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STUDY ON CONTINUOUS EXTRUSION FOAMING OF PP/PS/NANO-CLAY WITH SUPERCRITICAL CO2
The PP/PS/Nano-clay blends were foamed in this paper using a single-screw extruder foaming system and cell structure of foamed samples was characterized using SEM. By comparing cell morphology, foam expansion ratio, cell density etc, the effect of blend ratio for R-PP/PS/Nano-clay blends on cell morphology of foamed samples was studied. The results showed foaming behavior of PP could be improved when it was blended with PS, and the addition of Nano-clay further improved the foaming property of the blends. Microcellular foamed plastics with cell-population density as high as 2.16 108cells/cm3 were obtained when 5wt% Nano-clay was included in the formulation.
MEASUREMENT AND ANALYSIS OF EXTRUSION FOAMING BEHAVIOR OF PP/PDMS BLENDS
Foaming behavior of PP/PDMS blends was investigated using a single extruder foaming system, with CO2 as the foaming agent. Influences of die temperature and foaming agent conten on foam expansion ratio, cell density and die pressure were analyzed. Our research showed that gas loss and crystallization stiffening of the melt at low temperature were the two governing factors of foam expansion ratio, and the addition of PDMS improved the expansion ratio of PP foamed samples at higher loadings (5wt% and 7wt%) of foaming agent. Foamed samples with expansion ratio as high as 23 were obtained as 5wt% CO2 was used.
CAUSE OF OCCATIONAL FAILURE OF CPVC PIPES AND FITTINGS IN HYDRONIC HEATING SYSTEMS
CPVC pipes and fittings are commonly used in hydronic heating systems. However, there are occasional failures of CPVC pipes and fittings used in these systems due to chemical contamination by the lubricant oil used in the heat exchanger refrigerant. Although leaks in the heat exchanger are rare, when a leak does occur, it can lead to almost immediate failure of the CPVC piping system. This paper discusses the results of our forensic failure analyses on CPVC hydronic piping. Also we present the results of our studies on the chemical compatibility of refrigerant lubricant oils.
EFFECT OF ULTRA-HIGH THERMAL TREATMENT OF CARBON NANOFIBERS ON EMI SE OF LLDPE NANOCOMPOSITES
The electromagnetic interference shielding effectiveness (EMI SE) and the electrical properties of linear low density polyethylene modified by heat treated carbon nanofibers (Pyrograf III PR-19) and mesophase pitch-based carbon fibers were investigated. After thermal treatment of the nanofibers to 2500C, 20 wt% PR-19 thermal treated nanocomposites displayed a resistivity of ~1e5 cm, and EMI SE values as high as 15 dB for most of the VHF-UHF frequency range. These nanocomposites retained half of the flexibility and strength as well as one-third of the ductility, relative to the LLDPE. EMI SE analysis indicates that absorption is the primary shielding mechanism.
THE PREPARATION OF NANO-CLAY/POLYPROPYLENE COMPOSITE MATERIALS WITH IMPROVED PROPERTIES USING SUPERCRITICAL CARBON DIOXIDE
Supercritical carbon dioxide (scCO2) was used as a processing aid to improve the level of exfoliation and, in some cases, the dispersion of nano-clay in polypropylene (PP). The anisotropic properties of injection molded nano-clay/PP composites were studied. The use of scCO2 with modified processing methods lead to materials which showed improvements in the mechanical properties of 78.4% compared to the pure PP matrix for a 18wt % clay loading. A further improvement in properties is expected with higher levels of nano-clay, improvements in the processing method, and the use of a highly crystalline PP matrix.
FACTS ANALYSIS" - A SIMPLE SIX-SIGMA ANALYSIS TOOL FOR TROUBLESHOOTING PROBLEMS WITH ORGANIC SURFACE COATINGS ON PLASTICS"
Troubleshooting serious problems with coatings on plastics requires quickly finding the cause. Delay can mean high costs, customer dissatisfaction and loss of reputation. To proceed rapidly an investigator must be able to select one or two most likely causes for further investigation. Facts Analysis is a useful, practical, simple tool for generating plausible possible causes and deciding which ones to pursue further. Therefore, blind alleys are avoided. An available workbook, Factory Applied Coating Troubleshooting Checklist leads the investigator through the D, the M-and most of the A of six-sigma DMAIC. It can be used by investigators of all educational backgrounds.
