1、Designation: D3419 12Standard Practice forIn-Line Screw-Injection Molding Test Specimens FromThermosetting Compounds1This standard is issued under the fixed designation D3419; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the yea
2、r of last 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 injection molding test specimens of thermosetti
3、ngmaterials. It is to be used to obtain uniformity in methods ofdescribing the various steps of the injection molding processand in the reporting of those conditions. The exact moldingconditions will vary from material to material, and if notincorporated in the material specification, shall be agree
4、d uponbetween the purchaser and the supplier or determined byprevious experience with the particular type of material beingused and its plasticity.NOTE 1The utility of this practice has been demonstrated for themolding of thermosetting molding compounds exhibiting lower-viscositynon-Newtonian flow.1
5、.2 The values stated in SI units are to be regarded asstandard. The values given in parentheses are for informationonly.1.3 This standard does not purport to address all of thesafety problems, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-pr
6、iate safety and health practices and determine the applica-bility of regulatory limitations prior to use.1.4 This practice assumes the use of reciprocating screwinjection molding machines.NOTE 2This standard and ISO 10724 address the same subject matter,but differ in technical content.2. Referenced
7、Documents2.1 ASTM Standards:2D883 Terminology Relating to PlasticsD3641 Practice for Injection Molding Test Specimens ofThermoplastic Molding and Extrusion Materials2.2 ISO Standards:3ISO 10724 :1994(E)PlasticsThermosetting MouldingMaterialsInjection Moulding of Multipurpose TestSpecimensISO 3167 :1
8、993, PlasticsMultipurpose Test Specimens3. Terminology3.1 Definitions:3.1.1 GeneralDefinitions of terms applying to this prac-tice appear in Terminology D883.3.1.2 injection moldingthe process of forming a materialby forcing it, in a fluid state and under pressure, through arunner system (sprue, run
9、ner, and gate(s) into the cavity of aclosed mold.3.1.2.1 DiscussionScrew-injection molding and reaction-injection molding are types of injection molding.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
10、early stage in the processof cure.3.2.1.1 DiscussionBreathing allows the escape of gas orvapor from the molding material 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 landing (of a cavity), vthe pr
11、actice of relieving themold around the cavity (cavities), thus reducing the surfacearea of the flat mating surfaces of the mold halves.3.2.3.1 DiscussionTypical lands are 4.5 mm (316 in.) to 6mm (14 in.) in width. It is recommended that landing pads beincorporated to hold the mold open 0.0125 mm (0.
12、0005 in.) toprevent damage to the lands.4. Significance and Use4.1 This practice is subject to the definition of injectionmolding given in 3.1.2 with the further provision that within-line screw injection the plastic compound, heated in achamber by conduction and friction, is fluxed by the action of
13、1This practice 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 1975. Last previous edition approved in 2006 as D3419 - 00(2006).
14、DOI: 10.1520/D3419-12.2For 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.3Available from American National Stand
15、ards Institute (ANSI), 25 W. 43rd St.,4th Floor, New York, NY 10036, http:/www.ansi.org.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.a reciprocating screw and then
16、is forced into a hot mold whereit solidifies. Hereafter, in-line screw-injection molding will bereferred to simply as injection molding.4.2 The mold referenced in this section (see Fig. 1)isgenerally useful, and describes what have been the mostcommon specimens required for the testing of thermosets
17、. ISOspecimens and testing are gaining favor, however. PracticeD3641 and ISO 10724 describe the layout and practice forinjection molding the multi-purpose specimens in accordancewith ISO 3167.4.3 Typically, injection-molded test specimens are madewith shorter cycles than those used for similar moldi
