Finite-difference solutions for the blow moulding of polymers

In this paper the cooling and solidification of a blow moulded plastic bottle is investigated. The solidification of the polymer is a Stefan problem where the solid and liquid phases are treated separately with a boundary condition across the solid-liquid interface. The formulation of the mathematical model differs from previous treatments, because the moving boundaries in the solution domain are first fixed using appropriate transformations in the solid and liquid phases and then finite-difference solutions are obtained using a fully implicit scheme. A detailed discussion of the results for the temperature distribution in the two phases and the moving boundaries is presented.