Structure and Property Modification of Bimodal Molecular Weight Distribution Polyethylene by Electron Beam Irradiation

Lee, Sang-Man,Jeon, Hye-Jin,Choi, Sun-Woong,Song, Hyun-Hoon,Nho, Young-Chang,Cho, Kyu-Cheol The Polymer Society of Korea 2006 Macromolecular Research Vol.14 No.6

Polyethylene of bimodal molecular weight distribution was irradiated with an electron beam. The thermal and mechanical properties were examined by DSC, small and wide angle X-ray scattering and static tensile test according to the crystal morphology of the irradiated samples. The crystal morphology change upon irradiation, as revealed by wide angle X-ray scattering, correlated well with the changes in melting enthalpy, whereas the lamellar thickness and the amorphous gap thickness remained virtually unchanged at irradiation doses up to 500 kGy. Crosslinks in the crystal domains became evident at an energy level of 250 kGy, resulting in reduced crystallinity and crystal size of the (110) and (200) planes. The samples became stiff and brittle with increased irradiation dose, which seem to be more relevant to the amount of cross links than the crystal morphology changes.

방사선에 의해 제조된 pH 및 온도에 민감한 수화겔의 물성연구 및 약물방출에 관한 연구

김현우,노영창,손태일 한국공업화학회 2003 공업화학 Vol.14 No.3

N-isopropylacrylamide (NIPAAm)와 acrylic acid (AA)를 증류수에 일정한 몰비로 용해한 것과 여기에 butyl acrylate (BA)를 혼합한 용액을 상온에서 30, 50 kGy로 γ-선 조사하여 중합반응과 가교를 동시에 일으켜 pH 및 온도에 민감한 수화겔을 제조하였다. 제조된 수화겔은 pH 2, 7의 용액에서 5~40℃로 온도를 변화시켜 각각의 온도에서 최대 팽윤도를 측정하고 한편으로는 37℃로 고정한 후 PH 2~8까지 pH에 대한 최대 팽윤도를 측정하였다. 수화겔의 팽윤과 수축에 이온강도가 어떤 영향을 미치는지 알아보기 위해 0, 0.01, 0.03 N의 염화나트륨 용액에서 팽윤실험을 하였다. 경구용 인슐린 전달제재를 제조할 목적으로 수화겔이 최대 팽윤할 수 있는 최저의 온도와 pH 조건에서 인슐린을 탑재한 다음 자연건조(air dried)와 동결건조(freeze dried)를 하여 인슐린을 함유한 겔(drug-gels)을 제조하였으며, 인슐린 탑재 후 남은 인슐린 용액으로부터 탑재효율을 구하였다. Drug-gel은 in vitro에서 인공위액(simulated gastric fluid; SGF)과 인공장액(simulated intestinal fluid ; SIF)에서 약물 방출량을 측정하여 방출속도를 측정하였다. Temperature and pH sensitive N-isopropyacrylamide-acrylic acid (NIPAAm-AA) and N-isopropylacrylamide-acrylic acid-butyl acrylate (NIPAAm-AA-BA) hydrogels were synthesized by simultaneous polymerization and crosslinking of NIPAAm AA, and BA monomers in aqueous solution using γ-rays from ^60Co source at room temperature. The measurements of equilibrium water content on the synthesized hydrogels were made at the temperature ranging from 5 to 40℃ and pH 2 and 7. The prepared hydrogels had temperature-sensitive (30~35℃) and pH-sensitive swelling behavior. The HIPAAm-AA and NIPAAm-AA-BA hydrogels were used in drug delivery systems for the controlled release of insulin Insulin has been shown to have binding sites for hydrophobic molecules. Thus, it is likely that insulin binds specifically to the butyl side. The gels including insulin were prepared by air drying or freeze drying after loading insulin in solution (14.1 IU/mL) at 5℃ and pH 7. Drug-gels were plated in simulated gastric fluid (SGF; pH 1.2) at 37℃ for 2 h and then at simulated intestinal fluid (SIF : pH 7.3). The insulin release of the drug-gels was examined by UY analysis.

