1、Designation: D731 10D731 18Standard Test Method forMolding Index of Thermosetting Molding Powder1This standard is issued under the fixed designation D731; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A
2、 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 test method covers the measurement of the molding index (plasticity) of thermosetting plastics ranging in flow fromsoft to stiff
3、 by selection of appropriate molding pressures within the range from 3.7 to 36.5 MPa (530 to 5300 psi).1.2 The values stated in SI units are to be regarded as the standard. The values given in parentheses are for information only.1.3 This standard does not purport to address all of the safety concer
4、ns, if any, associated with its use. It is the responsibilityof the user of this standard to establish appropriate safety safety, health, and healthenvironmental practices and determine theapplicability of regulatory limitations prior to use.NOTE 1There is no known ISO equivalent to this test method
5、.1.4 This international standard was developed in accordance with internationally recognized principles on standardizationestablished in the Decision on Principles for the Development of International Standards, Guides and Recommendations issuedby the World Trade Organization Technical Barriers to T
6、rade (TBT) Committee.2. Referenced Documents2.1 ASTM Standards:2D256 Test Methods for Determining the Izod Pendulum Impact Resistance of PlasticsD883 Terminology Relating to PlasticsD957 Practice for Determining Surface Temperature of Molds for PlasticsE691 Practice for Conducting an Interlaboratory
7、 Study to Determine the Precision of a Test Method3. Terminology3.1 Definitions are in accordance with Terminology D883, unless otherwise specified.3.2 Definitions of Terms Specific to This Standard:3.3 plasticitya measure of the resistance of a molten thermosetting material to flow under heat and p
8、ressure.Ameasure of theapparent viscosity of the material.4. Summary of Test Method4.1 A cup mold is mounted in a semi-automatic type press. A predetermined quantity of test sample is charged into the mold,controlled at a temperature dependent upon the test material. The minimum force required to mo
9、ld a cup having a flash or finthickness within a specified tolerance is determined. This force along with the mold closing time is reported as molding index.5. Significance and Use5.1 This test method provides a guide for evaluating the moldability of thermosetting molding powders. This test method
10、doesnot necessarily denote that the molding behavior of different materials will be alike and trials may be necessary to establish theappropriate molding index for each material in question.1 This test method is under the jurisdiction ofASTM Committee D20 on Plastics and is the direct responsibility
11、 of Subcommittee D20.30Thermal Properties.30 on ThermalProperties (Section D20.30.08).Current edition approved May 1, 2010May 1, 2018. Published June 2010May 2018. Originally approved in 1950. Last previous edition approved in 20082010 asD731 - 08.D731 - 10. DOI: 10.1520/D0731-10.10.1520/D0731-18.2
12、For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Customer Service at serviceastm.org. For Annual Book of ASTM Standardsvolume information, refer to the standards Document Summary page on the ASTM website.This document is not an ASTM standard and is intended only to p
13、rovide 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 only the current versionof t
14、he 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 States15.2 The sensitivity of this test diminishes wh
15、en the molding pressure is decreased below 5.3 MPa (764 psi), so pressures lowerthan this are not ordinarily recommended. This is due to the friction of moving parts and the insensitivity of the pressure switchactuating the timer at these low pressures.6. Apparatus6.1 MoldA cup mold3 of the flash ty
16、pe, to produce a molded cup as shown in Fig. 1, operated under controlled pressure andtemperatures and provided with stops so that flash or fin thickness cannot be less than 0.14 mm (0.0055 in.). The area of the moldcasting creating the molded flash shall be located on top of the cup, flat, perpendi
17、cular to the axis of the cup, and in the form ofan annular ring 3.17 mm (0.125 in.) in width.6.2 PyrometerA calibrated pyrometer, traceable to a national standard (for example, NIST), and accurate to 61C shall beused to determine the temperature of the mold surfaces. For properly measuring mold temp
18、eratures, reference Practice D957.6.3 Heating SystemAny conventional means for heating the press platens, provided the heat source is constant enough tomaintain the molding temperature within 61C of the specified temperature (see 9.2).3 A detailed drawing of the mold design is available from ASTM He
