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常用工程塑料的密度表簡稱英文學名中文學名比重g/cm3工PA-6尼龍單6Polyamide-6聚先胺-6 1.13程PA6+15%GF 1.27塑PA-66尼龍件6polyamide-66聚先胺-66 1.13料PA66+30%GF Polyamide-66＋30%Glass Fiber聚先胺-66+30%玻纖1.39PA66+40%GF 聚先胺-66+40%玻纖1.46PA46+40%GF 聚先胺-46+40%玻纖1.27POM賽鋼Polyacetel聚甲醛1.42 PC Polycarbonate聚碳酸酯1.2PET poly(EthyleneTerephthalate)聚封苯二甲酸乙二醇酯1.33PET+30%GF PET+30%Glass Fiber同上+30%玻纖 1.67PETG CHDM ModifiedCopolyester改性聚酯 1.27PCTG CHDM ModifiedCopolyester改性聚酯 1.23PBT Poly(ButyleneTerephthalate)聚封苯二甲酸丁二醇酯1.4PBT+30%GF PBT+30%Glass Fiber同上+30%玻纖 1.61 PCT+30%GF Poly cyclohexylenedimeth yleneTerephthalate改性聚酯 1.45CA酸性膠Cellulose Acetate醋酸纖維素 1.26CAP Cellulose acetatePropionate丙酸纖維素 1.2CAB Cellulose AcetateButyrate丁酸纖維素 1.19耐高溫PPHigh HeatPolypropylene耐高溫聚丙烯 1.12防火PP Flame RetardedPolypropylene防火聚丙烯0.95PPS+40%GF Polyphenyiene Sulfide 聚苯硫酸+40%玻纖1.67PPO Polyphenyiene Oxide聚苯酸1.07 PSU Polysulfone聚1.24 PES polyether Sulfone聚酸 1.37 LCP Liquid Crystal Polymer 液晶聚合物 1.7SBS彈性膠Styrene-butadiene-styrene block copolymer苯乙烯嵌段共聚物0.96-1.10SEBS彈性膠styrene-cthylene-butadiene-styrene blockcopolymer氬化苯乙烯嵌段共聚物0.87-0.91TPU ThermoplasticPolyurethane熱塑性聚氨酯 1.24TPV ThermoplasticVulcanizate完全硫化聚烯輕彈性膠0.97COP Polyester Elastomer聚酯彈性膠 1.2通GPPS硬膠General PurposePolystyrene通用聚苯乙烯 1.16用HIPS不碎膠High ImpacctPolystyrene高行聚苯乙烯 1.08塑ABS Acrylonitrite ButadieneStyrene丙烯一丁二烯一苯乙烯1.05料AS（SAN）Acrylonitrile Styrene 丙烯一丁二烯一苯乙烯1.07BS（K膠）Butadiene Styrene 1.01LDPE軟膠Low DensityPolyethylene低密度聚乙烯0.92HDPE High DensityPolycthylene高密度聚乙烯0.96EVA Ethylene Vinyl Acclate乙烯-醋酸乙烯酯0.95PVC硬 1.38-1.41PP Polypropylene聚丙烯0.91PMMA 1.18簡稱英文學名中文學名比重g/cm3工PA46polyamide-46聚先胺-46 1.35程玻纤 1.96塑碳纤 1.57料橡胶管0.95碳钢7.8565Mn弹簧钢7.81Al6061铝合金 2.7SUS303不锈钢7.86常用金属Cu铜8.89H65铜合金8.45模塑收縮率%熱變形低壓℃料℃ * hrs料筒溫度℃模溫℃0.7-1.018080*4250-27040-601.320080*4280-30040-600.325070*4240-27080-902.1172100*2205-22580-1000.5137130*4271-29371-930.467154*6277-29315-300.2239135*4265-30595-1500.2-0.57070*5250-27015-400.2-0.57475*5275-29515-401.5-2.2152130*3225-24540-800.4-0.9221130*3225-25040-1000.1-0.4276120*4295-370105-1350.58170*4160-23040-600.583-8870*2215-24040-750.577-8770*2230-25040-850.9-1.113480*2180-22060-80111085*2180-22030-500.25260140*3300-340120-1500.5-0.8126110*3270-3100.5179130*4330-360120-1600.68208150*2340-380120-1600.02290140*5385-40035-2001.5N.A50*3145-16025-301.6N.A50*3180-20035-651.2N.A100*3190-22021-491.5-2.5N.A75*2180-190#### 1.490110*2220-25045 0.3-0.670-8070*2200-25040-600.570-8570*2210-27020-500.680-9580*3210-26050-800.685-9580*3220-27040-800.570-8070*2190-23030-50335-5065*1220-26020-40340-7565*1190-28030-702N.A65*1140-20020-401.5N.A60*1170-19020-40260-10060*1210-28020-500.695-10375*2220-24060-80模塑收縮率%熱變形低壓℃料℃ * hrs料筒溫度℃模溫℃。
实验 密度梯度管法测定聚合物的密度和结晶度密度梯度法是测定聚合物密度的方法之一。
聚合物的密度是聚合物的重要参数。
聚合物结晶过程中密度变化的测定，可研究结晶度和结晶速率；拉伸、退火可以改变取向度和结晶度，也可通过密度来进行研究；对许多结晶性聚合物其结晶度的大小对聚合物的性能、加工条件选择及应用都有很大影响。
聚合物的结晶度的测定方法虽有X 射线衍射法、红外吸收光谱法、核磁共振法、差热分析、反相色谱等等，但都要使用复杂的仪器设备。
而用密度梯度管法从测得的密度换算到结晶度，既简单易行又较为准确。
而且它能同时测定一定范围内多个不同密度的样品，尤其对很小的样品或是密度改变极小的一组样品，需要高灵敏的测定方法来观察其密度改变，此法既方便又灵敏。
一、实验目的：1．掌握用密度梯度法测定聚合物密度、结晶度的基本原理和方法。
2．利用文献上某些结晶性聚合物PE 和PP 晶区和非晶区的密度数据，计算结晶度。
二、基本原理：由于高分子结构的不均一性，大分子内摩擦的阻碍等原因，聚合物的结晶总是不完善的，而是晶相与非晶相共存的两相结构，结晶度f w 即表征聚合物样品中晶区部分重量占全部重量的百分数：在结晶聚合物中（如PP 、PE 等），晶相结构排列规则，堆砌紧密，因而密度大；而非晶结构排列无序，堆砌松散，密度小。
所以，晶区与非晶区以不同比例两相共存的聚合物，结晶度的差别反映了密度的差别。
测定聚合物样品的密度，便可求出聚合物的结晶度。
密度梯度法测定结晶度的原理就是在此基础上，利用聚合物比容的线性加和关 系，即聚合物的比容是晶区部分比容与无定形部分比容之和。
聚合物的比容V 和结晶度w f 有如下关系：()1c w a w V V f V f =+- --------------------------------- （2） 式中c V 为样品中结晶区比容，可以从X 光衍射分析所得的晶胞参数计算求得；a V 为样品中无定形区的比容，可以用膨胀计测定不同温度时该聚合物熔体的比容，然后外推得到该温度时非晶区的比容a V 的数值。
Designation:D 1505–03Standard Test Method forDensity of Plastics by the Density-Gradient Technique 1This standard is issued under the fixed designation D 1505;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.This standard has been approved for use by agencies of the Department of Defense.1.Scope*1.1This test method covers the determination of the density of solid plastics.1.2This test method is based on observing the level to which a test specimen sinks in a liquid column exhibiting a density gradient,in comparison with standards of known density.N OTE 1—The comparable ISO document is ISO 1183–2.There has not been any data generated to date comparing the results of the ISO method with this method.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.2.Referenced Documents 2.1ASTM Standards:2D 941Test Method for Density and Relative Density (Spe-cific Gravity)of Liquids by Lipkin Bicapillary Pycnometer D 2839Practice for Use of a Melt Index Strand for Deter-mining Density of PolyethyleneD 4703Practice for Compression Molding Thermoplastic Materials into Test Specimens,Plaques,or SheetsE 691Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method 2.2ISO Standard:ISO 1183-2Methods for Determining the Density and Rela-tive Density of Noncellular Plastics 33.Terminology 3.1Definition:3.1.1density of plastics —the weight per unit volume of material at 23°C,expressed as follows:D 23C ,g/cm 3(1)N OTE 2—Density is to be distinguished from specific gravity,which is the ratio of the weight of a given volume of the material to that of an equal volume of water at a stated temperature.4.Significance and Use4.1The density of a solid is a conveniently measurable property which is frequently useful as a means of following physical changes in a sample,as an indication of uniformity among samples,and a means of identification.4.2This test method is designed to yield results accurate to better than 0.05%.N OTE 3—Where accuracy of 0.05%or better is desired,the gradient tube shall be constructed so that vertical distances of 1mm shall represent density differences no greater than 0.0001g/cm.3The sensitivity of the column is then 0.0001g/cm 3·mm.Where less accuracy is needed,the gradient tube shall be constructed to any required sensitivity.5.Apparatus5.1Density-Gradient Tube —A suitable graduate with ground-glass stopper.45.2Constant-Temperature Bath —A means of controlling the temperature of the liquid in the tube at 2360.1°C.A thermostatted water jacket around the tube is a satisfactory and convenient method of achieving this.5.3Glass Floats —A number of calibrated glass floats cov-ering the density range to be studied and approximately evenly distributed throughout this range.5.4Pycnometer ,for use in determining the densities of the standard floats.5.5Liquids ,suitable for the preparation of a density gradi-ent (Table 1).N OTE 4—It is very important that none of the liquids used in the tube1This test method is under the jurisdiction of ASTM Committee D20on Plastic and is the direct responsibility of Subcommittee D20.70on Analytical Methods (Section D20.70.01).Current edition approved November 1,2003.Published January 2004.Originally approved in st previous edition approved in 1998as D 1505-98.2For referenced ASTM standards,visit the ASTM website,,or contact ASTM Customer Service at service@.For Annual Book of ASTM Standards volume information,refer to the standard’s Document Summary page on the ASTM website.3Available from American National Standards Institute (ANSI),25W.43rd St.,4th Floor,New York,NY 10036.4Tubes similar to those described in Refs (6)and (12)may also be used.1*A Summary of Changes section appears at the end of this standard.Copyright ©ASTM International,100Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959,United States.exert a solvent or chemical effect upon the test specimens during the time of specimen immersion.5.6Hydrometers —A set of suitable hydrometers covering the range of densities to be measured.These hydrometers should have 0.001density graduations.5.7Analytical Balance ,with a sensitivity of 0.001g.5.8Siphon or Pipet Arrangement ,for filling the gradient tube.This piece of equipment should be constructed so that the rate of flow of liquid may be regulated to 1065mL/min.6.Test Specimen6.1The test specimen shall consist of a piece of the material under test.The piece may be cut to any shape convenient for easy identification,but should have dimensions that permit the most accurate position measurement of the center of volume of the suspended specimen (Note 5).Care should be taken in cutting specimens to avoid change in density resulting from compressive stress.N OTE 5—The equilibrium positions of film