccda38366baf50.htmlst previous edition approved in2008as D792-08.DOI: 10.1520/D0792-13.

2For referenced ASTM standards,visit the ASTM website,http://www.wendangku.net/doc/355839baddccda38366baf50.html,or contact ASTM Customer Service at service@http://www.wendangku.net/doc/355839baddccda38366baf50.html.For Annual Book of ASTM

Standards volume information,refer to the standard’s Document Summary page on the ASTM website.

3The last approved version of this historical standard is referenced on http://www.wendangku.net/doc/355839baddccda38366baf50.html.

*A Summary of Changes section appears at the end of this standard

Copyright?ASTM International,100Barr Harbor Drive,PO Box C700,West Conshohocken,PA19428-2959.United States

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5.Signi?cance and Use

5.1The speci?c gravity or density of a solid is a property that is conveniently measured to identify a material,to 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 material are due to localized differences in crystallinity,loss of plasticizer,absorp-tion of solvent,or to other causes.It is possible that portions of a sample differ in density because of their differences in crystallinity,thermal history,porosity,and composition(types or proportions of resin,plasticizer,pigment,or?ller).

5.3Density is useful for calculating strength-weight and cost-weight ratios.

6.Sampling

6.1The sampling units used for the determination of spe-ci?c gravity(relative density)shall be representative of the quantity of product for which the data are required.

6.1.1If it is known or suspected that the sample consists of two or more layers or sections having different speci?c gravities,either complete?nished parts or complete cross sections of the parts or shapes shall be used as the specimens, or separate specimens shall be taken and tested from each layer.The speci?c gravity(relative density)of the total part shall not be obtained by adding the speci?c 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 and50610%relative humidity for not less than40 h prior to test in accordance with Procedure A of Practice D618,unless otherwise speci?ed by the contract or relevant material speci?cations.In cases of disagreement,the tolerances shall be61°C and65%relative humidity.

7.2Test Conditions—Conduct tests in the standard labora-tory atmosphere of2362°C and50610%relative humidity, unless otherwise speci?ed in this speci?cation or by the contract or relevant material speci?cation.In cases of disagreement,the tolerances shall be61°C and65%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 otherwise not affected by water.

9.Apparatus

9.1Analytical Balance—A balance with a precision of0.1 mg or better is required for materials having densities less than 1.00g/cm3and sample weights less than10grams.For all other materials and sample weights,a balance with precision of 1mg or better is acceptable(see Note5).The balance shall be equipped with a stationary support for the immersion vessel above the balance pan(“pan straddle”).

N OTE5—The balance shall provide the precision that all materials tested have three signi?cant?gures on density.In case that materials with different densities are tested on one single balance,use the balance that provides at least three signi?cant?gures for all materials concerned.

N OTE6—To assure that the balance meets the performance requirements,check on zero point and sensitivity frequently and perform periodic calibration.

9.2Sample Holder,corrosion-resistant(for example,wire, gemholder,etc.).

9.3Sinker—A sinker for use with specimens of plastics that have speci?c gravities less than1.00.The sinker shall:(1)be corrosion-resistant;(2)have a speci?c 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 shall have an opening to facilitate attachment to the specimen and sample holder.

9.4Immersion Vessel—A beaker or other wide-mouthed vessel for holding the water and immersed specimen.

9.5Thermometer—A thermometer readable to0.1°C or better.

10.Materials

10.1Water—The water shall be substantially air-free and distilled or de-mineralized water.

N OTE7—Air in water can be removed by boiling and cooling the water, or by shaking the water under vacuum in a heavy-walled vacuum?ask. (Warning—Use gloves and shielding.)If the water does not wet the specimen,add a few drops of a wetting agent into the water.If this solution does not wet the specimen,Method B shall be used.

11.Test Specimen

11.1The test specimen shall be a single piece of material with a size and shape suitable for the testing apparatus, provided that its volume shall be not less than1cm3and its surface and edges shall be made smooth.The thickness of the specimen shall be at least1mm for each1g of weight.A specimen weighing1to5g was found to be convenient,but specimens up to approximately50g are also acceptable(see Note8).Care shall be taken in cutting specimens to avoid changes in density resulting from compressive stresses or frictional heating.

N OTE8—Speci?cations for certain plastics require a particular method of specimen preparation and should be consulted if applicable.

