1、Designation: D3641 14D3641 15Standard Practice forInjection Molding Test Specimens of Thermoplastic Moldingand Extrusion Materials1This standard is issued under the fixed designation D3641; the number immediately following the designation indicates the year oforiginal adoption or, in the case of rev
2、ision, the year 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 followed when injection molding test specimens o
3、f thermoplastic moldingand extrusion materials. This practice is to be used to obtain uniformity in methods of describing the various steps of the injectionmolding process and to set up uniform methods of reporting these conditions. The exact conditions required to prepare suitablespecimens will var
4、y for each plastic material. Any requirements or recommendations in the material specification that differ fromthis standard take precedence over those in this standard. Always consult the referenced material document for specimenpreparation. If no referenced document exists, then consult the materi
5、al supplier for specimen preparation guidance and note suchin the test report.1.2 The methodology presented assumes the use of reciprocating screw injection molding machines.1.3 The values stated in SI units are to be regarded as the standard. The values given in parentheses are for information only
6、.1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibilityof the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatorylimitations prior to use.NOTE 1This pract
7、ice is equivalent to the following parts of ISO 294: PlasticsInjection Moulding of Test Specimens of Thermoplastic Materials;294-1: Part 1General Principles and Multipurpose Test Specimens (ISO Type A Mould) and Bars (ISO Type B Mould); ISO 294-2: Part 2SmallTensile Bars (ISO Type C Mould); ISO 294-
8、3: Part 3Plates (ISO Type D Moulds).2. Referenced Documents2.1 ASTM Standards:2D256 Test Methods for Determining the Izod Pendulum Impact Resistance of PlasticsD570 Test Method for Water Absorption of PlasticsD638 Test Method for Tensile Properties of PlasticsD648 Test Method for Deflection Temperat
9、ure of Plastics Under Flexural Load in the Edgewise PositionD790 Test Methods for Flexural Properties of Unreinforced and Reinforced Plastics and Electrical Insulating MaterialsD883 Terminology Relating to PlasticsD955 Test Method of Measuring Shrinkage from Mold Dimensions of ThermoplasticsD957 Pra
10、ctice for Determining Surface Temperature of Molds for PlasticsD1525 Test Method for Vicat Softening Temperature of PlasticsD6110 Test Method for Determining the Charpy Impact Resistance of Notched Specimens of Plastics2.2 ISO Standards:3ISO 3167 PlasticsPreparation and Use of Multipurpose Test Spec
11、imensISO 294-1: PlasticsInjection Moulding of Test Specimens of Thermoplastic MaterialsPart 1: General Principles andMultipurpose Test Specimens (ISO Type A Mould) and Bars (ISO Type B Mould)ISO 294-2: PlasticsInjection Moulding of Test Specimens of Thermoplastic MaterialsPart 2: Small Tensile Bars
12、(ISO TypeC Mould)ISO 294-3: PlasticsInjection Moulding of Test Specimens of Thermoplastic MaterialsPart 3: Plates (ISO Type D Moulds)1 This practice is under the jurisdiction of ASTM Committee D20 on Plastics and is the direct responsibility of Subcommittee D20.09 on Specimen Preparation.Current edi
13、tion approved March 1, 2014May 1, 2015. Published March 2014June 2015. Originally approved 1991. Last previous edition approved 20122014 asD3641 12.D3641 14. DOI: 10.1520/D3641-14.10.1520/D3641-15.2 For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Customer Service at
14、 serviceastm.org. For Annual Book of ASTM Standardsvolume information, refer to the standards Document Summary page on the ASTM website.3 Available from American National Standards Institute (ANSI), 25 W. 43rd St., 4th Floor, New York, NY 10036, http:/www.ansi.org.This document is not an ASTM standa
15、rd and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Becauseit may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases
16、only the current versionof the standard as published by ASTM is to be considered the official document.*A Summary of Changes section appears at the end of this standardCopyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States1ISO 20753 Plastics
17、Test Specimens3. Terminology3.1 DefinitionsDefinitions of terms applying to this practice appear in Terminology D883.3.2 Definitions of Terms Specific to This Standard:3.2.1 average injection velocity, nthe mean value of the velocity of the molten plastic flow front within a cavity during theinjecti
18、on time that is calculated from the shot volume and injection time. (See Terminology D883.)3.2.1.1 DiscussionThe average injection velocity is calculated as follows:Vav 5 VsTi 3Ac 3nwhere:Vav = average injection velocity, mm/s,Vs = shot volume, mm3,Ti = injection time, s,Ac = cross section of the ca
19、vity, mm2, (see 3.2.2) andn = number of cavities.The calculation is valid for molds containing a single cavity or those containing identical multi-specimen cavities only. Thiscalculation does not apply for family molds.3.2.2 cross section of the cavity, nin a mold for test specimens, the area of a p
