Porous Monofilaments by Continuous Solid-State Foaming

Fabrication of Mesoporous Polystyrene Films with Controlled Porosity and Pore Size by Solvent Annealing for Templated Syntheses

Herein, we aim to develop a facile method for the fabrication of mesoporous polystyrene (PS) films with controlled porosity and pore size by solvent annealing. A PS polymer film is solvent-annealed using N,N-dimethyl formamide (DMF) vapor for the development of phase separation, followed by rapidly cooling to the preset cryogenic temperature. Subsequently, a nonsolvent (methanol) is introduced to extract the crystalline DMF from the DMF-swollen PS, giving mesoporous PS with a network structure after the removal of DMF. The porosity of the mesoporous PS films can be controlled by the degree of swelling. Most interestingly, the phase separation between PS and DMF at the thin-film state under solvent annealing can be regulated by the annealing time through the spinodal decomposition, giving the development of nanonetwork structure with controlled structural features (i.e., framework size and interframework spacing) at invariant porosity. Consequently, after the removal of DMF, mesoporous PS films with controlled porosity and pore size can be obtained and then used as a template for the fabrication of a variety of nanoporous inorganics by templated syntheses, such as nanoporous SiO₂, TiO₂, and Ni, providing a cost-effective way to fabricate a range of nanoporous materials with controlled porosity and pore size as well as large specific surface area for aimed applications.

Thermoplastic polyurethane/clay nanocomposite foam made by batch foaming

In this study, the foaming of nonwoven fabrics and bulk polymers was investigated. Four different polymers that are commonly used for textiles including polyethylene terephthalate, thermoplastic polyurethane, thermoplastic polyether ester elastomer and polypropylene were foamed by batch foaming. Among the polymers, thermoplastic polyurethane seems to be the most promising material since it possesses the highest cell density and smallest cell size. In addition, nanoclay was added to thermoplastic polyurethane to promote cell nucleation and to increase the cell density. The results showed that well dispersed nanoclay in thermoplastic polyurethane served as an excellent nucleation agent and the cell structure was improved. The cell size of thermoplastic polyurethane nanocomposite foam decreased to 1 µm while the cell density increased to 3 × 1011 cells/cm3.