specimens in the thickness range from 0.025to 0.051mm (0.001to 0.002in.)may be affected by interfacial tension.If this affect is suspected,films not less than 0.127mm (0.005in.)in thickness should be tested.6.2The specimen shall be free of foreign matter and voids and shall have no cavities or surface characteristics that will cause entrapment of bubbles.7.Preparation of Density-Gradient Columns7.1Preparation of Standard Glass Floats 5—Prepare glass floats by any convenient method such that they are fully annealed,approximately spherical,have a maximum diameter less than one fourth the inside diameter of the column,and do not interfere with the test specimens.Prepare a solution (400to 600mL)of the liquids to be used in the gradient tube such that the density of the solution is approximately equal to the desired lowest density.When the floats are at room temperature,drop them gently into the solution.Save the floats that sink very slowly,and discard those that sink very fast,or save them for another tube.If necessary to obtain a suitable range of floats,grind selected floats to the desired density by rubbing the head part of the float on a glass plate on which is spread a thin slurry of 400or 500-mesh silicon carbide (Carborundum)or otherappropriate abrasive.Progress may be followed by dropping the float in the test solution at intervals and noting its change in rate of sinking.7.2Calibration of Standard Glass Floats (see Appendix X1):7.2.1Place a tall cylinder in the constant-temperature bath maintained at 2360.1°C.Then fill the cylinder about two thirds full with a solution of two suitable liquids selected from Table 1,the density of which can be varied over the desired range by the addition of either liquid to the mixture.After the cylinder and solution have attained temperature equilibrium,place the float in the solution,and if it sinks,add the denser liquid by suitable means with good stirring until the float reverses direction of movement.If the float rises,add the less dense liquid by suitable means with good stirring until the float reverses direction of movement.7.2.2When reversal of movement has been observed,re-duce the amount of the liquid additions to that equivalent to 0.0001-g/cm 3density.When an addition equivalent to 0.0001-g/cm 3density causes a reversal of movement,or when the float remains completely stationary for at least 15min,the float and liquid are in satisfactory balance.The cylinder must be covered whenever it is being observed for balance,and the liquid surface must be below the surface of the liquid in the constant-temperature bath.After vigorous stirring,the liquid may continue to move for a considerable length of time;make sure that the observed movement of the float is not due to liquid motion by waiting at least 15min after stirring has stopped before observing the float.7.2.3When balance has been obtained,fill a freshly cleaned and dried pycnometer with the solution and place it in the 2360.1°C bath for sufficient time to allow temperature equilib-rium of the glass.Determine the density of the solution by normal methods (Test Method D 941)and make “in vacuo”corrections for all weighings.Record this as the density of the float.Repeat the procedure for each float.7.3Gradient Tube Preparation (see appendix for details):7.3.1Method A —Stepwise addition.7.3.2Method B —Continuous filling (liquid entering gradi-ent tube becomes progressively less dense).7.3.3Method C —Continuous filling (liquid entering gradi-ent tube becomes progressively more dense).8.Conditioning8.1Test specimens whose change in density on conditioning may be greater than the accuracy required of the density determination shall be conditioned before testing in accordance with the method listed in the applicable ASTM material specification.9.Procedure9.1Wet three representative test specimens with the less dense of the two liquids used in the tube and gently place them in the tube.Allow the tube and specimens to reach equilibrium,which will require 10min or more.Thin films of 1to 2mils in thickness require approximately 11⁄2h to settle,and rechecking after several hours is advisable (Note 4).9.2Read the height of each float and each specimen by a line through the individual center of volume and averaging the5Glass floats may be purchased from American Density Materials,3826Springhill Rd.Staunton,V A 24401,Ph:(540)887-1217.TABLE 1Liquid Systems for Density-Gradient TubesSystemDensity Range,g/cm 3Methanol-benzyl alcohol 0.80to 0.92Isopropanol-water0.79to 1.00Isopropanol-diethylene glycol 0.79to 1.11Ethanol-carbon tetrachloride 0.79to 1.59Toluene-carbon tetrachloride 0.87to 1.59Water-sodium bromide 1.00to 1.41Water-calcium nitrate1.00to 1.60Carbon tetrachloride-trimethylene dibromide 1.60to 1.99Trimethylene dibromide-ethylene bromide 1.99to2.18Ethylene bromide-bromoform2.18to2.89three values.When a cathetometer is used,measure the height of the floats and specimens from an arbitrary level using a line through their center of volume.If equilibrium is not obtained,the specimen may be imbibing the liquid.9.3Old samples can be removed without destroying the gradient by slowly withdrawing a wire screen basket attached to a long wire (Note 6).This can be conveniently done by means of a clock motor.Withdraw the basket from the bottom of the tube and,after cleaning,return it to the bottom of the tube.It is essential that this procedure be performed at a slow enough rate (approximately 30min/300-mm length of column)so that the density gradient is not disturbed.N OTE 6—Whenever it is observed that air bubbles are collecting on samples in the column,a vacuum applied to the column will correct this.10.Calculation10.1The densities of the samples may be determined graphically or by calculation from the levels to which the samples settle by either of the following methods:10.1.1Graphical Calculation —Plot float position versus float density on a chart large enough to be read accurately to 61mm and the desired precision of density.Plot the positions of the unknown specimens on the chart and read their corre-sponding densities.10.1.2Numerical Calculation —Calculate the density by interpolation as follows:Density at x 5a 1[~x 2y !~b 2a !/~z 2y !#(2)where:a andb =densities of the two standard floats,y and z =distances of the two standards,a and b ,respec-tively,bracketing the unknown measured from an arbitrary level,andx =distance of unknown above the same arbitrarylevel.11.Report11.1Report the following information:11.1.1Density reported as D 23C ,in grams per cubic centimetre,as the average for three representative test speci-mens,11.1.2Number of specimens tested if different than three,11.1.3Sensitivity of density gradient in grams per cubic centimetre per millimetre,11.1.4Complete identification of the material tested,and 11.1.5Date of the test.12.Precision and Bias 612.1Specimens Molded in One Laboratory and Tested in Several Laboratories —An interlaboratory test was run in 1981in which randomized density plaques were supplied to 22laboratories.Four polyethylene samples of nominal densities of 0.92to 0.96g/cm 3were molded in one laboratory.The data were analyzed using Practice E 691,and the results are given in Table 2.12.2Specimens Molded and Tested in Several Laboratories :12.2.1Samples Prepared Using Practice D 4703in Each Laboratory —Table 3is based on a round robin 9conducted in 1994in accordance with Practice E 691,involving seven materials tested by 7to 11laboratories.For each material,all of the samples were prepared by each laboratory,molded in accordance with Procedure C of Annex A1of Practice D 4703,and tested using this test method.The data are for comparison with the data of the same samples tested by Practice D 2839.Each test result is an individual determination.Each laboratory obtained six test results for each material.12.2.2Samples Prepared Using Practice D 2839in Each Laboratory —Table 4is based on a round robin 9conducted in 1994in accordance with Practice E 691,involving seven materials tested by 10to 15laboratories.For each material,all of the samples were prepared by each laboratory in accordance with Practice D 2839.Each test result is an individual deter-mination.Each laboratory obtained six test results for each