摘要
以甘油(GL)和聚乙二醇(PEG)为分散介质,研究了低体积分数(φ<8%)的SiO2分散体系的稳态和动态的流变性能,发现体系都具有可逆的剪切变稀和剪切增稠现象.在剪切速率大于临界剪切速率(γi>γic)时,体系具有明显的剪切增稠现象,而当γi<γic,GL体系只有轻微的剪切变稀现象,PEG体系剪切变稀现象却很明显.在动态试验中考察了模量以及损耗角正切tgδ随剪切应力(σ)的变化.在所研究的应力范围内,体系中耗能模量G"都大于储能模量G',tgδ大于1,体系主要表现为粘性.用“粒子簇”生成机理能较好地解释这种剪切变稀和剪切增稠现象,即剪切变稀是由于连续的空间网络结构被破坏,PEG体系剪切变稀现象较GL体系明显应该与PEG高分子链的松弛以及体系中较少的氢键有关;剪切增稠是由于粒子簇的生成引起的.
The rheological behavior of fumed silica dispersions in glycerol (GL) and polyethylene glycol (PEG) have been studied under steady and oscillation shear. The reversible shear-thinning and shear-thickening behaviors have been observed. The two dispersions all show obvious shear-thickening when the shear rate is higher than the critical rate ( γ^·〉γc^·), but when γ^·〉γc^·, the GL system only shows slightly shear-thinning behavior, while the PEG system shows shear-thinning comparatively more obviously. The storage modulus G', loss modulus G" and tg δ have also been studied through oscillation stress shear. The magnitude of G" is larger than that of G' and tg δ〉 1 for both of the systems in the range of stress studied, which shows that the systems mainly possess the viscous properties. Through "clustering" theory, the shear-thinning and the shear-thickening behaviors can be explained. The shear-thinning is due to the breakage of the steric continuous network structure and that the degree of the shear-thinning of the PEG system is larger than the GL system is due to the less number of the hydrogen bonds and the laxation of the PEG chains; the shear-thickening is caused by the formation of the clusters.
出处
《化学学报》
SCIE
CAS
CSCD
北大核心
2006年第15期1543-1547,共5页
Acta Chimica Sinica
关键词
SiO2分散体系
流变性
剪切增稠
机理
silica dispersion
rheological property
shear-thickening
mechanism