ASTM D1896-2009 Standard Practice for Transfer Molding Test Specimens of Thermosetting Compounds.pdf

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1、Designation: D1896 09Standard Practice forTransfer Molding Test Specimens of ThermosettingCompounds1This standard is issued under the fixed designation D1896; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revisio

2、n. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope*1.1 This practice covers a general procedure for the transfermolding of mechanical and electrical test specimens of ther-mosetting mo

3、lding materials.NOTE 1The utility of this practice has been demonstrated for themolding of thermosetting molding compounds exhibiting intermediateviscosity non-Newtonian flow.1.2 The values stated in either SI or inch-pound units are tobe regarded separately as standard. The values stated in eachsys

4、tem are not always exact equivalents; therefore, eachsystem shall be used independently of the other. Combiningvalues from the two systems may result in nonconformancewith this practice.1.3 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is th

5、eresponsibility 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.NOTE 2There is no known ISO equivalent to this standard.2. Referenced Documents2.1 ASTM Standards:2D731 Test Method for Molding I

6、ndex of ThermosettingMolding PowderD883 Terminology Relating to PlasticsD957 Practice for Determining Surface Temperature ofMolds for PlasticsD3123 Test Method for Spiral Flow of Low-Pressure Ther-mosetting Molding CompoundsD3795 Test Method for Thermal Flow, Cure, and BehaviorProperties of Pourable

7、 Thermosetting Materials by TorqueRheometer3. Terminology3.1 Definitions:3.1.1 GeneralDefinitions of terms applying to this prac-tice appear in Terminology D883.3.1.2 transfer molding, na method of forming articles byfusing a plastic material in a chamber and then forcingessentially the whole mass i

8、nto a hot mold where it solidifies.3.2 Definitions of Terms Specific to This Standard:3.2.1 breathing, vthe operation of opening a mold or pressfor a very short period of time at an early stage in the processof cure.3.2.1.1 DiscussionBreathing allows the escape of gas orvapor from the molding materi

9、al and reduces the tendency ofthick moldings to blister.3.2.2 cavity (of a mold), nthe space within a mold to befilled to form the molded product.3.2.3 clamp pressure, nthe pressure applied to the mold tokeep it closed, in opposition to the fluid pressure of thecompressed molding material.3.2.4 fill

10、 time, nthe time required to fill each cavity usedin the mold. Fill times can be critical to well molded parts (seeNote 3 under 4.4).3.2.5 minimum plunger pressure, nthe minimum pressure,on the ram, required to just fill each cavity used in the mold ata specified temperature and reasonable fill time

11、.3.2.6 vent, na hole, slot, or groove provided in a mold ormachine to allow air and gas to escape during molding,extrusion, or forming.4. Significance and Use4.1 Transfer molding is particularly suited to thermosettingmaterials of intermediate plasticity. Fixed molding parameterscannot be specified

12、for each type of material. Molding com-pounds of the same type come in many different plasticitiesmeasured in accordance with Test Methods D731, D3123, and1This practice is under the jurisdiction ofASTM Committee D20 on Plastics andis the direct responsibility of Subcommittee D20.09 on Specimen Prep

13、aration.Current edition approved Dec. 1, 2009. Published December 2009. Originallyapproved in 1961. Last previous edition approved in 2004 as D1896 - 99(2004).DOI: 10.1520/D1896-09.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.or

14、g. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.1*A Summary of Changes section appears at the end of this standard.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States

15、.D3795. Consequently, for a given material type, the moldingparameters required to produce satisfactory test specimens willoften vary dependent on the plasticity of the specific materialgrade.4.2 The mold shown in this practice provides for a set offive specimens. However, if only certain specimens

16、are desired,the other cavities can be blocked by inserting gate blanks.4.3 Typically, breathing of the mold is not required torelease trapped volatile matter as the gas is free to flow fromthe vent end of the mold. This is a particular advantage forheat-resistant compounds and reduces the tendency f

17、or moldedspecimens to blister at high exposure temperatures.4.4 Flow and knit lines in a molded piece are often sites ofmechanical or electrical weakness and can be found in somedegree of severity throughout the molded piece. The semisolidmolding compound passing through the gate is subject tonon-Ne

