超临界二氧化碳间歇式发泡工艺制备原位微纤增强聚丙烯泡沫

In-Situ Fibril Enhanced Polypropylene Foams Fabricated by Supercritical CO_(2)Batch Foaming Process Aimin

采用熔融共混法制备了球状聚四氟乙烯(PTFE)和原位PTFE微纤增强聚丙烯(PP)复合材料,利用自主研发的间歇式发泡系统制备了纯PP,PP/S-PTFE(球状PTFE增强PP)和PP/F-PTFE(原位PTFE微纤增强PP)发泡件。扫描电镜和光热诱导红外显微镜揭示了PTFE一步法成纤的关键因素是PTFE的伸长链晶体结构和表面处理工艺;X射线衍射分析显示PP,PP/S-PTFE和PP/F-PTFE都呈现α晶体结构。在确定的发泡压力下,发泡倍率随着发泡温度的升高先增加后减小,而发泡压力从5 MPa提高为15 MPa,发泡温度区间向低温段扩展了10℃。原位PTFE微纤对复合材料的最大发泡倍率有一定的抑制作用,但相同发泡倍率下,PP/F-PTFE泡沫件的泡孔直径最小,泡孔密度最大,泡孔尺寸均匀性最优,其泡沫件的压缩强度比相同发泡倍率PP泡沫件压缩强度提高了123%。

Spherical polytetrafluoroethylene(PTFE)and in-situ fibrillary PTFE reinforced PP composites were prepared by one-step melt blending method.Then pristine PP,spherical PTFE reinforced PP(PP/S-PTFE)and in-situ fibrillary PTFE reinforced PP(PP/F-PTFE)foams were fabricated by self-developed batch foaming system.Scanning electron microscopy(SEM)and photo thermal induced infrared microscope reveal that the extended chain crystal structure and surface modification of PTFE are the critical factors which lead to the in-situ fibrillation of PTFE.X-ray diffraction(XRD)results show that PP,PP/S-PTFE and PP/F-PTFE all presentαcrystal structure.The expansion ratio firstly increases and then decreases with the increased temperature at a given pressure,however,the foaming temperature range is extended to lower temperature by 10℃when the pressure increases from 5 MPa to 15 MPa.The maximum expansion ratio of PP/PTFE composites is reduced with the incorporation of in-situ PTFE fibril,yet it is beneficial to the optimization of cell structure and improvement of mechanical properties.According to the SEM observation and compressive test,PP/F-PTFE foams exhibit the smallest cell size,the highest cell population density and the best standard deviation of cell size,the compressive strength of PP/F-PTFE foams is higher than that of PP foams by 123%with the same expansion ratio.