Silkworms have been developed for food and medicinal purposes, and several silkworm products are commercially available. However, there has been no research on their shelf stability. This study investigated the shelf stability of freeze-dried silkworms during storage at various temperature and humidity conditions, using three lipid oxidation indicators: peroxide, acid, and TBA value. The higher the temperature and relative humidity are, the more significant the three lipid oxidation indicators increase. Among these indicators, the TBA and peroxide values show the highest temperature dependence and humidity dependence, respectively. This study could contribute to the standardization of the shelf life of products made from freeze-dried silkworms.
본 연구에서는 가설 강교에 사용되는 조립식 거더-교각 접합부에 대한 새로운 설계를 제안하였다. 새로운 접합부는 모듈의 각 부분을 공장에서 용접하여 제작한 후 현장에서 용접 대신 볼트 접합부를 사용하도록 구성하여 현장에서 모듈을 신속 하게 조립하도록 구성하였다. 이 새롭게 제안된 거더-교각 접합부의 구조적 성능을 평가하기 위해 정적 거동, 연성 성능 및 회 전 성능을 분석하는 실험을 수행하였다, 실험결과 제안된 볼트 접합부는 기존의 용접 체결부에 비해 정적 지지력, 연성 거동 및 회전 성능에서 우수한 성능을 보여주었다. 비록 볼트 체결부의 강성이 용접 체결부보다 다소 작지만, 체결부의 연성 성능이나 정적 지지력에 큰 영향을 미치지 않았으며, 안전성 향상, 빠른 조립 및 분해, 건설 공기 단축 등의 유리한 특성으로 인해 가설 교량 건설에 적합한 것으로 평가되었다.
The TRM method applied in this study is a method aiming at long span and low girder hight of the temporary bridge. When the preload is introduced to the girder member and the preload is removed after by welding the stiffener, a prestress is introduced through the stiffener to increase the load capacity of the member. Therefore, in this study, the structural performance improvement through the application of the TRM method was verified experimentally by the bending tests of the specimens with and without the TRM method.
Acrylic resins (HSCs : EA/EMA/2-HEMA/CLA) which contain 70% solid content were synthesized by the copolymerization of monomers (2-hydroxyethyl methacrylate, ethyl acrylate, and ethyl methacrylate) and functional monomer (caprolactone acrylate : CLA) which improves the crosslinking density and physical properties of films. The physical properties of the prepared acrylic resins (HSCs) containing CLA, are as follows : viscosity 245~515 cps ; Mn 2670~2840 ; and conversions, 83~91%, respectively. From the correlation of Tg values, viscosities, and Mn of the HSCs, it was found that viscosity and Mn increased with Tg value.
An emulsion of octadecamidoethylaminoethyl dodecate (which provides softness) and an emulsion silicone oil KF-96 (which provides lubricity) were separately synthesized. Then PP finishing softeners (SSA-7) was prepared by blending of the synthesized emulsions with beef tallow hardened oil (a softness improving agent). PP finishing treatment was carried out with the prepared SSA-7 and PP finishing resin by a one bath method, and several physical properties were tested. As a result, crease recovery, tear strength, softness, lubricity, and bending resistance were all good, indicating that the prepared SSA-7 is a good PP finishing softener.
Low foaming scouring agents (LSSA) were prepared by blending of amine salt of dodecylbenzene sulfone, poly (PO-b-EO) glycol, Newpol PP-2000, MJU-100, ethylene glycol and organic solvent. As the results of several tests, LSSA-2 showed good scouring effect, penetrating ability and emulsifiability, and showed not much water pollution. The foaming power of LSSA-2 measured by Ross & Miles method was 11mm foam height immediately after foaming. And the foaming power of LSSA-2 measured by Ross & Clark method were less than 310mm foam height at 30℃, 17mm at 80℃. As a result, LSSA-2 was proved as a good foaming scouring agent.
PU flame-retardant coatings (APHD) containing phosphorous were prepared by blending of hexamethylene diisocyanate-trimer, white pigment, dispersing agent, flowing agent, and previously prepared benzoic acid modified polyester (APTB) that contains phosphorous. Physical properties of the prepared APHD were examined. With the introduction of BZA (contained in APTB), the film viscosity and film hardness of APHD decreased. With the introduction of caprolactone group, the flexibility, impact resistance, accelerated weathering resistance of APTBs increased. Flame retardancy of the coatings was tested. In a vertical burning method, APHD shows 210~313 seconds, and in a 45˚ Meckel burner method, shows 1.3~4.0cm2 of char length, which indicates that the coatings are good flame-retardant coatings. Moreover, the amount of afterglow and flame retardancy of the coatings are decreased with increasing BZA content.
Reaction intermediates PCP/BZA (PBI) and tetramethylene bis(orthophosphate) (TBOP) wer synthesized from polycaprolactone (PCP) and benzoic acid (BZA) and from pyrophosphoric acid and 1,4-butanediol, respectively. Benzoic acid modified polyesters containing phosphorus (APTB-5, -10, -15) were synthesized by polycondensation of the prepared PBI (containing 5, 10, 15wt% of benzoic acid), TBOP, adipic acid, and 1,4-butanediol. The structure and characteristics of APTBs were examined using FT-IR, NMR, GPC, and TGA analysis. The increase of the amount of BZA in the synthesis of APTBs resulted in decrease in average molecular weight and kinematic viscosity. From the TGA analysis of APTBs, it was found that the afterglow decreased with the amount of BZA content at the high temperatures.
