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The blocked isocyanate group (BHI) was synthesized to improve the storage stability of HI (2‐hydroxyethyl methacrylate combined with isophorone diisocyanate) and characterized by Fourier transform infrared spectroscopy (FTIR). High‐density polyethylene grafted with the blocked isocyanate group (HDPE‐g‐BHI) was used as a reactive compatibilizer for an immiscible high‐density polyethylene/poly(ethylene terephthalate) (HDPE/PET) blend. A possible reactive compatibilization mechanism is that regenerated isocyanate groups of HDPE functionalized by BHI react with the hydroxyl and carboxyl groups of PET during melt blending. The HDPE‐g‐BHI/PET blend showed the smaller size of a dispersed phase compared to the HDPE/PET blend, indicating improved compatibility between HDPE and PET. This increased compatibility was due to the formation of an in situ graft copolymer, which was confirmed by dynamic mechanical analysis. Differential scanning calorimetry (DSC) analysis represented that there were few changes in the crystallinity for the continuous PET phase of the HDPE‐g‐BHI/PET blends, compared with those of the HDPE/PET blends at the same composition. Tensile strengths and elongations at the break of the HDPE‐g‐BHI/PET blends were greater than those of the HDPE/PET blends. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 1017–1024, 2000

ABSTRACT:To evaluate the compatibilization effects of an isocyanate group on poly-(ethylene terephthalate)/polypropylene (PET/PP) blends through a reactive blend, PP grafted with 2-hydroxyethyl methacrylate-isophorone diisocyanate (PP-g-HI) was prepared and blended with PET. In view of the blend morphology, the presence of PP-g-HI reduced the particle size of the dispersed phase by the reduced interfacial tension between the PP and PET phases, indicating the in situ copolymer (PP-g-PET) generated during the melt blending. The DSC thermograms for the cooling run indicated that the PET crystallization in the PP-g-HI rich phase was affected by the chemical reactions of PET and PP-g-HI. The improved mechanical properties for the PET/PP-g-HI blends were shown in the measurement of the tensile and flexural properties. In addition, the water absorption test indicated that the PET/PP-g-HI blend was more effective than the PET/PP blend in improving the water resistance of PET. The positive properties of PET/PP-g-HI blends stemmed from the improved compatibilization of the PET/PP blend.

Polyurethane/clay nanocomposites have been synthesized using Na ϩ -montmorillonite (Na ϩ -MMT)/ amphiphilic urethane precursor (APU) chains that have hydrophilic polyethylene oxide (PEO) chains and hydrophobic segments at the same molecules. Nanocomposites were synthesized through two different crosslinking polymerization methods. One is UV curing of melt mixed APU/Na ϩ -MMT mixtures; the other is coalescence polymerization of APU/ Na ϩ -MMT emulsions. These two kinds of composites had intercalated silicate layers of Na ϩ -montmorillonite by insertion of PEO chains in APU chains, which was confirmed by X-ray diffraction measurement and transmission electron microscopy. These composite films also showed improved mechanical properties compared to pristine APU films. Although the two kinds of nanocomposites exhibited the same degree of intercalation and were synthesized based on the same precursor chains, these nanocomposite films had the different mechanical properties. Nanocomposites synthesized using APU/Na ϩ -MMT emulsions, having microphase-separated structure, had greater tensile strength than those prepared with melt-mixed APU/Na ϩ -MMT mixtures. Location of intercalated Na ϩ -MMT by PEO chains at the oil-water interface also could be confirmed by rheological behavior of the APU/Na ϩ -MMT/water mixture.

ABSTRACT:Monodisperse poly[styrene-co-glycidyl methacrylate (GMA)] microparticles were synthesized by dispersion copolymerization in a water-ethanol medium. The effects of various polymerization parameters on the particle size and size distribution of the dispersion copolymerization were investigated. The dispersion of polymer particles decreased when the GMA was added if the polystyrene homopolymer particles were polydispersed. The GMA acted as a comonomer as well as a costabilizer in the dispersion copolymerization of styrene with GMA. The solvency of the monomer increased with the concentration of GMA in the polymerization medium because GMA has a greater hydrophilicity than styrene, resulting in a large particle size and a slow polymerization rate. From an HCl-dioxane analysis of the poly(styrene-co-GMA) microparticles, great amounts of epoxy groups were detected after the completion of dispersion copolymerization.