11.2The specimen shall be free from oil,grease,and other foreign matter.

12.Procedure

12.1Measure and record the water temperature.

12.2Weigh the specimen in air.Weigh to the nearest0.1mg for specimens of mass1to10g and density less than1.00 g/cm3.Weigh to the nearest1mg for other specimens.

12.3If necessary,attach to the balance a piece of?ne wire sufficiently long to reach from the hook above the pan to the support for the immersion vessel.In this case attach

ASTM D792-13 用位移法测定塑料密度和比重的标准试验方法

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ASTM D792-13 用位移法测定塑料密度和比重的标准试验方法

specimen to the wire such that it is suspended about 25mm above the vessel support.

N OTE 9—If a wire is used,weigh the specimen in air after hanging from the wire.In this case,record the mass of the specimen,a =(mass of specimen +wire,in air)?(mass of wire in air).

12.4Mount the immersion vessel on the support,and completely immerse the suspended specimen (and sinkers,if used)in water (see 10.1)at a temperature of 2362°C.The vessel must not touch sample holder or specimen.Remove any bubbles adhering to the specimen,sample holder,or sinker,by rubbing them with a wire.Pay particular attention to holes in the specimen and sinker.If the bubbles are not removed by this method or if bubbles are continuously formed (as from dissolved gases),the use of vacuum is recommended (see Note 10).Determine the mass of the suspended specimen to the required precision (see 12.2)(see Note 11).Record this apparent mass as b (the mass of the specimen,sinker,if used,and the partially immersed wire in liquid).Unless otherwise speci?ed,weigh rapidly in order to minimize absorption of water by the specimen.

N OTE 10—Some specimens may contain absorbed or dissolved gases,or irregularities which tend to trap air bubbles;any of these may affect the density values obtained.In such cases,the immersed specimen may be subjected to vacuum in a separate vessel until evolution of bubbles has substantially ceased before weighing (see Test Method B).It must also be demonstrated that the use of this technique leads to results of the required degree of precision.

N OTE 11—It may be necessary to change the sensitivity adjustment of the balance to overcome the damping effect of the immersed specimen.

12.5Weigh the sample holder (and sinker,if used)in water with immersion to the same depth as used in the previous step (Notes 12and 13).Record this weight as w (mass of the sample holder in liquid).

N OTE 12—If a wire is used,it is convenient to mark the level of immersion by means of a shallow notch ?led in the wire.The ?ner the wire,the greater the tolerance is permitted in adjusting the level of immersion between weighings.With wire Awg No.36or ?ner,disregard its degrees of immersion and,if no sinker is used,use the mass of the wire in air as w.

N OTE 13—If the wire is used and is left attached to the balance arm during a series of determinations,determine the mass a with the aid of a tare on the other arm of the balance or as in Note 9.In such cases,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 http://www.wendangku.net/doc/355839baddccda38366baf50.htmle additional specimens if desired.13.Calculation

13.1Calculate the speci?c gravity of the plastic as follows:

sp gr 23/23°C 5a /~a 1w 2b !

where:

a =apparent mass of specimen,without wire or sinker,in

air,

b =apparent mass of specimen (and of sinker,if used)

completely immersed and of the wire partially immersed in liquid,and

w =apparent mass of totally immersed sinker (if used)and

of partially immersed wire.13.2Calculate the density of the plastic as follows:

D 23C ,kg/m 35sp gr 23/23°C 3997.5

13.3If the temperature of the water is different than 23°C,use the density of water listed in Table 3directly,or use the following equations to calculate the density of water at testing temperature:

M 5?D /?t

(1)D ~conversion to 23°C !,kg/m 3

(2)

5sp gr t a /t w 3@997.51~t w 223!3M #and

sp gr 23/235D ~conversion to 23°C !/997.5

(3)

where:

M =slope,

?D =difference between the lowest and highest temperature

tolerance for the standard density of water (D @21°C –D @25°C),

?t =difference between the highest and lowest temperature

tolerance recommended,(21°C–25°C),t a

=temperature of air,and t w =temperature of water.14.Report

14.1Report the following information:

14.1.1Complete identi?cation of the material or product tested,including method of specimen preparation and conditioning,

14.1.2Average speci?c gravity (relative density)for all specimens from a sampling unit corrected to 23.0°C (Table 3)

