Won-Jei Cho

Environmentally friendly polymer hybrids Part I Mechanical, thermal, and barrier properties of thermoplastic starch/clay nanocomposites

As an attempt to develop environmentally friendly polymer hybrids, biodegradable thermoplastic starch (TPS)/clay nanocomposites were prepared through melt intercalation method. Natural montrorillonite (Na+ MMT; Cloisite Na+) and one organically modified MMT with methyl tallow bis-2-hydroxyethyl ammonium cations located in the silicate gallery (Cloisite 30B) were chosen in the nanocomposite preparation. TPS was prepared from natural potato starch by gelatinizing and plasticizing it with water and glycerol. The dispersion of the silicate layers in the TPS hybrids was characterized by using wide angle X-ray diffraction (WAXD) and transmission electron microscopy (TEM). It was observed that the TPS/Cloisite Na+ nanocomposites showed higher tensile strength and thermal stability, better barrier properties to water vapor than the TPS/Cloisite 30B nanocomposites as well as the pristine TPS, due to the formation of the intercalated nanostructure. The effect of clay contents on the tensile, dynamic mechanical, and thermal properties as well as the barrier properties of the nanocomposites were investigated.

Preparation and Properties of Biodegradable Thermoplastic Starch/Clay Hybrids

Biodegradable thermoplastic starch (TPS)/clay hybrids were prepared by melt intercalation. Three organically modified montmorillonite (MMT) with different ammonium cations and one unmodified Na+ MMT (Cloisite Na+) were used. Cloisite Na+ showed the best dispersion in the TPS matrix. It was observed that the TPS/Cloisite Na+ hybrid showed an intercalation of TPS in the silicate layer due to the matching of the surface polarity and interactions of the Cloisite Na+ and the TPS, which gives higher tensile strength and better barrier properties to water vapor as compared to the other TPS/organoclay hybrids as well as the pristine TPS. It was found that the dynamic mechanical properties of the TPS/clay hybrids were also affected by the polar interactions.

Microstructure, tensile properties, and biodegradability of aliphatic polyester/clay nanocomposites

Novel biodegradable aliphatic polyester (APES)/organoclay nanocomposites were prepared through melt intercalation method. Two kinds of organoclays, Cloisite 30B and Cloisite 10A with different ammonium cations located in the silicate gallery, were chosen for the nanocomposites preparation. The dispersion of the silicate layers in the APES hybrids was characterized by using X-ray diffraction (XRD) and transmission electron microscopy (TEM). Tensile properties and the biodegradability of the APES/organoclay nanocomposites were also studied. APES/Cloisite 30B hybrids showed higher degree of intercalation than APES/Cloisite 10A hybrids due to the strong hydrogen bonding interaction between APES and hydroxyl group in the gallery of Cloisite 30B silicate layers. This leads to higher tensile properties and lower biodegradability for APES/Cloisite 30B hybrids than for the APES/Cloisite 10A hybrids.

Miscibility, properties, and biodegradability of microbial polyester containing blends

The blending of poly[(R)-3-hydroxybutyrate] [P(3HB)] or poly((R)-3-hydroxybutyrate-co-3-hydroxyvalerate) [P(3HB-co-3HV)] with other synthetic polymers has attracted much interest as one approach to improve the inherent brittleness as well as to reduce high production cost of the microbial polyesters. Crystallization behavior, physical properties, and biodegradation behaviors of the microbial polyester containing blends are significantly affected by the nature of the blend partner component depending on whether it is biodegradable or not and/or whether it is miscible with the microbial polyesters or not. In this article, we have a critic review on the recent progress of the polymer blends based on the microbial polyesters.

Preparation and Characterization of Poly(butyleneterephthalate)/Organoclay Nanocomposites

PBT/organic montmorillonite (MMT) nanocomposites were prepared via melt intercalation and their nanostructure was characterized by means of X-ray diffraction and transmission electron microscopy. Nanocomposite formation requires sufficiently hydrophobic organically modified layered silicates, as well as the presence of polar interactions between silicate and polymer. Three different alkylammonium surfactants were used to modify MMT. In addition, epoxy resin was added as a third component, and the effects on the intercalation and exfoliation behavior of the PBT nanocomposites were investigated.

Reactive compatibilization of the PBT/EVA blend by maleic anhydride

This study concerns the reactive compatibilization of the blend of poly(butylene terephthalate) (PBT) and ethylene/vinyl acetate copolymer (EVA) by maleic anhydride (MAH). First, the graft copolymerization of EVA with MAH was investigated using dicumyl peroxide (DCP) as an initiator by melt free radical grafting in a plasticorder (Haake). The concentrations of MAH and DCP were varied from 0 to 3.0 phr and from 0 to 0.4 phr, respectively. EVA-g-MAH formed by the grafting reaction of EVA and MAH in the presence of DCP exhibits a significantly lower torque value than EVA bearing no MAH. PBT was blended with thus-obtained EVA-g-MAH using the same plasticorder. For comparison, PBT/EVA blend was also prepared. The FTIR spectroscopic studies showed that PBT-g-EVA copolymer was formed by the in situ interfacial reaction of MAH grafted onto EVA with the carboxylic and/or hydroxyl groups at the chain ends of PBT in the blend systems. The impact strength of PBT/EVA-g-MAH (80/20) blend showed about three-fold increase in comparison with PBT/EVA (80/20) blend due to the enhanced interfacial adhesion by the formation of in situ compatibilizer, i.e. PBT-g-EVA copolymer. Also, the morphology of the blends was observed with scanning electron microscope (SEM).

