Phase diagram and crystallization of polycarbonate/poly‐ϵ‐caprolactone blends

Abstract

It is reported on the equilibrium melting point depression of polycarbonate from bisphenol A (PC) in its blend with poly-a-caprolactone (PCL). To this end, a model which explains the bended course of the measured Hoffman-Weeks plots is developed which takes into account the composition changes at the crystal growth front upon progressive crystallization. The occasional melting point depression of the PCL component is discussed. The calculated Flory-Huggins parameter of x12 = -0.09 indicates only weak enthalpic interactions. The remarkable drop in the glass transition temperature of PC with blending allows PC degrees of crystallinity up to 25% upon crystallization from the melt. ZUS AMMENFAS S UNG :Es wird iiber die Gleichgewichts-Schmelzpunktsdepression von Polycarbonat aus Bisphenol A (PC) in Mischungen mit Poly-E-caprolacton (PCL) berichtet. Hierzu wird ein Model1 entwickelt, das den gekriimmten Verlauf der gemessenen Hoffman-Weeks-Plots zu erkliiren vermag. Es beriicksichtigt die Konzentrationsinhomogenitaten, die mit fortscheitender Kristallisation an der Kristallwachstumsfront entstehen. Die gelegentlich beobachtete Schmelzpunktsdepression der PCL-Komponente wird diskutiert. Der Flory-Hugginssche Wechselwirkungsparameter wird zu -0,09 berechnet; aus diesem kleinen Wert mu8 geschlossen werden, dal3 die Mischungspartner enthalpisch nur schwach wechselwirken. Der merkliche Abfall der Glastemperatur des PC nach Einmischen von PCL bewirkt eine betrachtliche Kristallisation aus der Schmelze; es konnen PC-Kristallinitatsgrade bis zu 25% erreicht werden.

Thermal characterization of polycarbonate/polycaprolactone blends

“…PCL is a very effective polymeric plasticizer because, even with acetone vapors, PC is not able to crystallize fast enough to allow detection during the DSC cooling scans 16–18. Even though crystallization during the cooling scan may be implicit in previous works,2, 4, 11, 12 these works did not show the cooling scans from the melt (e.g., those in Fig. 1) but the subsequent heating scans (analogous to those in Fig.…”

“…One example of two crystallizable polymers that mix homogeneously in the melt at all compositions is the bisphenol A polycarbonate/poly(ϵ‐caprolactone) (PC/PCL) blend system 1–4. In this case, one glass transition can be detected because, upon cooling, the amorphous phase remains a homogeneous mixture of both polymers.…”

“…This analysis for the PCL component yielded a linear dependence of the melting point on the crystallization temperature ( T c ). However, for PC an upward‐bent curve has been presented 2, 4. Hatzius et al4 attributed such behavior to a compositional change at the crystallizing front.…”

“…However, for PC an upward‐bent curve has been presented 2, 4. Hatzius et al4 attributed such behavior to a compositional change at the crystallizing front. However, they obtained a χ 12 of −0.097, similar to that reported by Kim and Paul 9…”

Crystallization kinetical and morphological peculiarities in binary crystalline/crystalline polymer blends

“…39,41 That blend system is interesting in that the low T g component PCL enables the PC-whose high T g usually inhibits its crystallization-to crystallize to a remarkable extent. 36,37,41 Simultaneous crystallization (in the sense that the components crystallize at the same time) upon isothermal conditions, and the IPC as well as the ILC schemes, respectively, could be realized, for example, in the blend PBSU/ P(VDC-co-VC), [46][47][48][49][50][51][52][53] in the blend PESU/PEO 26,28 and in the blend PLA/P(BSU-co-BC). 44,45 The actual crystallization scheme-whether S-co-S, IPC, ILC, or IFC, whether one-step or two-step crystallization occurs-depends clearly on the composition and on the thermal conditions.…”