私密直播全婐app免费大渔直播,国产av成人无码免费视频,男女同房做爰全过程高潮,国产精品自产拍在线观看

相關鏈接
聯系方式
  • 通信地址:杭州市浙大路38號浙大玉泉校區第十教學大樓(石化大樓)4111室
  • 郵編:310027
  • 電話:0571-87952631
  • 傳真:0571-87951612
  • Email:wulinbo@zju.edu.cn
當前位置:> 首頁 > 論文著作 > 正文
Synthesis of high molecular weight poly(L-lactic acid) via melt/solid state polycondensation. II. Effect of crystallization on solid state polycondensation
作者:Bo Peng, Hongbin Hou, Fangchao Song, Linbo Wu*.
關鍵字:biodegradable polymers, poly(L-lactic acid)
論文來源:期刊
具體來源:Ind. Eng. Chem. Res. 2012, 51, 5190?5196
發表時間:2012年

To enhance the reaction rate of solid state polycondensation (SSP) of poly(L-lactic acid) (PLLA) and thus to
prepare high molecular weight PLLA by SSP in a short time, the effects of precrystallization as well as SSP temperature (Ts) on
the SSP of PLLA were investigated. It was found that precrystallization at low Tc (70 °C) and then SSP at step-raised Ts could
greatly favor the growth of the molecular weight of PLLA. After precrystallization at 70 °C for 60 min and then SSP at 150−160
°C for 20 h, the product’s weight average molecular weight (Mw) exceeds 200 000 g·mol−1 while its optical purity remained as
high as 90%. The prepolymer precrystallized at 70 °C for 60 min had smaller crystal size and looser packing of lamellae structure
than that at Tcmax (110 °C) and moderate crystallinity of 45%. Such crystal properties may result in enhanced concentration and
mobility of chain-end groups and improved diffusion of byproduct water in an amorphous area, so the SSP reaction is
accelerated. PLLA continues to crystallize during SSP. The crystallinity and melting temperature increase rapidly at the early
stage and slowly at the late stage, implying that the effect of precrystallization on the SSP rate is significant at the early stage, and
weakens gradually at the late stage.

主站蜘蛛池模板: 肥乡县| 长春市| 镇雄县| 鄂尔多斯市| 林州市| 华亭县| 胶南市| 仲巴县| 西乌珠穆沁旗| 自治县| 静乐县| 马鞍山市| 临沂市| 奉节县| 武鸣县| 新田县| 尉氏县| 慈利县| 定结县| 名山县| 丽江市| 渑池县| 闸北区| 青冈县| 馆陶县| 唐海县| 尉犁县| 桑日县| 巴南区| 西丰县| 天镇县| 垣曲县| 大洼县| 天等县| 崇义县| 苍南县| 哈尔滨市| 长乐市| 武定县| 新蔡县| 广灵县|