Designation:D570–98(Reapproved2005)
Standard Test Method for
which从句
Water Absorption of Plastics1
This standard is issued under thefixed designation D570;the number immediately following the designation indicates the year of original adoption or,in the ca of revision,the year of last revision.A number in parenthes indicates the year of last reapproval.A superscript epsilon(e)indicates an editorial change since the last revision or reapproval.
1.Scope
1.1This test method covers the determination of the relative rate of absorption of water by plastics when immerd.This test method is intended to apply to the testing of all types of plastics,including cast,hot-molded,and cold-molded resinous products,and both homogeneous and laminated plastics in rod and tube form and in sheets0.13mm[0.005in.]or greater in thickness.
1.2The values given in SI units are to be regarded as standard.The values stated in brackets are for information only.
1.3This standard does not purport to address all of the safety concerns,if any,associated with its u.It is the responsibility of the ur of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to u.
N OTE1—ISO62is technically equivalent to this test method.
2.Referenced Documents
2.1ASTM Standards:
D647Practice for Design of Molds for Test Specimens of Plastic Molding Materials2
2.2ISO Standard:
ISO62Plastics—Determination of Water Absorption3
3.Significance and U
3.1This test method for rate of water absorption has two chief functions:first,as a guide to the proportion of water absorbed by a material and conquently,in tho cas where the relationships between moisture and electrical or mechanical properties,dimensions,or appearance have been determined, as a guide to the effects of exposure to water or humid conditions on such properties;and cond,as a control test on the uniformity of a product.This cond function is particu-larly applicable to sheet,rod,and tube arms when the test is made on thefinished product.
3.2Comparison of water absorption values of various plas-tics can be made on the basis of values obtained in accordance with7.1and7.
4.
3.3Ideal diffusion of liquids4into polymers is a function of the square root of immersion time.Time to saturation is strongly dependent on specimen thickness.For example,Table 1shows the time to approximate time saturation for various thickness of nylon-6.
3.4The moisture content of a plastic is very intimately related to such properties as electrical insulation resistance, dielectric loss,mechanical strength,appearance,and dimen-sions.The effect upon the properties of change in moisture content due to water absorption depends largely on the type of exposure(by immersion in water or by exposure to high humidity),shape of the part,and inherent properties of the plastic.With nonhomogeneous materials,such as laminated forms,the rate of water absorption may be widely different through each edge and surface.Even for otherwi homoge-neous materials,it may be slightly greater through cut edges than through molded surfaces.Conquently,attempts to correlate water absorption with the surface area must generally be limited to cloly related materials and to similarly shaped specimens:For materials of widely varying density,relation between water-absorption values on a volume as well as a weight basis may need to be considered.
4.Apparatus
4.1Balance—An analytical balance capable of reading 0.0001g.
叙事文
4.2Oven,capable of maintaining uniform temperatures of 5063°C[1226
5.4°F]and of105to110°C[221to230°F].
5.Test Specimen
5.1The test specimen for molded plastics shall be in the form of a disk50.8mm[2in.]in diameter and3.2mm[1⁄8in.] in thickness(e Note2).Permissible variations in thickness are60.18mm[60.007in.]for hot-molded and60.30mm [60.012in.]for cold-molded or cast materials.
1This test method is under the jurisdiction of ASTM Committee D20on Plastics
and is the direct responsibility of Subcommittee D20.50on Durability of Plastics.
Current edition approved Nov.1,2005.Published January2006.Originally approved in1940.Last previous edition approved in1998as D570-98.
2Withdrawn.
3Available from American National Standards Institute(ANSI),25W.43rd St., 4th Floor,New York,NY10036.
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4Additional information regarding diffusion of liquids in polymers can be found in the following references:(1)Diffusion,Mass Transfer in Fluid Systems,E.L. Cussler,Cambridge University Press,19
85,ISBN0-521-29846-6,(2)Diffusion in Polymers,J.Crank and G.S.Park,Academic Press,1968,and(3)“Permeation, Diffusion,and Sorption of Gas and Vapors,”R.M.Felder and G.S.Huvard,in Methods of Experimental Physics,V ol16C,1980,Academic Press.
Copyright©ASTM International,100Barr Harbor Drive,PO Box C700,West Conshohocken,PA19428-2959,United States.
N OTE 2—The disk mold prescribed in the Molds for Disk Test Specimens Section of Practice D 647is suitable for molding disk test specimens of thermotting materials but not thermoplastic materials.