19、adquarters. Order Adjunct: ADJD0731.FIG. 1 Cup MoldD731 1826.4 Pressure SystemA semiautomatic press with a fixed mold and fully insulated to minimize heat losses shall be used. Thehydraulic system shall be provided with a means of pressure regulation so that the load on the mold shall differ by not
20、more than61112 N (6250 lbf) from the stated value. The capacity of the hydraulic system shall permit a ram travel of approximately 25mm/s (1 in./s). The ram diameter shall not exceed 100 mm (4 in.).NOTE 1The use of hand molds is not recommended but may be used to give an estimate of the molding inde
21、x.7. Test Specimen7.1 To determine the weight of the test specimen for materials having an Izod impact strength of 27 J/m (0.50 ft-lb/in.) of notch,or less, a cup having a flash or fin thickness of 0.15 to 0.20 mm (0.006 to 0.008 in.) shall be molded (see Note 32). The adheringfin shall be removed a
22、nd the cup weighed to the nearest 0.1 g. This weight multiplied by 1.1 shall be the weight of the test specimenused. For materials having an impact above 27 J/m (0.50 ft-lb/in.) of notch, the specimen weight is determined in a similar manner,except that cup flash shall not be more than 0.66 mm (0.02
23、6 in.) or less than 0.51 mm (0.020 in.), and the amount of material shallbe 1.05 times the weight of this cup. The test specimen shall be in the form of loose powder unless preforming is necessary formaterials of high bulk. Minimum pressure shall be employed in the preforming operation to minimize t
24、he increase in closing timeresulting from the use of preforms.NOTE 2While the mold is provided with stops so that the flash or fin thickness cannot be less than 0.15 6 0.013 mm (0.006 6 0.0005 in.), the moldedcup itself may have a flash thickness of 0.15 to 0.20 mm (0.006 6 0.0008 in.) as the micro
25、switch controlling the closing time must have a tolerancein which to operate.8. Conditioning8.1 Materials are normally tested in the “as received” condition, except in referee tests, when they shall be conditioned inaccordance with 8.2 (see Note 43).8.2 For referee testing, all materials shall be sh
26、ipped and stored in sealed moisture barrier containers. These materials shall bestored for a minimum period of 48 h at standard laboratory temperature before breaking the seal on the carton. A representativesample shall be taken from this carton immediately after opening and tested within 3 min in o
27、rder to preserve the original moisturecontent. Alternative methods of conditioning samples are acceptable provided they are mutually agreed upon between themanufacturer and the purchaser.NOTE 3Conditioning may alter the moisture content of most materials and thereby change their molding index or mol
28、ding behavior.9. Procedure9.1 Mount the mold in the semi-automatic press. The rate of flow is sensitive to the condition of the mold surfaces. To avoiderroneous results, any residue deposited from prior tests shall be completely removed from the mold surfaces. Discard the first fewcups molded and ac
29、cept the flow time as correct when two successive cups molded under test do not differ by more than 1 s intime of flow.9.2 The preferred mold temperature for testing the molding index for the following materials shall be:C (F)Phenolic 165 1 (330 1.8)Melamine 155 1 (310 1.8)Urea 150 1 (300 1.8)Epoxy
30、150 1 (300 1.8)Diallyl phthalate 150 1 (300 1.8)Alkyd 150 1 (300 1.8)Other temperatures are acceptable provided they are mutually agreed upon between the manufacturer and the purchaser.9.3 First determine the proper weight to be used as outlined in 6.1. Then begin the test with a load sufficient to
31、close the moldto the fin thickness specified for the type of material being tested as defined in 6.1. For example, if a 44482 N (10,000 lb) loadis applied on the mold to make the initial cup and the required fin thickness is obtained, the next lower load, 336233362 N(37500(7500 lb) is applied as ind
32、icated in the following table. If the mold closes to the required thickness again, then the 22241N (5000 lb) load is applied. If the mold then does not close, the “molding index” is the closing time obtained with the 33362 N(7500 lb) load. It is recommended that the mold loads used be selected from
33、the following table (see Note 54):Total ForceBetweenPlatensPlasticPressureN (lb) MPa (psi)16 014 (3600) 5.3 (764)D731 18322 241 (5000) 7.3 (1060)33 362 (7500) 11 (1591)44 482 (10 000) 14.6 (2121)59 161 (13 300) 19.4 (2821)66 723 (15 000) 21.9 (3181)88 964 (20 000) 29.2 (4242)111 206(25 000) 36.5 (53
34、02)NOTE 4These fixed mold loads are recommended based upon common practice and materials and plasticities currently available. Other mold loadsmay be defined, if agreed to by supplier and customer, to better define the plasticity of a material.9.4 The time of flow in seconds shall be measured from t
