Han Mo Jeong

Shape memory polyurethane containing mesogenic moiety

The mechanical and thermal properties, in particular the shape memory effect, of TPUs synthesized from diol-terminated poly(caprolactone) (PCL diol), 4,4′-diphenylmethane diisocyanate (MDI), and mesogenic chain extenders, 4,4′-bis-(2-hydroxyethoxy)biphenyl (BEBP) or 4,4′-bis-(6-hydroxyhexoxy)biphenyl (BHBP) were examined and compared with results for PCL diol/MDI/1,4-butanediol (BD) based TPUs in a previous study. Some results related to the rigid structure of BEBP or BHBP were observed in the thermomechanical properties. Shape fixity was related to the crystallization of the PCL phase.

Morphological, thermal and rheological properties of the blends polypropylene/nylon-6, polypropylene/nylon-6/(maleic anhydride-g-polypropylene) and (maleic anhydride-g-polypropylene)/nylon-6

Abstract Melt blends of polypropylene(PP)/nylon-6, PP/nylon-6/(maleic anhydride-g-polypropylene-(MAH-g-PP)) and (MAH-g-PP)/nylon-6 have been prepared using a Brabender plasticoder. Measured properties included steady shear viscosities from a capillary rheometer, thermal properties from DSC, and morphologies from SEM. The viscosity-composition curve, measured at low rate of shear, indicated negative deviation from the simple additive rule for PP/nylon-6 blends, positive deviation for PP/nylon-6/MAH-g-PP blends and positive and negative deviations for MAH-g-PP/nylon-6 blends. The results have been interpreted in terms of morphological texture of the blends and chemical reactions between the constituent polymers.

Aqueous dispersion of polyurethane ionomers from hexamethylene diisocyanate and trimellitic anhydride

Polyurethane (PU) ionomers were prepared from trimellitic anhydride (TMA), poly(tetramethylene adipate) glycol (PTAd), and hexamethylene diisocyanate (HDI) in acetone. Upon neutralizing the carboxylic groups with a tertiary amine (TEA), and adding water to PU ionomer solution, followed by removing the acetone, stable aqueous PU dispersions were obtained.Effects of interionic molecular weight and nonionic hydrophilic segment, viz. monofunctional ethylene-propylene oxide ether on particle, size, emulsion viscosity, mechanical, and viscoelastic properties of the emulsion cast films were examined.

Compatibility enhancement of ABS/polycarbonate blends

The effects of blend composition, melt viscosity of poly(acrylonitrile-butadiene-styrene) (ABS), and compatibilizing effect of poly(methyl methacrylate) (PMMA) on mechanical properties of ABS/polycarbonate (PC) blends at ABS-rich compositions were studied. As the content of PC was increased, impact strength and Vicat softening temperature (VST) were increased. As the melt viscosity of ABS was increased near to that of PC, finer distribution of dispersed PC phase and consequent enhanced impact strength and VST were observed. The compatibilizing effect of PMMA can be ascer-tained from the enhanced properties of ¼-inch notch impact strength, VST, tensilestrength, and the morphology observed by a scanning electron microscope. The improved adhesion of the ABS/PC interface by PMMA changed the fracture mechanism and reduced the notch sensitivity of blends.

Miscibility of tetramethyl polycarbonate with syndiotactic polystyrene

Abstract Tetramethyl polycarbonate (TMPC) and syndiotactic polystyrene ( s -PS) are miscible, showing single glass transition temperature in blends. The crystallization behavior of s -PS in blends with TMPC was retarded by the miscible TMPC. The binary interaction energy density B, between TMPC and s -PS was calculated from the melting point depression of s -PS to be −0.92xa0J/cm 3 .

Aqueous Dispersion of Polyurethane Anionomer from Aliphatic Diisocyanates and Poly(Hexamethylene Carbonate) Diol

Abstract Water dispersible polyurethanes (PUs) were prepared from poly(hexamethylene carbonate) (PHC) diol, isophorone diisocyanates (IPDI), hexamethylene diisocyanate (HDI), and dimethylolpropionic acid (DMPA) as latent anionic sites. After neutralization of the carboxyl group from the DMPA unit with triethylamine (TEA), the PU anionomers were dispersed by adding water, following by crosslinking using triethylenetetramine (TETA). The particle size of the dispersion decreased with the content of DMPA and increased with HDI in the HDI-IPDI system, and it exhibited a minimum when the number-average molecular weight (M n) of the prepolymer was 3000 and 4500, respectively. PUs with a higher content of hard segments from DMPA or TETA, or with a higher content of IPDI rather than HDI, had higher tensile moduli and storage moduli at room temperature. Ultimate tensile properties increased with an increase of the prepolymer molecular weight and the DMPA and HDI content.

Synthesis and application of polyarylate-poly(methyl methacrylate) block copolymer as compatibilizer for polyarylate/poly(vinylidene fluoride) blend

Abstract Polyarylate (PAR)-poly(methyl methacrylate) (PMMA) block copolymers were synthesized via radical polymerization of methyl methacrylate using a macroinitiator. The compatibilizing effect of this block copolymer in PAR/poly(vinylidene fluoride) (PVDF) blends was investigated by examining thermal properties, morphology and surface characteristics. The depression of melting point of PVDF and the increase in Tg of PAR with increasing PAR content in PAR/PVDF/PAR-PMMA block copolymer ternary blends were accentuated by the addition of the PAR-PMMA block copolymer. Furthermore, a rather finer dispersion was obtained by the addition of block copolymer, which is evidenced also by contact angle measurements, showing that the contact angle of blend is greatly influenced by the presence of block copolymer. These experimental results clearly demonstrate the compatibilizing effect of PAR-PMMA block copolymer in PAR/PVDF blends.