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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THE INVESTIGATION OF WARPAGE BEHAVIOR BY CONSIDERING THE PROCESS-INDUCED PROPERTY VARIATION IN SEQUENTIAL OVERMOLDING
The crucial factors in multi-component molding(MCM) processes were difficult to identify with theconventional trial-and-error method due to its complicatednature and physical mechanism. Regarding the temperateconduction effect between two shots, we adopt directly atrue 3D simulation tool to investigate. The parttemperature distribution of the first shot is taken intoconsideration and affects the mold filling pattern of thesecond shot. Besides, the mechanical property of the firstshot will also influence the warpage and shrinkagebehavior of the second shot and the final product.Simulations can provide good guidelines to help peopleunderstand the mechanism and make the proper design tofabricate modern MCM products.
THERMAL FEATURE OF VARIOTHERM MOLD IN INJECTION MOLDING PROCESSES
With the development of variotherm mold temperature control, people use this technique to fit the special demands in injection molding. Not only the present mold temperature settings, but also the temperature distribution of the previous state will affect mold temperature. Especially when there are multi-layout of mold temperature controls with different heating sources and cooling sources, whole mold temperature properties would be very sensitive. As a consequence, we study mold temperature control system through CAE simulation, and discuss thermal features of different variotherm processes.
LINEAR VISCOELASTIC PROPERTIES OF N-HEXADECANE UNDER OSCILLATORY SHEAR VIA NON-MOLECULAR DYNAMICS SIMULATIONS
Small strain amplitude oscillatory shear flows of n-hexadecane fluid are performed using non-molecular dynamics simulations with sinusoidal strain. The features of the oscillatory shear flow regarding velocity profile and phase angle are presented. While the fluid is proved to exhibit linear viscoelastic behavior, its storage and loss moduli have no dependence on strain amplitude. Significantly, at different temperatures, the storage and loss moduli versus frequency curves can discriminate between the solid-like, liquid-like, and gel-like states of the fluid.
IMPROVED COLOR MIXING FOR SHEAR AND THERMALLY SENSITIVE PIGMENTS
Currently, many small twin-screw extruders cannot directly blend specific blue pre-blended composites with temperature and shear sensitive yellow pigments to produce a uniform green color. This research will show a new mixing method, one employing a singlescrew extruder joined directly to a low temperature, low shear, low pressure extensional flow mixer, to develop a 1-pass, mixing process, which creates a superior homogenous, vibrant color from dissimilar, incompatible materials. The challenge was to achieve adequate distribution and dispersion, without generating enough energy from shear, temperature, and pressure which would degrade the sensitive yellow constituent of this mix and turn it brown when degraded.
A THREE-DIMENSIONAL CAE MOLDING OF MICROCHIP ENCAPSULATION
In the packaging of plastic-encapsulated microelectronics (PEM), microchip encapsulation has been the dominant technique for encapsulation processes. With the tendency of the technologies continuously moving toward smaller scale and higher density, the existed defects problems during fabrication become more and more important. Among those problems, wire sweep and paddle shift are the most common. In this study, an integrated CAE technology which gives a comprehensive solution for microchip encapsulation has been developed. By using this technology, wire sweep and paddle shift predictions under different molding conditions can be obtained, and the simulation results also demonstrate the feasibility of our technology for practitioners to analyze their mold designs for microchip encapsulation.
MELT MEMORY AND CORE DEFLECTION
When injection molding long slender hollow parts with closed ends, like test tubes, an unevenly advancing melt front around the cores results in core deflection, a pervasive problem especially when the parts are thinwalled. Accurately predicting core deflection problems is accomplished by considering the distributed load on the core caused by the normal stress distribution acting on the cores. In this paper, the effect of fluid elasticity on core deflection is explored by incorporating melt memory into the prediction of core deflection using the upper convected Maxwell model. The Deborah number is then used to represent the dimensionless amount of elasticity. We find that melt memory significantly worsens core deflection, and we provide a chart to help practitioners predict this.
STUDIES ON THE MELTING BEHAVIOR OF POLYPROPYLENE NANO-COMPOSITES USING X-RAY DIFFRACTION AND DIFFERENTIAL SCANNING CALORIMETRY
The structural details of polymeric composites produced by melt intercalation of polypropylene and layered silicates have been investigated at process-related temperatures. Various samples from different states of the production process have been investigated at temperatures ranging from 25 to 200°C by means of X-ray diffraction. These states included pure polypropylene an unmodified (MMT) and an organically modified montmorrillonite (OMMT) a master batch (polypropylene filled with 20 wt% OMMT) and a dilute nano-composite (5 wt% OMMT). For the determination of the long period of polypropylene and of the interlayer distance of the silicate platelets small angle X-ray scattering (SAXS) was used. To define the degree of crystallization and the crystal lattice a wide angle X-ray diffraction (WAXD) was used. The structure of polymeric nano-composites was likewise confirmed by means of differential scanning calorimetry (DSC). By combining the results from both types of experiments it was possible to assign energy-related parameters to structural details.
