1、Designation: D5224 12Standard Practice forCompression Molding Test Specimens of ThermosettingMolding Compounds1This standard is issued under the fixed designation D5224; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of l
2、ast revision. 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 the general principles to be fol-lowed when compression molding test specimens of thermo-setting
3、molding compounds, such as phenolics, aminoplastics,melamine phenolics, epoxies, and unsaturated polyesters.1.2 Molding conditions are given for amino, phenolic, andallyl molding compounds. The exact molding conditions willvary from material to material, and, if not incorporated in thematerial speci
4、fication, shall be agreed upon between thepurchaser and the supplier or determined by previous experi-ence with the particular type of material being used1.3 The values stated in SI units are to be regarded asstandard. The values in parentheses are given for informationonly.1.4 This standard does no
5、t purport to address all of thesafety concerns, if any, associated with 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 1This standard and ISO 295 address
6、the same subject matter,but differ in technical content.2. Referenced Documents2.1 ASTM Standards:2D638 Test Method for Tensile Properties of PlasticsD883 Terminology Relating to Plastics2.2 ISO Standard:ISO 295 PlasticsCompression Molding Test Specimensof Thermosetting Materials3ISO 3167 PlasticsMu
7、ltipurposeTest Specimens33. Terminology3.1 DefinitionsFor definitions of terms pertaining to plas-tics used in this practice, see Terminology D883.3.2 Definitions of Terms Specific to This Standard:3.2.1 breathe step, nin plastics molding, the part of themolding cycle in which the mold halves are op
8、ened momen-tarily, prior to curing, to release volatiles from the molded part.3.2.2 skin, nin plastics molding, the thin resin-rich layer(skin) on the surface of the molded part.3.2.3 skin effect, nin plastics testing, the positive ornegative effect on the results of some standard tests attributable
9、to the skin.4. Summary of Practice4.1 Compression molded test specimens are produced byloading a mold cavity with some form of the molding material,applying a specified pressure to the mating surface for aspecified time and at a specified temperature, and then remov-ing the part from the cavity.5. S
10、ignificance and Use5.1 The conditions at which compounds are molded areknown to influence the properties of the specimens. The degreeof cure, elimination of knit-lines between particles, density ofthe part, and degradation of the polymer are among thosefactors which will be affected by the molding c
11、onditions. Thusit is important to conform to a standard set of conditions inorder to have a valid comparison of properties betweendifferent compounds and different batches of the same com-pound.5.2 Molded specimens showing evidence of low-densityareas due to trapped gases shall be discarded. A breat
12、he stepcan be incorporated to eliminate this situation. If used, it iscritical that the breathe step be as brief as possible to avoidprecuring of the compound before full pressure is appliedleading to poorly “knitted” areas and lower strength in themolded specimen.6. Apparatus6.1 Molds:1This practic
13、e is under the jurisdiction ofASTM Committee D20 on Plastics andis the direct responsibility of Subcommittee D20.09 on Specimen Preparation.Current edition approved April 1, 2012. Published May 2012. Originallyapproved in 1992. Last previous edition approved in 2006 as D5224 - 00 (2006).DOI: 10.1520
14、/D5224-12.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3ISO Standards Handbook 21, Vol 2, Plastics, 2nd Ed
15、., 1990, available fromAmerican National Standards Institute (ANSI), 25 W. 43rd St., 4th Floor, New York,NY 10036.1*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.6.1.1
16、 The mold shall be made of steel, able to withstand themolding temperatures and pressures. The mold shall be de-signed such that the compressive mold force is transferred tothe molding material with no appreciable loss. The moldsshown in Figs. 1 and 2 are recommended for maintaining themaximum force
17、 on the material. They are of the three-platedesign; consisting of a shell or floating plate, with upper andlower compression plates. Molds may be of single or multiplecavity design.NOTE 2Semi-positive molds can be used, and for materials such asamino compounds, are preferred.6.1.2 The majority of t
18、ests will use bars 12.7 mm (0.5 in.) inwidth by 127 mm (5 in.) or 64 mm (2.5 in.) in length, discs 51mm (2 in.) or 102 mm (4 in.) in diameter or an appropriatetensile bar as described in Test Method D638 or the multi-purpose design from ISO 3167. The mold shall be capable ofmolding thickness from 1.
