Jae Hyeung Park

Effect of montmorillonite on wettability and microstructure properties of zein/montmorillonite nanocomposite nanofiber mats

Zein is a hydrophobic protein produced from maize and has great potential in a number of industrial applications such as food, food coating and food packaging. The objectives of this study are to determine the effects of montmorillonite on the wettability and microstructure properties of zein/montmorillonite nanocomposite nanofiber mats fabricated by the electrospinning technique in ethyl alcohol aqueous solution. The zein/montmorillonite nanofiber mats were characterized by field-emission scanning electron microscopy, transmission electron microscopy, X-ray diffraction, differential scanning calorimetry, thermogravimetric analysis and contact angle measurements. This study shows that the introduction of montmorillonite resulted in the improvement of the thermal stability and hydrophilicity for the zein matrix. X-ray diffraction patterns and transmission electron microscopy micrographs suggest the coexistence of intercalated montmorillonite layers over the examined montmorillonite contents. Since montmorillonite is a hydrophilic clay, its addition can be used not only to produce nanomaterials with the already known improved properties but also to enhance the hydrophilicity of material.

Electrospinning Fabrication of Polyvinyl alcohol)/Waterborne Polyurethane/Silver Composite Nanofibre Mats in Aqueous Solution for Anti-bacterial Exploits

Nanofibre mats of poly(vinyl alcohol) (PVA), waterborne polyurethane (WBPU) and nanometre silver (Ag) colloids have been fabricated by an electrospinning method in aqueous solutions. Since PVA is a water soluble and biocompatible polymer, it is one of the best materials for preparation of electrospun antibacterial nanofibre mats. WBPU was used as a filler to enhance the properties of homopolymer nanofibre. Transmission electron microscopy analyses showed a uniform distribution of silver in the fibres. In anti-bacterial tests, the PVA/WBPU/Ag composite nanofibres showed excellent anti-bacterial performance, indicating practical uses as a new preservative. Moreover, the PVA/WBPU/Ag nanofibres showed improved thermal properties.

Electrospinning and Characterisation of Poly(vinyl alcohol) Blend Submicron Fibres in Aqueous Solutions

Poly(vinyl alcohol) (number-average degree of polymerisation 1700 (PVA-17) and 4000 (PVA-40)) blend submicron fibres were fabricated by the electrospinning method in an aqueous solution of 5–10% polymer concentration. Scanning electron microscopy (SEM), differential scanning calorimetry (DSC), X-ray diffraction (XRD), and thermal gravimetric analysis (TGA) were utilised to characterise the morphology and physical properties of the PVA fibres. The role of PVA blend mass ratio and concentration and of processing parameters such as applied voltage and capillary-to-collector distance in the production of ultrafine submicron PVA blend fibres was investigated. Uniform PVA fibres with an average submicron-scale diameter (250–600 nm) could be prepared from a 7.5% PVA-17/PVA-40 blend solution with various mass ratios. With a lower PVA blend concentration (5%), using different PVA-17/PVA-40 mass ratios, beads appeared in the fibre morphology, and homogeneity was also absent. At a higher PVA blend concentration (10%), larger-diameter (<700 nm) ribbon-like fibres were produced. Moreover, with a higher percentage of PVA-40 in the PVA blend fibres, superior crystallinity, thermal stability, and mechanical properties could be obtained by comparison with PVA-17.

Poly(vinyl alcohol)/montmorillonite/silver hybrid nanoparticles prepared from aqueous solutions by the electrospraying method

Poly(vinyl alcohol)/montmorillonite/silver hybrid nanoparticles are successfully fabricated by one-step electrospraying process in aqueous solution. The aim of this project is to design an optimum solution parameter for electrospraying system and evaluate inorganic material effects to antibacterial performance and thermal properties. Hybrid nanoparticles could be obtained at low molecular weight and concentration of the polymer. Transmission electron microscopy analysis showed montmorillonite and silver were well dispersed in poly(vinyl alcohol) nanoparticles and enhanced thermal properties of the composite material. In anti-bacterial test, the poly(vinyl alcohol)/montmorillonite/silver hybrid nanoparticles showed an excellent anti-bacterial performance.

Electrospraying Fabrication and Characterization of Low Molecular Weight Poly(vinyl alcohol)/Silver Composite Nanospheres for Antibacterial Applications

Low molecular weight poly(vinyl alcohol) (LMW-PVA)/silver (Ag) composite nanospheres were prepared using an electrospraying technique by controlling the concentration of PVA solution. Since PVA is water-soluble and biocompatible, it is one of the best polymers for preparation of antibacterial materials. The composite nanospheres were characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray diffraction (XRD), thermogravimetric analysis (TGA), and antibacterial activity measurement. The LMW-PVA/Ag composite nanospheres had ∼350 nm average diameter and showed powerful antibacterial ability.

