Developing high performance polymeric nano-composites for tribological applications

Polymers and their composites have been widely applied in different industrial sectors as alternatives to conventional metal-based materials, for the better performance of the system, increasing efficiency and cutting down operational costs. In those applications polymeric materials are sometime subjected to tribological loading conditions where external lubricants are not permissible and polymers’ self-lubricating ability is desirable in such tribo-contacts. In particular, high temperature is often the key factor determining the working conditions of polymers. Hence, high performance polymers (HPPs) have received increasing attention in last decades. In view of above-mentioned facts, the present research investigated the tribological performance of some important engineering polymers and their nanocomposites such as epoxy, PEEK, PPP and PBI. For example, nano-silica (SiO2), nano-rubber (CBTN) and titanium dioxide (TiO2) nano-particles have been incorporated in thermosetting epoxy resin and PEEK, respectively, to improve their tribological properties. To explore the effect of harsh environments during sliding wear, pin-on-disk tests of above-mentioned materials were carried out in dry, wet and elevated temperature regimes. Finally, attempts have been made to establish correlations between the basic mechanical properties of HPPs and their sliding wear behaviour. Various wear models to correlate the tribological aspects of HPPs and polymer nanocomposites with associated mechanical properties were examined along with experimental validation. In addition to that, underlying wear mechanisms were taken into account towards model developments. To develop a quantitative solution for wear prediction, the new computer techniques such as artificial neural network (ANN) may be helpful in the area. Accordingly, the ANN was employed to find the general wear trend of materials

Environmentally Acceptable Friction Composites

This thesis describes the development of a novel friction composite, the properties of its raw ingredients (including a CNSL-based resin and hemp fibre), the manufacturing process used to produce it, the tribological performance of the composite, and its incorporation into railway brake pads for passenger rolling stock.Currently, the production of most non-asbestos organic (NAO) friction materials depends on a long and energy intensive manufacturing process and an unsustainable supply of synthetic resins and fibres; it is both expensive and bad for the environment. In this research, a new, more energy efficient, manufacturing process was developed which makes use of a naturally derived resin and natural plant fibres. The new process is known as 'cold moulding' and is fundamentally different from the conventional method. It was used to develop a new brake pad for use in low temperature (<400 °C) applications, such as rapid urban rail transit (RURT) trains. A commercially available resin based upon cashew nut shell liquid (CNSL) was analysed and found to have properties suitable for cold moulding. In addition, hemp fibre was identified as a suitable composite reinforcement. This was processed to improve its morphology and blended with aramid to improve its thermal stability. Each stage of cold mould manufacture was thoroughly investigated and the critical process parameters were identified. The entire procedure was successfully scaled up to produce an industrially sized 250 kg batch of material and the resultant composites were found to have appropriate thermal and mechanical properties for use in a rail brake pad. The tribological performance of these composites was iteratively developed through a rigorous testing and evaluation procedure. This was performed on both sub- and full-scale dynamometers. By adding various abrasives, lubricants, and fillers to the formulation it was possible to produce a brake pad with similar friction characteristics to the current market material, but with a 60% lower wear rate. In addition, this brake pad caused 15% less wear to the brake disc. A detailed examination of both halves of the friction couple found that cold moulded composites exhibit a different wear mechanism from the current market material, which was suggested to be the reason for their superior properties. Cold moulding is 3.5x faster and uses 400% less energy than the conventional method.Technology Strategy BoardEuropean Friction Industries LtdAptec Products LtdHemp Technology Lt

Polymer Processing and Surfaces

This book focuses on fundamental and applied research on polymer processing and its effect on the final surface as the optimization of polymer surface properties results in the unique applicability of these over other materials. The development and testing of the next generation of polymeric and composite materials is of particular interest. Special attention is given to polymer surface modification, external stimuli-responsive surfaces, coatings, adhesion, polymer and composites fatigue analysis, evaluation of the surface quality and microhardness, processing parameter optimization, characterization techniques, among others

