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Thermal and Mechanical Properties of Functional Monomer Modified Soy Protein Plastic by Reactive Extrusion Technology
Chemical modification of soy plastic with monomers such as maleic anhydride, glycidyl methacrylate and styrene was accomplished by using reactive extrusion technology. Thermal and mechanical properties of modified soy protein plastic were characterized by using Differential Scanning Calorimetry, Dynamic Mechanical Analyzer and United Testing System. It was found that the denaturation temperature, the glass transition temperature and ( relaxation temperature of soy flour plastic changed and hence tensile properties of modified soy protein plastic improved.
Mechanical Properties of Hybrid Polyester Composites
There are different reasons why the production of polyester composites with natural reinforcements, like jute can be of interest. One of them is to fabricate the hybrid composites with cheap waste jute sacks as reinforcements in combination with glass mat. The laminates have been fabricated with a different number of jute and glass mat layers and different type of polyester resins. Also, the content of cross-linking agent has been varied. As the indicator of change of mechanical properties, tensile and flexural strength as well as tensile and flexural modulus have been determined. Based on the planned experiments and statistical analysis it can be concluded that in comparison with glass mat polyester composites, the mechanical properties of hybrid composites in optimal combination of glass and jute reinforcements are lower, but at the same time the laminates are 15 to 20% cheaper.
Process Induced Orientation of Nanolayers in Polyolefin Nanocomposites
Polypropylene nanocomposites with layered silicates have been prepared with and without edge functionalization by melt processing. The resulting composites were subjected to uniaxial extensional flow in the core of axisymmetric converging dies at strain rates of up to 5 s-1 and a Hencky strain of about 5. The edge treated clay led to a much greater level of exfoliation as determined by XRD, TEM and dynamic viscosity measurements. We observe that at the high strains, the nanolayers are predominantly oriented parallel to the flow direction in the core, in contrast to the perpendicular orientation reported by Okamoto et al. for uniaxial extension of nanocomposite strips to a strain of 1.3.
Kinetic Stability of the Well-Exfoliated State in Polypropylene-Clay Nanocomposites Made by Solid-State Shear Pulverization
Analysis by electron microscopy, x-ray diffraction/scattering and DSC has revealed that well-exfoliated states can be achieved in polypropylene (PP)-clay nanocomposites using a novel non-equilibrium processing method called solid-state shear pulverization (SSSP). Such well-exfoliated states cannot be achieved in PP/clay nanocomposites by melt processing. Nanocomposites made via SSSP have been found by x-ray and DSC analysis to remain well-exfoliated after 1.5 to 2 hr of annealing in the melt state of PP. Thus, even if a well-exfoliated state is not thermodynamically favored, it is kinetically stable over long times in the melt state.
Thermo-Kinetic Compounding of Polypropylene and Clay
Polypropylene (PP)/Montmorillonite (MMT) clay nanocomposites have been prepared by melt mixing PP and different levels of a predispersed organoclay masterbatch (PP/clay concentrate). Melt mixing was achieved using a Gelimat, a high-speed thermo-kinetic mixer. The Gelimat system is designed to handle difficult compounding and dispersion applications and can achieve mixing, heating and compounding products within a minute. Therefore, the thermal history of the compounded polymer is short, which limits degradation. The structure and properties of the nanocomposites prepared with a Gelimat were compared to ones prepared with a twin screw extruder. The structure and properties of PP/clay nanocomposites were compared by X-ray diffraction, mechanical testing and rheological analysis. Results indicate that a better exfoliation of the clay can be achieved with thermo-kinetic mixing when compared to extrusion, resulting in better mechanical properties.
Tensile Properties and Fracture Toughness of PP-Based Nanocomposites
The tensile properties and the fracture toughness, using the essential work of fracture method, of melt-compounded polymer nanocomposites (NCs) based on polypropylene with different organo-modified clays (montmorillonite) and maleic anhydride grafted PP coupling agents were studied. Improvements in tensile and fracture properties were observed, which were related to the level of dispersion of clay particles, both at the nano- and the micro-scale. Clay micro-particles acted as void nucleation sites within the PP matrix. The highest tensile properties and highest fracture toughness were obtained for the PP/clay compound showing high particle density with good particle-matrix adhesion, which led to intermediate void nucleation but extensive fibrillation.
Development of Polyolefin Nanocomposites: Relationship between Formulation, Processing, Structure and Performance
The preparation of nanoclay-reinforced polyolefin nanocomposites by means of melt processing was investigated. Different formulations and processing conditions were used in order to optimize the chemical interaction between the polymer matrix and the clay so as to maximize the performance. X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared (FT-IR) spectroscopy, thermogravimetric analysis (TGA), and differential thermal analysis (DTA) were used to study the chemical interactions between the polymer and the organo-nanoclay as well as the dispersion of the nanoclay. It was shown that the various parameters (chemistry and concentration of organo-intercalant, mixing conditions, and especially chemistry and concentration of coupling agent) all affect the ultimate performance and that the interactions between them must be taken into consideration in developing nanocomposite systems.