18、ngs madeby compression, and the cycle is equal to or faster than that fortransfer molding.4.4 Breathing of the mold is not usually required to releasetrapped volatile material as the gas is free to flow from the ventend of the mold. This is particularly advantageous for heat-resistant compounds and
19、reduces the tendency for moldedspecimens to blister at high exposure temperatures.4.5 Injection molding is intended for low-viscosity com-pounds. One set of processing parameters cannot be specifiedfor all types of thermosetting materials, nor for samples of thesame material having different plastic
20、ities.4.6 Materials containing fibrous fillers such as glass roving,chopped cloth, or cellulosic fibers can be injection molded, buttheir properties will be affected depending upon how muchfiber breakdown occurs as the compound is worked by thescrew and as it passes through the system of runners and
21、 gates.The orientation of the fibers in the molded specimen will alsoaffect injection-molded properties.4.7 Flow and knit lines in a molded piece are often sites ofmechanical or electrical weakness. The fluxed material passingthrough the gate wrinkles and folds as it proceeds into the moldcavity. Kn
22、it lines are found to some degree throughout themolded piece; and can affect test results. Fibers and otherreinforcements in the molding compound align with the flowpattern and, generally, are perpendicular to the axis of the barat its center and parallel at its surface.4.7.1 Placement and size of g
23、ates and vents can be used tominimize flow and knit lines, for example, side gating of barswill minimize the tendency of the material to fold onto itself asthe material front proceeds through the length of the mold.4.8 The Izod impact strength of injection-molded specimenscontaining short fibers wil
24、l generally be lower than the valuesobtained using compression molding methods. The impactstrength can also vary along the axis of the bar due to moldingparameters, flow patterns, and fiber orientation.4.9 The flexural and tensile strength of injection-moldedspecimens of molding compounds containing
25、 short fibers willgenerally be higher than the values obtained usingNOTE 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 Test Specimens (Steam Cores Not Shown)D3419 122compression-moldi
26、ng methods. Flexural tests are particularlysensitive to injection molding due to the thin resin skin formedat the surface of the bar during final filling of the cavity andpressure buildup.4.10 At constant mold temperature the following parametersare known to cause an underfilled condition at the ven
27、ted endof the cavity: incorrect plasticity, too low an injection pressure,insufficient material, too long an injection time, blocked vents,high stock temperature, or incorrect die temperature.5. Apparatus5.1 In-Line, Screw-Injection Machine A device incorpo-rating a hydraulically or electrically dri
28、ven screw which,working against a predetermined back pressure, draws materialfrom the feed hopper and by frictional and conducted heatworks a charge of material into a hot plastic state. Followingthe plasticating step, the screw stops rotating, moves forwardand forces the hot material through the no
29、zzle, sprue, runner,and gate into the cavity. Optimal injection and clamp pressuresare within the range of 70 to 140 MPa (10,000 to 20,000 psi).Measurement of actual molding pressures can be made withpressure transducers placed strategically in the cavities.5.1.1 The clamp force of the machine shall
30、 be sufficient toprevent excessive flashing under all operating conditions (see5.2.5).5.2 MoldThe mold cavities and layout depend on thespecimens required by the tests in question. The mold layoutshown in Fig. 1 has been found satisfactory, although moldswith fewer cavities, or different configurati
31、ons, or both can beused. Molds with multiple-identical-cavity layouts with sym-metrical gates and runners are recommended. Single cavitymolds are not recommended. In any case, it is important todescribe the mold in the report on the specimen preparation.5.2.1 Family molds like the one shown in Fig.
