Investigation on the reactive processing of textile-ramie fiber reinforced anionic polyamide-6 composites

Abstract A reactive processing was adopted to prepare a new-style and environmentally friendly thermoplastic composite consisting of anionic polyamide-6 (APA-6) and textile-ramie fiber. However, severe polymerization-inhibition and fiber-discoloration phenomena had happened in reactive processing of ramie fiber reinforced APA-6 composites. To analyze the mechanism and find out the solutions for these issues, three kinds of initiators for APA-6 were selected to react with powdery ramie fiber at 150 °C under vacuum respectively. Then, the discolored by-products obtained from the reactions were analyzed using Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance (NMR) and atomic absorption spectroscopy (AAS). Finally, it was concluded that the reasons for inhibition and discoloration phenomena were mainly due to the special by-products generated from the peeling reaction of cellulose, which were also easy to react with initiators simultaneously. It meant that the initiators for APA-6 were consumed severely, thereby resulting in the failure of polymerization. Meanwhile, a kind of new initiator, caprolactam magnesium bromide, with low activity and weak alkalinity, weakened the peeling reaction and the reaction with active groups on the special by-products, thus the inhibition and discoloration phenomena were suppressed significantly, which overcame the most important challenges for the preparation of ramie fiber reinforced APA-6 composites via reactive processing. This work not only open a new avenue for development of environmentally friendly composites, but also further broaden the applications of natural fibers.