碳化硅/炭黑悬浮体中丙烯酰胺单体自由基聚合的研究

采用2种引发体系引发碳化硅／炭黑悬浮体中丙烯酰胺单体的自由基聚合，通过测定单体聚合的热效应对丙烯酰胺单体的自由基聚合过程进行了表征，并分析了丙烯酰胺单体在碳化硅／炭黑悬浮体中的聚合机理。发现炭黑的存在不仅可以加速过硫酸铵分解，而且对丙烯酰胺单体的自由基聚合具有较强的阻聚作用，造成碳化硅／炭黑悬浮体聚合诱导期过短和单体聚合转化率较低。采用氧化还原引发体系可以提高单体转化率并实现单体聚合，但无法延长单体聚合的诱导期。通过在碳化硅／炭黑悬浮体中添加不同用量的缓聚剂乙酰丙酮，可以显著改善单体的聚合特性，不仅可以随意控制单体聚合的诱导期，而且还可以提高单体聚合的转化率，从而保证了碳化硅／炭黑悬浮体的凝胶注模工艺的实施。

FREE-RADICAL POLYMERIZATION OF ACRYLAMIDE IN AQUEOUS CONCENTRATED SILICA CARBIDE/CARBON BLACK SUSPENSIONS

Two initiator systems were used to initiate free_radical polymerization of acrylamide in aqueous concentrated silica carbide/carbon black suspensions. The heat evolution of the suspension was measured to characterize the polymerization process of acrylamide and the polymerization mechanism was proposed. It is found that the existence of carbon black can not only accelerate the decomposition of ammonium persulfate but also inhibit strongly the free_radical polymerization of acrylamide, resulting in the lower conversion and short idle time of polymerization. Conversion of polymerization can be improved by using oxidation-reduction initiator system but it is difficult to extend the idle time. By adding acetylacetone, the idle time of the free_radical polymerization of acrylamide in aqueous concentrated silica carbide/carbon black suspensions can be adjusted to the suitable value to satisfy the needs of gelcasting process.