material.12.3Concept of r and R —Warning—The following expla-nations of r and R (12.3-12.3.3)are only intended to present a meaningful way of considering the approximate precision of this test method.The data in Table 1should not be rigorously applied to acceptance or rejection of material,as those data are specific to the round robin and may not be representative of other lots,conditions,materials,or ers of this test method should apply the principles outlined in Practice E 691to generate data specific to their laboratory and materi-als,or between specific laboratories.The principles of 12.3-12.3.3would then be valid for each data.If S r and S R have been calculated from a large enough body of data,and for test results that were averages from testing one specimen:12.3.1Repeatability Limit,r (Comparing two test results for the same material,obtained by the same operator using the6Supporting data are available from ASTM Headquarters.Request RR:D20-1123.TABLE 2Precision Data Summary—Polyethylene DensityMaterial Average Density,g/cm 3S r A S R B r C R D 10.91960.000290.001060.000820.004520.93190.000120.000800.000340.002330.95270.000330.001160.000930.003340.96230.000620.001140.001800.0033AS r =within-laboratory standard deviation for the indicated material.It is obtained by pooling the within-laboratory standard deviations of the test results from all of the participating laboratories.BS R =between-laboratories reproducibility,expressed as standard deviation,for the indicated material.Cr =within-laboratory repeatability limit =2.8S r .DR =between-laboratories reproducibility limit =2.8S R.same equipment on the same day)—The two test results should be judged not equivalent if they differ by more than the r value for that material.12.3.2Reproducibility Limit,R (Comparing two test results for the same material,obtained by different operators using different equipment in different laboratories)—The two test results should be judged not equivalent if they differ by more than the R value for that material.12.3.3Any judgment in accordance with 12.2.1or 12.2.2would have an approximate 95%(0.95)probability of being correct.12.3.4Bias —There are no recognized standards by which to estimate the bias of this test method.13.Keywords13.1density;film;gradient;plaque;polyolefins;polyeth-ylene;polypropylene;preparationAPPENDIXES(Nonmandatory Information)X1.FLOAT CALIBRATION—ALTERNATIVE TEST METHODX1.1This test method of float calibration has been found by one laboratory to save time and give the same accuracy as the standard test method.Its reliability has not been demon-strated by round-robin data.X1.1.1Prepare a homogeneous solution whose density is fairly close to that of the float in question.X1.1.2Fill a graduate about 3⁄4full with the solution,drop in the float,stopper,and place in a thermostatted water bath near 23°C.Fill a tared two-arm pycnometer (Test Method D 941,or equivalent)with the solution.Place the pycnometer in the bath.X1.1.3Vary the bath temperature until the solution density is very near to that of the float.(If the float was initially on the bottom of the graduate,lower the bath temperature until the float rises;if the float floated initially,raise the bath tempera-ture until the float sinks to the bottom.)X1.1.4Change the bath temperature in the appropriate direction in increments corresponding to solution density increments of about 0.0001g/cm 3until the float reverses direction of movement as a result of the last change.This must be done slowly (at least 15-min intervals between incremental changes on the temperature controller).Read the volume of liquid in the pycnometer.X1.1.5Change the bath temperature in increments in the opposite direction,as above,until a change in the float position again occurs.Read the volume of liquid in the pycnometer.N OTE X1.1—The float should rise off the bottom of its own volition.As a precaution against surface tension effects when the float is floating,the float should be pushed about halfway down in the liquid column and then observed as to whether it rises or falls.For this purpose,a length of Nichrome wire,with a small loop on the lower end and an inch or so of length extending above the liquid surface,is kept within the graduate throughout the course of the run.To push a floating float down,the cylinder is unstoppered and the upper wire end grasped with tweezers for the manipulations.The cylinder is then quickly restoppered.X1.1.6Remove the pycnometer from the bath,dry the outside,and set aside until the temperature reaches ambient temperature.Weigh and calculate the “in vacuo”mass of solution to ing the average of the two observed solution volumes,calculate the density of the solution to 0.0001g/cm 3.This solution density is also the float density.X1.1.7The pycnometer used should be calibrated for vol-ume from the 23°C calibration,although the reading is taken at a different temperature.The alternative test method is based on a number of unsupported assumptions but generally gives the same results as that described in 7.2within the accuracyTABLE 3Precision Data—Density,g/cm 3Material Number ofLaboratoriesDensity,g/cm 3S r A S R B r C R DB 70.91390.000290.000880.000810.00245F 80.91770.000180.000790.000510.00221G 80.92200.000280.000710.000780.00197A 110.93560.000360.001050.001000.00294E 110.95280.000460.001180.001290.00331C 100.96190.001000.001000.001030.00281D90.96330.000360.001370.001010.00384AS r =within-laboratory standard deviation for the indicated material.It is obtained by pooling the within-laboratory standard deviations of the test results from all of the participating laboratories.BS R =between-laboratories reproducibility,expressed as standard deviation,for the indicated material.Cr =within-laboratory repeatability limit =2.8S r .DR =between-laboratories reproducibility limit =2.8S R .TABLE 4Density,g/cm 3,Samples Prepared in Accordance WithPractice D 2839MaterialNumber ofLaboratoriesDensity,g/cm 3S r A S R B r C R D B 100.91390.000260.000780.000720.00219F 120.91790.000200.000780.000550.00220G 130.92220.000300.000730.000850.00206A 150.93570.000410.000800.001150.00225E 140.95300.000390.000920.001090.00258C 110.96150.000300.000730.000850.00206D100.96260.000530.001090.001480.00305AS r =within-laboratory standard deviation for the indicated material.It is obtained by pooling the within-laboratory standard deviations of the test results from all of the participating laboratories.BS R =between-laboratories reproducibility,expressed as standard deviation,for the indicated material.Cr =within-laboratory repeatability limit =2.8S r .DR =between-laboratories reproducibility limit =2.8S R.required.In case of disagreement,the method described in7.2shall be the referee method.X2.GRADIENT TUBE PREPARATIONX2.1Method A—Stepwise Addition:X2.1.1Using the two liquids that will give the desireddensity range,and sensitivity(S)in grams per cubic centimetreper millimetre,prepare four or more solutions such that eachdiffers from the next heavier by80S g/cm3.The number ofsolutions will depend upon the desired density range of thecolumn and shall be determined as follows:Numbers of solutions to prepare density2gradient(X2.1)column~Note X2.1!5~11D22D1!