5.2ISO Standard Specimen —The test specimen for homo-geneous plastics shall be 60by 60by 1mm.Tolerance for the 60-mm dimension is 62mm and 60.05mm for the 1-mm thickness.This test method and ISO 62are technically equiva-lent when the test specimen described in 5.2is ud.
5.3The test specimen for sheets shall be in the form of a bar 7
6.2mm [3in.]long by 25.4mm [1in.]wide by the thickness of the material.When comparison of absorption values with molded plastics is desired,specimens 3.2-mm [1⁄8-in.]thick should be ud.Per
missible variations in thickness shall be 0.20mm [60.008in.]except for materials which have greater standard commercial tolerances.
5.4The test specimen for rods shall be 25.4-mm [1-in.]long for rods 25.4mm in diameter or under and 12.7-mm [1⁄2-in.]long for larger-diameter rods.The diameter of the specimen shall be the diameter of the finished rod.
5.5The test specimen for tubes less than 76mm [3in.]in inside diameter shall be the full ction of the tube and 25.4-mm [1-in.]long.For tubes 76mm [3in.]or more in inside diameter,a rectangular specimen shall be cut 76mm in length in the circumferential direction of the tube and 25.4mm in width lengthwi of the tube.
5.6The test specimens for sheets,rods,and tubes shall be machined,sawed,or sheared from the sample so as to have smooth edges free from cracks.The cut edges shall be made smooth by finishing with No.0or finer sandpaper or emery cloth.Sawing,machining,and sandpapering operations shall be slow enough so that the material is not heated appreciably.
N OTE 3—If there is any oil on the surface of the specimen when received or as a result of machining operations,wash the specimen with a cloth wet with gasoline to remove oil,wipe with a dry
cloth,and allow to stand in air for 2h to permit evaporation of the gasoline.If gasoline attacks the plastic,u some suitable solvent or detergent that will evaporate within the 2-h period.
5.7The dimensions listed in the following table for the various specimens shall be measured to the nearest 0.025mm [0.001in.].Dimensions not listed shall be measured within 0.8mm [61⁄32in.].
点餐英文
Type of Specimen Dimensions to Be Measured to the Nearest 0.025mm [0.001in.]Molded disk thickness Sheet thickness
Rod length and diameter
Tube
inside and outside diameter,and wall thickness
6.Conditioning
6.1Three specimens shall be conditioned as follows:
6.1.1Specimens of materials who water-absorption value would be appreciably affected by temper
atures in the neigh-borhood of 110°C [230°F],shall be dried in an oven for 24h at 5063°C [12265.4°F],cooled in a desiccator,and imme-diately weighed to the nearest 0.001g.
N OTE 4—If a static charge interferes with the weighing,lightly rub the surface of the specimens with a grounded conductor.
6.1.2Specimens of materials,such as phenolic laminated plastics and other products who water-absorption value has been shown not to be appreciably affected by temperatures up to 110°C [230°F],shall be dried in an oven for 1h at 105to 110°C [221to 230°F].
6.1.3When data for comparison with absorption values for other plastics are desired,the specimens shall be dried in an oven for 24h at 5063°C [12265.4°F],cooled in a desic-cator,and immediately weighed to the nearest 0.001g.
7.Procedure
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7.1Twenty-Four Hour Immersion —The conditioned speci-mens shall be placed in a container of distilled water main-tained at a temperature of 2361°C [73.461.8°F],and shall rest on edge and be entirely immerd.At the end of 24,+1⁄2,−0h,the specimens shall be removed from the water one at a
time,all surface water wiped off with a dry cloth,and weighed to the nearest 0.001g immediately.If the specimen is 1⁄ less in thickness,it shall be put in a weighing bottle immedi-ately after wiping and weighed in the bottle.湖南有哪些地方
7.2Two-Hour Immersion —For all thickness of materials having a relatively high rate of absorption,and for thin specimens of other materials which may show a significant weight increa in 2h,the specimens shall be tested as described in 7.1except that the time of immersion shall be reduced to 12064min.
7.3Repeated Immersion —A specimen may be weighed to the nearest 0.001g after 2-h immersion,replaced in the water,and weighed again after 24h.
N OTE 5—In using this test method the amount of water absorbed in 24h may be less than it would have been had the immersion not been interrupted.
