Electro-active nanofibres electrospun from blends of poly-vinyl cinnamate and a cholesteric liquid crystalline silicone polymer

Electrospinning was used to generate polymer nanofibres from blends of poly-vinyl cinnamate (PVCN) and a cholesteric silicone polymer. Only blends that contained at least 40 % of PVCN produced fibres. Both differential scanning calorimetry and electron dispersion spectroscopy data indicate that the samples are miscible over a wide temperature interval. The variation of fibre diameter with concentration is nonlinear with a well-defined minimum corresponding to an 80 % PVCN blend. The fibres are birefringent with Kerr constants similar to that of cholesteric liquid crystals. Although not significant, the Kerr constant increases with increasing silicone polymer concentration

Modifying the thermomechanical properties of electrospun fibres of poly‑vinyl cinnamate by photo‑cross‑linking

We explore the effects of cross-linking on some thermal and mechanical properties of polymer nanofibers of poly-vinyl cinnamate which were electro-spun from 1,2 dichloroethane. Scanning electron microscopy performed on the fibres revealed smooth fibres which were devoid of beading or ribbon-type features. When cross-linked, the Young’s moduli and glass transition temperatures of the fibres increase, owing to the formation of new covalent bonds which leads to higher overall binding energies. The glass transition temperatures increased by 20 K after 1 h of photo-polymerization while the Young’s modulus increased by 50% for the same exposure time. The glass transition temperatures as well as the heats of enthalpy indicate that a significant portion of cross-linking occurs within the first 10 min of exposure

Highly Anisotropic Polymer Composites Based on Carbon Nanotubes

Properties of polymers can be optimized through processing methods or by the addition of nanofillers. Carbon nanotubes (CNTs) have gained attention due to their promising behavior. Carbon nanotubes are essentially a sheet of graphene wrapped into a cylindrical shape with either a single or multiple walls. Tube diameters are approximately nanometres, but they can be micrometres in length. Due to the unique properties of nanotubes, they offer promise in composite materials with current research dedicated to embedding them in a polymer matrix. If improvements are to be made, the nanotubes need to be in an aligned configuration. This presents challenges due to the strong intermolecular forces that cause nanotube agglomeration leading to poor quality dispersion and random CNT orientations. Thus, there are two particular challenges to the formation of polymer composites based on CNTs: dispersion and alignment, and these are the focus of this chapter. We consider recent developments in the synthesis of carbon nanotubes and their properties. Next, we detail the challenges of dispersion and alignment that are presented in the preparation of polymer/CNT composites. Finally, we review the literature to identify progress made in preparing high performance polymer/CNT composites and their properties and present one particular solution

Carbon nanotubes in electrospun polyethylene oxide nanofibres: a potential route to conducting nanofibres

Polyethylene oxide solution containing multi-walled carbon nanotubes have been electrospun onto a rotating collector to produce highly aligned arrays of electrospun nanofibers ranging in diameters from (200 – 360) nanometres. The addition of a surfactant (Triton X-100)is highly effective in dispersing carbon nanotube within an aqueous solution of polyethylene oxide and the resulting mixture can be electrospun without excessive clumping to produce nanofibers containing high loadings of nanotubes; in this case up to 5% wt thereby providing an effective route to electrically conductive nanofibres

New tools for understanding complex polymer behaviour

The process of manufacturing with polymers usually involves shaping in the melt followed by a transition to the solid to preserve that shape and provide the required mechanical properties. The development of an understanding of those transitions is critical to the optimisation of materials and manufacturing technology. For synthetic polymers there are three key length scales in any phase transition such as crystallisation: the first involves the thin (∼10 nm) lamellar crystals, the second is the crystal planes in the unit cell (∼1 nm) and the third the regular local chain conformation (∼0.1 nm). We are using the extended Q range available with NIMROD at the ISIS Facility in the UK to obtain neutron scattering data which follows the transformation pathways of these three length scales simultaneously. We are using computational modelling procedures to analyse these data to develop a firm understanding of the multiscale processes involved in crystallisation. This paper describes the methodology and some of the experimental challenges using data drawn from this stud

