Method for manufacturing a polyester based polymer article

A method for manufacturing a polymer article comprising injecting a semi-crystallizable polyester based polymer melt in a flow path for converting it into a semifinal shape, wherein the polyester based polymer melt is converted at a given local pressure and a selected given melt processing temperature, wherein at ambient pressure said selected given melt processing temperature is higher than the crystallization temperature of the semi-crystallizable polyester based polymer at ambient pressure as determined from the corresponding PVT graph of the semi-crystallizable polyester, modifying the flow path of the semi-crystallizable polyester based polymer melt such that the local pressure increases thereby increasing the crystallization temperature where the local pressure is applied to at least the selected given melt processing temperature of the semi-crystallizable polyester based polymer melt and

• comprising injecting the polyester based polymer into a preform mold for converting the polyester based polymer into a preform while applying a local shear and/or extensional deformation on the polyester based polymer melt, wherein applying the local shear and/or extension deformation on the polyester based polymer melt comprises selectively modifying the flow path of the polyester based polymer melt as a function of a local pressure profile over at least part of the flow path, said local pressure profile being determined as a function of optimized response of the polyester based polymer melt to the applied local shear and/or extensional deformation over at least said part of the flow path.