Anionic polymerisation of caprolactam: process monitoring and reaction kinetic studies

Abstract

Reactive processing of PA6 (in-situ anionic polymerization of caprolactam-APCL) enables the production of high performance composite with high mechanical property, good weldability, and recyclability for structural, aerospace and automotive applications.Compare to melt processing, reactive processing enables shorter cycle time, lower processing temperature and pressure. This makes reactive processing a promising new manufacturing technique capable of addressing mass markets.Unfortunately, the insufficient study on influences of processing conditions and reaction kinetics have limited the commercial implementation of the reactive system. This work aims to investigate the processing parameter effect on polymer properties and validate the reaction kinetic models of small scale isothermal polymerization. Experiments were carried out using Differential Scanning Calorimetry (DSC) for the in-situ monitoring of polymerization and crystallization under different processing conditions. Results show that the increase in initiator, activator concentration and polymerization temperature lead to the increase in reaction rate and drop in crystallinity. Whilst this behaviour was expected, the research also shows that the polymer conversion exhibits a far more complex behaviour. For low temperatures, it appears that the monomer conversion is inhibited by early crystallisation whereas for high temperatures the reaction equilibrium shifts towards the monomer state.The derived polymerisation and crystallisation heat flows were used for validation of kinetic models including Kamal-Sourour and Malkin model for polymerisation, Kim model for crystallisation. All experiment data support the validity of Kamal-Sourour model in describing the kinetic development of polymerisation reaction using C1-C20P catalyst system. With the parameters identified from this work, Kamal-Sourour model accurately predict the polymerisation rate under different processing conditions. On the contrast, Malkin polymerisation model failed to give meaningful modelling of the same process. Though Kim crystallisation model gave excellent simulation of the crystallisation process during APCL, the physical meaning of parameter is yet to be determined.

The Effect of the Parameters of T-RTM on the Properties of Polyamide 6 Prepared by in Situ Polymerization

“…The next is between 100 • C and 250 • C, where the various solvents and small molecules (such as monomers, oligomers) leave. Finally, the polymer degrades-the chains break up-above the melting temperature, and as temperature approaches decomposition temperature, the material starts to decompose [18].…”