32、1 requireproper precautions to ensure that constant and uniform filling isachieved in all cavities.5.2.2 Gate dimensions equal to two-thirds of the width andheight of end-gated specimens are recommended for specimensnot greater than 4-mm (0.16-in.) thickness. For specimens over4-mm (0.16-in.) thickn
33、ess, or for other than end-gated speci-mens, gate dimensions of 8-mm (0.31-in.) width by 3-mm(0.12-in.) thickness are recommended. Short gate lengths, notexceeding 3 mm (0.12 in.) are recommended.5.2.3 Suitable venting must be provided from each cavity.Dimensions of 4 to 6-mm (0.16 to 0.24-in.) widt
34、h by 0.05 to1-mm (0.002 to 0.004-in.) depth are recommended.5.2.4 It is recommended that cavities be landed, so that ifflashing does occur, the mold will re-close after the injectionstroke. Typical lands are 4.5 mm (316 in.) to 6 mm (14 in.) inwidth. Landing pads are recommended to hold the mold ope
35、n0.0125 mm (0.0005 in.) in order to prevent damage to thelands.5.2.5 Full round runners, at least 6-mm (0.24-in.) diameter,are recommended as they offer less resistance to flow.5.2.6 Sharp corners in gates and runners are to be avoided asthey can cause hot spots and premature curing.5.2.7 On larger
36、specimens, such as discs or plaques, mul-tiple gates can produce knit lines where the material flowstogether. One larger gate is generally better than severalsmaller gates.5.2.8 Mold surfaces finished to a roughness of 0.4 to 0.8 m(SPI-SPE #2 or equivalent4) are preferred, unless it is knownthat the
37、 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 of flow willfacilitate specimen removal.5.2.9 Hydraulic or mechanical knockout systems outside ofthe specimen test area can be used, if
38、necessary, to ensure partremoval.5.2.10 For specimens no greater than 4-mm (0.16-in.) thick-ness, a maximum cavity draft angle of 1 is preferred. Forthicker specimens or, if necessary, to provide additional re-lease, a maximum cavity draft angle of 2 can be used.5.2.11 It is recommended that all mol
39、d cavities be marked toidentify the source of specimens. Such identifying marks shallnot be located in the test area of the specimens.5.2.12 Interchangeable mold cavities and gate inserts arerecommended to achieve the greatest flexibility in molding.5.3 Heating SystemMold heating can be accomplished
40、 byconduction from heated platens, heaters inserted into the molditself by hot fluids circulated through passageways in the moldor any suitable alternative. The heating system used shall becapable of controlling the mold temperature to 63C (65F)from point to point on the mold and for the duration of
41、 themolding time.NOTE 3It is generally preferable to heat the mold electrically.5.4 Temperature IndicatorA surface pyrometer or equiva-lent means is used to measure the temperature of the moldsurface.6. Conditioning6.1 Store the molding compound in moisture barrier con-tainers and keep at standard r
42、oom temperature at the time ofmolding. Compounds designed for screw-injection moldingordinarily are not preconditioned prior to molding. Mold thematerial as soon as possible after opening the container.7. Procedure7.1 Choose and set the temperatures of the mold based onthe relevant material specific
43、ation, the manufacturers recom-mendation, or previous experience with the particular type ofmaterial being used and its plasticity.NOTE 4Typically, the temperature will be in the range from 150 to175C (302 to 347F).7.2 Set barrel temperatures, back pressure, and screw speedto give a stock temperatur
44、e between 90 and 120C (195 to250F). The optimum molding conditions and stock tempera-ture to be used for a particular compound are those which give4The sole source of supply of mold comparison kits known to the committee atthis time is D-M-E Co., 29111 Stephenson Highway, Madison Heights, MI 48071.I
45、f you are aware of alternative suppliers, please provide this information to ASTMInternational Headquarters. Your comments will receive careful consideration at ameeting of the responsible technical committee,1which you may attend.D3419 123consistent processing from one shot to the next and which yi
46、eldtest specimens that are completely filled out and free of anymolded-in defects. Eliminate any unwanted cavity by blockingits runner system at the gate and adjusting injection pressureand shot size accordingly.7.2.1 The stock temperature (the temperature of the materialafter the plasticating step)
47、 is determined by injecting a slug ofmaterial out of the nozzle into an insulated cup and immedi-ately measuring the temperature with a needle-type pyrometeror equivalent means.7.3 The injection pressure selected is dependent upon thecomposition and plasticity of the material.NOTE 5A secondary or ho
48、lding pressure of 50 % of the primaryinjection pressure is recommended. A secondary pressure lower than 30MPa (4300 psi) is not recommended.7.4 The various molding parameters, including injectionpressure and/or speed, shall be adjusted to achieve a suitableinjection time.NOTE 6Depending upon the num
49、ber of cavities in the mold, aninjection time of 4 to9sisrecommended.7.5 A suitable cure time shall be used to give a blister-freepart.NOTE 7A cure time of 10 s beyond the blister-free cure time of thethickest specimen is normally sufficient.8. Report8.1 Report the following information:8.1.1 Type and description of material used,8.1.2 Identification of mold, as follows:8.1.2.1 Specimen geometry8.1.2.2 Mold layout, and8.1.3 Molding conditions, as follows:8.1.3.1 Mold temperature,8.1.3.2 Stock temperature,8.1.3.3 Injection pressure,8.1.3.4 Inj
