• Biomaterials Research
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• v.22 no.4
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• pp.235-248
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• 2018

Background: Injectable hydrogels have been extensively researched for the use as scaffolds or as carriers of therapeutic agents such as drugs, cells, proteins, and bioactive molecules in the treatment of diseases and cancers and the repair and regeneration of tissues. It is because they have the injectability with minimal invasiveness and usability for irregularly shaped sites, in addition to typical advantages of conventional hydrogels such as biocompatibility, permeability to oxygen and nutrient, properties similar to the characteristics of the native extracellular matrix, and porous structure allowing therapeutic agents to be loaded. Main body: In this article, recent studies of injectable hydrogel systems applicable for therapeutic agent delivery, disease/cancer therapy, and tissue engineering have reviewed in terms of the various factors physically and chemically contributing to sol-gel transition via which gels have been formed. The various factors are as follows: several different non-covalent interactions resulting in physical crosslinking (the electrostatic interactions (e.g., the ionic and hydrogen bonds), hydrophobic interactions, ${\pi}$-interactions, and van der Waals forces), in-situ chemical reactions inducing chemical crosslinking (the Diels Alder click reactions, Michael reactions, Schiff base reactions, or enzyme-or photo-mediated reactions), and external stimuli (temperatures, pHs, lights, electric/magnetic fields, ultrasounds, or biomolecular species (e.g., enzyme)). Finally, their applications with accompanying therapeutic agents and notable properties used were reviewed as well. Conclusion: Injectable hydrogels, of which network morphology and properties could be tuned, have shown to control the load and release of therapeutic agents, consequently producing significant therapeutic efficacy. Accordingly, they are believed to be successful and promising biomaterials as scaffolds and carriers of therapeutic agents for disease and cancer therapy and tissue engineering.

• Textile Coloration and Finishing
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• v.35 no.1
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• pp.8-19
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• 2023

Silicone rubber is widely used in most industries due to diverse advantages like heat stability, UV stability, durability, chemical resistance, environment friendliness, inertness and so on. But there is limitation to expand applications due to relatively weak rubber strengths such as tensile strength and tear strength, especially in fabric coating applications. The purpose of this study is to find influence of coating agent on performances of rubber and coated fabrics and their correlation according to different crosslinking densities of silicone rubbers. Addition cure type of silicones were formulated using crosslinked MQ-type silicone resin consisting of M (R₃SiO_1/2) and Q (SiO_4/2) and linear polymers. Raw materials used were; 1) linear vinyl endblocked polymers and vinyl functional MQ resin as main polymers, 2) linear silicone hydride polymers as crosslinkers, 3) platinum catalyst and 4) inhibitor to control curing speed. Rubber specimens were prepared to check mechanical strength using universal testing machine (UTM). Crosslinking density was calculated using Flory-Rhener equation using solvent swelling method. Differential scanning calorimetry (DSC) and scanning electron microscope (SEM-EDS) were used to characterize rubbers. Consequently, it was found that physical properties of silicone rubbers and coated fabrics can be expected by crosslinking density of rubbers. Silicone rubber formulations that contain 20 ~ 30 wt% of vinyl MQ resin showed strongest balanced performances.

• Applied Chemistry for Engineering
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• v.5 no.5
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• pp.772-778
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• 1994

The pervaporation separation experiments of phenol-water mixtures were carried out by using Type 1 (PDMS : crosslinking agent= 1 : 0.25) and Type 2 (PDMS : crosslinking agent= 1 : 0.35) silicone rubber membranes at 30, 40 and $50^{\circ}C$. The phenol concentrations in the feed to be separated were 500 ppm to 5 wt%. Type 2 membranes were more efficient than Type 1 membranes for the separation of phenol-water mixtures. The phenol concentration of 70wt% was obtained for 5wt% of phenol concentration in the feed at $30^{\circ}C$ and 11wt% phenol concentration observed for 500ppm of phenol concentration in the feed at $30^{\circ}C$ by using Type 2 membranes.

• Elastomers and Composites
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• v.46 no.4
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• pp.318-323
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• 2011

To recycle the waste tire rubber powder, rubber powder composite for waterproof sheet was prepared, and analyzed the effect of the kind of resin and the amount of crosslinking agent on the mechanical property of the composites. The elongation-at-break of the PE composite increased more than 3 times as EPDM was added into rubber composites. As the content of the crosslinking agent increased, the tensile strength of composite increased as well. When recycled polypropylene was used, the increase in composite's tensile strength was more than 3 times. Therefore to use the recycled PP in composite is more effective rather than PP in term mechanical properties.

