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폴리비닐아세테이트 Sub-microparticle의 제조 및 특성해석
김한도,Ghim, Han-Do 한국섬유공학회 2005 한국섬유공학회지 Vol.42 No.3
Nano-sized poly(vinyl acetate) (PVAc) particles were prepared by emulsification-and-diffusion method. Influences of process variables on the mean particle size of resulting sub-microparticles have been evaluated. It wasclarified that the type and concentration of stabilizer, homogenizer speed, and polymer concentration determined the size of PVAc sub-microparticles. Especially when didodecyl dimethyl ammonium bromide and propylene carbonatewere used as stabilizer and solvent, respectively. PVAc sub-microparticles smaller than 200 nm were obtained.
Lim, Hyun-Ju,Ghim, Han-Do,Choi, Jin-Hyun,Chung, Ho-Yun,Lim, Jeong-Ok 한국고분자학회 2010 Macromolecular Research Vol.18 No.8
A new controlled release system is proposed for bone morphogenetic proteins (BMP)-induced osteoblastic growth and differentiation of the human bone marrow stromal cells (hBMSCs) using injectable nanohydrogels. Alginate nanohydrogels (ANH) containing BMP-2 (BMP-2@ANH) were prepared using a reverse emulsificationdiffusion technique. The mean particle diameter of the BMP-2@ANH measured by dynamic light scattering was 520 nm. The proliferation of hBMSCs was promoted with the BMP-2@ANH. The controlled release of BMP-2 from the BMP-2@ANH enhanced the differentiation of hBMSCs into osteoblasts, which was confirmed by RT-PCR and alkaline phosphate activity. With the BMP-2@ANH, calcification and phosphate deposits on the cells were confirmed by alizarin red-S staining and von-kossa staining, respectively, showing that the differentiation of hBMSCs into osteoblasts was activated by the BMP-2 released from the BMP-2@ANH. Growth factor delivery using a nanohydrogel is a potential method for facilitating the differentiation of stem cells in vivo.
Yeum, Jeong-Hyun,Ghim, Han-Do,Deng, Yulin The Korean Fiber Society 2005 Fibers and polymers Vol.6 No.4
In order to prepare high molecular weight poly(methyl methacrylate) (PMMA)/silver nanocomposite microspheres, methyl methacrylate was suspension-polymerized in the presence of silver nanoparticles at low temperature with 2,2'-azobis(2,4-dimethylvaleronitrile) as an initiator. The rate of conversion was increased by increasing the initiator concentration. When silver nanoparticles were added, the rate of polymerization decreased slightly. High monomer conversion (about $85\%$) was obtained in spite of low polymerization temperature of $30^{\circ}C$. Under controlled conditions, PMMA/silver microspheres with various number-average degrees of polymerization (6,000-37,000) were prepared. Morphology studies revealed that except for normal suspension microspheres with a smooth surface, a golf ball-like appearance of the microspheres was observed, due to the migration and aggregation of the hydrophilic silver nanoparticles at the sublayer beneath the microsphere's surface.
Preparation and Characterization of Flame Retardant High Impact Polystyrene
Minkwan Kim(김민관),Mi Jung Lee(이미정),Han Do Ghim(김한도) 한국고분자학회 2017 폴리머 Vol.41 No.1
난연성 고충격 폴리스티렌(HIPS)의 합성을 위하여 라디칼계 부가반응을 통해 트리페닐포스페이트(TPP)를 그래프트하였다. FTIR과 <SUP>1</SUP>H NMR 분석을 통하여 TPP의 부가반응이 성공적으로 이루어졌음과 HIPS를 구성하는 폴리부타디엔(PB)의 이중결합이 감소하였음을 확인하였다. 또한 TPP의 부가에 따른 이중결합의 감소는 Izod 충격강도의 감소를 통해 확인하였다. 그래프트된 TPP가 TPP@HIPS의 비결정영역에 존재하고 있음은 <SUP>31</SUP>P NMR 분석을 통해 확인하였다. TGA 분석의 잔존 char yield로부터 TPP@HIPS의 열안정성이 향상되었음을 유추할 수 있었다. TPP@HIPS의 잔존 char yield는 600 ℃ 이상에서 16.65 wt%를 보였으며, 미처리 HIPS(pHIPS)의 경우에는 잔존하는 char가 존재하지 않았다. 한계산소지수(LOI) 수치는 pHIPS와 TPP@HIPS에 있어 유의미한 차이를 나타내지 않았으나, UL94 수직시험법을 통해 TPP@HIPS가 V-1 등급의 우수한 난연성을 나타냄을 확인하였다. A triphenyl phosphate (TPP) graft high impact polystyrene (HIPS) (TPP@HIPS) is synthesized to prepare flame retarding HIPS via radical addition reaction of TPP. From FTIR and <SUP>1</SUP>H NMR analyses, successful addition reaction of the TPP and decreases of the amount of double bond of polybutadiene parts in HIPS were confirmed. Reduction of the amount of double bond by addition of TPP can also be confirmed through comparison of Izod impact strength values. From <SUP>31</SUP>P NMR characterization, it can be supposed that the TPP exists as amorphous phase in TPP@HIPS. Thermal stability of the TPP@HIPS is improved, which is deduced by increasing residual char yield observed from TGA analyses. Residual char content of the TPP@HIPS at over 600 ℃ was 16.65 wt%, whereas there was no residue for pure HIPS (pHIPS). There are not significant differences in limited oxygen index (LOI) values of pHIPS and TPP@HIPS. However, the TPP@HIPS showed superior flame retardancy of V-1 rating in UL94 vertical test.