双峰泡孔结构聚苯乙烯材料的制备

PREPARATION OF POLYSTYRENE FOAMS WITH BI-MODAL CELLS

以超临界二氧化碳（Sc-CO2）为物理发泡剂,在高压釜中采用两种温度设定方式和降压对聚苯乙烯（PS）进行发泡,测试、分析发泡样品的泡孔结构、泡体密度和断面润湿性能.结果表明,仅通过降压只获得单峰的泡孔结构,而升温与降压协同作用可获得双峰的泡孔结构,大、小泡孔分别在升温和降压阶段成核形成;在发泡温度100 ℃、饱和温度30~70 ℃下制备的发泡样品中,大、小泡孔的平均直径分别为50~216和10~15 μm.大泡孔的直径较大和密度较高都有利于降低样品的泡体密度,最低达0.15 g/cm3.单峰泡孔结构能在一定程度上提高样品断面的疏水性,使静态接触角（CA）从PS的本征值（87.1°）增大至138.8°;双峰泡孔结构可赋予样品断面更高的CA（155.1°）,呈现超疏水特性.

Using supercritical carbon dioxide （Sc-CO2） as the physical foaming agent,polystyrene （PS） foams were prepared in a batch process via two different heating modes and depressurization.The cellular structures,foam densities and wetting properties of the PS foams were investigated by means of scanning electron microscope,electronic balance and contact angle measuring device,respectively.The results showed that a mono-modal cell structure was obtained only through depressurization,whereas a bi-modal cell structure was achieved through the synergistic effect of heating and depressurization.The large and small cells were formed by nucleation in the heating and depressurization stages,respectively.For the PS foams prepared at 100 ℃ foaming temperature and 30~70 ℃ saturation temperatures,the large and small cells had average diameters of 50~216 and 10~15 μm,respectively.Increasing the diameter and density of the large cell was favourable to the decrease of the foam density,and the lowest foam density was 0.15 g/cm3.The mono-modal cell structure yielded an increase in static contact angle （CA） from the intrinsic value of the PS （87.1°） to 138.8° on the fractured surface of the foam; the CA value on the surface with a bi-modal cell structure prepared at 70 ℃ saturation temperature increased up to 155.1°,displaying the superhydrophobic wetting properties.