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The aim of this work was to investigate the various effects of compatibilizers on different aspects. The polypropylene based WPC, containing different compatibilizers, were produced via compounding and injection molding. Testing for tensile and impact strengths as well as for MFR and shrinkage was carried out subsequently. We found, that the presence of a compatibilizer not only enhances tensile strength (up to 80%, depending on wood and compatibilizer concentration), but also influence other properties, e.g. shrinkage and MVR are increasing with increasing compatibilizer concentration. Furthermore, with the help of a saturation model, the effects of different compatibilizer grades, exhibiting different maleic anhydride content as well as different viscosity, were evaluated to get deeper insight in the mechanisms.
In the past three decades there has been great advancement in preparing microcellular thermoplastic polymer foam. However little attention is paid to thermoplastic elastomer. In this study microcellular poly(ethylene-co-octene) (PEOc) rubber foams with a cell density of 2.9×1010 cells/cm3 and cell size of 1.9 ?m are successfully prepared by using CO2 as the physical blowing agent with a batch foaming process. Microcellular PEOc foams exhibit a well defined closed cell structure uniform cell size distribution and formation of unfoamed skin at low foaming temperatures. Their difference from thermoplastic foam is the foam shrinkage in the atmosphere due to the elasticity of polymer matrix. The effect of melt flow rates on the cell growth process is investigated by changing the foaming conditions.
In the past three decades, there has been great advancement in preparing microcellular thermoplastic polymer foam. However, little attention is paid to thermoplastic elastomer. In this study, microcellular poly(ethylene-co-octene) (PEOc) rubber foams with a cell density of 2.9??1010 cells/cm3 and cell size of 1.9 ?¬m are successfully prepared by using CO2 as the physical blowing agent with a batch foaming process. Microcellular PEOc foams exhibit a well defined closed cell structure, uniform cell size distribution, and formation of unfoamed skin at low foaming temperatures. Their difference from thermoplastic foam is the foam shrinkage in the atmosphere due to the elasticity of polymer matrix. The effect of melt flow rates on the cell growth process is investigated by changing the foaming conditions.
Nanocomposites comprising a high percentage of inorganic layers and a low percentage of organic binder have been reported to exhibit remarkable physical properties due to high levels of organization, connectivity and phase morphology. We report the preparation and characterization of a system of this type consisting of montmorillonite layers and thermoplastic polyurethane (TPU) binder. Transparent sheets were prepared and characterized via SEM for structure, TGA and DSC for thermal properties, and DMA for mechanical response. These materials are stable, robust, and exhibit interesting combinations of stiffness and damping capacity.
Delivery of a melt which is homogenous in composition and temperature is paramount for achieving high quality extruded products. However, melting stability can be difficult to determine via typical melt pressure and thermocouple instrumentation. This can result in inefficient operation through non-optimized operating conditions or extruder screw geometry. In this work, melt temperature homogeneity in a single screw extruder is investigated experimentally using a thermocouple mesh technique. The effect of barrel temperature settings and screw speed on die melt temperature homogeneity is investigated. Inferential methods of determining melting stability in-process are investigated with the aim of developing modeling and control techniques to improve process quality and efficiency.
Manufacturing of extruded polystyrene (XPS) foam insulation boards is currently based on weak ozone depleting gases. Mixtures of blowing agents are actually seen as one of the most promising solutions to ozonedepleting substances phase-out. This paper investigates various blowing agent formulations based on mixtures of hydrofluorocarbons HFC-134a (1,1,1,2-tetrafluoroethane) and HFC-32 (difluoromethane). The study focuses on the rheological (plasticization) and degassing (solubility) behaviors of the formulations, as measured on-line during foam extrusion. Rules of mixing for such blends of HFCs are proposed based on the relative contribution of each component to the overall processing behavior.
Massively invasive surgery is often the only cure for the worst cases of cartilage-related diseases. In an effort to physiologically mimic human joints, 4 biomedical thermoplastic polyurethanes (TPU) differing in glass transition temperature, modulus and wettability were foamed using a CO2-based solid-state process. Human cartilage mechanical behavior was closely matched by low density foams of the softest TPU investigated. In vitro osteoblastic studies showed improved cell differentiation, activity and proliferation; all suggestive of TPU foans potential osteointegration. The superior bioactivity and cartilage-matching mechanics make the TPU foam a promising cartilage replacement.