Alkaline powder cleaning agents (APCAs) were prepared by blending of Na2CO3 tetrasodium pyrophosphate (TSPP). sodium orthosilicate (Na-OSi), Na-dioctyl sulfosuccinate (303C), Demol C, and MJU-100A (100A). The physical properties of APCAs tested with steel specimen showed the following results. The cleaning powers of APCA-6 (Na2CO3 250g/TSPP 70g/Na-OSi 40g/303C 60g/Demol C 50g/100A 30g mixture) for press-rust preventing oil was 97% and 98% degreasing at 2wt%, 70℃ and 90℃, respectively; for Quenching oil, the cleaning power of APCA-6 was 95% degreasing at 2wt% and 70℃. From the results, it was ascertained that APCA-6 exhibited a good cleaning power. Also low foaming power tests proved that the APCA-6 maintained good defoaming effect.
The high-solid coatings were prepared by blending the synthesized acrylic resin in the previous paper and hexamethylene diisocyanate-trimer and curing it at room temperature. The characterization of the films of the prepared coatings was performed. The impact resistance, 60℃ specular gloss, cross-hatch adhension, and heat resistance of the films proved to be good, and the pencil hardness and drying time proved to be slightly poor. Especially, there was a remarkable improvement in the heat resistance. This improvement may stem from the regular arrangement of ethyl groups introduced into the acrylic resin. From a viscoelastic measurement using a rigid-body pendulum, curing was accelerated with the Tg value. With the increase in Tg, log damp value was lowered and dynamic viscoelasic Tg of a cured film was increased.
A copolymer 〈HSAs : EA/EMA/2-HEMA/AAEM) which is an acrylic resin containing 70% solid content was synthesized by the reaction of monomers, including ethyl acrylate, ethyl methacrylate, and 2-hydroxyethyl methacrylate with a functional monomer, such as acetoacetoxyethyl methacrylate, which may give improvements in cross-linking density and physical properties of films. The physical properties of prepared acrylic resins, HSA containing AAEM, are as follows : viscosity, 203~550cps ; Mn, 2590~2850 ; and conversion, 82~89%, respectively. It was found from the plotting of Tg versus viscosity and Tg versus molecular weight that viscosity increased with Tg while number averaged molecular weight decreased with increasing Tg.
To prepare alkaline degreasing agents(SADAs), tetrasodium pyrophosphate(TSPP), Na2CO3, Tetronix T-701 (T-701), Na-dioctyl sulfosuccinate(303C), Demol C, and MJU-100A were blended. The prepared degreasing agents were tested with steel specimens and the results were as follows. The degreasing powers of SADA-6(Na2CO3 50g/TSPP 25g/T-701 10g/303C 15g/Demol C 12g/MJU-100A 8g/water 130g mixture) for press-rust preventing oil were 98% and 99% degreasing at 4wt%, 70 ℃ and 90 ℃, respectively; for quenching oil, the degreasing power of SADA-6 was 92% degreasing at 4wt% and 70 ℃. From these results, it was proved that the SADA-6 exhibits a good degreasing power. Foam heights measured immediately after foaming by Ross & Miles method and Ross & Clark method at 6wt% and 60 ℃ were 16mm and 40mm, respectively. SADA-6 was proved a good low foaming degreasing agent.
한외여과막의 분획분자량을 결정하기 위하여 dead-end형 셀내에 평막을 설치하고 분자량 분포가 수천 내지 수백만의 혼합 dextran 수용액으로 투과 실험하였다. 원료 용액과 투과액을 GPC로 분석하여 각 분자량에 대한 배제율을 구하고 90% 배제율에 해당하는 dextran분자량을 분획분자량를 결정하였다. 투과압력을 0.5에서 2.0 bar까지 증가시킬 경우, Millipore사의 PBTK막은 63,000 내지 68,000 daltons로 10% 이내에서 변화하였지만 Millipore사의 PBQK 막 또는 (주)새한의 UE1812막의 분획분자량은 각각 3.5 및 4.3 배 증가하였다. 또한 투과액을 원료용액의 10내지 40%까지 분리막을 증가시키면서 배제율을 측정한 결과, PBTK의 분획분자량은 25% 증가하였다.
An intermediate, tetramethylene bis (orthophosphate), was prepared by the esterification of pyrophosphoric acid and l,4-butanediol. Then pyrophosphoric-containing modified polyesters (ATTBs) were synthesized by polycondensation of tetramethylene bis(orthophosphate), trimethylolpropane, adipic acid, and l,4-butanediol. The content of l,4-butanediol was varied from 10 to 20wt% for the reaction. The increase of the amount of l,4-butanediol in the synthesis of ATTBs resulted in increase in average molecular weight and decrease in kinematic viscosity owing to the excellent flowability and reactivity of l,4-butanediol.