Comb polymer architecture effects on the rheological property evolution of concentrated cement suspensions
Comb polymer architecture effects on the rheological property evolution of concentrated cement suspensions
复制标题
DOI：
10.1111/j.1551-2916.2004.01643.x
复制
发表时间：
2004-09-01
影响因子：
3.9
通讯作者：
Lewis, JA
中科院分区：
文献类型：
--
作者：
Kirby, GH;Lewis, JA
我们研究了在不存在和存在梳形聚合物的情况下，由聚丙烯酸（PAA）的骨干和电荷中性，聚（环氧乙烷）（PEO）的牙齿的浓缩水泥悬浮液的流变行为。这些物种具有均匀的主链分子量和接枝密度，具有不同的齿分子量。PAA（线性聚合物）和PAA/PEO梳形聚合物均赋予高于临界重量分数w* 为4 mg/（g水泥）的浓缩水泥悬浮液初始稳定性。然而，水泥-PAA悬浮液过早凝固。它们的快速，不可逆的硬化源于PAA和溶液中的多价反离子之间的有害相互作用。有趣的是，存在的PEO齿组成的长度只有几个单体单元减轻这种相互作用。浓缩的水泥-PAA/PEO悬浮液的流变性能的演变表现出复杂的行为，从可逆的凝胶状反应，观察到在短齿长度的显着的凝胶到流体的转变，在减速期间观察到的系统组成的较长的PEO齿。在较长的水化时间下，所有水泥-PAA/PEO悬浮液在加速期开始之前表现出类似于exp（t/tau（c））的初始弹性模量值G（i）'，随后是初始凝固。他们的特征水合时间，τ（c），和设置时间强烈依赖于“自由”的羧酸基团[COO-]的浓度所产生的非吸附在溶液中的水化物种。
We have studied the rheological behavior of concentrated cement suspensions in the absence and presence of comb polymers comprised of a polyacrylic acid (PAA) backbone and charge-neutral, poly(ethylene oxide) (PEO) teeth. These species possessed a uniform backbone molecular weight and graft density, with varying teeth molecular weight. Both PAA, a linear polyelectrolyte, and PAA/PEO comb polymers imparted initial stability to concentrated cement suspensions above a critical weight fraction, w* of 4 mg/(g of cement). Cement-PAA suspensions, however, set prematurely. Their rapid, irreversible stiffening stemmed from deleterious interactions between PAA and multivalent counterions in solution. Interestingly, the presence of PEO teeth comprised of only a few monomer units in length mitigated such interactions. The rheological property evolution of concentrated cement-PAA/PEO suspensions exhibited complex behavior ranging from the reversible gel-like response observed at short teeth lengths to a remarkable gel-to-fluid transition observed during the deceleratory period for systems comprised of longer PEO teeth. At longer hydration times, all cement-PAA/PEO suspensions exhibited initial elastic modulus values, G(i)' similar to exp(t/tau(c)) before the onset of the acceleratory period, followed by initial set. Their characteristic hydration time, tau(c), and set time depended strongly on the concentration of "free" carboxylic acid groups [COO-] arising from non-adsorbed polyelectrolyte species in solution.