35、he instant that the hydraulic gage indicates an applied load of 4448N (1000 lb) to the instant that the fin has reached 0.20 mm (0.008 in.) in thickness for materials with an Izod impact strength of27 J/m (0.50 ft-lb/in.) of notch, or less, and 0.66 mm (0.026 in.) for materials with an impact above
36、27 J/m (0.50 ft-lb/in.) of notch.NOTE 5The molding pressure is calculated by dividing the total load by the projected area of the mold cavity.NOTE 6A convenient method for determining fin thickness is to indicate the final movement of the platen with a dial micrometer.10. Report10.1 Report the follo
37、wing information:10.1.1 A statement indicating the nature of the material tested and the manufacturers material number and batch number,10.1.2 The molding index expressed as the total minimum force in newtons (pounds) required to close the mold, with the closingtime in seconds (for example, 445/13.4
38、 N (100/13.418),10.1.3 Temperature of the mold,10.1.4 Weight of the test sample in grams, and form of sample (loose powder or preform),10.1.5 Thickness of flash or fin measured to the nearest 0.025 mm (0.001 in.),10.1.6 Description of any unusual characteristics of the test sample, such as discolora
39、tion and sticking,10.1.7 Details of conditioning,10.1.8 Impact strength of the material expressed as Izod in J/m (ft-lb/in.) of notch in accordance with Test Methods D256, and11. Precision and Bias411.1 Table 1 is based on a round robin conducted in 1988 in accordance with Practice E691 involving te
40、n test samples. The testresults in Table 1 were from four laboratories with each laboratory obtaining four test results for each sample. (WarningThefollowing explanations of r and R (11.3 through 11.3.311.3.4) are only intended to present a meaningful way of considering theapproximate precision of t
41、his test method. The data in Table 1 is not to be rigorously applied to the acceptance or rejection ofmaterial, as those data are specific to the round robin and are not necessarily representative of other lots, conditions, materials, orlaboratories. In particular with data from less than six labora
42、tories, the between-laboratories results are likely to have a very highdegree of error.)11.2 Apply the principles outlined in Practice E691 to generate data specific to their laboratory and materials or between specificlaboratories. The principles of 11.3 through 11.3.311.3.4 would then be valid for
43、 such data.4 Supporting data are available from ASTM Headquarters. Request RR:D20-1163.TABLE 1 Molding Index in SecondsNOTE 1Sr is the within-laboratory standard deviation of the average,SR is the between-laboratories standard deviation of the average, r = 2.8Sr, and R = 2.8 SR.Material Average Load
44、, N(lb)Sr SR r RPolyester (B)A 4.78 112 (25) 0.025 0.909 0.070 2.545Glass-Filled (B)B 8.99 112 (25) 0.038 0.727 0.106 2.036Polyester (A)A 9.63 112 (25) 0.072 0.577 0.202 1.616Mineral Filled (A)B 11.54 112 (25) 0.072 0.881 0.202 2.467Mineral Filled (B)A 11.57 112 (25) 0.098 1.736 0.274 4.861General P
45、urpose (B)A 11.78 112 (25) 0.041 1.264 0.115 3.539DAP (B)A 12.64 112 (25) 0.054 0.892 0.151 2.498Impact Type (B)A 14.92 168 (36) 0.090 0.965 0.252 2.702Glass-filled (A)B 16.06 224 (50) 0.083 0.912 0.232 2.554General Purpose (A)B 18.37 168 (36) 0.056 1.331 0.157 3.727A Sample B obtained from Occident
46、al Chemical Corp., Fort Green, Ontario,Canada.B Sample A obtained from Occidental Chemical Corp., Tonawanda, NY.D731 18411.3 Concept of r and RR: If Sr and S R have been calculated from a large enough body of data, (use Table 1 with cautionas only four laboratories participated) and for test results
47、 that were averages from testing four specimens.11.3.1 Repeatability (Sr)Precision under repeatability conditions, represented by repeatability standard deviation.11.3.2 Reproducibility (SR)Precision under reproducibility conditions, represented by reproducibility standard deviation.11.3.3 Repeatabi
48、lity Limit, rComparing two test results for the same material, obtained by the same operator using the sameequipment on the same day, the two test results shall be judged not equivalent if they differ by more than theThe value below whichthe absolute difference between two individual test results ob
49、tained under repeatability conditions may be expected to occur witha probability of approximately 0.95 (95 %).r value for that material.11.3.4 Reproducibility Limit, RComparing two test results for the same material, obtained by different operators usingdifferent equipment on different days, the two test results shall be judged not equivalent if they differ by more than the The valuebelow which the absolute difference between two individual test results obtained under reproducibility conditions may be expectedto occur with a probability