PREPARATION AND OPTICAL PROPERTIES OF POLYSTYRENE COATED META-NITROANILINE SINGLE CRYSTALS.
In this paper the effect of varying amounts of polymer coating material on the optical properties of an organic crystal of metanitroaniline (m-NA) prepared by using different solvents such as methanol MEK and acetone by solution growth technique is investigated. The crystals were obtained with an average size of about 5 X 3 X 3 mm. These crystals were coated with polystyrene to improve their NLO properties. These crystals were characterized to investigate the observation of second harmonic generation FTIR SEM X-ray and thermal analysis. The purposes of the polymer coating are to improve surface morphology of the crystal improve LASER shot withstand capacity and improve nonlinear optical (NLO) properties corresponding to SHG intensity values. Solvent used for crystal preparation is found to have a large influence on the morphology of m-NA crystal and thus the second harmonic generation intensity values.
PROCESSING AND CHARACTERIZATION OF BLENDS OF POLY LACTIC ACID (PLA) AND SAPINDUS TRIFOLIATUS.
We investigated thermal mechanical rheological properties of a binary blend of poly lactic acid (PLA) and Sapindus trifoliatus as additive in it. The blends with different percentages of Sapindus Trifoliatus were extruded and their molded properties were examined. DSC thermograms show improvement in the crystallization. Rheological properties changed drastically with increasing percentage of Sapindus Trifoliatus. Tensile strength and modulus increased by addition of Sapindus Trifoliatus. Immiscibility was measured with thermal data. It is also observed that thermal stability of blends was lower than the pure PLA.
EVA CURING STUDY BY DSC FOR SOLAR APPLICATION
Ethylene vinyl acetate (EVA) has been used as encapsulant for solar cell application. the curing degree needs to be controlled to optimize the property. The traditional way to characterize the gel content (crosslinking degree) is by extraction using organic solvent. This method is time consuming and environmental unfriendly due to the toxic solvent. One new way to characterize gel content is by DSC. From the exothermic residue crosslink peak the gel content can be determined. The study indicates excellent correlation between these two methods. Compared with extraction method, DSC is easier and more cost efficient.
EFFECT OF HEAT AND SHEAR ON THE GELATINIZATION OF THERMOPLASTIC STARCH WITH VARIOUS PLASTICIZERS
Different compositions of starch/water/plasticizer slurries are prepared in a batch mixer followed by an equilibration time. The slurries were then subjected to different thermal and shear treatments. A rheological technique has been developed to track the influence of shear on the gelatinization process and the results are also supported by DSC and polarized light microscopy for static systems. Shear has a dramatic effect on gelatinization and the dependence of the onset and conclusion temperatures with slurry composition vary widely depending on the type of plasticizer used.
MECHANICAL PROPERTIES OF ELECTROSPUN COMPOSITES AND THEIR CRYSTALLINITY MEASUREMENTS USING X-RAY DIFFRACTION
Electrospinning method was used to produce nanoscale polymer fibers. The mechanical properties and toughness of the hydroxyapatite (HAP) reinforced poly(- caprolactone) (PCL) electrospun fibers were evaluated.The mechanical response of the electrospun composites was compared with that of the non-spun compression molded composites and it was determined that mechanical properties and the toughness values were enhanced when the materialƒ??s dimensions are reduced to the nanometer length scale. The crystallinity of the spun and the non-spun composites were determined using wide angle x-ray diffraction and the effect of crystallinity was assessed.
DIRECT ISOLATION OF BIFUNCTIONAL POLYPHENYLENE ETHER COPOLYMER
A bi-functional polyphenylene ether copolymer is produced by oxidative coupling polymerization of 2,6 xylenol and TMBPA (Tetra Methyl Bisphenol A). The reaction takes place in a solvent, such as toluene, which needs to be removed in an ƒ??isolationƒ? processing step. The isolation can be done by precipitation of the copolymer with an anti-solvent such as isopropanol or by direct" isolation in a devolatilization extruder. This pape rde-scribes the devolatilization extrusion operation of low viscosity copolymer. Process conditions to control the desired residual solvent content in the product were investigated and the effect on the copolymer properties is reported."
EFFECTS OF HIGH INTENSITY SONICATION ON AN EPOXY RESIN: PRE- AND POST-CURE BEHAVIOR
The ultrasonic cavitation approach for the fabrication of polymer nanocomposites has proven effective for particle dispersion which improves the thermomechanical properties. However the effects of probe-style cavitation on the behavior of the polymer itself are not completely understood. While FTIR data show increased functional group intensity DSC measurements confirm no decrease in glass transition for EPON 862. It appears that sonication increases the storage modulus of epoxy especially at low temperatures though the maximum increase was observed for a sample which was sonicated for 5 minutes.
