聚乙烯醇在超临界二氧化碳中的发泡行为

Foaming Behavior of Poly (Vinyl Alcohol) with Supercritical Carbon Dioxide

采用甘油作为聚乙烯醇(PVA)的塑化改性剂,实现了PVA的热塑成型,以超临界二氧化碳(scCO_2)为物理发泡剂,采用间歇式降压法制备了一系列PVA泡沫材料。利用差式扫描量热仪和流变仪系统研究了甘油对PVA的熔融行为和流变性能;并采用扫描电镜(SEM)研究了发泡温度、饱和压力和保压时间对泡孔形态的影响。结果表明,40%甘油增塑PVA体系的熔融温度降低至177.7℃,且在发泡温度下具有合适的黏度;随发泡温度的提高,PVA泡沫材料的泡孔尺寸增大,泡孔密度下降;增大饱和压力和适当延长保压时间,可提高增塑PVA体系的发泡效果。在合适的工艺条件下,发泡温度为185℃,饱和压力为15 MPa,保压时间为60 min时,PVA泡沫材料的发泡效果良好,其泡孔尺寸50.6μm,泡孔密度为8.8×10~6个/cm^3。

Glycerin was used as the plasticizing agent for poly （vinyl alcohol） （PVA） to realize its thermal processing, and PVA foam was successfully prepared via the batch depressurization foaming process using supercritical carbon dioxide （scCO2） as the physical blowing agent. The melting behaviors and theological properties of plasticized PVA were investigated with differential scanning calorimetry （DSC） and rheometer. Scanning electron microscope （SEM） was adopted to study the influences of foaming temperature, saturation pressure and time on the cellular structure of PVA foams. The results indicated that the melting point of plasticized PVA with 40% glycerin was decreased to 177.7 ~C , and an appropriate viscosity was obtained at the foaming temperature. With increasing the foaming temperature,the cell size increased and the cell density were decreased;better cellular structure was obtained in final PVA foaming product when higher saturation pressure and longer holding time. PVA foam with favorable structure could be produced at foam temperature of 185℃ , saturation pressure of 15 MPa and holding time of 60 min,the cell size and cell density were 50.6 μm and 8.8 × 106 cell/cm3.