Wetting and fouling on polymeric films

在当前的项目中，已经研究了各种聚合物表面的润湿和结垢行为。表面粗糙度和前处理技术(等离子体/电晕)的影响已经被量化，并可用于估计工业应用潜力。离子液体(IL)的正润湿特性是进一步研究的诱因，因为具有交替工作对(IL/水而不是溴化锂/水)的吸收式制冷机在过程强化方面具有很高的潜力。由于形成了薄而稳定的液膜，高粘度流体的润湿性增加导致了强化的换热。简单的接触角测量为预测降膜润湿性能提供了深刻的依据。已有的平面表面降膜临界液体负荷关联式(与布局相关)成功地适用于聚合物表面。以不锈钢为基准，可以量化聚合物表面预期的低比例亲和力。建立了沉积量与沉积层表面自由能和附着力之间的关系。未来需要进行研究，以验证聚合物表面的低结垢倾向，也适用于与实际工业过程相关的混合盐溶液。在项目延长一年的时间框架内，计划逐步采用实验方法来描述聚合物表面混合盐沉积的复杂机制。聚合物表面润湿性能的改善可以通过聚合物构象的变化来解释，分子动力学模拟也验证了这一点。结果表明，粗颗粒耗散粒子动力学(DPD)模拟可以用来分析润湿增强的局部条件。然而，除了已经获得的水和聚合物的DPD相互作用参数之外，仍然需要使用替代溶剂(例如，作为有机溶剂的异丙醇)对该方法进行示范验证。

Various polymer surfaces have been studied in the current project with regard to their wetting and scaling behavior. The impact of surface roughness and pre-treatment techniques (plasma/corona) have been quantified and can be used for estimation of an industrial application potential. The observed positive wetting characteristics of Ionic Liquids (IL) are an incentive for further investigations, because of the high potential in process intensification of e.g. absorption chillers with alternate working pairs (IL/water instead of LiBr/water). An increased wettability of the high viscous fluids results in enhanced heat transfer due to the formation of thin and stable liquid films. The simple contact angle measurements gave a profound basis to predict the performance of falling film wetting. Existing correlations for the critical liquid load of falling films (relevant for layout) on plane surfaces were successfully adapted to that of polymeric surfaces. The expected low scaling affinity of the polymeric surfaces could be quantified with stainless steel as benchmark. A relation between deposition quantity and surface free energy as well as adhesive force of the deposit was established. A demand for future investigations exists to verify the low scaling propensity of the polymer surfaces also for mixed salt solutions relevant for real industrial processes. A stepwise adaption of the experimental methodology to describe the complex mechanisms of mixed salt deposition on polymeric surfaces is planned within the time frame of the one year project extension. The improved wetting performance of the polymer surfaces due to conditioning could be explained by changes in polymer conformation, also validated by molecular dynamics simulation. It could be shown that coarse grained dissipative particle dynamics (DPD) simulations can be used to analyze the local conditions for wetting enhancement. However, in addition to the already obtained DPD interaction parameters of water and polymer an exemplary validation of the methodology using an alternative solvent (e.g. isopropanol as organic one) is still necessary.