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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HIGH-SHEAR-RATE RHEOLOGY OF POLYSTYRENE MELTS
This work presents a systematic analysis on the capillary rheology of polystyrene melts under high shear rates ranging from 103 to 106 s-1. The precise Bagley correction was achieved by means of the enhanced exit pressure technique. The end pressure drop was found to predominate over the Bagley-corrected capillary pressure drop in the high shear rate range. Furthermore, the dissipation heating, pressure dependence, and compressibility effects were quantitatively evaluated. Results implied that the apparent nonlinearity of the Bagley-corrected capillary pressure drop versus apparent shear rate profile, which occurred at the shear rates of above 105 s-1, mainly resulted from the dissipation heating. In the shear rate ranges investigated, the corrected rheological behavior could be adequately described by the power law.
MONITORING OF THERMAL HOMOGENEITY IN SINGLE SCREW EXTRUSION USING INFRARED TEMPERATURE SENSORS
The ability of infrared temperature sensors to provide information relating to the thermal homogeneity and melting performance of single screw extruders has been investigated. Infrared sensors were located in the barrel of a single screw extruder close to the end of the screw and in an instrumented die adaptor. Results were compared to those obtained from a thermocouple grid sensor located at the entrance to the extruder die. Two grades of high density polyethylene were used in experiments with three extruder screw geometries at a range of screw speeds. When located in the die adaptor, the infrared sensor detected temperature fluctuations related to melting instabilities but these were smaller in magnitude than the actual fluctuations detected by the thermocouple grid sensor due to the limited penetration depth of the infrared sensor. When located in the extruder barrel the infrared sensor provided a bulk measurement of melt temperature across the depth of the screw channel in the metering section which correlated more closely with that measured using the thermocouple grid.
COMPUTER SIMULATION OF FLOW BALANCE IN THE DIE OF SLOT COATER: PART 1: LAND GEOMETRY
Coating operations such as spin coating, curtain coating, role coating, slide coating, slot coating, and etc. are dated from long time ago and still considered very important processing. Slot coating is considered very important specially for the manufacturing of liquid crystal display parts. Photo resistant is coated on the glass and is sent to next process to make TFT board. Coating quality such as uniformity of coating thickness can be divided into two categories, which are machine direction quality and transverse direction quality. Machine direction quality is related to die lip design and operation conditions whereas the transverse direction quality is related to flow uniformity inside of the die. The flow uniformity is governed by flow balance in the die. The most important design factors for the inside die geometry are manifold and land. Through this study the flow balance according to the land design has been examined by computer simulation. The parameters for land design are length and shape. Exit velocity at the outlet of die is different from land designs. The best land design has been investigated in this study.
SUPERCRITICAL FLUID DOSAGE CONTROL USING ARTIFICIAL NEURAL NETWORK (ANN) FOR MICROCELLULAR INJECTION MOLDING
Supercritical fluid (SCF) dosage is one of the most important parameters for microcellular injection molding. Highly accurate and repeatable SCF dosage is required to ensure high part quality and consistency. In this study, an artificial neural network (ANN) based SCF dosage control strategy was proposed to predict and compensate for the possible variations in the coming SCF dosing stage to achieve a more repeatable SCF dosage. The result shows that this control strategy can be successfully implemented, and that it leads to significant improvements in dosage consistency and part quality.
COMPATIBLIZED POLYPHENYLENE SULFIDE/LIQUID CRYSTAL POLYMER ALLOY FOR ELECTRICAL&ELECTRONIC APPLICATIONS
The combination of polyphenylene sulfide (PPS) and liquid crystal polymer (LCP) in polymer blend is a potential way of creating new polymer properties. However, the two polymers are incompatible, and typical physical blends do not realize synergistic performance. Herein we report a compatiblized PPS/LCP alloy. Morphology and thermal analysis confirm the improved compatibility of PPS and LCP. As a result, mechanical properties of the compatiblized PPS/LCP alloy are improved. In particular, the notched Izod impact improves by 45% and weld line strength improves by 37% compared to PPS/LCP physical blend. The surface quality as measured by surface gloss of the compatiblized alloy is also improved significantly. In addition, the compatiblized PPS/LCP alloy is halogen free according to IEC 61249-2-21 standard and meets V-0 flammability of the UL-94 standard. Such compatiblized PPS/LCP alloy is an ideal material for electronics applications such as connectors and printer parts.
ULTRA-HIGH THERMALLY TREATED LLDPE NANOCOMPOSITES: TRANSPORT PROPERTIES AND ELECTROMAGNETIC SHIELDING
The electromagnetic shielding effectiveness (EM SE) and the electrical properties of ultra-high thermally treated carbon nanotubes/nanofibers in LLDPE matrix were evaluated. EM SE displayed dependence on electrical resistivity and electrical permittivity. Nanocomposites at 60wt% nanomodifier content showed EM SE values as high as 67 dB at 1.5GHz. The primary shielding mechanism in these nanocomposites was absorption. Therefore, such nanomaterials have potential use in electromagnetic compatibility applications.
