Postcondensation and oxidation processes in molten polyamide 6

Abstract

Polyamide samples were heated under vacuum or mixed in a Brabender plastograph. UV absorbance, chain end concentration, and molecular weight were studied. Postcondensation was observed for polyamide heated under vacuum. For polyamide samples mixed in the plastograph, atmosphere, shear rate, and temperature changed. Melt viscosity and intrinsic viscosity are in good correlation in a log‐log plot. Oxidation effect on molecular weight and amine chain end concentration could be well related to UV absorbance. The oxygen diffusion into the molten polyamide is a critical parameter. The oxygen concentration in the polyamide mixed under air is ca. 20 times higher than when mixed under nitrogen. The introduction of preoxidized material in the molten polyamide or mixing in the presence of oxygen have similar effects. Postcondensation and oxidation strongly influence the melt behavior of polyamides. © 1993 John Wiley & Sons, Inc.

PLA/PA Bio-Blends: Induced Morphology by Extrusion

“…Moreover, the PA had a similar behavior to the PLAREx with a complete clear shear thinning region in the range tested and higher strain rate sensitivity with the shear rate. Also, PA was presented upward in the trace, which can be associated with a post-condensation process in low frequencies, and has been found in studies of PA11 and PA6 [16,41,42]. In relation to the storage modulus (G') presented in Figure 5b, the PLA had the lowest values and reached the terminal region.…”

Time-resolved rheology as a tool to monitor the progress of polymer degradation in the melt state – Part I: Thermal and thermo-oxidative degradation of polyamide 11

“…However, the occurrence of concurrent degradation reactions cannot be excluded. In particular, oxygen and air moisture could promote chain scission and hydrolysis reactions [23,30,31]. In the next Section we discuss how to discriminate among these possible degradation mechanisms by means of rheological analysis.…”

Review on the thermo-oxidative degradation of polymers during processing and in service

“…Polyamides containing primary amino end-groups show yellowing almost from the start of oxidation, whereas their molecular weights drop much more slowly [123][124][125][126][127][128][129][130][131][132][133]. Amine end groups can initiate the homolysis of hydroperoxides too, but primarily they condense with aldehydes generated by oxidation to aldimines [134].…”