Browsing by Author "Pielichowski, Krzysztof"

Now showing 1 - 9 of 9
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    The effect of nanoclay on dust generation during drilling process of polyamide 6 nanocomposites
    (Hindawi Publishing Corporation, 2012-06-10T00:00:00Z) Sachse, Sophia; Silva, Francesco; Zhu, Huijun; Irfan, Adeel; Leszczynska, Agneska; Pielichowski, Krzysztof; Ermini, Valentina; Blazquez, Maria; Kuzmenko, Oleksandr; Njuguna, James A. K.
    During the past decade, polymer nanocomposites have emerged as a novel and rapidly developing class of materials and attracted considerable investment in research and development worldwide. However, there is currently a lack of information available in the literature on the nano and ultrafine particle emission rates from these materials. In this study, influence of nanoclay on mechanical drilling of PA6 composites, in terms of dust generation has been reported. With the help of real-time characterization, submicrometer-sized particles (5.6-512 nm) size distribution and number concentration emitted from polyamide 6/nanoclay composites during mechanical drilling is studied. Total particle concentration for the PA6/nanoclay composites was 20,000 cm-3, while unreinforced panel measured a total concentration of approximately 400,000 cm-3. While the airborne particle concentration for the PA6/ nanoclay composites was 20 times lower than for the PA6 matrix, the concentration of deposited nanoparticles doubled for the nanocomposite. The results clearly shows that more particles in the size range between 175-350 nm are generated, during drilling of the nanocomposites and this particles deposit in a shorter time. It is likely that the presence of nanoclay in some way retains the formation of high quantity of airborne particles and promotes particle deposition.
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    Epoxy-based fibre reinforced nanocomposites
    (John Wiley & Sons, Ltd, 2007-10-31T00:00:00Z) Njuguna, James A. K.; Pielichowski, Krzysztof; Alcock, Jeffrey R.
    The modification of epoxy resins with nanoparticles could endow the materials with some superior properties such as broadening of the glass transition temperatures, modest increases in the glassy modulus, low dielectric constant, and significant increases in key mechanical properties. In the last 15 years, some studies have shown the potential improvement in properties and performances of fibre reinforced polymer matrix materials in which nano and micro-scale particles were incorporated. From the existing literature, considerable effort has been given to the synthesis and processing of these unique polymers, but relatively little work has focused on the fibre reinforced epoxy composites. The purpose of this work, therefore, is to review the available literature in epoxy- fibre reinforced composites manufactured using carbon nanotubes, carbon nanofibre and nanoclays for reinforcement.
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    Fabrication, Characterization and low-velocity impact testing of hybrid sandwich composites with polyurethane/layered silicate foam cores
    (John Wiley & Sons, Ltd, 2011-01-31T00:00:00Z) Njuguna, James A. K.; Michalowski, Slawomir; Pielichowski, Krzysztof; Kayvantash, Kambiz; Walton, A. C.
    A series of nanophased hybrid sandwich composites based on polyurethane/montmorillonite (PU/MMT) has been fabricated and characterised. Polyaddition reaction of the polyol premix with 4,4'-diphenylmethane diisocyanate was applied to obtain nanophased polyurethane foams which were then used for fabrication of sandwich panels. It has been found that the incorporation of MMT resulted in higher number of PU cells with smaller dimensions and higher anisotropy index (cross-sections RI and RII). The obtained materials exhibited improved parameters in terms of thermal insulation properties. The results also show that nanophased sandwich structures are capable of upholding withstanding higher peak loads than those made of neat polyurethane foam cores when subject to low-velocity impact despite lower density than that of neat PU foams. This is especially significant for multi-impact recurrences within the threshold loads and energies studied.
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    The Influence of Multiscale Fillers Rein forcement into Impact Resistance and Energy Absorption Properties of Polyamide 6 and Polypropylene Nanocomposite Structures
    (2013-09-01T00:00:00Z) Silva, Francesco; Njuguna, James A. K.; Sachse, Sophia; Pielichowski, Krzysztof; Leszczynska, Agneska; Giacomelli, Marco
    Three-phase composites (thermoplastic polymer, glass-fibres and nano-particles) were investigated as an alternative to two-phase (polymer and glass-fibres) composites. The effect of matrix and reinforcement material on the energy absorption capabilities of composite structures was studied in details in this paper. Dynamic and quasi-static axial collapse of conical structures was conducted using a high energy drop tower, as well as Instron universal testing machine. The impact event was recorded using a high-speed camera and the fracture surface was investigated with scanning electron microscopy (SEM). Attention was directed towards the relation between micro and macro fracture process with crack propagation mechanism and energy absorbed by the structure. The obtained results indicated an important influence of filler and matrix material on the energy absorption capabilities of the polymer composites. A significant increase in specific energy absorption (SEA) was observed in polyamide 6 (PA6) reinforced with nano-silica particles and glass-spheres, whereas addition of montmorillonite (MMT) caused a decrease in that property. On the other hand, very little influence of the secondary reinforcement on the energy absorption capabilities of polypropylene (PP) composites was found.
