Feasibility Study of Plasma Treatment of Clays and Polymers for Nanocomposite Manufacture by Laser Sintering

Additive Manufacturing (AM) describes a powerful set of techniques which have the potential to become a reliable method for the manufacture of complex and accurate parts. Laser Sintering (LS) is one of the most promising AM techniques, capable of manufacturing 3-dimensional (3D) products from polymer powders. However, some key challenges still limit their widespread applications. The most common key challenges, specifically for the Laser Sintering AM process are limited availability of different materials, inconsistent or poor mechanical properties and surface quality, each of which is currently still restricting the functions of the end-use parts. In some cases, nanoclay reinforcement of polymers has been shown to provide performance benefits, improving part quality, and offering new applications. However, the dispersion of those nano-sized materials still remains a critical issue for the preparation of Laser Sintering nanocomposites. A novel method of using plasma treatment to tackle these challenges was developed in this study. Plasma treatment was used to increase the surface area of nanoclay particles and with the expectation of simultaneous surface functionalisation aiming for increased homogeneity after dry mixing of polymer and nanoclay powders. SEM images of treated composite powders confirmed this expectation as the plasma treatment reduce agglomerations and improved nanoclay dispersion in the powders. To consolidate these powders into parts a novel methodology, i.e. Downward Heat Sintering (DHS) method was initially used as a powerful replication method for the Laser Sintering technique. DHS process was employed with a hot press to process small quantities of PA12 and dry mixed composite powders into tensile test specimens after optimisation attempts based on differential scanning calorimetry (DSC) and hot-stage microscopy (HSM). SEM images of the heat sintered specimens showed clearly the plasma treatment prevented the aggregation of the nanoclay resulting in an improved elastic modulus of treated composite compared with neat PA12 and untreated composites. Moreover, the reduction in elongation at break for the treated composite was less pronounced than untreated composite. Further work resulted in successfully LS parts with different complex and accurate shapes. No significant deterioration in LS processibility was observed and complex LS parts could be produced when including the plasma treated nanoclay. SEM images of the cross-sections of the fabricated parts that the layer by layer structure were successfully consolidated and relatively uniform. In addition, the introduction of the plasma treated nanoclay was found to improve the elastic modulus of the LS composite parts. Most notably however, a substantially improved surface quality in part’s appearance and microstructure was found as a result of incorporating plasma treated nanoclay compared to the nontreated nanoclay. PA12 exposed to Low Pressure Air Plasma Treatment showed an increase in wettability, was relatively porous, and possessed a higher density, which resulted from surface functionalisation and materials removal during the plasma exposure. However, it showed poor melt behaviour under heating conditions typical for Laser Sintering. In contrast, brief Plasma Jet treatments demonstrated similar changes in porosity, but crucially, retained the favourable melt characteristics of PA12 powder. To summarise, this is a unique study on the use of plasma treatment and polymer/polymer nanocomposites in LS applications, demonstrating for the first time that plasma treatment has the potential to provide crucial performance benefits for laser sintered nanocomposites

Surface modification of the laser sintering standard powder polyamide 12 by plasma treatments

Polyamide 12 (PA12) powder was exposed for up to 3 h to low pressure air plasma treatment (LP-PT) and several minutes by two different atmospheric pressure plasma jets (APPJ) i.e., kINPen (K-APPJ) and Hairline (H-APPJ). The chemical and physical changes resulting from LP-PT were observed by a combination of Scanning Electron Microscopy (SEM), Hot Stage Microscopy (HSM) and Fourier transform infrared spectroscopy (FTIR), which demonstrated significant changes between the plasma treated and untreated PA12 powders. PA12 exposed to LP-PT showed an increase in wettability, was relatively porous, and possessed a higher density, which resulted from the surface functionalization and materials removal during the plasma exposure. However, it showed poor melt behavior under heating conditions typical for Laser Sintering. In contrast, brief PJ treatments demonstrated similar changes in porosity, but crucially, retained the favorable melt characteristics of PA12 powder