/80S(X2.1)where:D2=upper limit of density range desired,D1=lower limit of density range desired,andS=sensitivity,in grams per cubic centimetre per milli-metre.N OTE X2.1—Correct the value of(1+D2−D1)/80S to the nearestwhole number.To prepare these solutions,proceed as follows:Using the hydrometers,mix the two liquids in the proportions necessary to obtain the desired solutions.Remove the dissolved air from the solutions by gentle heating or an applied vacuum.Then check the density of the solutions at2360.1°C by means of the hydrometers and,if necessary,add the appropriate air-free liquid until the desired density is obtained.N OTE X2.2—Where aqueous mixtures are used,0.5%aqueous sodium acetate should be used to prepare the mixture.This reduces the formation of bubbles from dissolution.N OTE X2.3—In order to obtain a linear gradient in the tube,it is very important that the solutions be homogeneous and at the same temperature when their densities are determined.It is also important that the density difference between the solutions consecutively introduced into the tube be equal.X2.1.2By means of a siphon or pipet,fill the gradient tube with an equal volume of each liquid starting with the heaviest, taking appropriate measures to prevent air from being dis-solved in the liquid.After the addition of the heaviest liquid, very carefully and slowly pour an equal volume of the second heaviest liquid down the side of the column by holding the siphon or pipet against the side of the tube at a slight angle. Avoid excess agitation and turbulence.In this manner,the “building”of the tube shall be completed.N OTE X2.4—Density gradients may also be prepared by reversing the procedure described in X2.1.1and X2.1.2.When this procedure is used, the lightest solution is placed in the tube and the next lightest solution is very carefully and slowly“placed”in the bottom of the tube by means of a pipet or siphon which just touches the bottom of the tube.In this manner the“building”of the tube shall be completed.X2.1.3If the tube is not already in a constant-temperature bath,transfer the tube,with as little agitation as possible,to the constant-temperature bath maintained at2360.1°C.The bath level should approximately equal that of the solution in the tube,and provision should be made for vibrationless mounting of the tube.X2.1.4For every254mm of length of tube,dip a minimum offive clean calibratedfloats,spanning the effective range of the column,into the less dense solvent used in the preparation of the gradient tube and add them to the tube.By means of a stirrer(for example,a small coiled wire or other appropriate stirring device)mix the different layers of the tube gently by stirring horizontally until the least dense and most densefloats span the required range of the gradient tube.If,at this time,it is observed that thefloats are“bunched”together and not spread out evenly in the tube,discard the solution and repeat the procedure.Then cap the tube and keep it in the constant-temperature bath for a minimum of24h.X2.1.5At the end of this time,plot the density offloats versus the height offloats to observe whether or not a fairly smooth and nearly linear curve is obtained.Some small irregularities may be seen,but they should be slight.Whenever an irregular curve is obtained,the solution in the tube shall be discarded and a new gradient prepared.N OTE X2.5—Gradient systems may remain stable for several months. X2.2Method B—Continuous Filling with Liquid Entering Gradient Tube Becoming Progressively Less Dense:X2.2.1Assemble the apparatus as shown in Fig.X2.1,using beakers of the same diameter.Then select an appropriate amount of two suitable liquids which previously have been carefully deaerated by gentle heating or an applied vacuum. Typical liquid systems for density-gradient tubes are listed in Table1.The volume of the more dense liquid used in the mixer (Beaker B shown in Fig.X2.1)must be equal to at least one half of the total volume desired in the gradient tube.An FIG.X2.1Apparatus for Gradient TubePreparationestimate of the volume of the less dense liquid required in Beaker A to establishflow from A to B can be obtained from the following inequality:V A.d B V B/d A(X2.2) where:V A=starting liquid volume in Beaker A,V B=starting liquid volume in Beaker B,d A=density of the starting liquid in Beaker A,andd B=density of the starting liquid in Beaker B.A small excess(not exceeding5%)over the amount indicated by the preceding equality will induce the required flow from A toB and yield a very nearly linear gradient column.X2.2.2Place an appropriate volume of the denser liquid into Beaker B of suitable size.Prime the siphon between Beaker B and the gradient tube with liquid from Beaker B and then close the stopcock.The delivery end of this siphon should be equipped with a capillary tip forflow control.N OTE X2.6—Techniques acceptable for transfer of liquid into the gradient tube are siphon/gravity,vacuum-filling,use of a peristatic pump, or any other technique useful to transfer liquids in a controlled manner.It is important to control theflow in order to maintain a desirable gradient. X2.2.3Place an appropriate volume of the less dense liquid into Beaker A.Prime the siphon between Beakers A and B with the liquid from Beaker A and close the stopcock.Start the highspeed,propeller-type stirrer in Beaker B and adjust the speed of stirring such that the surface of the liquid does not fluctuate greatly.X2.2.4Start the delivery of the liquid to the gradient tube by opening the necessary siphon-tube stopcocks simultaneously. Adjust theflow of liquid into the gradient tube at a very slow rate,permitting the liquid toflow down the side of the tube.Fill the tube to the desired level.N OTE X2.7—Preparation of a suitable gradient tube may require1to 11⁄2h or longer,depending upon the volume required in the gradient tube. X2.3Method C—Continuous Filling with Liquid Entering Gradient Tube Becoming Progressively More Dense:X2.3.1This method is essentially the same as Method B with the following exceptions:X2.3.2The lighter of the two liquids is placed in Beaker B. X2.3.3The liquid introduced into the gradient column is introduced at the bottom of the column.Thefirst liquid introduced is the lighter end of the gradient and is constantly pushed up in the tube as the liquid being introduced becomes progressively heavier.X2.3.4The liquid from Beaker A must be introduced into Beaker B by directflow from the bottom of Beaker A to the bottom of Beaker B,rather than being siphoned over as it is in Method B.Filling the tube by this method may be done more rapidly than by Methods A or B.The stopcock between Containers A and B should be of equal or larger bore than the outlet stopcock.A schematic drawing of the apparatus for Method C is shown in Fig.X2.2.REFERENCES (1)Linderstrøm-Lang,K.,“Dilatometric Ultra-Micro-Estimation of Pep-tidase Activity,”Nature,NATRA,V ol139,1937,p.713.(2)Linderstrøm-Lang,K.,and Lanz,H.,“Enzymic Histochemistry XXIXDilatometric Micro-Determination of Peptidase Activity,”Comptesrendus des gravaus de laboratorie Carlsberg,Serie Chimique,V ol21,1938,p.315.(3)Linderstrøm-Lang,K.,Jacobsen,O.,and Johansen,G.,“Measurementof the Deuterium Content in Mixtures of H2O and D2O,”ibid.,V ol23,1938,p.17.(4)Jacobsen,C.F.,and Linderstrøm-Lang,K.,“Method for Rapid Deter-mination of Specific Gravity,”Acta Physiologica Scandinavica,AP-SCA,V ol1,1940,p.149.(5)Boyer,R.F.,Spencer,R.S.,and Wiley,R.M.,“Use of Density-Gradient Tube in the Study of High Polymers,”Journal of Polymer Science,JPSCA,V ol1,1946,p.249.(6)Anfinsen,C.,“Preparation and Measurement of Isotopic Tracers:ASymposium Prepared for the Isotope Research Group,”Edwards,J.W.,Publishers,Ann Arbor,MI,1946,p.61.(7)Tessler,S.,Woodberry,N.T.,and Mark,H.,“Application of theDensity-Gradient Tube in Fiber Research,”Journal of Polymer Sci-ence,JPSCA,V ol1,1946,p.437.(8)Low,B.W.,and Richards,F.M.,“The Use of the Gradient Tube forthe Determination of Crystal Densities,”Journal of the American Chemical Society,JACSA,V ol74,1952,p.1660.(9)Sperati,C.A.,Franta,W.A.,and Starkweather,H.W.,Jr.,“TheMolecular Structure of Polyethylene V,the Effect of Chain Branching and Molecular Weight on Physical Properties,”Journal of the Ameri-can Chemical Society,JACSA,V ol75,1953,p.6127.(10)Tung,L.H.,and Taylor,W.C.,“An Improved Method of PreparingDensity Gradient Tubes,”Journal of Polymer Science,JPSCA,V ol 21,1956,p.144.(11)Mills,J.M.,“A Rapid Method of Construction Linear DensityGradient Columns,”Journal of Polymer Science,V ol19,1956,p.585.(12)Wiley,R.E.,“Setting Up a Density Gradient Laboratory,”PlasticsTechnology,PLTEA,V ol8,No.3,1962,p.31.FIG.X2.2Apparatus for Gradient TubePreparation。
常见塑料物性的检测及标准流动系数（1）测试的标准：ASTMD1238（2）常用的测试标准的量测仪器是溶液指数计（MeltIndeGer）.（3）流动系数检测方法：是一种表示塑胶材料加工时的流动性的数值。
它是美国量测标准协会(ASTM)根据美国杜邦公司(DuPont)惯用的鉴定塑料特性的方法制定而成，其测试方法是先让塑料粒在一定时间（10分钟）内、一定温度及压力（各种材料标准不同）下，融化成塑料流体，然后通过一直径为2.1mm圆管所流出的克（g）数。
其值越大，表示该塑胶材料的加工流动性越佳，反之则越差。
（4）测试的具体操作过程是：将待测高分子（塑料）原料置入小槽中，槽末接有细管，细管直径为2.095mm，管长为8mm。
加热至某温度后，原料上端藉由活塞施加某一定重量向下压挤，量测该原料在10分钟内所被挤出的重量，即为该塑料的流动指数。
有时您会看到这样的表示法?MI25g/10min，它表示在10分钟内该塑料被挤出25克。
一般常用塑料的MI值大约介于1~25之间。
MI愈大，代表该塑料原料粘度愈小及分子重量愈小，反之则代表该塑料粘度愈大及分子重量愈大。
收缩率测试的标准：ASTMD955塑胶制品经冷却、固化并脱模成形后，其尺寸与原模具尺寸之差的百分比。
（3）因结构不同的关系，结晶性塑料与非结晶性塑料的收缩率存在明显的差异。
一般地，结晶性塑料的收缩率比非结晶性塑料的收缩率大上好几倍（如下表所示）。
