신소재 cryoprotectant로서 hydroxyethylstarch의 물리적, 열적 특성에 관한 연구 (The) Studies on Physical and Thermal Properties of Hydroxyethylstarch as a New Cryoprotectant원문보기
본 실험은 신소재 cryoprotectant로서 ethyleneoxide 합성비에 따른 HES(hydroxyethylstarch)의 물리적, 열적 특성으로 얼음결정체 재결정화, 점도, DSC를 이용한 호화온도와 수분의 유리전이 온도를 측정하였다. 실험에 사용된 HES는 실험실에서 자체합성한 HES(ethyleneoxide의 합성비, φ= 0.0, 0.25, 0.50, 0.75, 1.00)를 이용하였다. φ=0.50, 0.75, 1.00인 HES를 각각 25, 50, 75, 100 %(w/w)의 농도인 마트릭스를 제조한 후 -8℃에서 얼음결정체 재결정화를 측정하였다. 점도는 각각의 합성비에서 온도변화(10, 20, 30, 40℃)에 따른 겉보기 점도 변화를 측정하였다. 또한 호화온도는 각각의 합성비에서 농도에 따라 10~85℃에서 10℃/min으로 가열시켜 열적변화를 관찰하였다. 유리전이온도는 합성비 φ=0.25인 HES를 ...
본 실험은 신소재 cryoprotectant로서 ethyleneoxide 합성비에 따른 HES(hydroxyethylstarch)의 물리적, 열적 특성으로 얼음결정체 재결정화, 점도, DSC를 이용한 호화온도와 수분의 유리전이 온도를 측정하였다. 실험에 사용된 HES는 실험실에서 자체합성한 HES(ethyleneoxide의 합성비, φ= 0.0, 0.25, 0.50, 0.75, 1.00)를 이용하였다. φ=0.50, 0.75, 1.00인 HES를 각각 25, 50, 75, 100 %(w/w)의 농도인 마트릭스를 제조한 후 -8℃에서 얼음결정체 재결정화를 측정하였다. 점도는 각각의 합성비에서 온도변화(10, 20, 30, 40℃)에 따른 겉보기 점도 변화를 측정하였다. 또한 호화온도는 각각의 합성비에서 농도에 따라 10~85℃에서 10℃/min으로 가열시켜 열적변화를 관찰하였다. 유리전이온도는 합성비 φ=0.25인 HES를 액체질소에 침지시켜 유리상태로 만든후 3℃/min으로 가열시키면서 devitrification 과정을 통한 유리전이온도를 측정하였다 1. HES 마트릭스에서 관찰된 얼음결정체는 저장초기부터 원형 및 타원형을 이루고 있었으며 저장기간에 따라 크기가 증가하였으며 전형적인 재결정화 과정을 관찰할 수 있었다. 본 실험에서는 3가지의 기본 재결정화 기작 중 sintering process가 얼음의 재결정화에 결정적인 역할을 하였다. 2. 얼음결정체 재결정화는 합성비와 농도가 증가함에 따라 지연되는 경향을 보였으나 합성비가 높은 HES의 경우는 농도가 증가함에 따라 오히려 재결정화가 빠르게 진행됨을 관찰할 수 있었다. 3. 얼음의 재결정화과정은 X_(m) = k·t^(n)라는 수학적 모델로 나타낼 수 있었고 속도상수 k는 16.84와 48.87사이에 그리고 시스템 지수 n은 0.1142에서 0.3261사이에 놓여 있었다. 4. 합성비와 온도에 따른 점도 변화는 온도가 증가함에 따라 HES의 점도는 감소하는 경향을 보였으나 합성비에 따른 점도는 각각의 온도에 따라 다른 경향을 나타내었다. φ=0.25인 HES 마트릭스는 고점도를 나타내어 기계적인 측정이 불가능하였고, 유동성 지수 n을 비교할 경우 φ=0.50인 HES 마트릭스는 비뉴턴성 유체로 의사가소성(pseudoplastic)형태를 나타내었고, φ=0.75와 1.00에서는 뉴턴성 유체와 비슷한 형태를 나타냈다. 5. 합성비가 증가함에 따라 HES의 호화온도는 증가하는 경향을 나타내었으나 농도에 따른 변화는 없었다 φ=0.25인 HES(25 %)의 호화개시온도는 37.88℃로 합성비가 증가함에 따라 4~5℃정도 증가함을 알 수 있었다. 6. HES의 첨가는 수분의 유리전이온도를 변화시킨는데 (φ=0.25인 HES 마트릭스(10 %)의 유리전이온도는 -75.46℃로 나타났다. 순수한 물의 유리전이온도(-136℃)와 비교하여 볼 때 약 50℃정도 상승된 것으로 나타났다.
