1、Designation: D 3419 00 (Reapproved 2006)Standard Practice forIn-Line Screw-Injection Molding Test Specimens FromThermosetting Compounds1This standard is issued under the fixed designation D 3419; the number immediately following the designation indicates the year oforiginal adoption or, in the case
2、of revision, the 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. Scope1.1 This practice covers the general principles to be fol-lowed when injection molding test spec
3、imens of thermosettingmaterials. 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 shouldbecome part of the material specificat
4、ion or be agreed uponbetween the purchaser and the supplier.NOTE 1The utility of this practice has been demonstrated for themolding of thermosetting molding compounds exhibiting lower-viscositynon-Newtonian flow.1.2 The values stated in SI units are to be regarded asstandard. The values given in bra
5、ckets are for information only.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-priate safety and health practices and determine the applica-bility of regulatory limitatio
6、ns prior to use.1.4 This practice assumes the use of reciprocating screwinjection molding machines.NOTE 2This standard is similar in content (but not technicallyequivalent) to ISO 10724: 1994(E).2. Referenced Documents2.1 ASTM Standards:2D 883 Terminology Relating to PlasticsD 958 Practice for Deter
7、mining Temperatures of StandardASTM Molds for Test Specimens of Plastics32.2 ISO Standards:4ISO 10724: 1994(E)PlasticsThermosetting MouldingMaterialsInjection Moulding of Multipurpose TestSpecimensISO 3167: 1993, PlasticsMultipurpose Test Specimens3. Terminology3.1 Definitions:3.1.1 GeneralDefinitio
8、ns of terms applying to this prac-tice appear in Terminology D 883.3.1.2 injection moldingthe process of forming a materialby forcing it, in a fluid state and under pressure, through arunner system (sprue, runner, and gate(s) into the cavity of aclosed mold.3.1.3 DiscussionScrew-injection molding an
9、d 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 early stage in the processof cure.3.2.2 DiscussionBreathing allows the escape of gas orvapor
10、from the molding material and reduces the tendency ofthick moldings to blister.3.2.3 cavity (of a mold), nthe space within a mold to befilled to form the molded product.3.2.4 landing (of a cavity), vthe practice of relieving themold around the cavity (cavities), thus reducing the surfacearea of the
11、flat mating surfaces of the mold halves. Typicallands are 4.5 mm 316 in. to 6 mm 14 in. in width. Landingpads should be incorporated to hold the mold open 0.0125 mm0.0005 in. to prevent damage to the lands.4. Significance and Use4.1 This practice is subject to the definition of injectionmolding give
12、n 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 ofa reciprocating screw and then is forced into a hot mold whereit solidifies. Hereafter, in-line screw-injection molding will bereferre
13、d 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. ISO1This practice is under the jurisdiction ofASTM Committee D20 on Plastics andis the direct respons
14、ibility of Subcommittee D20.09 on Specimen Preparation.Current edition approved March 15, 2006. Published March 2006. Originallyapproved in 1975. Last previous edition approved in 2000 as D 3419 - 00.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Servic
15、e at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3Withdrawn4Available from American National Standards Institute (ANSI), 25 W. 43rd St.,4th Floor, New York, NY 10036.1Copyright ASTM International, 100 Barr Harb
16、or Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.specimens and testing are gaining favor, however. ISO 10724describes the layout and practice for injection molding themulti-purpose specimens in accordance with ISO 3167.4.3 Typically, injection-molded test specimens are madewith
17、 shorter cycles than those used for similar moldings 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 particular
18、ly advantageous for heat-resistant compounds and 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 sam
19、ples of thesame material having different plasticities.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 a
20、nd as it passes through the system of runners and 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
21、 and folds as it proceeds into the moldcavity. Knit lines may be found to some degree throughout themolded piece; these knit lines affect end-test results. Fibers andother reinforcements in the molding compound align with theflow pattern and, consequently, may be perpendicular to theaxis of the bar
22、at its center and parallel at its surface.4.7.1 Placement and size of gates 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 i
23、mpact strength of injection-molded specimenscontaining short fibers will generally be lower than the valuesobtained using compression molding methods. The impactstrength may also vary along the axis of the bar due to moldingparameters, flow patterns, and fiber orientation.4.9 The flexural and tensil
24、e strength of injection-moldedspecimens of molding compounds containing short fibers willgenerally be higher than the values obtained usingcompression-molding methods. Flexural tests are particularlysensitive to injection molding due to the thin resin skin formedat the surface of the bar during fina
25、l filling of the cavity andpressure buildup.4.10 At constant mold temperature the following parametersmay cause an underfilled condition at the vented end of thecavity: incorrect plasticity, too low an injection pressure,insufficient material, too long an injection time, blocked vents,high stock tem
26、perature, or incorrect die temperature.5. Apparatus5.1 In-Line, Screw-Injection Machine A device incorpo-rating a hydraulically or electrically driven screw which,working against a predetermined back pressure, draws materialfrom the feed hopper and by frictional and conducted heatworks a charge of m
27、aterial into a hot plastic state. Followingthe plasticating step, the screw stops rotating, moves forwardand forces the hot material through the nozzle, sprue, runner,and gate into the cavity. The machine should be capable ofaccurately delivering and maintaining suitable injection andclamp pressures
28、 within the range from 70 to 140 MPa (10,000to 20,000 psi). Measurement of actual molding pressures canbe made with pressure transducers placed strategically in thecavities.5.1.1 The clamp force of the machine shall be sufficient toprevent excessive flashing under all operating conditions (see5.2.5)
29、.5.2 MoldThe mold cavities and layout will depend on thespecimens required by the tests in question. Fig. 1 has beenfound satisfactory, although molds with fewer cavities, ordifferent configurations, or both may be used. Molds withmultiple-identical-cavity layouts with symmetrical gates andrunners a
30、re normally recommended. Single cavity molds arenot recommended. In either case, it is important to describe themold in the report on the specimen preparation.5.2.1 Family molds like the one shown in Fig. 1 requireproper precautions to ensure that constant and uniform filling isachieved in all cavit
31、ies.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. thickness, or for other than end-gated speci-mens, gate dimensions of 8-mm 0.31-in. width by 3-mm0.12-in.
