In the case of energy supply through microwaves, k di f is high due to the stirring but k dis is much lower in comparison to the ultrasonic energy supply. Thus the dissolution is the rate determining step which results in the observed mechanism (R2) which is in line with existing literature . In the case of ultrasonic energy supply, k di f is low but k dis is high when compared to energy supply through microwaves. This results in a mechanism where the diffusion (D2) or the reaction rate (F3) determine the observed rate. This reasoning could explain the observed mechanism difference and is simultaneously compatible with the observation that the dissolution of PA 6 in CEW clearly proceeds faster when supplying energy with ultrasound than with microwaves for t ≤ 16 h (see Figure ). The formulated hypothesis is in line with the literature and will be subject to further investigations in our laboratory.