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    Integration of polymer nanocomposites technologies for automotive applications: opportunities and environmental health challenges
    (2008-05-14T00:00:00Z) Njuguna, James A. K.; Peña, I.; Zhu, H.; Rocks, Sophie A.; Blazquez, Maria; Desai, S. A.; Pielichowski, Krzysztof
    The concept of nanostructured materials design is gaining widespread importance among the automotive industry. Although employment of nanotechnology in current and future automotives will go long way in solving energy crises, it is necessary to understand both the hazards associated with nanomaterials and the levels of exposure that are likely to occur. The existing knowledge in these areas is quite limited and it will be necessary in the near future. This paper highlights these key issues and goes a long way in pointing recent activities on environmental risks of nanomaterials. Some research directions are given and existing automotive opportunities and applications explored.
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    Nanofiller Fibre-Reinforced Polymer Nanocomposites
    (John Wiley & Sons, Ltd, 2008-06-09T00:00:00Z) Njuguna, James A. K.; Pielichowski, Krzysztof; Desai, S.
    In this work, the technology of nano and micro-scale particle reinforcement concerning various polymeric fibre-reinforced systems including polyamides (PA), polyesters, polyurethanes, polypropylenes and high performance/temperature engineering polymers such as polyimide (PI), poly(ether ether ketone) (PEEK), polyarylacetylene (PAA) and poly p-phenylene benzobisoxazole (PBO) is reviewed. When the diameters of polymer fibre materials are shrunk from micrometers to submicrons or nanometers, there appear several unique characteristics such as very large surface area to volume ratio (this ratio for a nanofibre can be as large as 103 times of that of a microfibre), flexibility in surface functionalities and superior mechanical performance (such as stiffness and tensile strength) compared with any other known form of the material. However, nanoparticle reinforcement of fibre reinforced composites has been shown to be a possibility, but much work remains to be performed in order to understand how nanoreinforcement results in dramatic changes in material properties. The understanding of these phenomena will facilitate their extension to the reinforcement of more complicated anisotropic structures and advanced polymeric composite systems.
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    Polymer/montmorillonite nanocomposites with improved thermal properties: Part II. Thermal stability of montmorillonite nanocomposites based on different polymeric matrixes.
    (Elsevier Science B.V., Amsterdam., 2007-02-01T00:00:00Z) Leszczynska, Agneska; Njuguna, James A. K.; Pielichowski, Krzysztof; Banerjee, J. R.
    In previous part of this work factors influencing the thermal stability of polymer nanocomposite materials were indicated, such as chemical constitution of organic modifier, filler content, nanocomposites’ structure and the processing- dependent degree of homogenization of nanofiller, were presented. In this part the basic changes in thermal behaviour of different polymeric matrixes (e.g. polyolefins, polyamides, poly(vinyl chloride) and styrene-containing polymers) upon addition of montmorillonite have been described. Brief description of the kinetics of the decomposition process in inert and oxidative environment, as well as analysis of volatile and condensed products of degradation, have also been presente
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    Polymer/montmorillonite nanocomposites with improved thermal properties: Part I. Factors influencing thermal stability and mechanisms of thermal stability improvement.
    (Elsevier Science B.V., Amsterdam., 2007-02-01T00:00:00Z) Leszczynska, Agneska; Njuguna, James A. K.; Pielichowski, Krzysztof; Banerjee, J. R.
    The results of recent research indicate that the introduction of layered silicate – montmorillonite – into polymer matrix results in increase of thermal stability of a number of polymer nanocomposites. Due to characteristic structure of layers in polymer matrix and nanoscopic dimensions of filler particles, several effects have been observed that can explain the changes in thermal properties. The level of surface activity may be directly influenced by the mechanical interfacial adhesion or thermal stability of organic compound used to modify montmorillonite. Thus, increasing the thermal stability of montmorillonite and resultant nanocomposites is one of the key points in the successful technical application of polymer–clay nanocomposites on the industrial scale. Basing on most recent research, this work presents a detailed examination of factors influencing thermal stability, including the role of chemical constitution of organic modifier, composition and structure of nanocomposites, and mechanisms of improvement of thermal stability in polymer/ montmorillonite nanocompo
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    Recent developments in polyurethane-based conducting polymer composites
    (Springer Science Business Media, 2004-07-01T00:00:00Z) Njuguna, James A. K.; Pielichowski, Krzysztof
    Polyurethane-based conducting composites with polyaniline, polythiophene or polypyrrole are in the class of modern macromolecular materials that combine the toughness and elasticity of polyurethane matrix with conductivity of intrinsically conducting polymers. Since the methods of preparation strongly influence the structure and properties of resulting composite/blend, this works aim at systematic description of polyurethane based conducting composites. This review has been structured to present an overview on preparations, characterisation and applications of polyurethane-based conducting materials with polyaniline, polythiophene or polypyrrole.