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Segmented thermoplastic polyurethanes, polyureas and polyurethaneureas (TPU) based on a given hard segment and two chemically different soft segments display interesting microphase morphologies and thermal, mechanical and surface properties. In these systems the final TPU morphology is mainly controlled by the structure, amount and molecular weight of the soft segment oligomers and the nature and...
The effects of methyl acrylate (MA) incorporation (0–15mol%) on the glass transition, melting behavior, and the peak temperature of the stabilization exotherm in acrylonitrile (AN) based copolymers were studied. A qualitative decrease in crystalline content with increasing MA content was observed using wide angle X-ray scattering (WAXS). The lower crystallinity of the high MA content copolymers could...
Polyacrylonitrile (PAN) terpolymers consisting of acrylonitrile/methyl acrylate (AN/MA) systems with added amounts of a termonomer (acid based) were synthesized in an effort to generate melt spinnable carbon fiber precursors. The complex viscosity was measured as a function of time in the temperature range of 200-220 o C, and was found to be dependent on both, the amount, as well as the nature...
This study introduces a novel high-temperature semicrystalline polyimide, which is based on an ether diamine (TPER or 1,3(4)APB) and BTDA dianhydride, both being commercially available. Phthalic anhydride is used as an endcap for improving thermal stability. The polyimide displays a Tg at ca. 230°C and two prominent melting endotherms at 360 and 416°C, respectively, with a sharp recrystallization...
The morphology and mechanical properties of emulsion blended samples of poly(tetrafluoroethylene) (PTFE) and poly(tetrafluoroethylene-co-vinylidene fluoride-co-hexafluoropropylene) (FKM) were investigated. Film samples with varying levels of PTFE content and varying degrees of FKM covalent cross-linking were produced. It was observed at room temperature that below 50wt% PTFE content, cross-linking...
Several linear polyethylene homopolymers of varied molecular weight (13=<M w =<839kg/mol) were synthesized with a metallocene catalyst and characterized. The synthetic approach resulted in relatively narrow molecular weight distributions (2.3<M w /M n <3.6) as measured by size exclusion chromatography. The melt rheological data, η * (ω) were modeled...
In this study, the morphology of polyurea hard domains in flexible polyurethane molded foams was investigated to evaluate the influence of diethanol amine (DEOA), a commercially utilized cross-linking agent. Tapping Mode AFM was utilized to reveal that DEOA dramatically alters the morphology of the solid state. Without DEOA, the solid state phase separation leads to the formation of lamellae-like...
Atomic force microscopy (AFM) and wide angle X-ray scattering (WAXS) were used to examine the morphology of hard domains in flexible polyurethane foams and plaques based on slabstock formulations. In plaque samples that were uniaxially deformed to 50% elongation, WAXS was utilized to demonstrate transverse hard segment orientation relative to the axis of deformation. AFM was utilized to directly observe...
A series of flexible polyurethane slabstock foam samples were prepared with varying surfactant concentration. Several samples were also prepared by quenching small pieces into liquid nitrogen during the foaming process. The morphology of these materials was characterized at many length scales via scanning electron microscopy (SEM), transmission electron microscopy (TEM), wide-angle and small-angle...
Lamellar thickness and its distribution in high-density polyethylene (HDPE) films having a well-defined stacked lamellar morphology were investigated by using differential scanning calorimetry (d.s.c.), small-angle X-ray scattering (SAXS), transmission electron microscopy (TEM) and atomic force microscopy (AFM). It was found that the most probable lamellar thicknesses from SAXS and TEM agrees very...
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