MANUFACTURE AND CHARACTERIZATION OF POLYVINYL CHLORIDE / POLYETHYLENE PVC / PE COMPOSITES FOR STRUCTURAL APPLICATIONS

The research initially studied a safe recycling process that decreases the accumulation of thermoplastic wastes and prevents pollution of the environment. Obtained all composites in these works were analyzed for mechanical, thermal, and morphological dynamical- mechanical and rheological characteristics. This research aims to develop a new polyvinylchloride (PVC) microcomposite that incorporates low density polyethylene (LDPE), calcium carbonate (CaCO3), and calcium/zinc stearate (CaSt2/ZnSt2). The addition of 5 phr of CaSt2: ZnSt2 = 9:1 into PVC appears to yield an optimal mechanical result and shows high thermal stability. Moreover, when a heat stabilizer rich in calcium is mixed with CaCO3 and LDPE, an excellent synergistic effect is demonstrated. The properties of polyvinyl chloride (PVC) and low density polyethylene (LDPE) blends, at three different ratios (20, 50, and 80 wt.%) of renewable LDPE were studied. Besides, Biobased composite with PVC-LDPE blend and date palm fiber as reinforcement at different loading levels (0-30 wt.%) were also investigated. The matrix in which PVC-LDPE (20 wt.%-80 wt.%) had the optimum mechanical and thermal properties. The modulus of the composites is enhanced with increasing DPLF content. Scanning electron microscopic micrographs revealed that morphological properties of fracture surfaces are following the tensile properties of these blends and composites. Thermal analysis showed that the thermal degradation of PVC-LDPE (20 wt.%/80 wt.%) blend and PVC-LDPE-DPLF (10 and 30 wt.%) composites took place in two steps: in the first step, the blend was more stable than the composites. In the second step, the composites showed slightly better stability than the PVC-LDPE (20 wt.%-80 wt.%) blend. Leaflets and rachis fibers (DPFs) were used as a sustainable reinforcement material to strengthen PVC-HDPE (20:80) biocomposites to further study the feasibility of compounding date palm fiber. As this renewable material used in this project work are crop wastes, the fibers had to be pre-treated to eliminate lignin and impurities for enhancing the interfacial adhesion between matrix and fiber, composites with untreated and treated DPFs containing 30 wt% were produced. Infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and thermogravimetric analysis (TGA) have confirmed the enhancement of surface modification of DPFs from the delignification process to the extraction of cellulose microcrystals (CMCs). Furthermore, structural, morphological, thermal, mechanical, dynamic-mechanical, rheological, and water absorption all improved the biocomposites characteristic performances as a function of the modified DPFs. Hence, the PVC HDPE-HNO3F composite reveals a selective advantage to be a good potential candidate for several structural application

Manufacturing Distinction: Gaining access to Mass Customization in the Production of Architecture

Contemporary architecture often finds itself challenging the physical constraints of the previous era and typically aims to be one of a kind. This thesis views architecture as the accumulation of design and construction and considers both from the view of constructibility. The design of architecture relies upon the formal desire, its materiality, function, direction of which parts are needed and how they can be constructed. The construction of architecture focuses on the coordination, fabrication and assembly of these parts. The industry of construction has three primary constraints: time, cost, and labour. To ease the construction process ideals have been borrowed and implemented from manufacturing to allow streamlining and moved away from the world of bespoke construction. We sit in a system of construction based upon the manufactured part. Manufacturing operations follow one essential formula, the transformation of raw material through the addition of machinery, tools, energy, and labour, to provide the desired product with greater function and value. All consumer items are created through these methods individually or in some combination, having to navigate the complex order of procedures which transform simple materials into everyday objects. The constraints of material play a significant role in the manufacturing operation available to produce any given object and its subsequent performance in an architectural application. Architecture is much more than the manufacturing of a single object. Similar to the production of bikes, cars and other consumer products, architecture utilizes what is known as a system of production. With increased product demand the system of production has naturally transformed as well. Improvements can be seen in areas of logical flow (the division of labour and interchangeable parts), physical flow (the assembly line, mechanization, and digitalization), and controls (tolerances and standards). The constraints of a product play a large role in the appropriateness of a system of production for that object, subsequently impacting the feasibility of any object being economically produced. Manufacturing processes are moving towards digital management and flow as a way of offering unique options within the production of manufactured parts. Overall, architecture strives for a way to be unique within the boundaries of manufactured elements, achieving this through different means such as distilling the function of a space to the elements that construct it, constructing with modular elements, and componentized customization. The transition towards digital design of objects within the industry allows a physically ‘free’ environment to create within; additive manufacturing offers the processing counterpart by digitally shaping physical objects from ‘nothing’. Moving architecture into the digital realm shifts it into a place to easily integrate digital design data into the manufacturing process. Having the ability to bypass the challenges of how we make items, why we choose specific materials, why we produce at specific volume runs, and ties into existing digital production processes. The potentials stand out in the area of producing objects with unique physical constraints or meeting the demands of small product runs

