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.
Axial compressive behavior of seawater sea-sand recycled aggregate concrete-filled double-skin non-corrosive tubular columns with square cross-section
Abstract This paper presents the results of an experimental investigation on mechanical properties of seawater sea-sand recycled aggregate concrete (SSRAC) filled double-skin tubular square columns (DSTCs). A total of 45 square DSTCs, included 12 fully-filled FRP confined SSRAC (fiber-reinforced polymer) columns, 21 FRP-SSRAC-aluminum tube columns, and 12 FRP-SSRAC-stainless steel tube columns, were tested under axial compression. The effects of the key parameters, including void ratio, recycled aggregate (RA) replacement ratio, and tube materials’ properties, on the structural behavior of SSRAC-filled square DSTCs are discussed. The test results indicate that mixing seawater and sea-sand with RAs could make up the early strength reduction caused by RA replacement. The void ratio significantly influences the stress–strain relationship of SSRAC filled in DSTCs due to the nonuniform hoop confinement pressure caused by the square cross-section. This nonuniform hoop confinement is also highly related to the inner tubes’ material properties due to their different local buckling behaviors. The test results are also used to assess the suitability of existing models proposed for different kinds of DSTCs. The evaluation results suggest that the models could provide satisfying predictions as long as the corner radius and void ratio’s coupling effects are reasonably considered.
Miscibility of poly(ether imide) and poly(ethylene terephthalate)
DSC results show the miscibility of blends composed of poly(etherimide) (Ultem 1000) and PET and the strong influence that the PEI has on the crystallization-melting characteristics of PET in the blends