ASTM D1896 D1896M-2010 Standard Practice for Transfer Molding Test Specimens of Thermosetting Compounds《热固化合物的传递模塑试样的标准实施规程》.pdf
《ASTM D1896 D1896M-2010 Standard Practice for Transfer Molding Test Specimens of Thermosetting Compounds《热固化合物的传递模塑试样的标准实施规程》.pdf》由会员分享,可在线阅读,更多相关《ASTM D1896 D1896M-2010 Standard Practice for Transfer Molding Test Specimens of Thermosetting Compounds《热固化合物的传递模塑试样的标准实施规程》.pdf(4页珍藏版)》请在麦多课文档分享上搜索。
1、Designation: D1896/D1896M 10Standard Practice forTransfer Molding Test Specimens of ThermosettingCompounds1This standard is issued under the fixed designation D1896/D1896M; the number immediately following the designation indicates theyear of original adoption or, in the case of revision, the year o
2、f last revision. A number in parentheses indicates the year of lastreapproval. A superscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope*1.1 This practice covers a general procedure for the transfermolding of mechanical and electrical test specimens of the
3、r-mosetting molding materials.NOTE 1The utility of this practice has been demonstrated for themolding of thermosetting molding compounds exhibiting intermediateviscosity non-Newtonian flow.1.2 The values stated in either SI or inch-pound units are tobe regarded separately as standard. The values sta
4、ted in eachsystem are not always exact equivalents; therefore, eachsystem shall be used independently of the other. Combiningvalues from the two systems can result in nonconformancewith this practice.1.3 This standard does not purport to address all of thesafety concerns, if any, associated with its
5、 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 limitations prior to use.NOTE 2There is no known ISO equivalent to this standard.2. Referenced Documents2.1 ASTM Standards:2D883 Terminology
6、 Relating to PlasticsD957 Practice for Determining Surface Temperature ofMolds for PlasticsD3123 Test Method for Spiral Flow of Low-Pressure Ther-mosetting Molding CompoundsD3795 Test Method for Thermal Flow, Cure, and BehaviorProperties of Pourable Thermosetting Materials by TorqueRheometer3. Termi
7、nology3.1 Definitions:3.1.1 GeneralDefinitions of terms applying to this prac-tice appear in Terminology D883.3.1.2 transfer molding, na method of forming articles byfusing a plastic material in a chamber and then forcingessentially the whole mass into a hot mold where it solidifies.3.2 Definitions
8、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.3.2.1.1 DiscussionBreathing allows the escape of gas orvapor from the molding material and reduces the tendency ofthick moldings to bli
9、ster.3.2.2 cavity (of a mold), nthe space within a mold to befilled to form the molded product.3.2.3 clamp pressure, nthe pressure applied to the mold tokeep it closed, in opposition to the fluid pressure of thecompressed molding material.3.2.4 fill time, nthe time required to fill each cavity usedi
10、n the mold. Fill times can be critical to well molded parts (seeNote 3 under 4.4).3.2.5 minimum plunger pressure, nthe minimum pressure,on the ram, required to just fill each cavity used in the mold ata specified temperature and reasonable fill time.3.2.6 vent, na hole, slot, or groove provided in a
11、 mold ormachine to allow air and gas to escape during molding,extrusion, or forming.4. Significance and Use4.1 Transfer molding is particularly suited to thermosettingmaterials of intermediate plasticity. Fixed molding parameterscannot be specified for each type of material. Molding com-pounds of th
12、e same type come in many different plasticitiesmeasured in accordance with Test Methods D3123 and D3795.Consequently, for a given material type, the molding param-eters required to produce satisfactory test specimens will oftenvary dependent on the plasticity of the specific material grade.4.2 The m
13、old shown in this practice provides for a set offive specimens. However, if only certain specimens are desired,the other cavities can be blocked by inserting gate blanks.4.3 Typically, breathing of the mold is not required torelease trapped volatile matter as the gas is free to flow fromthe vent end
14、 of the mold. This is a particular advantage for1This practice is under the jurisdiction ofASTM Committee D20 on Plastics andis the direct responsibility of Subcommittee D20.09 on Specimen Preparation.Current edition approved Aug. 1, 2010. Published September 2010. Originallyapproved in 1961. Last p
15、revious edition approved in 2009 as D1896 - 09. DOI:10.1520/D1896_D1896M-10.2For 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 onth
16、e ASTM website.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.heat-resistant compounds and reduces the tendency for moldedspecimens to blister at high exposure temper
17、atures.4.4 Flow and knit lines in a molded piece are often sites ofmechanical or electrical weakness and can be found in somedegree of severity throughout the molded piece. The semisolidmolding compound passing through the gate is subject tonon-Newtonian flow and, consequently, wrinkles and folds as
18、it travels down the mold cavity. Fibers and other reinforce-ments in the molding compound align with the flow patternand, consequently, can orient perpendicular to the axis of thebar at the center and parallel at the surface of the bar. Moldtemperature, thermal conductivity and plasticity of the mol
19、dingcompound, degree of preheat, and plunger pressure are param-eters that influence the time to fill the mold cavities and theformation of knit lines.NOTE 3If the temperature of the mold is held constant and the plungerpressure varied for a designated thermosetting molding compound, twoextreme char
20、acteristic conditions can be obtained. If the pressure is low,then the vent end of the cavity will not fully fill, and weld lines will formby incomplete knitting of the material. If the pressure is too high, the moldcavity will fill fast, the outside of the specimen will case harden while thepressur
21、e is still forcing material out the vent, and a ball-and-socket grainstructure will be obtained. A ball-and-socket structure is an indication ofthe molding condition, and lower test data will result.4.5 Thermosetting compounds containing long-fiber fillerssuch as glass roving, chopped cloth, or shav
22、ings can be usedbut are not recommended for transfer molding. These fillermaterials tend to break, tear, or ball in passing through thegates of the mold, thereby not optimizing their potentialstrength.4.6 The Izod impact strength of transfer molded specimensof molding compounds containing short fibe
23、rs will generally belower than the values obtained using compression-moldingmethods. Quite often the impact strength will vary along theaxis of the bar due to molding parameters, flow pattern, andfiber orientation.4.7 The flexural and tensile strength of transfer moldedspecimens of molding compounds
24、 containing short fibers willgenerally be higher than the values obtained usingcompression-molding methods. Flexural tests are particularlysensitive to transfer molding due to the thin resin skin formedat the surface of the bar during the final filling of the cavity andpressure buildup.5. Apparatus5
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