7.4Long-Term Immersion —To determine the total water absorbed when substantially saturated,the conditioned speci-mens shall be tested as described in 7.1except that at the end of 24h they shall be removed from the water,wiped free of surface moisture with a dry cloth,weighed to the nearest 0.001g immediately,and then replaced in the water.The weighings shall be repeated at the end of the
first week and every two weeks thereafter until the increa in weight per two-week period,as shown by three concutive weighings,averages less than 1%of the total increa in weight or 5mg,whichever is greater;the specimen shall then be considered substantially saturated.The difference between the substantially saturated weight and the dry weight shall be considered as the water absorbed when substantially saturated.
7.5
Two-Hour Boiling Water Immersion —The conditioned specimens shall be placed in a container of boiling distilled water,and shall be supported on edge and be entirely im-merd.At the end of 12064min,the specimens shall be removed from the water and cooled in distilled water main-tained at room temperature.After 1561min,the specimens shall be removed from the water,one at a time,all surface
TABLE 1Time to Saturation for Various Thickness of Nylon-6
Thickness,mm
Typical Time to 95%Saturation,h
110024003.21000101000025
62000
water removed with a dry cloth,and the specimens weighed to the nearest0.001g immediately.If the specimen is1⁄ less in thickness,it shall be weighed in a weighing bottle. 7.6One-Half-Hour Boiling Water Immersion—For all thickness of materials having a relatively high rate of absorption and for thin specimens of other materials which may show a significant weight increa in1⁄2h,the specimens shall be tested as described in7.5,except that the time of immersion shall be reduced to3061min.
7.7Immersion at50°C—The conditioned specimens shall be tested as described in7.5,except that the time and temperature of immersion shall be4861h and5061°C [122.061.8°F],respectively,and cooling in water before weighing shall be omitted.
7.8When data for comparison with absorption values for other plastics are desired,the24-h immersio
n procedure described in7.1and the equilibrium value determined in7.4 shall be ud.
8.Reconditioning
8.1When materials are known or suspected to contain any appreciable amount of water-soluble ingredients,the speci-mens,after immersion,shall be weighed,and then recondi-tioned for the same time and temperature as ud in the original drying period.They shall then be cooled in a desiccator and immediately reweighed.If the reconditioned weight is lower than the conditioned weight,the difference shall be considered as water-soluble matter lost during the immersion test.For such materials,the water-absorption value shall be taken as the sum of the increa in weight on immersion and of the weight of the water-soluble matter.
9.Calculation and Report
9.1The report shall include the values for each specimen and the average for the three specimens as follows:
9.1.1Dimensions of the specimens before test,measured in accordance with5.6,and reported to the nearest0.025mm [0.001in.],
9.1.2Conditioning time and temperature,
9.1.3Immersion procedure ud,
9.1.4Time of immersion(long-term immersion procedure only),
9.1.5Percentage increa in weight during immersion,cal-culated to the nearest0.01%as follows:
Increa in weight,%5wet weight2conditioned weight
conditioned weight
3100
9.1.6Percentage of soluble matter lost during immersion,if
determined,calculated to the nearest0.01%as follows(e
Note6):
Soluble matter lost,%5
conditioned weight2reconditioned weight
conditioned weight
3100
N OTE6—When the weight on reconditioning the specimen after im-
mersion in water exceeds the conditioned weight prior to immersion,
report“none”under9.1.6.
9.1.7For long-term immersion procedure only,prepare a
graph of the increa in weight as a function of the square root
of each immersion time.The initial slope of this graph is
proportional to the diffusion constant of water in the plastic.
The plateau region with little or no change in weight as a
function of the square root of immersion time reprents the
saturation water content of the plastic.
N OTE7—Deviation from the initial slope and plateau model indicates
that simple diffusion may be a poor model for determining water content.
In such cas,additional studies are suggested to determine a better model
for water absorption.
9.1.8The percentage of water absorbed,which is the sum of
the values in9.1.5and9.1.6,and
9.1.9Any obrvations as to warping,cracking,or change
in appearance of the specimens.
10.Precision and Bias5
10.1Precision—An interlaboratory test program was car-全音符怎么画
ried out using the procedure outlined in7.1,involving three
laboratories and three materials.Analysis of this data yields the
following coefficients of variation(average of three replicates).
Within
Laboratories
Between
Laboratories
Average absorption above
1%(2materials)
2.33% 4.89%
Average absorption below
0.2%(1material)
9.01%16.63%
N OTE8—A round robin is currently under way to more completely
determine repeatability and reproducibility of this test method.
10.2Bias—No justifiable statement on the bias of this test
method can be made,since the true value of the property
cannot be established by an accepted referee method.
11.Keywords简单风景速写
11.1absorption;immersion;plastics;water
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1064.
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