The difference between transcrystallization and shear-induced cylindritic crystallization in fibre-reinforced polypropylene composites

摘要: Institut f(Jr Verbundwerkstoffe GmbH, Universit#t Kaiserslautern, Pf.3049, D-67663 Germany It was recognized early on that the fibre/matrix interphase (or interface) strongly influences mechanical properties of composite materials. One current research directions in field composites with semicrystalline thermoplastic ma- trices is devoted to question whether or not particular supermolecular arrangements trix vicinity reinforcing fibres can improve overall performance. Interest focused particularly potential benefits a transcrystalline [1-4], since it believed this kind "physical coupling" would enhance stress transfer between fibre and matrix. On effects interlayer, however, rather contradictory reports have appeared. The formation layer, originated by surface induced heterogeneous nucleation, generally studied single model [2, 3]. This has also been case for glass (GF) reinforced polypropylene (PP) [5-8], where transcrystaUine- like structure could only be pro- duced when crystallizing PP melt sheared pulling embedded GF. In our recent work [9, 10], demonstrated columnar developed shearing tran- scrystalline, but row-nucleated cylindritic. We shown further 10] both crystalliza- tion (Tc) temperature (Tpull) are set range the/3-PP, i.e. T,~ ~ 100 °C T~, 140 [11, 12], /3-rich appears. Partial melting revealed layer attached pulled oi-PP contained ol-row nuclei originated/3-crystalliza- (c~-fl bifurcation growth, [11]). So under conditions To~ < To, Tpun T~o: GF resulted complex polymorphous containing o~- (row-nuclei along GF) fl-form (grown up onto oL-row nuclei). Due "/3-overgrowth" oc-layer resolved optical level after separate the/3-phase [10]. cited works shear [5, 6, 9, proved "inert", did show any o-nucleation ability. Therefore seemed very interesting study how above scenario changes ol-nucleating used. 0261-8028 © 1994 Chapman & Hall transcrystalliza- (due 0l-nucleation) row- cylindritic crystallization shear- ing) met. easily differentiate them taking into account polymorphism thus choosing following conditions: T~ Tpull T~. Under these development an o~-transcrystalline front evidence transcrystallization, while fl-PP rich indic- ates 10]. As oL-nucleating poly(ethylene-terephtha- late) (PET) taken from commingled PET/PP yarn supplied Toyobo Co. (Japan) ability PET reported several (cf. [7, 13, 14]). isotactic used general-purpose injection-mould- ing grade (Tipplen H-523, Tisza Chemical Works, Hungary). behaviour GF/PP were Leitz polarizing microscope equipped Mettler hot stage. All experimental details found previous Figs 1-3 effect isothermal its quiescent melt. Fig. 1 demonstrates structures formed 2-step crystallization. At higher T0 (Td = 134 °C, t~ 30 min) spherul- ites grown sporadically (Fig. la). Reducing min time (t~) To2 -- 124 gives rise o:-transcrystallization lb c). A well obtained 1-step crystallization, provided Tc low enough (To 2). indicates transcrystallization growth necessary high nucleation density guaranteed at ~< 130 given PP/PET composi- tion. strong using a/3-nucleated matrix 3). 3 shows preserves c~-nucleating even (achieved proprietary selective fl-nucleat- agent (in 0.1 wt %). oL-transcrystalline obvious, whereas/3-spherulites characterize bulk 3a). becomes more striking later) /3-phase Tf 158 3b). acts as