Polymer-Clay Nanocomposites Prepared in Supercritical Carbon Dioxide
An alternative route to prepare polymer-clay nanocomposites using supercritical carbon dioxide (scCO2) is described. The presence of clay nanoparticles significantly influences the morphology, foaming process and crystallization of a polymer when processed in scCO2. Intercalated structures are successfully produced in the presence of scCO2 even when favorable interactions between the polymer and the clay are not present. The effect of scCO2 on the intercalation process is analyzed for a variety of polymer systems both with modified and unmodified clays. By controlling the hydrophilicity of the polymer and clay systems, specific understanding of the effect of scCO2 on the structure and morphology of the nanocomposites is obtained. Experimental results show significant increases in the clays d-spacings for scCO2-treated samples. This behavior is consistent regardless of the nature of the polymer, showing significant amounts of intercalation even in purely hydrophobic polymers.
Mechanical and Electrical Properties of Exfoliated Graphite-Platelet Polypropylene Nanocomposites
Polypropylene based nanocomposites reinforced with up to 25 vol% exfoliated graphite nano-platelets were fabricated using extrusion and injection molding. The mechanical and electrical properties of the graphite nanocomposites were investigated and compared to the properties of polypropylene-based composites reinforced with other conductive materials, e.g., carbon black and carbon fibers. It was found that the graphite nano-platelets were the most effective at increasing the modulus of the polypropylene and comparable to the other materials in terms of percolation threshold.
In-Situ Wide-Angle X-Ray Scattering (WAXS) Analysis of Electrically Activated Polypropylene(PP)/Clay Nanocomposites
Recently we have invented a novel method for fabricating polypropylene (PP)/clay nanocomposites by applying the electric field. Electric field was found to facilitate destruction of the layer-stacking and separation of the silicate layers by the penetration of polymer chains into silicate galleries. This was evidenced by rheological measurements, X-ray diffraction and Transmission electron microscopy. From this observation, we could find that the microstructural change of PP/Clay nano-composites induced by the electric field is a very important factor to control the performance and morphology of the material. In this study, real-time evolution of PP/clay nanocomposites under electric field using in situ wide-angle X-ray scattering (WAXS) analysis will be presented. We designed a heating block equipped with electric circuits to apply electric field on the molten state of PP/clay composites. The real-time microstructural changes of PP/clay nanocomposites under AC electric field of 1kV/mm and 60 Hz were analyzed by the result of 2D WAXS data. This will be compared with that under DC electric field. We will present the kinetics of melt intercalation process under electric field.
Vibration-Assisted Liquid Composite Molding
By oscillating the injected resin stream in liquid composite molding, the mold filling time can be significantly reduced. Flow enhancement is achieved because of the shear-thinning characteristics of typical polymer resins, as the effective shear rate of the resin is increased by oscillation of the resin within the fiber preform and the viscosity of the resin is correspondingly reduced. An experimental apparatus has been developed which consists of one-dimensional flow within a fiber preform and a vibrating piston which forces the inlet resin stream to oscillate. Experiments have been conducted using a polyacrylamide/water solution to simulate the polymer resin, and effects of oscillation amplitude, frequency and fiber volume fraction have been investigated. A simple analytical model has also been developed, and experimental results confirm the predicted trends in the amplitude, frequency and volume fraction effects on flow enhancement.
Rapid Surface Treatment of Reinforcing Fibers Using Ultraviolet Light Processing
A fast, inexpensive and environmentally benign process requiring only UV light and air for the surface treatment (oxidation) of reinforcing fibers has been developed that represents a substantial improvement over existing methods. In this new method, fibers are subjected to short wavelength ultraviolet (UV) light producing ozone from atmospheric oxygen. UV photons can also react with ozone to create monatomic oxygen, a highly reactive chemical species which is available to oxidize the fibers. Additionally, the UV photons can break chemical bonds on the fiber surface creating favorable conditions for reaction with ozone and monatomic oxygen. The result of this two-fold process is the rapid oxidation of the fiber surface that is essential to promote favorable interactions with the matrix in polymer composites. The effect of UVO treatment on the surface chemistry, tensile strength, and interfacial adhesion of a PAN based carbon fiber and an aramid fiber is reported.