TABLE 1Test Method A Speci?c Gravity Tested in Water

Material

Mean S r A S R B r C R D Polypropylene

0.90070.001960.002970.005550.00841Cellulose Acetate Butyrate 1.19730.002320.003040.006570.00860Polyphenylene Sul?de 1.17080.005400.007380.015280.02089Thermoset

1.31360.002710.003130.007670.02171Polyvinyl Chloride

1.3396

0.00243

0.00615

0.00688

0.01947

A

S r =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 =[[(s 1)2+(s 2)2...+(s n )2]/n]1/2

B

S R =between-laboratories reproducibility,expressed as standard deviation:S R =[S r 2+S L 2]1/2where S L is the standard deviation of laboratory means.C

r =within-laboratory critical interval between two test results =2.8×S r .D

R =between-laboratories critical interval between two test results =2.8×S R

.

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are reported as sp gr 23/23°C =___,or average density reported as D 23C =___kg/m 3,

N OTE 14—Reporting density in g/cm 3is also acceptable provided that it is agreed upon by the users.

14.1.3A measure of the degree of variation of speci?c gravity or density within the sampling unit such as the standard deviation and number of determinations on a homogeneous material or the averages plus these measures of dispersion on different layers or areas of a nonhomogeneous product,14.1.4Report the temperature of the water.

14.1.5Report the density and speci?c gravity with three signi?cant ?gures.

14.1.6Any evidence of porosity of the material or specimen,

14.1.7The method of test (that is,Method A of Test Method D792),and

14.1.8Date of test.15.Precision and Bias 15.1See Section 23.

TEST METHOD B FOR TESTING SOLID PLASTICS IN LIQUIDS OTHER THAN WATER (SPECIMENS 1

TO 50g)16.Scope

16.1Test Method B uses a liquid other than water for testing one-piece specimens,1to 50g,of plastics that are affected by water or are lighter than water.17.Apparatus

17.1The apparatus shall include the balance,wire,and immersion vessel of Section 8,and,optionally,the following:17.2Pycnometer with Thermometer—A 25-mL speci?c 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 ten divisions per degree Celsius over a temperature range of not less than 5°C or 10°F above and below the standard temperature,and having an ice point for calibration.A thermometer short enough to be handled inside the balance case will be found convenient.ASTM Thermometer 23C (see Speci?cation E1)and Anschütz-type thermometers have been found satisfactory for this purpose.

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 used shall not dissolve,swell,or otherwise affect the specimen,but shall wet it and shall have a speci?c gravity less than that of the specimen.In addition,the immersion liquid shall be non-hygroscopic,has a low vapor pressure,a low viscosity,and a high ?ash point,and shall leave little or no waxy or tarry residue on evaporation.A narrow cut distilled from kerosine meets these requirements for many plastics.The speci?c gravity 23/23°C of the immersion liquid shall be determined shortly before and after each use in this method to a precision of at least 0.1%relative,unless it has been established experimentally in the particular applica-tion that a lesser frequency of determination also provides the desired precision.

N OTE 15—For the determination of the speci?c gravity of the liquid,the use of a standard plummet of known volume or of Method A,C,or D of Test Methods D891,using the modi?cations required to give speci?c gravity 23/23°C instead of speci?c gravity 60/60°F,is recommended.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

TABLE 2Test Method B Speci?c Gravity Tested in Liquids Other Than Water

Material Mean S r A S R B r C R D Polypropylene 0.90230.001390.002390.003930.00669LDPE 0.92150.001090.001950.003080.00546HDPE

0.96780.001260.001890.003560.00529Thermoset

1.3130

0.00160

0.00217

0.00453

0.00608

A

S r =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 =[[(s 1)2+(s 2)2...+(s n )2]/n]1/2

B

S R =between-laboratories reproducibility,expressed as standard deviation:S R =[S r 2+S L 2]1/2where S L is the standard deviation of laboratory means.C

r =within-laboratory critical interval between two test results =2.8×S r .D

R =between-laboratories critical interval between two test results =2.8×S R .

