Joanna C.H. Wong

Controlling Phase Distributions in Macroporous Composite Materials through Particle-Stabilized Foams

Aqueous foams stabilized by ceramic and thermoplastic polymeric particles provide a general method for producing novel porous materials because their extraordinary stability against disproportionation and drainage allows them to be dried and sintered into solid materials. Here, we report the different microstructures that can be obtained from liquid foams stabilized by binary mixtures of particles when the interfacial energies between the particles and the air-liquid interfaces are manipulated to promote either preferential or competitive self-assembly of the particles at the foam interface. Modification of the interfacial energies was accomplished through surface modification of the particles or by decreasing the surface tension of the aqueous phase. Materials derived from liquid foams stabilized by poly(vinylidene fluoride) (PVDF) and alumina (Al(2)O(3)) particles are investigated. However, as is shown, the method can be extended to other polymeric and ceramic particles and provides the possibility to manufacture a wide range of porous composite materials.

Designing macroporous polymers from particle-stabilized foams

Particle-stabilized liquid foams provide a general route for producing low-density macroporous materials from melt-processable and intractable thermoplastic polymers. In this paper, we demonstrate how these liquid foams can be used to design macroporous polymers with tailored microstructures and properties by adjusting the various processing parameters. By varying the size, concentration, and wettability of the particles in the colloidal suspensions and controlling the frothing, drying, and sintering conditions, macroporous materials with porosities between 33 and 95% and median pore sizes (D50) between 13 and 634 μm were obtained. This foaming process is applicable to a wide range of hydrophobic materials and is demonstrated here on commercially available polymeric powders of poly(tetrafluoroethylene) (PTFE), poly(vinylidene fluoride) (PVDF), poly(ether imide) (PEI), and poly(ether ether ketone) (PEEK).

Engineering macroporous composite materials using competitive adsorption in particle-stabilized foams.

The high absorption energies of partially wetted particles at fluid interfaces allow the production of macroporous composite materials from particle-stabilized foams. Competition between the different particle types determines how they are distributed in the foam lamella and allow the phase distribution to be controlled; a technique that is useful in the design and engineering of porous composites. Here, we report details on the effects of preferential and competitive adsorption of poly(vinylidene fluoride) (PVDF) and alumina (Al(2)O(3)) particles at the foam interfaces on the consolidated macroporous composite materials. By varying the relative composition and surface energies of the stabilizing particles, macroporous composite materials with a broad range of phase distributions are possible.

Filament winding of aramid/PA6 commingled yarns with in situ consolidation:

The in situ consolidation of commingled yarns during filament winding is demonstrated on an aramid fibre-reinforced polyamide 6 material. This article is a systematic experimental investigation of the filament winding processing parameters, namely, the heat gun temperature, line speed, fibre tension, compaction force and preheater temperature. Optimizing the processing parameters in this filament winding process produced a fully consolidated material with a void content of ∼0.25% which is comparable to the material quality achieved by means of compression moulding using the same intermediate materials.