Die kristallisation von polybutylenterephthalat (PBT) und polycarbonat (PC) im polymerblend PBT/PC

Abstract

ZUSAMMENFASSUNG:Das Kristallisationsverhalten sowohl von PBT als auch von P C ist im definiert verarbeiteten Blend infolge intermolekularer Wechselwirkungen zwischen den unterschiedlichen Molekulen in der Schmelze verandert.Die iiber die Glasubergangstemperaturen gemessene teilweise Mischbarkeit der amorphen Phasen fiihrt bei PBT zu einer Erniedrigung des Kristallinitatsgrades, wenn die kinetischen Bedingungen des Kristallisationsprozesses keine kristallisationsbedingte Entmischung zulassen. Der auf den PBT-Anteil normierte Kristallinitatsgrad ist bei kleinen Abkiihlgeschwindigkeiten vom PC-Anteil unabhangig.In der Mischung PBT/PC 40/60 Gew.-Vo kommt es bei hohen Kiihlraten zu einer fraktionierten Kristallisation. Die Kristallisationstemperatur bei anisothermer Kristallisation ist bei geringen PC-Gehalten durch Anderung des Keimbildungsmechanismus erhoht. Bei isothermer Kristallisation steigt mit zunehmendem PC-Anteil die Kristallisationshalbwertszeit des PBT an.Das normalerweise amorphe P C kann in Gegenwart von PBT in den PC-reichen Mischungen besonders schnell kristallisieren, wobei der Kristallisations-bzw. Ordnungsprozen des P C in situ mittels der Rontgenbeugung gemessen wurde. Kalorimetrische Untersuchungen bestatigen dieses Ergebnis und erlauben eine quantitative Abschatzung des PC-Kristallinitatsgrades zu ca. 20% im Blend PBT/PC 5/95 Gew.-Yo. SUMMARYThe crystallization behavior of PBT as well as PC is changed in the controlled-processed blend due to intermolecular interactions between the different macromolecules in molten state.If the kinetics of the crystallization process prevents a crystallization-induced separation, the partial miscibility of the amorphous phases, measured by the glass transition temperatures, will lead to a decrease of the crystallinity of PBT. The crystallinity, normalized to the concentration of PBT in the blend, is independent from the concentration of P C at low cooling rates. At high cooling rates, PBT is crystallizing stepwise in the blend PBT/PC 40/60 wt.-%. The crystallization temperature in the anisothermic crystallization process is increased at low contents of PC due to a changed nucleation mechanism. The half-time of crystallization is increasing in blends with an increasing PC-content in isothermic crystallization experiments.The normally amorphous PC crystallizes considerably fast in presence of PBT in PCrich blends. The crystallization or change in the state of order of PC was measured in situ by X-ray diffraction. Calorimetric experiments confirm this result and allow a quantitative estimation of the PC-crystallinity, which amounts to some 20% in the blend PBT/PC 5/95 wt.-%.

Blends of polyamide1010 with unmodified and maleic-anhydride-grafted high-impact polystyrene

“…The fractionated crystallization is characteristic for the crystallization behavior of a semicrystalline polymer blended with an incompatible polymer. This phenomenon has been observed so far in block copolymers comprising PEO-PE-PEO and PEO-PS 15,16 and in blends comprising PE-PS, 17 PP-SBS, 18 PE-POM, 19 PVDF-PA6, 20 PVDF-PA66, PA6 -PP, 21 PE-PP, PBT-PC, 22 and PA-ABS 23 when the crystallizable component is included in the noncrystallizable matrix in fine dispersed domains. The smaller the particles, the more distinct the effect.…”

Effect of compatibilization on the properties of HIPS/PA1010 blends

“…The fractionated crystallization is characteristic of the crystallization behavior of a semicrystalline polymer blended with an immiscible polymer. This phenomenon has been observed so far in block copolymers comprising PEO-PS 9, 10 and in blends comprised of PE/PS, 11 PVDF/PA6, 12 PA6/PP, 13 PBT/PC, 14 and PA/ABS 15 when the crystallizable component is included in the noncrystallizable matrix in finely dispersed domains. The smaller the particles, the more distinct is the effect.…”

Syntheses and characterization of poly(butylene terephthalate) copolyesters modified with p‐acetoxybenzoic acid

“…The main T m at higher temperatures decreases with increasing PABA concentration up to 30 mol % of PABA and then levels off, and the second small peak below the main peak increases slightly with increasing PABA content. The additional melting peak at a lower temperature is thought to arise from PBT crystals that form from the amorphous phase during annealing and that form from recrystallization of crystals that have lower melting points 23–26…”