CONJUGATED POLYMER PHOTOVOLTAIC SOLAR CELLS MANUFACTURING AND INCREASING PERFORMANCE
Due to their lighter weight, conjugated (semiconducting) polymer cells have a potential of displacing conventional silicon cells. The most studied conjugated polymer solar cell is the bulk heterojunction cell. Here, the active layer is made up of a mixture of the conjugated polymer donor and the C60 based - fullerene acceptor. The efficiency of the cell is determined, using a solar simulator and the AM1.5G standards, after determining existence of an open circuit voltage (Voc) and short circuit current. Using Design of Experiments (DOE), Voc has been maximized. The variables considered in the DOE were solvent type, number of layers of PEDOT:PSS and polymer/fullerene mix, as well as spin-coating times and speeds, and annealing time, temperature and applications per cell layer. Other variables such as LiF insertion, electric or magnetic fields, nano-rods and nano-tubes will be studied in the future.
PHOTODEGRADATION OF ?-NUCLEATED POLYPROPYLENE
The paper deals with the effects of nucleation on photodegradation of isotactic polypropylene. The starting polymer was modified by a specific ?- nucleating/clarifying agent Millad 3988 based on 1 3;2 4-bis(3 4-dimethylbenzylidene) sorbitol. Several concentrations were applied. Samples prepared by compression moulding were then exposed to UV-irradiation. Infrared spectroscopy showed that the degradation kinetics is similar for all the samples. Melting and crystallization behaviour of irradiated samples was followed using a differential scanning calorimetry. In all cases UV-irradiation led to decrease of melting/crystallization temperature as a result of polymer degradation. The surface cracking was observed using polarized light microscopy. The network of the surface cracking was significantly different for neat and nucleated samples. Introduction
PHOTODEGRADATION OF ?ñ-NUCLEATED POLYPROPYLENE
The paper deals with the effects of nucleation on photodegradation of isotactic polypropylene. The starting polymer was modified by a specific ?ñ- nucleating/clarifying agent Millad 3988 based on 1,3;2,4-bis(3,4-dimethylbenzylidene) sorbitol. Several concentrations were applied. Samples prepared by compression moulding were then exposed to UV-irradiation. Infrared spectroscopy showed that the degradation kinetics is similar for all the samples. Melting and crystallization behaviour of irradiated samples was followed using a differential scanning calorimetry. In all cases UV-irradiation led to decrease of melting/crystallization temperature as a result of polymer degradation. The surface cracking was observed using polarized light microscopy. The network of the surface cracking was significantly different for neat and nucleated samples.
INCREASED ELECTRICAL CONDUCTIVITY FROM REDUCED CARBON NANOTUBE CONCENTRATIONS USING EXTENSIONAL FLOW MIXING
Carbon nanotubes (CNTs) are extraordinarily expensive, and reduced concentration solutions are sought which retain critical physical properties, especially electrical conductivity. Currently, electrical conductivity requirements usually exceed conventional twin-screw mixing capabilities, forcing processors to use higher concentrations of CNTs, or revert to the use of chemicals, additives or wet polymerization. This research covers tests and provides data on a new extensional flow mixing method designed to increase particle distribution and dispersion by performing hundreds of repetitive extensional flow cycles over a 20 second residence time, thereby significantly achieving high conductivity while decreasing CNT concentration requirements by over 40%.
QUALITY CONTROL OF POLYMER PRODUCTS THROUGH SPECTRAL IMAGING AND CHEMOMETRICS METHODS
Spectral imaging is increasingly used to develop rapid and non-invasive analytical sensors in a variety of fields. This paper discusses the ability of chemometrics methods such as multivariate image analysis (MIA) and wavelet texture analysis (WTA) to extract meaningful information from spectral images enabling the user to monitor subtle spatio-temporal variations in thin polymer materials. Three case studies are proposed to illustrate the method: (1) detecting subtle crystallinity variations across pure polymer films (2) studying extrusion dynamics of wood/plastic composites making it possible to follow the mechanical properties on-line and (3) predicting the mechanical properties of polymer blend films using both spatial and spectral features. These case studies show that spectral imaging can effectively be used identify local property variability and help in overall process control.
QUALITY CONTROL OF POLYMER PRODUCTS THROUGH SPECTRAL IMAGING AND CHEMOMETRICS METHODS
Spectral imaging is increasingly used to develop rapid and non-invasive analytical sensors in a variety of fields. This paper discusses the ability of chemometrics methods, such as multivariate image analysis (MIA) and wavelet texture analysis (WTA), to extract meaningful information from spectral images, enabling the user to monitor subtle spatio-temporal variations in thin polymer materials. Three case studies are proposed to illustrate the method: (1) detecting subtle crystallinity variations across pure polymer films, (2) studying extrusion dynamics of wood/plastic composites making it possible to follow the mechanical properties on-line, and (3) predicting the mechanical properties of polymer blend films using both spatial and spectral features. These case studies show that spectral imaging can effectively be used identify local property variability and help in overall process control.
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