32、 thickness are recommended. The gates should be asshort as possible, not exceeding 3 mm 0.12 in. in length.5.2.3 Suitable venting must be provided from each cavity.Dimensions of 4 to 6-mm 0.16 to 0.24-in. width by 0.05 to1-mm 0.002 to 0.004-in. depth are recommended.5.2.4 It is recommended that cavi
33、ties 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 should be incorporated to hold the moldopen 0.0125 mm 0.0005 in. to prevent damage to the lands.5.2.5 Full round runners, at least 6-
34、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 specimens, such as discs or plaques, mul-tiple gates can produce knit lines where the material flowsto
35、gether. One larger gate is generally better than severalsmaller gates.5.2.8 Mold surfaces should be finished to a roughness of 0.4to 0.8 m (SPI-SPE #2 or equivalent5), unless it is known thatthe particular test is not affected by a coarser surface finish.Chrome plating is recommended but not necessa
36、ry. All cavitysurfaces should be draw polished to facilitate specimen re-moval.5.2.9 Hydraulic or mechanical knockout systems outside ofthe specimen test area may be used.5Mold comparison kits are available from the D-M-E Co., 29111 StephensonHighway, Madison Heights, MI 48071.D 3419 00 (2006)25.2.1
37、0 For specimens no greater than 4-mm 0.16-in. thick-ness, a maximum cavity draft angle of 1 should be used. Forthicker specimens a maximum cavity draft angle of 2 may beused.5.2.11 It is recommended that all mold cavities be marked toidentify the source of specimens. Such identifying marks shallnot
38、interfere with the testing of the specimens.5.2.12 Interchangeable mold cavities and gate inserts arerecommended to achieve the greatest flexibility in molding.5.3 Heating SystemThe molds may be heated by conduc-tion from heated platens, heaters inserted into the mold itself,or by hot fluids circula
39、ted through passageways in the mold.The heating system shall be capable of controlling the moldtemperature to 63C 65F from point to point on the moldand for the duration of the molding time.5.4 Temperature IndicatorTypically, a surface pyrometeris used to measure the temperature of the molded surfac
40、e asspecified in Practice D 958.6. Conditioning6.1 Store the molding compound in moisture barrier con-tainers and keep at standard room temperature at the time ofmolding. Compounds designed for screw-injection moldingordinarily are not preconditioned prior to molding. Mold thematerial as soon as pos
41、sible after opening the container.7. Procedure7.1 Choose and set the temperatures of the mold based onthe manufacturers recommendation, the relevant materialspecification, or previous experience with the particular type ofmaterial being used and its plasticity. Typically, the tempera-ture will be in
42、 the range from 150 to 175C 302 to 347F.7.2 Set barrel temperatures, back pressure, and screw speedto give a stock temperature between 90 and 120C 195 to250F. The optimum molding conditions and stock tempera-ture to be used for a particular compound are those which giveconsistent processing from one
43、 shot to the next and which yieldtest 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.NOTE 3It is generally preferable to heat the mold electric
44、ally.7.2.1 The stock temperature (the temperature of the materialafter the plasticating step) 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 pyrometer.7.3 The injection pressure selected is dependent
45、upon thecomposition and plasticity of the material. A secondary orholding pressure of 50 % of the primary injection pressure isrecommended. A secondary pressure lower than 30 MPa (4300psi) is not recommended.7.4 Depending upon the number of cavities in the mold, aninjection time of 4 to9sisrecommend
46、ed. The various moldingparameters, including injection pressure and/or speed, shall beadjusted to achieve this.7.5 Cure time must be sufficient to give a blister free part. Acure time of 10 s beyond the blister free cure time of thethickest specimen is normally sufficient.8. Report8.1 Report the fol
47、lowing information:8.1.1 Type and description of material used,8.1.2 Identification of mold, 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 Injection time,8.1.3.5 Clamp pressure, and8.1.3.6 Cycle time.9. Keywords9.1 in-li
48、ne screw-injection-molding; injection molding; testspecimens; thermosetting compoundsD 3419 00 (2006)3NOTE 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
49、Shown)ASTM International takes 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 responsibility.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.
