Carboxyl terminated polyamide 12 chain extension by reactive extrusion using a dioxazoline coupling agent. Part I: Extrusion parameters analysis

Condensation reaction between a carboxyl terminated polyamide 12 (CTPA) (Mn = 2000 g mol(-1)) and a dioxazoline [2,2'-( 1,3-phenylene) -bis(2-oxazoline)] (OO) was achieved by reactive extrusion. Extrusion parameters effects on the process were analyzed through residence time distribution (RTD) and conversion distribution (CD) evolutions. RTD was measured using ultraviolet and ultrasonic detectable tracers. RTD measured along the extruder screws showed a decrease of the dimensionless variance (sigma(theta)(2)) with the reaction progress. Comparing measured molar masses and dispersity with those calculated using CD, competition between condensation and chain scission was detected. Effects of barrel temperature, screw profile, rotation speed and viscous dissipation on the reactive system evolution were analyzed and used for the process optimization. It was shown that a polyester amide with a Dp, 12 can be obtained using this dioxazoline coupling agent by reactive extrusion.