The topography of the inner surface of small bore extruded tubes used in fluid handling applications can affect flow rates, fluid turbulence and biofilm adherence. Quantitative surface roughness analysis of tubes manufactured from different polymers has shown that the inner surface topography is related to the polymer molecular variables, rheological properties and extrusion processing conditions. Surface energy analysis of these surfaces has also been shown to be related to polymer type as well as surface roughness.
The mechanical properties and crystallization behaviors of PP/acrylonitrile-butadiene-styrene/organic montmorillonite nanocomposites (PP/ABS/OMMT) were studied. It was shown that compatilizer PP-g-MAH not only improved the compatibility of PP/ABS but also promoted the dispersity of OMMT particles in continuous phase PP and dispersed phase ABS. In addition PP was reinforced and toughened by both layered silicate OMMT nanoparticles and ABS. The blend weight ratio of PP/ABS/OMMT which was 85/15/2 wt % had a concerted effect on toughening. OMMT nanoparticles also increased crystallization temperature and crystallinity.
The mechanical properties and crystallization behaviors of PP/acrylonitrile-butadiene-styrene/organic montmorillonite nanocomposites (PP/ABS/OMMT) were studied. It was shown that, compatilizer PP-g-MAH not only improved the compatibility of PP/ABS, but also promoted the dispersity of OMMT particles in continuous phase PP and dispersed phase ABS. In addition, PP was reinforced and toughened by both layered silicate OMMT nanoparticles and ABS.The blend weight ratio of PP/ABS/OMMT, which was 85/15/2 wt %, had a concerted effect on toughening.OMMT nanoparticles also increased crystallization temperature and crystallinity.
In order to assure the part quality in the part design step, it is desirable to optimize the cooling circuit prior to the mold design step. In the environment of frequent design changes, a way to optimize automatically the cooling circuit in a short period of time is necessary. In this work, an automated optimization of the cooling circuit was examined with a commercial optimization tool, PIAnO. The optimization technique is useful largely for large parts such as instrument panels and bumpers. The objective function is the deviation of temperature difference from a target mold surface temperature.
In this paper, we will discuss several companies who have not seen recessions as a deterrent to innovation but an opportunity. Using a case study format, we will discuss four companies that have innovated in a recessionary environment. We will derive the lessons learned and offer some recommendations as to ƒ??how toƒ? look for the silver lining in an economic downturn. The objective of this paper is to present examples of companies that re-positioned for growth during an economic downturn. In two of the cases, an innovative business grew out of adversity. The third is a new company that was able to identify a technology developed earlier but eventually abandoned due to a lack of a market. The last invested while its competitors contracted. Due to the poor economy, most of us are experiencing a drop in our business and are looking for ways to reposition our businesses. Our businesses are down as much as 50% from prior years. We have cut our costs, reduced our payrollsƒ??what do we do nowƒ?? The following four companies are examples of what can be done to innovate in a recessionary environment. The following table shows the types of business segmentation opportunities.
A 100 000 g/mol polyethylene molecule has a crosssection of about 0.5 nm and a contour length of about 0.9 ?m. A typical single-walled carbon nanotube (SWCNT) has a cross-section of about 1 nm and a contour length of about 1 ?m. The critical difference from a physics perspective between these two molecules is that the persistence length of the former is about 0.6 nm and the persistence length of the latter is reported as ? 30 ?m.1 One can make a similar comparison between SWCNTs and liquid crystalline polymer molecules; in this case the key difference is that the length of the former is much larger than the length of the latter. This paper presents what is believed to be a synergistic type of behavior that is possibly related to the similarity in size of the two high aspect-ratio materials the fact that single-walled carbon nanotubes can increase the jump in heat capacity at the glass transition. Other measurements involving the behavior of fictive temperatures and activation energies measured from calorimetric studies are also given.