18、wtonian flow and, consequently, wrinkles and folds asit travels down the mold cavity. Fibers and other reinforce-ments in the molding compound align with the flow patternand, consequently, can orient perpendicular to the axis of thebar at the center and parallel at the surface of the bar. Moldtemper

19、ature, thermal conductivity and plasticity of the moldingcompound, degree of preheat, and plunger pressure are param-eters that influence the time to fill the mold cavities and theformation of knit lines.NOTE 3If the temperature of the mold is held constant and the plungerpressure varied for a desig

20、nated thermosetting molding compound, twoextreme characteristic conditions can be obtained. If the pressure is low,then the vent end of the cavity will not fully fill, and weld lines will formby incomplete knitting of the material. If the pressure is too high, the moldcavity will fill fast, the outs

21、ide of the specimen will case harden while thepressure is still forcing material out the vent, and a ball-and-socket grainstructure will be obtained. A ball-and-socket structure is an indication ofthe molding condition, and lower test data will result.4.5 Thermosetting compounds containing long-fibe

22、r fillerssuch as glass roving, chopped cloth, or shavings can be usedbut are not recommended for transfer molding. These fillermaterials tend to break, tear, or ball in passing through thegates of the mold, thereby not optimizing their potentialstrength.4.6 The Izod impact strength of transfer molde

23、d specimensof molding compounds containing short fibers will generally belower than the values obtained using compression-moldingmethods. Quite often the impact strength will vary along theaxis of the bar due to molding parameters, flow pattern, andfiber orientation.4.7 The flexural and tensile stre

24、ngth of transfer moldedspecimens of molding compounds containing short fibers willgenerally be higher than the values obtained usingcompression-molding methods. Flexural tests are particularlysensitive to transfer molding due to the thin resin skin formedat the surface of the bar during the final fi

25、lling of the cavity andpressure buildup.5. Apparatus5.1 PressA hydraulic press designed to develop andmaintain accurately any desired pressure between 7 and 85MPa (1000 and 12 000 psi) on the plunger to 61 MPa (6150psi) and have a minimum plunger loading capacity of 230 cm3(14 in.3) (see Note 4). Th

26、e clamp pressure shall be at least 20 %higher than the plunger pressure.NOTE 4Plunger molding pressure under actual molding conditions isa variable that is difficult to control. Pressure standardization should becarried out on an empty cavity with the plunger against the mold-stopplate. The speed of

27、 the moveable platen is not important as the mold isclosed before the plunger operates. A ram speed of 3.6 m/min (140in./min) and a plunger speed of 2.2 m/min (85 in./min) have been foundsatisfactory when the mold is not loaded. The plunger speed is subject tothe flow properties of the molding mater

28、ial when the plunger cavity isloaded with molding compound.5.2 MoldA five-cavity mold similar to that shown in Fig.1 has been found satisfactory, although molds with fewercavities or different configurations of the tension specimen canbe used. Specimens can be eliminated by blocking the runnersto pa

29、rticular cavities and reducing injection pressure and shotsize accordingly. The gates for each of the cavities in this moldare 6.4 mm wide by 1.52 mm deep (14 by 0.060 in.). Suitableventing must be provided from each cavity. A cavity surfacefinish of SPI-A3 is recommended3, as is chrome plating of t

30、hemold surface.NOTE 5Although the mold shown is generally useful, it is preferred touse a multiple-identical-cavity mold with a symmetrical layout of runnersand cavities. In either case, it is important to describe the mold in thereport on the specimen preparation.5.3 Heating SystemAny convenient me

31、thod of heating thepress platens and plunger cavity can be used, provided the heatsource is constant enough to maintain the mold and plungertemperature within 63C (65F).5.4 Temperature IndicatorTypically, a surface pyrometeris used to measure the temperature of the mold surface asspecified in Practi

32、ce D957.5.5 PreformingAny preforming equipment or press canbe used that will provide a satisfactory preform of material forthe plunger and ease of handling in the electronic preheater.6. Conditioning6.1 Molding compounds are generally preformed, electroni-cally preheated, and molded from the compoun

33、d in theas-received condition.6.2 Condition molding compounds known to contain a highpercentage of moisture for 30 min at 90 6 3C (194 6 5F) ina forced-draft oven and preform immediately afterward. Amaximum depth of 15 mm (0.6 in.) is recommended for themolding compound in the oven tray. Store the p

