The SPE Library contains thousands of papers, presentations, journal briefs and recorded webinars from the best minds in the Plastics Industry. Spanning almost two decades, this collection of published research and development work in polymer science and plastics technology is a wealth of knowledge and information for anyone involved in plastics.
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Depression of Tg in Polystyrene by Freeze-Drying
The calorimetric glass temperature of polystyrenes with molecular weights ranging from 3.0 x 103 to 43.7 x 106 g/mol are measured as a function of cooling rate for both bulk material and for samples freeze-dried from dilute solution. We find that Tg is depressed approximately 5 K for samples which can fully entangle and also the same amount for ultrahigh molecular weight samples which cannot achieve full entanglement. The lowest molecular weight samples show only 2 K depression on freeze-drying. Annealing eliminates the depression in Tg. The results indicate that the reduction of the glass temperature due to freeze-drying cannot be due to the reduced entanglement concentration induced by freeze-drying.
A Study on Modification of PP with Aliphatic Diamines
In previous work, modification with different diamines was reported and the diamine-grafted polypropylene was used as an adhesion-promoting agent to layer of polycarbonate (PC). A study on the technique of adding reactive is reported in this work. Packets of different aliphatic diamines were reacted with polypropylene modified with maleic anhydride (PPgMA) in melting process. The reaction between amine primary groups and maleic anhydride groups was analyzed by FTIR. Differences in viscosity measurements were evident using packets of diamine, samples obtained by packet of diamine showed a low value of viscosity compared with samples produced by diamine-packet. Two-layered films were prepared using PC film and PPgNH2 film. Adhesion strength was measured using T-peel test. All results permit conclude which diamine is promoting the best adhesion between PPgNH2 and PC layers.
The Characterisation and Physical Testing of Micro-Mouldings
Nano-indentation techniques are being developed for the mechanical testing and physical characterisation of micro-mouldings. A procedure for the embedding, sectioning and testing of micro-mouldings was described at Antec ’02. The technique has been further refined and a systematic evaluation of injection mouldings with micro-dimensions has been carried out. The results from the nano-indentation tests have been supported by atomic force microscopy measurements relating to the dimensions and geometry of the indentations. The results that will be presented will show that the levels of anisotropy of mechanical properties can be measured in micro-mouldings by the methods described.
The Effect of Melt Temperature and Extrusion Rate on the Die Swell of Metallocene and Conventional Polyethylenes
A range of metallocene and conventional PE resins of various comonomer types, were extruded from a single capillary rheometer, at different melt temperatures and extrusion rates. Analysis shows that die swell increases with increasing extrusion rate and decreasing melt temperature. GPC analysis elucidated the influence of molecular characteristics on die swell. Increased die swell was found for the broader MWD (3.5-3.8) conventional PEs, in comparison with the narrower mPEs (2.1-3.1), and in the higher molecular weight resins. Furthermore, long chain branching was found to increase die swell.
Design, Fabrication, and Assembly of a Polymer Electrolyte Membrane Fuel Cell (PEMFC)
This report will include the way to design, fabricate, and assemble a Polymer Electrolyte Membrane Fuel Cell (PEMFC) to maintain a low voltage source, near one volt, that runs at operating temperatures near 80 degrees Celsius. Creating a stack of cells will provide an energy solution that is more efficient than the system in place today. The PEMFC runs off of pure hydrogen and air (oxygen) and will provide a power source that is non-pollutant and renewable since hydrogen is readily available through the electrolysis of water. The problems with this experiment are maintaining moisture control on both the cathode and anode and the other problem is in controlling the hydrogen gas supply since hydrogen is very explosive when combined with oxygen. With these problems taken into consideration the PEMFC could be the energy source for the future.
Polymer Defect Detection and Classification Utilizing Camera Optics, Real Time Computation and Small Scale Resin Sample Processing
This paper discusses a technique for identifying and analyzing defects in plastic compounds. Its primary use is in resin or master batch production or as a general purpose QC or investigative instrument.Initially the resin is processed in a simulation of typical production conditions, by producing blown or cast film on a small scale ( < 2 Kg/hr )The film is passed through the optical field of a CCD line scan camera Data from the camera is processed in hardware and software to capture the continuously moving image.The image data is then analyzed to automatically discriminate and classify a wide range of defects, flaws and process induced variables.The Authors will presentThe special considerations of the extrusion processThe optical design for 5 micron detection resolution of a moving webAlgorithms employed to classify and present data in real time at high speedThe late stage development of this system to detect clear particle contamination in a clear film.
Melt Processing of Tailored Acrylic Copolymers
Steady shear rheology of acrylonitrile (AN) terpolymers provides an indication of the melt stability of tailored AN copolymers. It has been found that AN can be copolymerized with methyl acrylate (MA) to produce a material with up to 88 mole percent AN that possesses suitable melt stability at elevated temperatures for processing into carbon fiber precursors. A third copolymer, acryloylbenzophenone (ABP), is copolymerized in 1-2 mole percent to act as a UV stabilizing agent that activates crosslinking following fiber formation. Boric acid (BA) is also added as a “free radical quencher”, which enhances the thermal stability of the terpolymer.