본 실험은 신소재 cryoprotectant로서 ethyleneoxide 합성비에 따른 HES(hydroxyethylstarch)의 물리적, 열적 특성으로 얼음결정체 재결정화, 점도, DSC를 이용한 호화온도와 수분의 유리전이 온도를 측정하였다. 실험에 사용된 HES는 실험실에서 자체합성한 HES(ethyleneoxide의 합성비, φ= 0.0, 0.25, 0.50, 0.75, 1.00)를 이용하였다. φ=0.50, 0.75, 1.00인 HES를 각각 25, 50, 75, 100 %(w/w)의 농도인 마트릭스를 제조한 후 -8℃에서 얼음결정체 재결정화를 측정하였다. 점도는 각각의 합성비에서 온도변화(10, 20, 30, 40℃)에 따른 겉보기 점도 변화를 측정하였다. 또한 호화온도는 각각의 합성비에서 농도에 따라 10~85℃에서 10℃/min으로 가열시켜 열적변화를 관찰하였다. 유리전이온도는 합성비 φ=0.25인 HES를 액체질소에 침지시켜 유리상태로 만든후 3℃/min으로 가열시키면서 devitrification 과정을 통한 유리전이온도를 측정하였다 1. HES 마트릭스에서 관찰된 얼음결정체는 저장초기부터 원형 및 타원형을 이루고 있었으며 저장기간에 따라 크기가 증가하였으며 전형적인 재결정화 과정을 관찰할 수 있었다. 본 실험에서는 3가지의 기본 재결정화 기작 중 sintering process가 얼음의 재결정화에 결정적인 역할을 하였다. 2. 얼음결정체 재결정화는 합성비와 농도가 증가함에 따라 지연되는 경향을 보였으나 합성비가 높은 HES의 경우는 농도가 증가함에 따라 오히려 재결정화가 빠르게 진행됨을 관찰할 수 있었다. 3. 얼음의 재결정화과정은 X_(m) = k·t^(n)라는 수학적 모델로 나타낼 수 있었고 속도상수 k는 16.84와 48.87사이에 그리고 시스템 지수 n은 0.1142에서 0.3261사이에 놓여 있었다. 4. 합성비와 온도에 따른 점도 변화는 온도가 증가함에 따라 HES의 점도는 감소하는 경향을 보였으나 합성비에 따른 점도는 각각의 온도에 따라 다른 경향을 나타내었다. φ=0.25인 HES 마트릭스는 고점도를 나타내어 기계적인 측정이 불가능하였고, 유동성 지수 n을 비교할 경우 φ=0.50인 HES 마트릭스는 비뉴턴성 유체로 의사가소성(pseudoplastic)형태를 나타내었고, φ=0.75와 1.00에서는 뉴턴성 유체와 비슷한 형태를 나타냈다. 5. 합성비가 증가함에 따라 HES의 호화온도는 증가하는 경향을 나타내었으나 농도에 따른 변화는 없었다 φ=0.25인 HES(25 %)의 호화개시온도는 37.88℃로 합성비가 증가함에 따라 4~5℃정도 증가함을 알 수 있었다. 6. HES의 첨가는 수분의 유리전이온도를 변화시킨는데 (φ=0.25인 HES 마트릭스(10 %)의 유리전이온도는 -75.46℃로 나타났다. 순수한 물의 유리전이온도(-136℃)와 비교하여 볼 때 약 50℃정도 상승된 것으로 나타났다.
The objective of this study was to investigate the physical and thermal properties of HES(hydroxyethylstarch) synthesized with ethyleneoxide and starch as a new cryoprotectant. The experiments were carried out with self-synthesized HES(synthesis rate of ethyleneoxide, φ, 0.0, 0.25, 0.50, 0.75 and 1....
The objective of this study was to investigate the physical and thermal properties of HES(hydroxyethylstarch) synthesized with ethyleneoxide and starch as a new cryoprotectant. The experiments were carried out with self-synthesized HES(synthesis rate of ethyleneoxide, φ, 0.0, 0.25, 0.50, 0.75 and 1.00) which was prepared in concentration of 25, 50, 75 and 100 %(w/w, saline solution). The recrystallization of ice, flow behaviour of HES matrices, changes of gelatinization temperature and glass transition temperature were measured. The recrystallizatlon of ice in HES matrices was measured at -8℃ depending on concentration (25, 50, 75, 100 %) and synthesis rate φ (0.50, 0.75, 1.00) in self-developed measuring system. The flow behaviour of all HES matrices was measured by rotational viscometer and the apparent viscosity depending on shear rate at temperature of 10, 20, 30 and 40℃ was estimated. The gelatinization temperature of HES matrices depending on concentration of HES and synthesis rate of ethyleneoxide was scanned with DSC in the temperature range from 10℃ to 85℃ with heating rate of 10℃/min. The glass transition temperature of HES (φ=0.25) was observed through devitrification process with beating rate of 3℃/min after ultra high cooling of HES matrices by liquid nitrogen into glass phase. 1. The crystals of all matrices were of spherical shape already in the initial phase and the recrystallization of ice was observed during storage in all HES matrices. Larger ice crystals increased in size, while smaller ones disappeared to the effect that the total number of crystals decreased. The main driving force into compact round crystals is determined by sintering process of three recrystallization mechanisms observed in frozen state. 2. The recrystallization process of ice in HES matrices was affected by synthesis rate (φ) of ethyleneoxide and concentration of HES. Increasing of φ and concentration delayed the crystal growth slowly. In particular, the recrystallization process of ice in HES matrices which were prepared with higher φ and concentration was more retarded. 3. From the results a mathematical relation, X_(m) = k·t^(n), was derived. A compilation of all experimental data evaluated showed values for t between 16.84 and 48.87 and for n between 0.1142 and 0.3261. 4. As temperature increased, apparent viscosity (η_(ap)) of all HES matrices was decreased. But it was found that there is no relationship between φ and η_(ap) at each temperature. In particular, HES matrices with φ=0.25 showed high viscosity so that it was impossible to measure instrumental in this study. The flow behaviour of HES matrices (φ=0.50) was found to be pseudoplastic as non-Newtonian and HES matrices (φ=0.75 and 1.00) showed Newtonian flow behaviour relating to the flow exponent, n of power equation model. 