本研究利用差示掃描熱分析儀(DSC)與溫度調制式差示掃描熱分析(TMDSC)來探討poly(L-lactic acid) (PLLA)的結晶化動力學以及多重熔融行為。
PLLA於溫度範圍85℃~140℃等溫結晶化後，利用Avrami方程式得知PLLA成核與成長方式。PLLA在等溫結晶化溫度130℃以上時成核與成長方式發生改變，和低溫時的成核與成長方式不相同，因Avrami指數(n)在85℃-125℃時為n=2-3和130℃以上時n≦2。而由於Avrami方程式而得知，在105℃左右時，因PLLA的成核速率與成長速率相當，在此時結晶化速率出現最大值。
當在升溫速率為10℃/min與等溫結晶化溫度90℃~120℃時，可以發現有多重熔融峰的出現。利用不同的升溫速率(1℃/min~40℃/min)以及TMDSC來探討PLLA多重熔融峰產生的機制。而由不同升溫速率得知，隨著升溫數率的加快，PLLA多重熔融峰逐漸變為單一熔融峰，因此推測可能是熔融-再結晶-再熔融(melting-recrystallization-remelting)機制所造成的。更進一步的由TMDSC的可逆熱流(reversing heat flow)與不可逆熱流(non-reversing heat flow)顯示，在可逆熱流(reversing heat flow)時只有單一吸熱峰(endothermic peak)，為等溫結晶的熔融峰。而不可逆熱流(non-reversing heat flow)卻發現了一個放熱峰(exothermic peak)與一個吸熱峰(endothermic peak)，分別為再結晶的再結晶峰與再熔融峰。因此確定PLLA多重熔融現象的機制為熔融-再結晶-再熔融(melting-recrystallization-remelting)，且隨著等溫結晶化溫度的升高，熔融-再結晶-再熔融的現象越不明顯。

The crystallization kinetics and multiple melting behaviors of poly (L-lactic acid) (PLLA) were investigated by differential scanning calorimetry (DSC) and temperature-modulated differential scanning calorimetry (TMDSC). Avrami equation was used to find the nucleation and growth mode of PLLA in isothermal crystallization under the temperature range of 85℃ to 140℃. The nucleation and growth mode was changing in isothermal crystallization temperature above 130℃ due to as Avrami exponent (n) in 85℃-125℃ was n=2-3 and above 130℃ was n≦2. Nucleation rate and growth rate was equal and maximum of PLLA crystallization rate was observed at105℃. Moreover PLLA could exhibit multiple melting behaviors, when the heating rate is 10℃/min and at isothermal crystallization temperature range between 90℃ to 120℃ with different heating rates (1℃/min to 40℃/min). In addition to TMDSC was used to discuss the origin of multiple melting behaviors mechanism of PLLA. In the case of higher heating rate, PLLA the multiple melting peaks became to single melting peak. The multiple melting behaviors followed the possible mechanism of melting-recrystallization-remelting. TMDSC results showed reversing heat flow and non-reversing heat flow was observed multiple melting behaviors mechanism of PLLA was melting-recrystallization-remelting. In reversing heat flow there was only one endothermic peak observed, which is originated from melting crystal of isothermal crystallization. Besides in non-reversing heat flow shows one exothermic peak and one endothermic peak. Both exothermic peak and endothermic peaks were originated from recrystallization and melting recrystallization parts respectively. While increasing the isothermal crystallization temperature, the behavior of melting-recrystallization-remelting becomes more inconspicuous.

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