Properties of uncompatibilized and compatibilized poly(butylene terephthalate)-LLDPE blends

In this work, blends of poly(butylene terephthalate) (PBT) and linear low-density polyethylene (LLDPE) were prepared. LLDPE was used as an impact modifier. Since the system was found to be incompatible, compatibilization was sought for by the addition of the following two types of functionalized polyethylene: ethylene vinylacetate copolymer (EVA) and maleic anhydride-grafted EVA copolymer (EVA-g-MAH). The effects of the compatibilizers on the rheological and mechanical properties of the blends have been also quantitatively investigated. The impact strength of the PBT–LLDPE binary blends slightly increased at a lower concentration of LLDPE but increased remarkably above a concentration of 60 wt % of LLDPE. The morphology of the blends showed that the LLDPE particles had dispersed in the PBT matrix below 40 wt % of LLDPE, while, at 60 wt % of LLDPE, a co-continuous morphology was obtained, which could explain the increase of the impact strength of the blend. Generally, the mechanical strength was decreased by adding LLDPE to PBT. Addition of EVA or EVA-g-MAH as a compatibilizer to PBT–LLDPE (70/30) blend considerably improved the impact strength of the blend without significantly sacrificing the tensile and the flexural strength. More improvement in those mechanical properties was observed in the case of the EVA-g-MAH system than for the EVA system. A larger viscosity increase was also observed in the case of the EVA-g-MAH than EVA. This may be due to interaction of the EVA-g-MAH with PBT.

Fracture toughness and properties of plasticized PVC and thermoplastic polyurethane blends

Abstract In this work, fracture toughness and properties of blends of plasticized poly(vinyl chloride) (PVC) and thermoplastic polyurethane (TPU) were investigated. Two kinds of TPU with different hardness, i.e. TPU90 (Shore A hardness 90) and TPU70 (Shore A hardness 70) were compared. PVC/TPU90 and PVC/TPU70 blends with variable weight ratio ( 100 0 , 90 10 , 80 20 , 70 30 , 60 40 , 50 50 , 0 100 ) were prepared by melt blending. Fracture toughness was investigated using the J-integral by locus method. Blending of TPU with plasticized PVC improved tensile strength, impact strength, abrasion resistance, and thermal stability, with small decline of tensile modulus and hardness. The PVC/TPU blends showed flame retardancy over the composition ranges, regardless of the hardness of TPU, except the PVC/TPU70 of 50 50 composition, in terms of the limiting oxygen index. PVC/TPU70 blends showed higher Jc values and thus higher fracture toughness over the entire composition than PVC/TPU90 blends. For the PVC/TPU70 blends, the SEM micrographs showed clear dimple rupture fracture topology, while the PVC/TPU90 blends did not.

Preparation of TiO2 nanoparticles in glycerol-containing solutions

Abstract TiO 2 nanoparticles were prepared from titanium isopropoxide by using a new solvent system containing glycerol. The particle size by scanning electron microscopy was in the range of 4–10 nm. The X-ray diffraction data revealed that the nanoparticles possess mostly a tetragonal crystal structure of anatase. The absorption of the tetrahedral titanium species at 280 nm on UV spectra exhibited the quantum size effect of the nanoparticles.

Compatibilizer in polymer blends for the recycling of plastics waste I: Preliminary studies on 50/50 wt% virgin polyblends

In this work, comparative studies have been made to investigate the effectiveness of several compatibilizers for three kinds of virgin plastic mixtures, high-density polyethylene (HDPE)/polypropylene (PP), low-density polyethylene (LDPE)/PP and HDPE/polystyrene (PS) blends, in order to gain insight into the recycling of wastes from those frequently encountered mixed plastics. Three copolymers were tested as potential compatibilizers for those blends: ethylene—propylene—diene terpolymer (EPDM)-g-maleic anhydride (EPDM-g-MAH) for HDPE/PP and LDPE/PP blends, styrene—ethylene (butylene—styrene) (SEBS) and SEBS-g-MAH, for HDPE/PS blends. The properties and morphology of each ternary blend containing a coplymeric compatibilizer were measured with differential scanning calorimeter, X-ray diffractometer, tensile tester and scanning electron microscope. The concentration of the graft copolymer was varied from 0 to 20 phr, whereas the blend composition was fixed at 50/50 by weight %. It was found that EPDM-g-MAH showed good compatibilizing effect for LDPE/PP blends but not for HDPE/PP blends, in general. It was also found that SEBS showed much better compatibilizing effects for HDPE/PP blend than the SEBS-g-MAH blend.