• Nuclear Engineering and Technology
• /
• v.56 no.6
• /
• pp.2153-2162
• /
• 2024

The purpose of this study is to develop a high-energy neutron shielding material applied in proton therapy environment. Composite shielding material consisting of 10.00 wt% boron carbide particles (B₄C), 13.64 wt% surface-modified cross-linked polyethylene (PE), and 76.36 wt% tungsten particles were fabricated by hot-pressure sintering method, where the optimal ratio of the composite is determined by the shielding effect under the neutron field generated in typical proton therapy environment. The results of Differential Scanning Calorimetry measurements (DSC) and tensile experiment show that the composite has good thermal and mechanical properties. In addition, the high energy-neutron shielding performance of the developed material was evaluated using cyclotron proton accelerator with 100 MeV proton. The simulation shows a 99.99% decrease in fast neutron injection after 44 cm shielding, and the experiment result show a 99.70% decrease. Finally, the shielding effect of replacing part of the shielding material of the proton therapy hall with the developed material was simulated, and the results showed that the total neutron injection decreased to 0.99‰ and the neutron dose reduced to 1.10‰ before the enhanced shielding. In summary, the developed material is expected to serve as a shielding enhancement material in the proton therapy environment.

• Polymer(Korea)
• /
• v.29 no.6
• /
• pp.605-612
• /
• 2005

This study investigates the isothermal crystallization behaviors of polypropylene-polyethylene-(1-butene) terpolymer and the adiabatically expanded polyolefin structured foams. For this purpose, butane gas was used as a physical blowing agent. Avrami equation has been used to interpret theoretically the experimental results obtained by either DSC or polarized optical microscope. It is believed that elongation induced crystallization occurring during the adiabatic expansion process has resulted in an increase in crystallization rate, eventually leading to a faster growth rate of spherulites and an increase in the nucleation density. An analysis of the foam by SEM images showed that the structure of foam is uniform (below diameter 30 $\mu$m closed cell) In addition, the thermal conductivity and the compressive strength of the polyolefin structured foams was measured. The thermal conductivity of foamed resin with excellent insulation characteristics is reduced compared with unfoamed resin. The compressive strength is decreased with increase in the expansion ratio.

• Applied Chemistry for Engineering
• /
• v.24 no.3
• /
• pp.305-313
• /
• 2013

In this study, we investigated effects of thermal annealing on the thermal properties and microphase separation behaviors of glycidyl azide-based thermoplastic polyurethane elastomers (ETPE). The GAP-based ETPEs were characterized by attenuated total reflectance-fourier transform infrared spectroscopy (ATR-FTIR), differential scanning calorimeter (DSC), dynamic mechanical analysis (DMA), and gel permeation chromatography (GPC). The effects of annealing temperature conditions ($80{\sim}130^{\circ}C$, 1 h or 24 h) on the properties of the ETPEs were investigated. The intensity of azide group absorption peak of ATR-FTIR spectra and the solubility of ETPE for methylene chloride and dimethylformamide solvent decreased after the annealing at $130^{\circ}C$ for 1 h and at $105^{\circ}C$ for 24 h. With increasing the annealing temperature from $80^{\circ}C$ to $110^{\circ}C$, the high temperature rubbery plateau region of storage modulus curves from DMA thermogram for GAP-based ETPEs was extended to the higher temperature.

• Korean Journal of Materials Research
• /
• v.8 no.11
• /
• pp.1026-1030
• /
• 1998