A 100,000 g/mol polyethylene molecule has a crosssection of about 0.5 nm and a contour length of about 0.9 ?¬m. A typical single-walled carbon nanotube (SWCNT) has a cross-section of about 1 nm and a contour length of about 1 ?¬m. The critical difference from a physics perspective between these two molecules is that the persistence length of the former is about 0.6 nm and the persistence length of the latter is reported as ƒ?? 30 ?¬m.1 One can make a similar comparison between SWCNTs and liquid crystalline polymer molecules; in this case the key difference is that the length of the former is much larger than the length of the latter. This paper presents what is believed to be a synergistic type of behavior that is possibly related to the similarity in size of the two high aspect-ratio materials, the fact that single-walled carbon nanotubes can increase the jump in heat capacity at the glass transition. Other measurements involving the behavior of fictive temperatures and activation energies measured from calorimetric studies are also given.
Conformal cooling channel could make the temperature distribution in the mold uniform, reducing cycle time and improving part quality. However, design principle for the conformal cooling channel has not been established yet. In this study, a constructal design principle was tried with hexagonal cooling channel. The size and the depth of the hexagonal cooling channel were optimized to minimize the temperature deviation of the mold surface. Constraint was pressure drop through the cooling channel limited by the pumping capability. The CAE tool for mold cooling analysis was Moldflow Cool.
A thermoplastic elastomer (TPE) blend of thermoplastic polyurethane (TPU) and polypropylene (PP) was sampled from extruded strands and injection molded plaques. Highly stretched strands of the PP phase are aligned parallel to each other along the extrusion direction in the extruded samples while in the injection-molded samples the PP phase is in ellipsoidal domains residing in the shear plane of the mold. Subjecting the samples to a tension load leads to rupture of the elongated strands, resulting in increased tensile set and reduced moduli. Annealing the extruded specimen at 150 oC for 30 min. can create cracks in the blend similar to those generated during tensile testing.
The foaming process of PMMA in specially designed rotor system with screws and previously designed rotor system without screw was studied respectively. In this study, with supercritical carbon dioxide (ScCO2) as a blowing agent, microcellular foam of PMMA was made in traditional steady process and dynamic vibration field respectively by using the isobarical feeding equipment of supercritical carbon dioxide and microcellular foaming simulator. The effects of processing parameters such as pressure, time of saturation, shear stress were investigated, in order to study and analyze the effects of processing conditions on PMMA microcellular plastics. Foamed samples with the cell density of 78.7??107 cell/cm3, average cell size of 12.6 ?¬m have been produced by using the screw system.
Wax formulations prepared using paraffin wax (PW) and hydrogenated resin (HR) were studied to identify effects of temperature and composition on phase homogeneity. A phase diagram was constructed showing regions of PW/HR miscibility and tracking changes in PW crystallisation as HR is added. Polarised optical microscopy identified changes in nucleation and crystal growth mechanisms of the PW semi-crystalline phase promoted by HR. A simplified wax injection system was used to investigate conditions for defect formation. Results, to be validated using a ProCAST model, showed defects occurred by injecting blend compositions corresponding to regions of PW/HR phase separation as shown by the phase diagram.
In the present study, the friction and wear properties of high temperature resistant polymers, Polyetherimide (PEI) and Polyetheretherketone (PEEK), have been investigated at specific combinations of high pressure, velocity and temperature against smooth steel counterparts. The effects of internal lubricant, polytetrafluoroethylene (PTFE) and PTFE with short fiber reinforcements (carbon fiber) are outlined. The tests were performed on a thrustwasher testing machine under dry sliding conditions. Different analytical techniques were employed to study the correlation between the transfer layer and friction properties. Lubricated and lubricated-reinforced compounds showed excellent wear resistance compared to pristine resins.
The mechanical properties and misconstrues of high impact polystyrene (HIPS) toughened by styrenebutadiene-styrene (SBS) were studied to find the Brittle-Ductile Transition Point. At the Brittle-Ductile Transition point, HIPS and SBS alloys were prepared using melt intercalation technique by blending HIPS and SBS while used acrylonitrile-styrene (AS) powder, gaining higher impact and tensile strength. Their microstructures near the Transition Point were characterized by scanning electron microscope (SEM) to investigate the toughening mechanism of HIPS/SBS/AS composites. The toughening mechanism is similar to the mechanism of RIF toughening rather than the cold-drawing theory which applied to ductile matrixes toughed by rigid organic filler (ROF).
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