阴离子聚合PA6与苎麻纤维复合反应中的阻聚与变色机理的研究

Mechanism of Retardation and Discoloration in Reactive Processing of Anionic Polyamide-6 and Ramie Fiber

通过浇注成型的方法研究并发现了苎麻纤维与阴离子聚合尼龙6(APA-6)反应加工过程中严重的阻聚和变色问题.为了分析阻聚和变色的机理并寻找解决方案,选取了3种不同的引发剂(氢氧化钠、己内酰胺钠盐和己内酰胺溴化镁)分别与微晶纤维素(MCC)在150℃的真空条件下反应.然后分别采用傅里叶变换红外光谱、原子吸收光谱、X-射线衍射和核磁共振波谱表征了引发剂和MCC反应前后的变化.结果证明,阻聚和变色的机理是在强碱性和高温条件下,纤维素发生了剥皮反应,产生的副产物又极易与引发剂反应,因此导致APA-6中起引发作用的己内酰胺阴离子被消耗,从而使得聚合反应终止.另外,由于己内酰胺溴化镁(C1)的低活性和弱碱性,使得剥皮反应很大程度的降低,进而避免了引发剂阴离子的消耗,从而使得阻聚和变色问题得到明显改善,最终实现了通过反应加工的方法制备APA-6与苎麻纤维复合材料的目的.

Three kinds of initiators （sodium hydroxide, sodium caprolactamate and caprolactam magnesium bromide） were selected to react respectively with microcrystalline cellulose （MCC） under vacuum at 150 ℃ for analyzing the mechanism of the severe retardation and discoloration in the reactive processing of anionic polyamide-6 and ramie fiber, with using conventional sodium initiators. Then the changes of the sodium caprolactamate （C10） and MCC before and after reaction were analyzed using Fourier translation infrared spectroscopy （FTIR） , atomic absorption spectroscopy （AAS） , X-ray diffraction （XRD） and nuclear magnetic resonance spectroscopy （NMR）, and it was concluded that the retardation and discoloration were mainly caused by the special byproducts generated from the peeling reaction of cellulose in alkaline and high-heat conditions, which were easy to react with anions dissociated from initiator, resulting in the consumption of the initiators,so as to make the end of polymerization of anionic polyamide-6. In addition,the initiator caprolactam magnesium bromide （C1）, due to low-activity and weak-alkalinity,weakened the peeling reaction and the reaction with the active groups on the byproducts, and thus the retardation and discoloration were improved significantly ,which were the most important challenge during the reactive processing. Finally, the goal was achieved for manufacturing the ramie fiber-reinforced anionic polyamide-6 composites by reactive processing.