Study On Preparation Of Open-cell Polylactide Foam Using Supercritical CO₂Foaming

Open-cell foaming material is a kind of foamed material, in which cells are mutual connected. The open-cell structure enables much unique use. Separate material by designed cell size and grow cells as tissue engineering scaffold. Polylactide is biology safe and biocompatible, and can be absorbed and degraded, is very important biology material. Scholars home and abroad have studied many methods to make open-cell polylactide material, such as heat induced phase separation, electrostatic spinning,3-D print, supercritical CO2foam, salt drain filter method.This paper is based on supercritical CO2foaming theory, to get high open-cell content, uniform cell, cell size controlled open-cell material by adding water, alcohol, ether, alkane or ketone. This paper study the influence of agent adding and process conditions on PLA open-cell foaming. This paper firstly studied the influence of water on PLA foaming. The influence of volume ratio of water and CO2, foaming temperature and discharging pressure method on PLA foaming was studied. Then influence of acetone/Butyl ketone, foaming conditions and volume ratio of CO2and acetone/Butyl ketone on PLA foaming was studied. The influence of, foaming temperature, foaming pressure, and discharging pressure methods on PLA foaming was studied. Finally the influence of acetone, butyl ketone, cyclohexanone, ethyl ether, ethanol, is1-bromopentane, cyclohexane on PLA foaming was compared.The results of the study indicate that:PLA foam samples adding water have obvious open-cell structures, big and irregular shape cell, wide pore size distribution. This is because water degraded PLA which caused melt viscosity and intensity reduced, and cell broken when foaming. Both PLA/acetone and PLA/d ketone foaming material have obvious open-cell structure and high open-cell content; And as the foaming temperature increase, cell diameter increases, cell size distribution broadens; And as the foaming pressure increase, open-cell structure increases gradually; as volume ratio of acetone or butyl ketone and CO2increase, open-cell structure and cell size increase; when volume ratio is much bigger open-cell structure decrease. At same foaming condition and volume ratio, the open-cell effect of butyl ketone, acetone, cyclohexanone was studied. And butyl ketone, acetone, cyclohexanone can make high open-cell content foam, the biggest86.3%. At same foaming condition and volume ratio, the open-cell effect of different agent is different. Discharging pressure once condition, open-cell effect order is cyclohexanone, ethyl acetate, cyclohexane,1-bromopentane,ethanol; other agents except ethanol have good open-cell effect. Discharging pressure twice from good to bad order:butyl methadone, cyclohexane, ethyl ether, ethanol.