TABLE 3Standard Density of Water A

°C ρ=/kg m –3

0.00.10.20.30.40.50.60.70.80.921997.994897319513929490738852863084068182795722997.773075037275704568156584635161185883564823997.541251744936469744564215397337303485324024997.299427472499225020001749149712440990073525

997.0480

0223

9965B

9707B

9447B

9186B

8925B

8663B

8399B

8135B

A Obtained from CRC Handbook of Chemistry and Physics ,78th

ASTM D792-13 用位移法测定塑料密度和比重的标准试验方法

edition,1997-1998.B

The leading ?gure decreases by 1.

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to the nearest0.1mg on an analytical balance.Fill the pycnometer with water(10.1)cooler than23°C.Insert the thermometer-stopper,causing excess water to be expelled through the side arm.Permit the?lled bottle to warm in air until the thermometer reads23.0°C.Remove the drop of water at the tip of the side arm with a bit of?lter 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?lled bottle again to the nearest0.2mg.Empty the pycnometer,dry,and?ll with immersion liquid.Determine the mass with the liquid in the same manner as was done with the water.Calculate the speci?c gravity23/23°C of the liquid,d,as follows:

d5~b2e!/~w2e!

where:

e=apparent mass of empty pycnometer,

w=apparent mass of pycnometer?lled with water at

23.0°C,and

b=apparent mass of pycnometer?lled with liquid at

23.0°C.

If a constant-temperature water bath is available,a pycnom-eter without a thermometer may be used(compare30.2).

N OTE16—One standard object which has been found satisfactory for this purpose is the Reimann Thermometer Plummet.These are normally supplied calibrated for measurements at temperatures other than23/23°C, so that recalibration is not necessary for the purposes of these methods.

19.Test Specimen

19.1See Section11.

20.Procedure

20.1The procedure shall be similar to Section12,except for the choice of immersion liquid,and the temperature during the immersed weighing(12.3)shall be2360.5°C.

21.Calculation

21.1The calculations shall be similar to Section13,except that d,the speci?c gravity23/23°C of the liquid,shall be placed in the numerator:(see13.1)

Sp gr23/23°C5~a3d!/~a1w2b!

22.Report

22.1See Section14.23.Precision and Bias

23.1Tables1and2are based on an interlaboratory study4 conducted in1985in accordance with Practice E691,involving 5materials tested with Test Method A by six laboratories or four materials tested with Test Method B by six laboratories. Each test result was based on two individual determinations and each laboratory obtained four test results for each material. (Warning—The explanations of r and R are only intended to present a meaningful way of considering the approximate precision of these test methods.The data of Tables1and2 should not be applied to acceptance or rejection of materials,as these data apply only to the materials tested in the round robin and are unlikely to be rigorously representative of other lots, formulations,conditions,materials,or http://www.wendangku.net/doc/355839baddccda38366baf50.htmlers of this test method should apply the principles outlined in Practice E691to generate data speci?c to the materials and laboratory (or between speci?c laboratories).The principles of23.2–23.2.3would then be valid for such data.)

23.2Concept of r and R in Tables1and2—If S r and S R have been calculated from a large enough body of data,and for test results that were averages from4test results for each material,then:

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 representing 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 representing 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 with23.2.1or23.2.2 would have an approximate95%(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;speci?c gravity

4Supporting data have been?led at ASTM International Headquarters and may be obtained by requesting Research Report

ASTM D792-13 用位移法测定塑料密度和比重的标准试验方法

RR:D20-1133. --``,`````,``,``,`,,`,,```````,,-`-`,,`,,`,`,,`---

ASTM D792-13 用位移法测定塑料密度和比重的标准试验方法

SUMMARY OF CHANGES

Committee D20has identi?ed the location of selected changes to this standard since the last issue (D792-08)that may impact the use of this standard.(November 1,2013)

(1)Revised 7.1and 7.2.

ASTM International takes no position respecting the validity of any patent rights asserted in connection with any item mentioned in this http://www.wendangku.net/doc/355839baddccda38366baf50.htmlers of this standard are expressly advised 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 ?ve years and if not revised,either reapproved or withdrawn.Your comments are invited either for revision of this standard or for additional standards and should be addressed to ASTM International 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 International,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 service@http://www.wendangku.net/doc/355839baddccda38366baf50.html (e-mail);or through the ASTM website (http://www.wendangku.net/doc/355839baddccda38366baf50.html).Permission rights to photocopy the standard may also be secured from the ASTM website (http://www.wendangku.net/doc/355839baddccda38366baf50.html/COPYRIGHT/).

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