聚乳酸/改性纤维素纳米晶的热稳定性和结晶性能

Thermal Stability and Crystallization Properties of Polylactide/Modified Cellulose Nanocrystals

采用简单的溶液混合将纤维素纳米晶(CNC)与聚乙二醇(PEG)复合后得到改性的纤维素纳米晶(CNC–PEG)粒子,将其与PLA熔融共混,得到PLA/CNC–PEG纳米复合物。采用热重(TG)分析仪表征了PLA/CNC–PEG纳米复合物的热稳定性,采用示差扫描量热(DSC)仪研究了PLA/CNC–PEG纳米复合物分别在不同升温速率下的非等温结晶行为。结果发现,CNC–PEG中PEG的影响使得PLA/CNC–PEG纳米复合物的热稳定性略高于纯PLA。引入CNC–PEG后,PLA/CNC–PEG(0.5%)纳米复合物的玻璃化转变温度(Tg)比纯PLA高,随着CNC–PEG含量的增加,共混物的Tg又随之降低。PLA/CNC–PEG纳米复合物的结晶温度(Tp)比纯PLA低,且随CNC–PEG含量的增加,共混物的Tp进一步降低。采用Kissinger公式对各样品的非等温结晶过程进行拟合,发现CNC–PEG降低了PLA的结晶活化能,而随CNC–PEG含量的增加,PEG的增塑作用使PLA的结晶活化能升高。

Modified CNC–PEG nanoparticles were obtained by simply solution mixing cellulose nanocrystals(CNC)with polyethylene glycol(PEG).Then,by melt blending them with PLA,PLA/CNC–PEG nanocomposites were obtained.Thermogravimetric analyzer(TG)was used to characterize the thermal stability of PLA/CNC–PEG nanocomposites.Differential scanning calorimetry(DSC)was used to study the non-isothermal crystallization behavior of PLA and different proportional PLA/CNC–PEG nanocomposites at different heating rates.The results show that the thermal stability of PLA/CNC–PEG nanocomposites is slightly higher than that of pure PLA,due to the impact of PEG in CNC–PEG.By the addition of CNC–PEG,the glass transition temperature(Tg)of PLA/CNC–PEG(0.5%)nanocomposite is higher than that of PLA.However,the Tg of the blend decreased with increasing the content of CNC–PEG.The crystallization temperature(Tp)of PLA/CNC–PEG nanocomposites is lower than that of pure PLA,and the Tp of the blends is further decreased with the increase of CNC–PEG content.The Kissinger formula was used to fit the nonisothermal crystallization process of each sample,and it was found that CNC–PEG decreased the crystallization activation energy of PLA,and as the content of CNC–PEG increased,the crystallization activation energy of PLA increased due to the plasticizing effect of PEG.