34、reformedmaterial in a desiccator over anhydrous calcium chloride atroom temperature until ready to preheat and mold.6.3 In the case of a referee test, prepare the preform materialas indicated in 6.2.7. Procedure7.1 Choose and set the temperatures of the mold andplunger cavity based on the manufactur

35、ers recommendation,3The sole source of supply of the mold comparison kits known to the committeeat this time is The Moldmakers Division of the Society of the Plastics Industry, Inc.,1667 K St., NW, Suite 1000 - Washington, DC 20006. If you are aware of alternativesuppliers, please provide this infor

36、mation to ASTM International Headquarters.Your comments will receive careful consideration at a meeting of the responsibletechnical committee1, which you may attend.D1896 092the relevant material specification, or previous experience withthe particular type of material being used and its plasticity.

37、Typically, the temperature will be in the range from 150 to175C (302 to 347F).7.2 Uniformly preheat the desired shot size of preformedmaterial of the compound to the preheat temperature specifiedby the manufacturer or the relevant material specification.NOTE 6The temperature of the preformed materia

38、l after electronicpreheating may be determined by a needle-type pyrometer of low thermalcapacity.7.3 Immediately remove the preheated preformed materialfrom the preheater, place it in the plunger cavity, close thepress, and apply molding pressure within a period of 5 s aftercompletion of preheating.

39、7.4 Adjust the plunger molding pressure to the plasticity ofthe material by increasing the minimum plunger pressure by10 %, after first determining the minimum plunger pressure(MPP) for the material.7.5 The minimum cure time shall be 3 min as measuredfrom the time the pressure on the plunger is with

40、in 6.9 MPa(1000 psi) of the preset pressure.7.6 No knockouts are required to remove the moldedspecimens, runner system, and cull from the mold. The wholemolded spider can be removed as a unit from the mold with theaid of compressed air.8. Report8.1 Report the following information:8.1.1 Date, place,

41、 and time of the molding,8.1.2 Description of material being molded (type, grade,color, and lot number),8.1.3 Premolding treatment of the material,8.1.4 Identification of the mold being used,8.1.5 Type and number of specimens molded,8.1.6 Description of the cavity gating, and8.1.7 Molding conditions

42、, including the following:8.1.7.1 All temperature setpoints,8.1.7.2 Pressures, and8.1.7.3 Cycle times.9. Keywords9.1 test specimens; thermosetting compounds;transfer-moldingNOTE 1Thermometer wells shall be 8 mm (516 in.) in diameter to permit use of a readily available thermometer.FIG. 1 Five-Cavity

43、 Transfer Mold for Thermosetting Plastic Test Specimens (Steam Cores Not Shown)D1896 093SUMMARY OF CHANGESCommittee D20 has identified the location of selected changes to this standard since the last issue,D1896 - 99(2004), that may impact the use of this standard. (December 1, 2009)(1) Revised the

44、ISO equivalency statement.(2) Updated mold finish designation and source of standards.(3) Removed permissive language in the procedural sections.ASTM International takes no position respecting the validity of any patent rights asserted in connection with any item mentionedin this standard. Users of

45、this standard are expressly advised that determination of the validity of any such patent rights, and the riskof infringement of such rights, are entirely their own responsibility.This standard is subject to revision at any time by the responsible technical committee and must be reviewed every five

46、years andif not revised, either reapproved or withdrawn. Your comments are invited either for revision of this standard or for additional standardsand should be addressed to ASTM International Headquarters. Your comments will receive careful consideration at a meeting of theresponsible technical com

47、mittee, which you may attend. If you feel that your comments have not received a fair hearing you shouldmake your views known to the ASTM Committee on Standards, at the address shown below.This standard is copyrighted by ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 1

48、9428-2959,United States. Individual reprints (single or multiple copies) of this standard may be obtained by contacting ASTM at the aboveaddress or at 610-832-9585 (phone), 610-832-9555 (fax), or serviceastm.org (e-mail); or through the ASTM website(www.astm.org). Permission rights to photocopy the standard may also be secured from the ASTM website (www.astm.org/COPYRIGHT/).D1896 094