• Korean Journal of Materials Research
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• v.21 no.7
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• pp.384-390
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• 2011

Ti-6Al-4V ELI (Extra Low Interstitial) alloy has been widely used as an alternative to bone due to its excellent biocompatibility. However, it still has many problems, including a high elastic modulus and toxicity. Therefore, nontoxic biomaterials with a low elastic modulus should be developed. However, the fabrication of a uniform coating is challenging. Moreover, the coating layer on Ti and Ti alloy substrates can be peeled off after implantation. To overcome these problems, it is necessary to produce bulk Ti and Ti alloy with hydroxyapatite (HA) composites. In this study, Ti, Nb, and Zr powders, which are biocompatible elements, were milled in a mixing machine (24h) and by planetary mechanical ball milling (1h, 4h, and 6h), respectively. Ti-35%Nb-7%Zr and Ti-35%Nb-7%Zr-10%HA composites were fabricated by spark plasma sintering (SPS) at $1000^{\circ}C$ under 70MPa using mixed and milled powders. The effects of HA addition and milling time on the biocompatibility and physical and mechanical properties of the Ti-35%Nb-7%Zr-(10%HA) alloys have been investigated. $Ti_2O$, CaO, $CaTiO_3$, and $Ti_xP_y$ phases were formed by chemical reaction during sintering. Vickers hardness of the sintered composites increases with increased milling time and by the addition of HA. The biocompatibilty of the HA added Ti-Nb-Zr alloys was improved, but the sintering ability was decreased.

• Proceedings of the Materials Research Society of Korea Conference
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• 2009.11a
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• pp.18.2-18.2
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• 2009

Ceramics have some properties that are unmatched by other kind of materials like metals or polymers. The ability of high thermal and chemical resistance and in case of being superior in specific mechanical properties makes the ceramic materials suitable for arange of applications. The microstructure and morphology of a material arguably permit the use of many advanced application otherwise difficult to achieve.Porous structures have some important applications in biomedical and environmental field. For human hard tissue reconstruction and augmentation procedure suitable biomaterials are used with a desirable porosity. A range of porous bioceramics were fabricated with tailored design to meet the demand of specific applications. Channeled and interconnected porosity was introduced in alumina, zirconia, and hydroxyapatite or tri calcium phosphate ceramics by different methods like multi-pass extrusion process, bubble formation in viscous slurry,slurry dripping in immiscible liquid, sponge replica method etc. The detailed microstructural and morphological investigations were carried out to establish the unique features of each method and the developed systems. For environmental filters the porous structures were also very important. We investigated a range of channeled and randomly porous silicon based ceramic composites to enhance the material stability and filtration efficiency by taking advantage of the material chemistry of the element. Detailed microstructural and mechanical characterizations were carried out for the fabricated porous filtration systems.

• Proceedings of the Materials Research Society of Korea Conference
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• 2010.05a
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• pp.41.2-41.2
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• 2010

In this work, HAp-(t-ZrO2) ceramic composites of biomimic artificial bone were fabricated by multi-extrusion process in order to replace nature bone. HAp-(t-ZrO2) and graphite powders were mixed separately with ethylene vinyl acetate (EVA) and stearic acid using shear mixer. Extruded HAp-(t-ZrO2) filaments and carbon filaments were arranged in the die to fabricate the first pass filament. The first pass filaments were arranged in the same die with a central carbon core for making the space for spongy bone. Burning out and sintering processes were performed to remove the binder and lubricant. The microstructure channel diameter was researched around $300{\mu}m$. Microstructure analysis was carried out by OM, SEM, and $\mu$-CT. Compressive strength was investigated for the artificial bone. Some preliminary bio-compatibility test was evaluated.

• Elastomers and Composites
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• v.50 no.4
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• pp.292-296
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• 2015

Biomimetic artificial basilar membrane being a core part of artificial cochlear requires performance evaluation through aging test. To evaluate the aging properties of PVDF piezoelectric membrane used for artificial basilar membrane, its mechanical properties such as tensile strength and elastic modulus and piezoelectric property such as piezoelectric constant were measured. The aging test conditions and acceleration constants were calculated based on Arrhenius model. The changes in tensile strengths and elastic moduli measured were less than 10~20% after aging test equivalent for 10 years. The piezoelectric constants were decreased drastically to 80% of its initial value in the early stage of the aging test and expected to decrease slowly down to 65% over 10 years. The experimental results show the reliability of totally implantable novel artificial cochlear and will contribute its commercialization.

• Macromolecular Research
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• v.16 no.3
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• pp.253-260
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• 2008

Environmentally friendly biocomposites were made using plant-based natural fibers, such as henequen and kenaf. The natural fiber reinforced polypropylene (PP) and unsaturated polyester (UP) biocomposites were examined in terms of the reinforcing effect of natural fibers on thermoplastic and thermosetting polymers. Kenaf (KE) and henequen (HQ) fibers were treated with an electron beam (EB) of 10 and 200 kGy doses, respectively, or with a 5 wt% NaOH solution. Four types of biocomposites (KE/PP, HQ/PP, KE/UP and HQ/UP) were fabricated by compression molding and each biocomposite was characterized by dynamic mechanical analysis and thermogravimetric analysis. The kenaf fiber had the larger reinforcing effect on the dynamic mechanical properties of both PP and UP biocomposites than the henequen fiber. The highest storage modulus was obtained from the biocomposite with the combination of UP matrix and 200 kGy EB treated kenaf fibers.