• Applied Chemistry for Engineering
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• v.7 no.4
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• pp.777-786
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• 1996

Uniform sized-porous poly(acrylonitrile-ethylene glycol dimethacrylate) (PAN) microgels were synthesized by seed polymerization using monodisperse polystyrene seed particles. The effect of weight ratios of monomer/seed (M/S) and diluent/monomer (DIM), concentration of crosslinking agent and the type of diluent was investigated on the formation of PAN microgels. The particle size distribution of PAN microgels was found to be monodisperse in that the weight ratio of M/S is less than 50. More porous microgels were formed and the interstices between small sized interior microspheres present inside of PAN microgels were also smaller with increasing crosslinking agent concentration. Well-developed pore structure was found to be in that weight ratio of D/M is 1 and toluene is used as a diluent.

• Korean Chemical Engineering Research
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• v.52 no.1
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• pp.63-67
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• 2014

The effects of reactant composition on the particle size distribution, synthetic yield, and density of Phenol-formaldehyde bead were examined in the synthesis of resol-type phenolic resin. Decrease of the content of DI water as dispersion media can increase the viscosity of suspension, which may cause the difference of particle size distribution and aggregation. The average particle size of synthesized beads was also decreased with the increasing content of stabilizer which can affect the interfacial area. The amount of crosslinking agent showed no effect on the size distribution and synthetic yield, but it made a decrease in the density of synthesized bead due to the macropore in the bead.

• Journal of Technologic Dentistry
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• v.35 no.4
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• pp.313-320
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• 2013

Purpose: The purpose of this study was to know the physical properties of UDMA dental composite resins containing two photosensitizers, PD, DA, as a photosensitizer instead of CQ. We want to know Remaining Double Bond(RDB) of UDMA unfilled resin and diametral tensile strength and flexural strength of composite resin containing PD and DA were compared with those of CQ, most widely used photosensitizer for dental composite resins. Methods: The RDB of UDMA studied by FT-IR spectroscopy increased with irradiation time. The composite resins were tested for their physical properties. The dental composite resins were made with UDMA as a monomer, silanized silica as filler, N,N-dimethylaminoethyl methacrylate (DAEM) as amine initiator, and one of the two kinds of new photosensitizers. Results: The relative RDB of UDMA was in the order: DA > CQ > PD but the physical properties of the composite resins show PD and DA with higher results compared with that containing CQ. The reason for the results is that PD and DA serve not only as a photosensitizer but also as a photo-crosslinking agent. Conclusion: PD and DA show as effective photosensizers, suitable for UDMA dental composite resin compare with a higher efficiency than CQ.

• Macromolecular Research
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• v.17 no.8
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• pp.580-584
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• 2009

The effects of crystallinity and radiation crosslinking on the physical properties of a microporous high density polyethylene (HDPE) film with Millad3988 as a nucleating agent were investigated. The pores of the HDPE film were affected by the crystallinity. The crystallinity of the HDPE films increased with increasing Millad3988 amount up to 0.1 wt% but decreased with further addition. The mechanical characteristics of the HDPE containing Millad3988 films improved with increasing irradiation dose up to 50 kGy, but decreased at 75 kGy due to severe degradation. The thermal shrinkage behavior of the HDPE films decreased with increasing radiation dose up to 50 kGy. The porosity of the stretched HDPEIMillad3988 films after ${\gamma}$-ray radiation increased with increasing y-ray radiation dose up to 50 kGy. The pores of the irradiated films were formed more easily by a stretching due to the formation of a crosslinked structure.

• Proceedings of the KSME Conference
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• 2001.11a
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• pp.853-858
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• 2001

Generally, mixed materials of LDPE, EVA and foaming agent are manufactured by crosslinking foaming or chemical foaming process. Above materials were used in a microcellular foaming injection molding process. Influence of each factor such as injection type, temperature of barrel, rate of mixed materials and contents of foaming agent was estimated by DOE(Design of Experiments). As a result of experiments, injection type and rate of LDPE, EVA have an influence on foaming rate. This data can be used in field of application of LDPE and EVA.

• Korean Chemical Engineering Research
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• v.49 no.1
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• pp.69-74
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• 2011

In this study, it was prepared for nanofiber with high impact polystyrene(HIPS). HIPS is able to crosslinking after electrospinning with crosslinking agent and it could overcome brittle characteristics of polystyrene(PS). After thermal crosslinking, HIPS nanofiber was sulfonated by sulfuric acid. It was investigated FT-IR, XPS, water uptake, ion exchange capacity(IEC), SEM, and contact angle. According to the result of FT-IR and XPS, it was increased due to introduce the hydrophilic group($SO_3H$) in the HIPS nanofiber. The highest water uptake and IEC were 75.6%, 2.67 meq/ g at 120 min sulfonation time with 7.5 wt% DVB.