PROGRESS ON SIMULATING LONG-GLASS FIBER ORIENTATION IN COMPLEX MOLDING GEOMETRIES
The mechanical properties of fiber reinforced materials are highly dependent on fiber orientation generated within the composite during molding operations. Rheologically obtained parameters for fiber suspensions are applied to current models to predict fiber orientation in complex geometries independent of experimental considerations. This method provides an a priori pathway to determine fiber orientation based solely on rheological testing of the suspension and independent of the mold geometry. Furthermore, predictions for fiber orientation are carried out using the traditional rigid fiber Folgar-Tucker model as well as the semi-flexible Bead-Rod model which allows for the inclusion of fiber bending to be taken into account often witnessed in long-glass fiber (LGF) systems. Computations for fiber orientation are performed for center-gated disks and predictions with the two above models are compared to experimental data.
HIGH PERFORMANCE METALLOCENE POLYETHYLENE BASED ON SK INNOVATION’S NEXLENE™ TECHNOLOGY
SK innovation has developed a new polyethylene technology, Nexlene™, capable of producing from mPOE to mHDPE based on SK’s novel metallocene catalyst. The process technology is based on a solution process and therefore is capable of producing octene-1 copolymers. Additionally, the bimodal process allows for product tailoring via adjusting the molecular weight distribution and co-monomer distribution. So we can obtain high performance Nexlene™ products with superior general physical properties, transparency, processibility, and organoleptic properties.
VIRTUAL PROTOTYPING APPLIED TO A BLOW MOLDED CONTAINER
This study shows how the parison of a large (1000 liters) blow molded water container can be optimized (programmed) to improve its mechanical performance as related to hydrostatic loading while keeping the weight of the part to a minimum. This case study is composed of two parts. The first (baseline) case is aimed at validating the computational model by comparing the material distribution predicted by the model with available experiments. As an input to the baseline simulation, the initial thickness variation along the parison was obtained from direct measurements from the field and used for the baseline case. The final material distribution obtained from the blow molding simulation is then compared to those of the real part. A structural analysis is next performed using static implicit FEA to predict the container's performance when it is completely filled with water and enclosed in a steel cage. The objectives are to compute the total deformation, and the total (von-Mises) stresses. The variable material distribution obtained from the blow molding step is used in the structural model. In the second part of the case study, the initial parison thickness used in the field was challenged and optimized. The objective of the optimization (programming) was to find out the minimum initial thickness of the parison that will increase the minimum final thickness to a desired value. The optimized container is lighter than the original design by 10% while at the same time being more rigid.
STRUCTURE AND PERFORMANCE OF MULTILAYER NANOCOMPOSITES FILMS
In this study, we investigated the structure and properties of multilayer films with a nanocomposite core layer. The core layer materials considered were polypropylene (PP), polylactic acid (PLA) and polyamides (PA-6) and the side layers were polyethylenes (PE). The multilayer films were obtained from the extrusion cast or film blowing processes. The structure of the films was investigated using microscopy, X-ray diffraction and differential scanning calorimetry. The properties studied were the mechanical properties in terms of modulus, strength and elongation in addition to tear, haze and barrier properties of the films. The effect of nanoclay content in the range of 1 to 7.5 wt% was investigated. In terms of structure, it was found that the clay platelets aligned in the films plane. Exfoliation was observed for the PA nanocomposite systems, some intercalation was observed in the case of PLA-nanoclay and no change in the clay spacing was observed in the case of PP-nanoclay system. For the performances, it was generally found that the presence of clay enhanced the modulus, tear and barrier properties, but little change was observed in the other properties. The barrier properties correlated with the state of dispersion of the clay platelets. Multilayer films with PA nanocomposites showed the highest barrier to oxygen permeation.
FILM INSERT MOLDING BASED ON POLYOXYMETHYLENE AND POLY(LACTIC ACID): MORPHOLOGY AND MECHANISM OF INTERFACIAL ADHESION
Film insert moldings were fabricated by using PLA as film and POM copolymers with various oxyethylene repeating units. The interfacial adhesion properties between film and substrate were determined by micro-cutting analyses. POM containing high oxyethylene content shows superior adhesive strength than those with low oxyethylene content. The growth of the POM-PLA mix layer was explained by mechanism of “negative pressure” in POM phase attributed by POM crystallization and partial miscibility between POM and PLA.
A NEW STERILIZABLE HIGH TEMPERATURE POLYETHERIMIDE BLEND FOR HEALTHCARE APPLICATIONS
A transparent, high temperature thermoplastic Polyetherimide (PEI) resin blend with improved impact resistance and enhanced hydrostability has been developed for healthcare applications. The two-phase resin blend can be sterilized using traditional methods such as high temperature autoclave, ethylene oxide, gamma radiation, as well as STERRAD® NX®, a low- temperature hydrogen peroxide plasma sterilization process. Injection molding of the new resin blend and mechanical property and color retention after sterilization is described and compared to polyphenylsulfone (PPSU).