20、lanar section perpendicular to the flow patternduring filling of the mold that forms the critical portion of the test specimen.3.2.3 flash, nthin film of material formed at the parting line of a part during molding, caused by unintentional opening of themold or by defective mating surfaces.3.2.4 swi
21、tchover point, nthat point in the injection stage of the injection molding cycle when the control or level of theforwarding force applied to the screw and shot is switched from that used during injection to that used during pack/hold.3.2.5 velocity-pressure transfer point (VPT), nthat point in the i
22、njection stage of the injection molding cycle as defined bypressure, position, or time when the rate of ram travel is switched from speed control to pressure control.4. Summary of Practice4.1 Many factors in the injection molding process can have an influence on the character of the moldings and the
23、 numericalvalues of test results. Among these are geometry, size, and temperature conditions of the heating chamber, pressures and speedsused, size, shape, and length of runners and gates, mold temperature and its uniformity, cavity surface finish, and timing cyclesused along with the method of sequ
24、encing from stage to stage in the process. It is sometimes necessary to pretreat materials beforemolding. For materials that absorb water, drying under prescribed conditions is recommended and the user is advised to consultthe applicable material standard for the conditions. This practice attempts t
25、o control some of these variables, nullify others, andreport those that are necessary to obtain reproducible specimens. Definite stock and mold temperatures, based on the relevantmaterial specifications or the material suppliers recommendations or past experience, and measured by standard techniques
26、, areused for the molding process. By a sequence of operations the pressures, timing settings, and mode of control are established onthe basis of their effects upon the molded part itself rather than upon any universal setpoints.5. Significance and Use5.1 It is well known that plastic test specimens
27、 molded under different conditions can have significantly different properties.This practice is designed to minimize those differences by establishing operating protocols without being unnecessarily restrictive.5.2 Always refer to theASTM material specification or ISO designation for the material fo
28、r recommended molding conditions.If not available, consult the material supplier.5.3 This practice requires the use of adequate quantities of plastic material to find desirable operating conditions and to makethe desired test specimens.6. Apparatus6.1 Injection Molding MachineThe machine selected fo
29、r use must be equipped with appropriate devices for the control andmeasurement of pressures, all relevant temperatures, and the timing of certain cycle elements.Additional devices to monitor cavitypressure and ram position and velocity are very useful and desirable in the effective control of the in
30、jection molding process toD3641 152give reproducible results. The capacity of the machine shall be such that the total shot weight (specimens plus sprue and runners)is 20 to 80 % of rated capacity. The injection machine must be capable of maintaining the proper injection velocity range ifspecified i
31、n the material standard.NOTE 2Heat-sensitive materials may require using the high end of the machine shot capacity range in order to minimize residence time of the meltin the barrel.6.1.1 Control SystemThe various control systems shall maintain the operating parameters of the injection molding proce
32、ssfrom cycle to cycle within the following limits:plastic melt, or stock temperature 3Cmold temperature 3C, #80C5C, 80Cinjection pressure 2 %hold pressure 5 %injection time 0.1 shold time 5 %shot weight 2 %Suitable means of monitoring these parameters to ensure control within the above limits shall
33、be utilized.6.1.2 ScrewThe design of the screw will be determined by the material being molded. A key criterion of screw design is toprovide a melt that is as uniform as possible with respect to composition, temperature, and viscosity.6.1.3 ClampThe clamping force of the machine shall be high enough
34、 to prevent flashing at all operating conditions.NOTE 3The minimum clamp force required is the product of the highest possible cavity pressure and the projected surface area of the cavities (andrunners). A force greater than this minimum will be required to prevent flashing.6.2 MoldThe design of the
35、 mold is one of the more critical variables affecting specimen properties. Optimum reproducibilityrequires that identical molds be used by parties attempting to obtain comparable results. However, in the absence of identicalmolds, adherence to certain features of design will help to minimize differe
36、nces between results obtained by different parties. Ithas been found that the use of unitized mold bases with interchangeable mold plates and gate inserts can provide a great deal offlexibility and provide rapid transitions between the moldings of different specimen configurations. (See Annex A1.)6.
