摘要
研究了二氧化硅悬浮体的流变性,在固体含量较少的情况下,体系呈Newton型;固体含量达到一定程度以后,产生三维结构,为假塑性体系,三维结构的固体含量与pH值有关。实验证实,在等电点(i,e,p)附近三维结构最为疏松,还研究了水解聚丙烯酰胺(HPAM)对悬浮体流变性能的影响,HPAM破坏了二氧化硅粒子聚集体结构,呈絮凝体结构,并出现触变性,当高聚物在固体表面覆盖一半时,具有最大触变性和动剪切力,HPAM的水解度达到一定程度,由于对固体粒子由“强”吸附转变为“弱”吸附,固体粒子“屏蔽”了高分子间的相互作用,出现了负触变性现象,在流动时粒子会脱附,静止以后又产生吸附。这种吸附与脱附是产生负触变性的主要原因,HPAM水解过度或用量过多,均会减弱负触变性现象。
The rheological behavior of aqueous silica dispersions was investigated as a function of pH, fraction of silica, etc. A gradual transition from Newtonian to pseudoplastic behavior was observed as the silica content was gradually increased. Plebs of ηPL versus percentage of silica showed a rapid increase in ηPL above a critical silica concentration which was dependent on the pH of the dispersion. These results are explained in terms of the interaction between the silica particles and the size of the units, at pH=4 showed an increase in yield value τ_B reaching a maximum at HPAM concentration corresponding to 0.5 coverage. Thereafter, the yield value decreased with further increase in HPAM coverage. Moreover, the theological results showed extensively hystersis in the shear stress-shear rate curves, indcativo of thixotropy. The results are explained in terms of bridging flocculation and partial reversibility of the flocculated structure. Because of the 'strong' adsorption of the HPAM against solid particles changing into a 'weak' one, solid particles 'shield' the interaction of the polymer molecules, therefore as HPAM increases its hydrolytic degrees, negative thixotropy appears in the system. On the other hand, an excess degree of hydrolysis, or higher concentration of HPAM weakens negative thixotropy.
出处
《化学学报》
SCIE
CAS
CSCD
北大核心
1990年第7期666-672,共7页
Acta Chimica Sinica
基金
国家自然科学基金