Structural BioComposites from Natural Fibers and Biopolymers
BioComposites are emerging as a viable alternative to glass-reinforced composites. Natural fibers have advantages over man-made fibers (e.g. glass and carbon) in areas such as low cost, low density, competitive specific mechanical properties, reduced energy consumption, carbon dioxide sequestration, and biodegradability. The combination of bio-fibers like kenaf, hemp, flax, henequen and sisal with polymer matrices from both non-renewable and renewable resources to produce composite materials that are competitive with synthetic composites requires special attention to the biofiber-matrix interface, and its resulting adhesion, as well as to the processing methods used to produce these materials. The development of useful biocomposite materials also requires that water-based sizings or dry coupling agents be used to improve fiber-matrix adhesion.. Through bio-fiber surface treatment, biopolymer modification, and adequate processing techniques, novel bio-composites can be designed and engineered so as to substitute/supplement glass fiber composites in various applications.
The Effect of Weathering on Wood-Polymer Composites
A range of wood-polymer blends, containing 20, 40 and 60% w/w MDF sawdust (212-850 microns) were prepared using polyethylene, polypropylene and polyvinyl chloride. The blends were melt compounded using a Killion single screw extruder with a barrier type screw design. Over a weathering period of 2 months (fluctuating wet and dry) the mechanical properties decreased in all composites with water retention evident when the composites were “dry”. The rate of water absorption increased during the second wetting period. The diffusivity of water through the wood-polymer composites was found to be greatest for the PVC based composites.
Injection Molding of a Starch Based Polymer Reinforced with Natural Fibers
Biodegradable composites were developed by compounding a commercial corn starch polymer with pine and Alfa fibers on a counter-rotating twin screw extruder. Subsequently, the compounds were injection molded under optimized conditions and characterized for the respective mechanical behavior and morphological features.The obtained results establish by evidence that this kind of composites present mechanical performance (in terms of stiffness and strength) within the range of the polymeric systems based on high consumption thermoplastics. In comparison with pine fibers, Alfa based composites presented a better performance as result of various advantageous morphological and interfacial aspects.
Effects of CBA on Extrusion Processing of Foamed Plastic/Wood-Flour Composites
It has been established that the production of foamed structure in plastic/wood-flour composites (PWC) is overwhelmingly dominated by the gaseous emissions/volatiles released by the wood-flour. By adopting effective processing strategies, the role of these volatile emissions on foam morphology of plastic/wood-flour composites can be largely suppressed. This paper discusses these strategies, and presents the results obtained from extrusion processing when the chemical blowing agents (CBA) predominantly control the density reduction. The effects of CBAs on extrusion processing of PWC are discussed. Although the used CBAs produced fine-celled structures, the processing window for density reduction was quite narrow.
An On-Line Analytical Method for Quality Control for Bio-Fiber Reinforced Composites
Wood fiber reinforced thermoplastics are a recent introduction and are finding increased acceptance in a range of industries. Quality control tests for these composites are expensive and time consuming. A quantifiable, reliable method of quality control in real time is increasingly becoming critical with increasing demand and longer production runs.This paper discusses the development of a new method using analytical techniques to monitor quality based on the free, unreacted acid in the composite. The results from this test correlate well to composite physical properties. This test is also useful for process design and optimization studies.
Optimization of Coupling Agent Characteristics for Maximizing Performance of Wood Fiber Thermoplastic Composites
Wood fiber reinforced thermoplastics are a recent phenomena. Their usage has been growing with increasing acceptance in a variety of industries. Applications range from non-structural to load bearing structural components.The multitude of applications requires diverse performance attributes. Performance of these composites is based on the efficiency of coupling the non-polar thermoplastic matrix to the polar wood fibers. Maleic anhydride grafted polymers are widely used for achieving this coupling. Selection criteria for appropriate performance attributes are based on a complex web of process, material and design variables.This paper presents the results of a designed experiment wherein the best combinations of compatibilizer characteristics, molecular weight and percent maleic anhydride grafting level and wood fiber moisture level were determined, to achieve the optimum balance of responses.
A Low-Cost Composite Bicycle Frame Produced by RTM: From Concept to Reality
In this paper the complete design and the manufacturing of an innovative composite bicycle frame is presented. The initial target and the concept are described to produce a lightweight frame using unsaturated polyester, glass fiber preforms, closed foam core and metal inserts. The final composite body frame has comparable weight and stiffness with a corresponding aluminum tube frame. For the mass production of the frame the resin transfer molding technique with a closed mould has been explored. Furthermore the extension of the method to use epoxy resins and carbon fibers is straightforward resulting in considerable weight reduction and strength increase but also to a moderate increase of the material costs.
