1、Designation: D 1896 99 (Reapproved 2004)Standard Practice forTransfer Molding Test Specimens of ThermosettingCompounds1This standard is issued under the fixed designation D 1896; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the
2、year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) 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
3、 of ther-mosetting molding 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 val
4、ues stated in eachsystem may not be exact equivalents; therefore, each systemshall be used independently of the other. Combining valuesfrom the two systems may result in nonconformance with thispractice.1.3 This standard does not purport to address all of thesafety concerns, if any, associated with
5、its use. It is theresponsibility 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 similar, or equivalent, ISO standard.2. Referenced Documents2.1 ASTM Standards:2D 731 Test Met
6、hod for Molding Index of ThermosettingMolding PowderD 883 Terminology Relating to PlasticsD 957 Practice for Determining Surface Temperature ofMolds for PlasticsD 3123 Test Method for Spiral Flow of Low-PressureThermosetting Molding CompoundsD 3795 Test Method for Thermal Flow and Cure Propertiesof
7、Thermosetting Plastics by Torque Rheometer3. Terminology3.1 Definitions:3.1.1 GeneralDefinitions of terms applying to this prac-tice appear in Terminology D 883.3.1.2 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 D 731, D 3123, andD 3795. For this reason, a material may mold satisfactorilyunder one set of fixed parameters, while the same type ofmaterial with a different p
13、lasticity may require a different set ofparameters to produce satisfactory test specimens.4.2 The mold shown in this practice provides for a set offive specimens. However, if only certain specimens are desired,the other cavities may be blocked by inserting gate blanks.4.3 Typically, breathing of the
14、 mold may not be required torelease trapped volatile matter as the gas is free to flow fromthe vent end of the mold. This is a particular advantage for1This practice is under the jurisdiction ofASTM Committee D20 on Plastics andis the direct responsibility of Subcommittee D20.09 on Specimen Preparat
15、ion.Current edition approved Nov. 1, 2004. Published January 2005. Originallyapproved in 1961. Last previous edition approved in 1999 as D 1896 - 99.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStanda
16、rds 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.heat-resistant compounds and re
17、duces the tendency for moldedspecimens to blister at high exposure temperatures.4.4 Flow and knit lines in a molded piece are often sites ofmechanical or electrical weakness. Knit lines may be found insome degree of severity throughout the molded piece. Thesemisolid molding compound passing through
18、the gate issubject to non-Newtonian flow and, consequently, wrinkles andfolds as it travels down the mold cavity. Fibers and otherreinforcements in the molding compound align with the flowpattern and, consequently, may mold perpendicular to the axisof the bar at the center and parallel at the surfac
19、e of the bar.Mold temperature, thermal conductivity and plasticity of themolding compound, degree of preheat, and plunger pressureare parameters that influence the time to fill the mold cavitiesand the formation of knit lines.NOTE 3If the temperature of the mold is held constant and the plungerpress
20、ure varied for a designated 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 wi
21、ll fill fast, the outside 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 compound
22、s containing long-fiber 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 stre
23、ngth of transfer molded 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 fle
24、xural and tensile strength 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 b
25、ar during the final filling 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 cm314 in.3
26、see Note 4). The 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-stoppla
27、te. The speed of 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 m
28、olding material 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 maybe used. Specimens may be eliminated by blocking the
29、runnersto particular 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. Surfaces of thecavity should be finished to SPI-SPE #2.3Chrome pla
30、ting ofthe mold surface is recommended.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
31、 SystemAny convenient method of heating thepress platens and plunger cavity may be used, provided theheat source is constant enough to maintain the mold andplunger temperature within 63C 65F.5.4 Temperature IndicatorTypically, a surface pyrometeris used to measure the temperature of the mold surface
32、 asspecified in Practice D 957.5.5 PreformingAny preforming equipment or press maybe 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
33、molded from the compound 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. Thedepth of the molding compound in the oven tray should notexceed 15 mm 0.6 in.
34、Store the preformed material in adesiccator over anhydrous calcium chloride at room tempera-ture 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 t
35、he manufacturers recommendation,the relevant material specification, or previous experience withthe particular type of material being used and its plasticity.Typically, the temperature will be in the range from 150 to175C 302 to 347F.7.2 Uniformly preheat the desired shot size of preformedmaterial o
36、f the compound to the preheat temperature specifiedby the manufacturer or the relevant material specification.NOTE 6The temperature of the preformed material after electronicpreheating may be determined by a needle-type pyrometer of low thermalcapacity.3The sole source of supply of the mold comparis
37、on kits known to the committeeat this time is D-M-E Co., 29111 Stephenson Highway, Madison Heights, MI 48071.If you are aware of alternative suppliers, please provide this information to ASTMInternational Headquarters. Your comments will receive careful consideration at ameeting of the responsible t
38、echnical committee1, which you may attend.D 1896 99 (2004)27.3 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.7.4 Adjust the plunger molding pressur
39、e 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 within 6.9 MPa1000 psi of the preset press
40、ure.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, and time of the molding,8.1.2 Descripti
41、on 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, including the following:8.1.7.1 All te
42、mperature 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 Transfer Mold for Thermosetting Plastic T
43、est Specimens (Steam Cores Not Shown)D 1896 99 (2004)3SUMMARY OF CHANGESCommittee D20 has identified the location of selected changes to this standard since the last issue,D 1896 - 99, that may impact the use of this standard. (November 1, 2004)(1) Reapproved without any change.ASTM International ta
44、kes no position respecting the validity of any patent rights asserted in connection with any item mentionedin this standard. Users of 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 r
45、esponsibility.This standard is subject to revision at any time by the responsible technical committee and must be reviewed every five years andif not revised, either reapproved or withdrawn. Your comments are invited either for revision of this standard or for additional standardsand should be addre
46、ssed to ASTM International Headquarters. Your comments will receive careful consideration at a meeting of theresponsible technical committee, 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 t
47、he address shown below.This standard is copyrighted by ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959,United States. Individual reprints (single or multiple copies) of this standard may be obtained by contacting ASTM at the aboveaddress or at 610-832-9585 (phone), 610-832-9555 (fax), or serviceastm.org (e-mail); or through the ASTM website(www.astm.org).D 1896 99 (2004)4
