Jin-Gyu Park

Blends of polybutyleneterephthalate with ethylene-propylene elastomer containing isocyanate functional group

Abstract Ethylene–propylene elastomer (EPM) grafted with an isocyanate-containing monomer (HI) was blended with polybutyleneterephthalate (PBT), and its morphological, rheological, and mechanical properties were studied. The monomer HI was prepared by the reaction of 2-hydroxylethylmethacrylate and isophorone diisocyanate. The HI was successfully incorporated onto EPM backbone through solution graft reaction with radical initiator. When the PBT was blended with HI-grafted EPM (EHI), the morphologies of the dispersed phase displayed differences with respect to particle size and interfacial adhesion, when compared with those of the PBT/EPM blend. The increase in complex viscosity, storage modulus and impact strength of PBT/EHI blends ensured that the compatibility between PBT and EPM was improved through functionalization of EPM with the isocyanate moiety. These results are mainly due to in situ graft PBT–EPM copolymer that formed through the chemical reaction between the isocyanate group of EHI and hydroxyl or carboxyl end groups of PBT.

Blends of polyethyleneterephthalate with EPDM through reactive mixing

Ethylene-propylene-diene elastomer (EPDM), which is grafted with an isocyanate-containing monomer (HI), was blended with polyethyleneterephthalate (PET) and its morphological, thermal, rheological, and mechanical properties were studied. HI was incorporated onto EPDM backbone through a solution graft reaction. When the PET was blended with HI-grafted EPDM (EPDM-g-HI), the morphologies of dispersed phases showed considerable differences in the aspects of particle size and interfacial adhesion compared with those of a PET/EPDM blend. DSC analysis showed that, when blends are cooled slowly, the PET phase in PET/EPDM-g-HI is somewhat amorphous compared with that in the PET/EPDM blend. The increase in complex viscosity, storage modulus and impact strength of PET/EPDM-g-HI blends enabled us to ensure that the compatibility between PET and EPDM improved through functionalization of EPDM with the isocyanate moiety. These results are mainly due to graft PET-EPDM copolymer in situ formed through the chemical reaction between the isocyanate group of EPDM-g-HI and hydroxyl or carboxyl end groups of PET.

Preparation of toughened PMMA through PEG-modified urethane acrylate/PMMA core–shell composite particles

Poly(urethane acrylate) (PUA)/poly(methylmethacrylate) (PMMA) core–shell composite particles were prepared by two-stage emulsion polymerization. The sizes of composite particles could be varied from 25 to 210 nm by introducing polyoxyethylene (POE) groups to the urethane acrylate molecular backbone. Core–shell morphology was identified by investigating the polarity of the surface of the core and shell polymer particles and by measuring the contact angle of the composite particles. A composite particle prepared with relatively small particles (about 20 nm) did not show the core/shell morphology, because the high polar surface of the core polymer particle and the low-stage ratio of the core to the shell cause the formation of a core/shell two-stage latex to be more thermodynamically unstable. The fracture toughness of rubber-toughened PMMA containing PUA/PMMA composite particles increased as the particle sizes decreased and the shell thickness of the composite particles increased. In particular, when the average size of the composite particle was about 43 nm and the stage ratio was 50/50, the fracture toughness of the rubber-toughened PMMA increased more than three times compared with that of pure PMMA. Furthermore, the transparency of toughened PMMA could be maintained up to 91% in the visible spectra range.

Monodisperse Micron-sized Polystyrene Particles by Seeded Polymerization Using Reactive Macrosurfactants

Monodisperse micron-sized polystyrene particles could be prepared through a two-staged seeded swelling and polymerization method using reactive surfactants. The seed was obtained by emulsifier-free emulsion polymerization. To prepare conventional surfactant-free monomer emulsion droplet in swelling process, a tri-block diol diacrylate (t-BDDA), which is poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) tri-block copolymer containing two chain ends capped with acryloyl chloride, was employed as a reactive surfactant instead of conventional surfactants. Thermodynamic consideration of the effect of monomer droplet size and interfacial tension on the swelling process ensured that two-staged monomer swelling could be effectively performed by using t-BDDA as a surface-active macromonomer. From the surface tension measurement and optical microscope observation, it was found that the t-BDDA had a favorable surface activity when the monomer emulsion was prepared under its cloud point. From the X-ray photoelectron spectroscopy, it was found that most of the t-BDDA resided on the final particle surfaces.