EFFECTS OF SCREW CONFIGURATION ON THE DISSOLUTION BEHAVIOR OF INDOMETHACIN IN EUDRAGITE PO SOLID DISPERISONS
This experimental study examines the evolution of the extent of dissolution of the active pharmaceutical ingredient (API) indomethacin (INM) into the polymer excipient Eudragit E PO (E PO) on four screw configurations. The Fourier transform infrared spectroscopy (FT-IR) results show that kneading blocks accelerate the complete dissolution process. It is concluded that the kneading blocks, which cause the processed stream to undergo chaotic laminar extensional flow and are crucial to laminar distributive mixing, may be the main necessary mixing elements for the full dissolution of the drug in the polymer melt.
GPC CONTROL OF HOT-RUNNER TEMPERATURE IN INJECTION MOLDING
Injection molding is one of the most popular polymer processing techniques in plastics industries. Hot runner has become a standard component of injection molding molds due to a number of advantages, including reduction in raw material consumption, greater production rate, and lower power consumption. Hot-runner temperature distribution plays an important role in final product quality. A multi-input-multi-output (MIMO) generalized predictive control (GPC) is developed, implemented and tested for hot-runner temperature control on a reciprocating-screw injection molding machine. Experimental results prove that GPC can control hot-runner temperature accurately.
EFFECT OF EXPANDABLE THERMOPLASTIC MICROSPHERES ON MICROCELLULAR INJECTION MOLDED POLYLACTIC ACID (PLA): MICROSTRUCTURE, SURFACE ROUGHNESS, AND TENSILE PROPERTIES
Expandable thermoplastic microspheres were employed as chemical blowing agents to produce biodegradable polylactic acid parts. The surface characteristics of the samples were evaluated with a 2D surface roughness analyzer and a white-light 3D surface profiler. It was found that microcellular injection molded parts with ETM exhibit good surface quality, similar to conventional solid injection molded parts. The tensile properties of injection molded PLA samples with variable ETM weight ratios have been investigated. As shown by the testing results, the cell microstructures play an important role in the surface quality and mechanical properties.
THE EFFECT OF BROAD ORTHOGONAL COMPOSITION DISTRIBUTION ON ENVIRONMENTAL STRESS CRACK RESISTANCE IN POLYETHYLENE
Environmental stress crack resistance (ESCR) is a critical mechanical property for polyethylene in injection and rotational molding applications. Based on a very well characterized matrix of materials with widely varying densities and melt index, we have looked at broad orthogonal composition distribution (BOCD) as a means of improving ESCR without the processability and stiffness debits. Through blending high melt index, high density components with low density, low melt index components to a target MI/ density, ESCR improvements of up to two orders of magnitude are evident over their single component counterparts.
MEASUREMENT OF INTERFACIAL TENSION AND THREAD/DROPLET KINETICS VIA POLYMER MELT MICROFLUIDICS
We present a novel platform for measurement of droplet dynamics and interfacial tension via polymer melt microfluidics (PMM). We utilize a flow focusing technique to form droplets or threads which then travel down a central channel. Upon cessation of flow, we monitor the relaxation of the droplets and threads and extract their interfacial tension. We demonstrate the technique using a polystyrene/polyamide (PS/PA) system and use the deformed droplet retraction method (DDRM) to determine the interfacial tension without any pre-processing of the samples in a confined geometry. The result agrees well with that of a previous work.
SUBSTRATE EFFECTS ON THE CONFINED CRYSTALLIZATION OF POLYCAPROLACTONE IN COEXTRUDED NANOLAYERED FILMS
This paper examines the structure-property relationships of poly (caprolactone) (PCL) nanolayers confined by various polymer substrates. AFM, gas transport, and WAXS characterizations were utilized to demonstrate that confined PCL nanolayers crystallized as large in-plane lamellae of high aspect ratio. This phenomenon, previously observed only for poly(ethylene oxide) (PEO), may be a more general phenomenon of crystalline polymers. In-plane PCL lamellae were as effective as PEO in reducing the oxygen permeability by more than 2 orders of magnitude. Additionally, the confining polymer substrate was found to affect to orientation of the PCL nanolayers due to chemical compatibility or epitaxial induced crystallization.
BIO-PLASTIC SHEETS FROM MBM PROTEINS
The processability of meat-and-bone-meal (MBM) proteins via thermal routes was investigated. Batch compounding and compression molding were used to determine optimal compositions and processing parameters. The sheets were studied for their water vapor permeability, mechanical properties and environmental aging effects. The relative humidity (RH) of the ambient air played a significant role in the processing of the compounded protein.. Sheets were formed at 40-50% RH. As expected, mechanical properties of the sheets were also found to be moisture sensitive. Particle size of MBM raw material was also found to significantly affect the texture and mechanical properties of sheets.