Surface modification of the laser sintering standard powder polyamide 12 by plasma treatments

Polyamide 12 (PA12) powder was exposed for up to 3 h to low pressure air plasma treatment (LP-PT) and several minutes by two different atmospheric pressure plasma jets (APPJ) i.e., kINPen (K-APPJ) and Hairline (H-APPJ). The chemical and physical changes resulting from LP-PT were observed by a combination of Scanning Electron Microscopy (SEM), Hot Stage Microscopy (HSM) and Fourier transform infrared spectroscopy (FTIR), which demonstrated significant changes between the plasma treated and untreated PA12 powders. PA12 exposed to LP-PT showed an increase in wettability, was relatively porous, and possessed a higher density, which resulted from the surface functionalization and materials removal during the plasma exposure. However, it showed poor melt behavior under heating conditions typical for Laser Sintering. In contrast, brief PJ treatments demonstrated similar changes in porosity, but crucially, retained the favorable melt characteristics of PA12 powder

Patent foramen ovale closure in young Patients with cryptogenic stroke: a case series and follow up from Saudi population.

One quarter of cerebral infarctions are cryptogenic and most of these patients are young. Patent Foramen Ovale (PFO) is found to be more prevalent in young persons with cryptogenic stroke and risk of stroke recurrence in such patients ranges from as low as 2% per annum to as high as 12% per annum. Since patients with PFO and cryptogenic stroke are young they need more effective ways to reduce risk of stroke recurrence hence percutaneous closure of PFO seems reasonable approach to deal with this etiology of stroke in such population. We report four cases of cryptogenic stroke in young Saudi patients. PFO closure was performed in all. After closure, none of them developed either recurrence of symptoms or any complication on follow up for more than one year

Scanning electron microscopy as a valuable tool to optimize the properties of the polymer/clay nanocomposites

AbstractThe current research utilizes a low voltage scanning electron microscopy (LV-SEM) with an electron beam along with low loading energy of lower than 2.2 KeV to minimize damage and specimen surface charging. The NovaSEM, is used as an efficient tool in the current study due to the high resolution information it can gather as images and its high magnification nanometers. Polyamide 12 (PA12), as a polymer matrix, and Cloisite 30B (C30B) nanoclay, as a filling material, were the materials tested in this study. From the results obtained, CBS was found to be a significant and valuable tool for certain complex tasks when studying and analyzing polymer/clay interfaces. CBS in conjunction with beam deceleration in a LV-SEM was used to map the C30B clay distribution on PA12 particles and within PA12-nanoclay nanocomposites manufactured from the latter’s clay distribution particles within the polymer particles’ surfaces. This SEM experimentation has demonstrated that using the clay’s air plasma design preceding the composite preparation resulted in removing the large clay assemblages. The plasma treatment has improved the interfacial adhesion and dispersion in the nanoclay/PA12 composite, resulting in similar maximum stress values which were both higher than the pure PA12. Thus, the mechanical tests exhibited performance enhancement for the resulting composites defined in the present work, and the enhancement of this method can be identified via SEM imaging

Tensile test results of Nylon12 and its composites (3% and 5% of nanoclay)

<p> </p><p></p><p> <br></p><p>Tensile test raw data. </p><p>Tensile test was done to examine the effect of nanoclay (with different processing: NEC or EC) on the mechanical properties of Nylon 12. </p><p>The attached data are for Neat Nylon12, 3%NEC+Nylon12, 3%EC+Nylon12, 5%NEC+Nylon12, and 5%EC+Nylon12. It includes: (Force, displacement) and (stress-strain) raw data. The conditions for my data are always normal (room temperature).</p><p> And all the test specifications are shown in the paper I would publish the test results for. </p><p>However, the paper is not published yet.</p><p> <br></p><p> </p><p></p><p><br></p><p> <br></p