19、5 mm (0.06 in.) to 12.5 mm (0.5 in.).Some procedures such as flame testing require thinner speci-mens. In all cases the ASTM Standard Test Procedure to beused shall be consulted for the dimensions of the required testspecimens.6.1.3 If at all possible, specimens shall be molded directly todimension,
20、 rather than machined from a plaque to maintain theintegrity of any skin effect.6.1.3.1 If it is necessary for specimens to be machined fromplates or plaques, they shall not be taken from the edge of theplaque and a minimum margin of 10 mm (0.5 in.) is recom-mended. This shall be noted in the report
21、.6.1.4 A cavity draft angle not exceeding 3 can be used tofacilitate specimen removal.6.1.5 The clearance between the vertical wall of the cavityand that of the force shall not exceed 0.1 mm (0.004 in.).6.1.6 Mold surfaces finished to a roughness of 0.4 to 0.8 m(SPI-SPE #2 or equivalent4) are prefer
22、red, unless it is knownthat the particular test is not affected by a coarser surface finish.Chrome plating is recommended but not necessary. Drawpolishing of all cavity surfaces in the direction parallel to theforce will facilitate specimen removal.6.1.7 If ejector pins are used, they shall not defo
23、rm thespecimens and their placement shall be such that the pin marksare not in the area of test.6.1.8 The mold shall have a loading chamber of sufficientvolume to allow the introduction of the entire charge ofmaterial in a single loading. Preforms can be used to decreasethe required loading volume o
24、f high bulk materials. Theconditions of such preforming shall be included in the report.6.1.9 As the specimen surface facing the lower die is heatedfor a longer time and at a higher temperature in the timeinterval between filling and compression, it is recommendedthat a mark be placed on one cavity
25、face in such a position thatit will not interfere with the testing. When reporting the resultsof tests that affect the surfaces unequally, the tested surfaceshall be indicated.6.2 PressThe hydraulic press shall have a range ofpressures sufficient to insure that the specified pressure isapplied and m
26、aintained during the entire molding operation,and of maintaining that pressure within 61.5 MPa (6218 psi).6.2.1 In order to prevent precure, the press shall be capableof closing within 15 s after the placement of the material in themold. A two-speed press is preferred for this purpose. The fastappro
27、ach speed can be in the range of 200 to 400 mm/s (8 to16 in./s) while the slow closing speed of 5 mm/s (0.2 in./s) isused to prevent gas entrapment.6.3 Heating SystemMold heating can be accomplished byconduction from heated platens, heaters inserted into the molditself, by hot fluids circulated thro
28、ugh passageways in themold, or any suitable alternative. The heating system shall be4Mold comparison kits are available from the D-M-E Company, 29111 Stephen-son Highway, Madison Heights, MI 48071.FIG. 1 Single-Cavity Positive-Compression Mold for Bar TestSpecimensFIG. 2 Compression Mold for Disk Te
29、st SpecimensD5224 122capable of controlling the mold temperature to 63C (65F)from point-to-point on the mold and for the duration of themolding time.6.3.1 If the mold is heated directly, it shall be insulated fromthe press platens with a sheet of insulating material.NOTE 3It is generally preferable
30、to heat the mold electrically.6.4 Temperature-Measurement System:6.4.1 Mold TemperatureA surface pyrometer or equiva-lent means is used to measure the temperature of the moldsurface.6.4.2 Preheated Compound Temperature If the compoundis to be preheated to a definite temperature, a needle-probepyrome
31、ter or equivalent sensitive to 62C shall be used.7. Conditioning7.1 Except for referee testing and preparation of samples forelectrical tests, prior conditioning of the material is notrequired.7.2 Referee Testing: Phenolic and Amino Molding Com-pounds:7.2.1 For the referee testing of all but electri
32、cal specimens,place a sufficient quantity of material in an open tray to amaximum depth of 13 mm (0.5 in.) for 72 h in a standardlaboratory atmosphere (23 6 1C, 50 6 5 % relative humid-ity).7.2.2 For the preparation of electrical test specimens, placea sufficient sample of the molding material in an
33、 open tray toa maximum depth of 13 mm (0.5 in.). Dry in an air-circulatingoven for 30 min at 90 6 3C. Mold the material immediatelyafter conditioning.7.3 Referee Testing: Allyl Molding Compounds:7.3.1 For referee testing of all test specimens, place asufficient quantity of material in an open tray t
34、o a depth of 25mm (1 in.) for 72 h in a standard laboratory atmosphere (23 61C, 50 6 5 % relative humidity).7.4 Electronic Preheating:7.4.1 When electronic preheating is to be used (refer toMolding Conditions, Table 1), the objective is to attain aparticular temperature as rapidly as possible. Deter