STUDY OF INJECTION MOLDED MICROCELLULAR POLYLACTIDE (PLA)/POLY(BUTYLENES ADIPATE-CO-TEREPHTHALATE) (PBAT) BLENDS WITH VARIOUS COMPOSITION RATIOS
Foamed PLA/PBAT blends were processed via the microcellular injection molding process using supercritical N2 as a blowing agent. The effect of composition ratio on cell morphology, thermal properties, and mechanical properties of microcellular PLA/PBAT blends was investigated. Results showed that neat PLA presented a relatively small cell size and the cell size became larger from the skin to the central area. With increasing PBAT content, the cell size also increased, while the size distribution of the cells became uniform. The thermal properties of PLA, especially Tg, were slightly affected by the addition of PBAT. The crystallization behavior was noticeably influenced.
RHEOLOGICAL MEASUREMENTS OF LOW DENSITY POLYETHYLENE (LDPE)/SUPERCRITICAL NITROGEN (N2) WITH A SLIT-DIE RHEOMETER AND THE USE OF NUMERICAL SIMULATION
In this study, the rheological behaviors of single-phase LDPE/N2 solutions at various gas contents are measured using a high-pressure slit-die rheometer. The resulting rheology data of LDPE/N2 are curve fit using the Cross-WLF model, which were then used in simulation of microcellular injection molding processes. The pressure effect on the shear viscosity is also studied. In addition, A 3D plot of viscosity as a function of shear rate, pressure and temperatures has been constructed, which is more profound at high pressures, low temperatures, and low shear rates.
10-YEAR OUTDOOR WEATHERING OF MOLDED-IN-COLOR ASA RESIN
Acrylonitrile-styrene-acrylate (ASA) alloy formulated in nineteen high chroma colors were exposed for 10 years of natural (outdoor) weathering in Florida and in Arizona, and 10,000 kJ/m2 of artificial accelerated weathering testing under ASTM G26 protocol. Exposed specimens were evaluated numerically and visually to assess the color shift, and ten out of nineteen colors demonstrated excellent color stability after 10 years of outdoor exposure. It was observed that both colorant package and weathering protocol are the key factors for determining the color durability of the formulated blends. The accelerated test appeared over-predicting color shift observed in the natural weathering tests.
EXTENSIONAL RHEOLOGY OF RAW NATURAL RUBBER FROM NEW CLONES OF HEVEA BRASILIENSIS
Natural rubber (NR) is a biopolymer whose properties depend on the structure of the 1,4-cis polyisoprene chains, non-rubber constituents, environmental conditions. NR has been characterized by traditional methods, but these cannot effectively account for clone's differences. The aim of this work is to use extensional rheology to characterize and differentiate NR samples as for clone type and season of the year. Three IAC 300 series and RRIM 600 clones of Hevea brasiliensis tapped between October 2006 and August 2008 were investigated. The extensional viscosity varied considerably and was more sensitive than any other traditional property, being fundamental for monitoring purposes.
AN ENGINEERING APPROACH TO THE CORRECTION OF ROTATIONAL FLOW CALCULATIONS FOR SINGLE-SCREW EXTRUDERS - EQUATION CORRECTION
Simulation of single-screw extruder screws using the standard pseudo-Newtonian method is known to deviate from measured performance. Part of this deviation is caused by the calculation of the drag flow rate. Previous research has shown that the calculation of the drag flow rate using this method is higher than that in the actual channel, causing the pressure gradient to be incorrectly adjusted to compensate for the error in the drag flow term. The research here provides the correction factors for rotational flow (historically known as drag flow) such that axial pressure gradients can be quickly and accurately calculated.
DESIGN ASPECTS OF DISCONTINUOUS MOLD COOLING TECHNIQUES
The use of pulsed cold water instead of tempered coolant is suggested to be a versatile and cost-efficient technique for the cooling of injection molds. But the advantages and limitations of such discontinuous cooling strategies are still a controversial issue. In this paper the behavior of a discontinuous temperature control system is analyzed. The heat balance of a test mold is monitored and the inter?ªaction of adjacent cooling circuits is identified. It is demonstrated that the appropriate placement of the sensor whose signal is used as an input variable for the temperature control system is of crucial importance.
DEVELOPMENT OF A REACTIVE EXTRUSION PROCESS FOR THE CONTINUOUS SYNTHESIS OF POLYESTERAMIDES
Polyesteramides are among degradable polymers, which are of great interest for a wide variety of applications. In this paper we report a novel reactive extrusion process for the continuous synthesis of polyesteramides. It is based on anionic ring-opening polymerization of e-caprolactam in the melt of commercially available polyester - polycaprolactone. By this means polyesteramides of different chemical compositions were successfully prepared with high yield. Process simulation was carried out using obtained process and material data.
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