Functional microporous materials

点击翻译按钮获取中文摘要

Today, microcellular foams are found in several applications because of their low density leading to good specific mechanical properties (strength per unit weight). Nevertheless, the overall foam properties are mainly controlled by their structures, not only in terms of cell size and cell density, but also with respect to cell morphology (deformation and orientation). So the long term objective of this research is to understand how the processing conditions can be used to control the final morphology of microcellular polymers. In the next five years, the focus will be on two important applications: gas separation and piezoelectric membranes. The first part of the project will focus on applications where polymer membranes (flat membranes or hollow fibers) have been developed for gas purification. The concept of mixed matrix membranes will be used as to control both permeability via an optimization of the polymer foam matrix, and selectivity via the addition of porous nano-particles like zeolites, metal organic frameworks, and clays. The main challenges, besides materials selection, is to optimize the processing conditions (pressure, temperature, flow rates, and equipment geometry) to get good dispersion and compatibility (adhesion) between all the phases. To solve this problem, it is proposed to produce in situ the nano-particles and blowing agents by using a twin-screw extruder as a chemical reactor (reactive extrusion). The second part of the work will be devoted to the production of piezoelectric polymer membranes. These materials are now used in applications like transducers and sensors for automotive and medical applications, as well as sporting goods and transportation/packaging logistics for real-time impact damage monitoring. Piezoelectricity is related to the possibility of a material to polarize under mechanical stresses. To get the effect in a polymer, the electrical equilibrium must be perturbed by creating positive and negative charges at the surface of the material (charging). This is where the foam structure comes into play since a very high amount of interfacial area can be created per unit volume. To optimize the effect, not only cell size and cell density are important, but also cell deformation and wall thickness. In this case, different methods (extrusion calandering = uniaxial elongation, or extrusion blowing = biaxial elongation) will be studied to produce single layers or multi-layers. Once optimized, the results of this research programme will be used to develop technologies for other important areas like automotive, building and construction, functional packaging, material handling, transportation, sound insulators, energy sources (battery/fuel cell), battery separators, tissue engineering, water purification, gas-liquid absorption, filtration, and reaction engineering (catalysis). A total of four students and one technician per year will be trained.