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허탁 건국대학교 1994 學術誌 Vol.38 No.2
A crosslinked polyurethane was ground and introduced into the same crosslinked polyurethane matrix as a filler with the variables of size, content, and swelling time in order to investigate the mechanical properties of polyurethane / polyurethane composites. The increase of the filler size decreased the mechanical properties of the composites such as tensile strength, elongation at break, and impact strength. The increase of the filler content from 0 to 20 wt% also deteriorated the properties of the composites. Even though the filler and the matrix showed good adhesion and compatibility (because they are virtually the same), poor mechanical properties was obtained. It may be due to the decrease of the modulus and the interference of the hard-segment phase formation when the filler was incorporated into the matrix. The effect of the swelling time of the polyurethane filler in the presence of poly(propylene glycol), PPG, and trimethylol propane, TMP, was expected to improve the mechanical properties because of the possible interpenetration of PPG and TMP at the filler-matrix interface. However, the decrease of the resulting properties from the increase of the swelling time with 0, 1, 3, 7, 15 days indicates that there was no significant interfacial interpenetration. Instead. the Increase of the swelling time brought about the defects in the network structures and hard-segment phase formation in the polyurethane matrix.
허탁,곽종명 한국공업화학회 2000 응용화학 Vol.4 No.1
In general, petrochemical industries are composed of very complex systems with internally recurring unit processes where the upstream input of a unit process may include the downstream output of the same unit process. Therefore, it is rather difficult to identify and quantify the inputs/outputs for those internally recurring unit processes, respectively. In this study, an objective and consistent calculation method which is applicable to complex systems with internally recurring unit processes are proposed to determine the inputs/outputs associated with each unit process by using simultaneous equations. In this case, unit processes linked another one are considered as variables and materials flows are considered as constants. The LCI results from the above methodology will be analyzed and compared using hypothetical examples.
허탁,안중우,정재우 한국공업화학회 1997 응용화학 Vol.1 No.2
Life Cycle Assessment(LCA) is a technique for assessing the environmental aspects and potential impacts associated with a product system, by compiling an inventory of relevant inputs and outputs of a product system from cradle to grave. But there are many unsolved problems. Open loop allocation is one of those problems. In this study, a solution for open loop allocation method is proposed and applied to expanded polystyrene wastes management system.
고무 탄성 이론을 이용한 가교 폴리우레탄의 특성에 관한 연구
허탁 건국대학교 1993 學術誌 Vol.37 No.2
Network formation (branching) theory was used to examine the relations between network structures and their properties. A series of model polyurethane(PU) networks based on poly(oxypropylene glycol), trimethylol propane, and dipheyl methane 4,4'-diisocyanate were prepared and analyzed by EANCs (Elastically Active Network Chains) theory and swelling experiment. The contribution of physical crosslinks to the total crosslinks was found to increase with increasing chemical crosslinks. In addition, with the same chemical crosslinking densities. the effect of physical crosslinks was more significant when the ratio of OH groups belonging to branch units to the total number of OH groups in the mixture (ρ) was larger. Tensile strengths increased with increasing the concentration of EANCs. While elongations at break did not show any trend, the fraction of elastic deformation decreased with increasing the concentration of EANCs. Galss transition temperatures increased with increasing not only the concentration of EANCs but also ρ.