37、2.1 Cavity LayoutMulti-cavity molds with identical cavities are recommended. The cavity layout shall be such that thereis a uniform and symmetrical distribution of specimen surface area on the overall mold surface. The use of single cavity moldsis discouraged. For large tensile test specimens and mu
38、ltipurpose bars, a two cavity “Z” layout is preferred, but a “T” layout isacceptable. For small tensile test specimens and bars, a four cavity double “T” layout is recommended. Other specimens have theirunique cavity layout. (See Annex A1.)NOTE 4ISO 294-1 states that the “Z” cavity runner layout is
39、preferred over the “T” cavity runner layout.NOTE 5Family molds designed to produce more than one part configuration with each shot are not recommended. If molds of this nature are used,consideration shall be taken in the design to ensure that constant and uniform filling velocities are achieved in a
40、ll cavities. Empirical techniques can beused to estimate these velocities. Additionally it is cautioned that the comparability of data obtained on specimens molded in this manner may be limitednot only to a specific polymer type but also to specific rheological characteristics.6.2.2 RunnersRunners w
41、ill either be of the full-round type cut into both halves of the mold or of the trapezoidal type cut intoonly one of the mold halves. They shall be a minimum of 5 mm (0.2 in.) in diameter or of equivalent cross-sectional area iftrapezoidal.Asymmetrical cavity layout will permit identical runner syst
42、ems to be used for each cavity and thus facilitate uniformfilling of all cavities with all materials under all conditions. Runner draft angles for trapezoidal runners shall be from 10 to 30.The diameter of the sprue shall be a minimum of 4 mm on the nozzle side.NOTE 6The runner system for small bars
43、 is longer than conventional to allow for approximately the same total shot volume between the differentinterchangeable cavity plates so that the shot size does not have to be adjusted significantly.NOTE 7If family molds with two or more identical specimen cavities or non-identical runner systems or
44、 if multi-cavity molds with non-identicalrunner systems are used, specimens from such cavities shall be identified and not be commingled for testing unless it has been demonstrated that thereare no statistically significant differences in test results between the cavities.NOTE 8Limited data have sho
45、wn that, for some materials (Polypropylenes, in particular), mechanical test values can be significantly affected by thecross sectional area of the runner. Specimens molded using the specified minimum runner size of 5 mm D (20 mm2) exhibited lower values of mostmechanical properties than specimens m
46、olded using runners with cross-sectional areas of 50 and 80 mm2. Higher viscosity (lower MFR) materials appearto be more sensitive. This effect needs to be considered when comparing data obtained from different sources.6.2.3 GatesUnless otherwise stated for specific specimens, or material specificat
47、ions, the gate depth for bar-type specimensshall be at least two-thirds the depth of the bar-type cavities cavity and the gate width shall preferably be equal to be at least twothirds the width of the bar-type cavities but no less than two thirds the width. cavity. Use the shortest possible gate len
48、gth, witha maximum length of 3 mm (0.12 in.). Such large gates tend to give parts whose physical properties are less sensitive to varyingmolding conditions than smaller ones. However, many existing test methods call for somewhat smaller gates such as some of thoselisted in Table 1.NOTE 9Larger gates
49、 (width and depth) are preferred as they tend to produce parts whose physical properties are less sensitive to varying moldingconditions than smaller ones.NOTE 10Certain materials require smaller gates to promote shear thinning so that mold cavities will be filled.D3641 153Gate sizes for commonly used test specimens are listed in Table 1. If it is necessary to use gates with alternative dimensions,these shall be reported in accordance with 8.1.6.6.2.4 CavitiesMachining tolerances of the cavity will depend on the material t
