Study On The Mechanism And Regulation Of Ipp Foaming Behavior By Thermal History And Nucleating Agent

Microcellular foam materials have the advantages of lightweight,impact resistance and so on.Microcellular foamed materials have been applied in packaging,electronic appliances products,armarium,sports goods,automobile industry and the other files.iPP is one of the commonly used plastics due to the relatively cheap price,higher deforming temperature and preferable chemical resistance.The microcellular foaming of i PP is one of the hot research topics in recent years.However,the weak melt strength of iPP usually results in less ideal cell structure,which hinders its application in foaming fields.The improved melt strength and cell nucleating ability were obtained by suitable thermal history and low loading nucleating agent,and the enhanced microcellular foamability of iPP were studied in this work.The main contents of this paper were illustrated as below:?1?The rheological test results indicated that the introduction of annealing treatment could increase the values of G'and G''due to the importing of partially ordered structures,compared to that of the iPP without such treatment after the eliminating of former thermal histories.Clearly,cooperated with the nucleating agent,which effectively increased the melt strength of iPP and which would further influence its microcellular foaming properties.?2?Using the batch foaming process,iPP and the 0.2 wt%DMDBS loaded iPP?iPP/0.2DMDBS?were foamed,cooperating with annealing treatment.Introducing the partially ordered structured by annealing,the broadened foaming temperature windows were sketched out at the situations of 6¹8 MPa compressed CO₂.A wide temperature scope of 23³1?C of iPP and an even more broader window of 63?C?110¹73?C?of iPP/0.2DMDBS at 18 MPa were figured out.Quite uniform cells with the cell densities of about 10⁹¹0¹² cells/cm³ were produced,while the foaming temperatures were set at around iPP's melting point.?3?Moreover,the influences of nucleating agent content,CO₂ saturation time,annealing time,saturation temperature and saturation pressure on iPP's crystallization,foaming behaviors were also investigated,at the presence of history control and the application of nucleating agent.Quite uniform cells with the average sizes of micrometers to nanometers and the cell densities of 10¹⁰¹0¹² cells/cm³ were produced,which provided the theory of continuous extrusion foaming for the subsequent iPP and accumulated the experimental data for further continuous extrusion foaming of iPP.