Phase Behavior and Its Effects on Crystallization in a Poly(trimethylene terephthalate)/Phenoxy Resin Blend
Phase behavior and its effects on crystallization in an extruded poly(trimethylene terephthalate) (PTT)/phenoxy resin blend were studied with time-resolved light scattering (TRLS), optical microscopy (OM), differential scanning calorimetry (DSC), and small-angle X-ray scattering (SAXS). During annealing in the molten state, a two-phase structure with unique periodicity and phase connectivity was developed by liquid–liquid phase separation. After the formation of the phase-separated structure, the blend was homogenized by the interchange reactions between the two polymers. The crystallization behavior of PTT predominantly depended on the phase morphology developed during annealing. The pre-existing phase structures disturbed the lamellar orientation, resulting in a poorly ordered spherulitic superstructure.
Morphology development in isotactic polypropylene/partially hydrogenated oligo(styrene-co-indene) blend
We investigated the spherulite formation in an isotactic polypropylene (iPP)/partially hydrogenated oligo(styrene-co-indene) blend by time-resolved light scattering equipped with a CCD camera system and TEM. The V v (parallel polarization) light scattering pattern at a high crystallization temperature (T c = 105 °C) changed from a single-ring pattern to a double-ring one and then to a circular symmetric one. Based on model calculation, the formation of the ring pattern can be interpreted by the positive birefringence spherulite which is expected to appear when the crosshatched lamellae sufficiently develop. The H v (cross-polarization) light scattering pattern was the rod type, implying that a high level of orientation ordering was established in radial direction but a low level in tangential one. It is consistent with the above argument on the V v patterns since the less ordering in tangential orientation could be caused by the crosshatching. Similar analysis on the crystallization at a low temperature (T c = 85 °C) showed a formation of noncrosshatched and fragmented lamellae. The analysis was supported by the TEM observation. Thus, we found that the new morphologies are available by adding miscible impurity and controlling the T c .
Direct conversion pulsed UWB transceiver architecture
Ultra-wideband (UWB) communication is an emerging wireless technology that promises high data rates over short distances and precise locationing. The large available bandwidth and the constraint of a maximum power spectral density drives a unique set of system challenges. This paper addresses these challenges using two UWB transceivers and a discrete prototype platform.