5. Synthesis rate of ethyleneoxide (φ) affected the change of gelatinization temperature of HES matrices. The higher the synthesis rate of ethylenoxide, the higher the gelatinization temperature increased. But it was observed that the gelatinization temperature was not directly depending on the concentration of HES in all matrices. HES matrices (φ=0.25, 25 %) showed 37.88℃ as gelatinization temperature and increasing of φ affects the elevating the gelatinization temperature of 4~5℃. 6. HES played an important role for the change of glass transition temperature, Tg of water. It was found that Tg of HES matrices (φ=0.25, 10 %) was measured at -75.46℃. It means that Tg is increased to 50℃ in comparing of Tg of pure water, -136℃.
The objective of this study was to investigate the physical and thermal properties of HES(hydroxyethylstarch) synthesized with ethyleneoxide and starch as a new cryoprotectant. The experiments were carried out with self-synthesized HES(synthesis rate of ethyleneoxide, φ, 0.0, 0.25, 0.50, 0.75 and 1.00) which was prepared in concentration of 25, 50, 75 and 100 %(w/w, saline solution). The recrystallization of ice, flow behaviour of HES matrices, changes of gelatinization temperature and glass transition temperature were measured. The recrystallizatlon of ice in HES matrices was measured at -8℃ depending on concentration (25, 50, 75, 100 %) and synthesis rate φ (0.50, 0.75, 1.00) in self-developed measuring system. The flow behaviour of all HES matrices was measured by rotational viscometer and the apparent viscosity depending on shear rate at temperature of 10, 20, 30 and 40℃ was estimated. The gelatinization temperature of HES matrices depending on concentration of HES and synthesis rate of ethyleneoxide was scanned with DSC in the temperature range from 10℃ to 85℃ with heating rate of 10℃/min. The glass transition temperature of HES (φ=0.25) was observed through devitrification process with beating rate of 3℃/min after ultra high cooling of HES matrices by liquid nitrogen into glass phase. 1. The crystals of all matrices were of spherical shape already in the initial phase and the recrystallization of ice was observed during storage in all HES matrices. Larger ice crystals increased in size, while smaller ones disappeared to the effect that the total number of crystals decreased. The main driving force into compact round crystals is determined by sintering process of three recrystallization mechanisms observed in frozen state. 2. The recrystallization process of ice in HES matrices was affected by synthesis rate (φ) of ethyleneoxide and concentration of HES. Increasing of φ and concentration delayed the crystal growth slowly. In particular, the recrystallization process of ice in HES matrices which were prepared with higher φ and concentration was more retarded. 3. From the results a mathematical relation, X_(m) = k·t^(n), was derived. A compilation of all experimental data evaluated showed values for t between 16.84 and 48.87 and for n between 0.1142 and 0.3261. 4. As temperature increased, apparent viscosity (η_(ap)) of all HES matrices was decreased. But it was found that there is no relationship between φ and η_(ap) at each temperature. In particular, HES matrices with φ=0.25 showed high viscosity so that it was impossible to measure instrumental in this study. The flow behaviour of HES matrices (φ=0.50) was found to be pseudoplastic as non-Newtonian and HES matrices (φ=0.75 and 1.00) showed Newtonian flow behaviour relating to the flow exponent, n of power equation model. 5. Synthesis rate of ethyleneoxide (φ) affected the change of gelatinization temperature of HES matrices. The higher the synthesis rate of ethylenoxide, the higher the gelatinization temperature increased. But it was observed that the gelatinization temperature was not directly depending on the concentration of HES in all matrices. HES matrices (φ=0.25, 25 %) showed 37.88℃ as gelatinization temperature and increasing of φ affects the elevating the gelatinization temperature of 4~5℃. 6. HES played an important role for the change of glass transition temperature, Tg of water. It was found that Tg of HES matrices (φ=0.25, 10 %) was measured at -75.46℃. It means that Tg is increased to 50℃ in comparing of Tg of pure water, -136℃.
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