Numerical Modeling of Bubble Growth in Microcellular Polypropylene Produced in a Core-Back Injection Process Using Chemical Blowing Agents

A core-back polypropylene foaming injection process using chemical blowing agents (CBA) has been studied. First, injection tests were carried out with two different CBAs and the different morphologies of the obtained samples have been analyzed. Structural parameters such as cell density and average radius size were calculated. Then, a bubble growth model was developed to predict the foaming development during the process, controlled by the depressurization of the mold cavity during the short core-back opening coupled with the evolution of the temperature during core-back and subsequent cooling. A good agreement is found between theoretical predictions and experimental results.