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Fiber structure development in high-speed melt spinning of poly(L-lactide)s with various D-lactide contents and racemate polylactide  
Fiber structure development in high-speed melt spinning of poly(L-lactide)s with various D-lactide contents and racemate polylactide
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关键词: poly(L-lactide)s  D-lactide  contents  and  racemate  polylactide  
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High-speedmeltspinningofpoly(L-lactides)(PLLA)copolymerizedwithasmallamountofD-lactidewascarriedout.Theorientation-inducedcrystallizationofPLLAwiththelowestD-lactidecontentstartedwhenthetake-upvelocityexceeded4km/min,andfiberswithα−formcrystalswereformed.ThecrystallizationinthespinningprocesswassuppressedwithanincreaseintheD-lactidecontent.Ontheotherhand,inthehigh-speedmeltspinningofracematepolylactide(r-PLA),α−formcrystalsandstereocomplex(SC)crystalswereformed,andtherelativeamountoftheSCcrystalsincreasedwithanincreaseinthetake-upveloctiy.Intheannealingprocessoftheas-spunr-PLAfibersobtainedat6km/min,reductionofthea-formcrystalsandsteepincreaseoftheSCcrystalsstartedataround100.C,whereasthea-fromcrystalswasfoundtoremainevenataround200.C.Asthemeltingtemperature(Tm)ofa-fromcrystalsisaround170.C,itcanbesaidthatthea-fromcrystalsstartedtodecreaseatatemperaturelowerthanitsTm,however,acertainamountofa-fromcrystalsremainedevenatatemperaturehigherthanitsTm.Amealingofas-spunanddrawnr-PLAfiberswascarriedoutat190oC,i.e.betweentheTmofα−formandSCcrystals.Birefringenceoftheas-spunfibersincreasedwhereasthatofthedrawnfibers,whichshowedhighbirefringenceafterdrawingat70oC,decreasedbytheannealingandeventuallybothfibersshowedsimilarbirefringence.
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mn-jkl    2009-05-25 16:52:02
文章研究了纺丝速率对结晶的影响以及在退火过程中a晶向stereocomplex晶的转化。
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