Optimal Design for PET Bottle to Maximize Reliability

Abstract

Kurzfassung This study presents the new development in the 1.8l Eagle shape of an edible oil bottle made of polyethylene terephthalat (PET) virgin resin. The study refers to an increasing of the stretch ratio between the bottle and the preform. The new preform design offers several advantages including light-weight, reduced electrical consumption, maintaining good quality level and improvement of some mechanical properties (ductility and toughness) for many bottle applications. Mainly, the study has been divided into two parts, i.e. experimental work and finite element analysis. Regarding the experimental work, substantial modifications of the injection unit have been made to produce the new preform fitting to the new stretch ratio. The modification comprises the pair of injection cores, cavity, guide ring, and two pairs of split insert. Also, in the experimental work 126 tension tests with standard samples from bottles before and after the modification have been performed. The specimens have been taken from seven areas of the bottle and have been loaded in two directions (axial and hoop). Finally, the new bottle quality level has been experimentally checked by load tests, stacking tests and center closure leak tests. For the finite element simulations, solid modeling of the complex bottle shape by SolidWorks has been carried out, followed by finite element analyses with Abaqus to calculate the stress and displacement in the bottle areas and also to compare the behavior of the stress distributions for old and new bottles. Among others, as the major result of this study a 16.2% reduction in the bottle weight has been achieved which will reduce the material cost. Regarding the mechanical properties for the new bottle, like ductility and toughness, a number of significant improvements have been made in many bottle areas. In the most critical area, the ductility has been improved by 180% and the toughness by 35%. The non-linear finite element analyses have revealed a maximum stress reduction of 36% as compared to the old bottle.