35、mine theconditions necessary to attain that temperature with sparepreforms which are then discarded. Do not use this type ofpreheating when preparing electrical test specimens. Thematerial shall be transferred to the mold immediately afterpreheating to prevent cooling or premature curing.7.5 Preplas
36、tification:7.5.1 Preplastification is permissible to insure thermal andmechanical homogenization of the material. The preplasticizedmaterial shall be molded immediately after preplastification toprevent cooling or premature curing. Preplastification condi-tions shall be the subject of an agreement b
37、etween theinterested parties and shall be included in the molding report.8. Procedure8.1 Unless directed otherwise in the material specification,mold test specimens under the conditions listed in Table 1.8.1.1 The “breathe step,” if used, is done by slightly openingthe mold for a few seconds to rele
38、ase volatiles generated by thecuring process and is done after it has already been closed atthe molding temperature.8.1.2 Release agents are not normally needed as moldingcompounds have internal lubricants to facilitate mold release.If release agents are used it shall be shown that they have noinflu
39、ence on the test specimen properties. They shall be notedin the report.8.1.3 Cooling fixtures can be used to prevent warpage uponremoval of the specimens from the mold.8.2 Phenolic Molding Compounds:8.2.1 Use conditions A or B from Table 1 for impact,flexure, tension, water absorption, heat deflecti
40、on, heat-agingtests.8.2.2 Use Condition C from Table 1 for electrical testspecimens.8.3 Amino Molding Compounds:8.3.1 For urea-formaldehyde compounds use Condition Dfrom Table 1.8.3.2 For melamine-formaldehyde compounds use Condi-tion E from Table 1.8.4 Allyl Molding CompoundsUse conditions F, G, or
41、 Hfrom Table 1.8.5 Molding Pressures:8.5.1 The molding pressures shown in Table 1 are recom-mended and shall be used for all referee molding and testing.If other pressures are to be used, the oil pressure p0inTABLE 1 Molding Conditions for Compression Molding of Thermoset Molding CompoundsMolding Co
42、ndition A B C D E F G HCharge powder preformApowder or preformBpowder, pill, or granular powder or preformBpowder powder preformPreheating none electronic air oven air oven none air oven electronicPreheat temperature 104 to 115C 90C 90C 120C 107CPreheat time 30 min 60 min 10 min 25 to 30 sMolding te
43、mperatureC170C 170C 170C 150C 150C 160C 160C 160CMolding pressureD,E17 MPaE17 MPa 17 MPa 28 MPa 28 MPa 20 MPa 20 MPa 20 MPaMolding time3.2 mm thickness 5 min 3 min 5 min 4 min 5 min 5 min 3 min 3 min6.4 mm thickness 5 min12.7 mm thickness 5 minBreathing allowed allowed allowed allowed allowed when n
44、ecessary (keep brief)AA single preform, preferably approximating the molded shape, shall be used. If more than one preform is used, weld lines may affect the test value of the specimen.BWhen using preforms, the material should be preheated in powder form, then preformed and molded immediately.CMoldi
45、ng temperatures should be held to within 3C of the specified level.DMolding pressure should be held to within 2 MPa of the specified level.EHighly plastic materials may flash excessively under the molding pressure specified. If that occurs, molding pressure may be reduced to a minimum of 10 MPa, in
46、whichcase the pressure used shall be reported.D5224 123megapascals (MPa), to be displayed on the pressure gauge inorder to obtain the specified pressure p, in megapascals, isgiven by the equation:p05 p 3 A1!/A (1)where:A = the area of the press piston head, m2, andA1= the total area of the cavities,
47、 m2.9. Report9.1 Report the following information:9.1.1 Type and description of material used,9.1.2 Description of the mold,9.1.3 State of material molded (as received or with “refereetest” conditioning),9.1.4 Molding condition used (A, B, C, D, E, F, G, or H) andany variations from the listed condi
48、tion,9.1.5 Whether or not a “breathe step” was used duringmolding,9.1.6 Whether any specimens were machined, and9.1.7 Whether any release agents were used.NOTE 4A report form (Fig. 3) identifying all pertinent information isprovided for reference.FIG. 3 Compression Molding ReportD5224 12410. Precisi
49、on and Bias10.1 Inasmuch as this practice does not generate a numeri-cal result, a precision and bias estimate is not possible.However, the procedures used during molding of test speci-mens will affect the numerical results from tests done on thespecimens. Thus variabilities in the molding procedure willcontribute to variability in the final test results.11. Keywords11.1 allyl molding compound; amino molding compound;compression molding; phenolic molding compound; plastics;thermosetSUMMARY OF CHANGESCommittee D20 has identified the location o