Water Diffusion Based Non-Destructive Evaluation (NDE) of PMR-II-50/M60J 4HS Weave Carbon Fabric Composite Materials under Stress-Thermal Cycling
Due to the geometric complexity of woven fabric composite materials, conventional Non-Destructive Evaluation (NDE) methods such as x-radiography and acoustic emission (AE) do not show microcracks well inside the materials. In this study, a simple and cost effective water uptake test as a NDE methodology for PMR-II-50/M60J (polyimide/carbon fiber) 4HS weave fabric composites is suggested. The short term water uptake test for 24 hours at 80°C has been performed before and after stress-thermal cycling experiments with the TAMU developed conduction heated stress-thermal cycling apparatus. The woven composite materials’ non-Fickian model during short term water uptake, that is, the rate of uptake initially increases rapidly followed by quick slow down associated with diffusion in cure-induced voids and cracks was modified by the effective diffusivity depending on crack densities. The suggested crack densities dependent diffusion model was compared with the experimental data. The application of the water absorption induced NDE was also re-evaluated by comparing to the results of the literatures in terms of crack closure by swelling and unloading of the existing load and matrix dissolution by hot water.
Nanocomposite Polyetherimide with High Thermo Oxidative Stability
Selected fillers were incorporated to prepare polyetherimide composite. The influence of fillers on the thermo-oxidative stability of the composite was studied by thermogravimetric analysis. The results showed that at optical filler loading and characteristics, the polymer composite became superior in its thermo-oxidative stability that is very promising in widening the window of service temperature of polyimides for extremely high temperature conditions where most polymeric composites fail. The findings should prove useful in developing high-temperature polymer composites for aerospace and electronics applications.
Low Cost Processing of Carbon Fabric Reinforced Nylon Composites
This manuscript describes the processing techniques and processing windows used to produce carbon fiber reinforced nylon matrix composite panels. Preliminary mechanical property measurements were also made. Anionic polyamide 6 resin (casting grade) was polymerized in situ after infusion. Careful time and temperature control were necessary to obtain total fiber impregnation with subsequent complete polymerization. These advances will permit the use of affordable thermoset manufacturing processes such as Vacuum Assisted Resin Transfer molding (VARTM) or Resin Transfer Molding (RTM) to produce thermoplastic-matrix composite structures.
Processing and Mechanical Properties of Continuous Fiber Reinforced Thermoplastics
In this study, multi-axial warp knitted thermoplastic composites were fabricated by our-developed Micro-braiding technique. Cross-sectional observation, tensile test and 3 point bending test were performed. The composite with good impregnation state was obtained under appropriate molding conditions, consequently high mechanical properties were achieved. The multi-axial warp knitted fabric composite without unimpregnated region had the equivalent mechanical properties with unidirectional composite laminates. Moreover, new concept of continuative fabrication method was proposed.
Measurement System Analysis for Viscosity Measurement of Highly Filled Biofiber Composites
A comprehensive measurement system analysis (MSA) on measurement of apparent viscosity using the slit die method was conducted. Nine materials and three operators with three repeats were used. P/T (precision to tolerance) and P/P (precision to process) ratios were estimated from gage R&R analysis. Repeatability was found to be greater than reproducibility. Slip analysis on the wood fiber composites indicated that these composites essentially flow by slip mechanism. Six Sigma methodologies with rigorous method development resulted in establishing control materials and implementing SPC in a manufacturing plant.
Injection Molded Biocomposites from Natural Fibers and Modified Polyamide
This paper focuses on the development of a new technology and process in order to manufacture natural fiber reinforced engineering thermoplastics like nylon 6. Natural fibers are not suitable reinforcements when high temperature melting (above 200°C) engineering thermoplastics is used as matrix materials because natural fibers start to degrade thermally at above 200°C. Small quantities of inorganic salts like lithium chloride were added to the nylon 6 during melt extrusion processing to depress its melting temperature. The final composites are injection molded into test specimen at the reduced processing temperatures of nylon 6. The molded plastics and composites are tested for mechanical and thermal properties. Natural fiber reinforced nylon 6 composites show improved tensile and flexural properties. The morphology of the fracture surfaces is observed using Environmental Scanning Electron Microscopy.
Processing/Structure/Property Relationships for Artificial Wood Made from Stretched PP/Wood-Fiber Composites
This paper presents the processing/structure/property relationships for artificial wood made from stretched PP/wood-fiber (WF) composites that have required strength and density. The die drawing of PP/WF composites causes a unidirectional orientation of the polymer molecules and enhances the mechanical properties significantly along the stretched direction. The drawing of the composites also lowers the density of artificial wood by generating voids at the WF and polymer matrix interface. The critical processing and materials parameters are identified. The effects of these parameters on the structure and the properties are also investigated.
Effect of Processing Conditions on the Physico-Mechanical Properties of Cellulose Fiber Reinforced Poly (Lactic Acid)
Green composites were made from poly (lactic acid) (PLA) and cellulose fibers by extrusion followed by injection molding processing and their physico-mechanical properties were evaluated. The properties of PLA reinforced with varying amounts of wood pulp-based cellulose materials were studied. These composites possess superior thermal and mechanical properties based on the strong interaction between the PLA matrix and the cellulose fibers. It was found that the wood pulp-based cellulose fiber could be a good reinforcement candidate for the high performance biodegradable polymer composites.
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