Some Critical Issues for Injection Molding

This book is composed of different chapters which are related to the subject of injection molding and written by leading international academic experts in the field. It contains introduction on polymer PVT measurements and two main application areas of polymer PVT data in injection molding, optimization for injection molding process, Powder Injection Molding which comprises Ceramic Injection Molding and Metal Injection Molding, ans some special techniques or applications in injection molding. It provides some clear presentation of injection molding process and equipment to direct people in plastics manufacturing to solve problems and avoid costly errors. With useful, fundamental information for knowing and optimizing the injection molding operation, the readers could gain some working knowledge of the injection molding

Aeronautical Engineering: A continuing bibliography, 1982 cumulative index

This bibliography is a cumulative index to the abstracts contained in NASA SP-7037 (145) through NASA SP-7037 (156) of Aeronautical Engineering: A Continuing Bibliography. NASA SP-7037 and its supplements have been compiled through the cooperative efforts of the American Institute of Aeronautics and Astronautics (AIAA) and the National Aeronautics and Space Administration (NASA). This cumulative index includes subject, personal author, corporate source, contract, and report number indexes

The 15th Aerospace Mechanisms Symposium

Technological areas covered include: aerospace propulsion; aerodynamic devices; crew safety; space vehicle control; spacecraft deployment, positioning, and pointing; deployable antennas/reflectors; and large space structures. Devices for payload deployment, payload retention, and crew extravehicular activities on the space shuttle orbiter are also described

Aeronautical engineering, a continuing bibliography with indexes (supplement 197)

This bibliography lists 488 reports, articles and other documents introduced into the NASA scientific and technical information system in January 1986

Laser surface modification of biomedical alloys

This study investigated the effects of high speed laser surface modification on 316L stainless steel and Ti-6Al-4V for biomedical implants application. Laser processing was carried out in an inert argon environment using a 1.5 kW CO2 laser. Parameters investigated in this work included irradiance, residence time, pulse width and sample pre-treatments. Surface topology, microstructure and melt pool depth were characterised using the scanning electron microscope. White light interferometry and stylus profilometry were used to determine the surface roughness. X-ray diffractometry was used to investigate the crystallinity and phase transformation induced by the laser treatment. Micro-hardness was measured using a Vickers micro-hardness indentation apparatus. Wear behaviour was investigated using a pin on disk apparatus. Corrosion behaviour was evaluated using a potentiostat and an electrochemical cell set-up simulating human body conditions. Biocompatibility of the samples was investigated in vitro by monitoring NIH/3T3 fibroblast and MC3T3-E1 osteoblast cell growth via MTT and Hoechst DNA assays. A strong correlation between irradiance, residence time, depth of processing and roughness was established in 316L. High depth of altered microstructure and increased roughness were linked to higher levels of both irradiance and residence times. At fixed energy density, increase in residence time resulted in growth of the melt pool. In the melted region, a uniform composition in microstructure with fewer impurities was observed. In Ti-6Al-4V alloy, laser treatment resulted in crack-free layers, twenty to fifty microns thick. With increase in both irradiance and residence time, surface roughness was found to decrease while melt pool depth increased. A martensite structure formed on the laser treated region producing acicular αTi nested within the aged βTi matrix. The βTi phase volume fraction was reduced by up to 19%. Microhardness increased up to 760 HV0.05 which represented a 67% increase compared to the bulk material. A homogenous chemical composition of the alloying elements was achieved in laser modified regions. Much lower levels of wear were noted in laser treated samples compared to untreated samples. Stable passive polarisation behaviour and reduction in corrosion rates was noted in treated samples ranging between 86 and 239 nm yr-1 compared to 108 nm yr-1 for untreated samples and 309 nm yr-1 for grit blast samples. Direct contact assays showed that laser treated samples had improved cytotoxicity properties compared to their untreated counterparts