Thermal properties of Fe- base amorpous alloys were investigated. $Fe_{80}P_6C_{12}B_{12}$ and $Fe_{73}P_{11}C_6B_4AI_4Ge_2$ amorphous alloys were fabricated by melt spinning method and thermal analysis was done by differential scanning calorimeter. After isothermal crystallization. the Avrami exponents of $Fe_{80}P_6C_{12}B_{12}$ and $Fe_{73}P_{11}C_6B_4AI_4Ge_2$ amorphous alloys were 1.8-2.2 and 2.5-4.0, respectively. It means the former alloy shows diffusion controlled growth and the latter one shows interface controlled growth. For $Fe_{80}P_6C_{12}B_{12}$ and $Fe_{73}P_{11}C_6B_4AI_4Ge_2$ amorphous alloys. the activation energies of isothermal crystallization was 353 and 371kJlmol. Also the activation energies of nucleation and growth were 301, 324kJlmol and 273. 30lkJ/mol, respectively. Thus $Fe_{73}P_{11}C_6B_4AI_4Ge_2$ amorphous alloy is considered to be more stable than $Fe_{73}P_{11}C_6B_4AI_4Ge_2$ amorphous alloy.

• Journal of the Korean Institute of Gas
• /
• v.2 no.1
• /
• pp.59-65
• /
• 1998

Morphology and thermal properties of polyurethane synthesized from 4,4'-diphenylmethane diisocyanate (MDI), polyester polyol, and 1,4-butane diol are investigated using fourier transform infrared spectroscopy (FT-IR), differential scanning calorimeter (DSC), and dynamic mechanical thermal analysis (DMTA). From the FT-IR study, it is found that the stretching peaks of hydrogen bonded N-H and C=O are shifted to the low frequencies with the increase of hard segment content of the polyurethanes. The shift of the stretching peaks of hydrogen bonded N-H and C=O indicates that the degree of hydrogen bonding is increased. From the DSC study, it appears that the glass transition temperature ($T_g$) of the polyurethanes is increased with the increase of the hard segment content. Also, it is found that the polyurethanes investigated in this study have the homogeneous network structure due to the high functionality of the MDI. From the DMTA study, transition of the soft segment was not found. Therefore it is concluded that the polyurethanes investigated in this study have the one-phase morphology which is consistent with the DSC results.

• Korean Chemical Engineering Research
• /
• v.51 no.1
• /
• pp.111-115
• /
• 2013

The optimum synthetic conditions of poly(p-phenylphenol) by horseradish peroxidase in dioxane:water (80:20 v/v) mixtures were studied. The stability against thermal degradation and structural properties of the synthesized phenolic resins were investigated by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC), respectively. The synthetic yield of poly(p-phenylphenol) increased upon the increase of the amount of enzyme up to 0.25 mg HRP/mL, then leveled off for further increase of the enzyme usage. When sodium acetate (100 mM, pH 4~6) and sodium phosphate (100 mM, pH 7~9) were used as the buffering salts for the aqueous component (20% v/v), the synthetic yield of the resin increased at higher pH of the aqueous buffer. But when the pHs of the aqueous buffer were 6 and 9, the synthetic yield strongly depended on the types of the buffering salts; if sodium phosphate was used instead of sodium acetate at pH 6, the yield decreased by about 15% and if sodium bicarbonate was used instead of sodium phosphate, the yield decreased by almost 20%. When the pH range of the aqueous buffer was from 4 to 7, the addition of a radical mediator, 2,2'-azinobis (3-ethylbenzothiazoline-6-sulfonate) (ABTS), up to 2 mM improved the synthetic yield of the resin by about 10%. TGA experiments revealed that the thermal stability of the resin synthesized in dioxane:water (100 mM sodium phosphate, pH 9) (80:20 v/v) was high having the char yield of 47% upon the heating at $800^{\circ}C$. DCS results showed that the structures of the polymers synthesized in acidic aqueous buffers were different from those of the polymers synthesized in the basic aqueous buffers. However, all the synthesized resins were found to have the property of the thermosetting resins.

