Thermo-mechanical behaviour of Polyamide 6 chain extended with 1,1′-Carbonyl-Bis-Caprolactam and 1,3-Phenylene-Bis-2-Oxazoline

A commercial Polyamide 6 (PA6) was melt compounded by using a twin screw extruder with a combination of 1,1′-Carbonyl-Bis-Caprolactam (CBC) and 1,3-Phenylene-Bis-2-Oxazoline (PBO), in order to evaluate their effect on the chain extension behaviour of the resulting materials. An increase of the viscosity values with the chain-extender amount was evidenced by rheological tests on the compounded pellets and relative viscosity measurements on solubilized samples, while the opposite trend was determined increasing the residence time at elevated temperatures. The increase of the molecular weight due to the presence of CBC and PBO was confirmed by the reduction of carboxylic and aminic functionalities evidenced in end group analysis. DSC tests showed a reduction of the melting temperature and of the crystallinity degree proportionally to the chain extender amount. Elastic modulus of the chain-extended materials was similar to that of the corresponding PA6 grades at different molecular weight, while crystallinity drop due to chain extension determined an increase of the strain at break values.