摘要
在高分子材料中引入纳米颗粒不仅能够影响材料的机械性能,而且能显著改变材料加工过程中的流变性能。尤其对于高分子共混物,纳米颗粒还能够引起混合物相结构的改变。我们按照不同的质量百分比将未经处理的纳米二氧化硅(SiO_2)颗粒通过熔融共混的方法引入到相容的PLA/PMMA 50/50的共混物中。研究发现随着二氧化硅颗粒的加入,不仅共混物的玻璃化转变温度得到提高,而且其玻璃化转变区间也变大。扫描电镜(SEM)结果显示SiO_2增强的PLA/PMMA混合物的界面存在明显的"坑状"结构。根据对PLA/SiO_2,PMMA/SiO_2以及PLA/PMMA/SiO_2三种纳米复合材料的SEM和流变学实验结果的综合分析,我们认为PLA分子链能够选择性吸附在纳米二氧化硅颗粒周围,引起PLA/PMMA混合物在纳米尺度的局部非均质分布。此外,流变实验表明纳米二氧化硅的引入提高了PLA/PMMA共混物在熔融状态下的粘弹性以及相稳定性,并且提高了共混物中的链缠结点密度。
The effects of nanosilica on the thermo-mechanical and rheological properties of PLA/PMMA 50/50 blends were investigated.It is found that the incorporation of nanosilica does not only increase the glass transition temperature but also extend the broadness of glass transition,attributing to local nanoscale heterogeneities in the miscible blends induced by the self-concentration of the components.According to the results of SEM and rheological measurements,it was proposed that PLA molecules were selectively adsorbed on the surface of nanosilica,and the preferential adsorption of PLA changed the blend composition in the "crater" structure and the bulk matrix.The phase separation temperature of the filled PLA/PMMA blends was also improved by the incorporation of nanosilica,implying a potential role of nanosilica in improving the phase stability of PLA/PMMA blends.In addition,nanosilica could increase the viscoelasticity and entanglement density of PLA/PMMA blends.
引文
[1]Xiaoqiong Hao,Joachim Kaschta,Xianhu Liu,Yamin Pan,Dirk W.Schubert.Polymer,2016,82(15):57-65
[2]Xiaoqiong Hao,Joachim Kaschta,Xianhu Liu,Dirk W.Schubert.Polymer,2015,80(2):38-45