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Strongly interacting amorphous poly(p-vinyl phenol) (PVPh) was added into semi-crystalline poly(ethylene oxide) (PEO) at 20 wt.% to generate dendritic lamellae of alternating birefringence colors, which intertwine roughly in the radial directions as periodic stripes. Optical and atomic-force microscopy analyses are performed on revealing lamellae assembly in highly dendritic PEO spherulites by crystallizing PEO/PVPh (80/20) at crystallization temperature ( T ) equals to 45 °C. The lamellae of two opposite colors in the same PEO spherulite quadrant are exactly of same geometry (of elongated plates, each being 0.2 μm in width and 2-5 μm in length), but they fan out +/−45, respectively, as they grow away from the radial direction. The opposite colored-lamellae are radiating out in radial directions, interweaving each other to display alternating colors in radial alignment. However, such alternating colors can also be similarly seen in ring-banded spherulites in many polymers. The results presented in this study have demonstrated that the lamellae of alternating birefringent colors cannot only be seen in banded spherulites, but also in spherulites with radial dendrites. [ABSTRACT FROM AUTHOR]

In this study the use of polyurethane foam (PUF) as a heat seal coating for potential application in medical pouch packaging were investigated. We prepared PUF coatings at various foam densities and cell densities through mechanical foaming at various stirring speeds; then used a LUMisizer to examine their stabilities. After applying PUF coatings of various foam densities onto a medical packaging material (Tyvek®) at various thicknesses, then employed impulse heat sealing with linear low density polyethylene (LLDPE) films to fabricate medical pouches. In addition to investigating the morphology, tack properties, adhesion, scratch resistance, flexibility, and durability of the PUF coats, the peel strength and air permeability of the medical pouches were also measured. Increasing the foam density of the PUF coatings increased their stability; the PUF coats prepared at a higher foam density exhibited greater tackiness (<1 g/cm), adhesion (5B), scratch resistance (HB), flexibility (passes), and durability (Δ YI ≤ 5). The peel strength measured in the T-peel configuration increased upon increasing the foam density and decreasing the coating thickness of the PUF coat/LLDPE pouches. The air permeability of the pouches increased upon increasing the foam density and cell density of the PUF coat/LLDPE pouches. Morphological studies using scanning electron microscopy were consistent with the experimental results. [ABSTRACT FROM AUTHOR]

In this study, we used a LUMiSizer® analytical centrifuge to determine the particle dispersions and size distributions of organic/inorganic composite coatings. The centrifuge was capable of recording both the measure space and time-resolved extinction profiles (STEP™-Technology) for up to 12 samples simultaneously, making it a powerful tool for the characterization and quality control of coatings. While the variation of the light extinction curves after centrifugal segregation provided a qualitative description, a rigorous formulation can provide detailed quantitative characterization. The technique used in this study allowed demixing to be accelerated and direct quantification of the dispersibility of the coatings. Because the dispersants and binders stabilized the organic/inorganic composite coatings, the dispersibility strongly depended on their concentration. The dispersibility of the coatings increased upon increasing the dispersant concentration and decreasing the concentration of the binder. Furthermore, the inorganic particles exhibited good dispersibility, without large degrees of aggregation, in the coating dispersions. We also used the LUMiSizer® to determine the particle size distribution and shelf life of coatings; the results were comparable with those obtained using dynamic light scattering, scanning electron microscope and zeta potential analysis. [ABSTRACT FROM AUTHOR]