Preparation of Low Molecular Weight Poly(vinyl alcohol)/ Montmorillonite Composite Nanoparticles Using an Electrospraying Technique

Composite nanoparticles composed of low molecular weight poly(vinyl alcohol) (LMW-PVA) and montmorillonite (MMT) were prepared using the electrospraying technique by regulating PVA solution concentration. Field-emission type scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, reflection type X-ray diffraction and thermal gravimetric analysis were utilized to characterize the LMW-PVA/MMT composite nanoparticles morphology and properties. MMT platelets were exfoliated and well distributed within the composite nanoparticles. It was also found that the thermal stability was enhanced by the addition of MMT.

Electrospinning Fabrication and Characterization of Water Soluble Polymer/Montmorillonite/Silver Nanocomposite Nanofibers out of Aqueous Solution

Polymer nanocomposites are a class of materials that have properties that offer significant commercial potential. It was commonly defined as the combination of a polymer matrix resin and inclusions that have at least one dimension (i.e. length, width, or thickness) in the nanometer size range. There are many types of nanocomposites that have received significant research and development including polymer/inorganic particle, polymer/polymer, metal/ceramic, and inorganic based nanocomposites. These polymer hybrid nanocomposites have attracted great interest due to inorganic materials filled polymer composites often exhibit remarkable improvement in material properties with only a low percentage of inorganic materials. High degrees of stiffness, strength, conductivity and thermal resistance, etc. are realized with far less high density inorganic material, they are much lighter compared to conventional polymer composites. Many novel nanocomposites with improved performance properties, which may have large potential applications in the fields such as optics, electrical devices, and photoconductors were reported (Fleming et al., 2001; Luna-Xavier et al., 2001; Tiarks et al., 2001). The synthesis of polymer nanocomposites is normally carried out by the following methods. One is based on in-situ polymerization of monomers inside the galleries of the inorganic host (Messersmith & Giannelis, 1993). The other approach is based on melt intercalation of polymers and it involves annealing a mixture of the polymer and the inorganic host, statically or under shear, above the Tg of the polymer (Usuki et al., 1997; Vaia et al., 1995). The solventless melt intercalation is an environmentally friendly technique and is adoptable to existing processing like roll milling, extrusion and molding. The materials made via these two processes have been summarized. Other unique methods for blending polymers directly with inorganic materials have employed microwaves, latex-colloid interaction, solvent evaporation, spray drying, spraying a polymer solution through a small orifice and Shirasu Porous Glass (SPG) membrane emulsification technique (Berkland et al., 2001; Fischer et al., 1999; Mu & Feng, 2001; Oriakhi & Lerner, 1995; Rosca et al., 2004).

Polymer/Montmorillonite/Silver Nanocomposite Micro- and Nanoparticles Prepared by In-Situ Polymerization and Electrospraying Technique

Polymer nanocomposite materials have the capacity for producing a synergetic association with surpassing merit properties which cannot be obtained from the individual components. Such materials can be obtained by simply mixing required organic and inorganic components. The introduction of inorganic material into the polymer matrix has proved to be an effective and low-cost method to improve the performance of the existing polymer materials (Okamoto et al., 2000; Ramos et al., 2000; Wu et al., 2006; Zhu et al., 2000). It has various applications, such as new biological materials (biosensors and biochips), biocompatible thin coatings for medical applications, biodegradable scaffolds, drug delivery system and filter systems (Matsumoto et al., 2005; Okuda et al., 1996; Salata et al., 1997; Sinha et al., 2004). The synthesis of polymer nanocomposites can be carried out by many different methods. For example, in-situ polymerization of monomers inside the galleries of the inorganic host has been one of the common methods for preparation of nanocomposites. Another common methods are based on melt intercalation, solventless melt intercalation, using microwaves, latex-colloid interaction, solvent evaporation, spray drying, shirasu porous glass membrane emulsification technique and electrospraying, etc. (Berkland et al., 2001; Ma et al., 1999; Messersmith et al., 1993; Mu et al., 2001; Oriakhi et al., 1995; Rosca et. al.,2004; Usuki et al., 1993). This article is concerned with fabrication of polymer nanocomposite particles by in-situ suspension polymerization and electrospraying which are represented as a traditional and current general method for synthesis of nanocomposite. The effectiveness of these nanocomposite particles are demonstrated with a field emission-type scanning electron microscope (FE-SEM), a transmission electron microscopy (TEM), an optical microscope, a reflection type X-ray diffraction (XRD), a