Waldner Carina, Hirn Ulrich
Institute of Bioproducts and Paper Technology, TU Graz, Inffeldgasse 23, 8010 Graz, Austria.
CD Laboratory for Fiber Swelling and Paper Performance, Inffeldgasse 23, 8010 Graz, Austria.
Materials (Basel). 2020 Jun 17;13(12):2754. doi: 10.3390/ma13122754.
Ultrasonic liquid penetration (ULP) measurements of porous sheets have been applied for a variety of purposes ranging from determining liquid absorption dynamics to surface characterization of substrates. Interpretation of ULP results, however, is complex as the ultrasound signal can be affected by several mechanisms: (1) air being replaced by the liquid in the substrate pores, (2) air bubbles forming during penetration, and (3) structural changes of the substrate due to swelling of the substrate material. Analyzing tailored liquids and substrates in combination with contact angle measurements we are demonstrating that the characteristic shape of the ULP measurement curves can be interpreted in terms of the regime of liquid uptake. A fast and direct decline of the curve corresponds to capillary penetration, the slope of the curve indicates the penetration speed. A slow decline after a previous maximum in the signal can be related to diffusive liquid transport and swelling of the substrate material.
多孔片材的超声液体渗透（ULP）测量已被用于多种目的，从确定液体吸收动力学到基材的表面表征。然而，由于超声信号可能受到多种机制的影响，ULP结果的解释很复杂：（1）基材孔隙中的空气被液体取代；（2）渗透过程中形成气泡；（3）基材材料膨胀导致基材结构变化。通过结合接触角测量分析定制的液体和基材，我们证明了ULP测量曲线的特征形状可以根据液体吸收机制来解释。曲线的快速直接下降对应于毛细管渗透，曲线的斜率表示渗透速度。信号先达到最大值后缓慢下降可能与液体的扩散传输和基材材料的膨胀有关。