同时有添加玻璃纤维或其它强化剂的塑胶材料，其收缩率可降低好几倍。
影响成型收缩的因素有热收缩、结晶度（热塑性）或硬化度（热固性）、弹性回复、分子配向、与成型条件等因素。
<1>热塑性塑料热膨胀系数测试的标准：ASTMD696塑料加热时尺寸膨胀的比率由于一般塑料的热膨胀系数比金属大2～10倍，因此在设计模具、塑料与金属并用的器具、塑料的钳核物时，必须详加考虑，以防止因内部应力而造成产品的龟裂变形。
玻璃转移点（TG）当塑料的温度达到玻璃转移点时，其分子键的分枝开始局部脉动，塑料便由玻璃状变成橡胶状。
塑料密度快速测定法与3h（小时）密度梯度法的对比实验摘要：密度是塑料的一个特征物理量，不同的塑料具有不同的密度范围。
对于HDPE，LLDPE等，ASTM，ISO，GB均有相应测定标准，这些标准检测周期比较长，测试相对比较麻烦。
作者进行密度快速测定法、与3h密度梯度法在HDPE和LLDPE的对比实验的研究。
根据实验结果分析得出：快速密度测定法与3h密度梯度法存在规定差值，即：0.0020-0.0030之间，在精确度要求不高的情况下，快速密度测定法可以代替3h密度梯度法以更快的速度、更少的二次污染来测定塑料密度。
关键词：塑料密度快速测定法一、仪器与试剂密度梯度计：英国RAY-RAN公司型号RR/DGA1恒温水浴：温度波动不大于士0.1℃。
密度计：密度范围适合配管密度的要求，精确到士0.001 g/cm3。
密度梯度管：刻有精确分度的玻璃管，直径不小于40mm，长不小于250mm。
标准玻璃浮标：经过精确校正，密度范围适合配管要求熔融指数仪：挤出样条异丙醇二、试样制备3h密度梯度法：用熔融指数样条作为密度样条，对于LLDPE待样条凝固后经400ml蒸馏水煮沸30min，对于HDPE经200ml沸水煮沸30min，待样条自然冷却至室温，用单面刀片截取样条中间3～5mm作为密度样条。
快速法：用熔融指数样条作为密度样条，直接冷却至室温后，用单面刀片截取样条中间3～5mm作为密度样条。
三、密度梯度柱配制用两个尺寸相同的玻璃容器，按GB/T 1033-2010中规定【1】，配制成相应的重液和轻液【2】，脱除气饱，起动电磁搅拌器，均匀搅拌，使混合液缓缓沿着梯度管壁流入管中，直至所需液位。
根据所需密度范围，选用5个以上的标准玻璃浮子，沿壁轻轻放入梯度柱中，使这一组标准玻璃浮子均匀分布于梯度柱的有效范围内。
将自己制好的密度梯度柱放在温度23±0.1℃下静置不少于2h待浮子位置稳定后，测量每个浮子的几何中心高度，精确到1mm。
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由于塑料消费渠道多而复杂，有品上标明材料品种。
中国参照美国塑料协装制品回收标志”， 虽可利用上述标记来困难，为将不同品种的塑料分别，以便：
热固性塑料或弹性体。
一般热塑性，只有在薄膜状态呈透明状，硬度从柔软质橡胶状（此时常加有增塑剂等添加剂）橡胶状手感，有一定的拉伸率。
塑性塑料加热时软化，易熔融，且热至材料化学分解前，保持其原有硬度不度前，不发生流动，至分解温度材料分解
些热塑性塑料会发生溶解，如聚乙微溶胀，弹性体不溶于溶剂，但通常会发
此时应将发泡制品分别出来，因为料的密度不同来分选塑料的。
常用塑料的
H试纸测试逸出气体的pH值来鉴别烧性， 同时注意熄火后，熔融塑
样，冷却后加入3滴50%的硫酸
n后再观察试样颜色，再在水浴中将试样应称为Liebermann-Storch-Morawski反应，聚偏二氯乙烯，聚氯乙烯混配料等，它乙醚萃取，以除去增塑剂，试验方法：将，萃取后在前75度以下干燥。
将干燥过的钠的甲醇溶液（1g氢氧化钠溶解于是20ml 即可鉴别不同的含氯塑料。
管中加热0。
1 ~0。
2g 试样，将的甲醇溶液，再滴一滴浓盐酸，如为尼龙。
测量不规则固体或液体的密度实验一：测量塑料块的密度 实验器材：托盘天平、砝码、量筒（或量杯）、细线、一杯水、塑料块。
实验步骤：1、用天平测出塑料块的质量m 。
2、在量筒（或量杯）中倒入适量的水，并读出水的体积V 0。
3、用细线拴住塑料块吊入量筒（或量杯）中，使其完全浸入水中，读出水和塑料块的总体积V 1。
4、通过计算得出塑料块的体积为V 。
5、通过密度公式Vm =ρ计算出塑料块的密度01ρV V m -=。
实验分析：该实验用到了排水法测量固体体积的方法，但注意的是所测物体必须是不溶于水的物质，且不易吸附水分。
实验二：测量木块的密度 实验器材：托盘天平、砝码、量筒（或量杯）、细线、一杯水、木块、铁块。
实验步骤：1、用天平测出木块的质量m 。
2、在量筒（或量杯）中倒入适量的水，把用细线拴住铁块并把其完全浸入量筒（或量杯）的水中，读出水和铁块的总体积V 0。
3、用细线同时拴住木块和铁块吊入量筒（或量杯）中，使其完全浸入水中，读出水和木块、铁块和水的总体积V 1。
4、通过计算得出木块的体积为V 。
5、通过密度公式Vm =ρ计算出木块的密度01ρV V m -=。
实验分析：木块的密度比水小，它会漂浮在水面上，为此此实验用了密度比较大的铁块把木块拉入水中，这样可以使木块完全浸入水中。
另外，在测量木块的体积时，不要忽略了铁块的体积。
实验三：测量铁块的密度 实验器材：托盘天平、砝码、带瓶盖的药瓶、足量的水、铁块、细线。
实验步骤：1、用天平测出铁块的质量为m 。
2、往药瓶里灌满水，盖好瓶盖，用天平测出药瓶和水的总质量m 0。
3、用细线把铁块完全浸入药瓶中，将溢出部分水。
然后再把铁块从药瓶中取出，盖好瓶盖，用天平再测量出药瓶和水的总质量m 1，则溢出的水的质量为m 0－m 1。
4、根据密度公式Vm =ρ的推导公式ρm=V 计算出溢出的水的体积为V=水ρ10m m -，即为铁块的体积。
5、铁块的密度ρ铁=水ρ10m m m -=水ρ10m m m -实验分析：此实验是在没有量筒（或量杯）的情况下，常用的一种测量固体密度的方法。
ASTM国际机构版权所有，地址：美国宾夕法尼亚洲，西康雪肯市巴尔港路100号。
由上海市标准化研究院（SIS）根据ASTM协议进行销售。
地址：上海市长乐路1219/1227号邮编：200031联系电话：86-21-64370807文件号：ASTM-D792-2008塑料密度与比重（相对比重）经更改的标准测试方法该标准在修订D792文献基础之上颁发,其采纳的起始年代和修改也包括了最后修订的年份。
其中的插入数字也表明最后通过的年份。
上角文号也表明从最初到有效的编辑更改时间。
该标准曾获国防部代理处通过。
1.范围*1.1这些测试方法描述了比重（相对比重）和固体塑料材料的密度形式，如板材、棒材、管材或压膜的测定方法。
1.2下面描述两种测试方法：1.2.1测试方法A—在水中测试固体塑料；1.2.2测试方法B—在除水以外的液态中测试固体塑料。
1.3在S1中描述的比值单位被看作标准值。
1.4该标准并不确保所有的安全内容，但可灵活使用。
使用者确立安全和健康标准还需依据其应用规则和使用的限制。
注1：该标准不能等同于ISO1183-1方法A。
该测试方法仅提供样品重量和规格指引。
ISO1183-1的容许测试温度范围：27℃±2°C。
2.参考文献2.1ASTM标准：D618塑料测试条件实作；D891比重、外观和液体工业化学品的测试方法；D4968专用塑料的年度评审测试方法指引；D6436塑料与热塑料弹性特征报告指引；E1ASTM玻璃装液体温度规格；E12与固体、液体和气体相关的密度和比重的相关术语；E691确定测试方法的准确操作；IEEE/ASTM SI-10国际单位体系的使用实作（现代公制）；3.术语3.1概要-在测试方法中使用的单位、符号、缩写遵循IEEE/ASTM SI-10要求。
3.2说明：3.2.1比重（相对比重）--额定量，温度在23°C条件下不渗透的物质比率，相当于释放气体或软化水在同等温度条件下，其形式表述为：比重-相对密度为23/23°C （或sp gr23/23°C）注2：这种说明基于E12中的表观比重和表观密度。
实验1 密度梯度管法测定高聚物的密度和结晶度高聚物的密度是高聚物的重要物理参数之一，它对于指导高聚物的合成、成型工艺以及探索结构与性能之间的关系等方面都是不可缺少的数据。
而对于结晶高聚物来说，结晶度反映了物质内部结构规则程度，影响着其许多物理、化学性能和应用性能，密度和结晶度之间有着密切的关系。
因此，测定高聚物的密度和结晶度，对研究其结构状态进而控制材料的性能有着很大的实用意义。
测定高聚物结晶度的方法很多，有X-射线衍射法、红外吸收光谱法、核磁共振法、差热分析法、反相色谱法、化学方法（水解法、甲酰化法、氘交换法）、密度法等等。
其中前几种方法都需要使用复杂的仪器设备，而密度法是从较容易测定的高聚物密度换算成结晶度，既简单易行，又较为准确。
凡是能测定出高聚物试样密度的方法都属于密度法。
本实验采用密度法中的一种方法 ── 密度梯度管法测定高聚物的结晶度。
一、实验目的1. 了解用密度梯度管法测定高聚物的密度和结晶度的基本原理和方法。
2. 学会用连续灌注法制备密度梯度管的技术及密度梯度管的标定方法。
3. 用密度梯度管测定结晶高聚物试样的密度，并计算其结晶度。
二、实验原理将两种密度不同且又能互溶的液体配制成一系列等差密度的混合液，并按照低密度液体（轻液）位于高密度液体（重液）之上的层次，把不同密度的混合液置于带有刻度的玻璃管中，由于液体分子的扩散作用，管中的液体密度将会从下到上呈连续的线性分布，这就是密度梯度管。
当把一个颗粒状试样放入密度梯度管中时，根据悬浮原理，试样会在与其密度相等的液位上悬浮不动。
配制密度梯度管所选用的轻液和重液种类不同时，密度梯度管的密度梯度范围就会不同。
在本实验后面的附表1-1中列出了一些常用的密度梯度管溶液体系。
高度图 1-1 密度梯度管的标定曲线将若干个已知其准确密度的标准玻璃小球放入密度梯度管中，读出各个小球在密度梯度管中的高度值，再以玻璃小球的密度值对小球的高度值作图，就可得到该密度梯度管的标定曲线。
Designation:D 1505–03Standard Test Method forDensity of Plastics by the Density-Gradient Technique 1This standard is issued under the fixed designation D 1505;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.This standard has been approved for use by agencies of the Department of Defense.1.Scope*1.1This test method covers the determination of the density of solid plastics.1.2This test method is based on observing the level to which a test specimen sinks in a liquid column exhibiting a density gradient,in comparison with standards of known density.N OTE 1—The comparable ISO document is ISO 1183–2.There has not been any data generated to date comparing the results of the ISO method with this method.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.2.Referenced Documents 2.1ASTM Standards:2D 941Test Method for Density and Relative Density (Spe-cific Gravity)of Liquids by Lipkin Bicapillary Pycnometer D 2839Practice for Use of a Melt Index Strand for Deter-mining Density of PolyethyleneD 4703Practice for Compression Molding Thermoplastic Materials into Test Specimens,Plaques,or SheetsE 691Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method 2.2ISO Standard:ISO 1183-2Methods for Determining the Density and Rela-tive Density of Noncellular Plastics 33.Terminology 3.1Definition:3.1.1density of plastics —the weight per unit volume of material at 23°C,expressed as follows:D 23C ,g/cm 3(1)N OTE 2—Density is to be distinguished from specific gravity,which is the ratio of the weight of a given volume of the material to that of an equal volume of water at a stated temperature.4.Significance and Use4.1The density of a solid is a conveniently measurable property which is frequently useful as a means of following physical changes in a sample,as an indication of uniformity among samples,and a means of identification.4.2This test method is designed to yield results accurate to better than 0.05%.N OTE 3—Where accuracy of 0.05%or better is desired,the gradient tube shall be constructed so that vertical distances of 1mm shall represent density differences no greater than 0.0001g/cm.3The sensitivity of the column is then 0.0001g/cm 3·mm.Where less accuracy is needed,the gradient tube shall be constructed to any required sensitivity.5.Apparatus5.1Density-Gradient Tube —A suitable graduate with ground-glass stopper.45.2Constant-Temperature Bath —A means of controlling the temperature of the liquid in the tube at 2360.1°C.A thermostatted water jacket around the tube is a satisfactory and convenient method of achieving this.5.3Glass Floats —A number of calibrated glass floats cov-ering the density range to be studied and approximately evenly distributed throughout this range.5.4Pycnometer ,for use in determining the densities of the standard floats.5.5Liquids ,suitable for the preparation of a density gradi-ent (Table 1).N OTE 4—It is very important that none of the liquids used in the tube1This test method is under the jurisdiction of ASTM Committee D20on Plastic and is the direct responsibility of Subcommittee D20.70on Analytical Methods (Section D20.70.01).Current edition approved November 1,2003.Published January 2004.Originally approved in st previous edition approved in 1998as D 1505-98.2For referenced ASTM standards,visit the ASTM website,,or contact ASTM Customer Service at service@.For Annual Book of ASTM Standards volume information,refer to the standard’s Document Summary page on the ASTM website.3Available from American National Standards Institute (ANSI),25W.43rd St.,4th Floor,New York,NY 10036.4Tubes similar to those described in Refs (6)and (12)may also be used.1*A Summary of Changes section appears at the end of this standard.Copyright ©ASTM International,100Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959,United States.exert a solvent or chemical effect upon the test specimens during the time of specimen immersion.5.6Hydrometers —A set of suitable hydrometers covering the range of densities to be measured.These hydrometers should have 0.001density