Evolution of Crystalline Structures of Poly(.epsilon.-caprolactone)/Polycarbonate Blends. 1. Isothermal Crystallization Kinetics As Probed by Synchrotron Small-Angle X-ray Scattering

Abstract

Evolution of the poly(ecapro1actone) (PCL) lamellae in blends of PCL/PC (polycarbonate) was monitored by synchrotron small-angle X-ray scattering (SAXS). Theeffecta of crystallization temperature, PC concentration, and PC crystallinity on the PCL lamellar growth in the PCL-rich blends were investigated. The half-crystallization time derived from the temporal change of the peak intensity increased with crystallization temperature and generally increased with the addition of PC. For a given blend composition, the lamellar growth rate increased with increasing PC crystallinity. The interlamellar spacing initially varied with time and then approached a plateau value at the later stage of crystallization. An insertion mechanism is proposed in which the PCL is crystallized in the amorphous intralamellar phase. This model is also consistent with the quantitative SAXS results? which suggested that random mixing of PCL and PC lamellae occurred in the semicrystalline (PCL)/semicrystalline (PC) state.

Review on PCL, PBS, and PCL/PBS blends containing carbon nanotubes

“…The PCL/PC blend system is an example in which homogeneous mixing of the components in the melt and in the amorphous phase, over the whole composition range, is envisaged [51][52][53][54][55][56][57]. PCL/PC blends were found to be miscible, because a single T g , that varied with composition between those of the neat components, was observed ( Figure 1).…”

“…Several equations were proposed to predict the values of the glass transition temperature for miscible polymer blends [51][52][53]58]. The earliest of these equations was the Fox equation (Equation (2)): (2) where T g is the glass transition of the blend, and T gi and w i are the respective glass transitions and weight fractions of the components in the blend.…”

“…g is obtained by fitting the T g -composition data to the Braun-Kovacs equation. Even though the literature conflicts in some aspects such as different methods used for preparing the blends, solution-or melt mixing, and the compositional variation of the glass transition, Cheung and co-workers [52] concluded that the Fox equation can only accurately predict the glass transition temperature for compositions above 70% PC and that the Braun-Kovacs expression should be used in the other range. In contrast, Balsamo et al [53] and Ketelaars et al [51] accurately described the compositional variation with the Fox equation over the entire composition range.…”

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

“…The LTC can dwell in the interlamellar, interfibrillar, and interspherulitic regions of HTC if inserted at all. 88,[94][95][96] Small angle Xray scattering, 13,15,23,[39][40][41]51 laser scanning microscopy, 48 or atomic force microscopy 45,53 can yield information whether LTC forms individual lamellae or individual lamellar stacks after its own crystallization, or whether both blend components form mixed stacks. The growth direction of the intruding species into the host spherulite can also such be investigated.…”

“…25 PC/PCL blends, finally, shall crystallize in mixed lamellar stacks. 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).…”