Abstract

Bulk polytetrafluoroethylene (PTFE) foam is a great potential oil–water separation material, owing to the high hydrophobicity and lipophilicity property. However, the technique of fabricating PTFE foam with low cost, controllable porosity and high mechanical strength remains an urgent requirement due to its high chemical inertness induced limitation. A kind of bulk PTFE foam material is prepared by cold pressing co-sintering method, employing sodium chloride (NaCl) as pore forming agent. SEM measurements reveal that the size and distribution of pore structure are mainly determined by the particle size and content of NaCl, because the migration and diffusion behaviors of PTFE particles suffer from more inhibition induced by increased NaCl particles during sintering. The PTFE foam with uniformly distributed pore structures can be obtained from composite mixed with 70 wt% NaCl and 30 wt% PTFE, with a low thermal conductivity as low as 0.069 W/(m K). With the decrease of PTFE content in raw composite, the density and mechanical properties of PTFE foam gradually declines. However, the tensile strength remains as low as 0.2 MPa, with an elongation rate of 21%, which guarantees the required mechanical strength avoiding being broken when use as a bulk oil absorption material. Remarkably, the PTFE foam shows a strong hydrophobicity, with a mean water contact angle of 137°, and with a mean surface roughness of 4.41 μm. It exhibits separation efficiency larger than 99% in 30 cycles, with separation flux larger than 4000 L/m²/h within 15 cycles, indicating excellent recyclability and stability. The PTFE foam sample also shows desirable continuous separation performance for oil/water mixture. The proposed bulk PTFE foam with low manufacturing cost and stable chemical and mechanical properties will provide data and theoretical support for the material applied in oil/water separation and thermal-protective coating.

中文翻译：

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氯化钠和聚四氟乙烯共烧结制备油水分离泡沫材料

摘要

块状聚四氟乙烯（PTFE）泡沫由于具有高疏水性和亲油性，是一种极具潜力的油水分离材料。然而，由于其高化学惰性引起的限制，低成本、可控孔隙率和高机械强度的PTFE泡沫的制造技术仍然是迫切的需求。以氯化钠(NaCl)为造孔剂，采用冷压共烧结法制备了一种块状聚四氟乙烯泡沫材料。SEM测量表明，孔隙结构的尺寸和分布主要由颗粒尺寸和氯化钠含量决定，因为烧结过程中氯化钠颗粒的增加对PTFE颗粒的迁移和扩散行为造成更多的抑制。由70 wt% NaCl和30 wt% PTFE混合而成的复合材料可获得孔结构分布均匀的PTFE泡沫，导热系数低至0.069 W/(m·K)。随着复合原料中PTFE含量的减少，PTFE泡沫的密度和力学性能逐渐下降。但拉伸强度仍低至0.2MPa，伸长率为21%，保证了用作散装吸油材料时所需的机械强度，避免断裂。值得注意的是，PTFE泡沫表现出很强的疏水性，平均水接触角为137°，平均表面粗糙度为4.41μm。30个循环的分离效率大于99%，15个循环的分离通量大于4000 L/m ² /h，表现出优异的可回收性和稳定性。PTFE 泡沫样品还显示出理想的油/水混合物连续分离性能。所提出的块体PTFE泡沫具有较低的制造成本和稳定的化学和机械性能，将为该材料在油水分离和热防护涂层中的应用提供数据和理论支持。