Study On The Dynamic Foaming Process Of Polypropylene With The Visualization Method

The polypropylene foam material is a kind of composites including polypropylene as the dense phase and gas phase,it has so many excellent performances that have get the widespread attention in the material industry.As is well known,the properties of foam products are determined by microcellular structure when the matrix materials has been fixed.In the mean time,the formation of microcellular structure is depended on foaming process.Consequently,the researchers show greater interests in foaming process of microcellular injection molding.In order to obtain the high quality foam material,it is very important to understand and master how the foaming process affecting the bubble pore structure.Many researchers usually study the foaming process by analysising the final cell structure,however,the foaming process can't be directly observe by this method.So this paper invesgated the dynamic foaming process by the visualization system with the variable temperature process.The complete process of cell growth and cooling setting was recorded,and the cell morphology and distribution was analysised in the different condition.The formation of polypropylene cell during injection molding foam was obtained by analyzing the foaming dynamic process experiment and chemical injection molding foam.The aim of this paper is to privide the reference to improve the cell structure of polypropylene in c hemical injection molding foam.The results show as follows:(1)The visualization system used in this paper was the powerful method to research c hemical injection molding foaming procee.(2)When the nucleating agents were added,and the foaming agent content and the cooling temperature were changed,the visualization foam proocess showed the similar change law in the injection molding foam.As the increase of foaming agents from 0.5% to 1.5%,the cell numbers increased and the ? stage was apprared early.The ? stage would be broadened when the foaming agent was 1.0%.The nucleating number not only increaed the cell numbers of ? stage,but postponed the ? stage due to the increase of the growth restraining force.(3)It was a good way to postpone or eliminate the ? stage and get the optimum cell structure by increasing the cooling rate.The faster cooling rate can cause the more stationary cell morphology,the less deformation of cell and the preferably cell structure.(4)The growth of the cells appeared fast growth stage and low growth stage,the low growth stage was mainly at ? stage and ? stage.and the growth restrained force was the main controlled factor.(5)The cell structure would be deformation when the cells grew to a certain degree.When the deformation happened,the melt between the two cell restraind the cell growth in the contact direction,however,the cells grew normally in other directions.So the cells would become the elliptical shape eventually.In the chemical molding foaming,the cell merge was hardly finished as the foaming process contained cooling process.