Characterization of BMI-Carbon Fiber Composite Microcrack Development under Thermal Cycling
The objective of this research is to determine the effect of thermal cycling on the development of microcracks in BMI-carbon fiber composites (5250-4 RTM / IM7 6K 4-harness satin weave fabric). By clamping composite specimens on the radial sides of two half cylinders having two different diameters (127mm and 70mm), two different pre-stresses (-0.4 to 0.4 GP and -0.7 to 0.7GPa) are applied to the composites. Three different thermal cycling experiments, 1) –196°C to 250°C, 2) 23°C to i)150°C ii) 200°C iii) 250°C, and 3) -196°C to 250°C were performed as a function of pre-stress, number of thermal cycles, heating or cooling rate, and humidity conditions. An in-situ monitoring microscope is used to observe the microcrack development under synergistic stress, time, and temperature conditions. The experimental results suggest that there is a higher probability of microcracking with increasing number of thermo-cycles, higher pre-stress and humidity. A mathematical model considering residual stress and pre-stress is suggested to predict the microcracking under environmental conditions.
The Effect of Thermal Spiking on the Moisture Absorbtion and Dynamic Mechanical Properties of Carbon Fibre Epoxy Resin Laminates
The effect of temperature, moisture and thermal spiking on the performance of Cycom 8 HS carbon fibre epoxy laminates was investigated. Cured laminate samples were preconditioned (65°C, 95%R.H.) and these samples were exposed to various thermal spiking (150°C/2min) programmes. DMTA techniques measured the changes in glass transition temperature (Tg), storage modulus (log E’) and damping (Tan ? max) of the laminates as a result of exposure to these environments. The thermal spiking programme was shown to cause an increase in both the amount and rate of moisture absorption of the laminates. These increments were accompanied by a significant decrease in Tg, log E’, and Tan ? max. SEM analysis also showed the progressive growth of both interlaminar and translaminar micro-cracks as a result of thermal spiking.
Electromagnetic Shielding of Epoxy Resin Composites Containing Carbon Fibers Coated with Polyaniline Base
Polymers filled with carbon fibers have recently received attention due to their remarkable conducting and dielectric properties. The fibrous character of the filler causes that the percolation threshold of these systems is reached at 1 – 2 vol. % of conducting component. Coating the fibers with a non-conducting layer can substantially increase the percolation threshold, thus enabling to broaden the range of concentrations where the DC conductivity of material is low and its behavior is not affected by the instabilities in the vicinity of the percolation threshold.As far as dielectric properties are concerned, at high frequencies they are mainly controlled by the polarization of induced dipoles of the fibers or their clusters. Thus, by increasing filler loading, i. e. with higher number of induced dipoles, an improvement of dielectric properties can be expected. The present study has been aimed at electromagnetic interference shielding properties of epoxy resin composites containing short carbon fibers coated with a layer of non-conducting polyaniline base. Due to the coating, the percolation threshold shifted to 16–20 vol. % of the filler. Such high concentration caused a considerable increase in complex permittivity and AC conductivity of investigated material below the percolation threshold. The evaluation of shielding effectiveness and the skin depth the radiation can penetrate, however, have revealed that the material is still not suitable for commercial applications. Nevertheless, the composites of short carbon fibers coated with non-conducting polyaniline base show a high AC conductivity in high frequencies (10 MHz –1300 MHz) and low DC conductivity at the same time. They can thus be used for transmitting high-frequency signals, and for shielding of low-frequency ones. Moreover, they do not short-circuit the surface of electronic systems.
Investigation into FRP Repaired RC Columns
Due to the aging of the infrastructures in this country, repair and rehabilitation of damaged steel reinforced concrete (RC) structures using fiber reinforced plastics (FRP) are increasingly becoming a topic of interest in the infrastructure community. In this study, a finite element analysis using ANSYS® was used to conduct a parametric analysis. Experiments were also conducted to justify the finite element analysis results. A reasonable agreement was found between the finite element analysis and the test results. The effect of the thickness, stiffness, and fiber orientation of the FRP layers as well as the interfacial bonding between the FRP and the concrete on the strength and stiffness of the repaired columns was evaluated using the finite element modeling.
Quantification of Energy Absorption in Glass Fibre Reinforced Polymers (GFRP) under Transverse Loading
Energy absorption for each of the following damage mechanisms: contact indentation, matrix cracking and delamination, and friction between delamination crack surfaces was quantified for glass fibre reinforced polymers (GFRP), in terms of the percentage of the total absorbed energy under transverse loading. The results suggest that only 50% of the total absorbed energy was consumed for delamination and matrix cracking. Therefore, any attempt to correlate the impact resistance of the GFRP with its delamination toughness needs firstly to exclude the energy loss due to the friction and the contact indentation. Otherwise, the derived delamination toughness would significantly overestimate the true toughness of the GFRP.
Nano-Clay and Long Fiber Reinforced Composites Based on Epoxy and Phenolic Resins
High-performance thermoset polymer composites are synthesized by using both long fibers and nano-clays. Epoxy and phenolic resin, the two most important thermoset polymers, are used as the polymer matrix. Hydrophobic epoxy resin is mixed with surface modified nano-clays, while hydrophilic phenolic resin is mixed with unmodified nano-clays to form nanocomposites. Long carbon fibers are also added into the epoxy nanocomposites to produce hybrid composites. Mechanical and thermal properties of such composites are compared with both long fiber-reinforced composites and polymerlayered silicate composites. The optimal conditions of sample preparation and processing are also investigated to achieve the best properties of the hybrid composites.
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