Wicking properties of polyamide nanofibrous structures

The hydrophilicity of nanofibrous structures is a key characteristic for many applications. However due to the high porosity of the structures, it is difficult to measure this property with contact angle measurements. Therefore a characterisation through wicking behaviour is more appropriate. The ISO-norm on wicking behaviour needs some refining to account for the specific nature of the highly porous nanofibrous structures. This refined method is used on polyamide 6 nanofibrous structures with different diameters and on polyamide 6 nanofibres with an incorporated hydrophilic compound. It was found that the fibre diameter is the major characteristic which influences the wicking behaviour

Development and characterization of protein nanohydrogels for food applications

Fundação para a Ciência e Tecnologia, POPH-QREN and FSE (FCT, Portugal)EU Cost Actions FA090

Modifying the crack growth in a glass fiber reinforced epoxy by adding polyamide 6 nanofibers

Recently, several types of nanoparticles are frequently incorporated in reinforced epoxy resin composites. Since it is difficult to obtain a homogeneous dispersion of these nanoparticles, the mechanical improvement of the composites is very moderate. Thermoplastic nanofibrous structures can overcome this issue. Therefore, this paper investigated the effect of electrospun polyamide 6 nanofibrous structures on the mechanical properties of a glass fiber/epoxy composite. The nanofibers are incorporated in the glass fiber/epoxy composite as stand-alone interlayered structures and directly spun on the glass fiber reinforcement. Both incorporation procedures have no negative effect on the impregnation of the epoxy. Incorporation of nanofibers increases the stress at failure in the 0°-direction, the best results are obtained when the nanofibers are directly electrospun on the glass fibers. Optical microscopic images also demonstrate that nanofibers prevent delamination when a 90° crack reaches a neighbourly 0° ply. When the composites are loaded under 45°, it is proven that for an identical stress, the glass fiber composite with deposited nanofibers has less cracks than when interlayered nanofibrous structures are incorporated

The influence of nanofibres in composite materials

Nanofibres have by definition a diameter less than 500 nm, which is several times smaller than the conventional fibres. Because of their very small fibre diameter these fibrous materials have specific and unique characteristics such as a high surface-to-volume ratio and high porosity. Thanks to this these nanofibres can be used in a broad spectrum of applications such as liquid and air filtration, wound bandages and composites. Although the literature on nanofibre composites is restricted, nanofibres can have advantages for advanced composites. Composites reinforced with conventional glass or carbon fibres may have very high tensile strengths, but the impact resistance is sometimes limited. A second problem of these actual composites is the delamination of the several textile layers. Both problems can be reduced by using nanofibrous webs between the glass or carbon layers. In our research large polyamide nanofibrous structures (PA 6, PA6.6, PA 4.6 and PA 6.9) were produced on a multi-nozzle setup. Starting from these structures the effect of the nanofibres on the curing of a epoxy matrix was investigated by thermo analytical measurements using a differential scanning calorimeter. Changing the nanofibres characteristics, especially the polyamide type and fibre diameter, will affect the curing behaviour of the resin. Furthermore the influence of the amount of water absorbed through the nanofibrous webs is inquired, by making identical composite samples at different relative humidity’s. In the second part of the research glass fibre/polyamide nanofibre composites were produced on large scale by infusion. The polyamide nanofibres were brought into the composites as stand-alone structures as well as coatings on the glass fabrics. The tenacity of these composites is compared to glass fibre composites without nanofibres. This research gives a good overview of the curing behaviour of the resin affected by the nanofibrous webs on the one side and the advantages of nanofibres for high performance composites on the other side