graduations.5.7Analytical Balance ,with a sensitivity of 0.001g.5.8Siphon or Pipet Arrangement ,for filling the gradient tube.This piece of equipment should be constructed so that the rate of flow of liquid may be regulated to 1065mL/min.6.Test Specimen6.1The test specimen shall consist of a piece of the material under test.The piece may be cut to any shape convenient for easy identification,but should have dimensions that permit the most accurate position measurement of the center of volume of the suspended specimen (Note 5).Care should be taken in cutting specimens to avoid change in density resulting from compressive stress.N OTE 5—The equilibrium positions of film specimens in the thickness range from 0.025to 0.051mm (0.001to 0.002in.)may be affected by interfacial tension.If this affect is suspected,films not less than 0.127mm (0.005in.)in thickness should be tested.6.2The specimen shall be free of foreign matter and voids and shall have no cavities or surface characteristics that will cause entrapment of bubbles.7.Preparation of Density-Gradient Columns7.1Preparation of Standard Glass Floats 5—Prepare glass floats by any convenient method such that they are fully annealed,approximately spherical,have a maximum diameter less than one fourth the inside diameter of the column,and do not interfere with the test specimens.Prepare a solution (400to 600mL)of the liquids to be used in the gradient tube such that the density of the solution is approximately equal to the desired lowest density.When the floats are at room temperature,drop them gently into the solution.Save the floats that sink very slowly,and discard those that sink very fast,or save them for another tube.If necessary to obtain a suitable range of floats,grind selected floats to the desired density by rubbing the head part of the float on a glass plate on which is spread a thin slurry of 400or 500-mesh silicon carbide (Carborundum)or otherappropriate abrasive.Progress may be followed by dropping the float in the test solution at intervals and noting its change in rate of sinking.7.2Calibration of Standard Glass Floats (see Appendix X1):7.2.1Place a tall cylinder in the constant-temperature bath maintained at 2360.1°C.Then fill the cylinder about two thirds full with a solution of two suitable liquids selected from Table 1,the density of which can be varied over the desired range by the addition of either liquid to the mixture.After the cylinder and solution have attained temperature equilibrium,place the float in the solution,and if it sinks,add the denser liquid by suitable means with good stirring until the float reverses direction of movement.If the float rises,add the less dense liquid by suitable means with good stirring until the float reverses direction of movement.7.2.2When reversal of movement has been observed,re-duce the amount of the liquid additions to that equivalent to 0.0001-g/cm 3density.When an addition equivalent to 0.0001-g/cm 3density causes a reversal of movement,or when the float remains completely stationary for at least 15min,the float and liquid are in satisfactory balance.The cylinder must be covered whenever it is being observed for balance,and the liquid surface must be below the surface of the liquid in the constant-temperature bath.After vigorous stirring,the liquid may continue to move for a considerable length of time;make sure that the observed movement of the float is not due to liquid motion by waiting at least 15min after stirring has stopped before observing the float.7.2.3When balance has been obtained,fill a freshly cleaned and dried pycnometer with the solution and place it in the 2360.1°C bath for sufficient time to allow temperature equilib-rium of the glass.Determine the density of the solution by normal methods (Test Method D 941)and make “in vacuo”corrections for all weighings.Record this as the density of the float.Repeat the procedure for each float.7.3Gradient Tube Preparation (see appendix for details):7.3.1Method A —Stepwise addition.7.3.2Method B —Continuous filling (liquid entering gradi-ent tube becomes progressively less dense).7.3.3Method C —Continuous filling (liquid entering gradi-ent tube becomes progressively more dense).8.Conditioning8.1Test specimens whose change in density on conditioning may be greater than the accuracy required of the density determination shall be conditioned before testing in accordance with the method listed in the applicable ASTM material specification.9.Procedure9.1Wet three representative test specimens with the less dense of the two liquids used in the tube and gently place them in the tube.Allow the tube and specimens to reach equilibrium,which will require 10min or more.Thin films of 1to 2mils in thickness require approximately 11⁄2h to settle,and rechecking after several hours is advisable (Note 4).9.2Read the height of each float and each specimen by a line through the individual center of volume and averaging the5Glass floats may be purchased from American Density Materials,3826Springhill Rd.Staunton,V A 24401,Ph:(540)887-1217.TABLE 1Liquid Systems for Density-Gradient TubesSystemDensity Range,g/cm 3Methanol-benzyl alcohol 0.80to 0.92Isopropanol-water0.79to 1.00Isopropanol-diethylene glycol 0.79to 1.11Ethanol-carbon tetrachloride 0.79to 1.59Toluene-carbon tetrachloride 0.87to 1.59Water-sodium bromide 1.00to 1.41Water-calcium nitrate1.00to 1.60Carbon tetrachloride-trimethylene dibromide 1.60to 1.99Trimethylene dibromide-ethylene bromide 1.99to2.18Ethylene bromide-bromoform2.18to2.89three values.When a cathetometer is used,measure the height of thefloats and specimens from an arbitrary level using a line through their center of volume.If equilibrium is not obtained, the specimen may be imbibing the liquid.9.3Old samples can be removed without destroying the gradient by slowly withdrawing a wire screen basket attached to a long wire(Note6).This can be conveniently done by means of a clock motor.Withdraw the basket from the bottom of the tube and,after cleaning,return it to the bottom of the tube.It is essential that this procedure be performed at a slow enough rate(approximately30min/300-mm length of column) so that the density gradient is not disturbed.N OTE6—Whenever it is observed that air bubbles are collecting on samples in the column,a vacuum applied to the column will correct this.10.Calculation10.1The densities of the samples may be determined graphically or by calculation from the levels to which the samples settle by either of the following methods:10.1.1Graphical Calculation—Plotfloat position versus float density on a chart large enough to be read accurately to 61mm and the desired precision of density.Plot the positions of the unknown specimens on the chart and read their corre-sponding densities.10.1.2Numerical Calculation—Calculate the density by interpolation as follows:Density at x5a1[~x2y!~b2a!/~z2y!#(2) where:a and b=densities of the two standardfloats,y and z=distances of the two standards,a and b,respec-tively,bracketing the unknown measured froman arbitrary level,andx=distance of unknown above the same arbitrary level.11.Report11.1Report the following information:11.1.1Density reported as D23C,in grams per cubic centimetre,as the average for three representative test speci-mens,11.1.2Number of specimens tested if different than three, 11.1.3Sensitivity of density gradient in grams per cubic centimetre per millimetre,11.1.4Complete identification of the material tested,and 11.1.5Date of the test.12.Precision and Bias612.1Specimens Molded in One Laboratory and Tested in Several Laboratories—An interlaboratory test was run in1981 in which randomized density plaques were supplied to22 laboratories.Four polyethylene samples of nominal densities of0.92to0.96g/cm3were molded in one laboratory.The data were analyzed using Practice E691,and the results are given in Table2.12.2Specimens Molded and Tested in Several Laboratories: 12.2.1Samples Prepared Using Practice D4703in Each Laboratory—Table3is based on a round robin9conducted in 1994in accordance with Practice E691,involving seven materials tested by7to11laboratories.For each material,all of the samples were prepared by each laboratory,molded in accordance with Procedure C of Annex A1of Practice D4703, and tested using