ASTM_D_1896_-_D_1896M_-_10.pdf

Designation:D1896/D1896M10Standard 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 of 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 ther-mosetting molding materials.NOTE1The 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 stated 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 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.NOTE2There is no known ISO equivalent to this standard.2.Referenced Documents2.1 ASTM Standards:2D883 Terminology 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.Terminology3.1 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 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 blister.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 used inthe 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 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 the 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 mold 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.1This 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 previous 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 onthe ASTM website.*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 States1 4.3 Typically,breathing of the mold is not required torelease trapped volatile matter as the gas is free to flow fromthe vent end of the mold.This is a particular advantage forheat-resistant compounds and reduces the tendency for moldedspecimens to blister at high exposure temperatures.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,con