Block copolymers (BCPs) have long been pursued as precursors to nanoporous materials such as filtration membranes. Selective swelling-induced pore generation has emerged as an extremely simple strategy to BCP membranes with both well-defined nanoporosity and inherently functional surfaces. Selective swelling produces pores is based on the strong swelling in the selective solvent and subsequent collapse during solvent evaporation of the minority blocks in the continuous phase composed of the majority blocks. It is a nondestructive process producing pores at no expense of any component of the BCPs. Thus-prodcued pores can be tuned typically in the range ~ 10-50 nm either by changing swelling conditions or molecular weights of BCPs. Interestingly, due to the immigration of the minority blocks onto the pore wall, the resulting porous materials possess an intrinsically active surface with enhanced hydrophilicity or hydrophobicity. By annealing the BCP films with appropriate solvents to align the minority blocks either normal or parallel to the substrate surface followed by selective swelling, we are able to obtain two different types of homogeneously porous structures: “standing” pores and “sleeping” pores, both having uniform pore sizes. In this talk, I will also highlight our results toward the upscaling of this method, the large-scale, affordable synthesis of polysulfone-based BCPs and the continuous manufacturing of BCP membranes by melt extrusion coupled with microwave-boosted selective swelling.

This study contains the process optimisation of hybrid-filled thin electrically conductive polypropylene (PP) films using a filler mixture of multi-walled carbon nanotubes (MWCNTs) and carbon black (CB). Essential for use as separator foil in battery applications [1] is that MWCNTs orientate strongly in the extrusion direction so that no or only low conductivity can be achieved through the film [2]. An additional used CB as a second filler solves this drawback because of its non-orientation during the extrusion process due to its spherical shape, resulting in interconnections between the CNTs. Different admixtures of MWCNT (2 types) and CB were used to affect the film properties. Under constant extrusion conditions, the use of sieve changers at the end of extrusion was investigated. Different pore sizes of the sieves were used. Thin films with a target thickness of 50 µm were then extruded at constant conditions. Depending on the filler concentration and the MWCNT type, residual agglomerates were sometimes found in the granulate in light microscopic study on thin sections. As a result, the films produced had holes and the roughness was different. The electrical conductivities in all three spatial directions were in the same range.

Thanks for the financial support by Federal ministry for Economic affairs and climate action, project BiPoLiS (grant 03ETE043D) and Federal ministry for Economic affairs and energy, project PLANAR MABAT (grant ZF4028415ZG8). We would like to thank Frank Werheid for producing the samples and Ines Kühnert for providing the extruder.

The current technology used in insulation system of HVDC (High Voltage Direct Current) cables is based on the use of crosslinked polyethylene (XLPE). The replacement of XLPE by thermoplastics such as polypropylene (PP) in insulating systems is being considered due to their recyclability and shorter processing time compared to XLPE [1]. Many researchers had noticed positive effects when adding inorganic nanofillers (SiO₂, MgO or TiO₂) via melt mixing to polymeric insulation systems, aiming to improve their electrical properties, including resistivity, breakdown strength, and space charge [2,3]. However, the industrialization of these systems is limited by the controversial handling of nanoparticles and by the difficulty to reach well dispersed fillers within the matrix, which is a critical point to achieve high performance nanodielectrics. To overcome these issues, the generation of inorganic particles directly in molten PP via a sol-gel route is considered in the current study. Authors reported the possibility to prepare PP/inorganic fillers nanocomposites by in situ generation of the fillers via reactive extrusion [4,5]. In this present work, PP/SiO₂ composites were prepared from an alkoxysilane as silica precursor. In a first step, the influence of key parameters such as the catalyst pH and hydrolysis time over the reaction kinetics of hydroalcoholic solutions were studied. In a second step, PP/SiO₂ composites were successfully processed using an internal mixer. Results show a strong correlation between the obtained morphologies and dielectric properties. The transfer of this mechanism to reactive extrusion was carried out and will be discussed in detail.

This study contains the mechanical performance of hybrid-filled thin electrically conductive polypropylene (PP) films using a filler mixture of multi-walled carbon nanotubes (MWCNTs) and carbon black (CB). Essential for use as separator foil in battery applications [1] is that MWCNTs orientate strongly in the extrusion direction so that no or only low conductivity can be achieved through the film [2]. An additional used CB as a second filler solves this drawback because of its non-orientation during the extrusion process due to its spherical shape, resulting in interconnections between the CNTs. Different wt% admixtures of MWCNT and CB were used to affect the conductivity properties. Fundamental to the application is, besides the filler impact on the mechanical properties, how the mechanical load affects the conductivity, see Figure 1. Both effects are evaluated in flow- and perpendicular to the flow-direction using conductive measurements during tensile tests of thin films. Core findings are a generally observed reduction in the mechanical key parameters depending on the admixtures of MWCNT and CB for the extruded films. Thin films are sensitive to added fillers observed as Young’s modulus reduction compared to the pristine unfilled PP film, but also a robust and intact conductive percolation network up to the highest stress in the system.

Figure 1 Stress-Strain curve in relationship to the resistance with low resistance values at low strain values and an increase beyond a critical strain value representing the sample necking, which defines the limits of mechanical load to the conductive percolation network

Fibre reinforced polymer composites (FRPs) are used for a wide variety of applications, including wind turbine blades, boats and automobiles. However, the vast majority are synthesised using non-renewable feedstocks, and due to a lack of recycling technologies, large quantities of waste are created at their end-of-life. FRPs generally have a thermosetting matrix, limiting their reprocessability and recyclability, but alternative thermosets that offer greater value at end-of-life are those containing dynamic cross-links, which undergo reversible exchange reactions or are chemically depolymerisable. We have developed both cross-linked polyester that achieve these goals, thus are more sustainable. We have also made progress in developing an epoxy system which holds promise to meet these goals, as well as having improved thermomechanical properties. This contribution will discuss the relationship between monomer and comonomer performance, lay-up procedure (hand lay-up, vacuum assisted resin infusion, hot press) and reinforcement (glass fibre, carbon fibre) to tune composite performance.

In this talk, we report the rheological response of suspensions of fumed silica colloids dispersed in a solution of high-molecular-weight polyacrylamide. The solvent is a mixture of water and glycerol. The colloids are fractal, unbreakable aggregates with an average size of 300 nm. This unique microstructure enables high effective colloidal volume fractions, while maximizing polymer adsorption on their high specific surface area.
Using extensive rheometry coupled with Ultra-Small Angle X-ray Scattering (USAXS), we show that these suspensions properties are strongly dependent on composition, aging, and memory effects. This interplay results in a competition between two irreversible gelation pathways. The first pathway involves spontaneous gelation during aging, which can be well described by a percolation model. The second pathway arises from a shear-induced gelation transition, whose characteristics depends on the sample's aging time. At short aging times, the suspension displays reversible shear-thickening, similar to equilibrium systems. At intermediate aging times, however, the suspension undergoes an irreversible shear-thickening transition as the shear rate increases. Thorough analysis of the USAXS spectra measured during this transition reveals that a pre-existing, loosely flocculated structure - formed during aging - extends under shear, as evidenced by anisotropic scattering patterns.
Our work highlights the need to link the time-dependent properties of these systems to a deeper understanding of polymer coil collapse dynamics at the colloidal interfaces. Furthermore, this interplay between these competing gelation pathways presents a novel approach for tuning the rheological properties of colloidal gels.