this test method.The data are for comparison with the data of the same samples tested by Practice D2839. Each test result is an individual determination.Each laboratory obtained six test results for each material.12.2.2Samples Prepared Using Practice D2839in Each Laboratory—Table4is based on a round robin9conducted in 1994in accordance with Practice E691,involving seven materials tested by10to15laboratories.For each material,all of the samples were prepared by each laboratory in accordance with Practice D2839.Each test result is an individual deter-mination.Each laboratory obtained six test results for each material.12.3Concept of r and R—Warning—The following expla-nations of r and R(12.3-12.3.3)are only intended to present a meaningful way of considering the approximate precision of this test method.The data in Table1should not be rigorously applied to acceptance or rejection of material,as those data are specific to the round robin and may not be representative of other lots,conditions,materials,or ers of this test method should apply the principles outlined in Practice E691to generate data specific to their laboratory and materi-als,or between specific laboratories.The principles of12.3-12.3.3would then be valid for each data.If S r and S R have been calculated from a large enough body of data,and for test results that were averages from testing one specimen:12.3.1Repeatability Limit,r(Comparing two test results for the same material,obtained by the same operator using the 6Supporting data are available from ASTM Headquarters.Request RR:D20-1123.TABLE2Precision Data Summary—Polyethylene DensityMaterial Average Density,g/cm3S r A S R B r C R D10.91960.000290.001060.000820.004520.93190.000120.000800.000340.002330.95270.000330.001160.000930.003340.96230.000620.001140.001800.0033A Sr=within-laboratory standard deviation for the indicated material.It is obtained by pooling the within-laboratory standard deviations of the test results from all of the participating laboratories.B SR =between-laboratories reproducibility,expressed as standard deviation,for the indicated material.C r=within-laboratory repeatability limit=2.8Sr .D R=between-laboratories reproducibility limit=2.8SR.same equipment on the same day)—The two test results should be judged not equivalent if they differ by more than the r value for that material.12.3.2Reproducibility Limit,R (Comparing two test results for the same material,obtained by different operators using different equipment in different laboratories)—The two test results should be judged not equivalent if they differ by more than the R value for that material.12.3.3Any judgment in accordance with 12.2.1or 12.2.2would have an approximate 95%(0.95)probability of being correct.12.3.4Bias —There are no recognized standards by which to estimate the bias of this test method.13.Keywords13.1density;film;gradient;plaque;polyolefins;polyeth-ylene;polypropylene;preparationAPPENDIXES(Nonmandatory Information)X1.FLOAT CALIBRATION—ALTERNATIVE TEST METHODX1.1This test method of float calibration has been found by one laboratory to save time and give the same accuracy as the standard test method.Its reliability has not been demon-strated by round-robin data.X1.1.1Prepare a homogeneous solution whose density is fairly close to that of the float in question.X1.1.2Fill a graduate about 3⁄4full with the solution,drop in the float,stopper,and place in a thermostatted water bath near 23°C.Fill a tared two-arm pycnometer (Test Method D 941,or equivalent)with the solution.Place the pycnometer in the bath.X1.1.3Vary the bath temperature until the solution density is very near to that of the float.(If the float was initially on the bottom of the graduate,lower the bath temperature until the float rises;if the float floated initially,raise the bath tempera-ture until the float sinks to the bottom.)X1.1.4Change the bath temperature in the appropriate direction in increments corresponding to solution density increments of about 0.0001g/cm 3until the float reverses direction of movement as a result of the last change.This must be done slowly (at least 15-min intervals between incremental changes on the temperature controller).Read the volume of liquid in the pycnometer.X1.1.5Change the bath temperature in increments in the opposite direction,as above,until a change in the float position again occurs.Read the volume of liquid in the pycnometer.N OTE X1.1—The float should rise off the bottom of its own volition.As a precaution against surface tension effects when the float is floating,the float should be pushed about halfway down in the liquid column and then observed as to whether it rises or falls.For this purpose,a length of Nichrome wire,with a small loop on the lower end and an inch or so of length extending above the liquid surface,is kept within the graduate throughout the course of the run.To push a floating float down,the cylinder is unstoppered and the upper wire end grasped with tweezers for the manipulations.The cylinder is then quickly restoppered.X1.1.6Remove the pycnometer from the bath,dry the outside,and set aside until the temperature reaches ambient temperature.Weigh and calculate the “in vacuo”mass of solution to ing the average of the two observed solution volumes,calculate the density of the solution to 0.0001g/cm 3.This solution density is also the float density.X1.1.7The pycnometer used should be calibrated for vol-ume from the 23°C calibration,although the reading is taken at a different temperature.The alternative test method is based on a number of unsupported assumptions but generally gives the same results as that described in 7.2within the accuracyTABLE 3Precision Data—Density,g/cm 3Material Number ofLaboratoriesDensity,g/cm 3S r A S R B r C R DB 70.91390.000290.000880.000810.00245F 80.91770.000180.000790.000510.00221G 80.92200.000280.000710.000780.00197A 110.93560.000360.001050.001000.00294E 110.95280.000460.001180.001290.00331C 100.96190.001000.001000.001030.00281D90.96330.000360.001370.001010.00384AS r =within-laboratory standard deviation for the indicated material.It is obtained by pooling the within-laboratory standard deviations of the test results from all of the participating laboratories.BS R =between-laboratories reproducibility,expressed as standard deviation,for the indicated material.Cr =within-laboratory repeatability limit =2.8S r .DR =between-laboratories reproducibility limit =2.8S R .TABLE 4Density,g/cm 3,Samples Prepared in Accordance WithPractice D 2839MaterialNumber ofLaboratoriesDensity,g/cm 3S r A S R B r C R D B 100.91390.000260.000780.000720.00219F 120.91790.000200.000780.000550.00220G 130.92220.000300.000730.000850.00206A 150.93570.000410.000800.001150.00225E 140.95300.000390.000920.001090.00258C 110.96150.000300.000730.000850.00206D100.96260.000530.001090.001480.00305AS r =within-laboratory standard deviation for the indicated material.It is obtained by pooling the within-laboratory standard deviations of the test results from all of the participating laboratories.BS R =between-laboratories reproducibility,expressed as standard deviation,for the indicated material.Cr =within-laboratory repeatability limit =2.8S r .DR =between-laboratories reproducibility limit =2.8S R.required.In case of disagreement,the method described in7.2shall be the referee method.X2.GRADIENT TUBE PREPARATIONX2.1Method A—Stepwise Addition:X2.1.1Using the two liquids that will give the desireddensity range,and sensitivity(S)in grams per cubic centimetreper millimetre,prepare four or more solutions such that eachdiffers from the next heavier by80S g/cm3.The number ofsolutions will depend upon the desired density range of thecolumn and shall be determined as follows:Numbers of solutions to prepare density2gradient(X2.1)column~Note X2.1!5~11D22D1!