• Polymer(Korea)
• /
• v.38 no.4
• /
• pp.510-517
• /
• 2014

A series of polyimide (PI) was prepared by reacting 4,4'-(hexafluoroisopropylidene)-diphthalic anhydride (6FDA) as the anhydride and bis(3-aminophenyl) sulfone (APS), bis[4-(3-aminophenoxy)-phenyl] sulfone (BAPS), 2,2-bis(4-aminophenyl)-hexafluoropropane (6FPD), 2,2-bis[4-(4-aminophenoxy)-phenyl]hexafluoropropane (6FBAPP), 2,2'-bis(trifluoromethyl)benzidine (TFDB), or 1,4-phenylenediamine (PDA) as the diamine. Residual stress behaviors were detected in-situ during thermal imidization of the polyimide precursors using a thin film stress analyzer (TFSA), and interpreted with respect to their morphology. According to the molecular orientation and packing order, the residual stress varied from 23.1 to 12.5 MPa, decreased with increasing chain rigidity. The thermal properties of the PI films were investigated using differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and thermomechanical analysis (TMA). Their optical properties were measured by ultraviolet-visible spectrophotometer (UV-vis), and spectrophotometry. The properties of PI films were found to be strongly dependent upon the morphological structure. However, trade-offs between residual stress and optical properties were identified.

• Journal of the Korean Wood Science and Technology
• /
• v.44 no.3
• /
• pp.406-414
• /
• 2016

The lignin-based carbon nanofiber reinforced epoxy composite has been prepared by immersing carbon nanofiber mat in epoxy resin solution in order to evaluate the physical and mechanical properties. The thermal and mechanical properties of the carbon nanofiber reinforced epoxy composite were analyzed using thermogravimetric analysis (TGA), differential scanning calorimeter (DSC) and tensile tester. It was found that the thermal properties of the carbon nanofiber reinforced epoxy composite improved, with its glass-transition temperature ($T_g$) increased from $90.7^{\circ}C$ ($T_g$ of epoxy resin itself) to $106.9^{\circ}C$. The tensile strengths of carbon nanofiber mats made from both lignin-g-PAN copolymer and PAN were 7.2 MPa and 9.4 MPa, respectively. The resulting tensile strength of lignin-based carbon nanofiber reinforced epoxy composite became 43.0 MPa, the six times higher than that of lignin-based carbon nanofiber mats. The carbon nanofibers were pulled out after the tensile test of the carbon nanofiber reinforced epoxy composite due to high tensile strength (478.8 MPa) of an individual carbon nanofiber itself as well as low interfacial adhesion between fibers and matrices, confirmed by the SEM analysis.

• Applied Chemistry for Engineering
• /
• v.18 no.1
• /
• pp.77-83
• /
• 2007

It is essential that second order nonlinear optical materials have low optical propagation losses in the wavelengths of second harmonic generation for practical applications in waveguides. Three dipolar chromophores substituted with nitro, cyano, and alkyl sulfone as an electron withdrawing group were prepared. The UV-Vis absorption spectra of the cyano and alkylsulfone chromophores showed a blue-shift compared to the nitro chromophore. The introduction of oxadiazole segment in the chromophore structure led to similar spectral shift. The blue-shift can produce low optical loses at second harmonics. The chromophores were successfully attached to a polyimide, yielding side chain polymers. The nonlinear optical property of the prepared optical polymers was determined by measuring electro-optic coefficient at 1.55 mm. The polymers exhibited high glass transition temperature of over $185^{\circ}C$ and thermal stability to $300^{\circ}C$ through differential scanning calorimeter analysis and thermal gravimetric analysis.

• Elastomers and Composites
• /
• v.44 no.2
• /
• pp.164-174
• /
• 2009

PA66/EPDM/PP-g-MA and PA66/EPDM-g-MA/PP-g-MA composites were manufactured by a modular intermeshing twin screw extruder for enhanced low temperature impact resistance with different content of PP-g-MA. The results showed that composite containing 90 wt% of PA66, 8 wt% of EPDM-g-MA, and 2 wt% of PP-g-MA has a optimum value in the thermal and mechanical properties. The characteristics of the composites were analyzed by TGA, DSC, and SEM. From above results, we established that the low interfacial strength and the impact resistance at low temperature shown in a pre-existing PP/EPDM composite were enhanced by grafting with compatibilizer such as maleic anhydride. These results show the possibility of local manufacturing process and cost down with optimum screw configuration for best mixing quality in the twin screw extruder.