Reactions occurring during the melt mixing of nylon 6 and oxazoline - Cyclophosphazene units

Abstract

Specific reactions of amino and carboxyl end groups of Nylon 6 with the reactive oxazoline groups belonging to a cyclophosphazene compound (referred as CP20XA) were carried out at 240 °C for different times, under inert atmosphere. Ny6 polymers terminated with one specific reactive chain end (-COOH or NH2) were reacted with different amounts of CP20XA to study the kinetic order of the reactions. All Ny6-CP20XA reacted products soluble in trifluoroethanol (TFE) were well characterized by MALDI-TOF MS, FT-IR and ( 1H and 13C) NMR techniques. The MALDI-TOF results show that the oxazoline rings react with the carboxyl chain ends of Ny6 following second-order kinetics. The reactions with amino chain ends are very fast and high amounts of gels are produced in just 5 min heating, whereas traces of gel are formed when Ny6C00H and CP-20XA are reacted for 60 min. The gels were characterized by FTIR analyses, and also by MALDI-TOF MS after partial acid hydrolysis. MALDI-TOF mass spectra reveal also that oxazoline rings can react with -NH amide groups along the Ny6 chains, and with secondary amino groups formed by a condensation reaction involving the elimination of ammonia from two amino chain ends. These side reactions could be responsible of the formation of the gels. The polymerization of CP20XA was also observed, and the oligomers formed could also react with Ny6 samples during the melt mixing.