폐색 혈전혈관염의 특징적인 혈관조영 소견

박상규,최창식,황우철,박충기,노준영 대한혈관외과학회 1992 Vascular Specialist International Vol.8 No.1

The authors wished to introduce detailed angiographjc findings that were reviewed from 11 patients with clinically and pathologically diagnosed as thromboangiitis obliterans(TAO) who were selected young-adult(under the age of 35) male without having history of diabetes mellitus or hyperlipidemia. Total 18 angiograms(16 femoral and 2 brachial) were analized. Follow-up angiographies were performed in 6 patients; 2 times in 5 patients and 3 times in 1 patient. There were 3l occluded arteries and 2 diffusely narrowed arteries. The sites of involvement were posterior tibial arteries in 8 cases, anterior tibial arteries in 6 cases, peroneal arteries in 4 cases, superficial fomoral arteries in 3 cases, popliteal arteries in 3 cases, radial arteries in 3 cases, ulnar arteries in 2 cases, common femorotibial trunk and interosseous arteries in each one case. Eleven arteries were segmentally occluded including one case of multisegmental involvement, and remaining 22 arteries were totally occluded. The shape of interfaces of the occlusion were smooth tapering appearance in 14 arteries, round appearance in 9 arteries, triangular appearance in 4 arteries, nipple shape in 3 arteries. There is no case of rat-tail appear- ance or round filling defect. The opacified arteries before occlusion were mostly normal(in 22 cases), but characteristic signs of corrugate appearance(in 6 cases), wave appearance(in 3 cases) and diffuse narrowing(in 2 cases) were often detected. The corrugate and the wave appearances were nearly symmetrical and constant. There are no case of plaque, calcification or post-stenotic dilatation. Corkscrew appearance of collaterals were observed in 8 cases. They looked as a tree-root or spider-legs. In 3 cases, there was no collaterals at all. In six patients available for follow-up, angiograms revealed gradually bidirectional extension of the occlusions regardless of receiving lumbar sympathectomy or lumbar sympathectomy with bypass graft. Conclusively, TAO is an apparently distinctive disease characterized by progressive and segmental occlusion in small to medium sized arteries with several characteristic signs.

Effect of Electron Beam and ${\gamma}$-Ray Irradiation on the Curing of Epoxy Resin

Kang, Phil-Hyun,Park, Jong-Seok,Nho, Young-Chang The Polymer Society of Korea 2002 Macromolecular Research Vol.10 No.6

The effect of an electron beam and ${\gamma}$-ray irradiation on the curing of epoxy resins was investigated. Diglycidyl ether of bisphenol A (DGEBA) and diglycidyl ether of bisphenol F (DGEBF) as epoxy resin were used. The epoxy resins containing 1.0-3.() wt% of triarylsulphonium hexafluoroantimonate(TASHFA) and triarylsulphonium hexafluorophosphate(TASHFP) as initiator were irradiated under nitrogen at room temperature with different dosage of EB and ${\gamma}$-rays from a Co$^{60}$ u source. The chemical and mechanical characteristics of irradiated epoxy resins were compared after curing of EB and ${\gamma}$-ray irradiation. The thermal properties of cured epoxy were investigated using dynamic mechanical thermal analysis. The chemical structures of cured epoxy were characterized using near infrared spectroscopy. Mechanical properties such as flexural strength, modulus were measured. The gel fraction of DGEBA with ${\gamma}$-ray was higher than that of the epoxy with EB at the same dose. Young's modulus of the sample irradiated by ${\gamma}$-ray is higher than that of sample cured by EB. From the result of strain at yield, it was found that the epoxy cured by ${\gamma}$-ray had a higher stiff property compared with the irradiated by EB.

Biodegradable polycaprolactone/cuttlebone scaffold composite using salt leaching process

박종석,Youn-Mook Lim,Min-Ho Youn,Hui-Jeong Gwon,Young-Chang Nho 한국화학공학회 2012 Korean Journal of Chemical Engineering Vol.29 No.7

We prepared biodegradable polycaprolactone/cuttlebone scaffold composite by salt leaching process. In the first step, a co-continuous blend of biodegradable materials, polycaprolactone (PCL) and cuttlebone (CB), and an amount of sodium chloride salt particles were mixed using a stirrer. Next, the extraction of mineral salts using de-ionized distilled water was performed using a biodegradable PCL/CB scaffold with fully interconnected pores. Finally, the durable morphology of the scaffolds was fabricated by freeze-drying process at −53 oC for 24 hrs in a vacuum. In addition,the quadrilateral pres ranged from about 250 to 300 μm in diameter. Scanning electron microscopy (SEM) and mercury intrusion porosimeter techniques were carried out to characterize the pore morphology. By increasing the CB and sodium chloride salt particle content, the number of interconnected pores, material properties, and pore morphology were dramatically changed. The average compressive strengths (load at 50% strain) of the different porous PCL/CB scaffolds were found to decrease from 133 to about 79 (load at 50% strain, gf) with an increase in porosity. The values of the porosity increased as the sodium chloride salt volume fraction increased

