1、Designation:D 956-87._.:AMERICAN SOCIETY FOR TESTING AND MATERIALS.1916 Race SI.,Philadelphia,Pa.19103.If not listed in the current combined index.will appear in!he next edition.Reprinted from the Annual Book of ASTM Standards,Copyright ASTM 1-,.Standard Practice for COMPRESSION.MOLDING TEST SPECIME
2、NS OF AMINO-.MOLDING COMPOUNDS.i This standard is issued underthe fixed designation D956;the number immediately following the designation indicates the year of original adoption or.in the case of revision,the year of last revision.A number in parentheses indicates the year of last reapproval.A supei
3、script epsilon(e)indicates an editorial change since the last revision or reapproval.1.scope 1.I This practice covers procedures.for mold-ing test specimens of impact,flexure,tensile,and water absorption from urea-formaldehyde compounds and melamine-formaldehyde com-pounds.1.1.1 Cellulose-Filled Ure
4、a and Melamine.Materials:Impact test specimens,1 2.7 by 1 2.7 by 127 mm(I/2 by Y2 by 5 in.).Flexural test specimens,6.4 by 1 2.7 by 127 mm(Y.by Y2 by 5 in.)_-.Plastics2 Specimens of Plastic Molding Matenal?Moldd Elect-ical Insulating Materials3 D647 Practice for Design of Molds for Test D651 Test Me
5、thod for Tensile Strength of D 704 Specification for Melamine-Formal-D 705 Specification for Urea-Formaldehyde Molding Compounds2 D958 Practice for Determining Tempera-tures of Standard ASTM Molds for Test Specimens of Plastics.dehyde Molding Compounds Water-absorpiion skimens,5 1 by 3.2-mm 3.and us
6、e(2 by%-in.)disk.1.1.2 Shock-Resistant Melamine Materials:.mm(Y2 by 1/2 by 5 in.)mm(%by Y2 by 5 in.)3.1 The conditions under which samples are Impact test swimens,1 2.7 by 1 2.7 by 127 molded influence the PrOPeflia of the speci-mens.In determining whether a given compound flexural test specimens,6.
7、4 by I 2.7 by 127 meets the specification requirements,it is impor-*tant to hold to a standard set of conditions.This Tension test specimens,“dog-hne”is&O iKeSSiY for a valid COmpXkOn Of Prop ehes obtained with different Compounds,Or be-tween different batches O f the same compound.3.2 If the molded
8、 specimens show evidence of low density a r a due to trapped gaseSv the SpeC-hens should be discarded.A breathe step should be used in molding new specimens.It is critical to hold to a relatively brief breathe cycle to avoid Prmudng the granules before PressUre is ap Piid-That in poorly knitted area
9、s-and lower strength in the molded spimen-mens shown in Fig.2 ofASTM Method D 65 1,Test for Tensile Strength of Molded l e c t r i l Insulating Materials?1.2 The values stated in SI units are to be regarded as the standard.The values in parenthe-ses are given for information only.1.3 This srandard m
10、ay inmlve hazardous ma-terials,operations,and equipment.This standard does not purport to address all o f the safity prob-lems associated with its use.It is the responsibil-ity o f the user o f this standard to establish appro-priate safity and health practices and determine the applicability o f re
11、gulatory limitations prior to use.2.Referend Documents 2.1 ASTM Standards:D638 Test Method for Tensile Properties of.This piactice is under the jurisdiction of ASTM Committee D-20 on Plastics and is the dimt responsibility of Subcommittee D20.09 on Specimen Preparations.Current edition approved Sept
12、.25.1987.PuMished Novcm-ber 1987.Orgnally published a s D 956-48 T.Last pmiou edition D956-51(1981).*Annual Bodc of ASTM Sfandards,Vol 08.0 I.Annual Ed ofASTM Slandards.vol 1 0.0 1.-.NOTICE:This standard has either been superseded and replaced by a new version or discontinued.Contact ASTM Internatio
13、nal(www.astm.org)for the latest information.ASTM D9Cb 87 W 0759530 00L!0397 O-4.Apparatus 4.1 Molds(Nofe 1):4.1.1 For molding impact specimens of cellu-lose-filled urea and melamine materials,a single bar,single cavity positive mold such as that shown in the figure illustrating the Single Bar,Single
14、 Cavity Positive Mold in Practice D647 shall be used.4.1.2 For molding impact and flexure test specimens of shock-resistant urea and mela-mine materials,a single bar,single cavity positive mold such as that shown in the figure illustrating the Single Bar,Single Cavity Positive Mold in Practice D647
15、shall be used.4.1.3 For molding water absorption speci-mens of urea and melamine materials,amold such as the 51-mm(2-in.)positive mold shown in the figure illustrating the.Mo1d for Disk Test Specimens in Practice D 647 shall be used.4.i.4 For molding tension specimens,a single bar,single cavity.posi
16、tive._.mold such as that shown in the figure illustrating the Mold for Tension Test Specimens in Practice D 647 shall be used(Note 2).i.NOTE 1-The molds shown in Practice D647 are hand molds.For ease of molding they shall be made-D 956 semi-automatic by bolting them to the press platens:NOTE 2-Chrome plating of cavities is recom-mended,but not necessary.4.2 Press-A hydraulic press of suficient sen-sitivity so that the molding pressure on the spec-imen can be controlled to f 1.7 MPa(k250 psi).4.3