Preparation Of LLDPE And PLA Microcellular Foam Based On Supercritical Fluid Technology

Microcellular foamed materials possess excellent mechanical properties and unique micro-pore morphology.Which has gained many scholar's attention in industrial and theoretical research.Microcellular foams have smaller cell sizes and higher cell density than conventional foams.Material weight can be greatly reduced,while this material has the advantages of high strength,low thermal conductivity,which can be used as thermal insulation materials and can also play a role in insulation field.According to the cellular foam material has a higher specific strength,high impact strength and good fatigue resistance characteristics,foam materials can be used in cushioning and other fields,such as the growth of children's needs crawling mat,Protective cover of car front cover and so on.For the high open-cell ratio of microcellular foam,it can be used in oil absorption,sound-absorbing materials,biodegradable scaffolds,pollution filtration and so on.Polyethylene microcellular foams with closed-cell morpologies have applied on insulation,heat insulation,damping and other aspects.In this paper,the microcellular foaming behavior of EPDM/LLDPE blends with supercritical CO₂ was studied.The effects of mass ratio of rubber to plastic,foaming temperature and saturation pressure on the cell structure and cell homogeneity of EPDM/LLEPE blends were discussed.Foaming parameters were optimized to foam closed cell material having regular cell size,high cell density,good resilience and toughness.On the basis of preparation of closed-cell material,it is continued to explore the use of supercritical carbon dioxide foaming method to prepare the surface and the interior are interconnected materials.Foaming of polylactic acid?PLA?by supercritical CO₂ foaming method is almost impossible to form cells in foam skin zone,which greatly limits its application in biological cell inoculation and biological tissue culture application.However,due to the limitations of the process of the breath figure method,only an apertured film material can be prepared and an apertured material with a certain thickness can not be obtained.Therefore,in view of the above problems,In this work,CO2 foaming technology and breath figures method were combined to prepare open and skinless polymer foams first time.Firstly,a polylactic acid foam with internal openings is prepared by supercritical CO2 foaming.Then,treating the PLA foam surface by a mixed solvent method,the skin and the internal are open and adjustable structure of the PLA skinless cell material was successfully prepared.