Surface Morphology Control of Polymer Films by Electron Irradiation and Its Application to Superhydrophobic Surfaces

Lee, Eun Je,Jung, Chan-Hee,Hwang, In-Tae,Choi, Jae-Hak,Cho, Sung Oh,Nho, Young-Chang American Chemical Society 2011 ACS APPLIED MATERIALS & INTERFACES Vol.3 No.8

<P>A simple and controllable one-step method to fabricate superhydrophobic surfaces on poly(tetrafluoroethylene) (PTFE) films is developed on the base of electron irradiation. When the thickness of PTFE films is higher than the penetration depth of electron beams, electrical charging occurs at the surface of the films because of the imbalance between the accumulation of incident electrons and the emission of secondary electrons. Local inhomogeneity of charge distribution due to this electrical charging results in the nonuniform decomposition of PTFE molecular bonds. As electron fluence increases, surface morphology and surface roughness of the films are dramatically changed. An extremely rough surface with micrometer-sized pores is produced on the surface of PTFE films by electron irradiation at a fluence higher than 2.5 × 10<SUP>17</SUP> cm<SUP>–2</SUP>.Because of high surface roughness, the irradiated PTFE films exhibit superhydrophobic property with a water contact angle (CA) greater than 150° at fluences ranging from 4 × 10<SUP>17</SUP> to 1 × 10<SUP>18</SUP> cm<SUP>–2</SUP>. The surface morphology and corresponding water CA can be controlled by simply changing the electron fluence. This electron irradiation method can be applicable to the fabrication of superhydrophobic surfaces using other low-surface-energy materials including various fluoropolymers.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/aamick/2011/aamick.2011.3.issue-8/am200464a/production/images/medium/am-2011-00464a_0004.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/am200464a'>ACS Electronic Supporting Info</A></P>

The Effect of Carbon Black on PTC Characteristics of Conductive Polyethylene / Carbon Black Composite

Nho, Young Chang,Kang, Phil Hyun 한국공업화학회 2001 Journal of Industrial and Engineering Chemistry Vol.7 No.4

The effect of the carbon black structure on the PTC(positive temperature coefficient) characteristics of a conductive high density polyethylene/carbon black (HDPE/CB) composite was investigated. The HDPE/CB composite was irradiated with gamma rays to a dosage of 50 kGy, 100 kGy and 150 kGy for the purpose of reducing the NTC (negative temperature coefficient) of the conductive composite. It was found that the PTC intensity depended on the particle size, surface area and loading of the carbon black. The PTC intensity of HDPE/CB increased as the loading and surface area of the carbon black decreased. The electrical reproducibility of HDPE/CB was improved by radiation crosslinking compared with the unirradiated compound. Tlne absence of the NTC effect in the crosslinked CB-filled polymer composites was related to an increase in the viscosity of the polymer matrix, thereby leading to a significant reduction in the mobility of the CB particles in the composites.

Studies on the Effect of γ-Irradiation and Antioxidants on PTC Characteristics of Conductive Carbon Black-Filled Polyethylene Composites

Young Chang Nho,Phil Hyun Kang 한국공업화학회 2003 Journal of Industrial and Engineering Chemistry Vol.9 No.6

Synthesis and Size Control of Ni Nanoparticles Using γ-Irradiation

Young Chang Nho,Hye-Jung Han,Jung-Il Kim,Phil Hyun Kang 한국공업화학회 2004 Journal of Industrial and Engineering Chemistry Vol.10 No.5

Radiation - Induced Graft Copolymerization of Acrylonitrile Containing Acrylic Acid or Glycidyl Metharcrylate onto Polyethylene Films

Nho, Young Chang,Choi, Seong Ho 한국공업화학회 1998 응용화학 Vol.2 No.2

Graft copolymerization of acrylonitrile (AN)/acrylic acid (AA) and acrylonitrile (AN)/glycidyl methacrylate (GMA) onto pre-irradiated polyethylene (PE) films was studied. The effect of reaction conditions such as solvents, additives, and monomer composition on the grafting yields was investigated. The extent of grafting was found to increase with increasing sulfuric acid concentration when sulfuric acid as an additive was added to the grafting solution. In AN/AA and AN/GMA mixture, the proportion of acrylonitrile in the copolymer increased with increasing AN component in feed monomers.