/80S(X2.1)where:D2=upper limit of density range desired,D1=lower limit of density range desired,andS=sensitivity,in grams per cubic centimetre per milli-metre.N OTE X2.1—Correct the value of(1+D2−D1)/80S to the nearestwhole number.To prepare these solutions,proceed as follows:Using the hydrometers,mix the two liquids in the proportions necessary to obtain the desired solutions.Remove the dissolved air from the solutions by gentle heating or an applied vacuum.Then check the density of the solutions at2360.1°C by means of the hydrometers and,if necessary,add the appropriate air-free liquid until the desired density is obtained.N OTE X2.2—Where aqueous mixtures are used,0.5%aqueous sodium acetate should be used to prepare the mixture.This reduces the formation of bubbles from dissolution.N OTE X2.3—In order to obtain a linear gradient in the tube,it is very important that the solutions be homogeneous and at the same temperature when their densities are determined.It is also important that the density difference between the solutions consecutively introduced into the tube be equal.X2.1.2By means of a siphon or pipet,fill the gradient tube with an equal volume of each liquid starting with the heaviest, taking appropriate measures to prevent air from being dis-solved in the liquid.After the addition of the heaviest liquid, very carefully and slowly pour an equal volume of the second heaviest liquid down the side of the column by holding the siphon or pipet against the side of the tube at a slight angle. Avoid excess agitation and turbulence.In this manner,the “building”of the tube shall be completed.N OTE X2.4—Density gradients may also be prepared by reversing the procedure described in X2.1.1and X2.1.2.When this procedure is used, the lightest solution is placed in the tube and the next lightest solution is very carefully and slowly“placed”in the bottom of the tube by means of a pipet or siphon which just touches the bottom of the tube.In this manner the“building”of the tube shall be completed.X2.1.3If the tube is not already in a constant-temperature bath,transfer the tube,with as little agitation as possible,to the constant-temperature bath maintained at2360.1°C.The bath level should approximately equal that of the solution in the tube,and provision should be made for vibrationless mounting of the tube.X2.1.4For every254mm of length of tube,dip a minimum offive clean calibratedfloats,spanning the effective range of the column,into the less dense solvent used in the preparation of the gradient tube and add them to the tube.By means of a stirrer(for example,a small coiled wire or other appropriate stirring device)mix the different layers of the tube gently by stirring horizontally until the least dense and most densefloats span the required range of the gradient tube.If,at this time,it is observed that thefloats are“bunched”together and not spread out evenly in the tube,discard the solution and repeat the procedure.Then cap the tube and keep it in the constant-temperature bath for a minimum of24h.X2.1.5At the end of this time,plot the density offloats versus the height offloats to observe whether or not a fairly smooth and nearly linear curve is obtained.Some small irregularities may be seen,but they should be slight.Whenever an irregular curve is obtained,the solution in the tube shall be discarded and a new gradient prepared.N OTE X2.5—Gradient systems may remain stable for several months. X2.2Method B—Continuous Filling with Liquid Entering Gradient Tube Becoming Progressively Less Dense:X2.2.1Assemble the apparatus as shown in Fig.X2.1,using beakers of the same diameter.Then select an appropriate amount of two suitable liquids which previously have been carefully deaerated by gentle heating or an applied vacuum. Typical liquid systems for density-gradient tubes are listed in Table1.The volume of the more dense liquid used in the mixer (Beaker B shown in Fig.X2.1)must be equal to at least one half of the total volume desired in the gradient tube.An FIG.X2.1Apparatus for Gradient TubePreparationestimate of the volume of the less dense liquid required in Beaker A to establishflow from A to B can be obtained from the following inequality:V A.d B V B/d A(X2.2) where:V A=starting liquid volume in Beaker A,V B=starting liquid volume in Beaker B,d A=density of the starting liquid in Beaker A,andd B=density of the starting liquid in Beaker B.A small excess(not exceeding5%)over the amount indicated by the preceding equality will induce the required flow from A toB and yield a very nearly linear gradient column.X2.2.2Place an appropriate volume of the denser liquid into Beaker B of suitable size.Prime the siphon between Beaker B and the gradient tube with liquid from Beaker B and then close the stopcock.The delivery end of this siphon should be equipped with a capillary tip forflow control.N OTE X2.6—Techniques acceptable for transfer of liquid into the gradient tube are siphon/gravity,vacuum-filling,use of a peristatic pump, or any other technique useful to transfer liquids in a controlled manner.It is important to control theflow in order to maintain a desirable gradient. X2.2.3Place an appropriate volume of the less dense liquid into Beaker A.Prime the siphon between Beakers A and B with the liquid from Beaker A and close the stopcock.Start the highspeed,propeller-type stirrer in Beaker B and adjust the speed of stirring such that the surface of the liquid does not fluctuate greatly.X2.2.4Start the delivery of the liquid to the gradient tube by opening the necessary siphon-tube stopcocks simultaneously. Adjust theflow of liquid into the gradient tube at a very slow rate,permitting the liquid toflow down the side of the tube.Fill the tube to the desired level.N OTE X2.7—Preparation of a suitable gradient tube may require1to 11⁄2h or longer,depending upon the volume required in the gradient tube. X2.3Method C—Continuous Filling with Liquid Entering Gradient Tube Becoming Progressively More Dense:X2.3.1This method is essentially the same as Method B with the following exceptions:X2.3.2The lighter of the two liquids is placed in Beaker B. X2.3.3The liquid introduced into the gradient column is introduced at the bottom of the column.Thefirst liquid introduced is the lighter end of the gradient and is constantly pushed up in the tube as the liquid being introduced becomes progressively heavier.X2.3.4The liquid from Beaker A must be introduced into Beaker B by directflow from the bottom of Beaker A to the bottom of Beaker B,rather than being siphoned over as it is in Method B.Filling the tube by this method may be done more rapidly than by Methods A or B.The stopcock between Containers A and B should be of equal or larger bore than the outlet stopcock.A schematic drawing of the apparatus for Method C is shown in Fig.X2.2.REFERENCES (1)Linderstrøm-Lang,K.,“Dilatometric Ultra-Micro-Estimation of Pep-tidase Activity,”Nature,NATRA,V ol139,1937,p.713.(2)Linderstrøm-Lang,K.,and Lanz,H.,“Enzymic Histochemistry XXIXDilatometric Micro-Determination of Peptidase Activity,”Comptesrendus des gravaus de laboratorie Carlsberg,Serie Chimique,V ol21,1938,p.315.(3)Linderstrøm-Lang,K.,Jacobsen,O.,and Johansen,G.,“Measurementof the Deuterium Content in Mixtures of H2O and D2O,”ibid.,V ol23,1938,p.17.(4)Jacobsen,C.F.,and Linderstrøm-Lang,K.,“Method for Rapid Deter-mination of Specific Gravity,”Acta Physiologica Scandinavica,AP-SCA,V ol1,1940,p.149.(5)Boyer,R.F.,Spencer,R.S.,and Wiley,R.M.,“Use of Density-Gradient Tube in the Study of High Polymers,”Journal of Polymer Science,JPSCA,V ol1,1946,p.249.(6)Anfinsen,C.,“Preparation and Measurement of Isotopic Tracers:ASymposium Prepared for the Isotope Research Group,”Edwards,J.W.,Publishers,Ann Arbor,MI,1946,p.61.(7)Tessler,S.,Woodberry,N.T.,and Mark,H.,“Application of theDensity-Gradient Tube in Fiber Research,”Journal of Polymer Sci-ence,JPSCA,V ol1,1946,p.437.(8)Low,B.W.,and Richards,F.M.,“The Use of the Gradient Tube forthe Determination of Crystal Densities,”Journal of the American Chemical Society,JACSA,V ol74,1952,p.1660.(9)Sperati,C.A.,Franta,W.A.,and Starkweather,H.W.,Jr.,“TheMolecular Structure of Polyethylene V,the Effect of Chain Branching and Molecular Weight on Physical Properties,”Journal of the Ameri-can Chemical Society,JACSA,V ol75,1953,p.6127.(10)Tung,L.H.,and Taylor,W.C.,“An Improved Method of PreparingDensity Gradient Tubes,”Journal of Polymer Science,JPSCA,V ol 21,1956,p.144.(11)Mills,J.M.,“A Rapid Method of Construction Linear DensityGradient Columns,”Journal of Polymer Science,V ol19,1956,p.585.(12)Wiley,R.E.,“Setting Up a Density Gradient Laboratory,”PlasticsTechnology,PLTEA,V ol8,No.3,1962,p.31.FIG.X2.2Apparatus for Gradient TubePreparation。
