Duck Kun Hwang

The preparation of isotactic polyacrylonitrile using zeolite

Abstract Isotactic polyacrylonitrile (PAN) has been prepared by using a zeolite as a host. After introduction of acrylonitrile monomers, they were subsequently polymerized with radical initiators in Na–Y and Na–β zeolite channels, followed by extraction with hydrofluoric acid. 13C-NMR results show that the isotacticity of extracted PAN is higher than that of bulk PAN prepared under the same reaction conditions and is also affected by the pore structure of host. Thermal and physical properties of extracted PAN were also investigated using GPC, DSC and XRD.

Thermal properties in strong hydrogen bonding systems composed of poly(vinyl alcohol), polyethyleneimine, and graphene oxide

Blends of poly(vinyl alcohol) (PVA), polyethyleneimine (PEI), and graphene oxide (GO) were prepared by solution casting method. Calorimetric thermal properties of the blends were investigated. The Tgs of PVA/PEI blends were higher than the Tgs of either of the component polymers at low concentrations of PEI. These abnormal increases of Tgs may be due to the negative entropy of mixing which is associated with strong hydrogen bonding between PVA and PEI. The degree of depression of s was not reduced by the negative entropy of mixing, since strong hydrogen bonding also causes an increase in the magnitude of negative c between PVA and PEI. The Tg of PVA was increased significantly by adding 0.7 wt.% GO into PVA. The magnitude of negative c was increased by adding GO into the blends of PVA and PEI

Method Development to Evaluate Melting Behavior of Glass Fiber-Reinforced Syndiotactic Polystyrene Composites in the Presence of Pressure Loading

Criteria of cycle time include metering, closing a mold, packing, holding, cooling, opening a mold and ejecting. Interestingly, metering time was found relatively lengthy in the composite of glass fiber (GF)-reinforced syndiotactic polystyrene (sPS) during injection molding. It was motivated by the ideas that analyzing dynamic thermal property may provide the correlation with metering time because differential scanning calorimeter does not fully provide dynamic thermal property. We created new measuring system to examine thermal behavior in the presence of pressure loading. The method was very effective to determine the melting rate of thermoplastics in the presence of pressure loadings.