We report a water-based spinning process to produce polyvinyl alcohol (PVA)-carbon nanotube composite fibers that contain a large fraction of nanotubes. The process differs from previous methods to achieve related materials because the spinning solution is injected in a static coagulation bath instead of being circulated in coflowing streams. The resultant wet spinning process is reminiscent of processes industrially developed for neat PVA fibers. Considering its robustness, the process is therefore expected to be easily scalable for greater production. The present method is based on the stabilization of nanotubes by appropriate surfactant molecules that allow the nanotubes to remain homogeneously dispersed in aqueous solutions of PVA. The obtained fibers are homogeneous, uniform in diameter, and can be spun indefinitely. They are electrically conductive and potentially useful for conducting textile applications. The present process being based on the colloidal stability of the particles in PVA solutions, it is believed that it could be extended to several other types of composite PVA fibers provided that the particles are stabilized by similar surfactants. V C 2011Wiley Periodicals, Inc. J Appl Polym Sci 125: E191-E196, 2012

Lignin is a promising bio‐based precursor for sustainable carbon fibers. Limiting factors for their development include the brittleness of lignin and the lack of large‐scale production routes. Here, a simple and economic wet‐spinning method, suitable for the fabrication of fibers based on softwood Kraft lignin (KL) and polyvinyl alcohol (PVA), is proposed. These two polymers reveal a partial miscibility in solution, and form metastable dispersions in solid state. KL‐PVA fibers are prepared at a weight ratio of 70:30 and are carbonized without thermo‐stabilization. A tailor‐made temperature program leads to a decreased microporosity on the fiber surfaces. The obtained carbon structures at 1000 °C are found to be poorly ordered, leading to only intermediate mechanical and electrical properties. However, graphitic domains appear at temperatures above 1500 °C and indicate a high potential for the system.

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The aim was to improve the processability and reduce the melt viscosity of well‐known nanocomposites based on polyamide 66 (PA66) and carbon nanotubes (CNT), while keeping the good electrical conductivity gained after the addition of CNT. Thus, a nanocomposite based on PA66 as the thermoplastic matrix and 3% of CNT was selected. At this composition, a percolated network is created and the material is electrically conductive. The approach followed was the addition of graphene nanoplatelets (GNP) of two different lateral sizes to obtain a PA66 nanocomposite with hybrid filler: CNT/GNP. In addition, a third nanocomposite of PA66 with GNP only was prepared for comparison purposes. The rheological characterization determined that adding 1% of GNP of 2 μm particle size decreased the viscosity of the system by 87%. However, the electrical conductivity was diminished to some extent, from 10−5 to 10−9 S cm−1 approximately. The Cross rheology model described successfully the experimental rheological data. The CNT/GNP nanocomposite exhibited faster relaxations, almost four orders of magnitude, in comparison with the CNT nanocomposite but slower than the GNP nanocomposite. The nanoparticles improved the crystallization ability of PA66 acting as nucleating agents and increasing the PA66 crystallization temperature by almost 10 °C. Self‐nucleation experiments demonstrated a supernucleation feature of the hybrid filler. The nucleation efficiency was about 500%. © 2021 Society of Chemical Industry

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In this work, different amounts of CNFs were added into a complex formulation to coat the CFs surfaces via sizing in order to enhance the bonding between the fibre and the resin in the CF-reinforced polymer composites. The sized CFs bundles were characterised by SEM and Raman. The nanomechanical properties of the composite materials produced were assessed by the nanoindentation test. The interfacial properties of the fibre and resin were evaluated by a push-out method developed on nanoindentation. The average interfacial shear strength of the fibre/matrix interface could be calculated by the critical load, sheet thickness and fibre diameter. The contact angle measurements and resin spreadability were performed prior to nanoindentation to investigate the wetting properties of the fibre. After the push-out tests, the characterisation via optical microscopy/SEM was carried out to ratify the results. It was found the CFs sizing with CNFs (1 to 10 wt%) could generally increase the interfacial shear strength but it was more cost-effective with a small amount of evenly distributed CNFs on CFs.

Three multifunctional smart composites for next-generation applications have been studied differently through versatile nanoindentation investigation techniques. They are used in order to determine peculiarities and specific properties for the different composites and to study the charge/matrix, charge/surface, or smart functions interactions. At first, a mapping indentation test was used to check the distribution of hardness and modulus across a large region to examine any non-uniformity due to structural anomalies or changes in properties for a carbon nanotubes (CNTs)-reinforced polypropylene (PP V-2) nanocomposite. This smart composite is suitable to be used in axial impeller fans and the results can be used to improve the process of the composite produced by injection moulding. Secondly, the interfacial properties of the carbon fibre (CF) and the resin were evaluated by a push-out method utilizing the smaller indentation tip to target the individual CF and apply load to measure its displacement under loads. This is useful to evaluate the effectiveness of the surface modification on the CFs, such as sizing. Finally, nanoindentation at different temperatures was used for the probing of the in situ response of smart shape memory polymer composite (SMPC) usable in grabbing devices for aerospace applications. Furthermore, the triggering temperature of the shape memory polymer response can be determined by observing the change of indentations after the heating and cooling cycles.

In this work, the carbon fibres (CFs) surfaces were modified via sizing and coated with a very thin layer of a complex formulation including carbon nanotubes (CNTs). A push-out method was developed based on nanoindentation to assess the interfacial shear strength of the fibre/matrix. The mechanical properties such as indentation hardness, reduced modulus, indentation displacement and indentation creep of the composite were evaluated by means of the Oliver-Pharr method. The critical load of different composites was measured and the interfacial shear strength (IFSS) was calculated to compare the effect of the CNTs concentration in the sizing solution. Wettability evaluation of the sized fibres was performed prior to nanoindentation to investigate the adhesion of the resin. After push-out testing, characterisation by optical microscopy/SEM was carried out to ratify the results. It was found sizing with a small amount of evenly distributed nano-inclusion on CFs can increase the interfacial shear strength but large amount of sizing could lead to a decrease of the interfacial bonding due to the agglomeration of CNTs on CFs.