Electrospinning of food-grade nanofibres from whey protein

In this study, electrospinning has been employed to produce micro to nano scale fibres of whey protein in order to investigate their potential for use in the food industry. Initially, spinning of purewhey protein proved challenging; so in order to facilitate the spinning of freshly prepared aqueous solutions, small amounts of polyethylene oxide (as low as 1% w/w in solution) were incorporated in the spinning solutions. The electrospun composite polyethylene-oxide/whey fibres exhibited diameters in the region of 100 to 400 nm, showing the potential to build fibre bundles from this size up. Time-dependent examinations of pure whey protein aqueous solutions were conducted using rheometery and small angle neutron scattering techniques, with the results showing a substantial change in the solution properties with time and stirring; and allowing the production of fibres, albeit with large diameters,without the need for an additive. The spinability is related to the potential of thewhey protein composites to form aggregate structures, either through hydration and interaction with neighbouring proteins, or through interaction with the polyethylene oxide

The exploitation of polymer based nanocomposites for additive manufacturing: a prospective review

Additive manufacturing (AM) is a well-known technology for making real three dimensional objects, based on metal, ceramic and plastic material used for various applications. The aim of this review is to explore and offer an insight in to the state of the art polymer based nanocomposites in to additive manufacturing applications. In context to this, the developing efforts and trends in nanocomposites development particularly for additive manufacturing processes were studied and summed up. The scope and limitations of nanocomposites into Stereolithography, selective laser sintering and fused deposition modeling was explored and highlighted. The review highlights widely accepted nanoparticles for range of applications including mechanical, electrical, flame retardance and crossing over into more biological with the use of polymer matrices. Acquisition of functional parts with limitations in regard to printing is highlighted. Overall, the review highlights successes, limitations and opportunities that the union of AM and polymer based nanocomposites can bring to science and technology

Compressive response of vertically aligned carbon nanotube films gleaned from in situ flat-punch indentations

We report the mechanical behavior of vertically aligned carbon nanotube films, grown on Si substrates using atmospheric pressure chemical vapor deposition, subjected to in situ large displacement (up to 70 μm) flat-punch indentations. We observed three distinct regimes in their indentation stress–strain curves: (i) a short elastic regime, followed by (ii) a sudden instability, which resulted in a substantial rapid displacement burst manifested by an instantaneous vertical shearing of the material directly underneath the indenter tip by as much as 30 μm, and (iii) a positively sloped plateau for displacements between 10 and 70 μm. In situ nanomechanical indentation experiments revealed that the shear strain was accommodated by an array of coiled carbon nanotube “microrollers,” providing a low-friction path for the vertical displacement. Mechanical response and concurrent deformation morphologies are discussed in the foam-like deformation framework with a particular emphasis on boundary conditions

Direct digital manufacturing of nanocomposites

Additive manufacturing has surged in popularity as a route to designing and preparing functional parts. Depending on the parts function, certain attributes such as high mechanical performances may be desired. We develop a route for improving the mechanical properties of polymer devices, fabricated through additive manufacturing by combining electrospinning and stereo-lithography into one automated process. This process utilises the impressive mechanical properties of carbon nanotubes by encapsulating and aligning them in electrospun fibres. Composite fibres will be incorporated into polymer resins prepared with stereo-lithography, thereby providing resins that benefit from the composite fibres properties, enhancing their overall mechanical properties

Rosin Based Composites for Additive Manufacturing

Acknowledgements: This work is supported by the Fundação para a Ciência e a Tecnologia (FCT) and Centro2020 through the Project references: UID/Multi/04044/2013; PAMI – ROTEIRO/0328/2013 (Nº 022158) and MATIS (CENTRO-01-0145-FEDER-000014 – 3362).Rosins are the non-volatile exudates of pine resins with hydrophobic characteristics that are widely used as a precursor for many industrial applications. In this paper we discuss the nature, process and its applications as a matrix for a composite material for additive manufacturing. The composite material has been tailored to chemical and mechanical properties with respect to their applications.info:eu-repo/semantics/publishedVersio