热熔粘合剂热稳定性及氧化降解机制研究.pdfVIP

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ThermalStabilizationofAdhesives

NealJ.EarhartandAmbuPatel

CIBA-GEIGYCorporation,Ardsley,NewYork,U.S.A.

GerritKnobloch

CIBA-GEIGYCorporation,Basel,Switzerland

I.INTRODUCTION

Adhesivesare,ingeneral,producedbythecompoundingofseveraldifferentcomponents:

polymers,tackifierresins,andwaxesoroils.Thehydrocarbon-basedcomponentsare

susceptibletothermaloxidationanddegradation[1].Manyadhesivesareexposedto

elevatedtemperaturesasaresultofcompounding,storage,andenduse.Hot-meltadhesives

(HMAs),forexampleareextremelypronetooxidationduetotheirhighcompoundingand

applicationtemperatures.Eachhydrocarbon-basedcomponentinanadhesiveformulation

followsasimilaroxidationmechanism.Theresultofdegradation,however,canbevery

differentandcangreatlyinfluencetheoverallthermalstabilityoftheadhesiveformulation.

II.MECHANISMOFTHERMALOXIDATIONANDDEGRADATION

ThebasicschemefortheautooxidationofpolymersisdetailedinTable1[2].Thescheme

canbebrokendownintoseveraldistinctreactions:initiation,propaion,andtermina-tion.

Thefirststepintheoxidationmechanism,initiation,occurswhenapolymericfreeradical

.

(R)isformedbyexposuretoheat,light,shear,orimpurities.Thepropaionreactions

involvetheveryrapidreactionofthepolymerfreeradicalswithoxygen-formingperoxy

radicals(ROO.).Theperoxyradicalscanthenreactwiththepolymertoproduce

hydroperoxides(ROOH),whichcandecomposefurthertoformtwonewfree-radical

..

species(ROandHO),which,inturn,canparticipateinotherpropa