• Elastomers and Composites
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• v.56 no.3
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• pp.136-151
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• 2021

Biomass lignin, a waste produced during the paper and bio-ethanol production process, is a cheap material that is available in large quantities. Thus, the interest in the valorization of biomass lignin has been increasing in industrial and academic areas. Over the years, lignin has been predominantly burnt as fuel to run pulping plants. However, less than 2% of the available lignin has been utilized for producing specialty chemicals, such as dispersants, adhesives, surfactants, and other value-added products. The development of value-added lignin-derived co-products should help make second generation biorefineries and the paper industry more profitable by valorizing lignin. Another possible approach towards value-added applications is using lignin as a component in plastics. However, blending lignin with polymers is not simple because the polarity of lignin molecules results in strong self-interactions. Therefore, achieving in-depth insights on lignin characteristics and structure will help in accelerating the development of lignin-based products. Considering the multipurpose characteristics of lignin for producing value-added products, this review will shed light on the potential applications of lignin and lignin-based derivatives on polymeric composite production. Moreover, the challenges in lignin valorization will be addressed.

• Maxillofacial Plastic and Reconstructive Surgery
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• v.42
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• pp.18.1-18.9
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• 2020

Background: Bone grafting has been considered the gold standard for hard tissue reconstructive surgery and is widely used for large mandibular defect reconstruction. However, the midface encompasses delicate structures that are surrounded by a complex bone architecture, which makes bone grafting using traditional methods very challenging. Three-dimensional (3D) bioprinting is a developing technology that is derived from the evolution of additive manufacturing. It enables precise development of a scaffold from different available biomaterials that mimic the shape, size, and dimension of a defect without relying only on the surgeon's skills and capabilities, and subsequently, may enhance surgical outcomes and, in turn, patient satisfaction and quality of life. Review: This review summarizes different biomaterial classes that can be used in 3D bioprinters as bioinks to fabricate bone scaffolds, including polymers, bioceramics, and composites. It also describes the advantages and limitations of the three currently used 3D bioprinting technologies: inkjet bioprinting, micro-extrusion, and laserassisted bioprinting. Conclusions: Although 3D bioprinting technology is still in its infancy and requires further development and optimization both in biomaterials and techniques, it offers great promise and potential for facial reconstruction with improved outcome.

• Journal of Adhesion and Interface
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• v.11 no.2
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• pp.41-49
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• 2010

Furan-containing epoxide monomers (8, 9) were designed and synthesized as carbon-neutral, environment-friendly adhesion material. Bicyclic skeleton were constructed using the Diels-Alder reaction of furan and methyl acrylate, both readily accessible starting material from a biomass via bio-refinery process. After reduction of ester functionality, resulting hydroxyl moieties were coupled to epichlorohydrin to provide the epoxy-functionalized furanic monomers (8, 9). The structure of new furanic monomers was confirmed by $^1H$ and $^{13}C$ NMR spectroscopy. As UV-curable monomers, basic properties such as UV curing time and the extent of UV curing were evaluated by photo DSC. Photo-curing shrinkages were measured by linear variable differential transformer transducer (LVDT) and the effect of molecular structure on shrinkage was considered. In addition, new synthetic compounds showed the shear strength over 3 MPa when they were photo-cured between polycarbonate plates, which indicates these compounds are feasible to use as photo-curable adhesive materials.

• Elastomers and Composites
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• v.47 no.1
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• pp.2-8
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• 2012

In this study, in order to develop renewable bio-based nanocomposites, multi-functional nanocomposites from soybean resins (AESO, MAESO) and nanoclay were prepared. Photoelectrodes for environmental friendly dye-sensitized solar cell using soybean resin were also prepared. Organo-modified nanoclay was directly dispersed in functionalized soybean resins after mixing with styrene as a comonomer and radical initiator was used to copolymerize the nanocomposites. The observed morphology was a mixture of intercalated/exfoliated structure and the physical properties were improved by adding nanoclay. A nanocomposite using MAESO, which added COOH functional group to the soybean resin, showed better dispersibility than AESO composites. Ultrasonic treatment of the nanocomposites also improved the physical properties. Nanoporous $TiO_2$ photoelectrode was also prepared using soybean resins as a binder, after acid-treatment of $TiO_2$ surface using nitric acid. Dye-sensitized solar cells were prepared after adsorbing dye molecules on it. The $TiO_2$ photoelectrode prepared using soybean binder had high current density because of increased surface area by improved dispersibility. The photoelectrochemical properties and conversion efficiency of the solar cell were significantly improved using the soybean binder.

• Journal of Adhesion and Interface
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• v.11 no.2
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• pp.50-56
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• 2010

Polyethyleneterephthalate (PET) film is widely used in various industrial fields such as mobile phone, display pannel, notebook etc. Recently PET film attached on indium tin oxide (ITO) surface has a role of high pencil hardness, high refractive index etc. So we synthesized two types of multi-functional monomer which are epoxy modifed acrylate and unmodified acrylate type using recyclable resource like phloroglucinol, derived from trinitrotoluene. We studied the effect of multi-functional monomer's chemical structure on the various properties such as refractive index, optical transmittance, and pencil hardness. We characterized synthesized multi-functional monomer by qualitative analysis through H NMR. We observed that pencil hardness of 1,3,5-triepoxide benzene and 1,3,5-triacrylate benzene they have the range of 2~3 H at high UV dosage of 300 mW. Refractive index appeared the value of 1.54~1.57. Transmittance of all multi-functional monomers has more than 93%.