VERIFICATION OF EXPERIMENT AND NUMERICAL METHOD SIMULATION ON VENTING DESIGN FOR IMPROVING PRODUCT SURFACE QUALITY
In this study the effect of injection mold venting design combine with CAE simulation results to improve the product surface quality was verified. Various venting design (numbers and locations) and injection speed (100, 200, 300 mm/s) were used in the experiment. The melt flow evolution was verified by a numerical simulation method. The developed pressure of trapped air inside cavity was derived and associated with part surface quality. Highly compressed trapped air from high injection speeds led to poor surface quality due to burning of material. For solving the burning mark and surface quality improvement, venting locations and sizes could thus be determined from experimental and simulation results to offer adequate venting.
COMPUTER SIMULATION OF FLOW BALANCE IN THE DIE OF SLOT COATER: PART 2: MANIFOLD GEOMETRY
Coating operations such as spin coating, curtain coating, role coating, slide coating, slot coating, and etc. are dated from long time ago and still considered very important processing. Slot coating is considered very important specially for the manufacturing of liquid crystal display parts. Photo resistant is coated on the glass and is sent to next process to make TFT board. Coating quality such as uniformity of coating thickness can be divided into two categories, which are machine direction quality and transverse direction quality. Machine direction quality is related to die lip design and operation conditions whereas the transverse direction quality is related to flow uniformity inside of the die. The flow uniformity is governed by flow balance in the die. The most important design factors for the inside die geometry are manifold and land. Through this study the flow balance according to the manifold design has been examined by computer simulation. The design variables of manifold were manifold volume and manifold shape. Well designed manifold gives good flow balance in the die land and consequently gives good coating uniformity. Good manifold design has been investigated by computer simulation.
ESTABLISHMENT OF A GAS-ASSISTED INJECTION MOLDING SYSTEM FOR WAX INJECTION IN INVESTMENT CASTING
This study combines two processes. A one dimensional tube was used to investigate the gas penetration characteristics including penetration length and hollowed-core ratio under varied parameters including gas delay time, short shot and wax temperature. The wax properties were tested by importing the CAE software to simulate the wax filling and gas penetration length. The experimental results show gas-assisted injection molding is successfully applied to wax injection. Simulation results for wax filling and gas penetration are in agreement with the experimental results except for gas pressure, due to the viscosity deviation.
FUNCTIONALITY IN MULTILAYER FILMS FOR PACKAGING
During the last decades, the food, pharmaceutical and many other industries have seen several changes in packaging technology and applications because of new consumer demands and market trends. These drivers can be summarized as requirements for high quality, freshness and extended shelf-life of products, with easy-to-use and resistant packaging made with lighter, cheaper and recyclable materials. On the other hand, public demand and awareness for food safety has become a significant concern. This has even intensified on the recent regular outbreak of Listeria and Salmonella bacteria in various area of the world, following the consumption of contaminated meat and cheese products. The outbreak has prompted the public awareness to question food quality in stores and technological solutions that could prevent contamination and/or alert consumers may provide better public protection. Finally, the global market for materials and films used in packaging is very large. When decomposed into various segments such as controlled, active, and smart or barrier packaging, the volumes used and annual growth rates are significant in addition to other concerns such as sustainability. The performance of polymer films and multilayer packages are the result of the microstructure that is imparted to the material as a result of complex interactions between the resin and the thermo- mechanical history that it experiences during processing. This microstructure is strongly influenced by molecular parameters of the resins used (molecular weight, molecular weight distribution, branching, co-monomer type and content, etc.), their layout in multilayer structures and the additives used as well as the rheological, thermodynamic, thermal properties and the crystallization kinetics under the processing conditions. In the past, most of the studies were directed to the improvement of structural properties of films and multilayer structures (mainly mechanical: strength, tear, toughness etc...) and muc
A STUDY ON THE SCRATCH RESISTANT CHARACTERISTICS OF INJECTION MOLDED POLYCARBONATE PARTS
Polycarbonate (PC) is one of the engineering plastics and it has high mechanical properties and transparent characteristics. PC is widely used for the outer case of mobile electronic products and lamp covers for automobile, and so on. However it has a weakness in low surface hardness, which is a low scratch resistant property. Scratch resistant property is considered very important specially for the outer case usage. Scratch resistant property is evaluated by pencil hardness. It was observed that the pencil hardness of injection molded PC sheet was dependent of its surface roughness. The specimen having convex or concave shaped surface had high pencil hardness. Deformation and stress concentration on the specimen surface have been analyzed during the pencil hardness test through computer simulation. Convex and concave shaped surface showed small deformation compare with flat surface. This made pencil hardness high. The surface of injection molded product can be controlled by controlling mold surface. Consequently the high pencil hardness can be achieved by designing the surface roughness of mold surface.
NEW NON-HALOGEN FLAME RETARDED BIO-DERIVED POLYMER BLENDS DEVELOPMENTS
The use of polylactic acid (PLA) in durable applications such as appliances and computers has been limited by PLA’s inherent property shortcomings, such as low impact strength, low heat distortion temperature, and lack of flame retardancy. These issues have been overcome via blending with engineering plastics, applying new compatibilization technology and using unique flame retardant additives. The resultant compositions have an excellent balance between heat resistance, impact resistance and flame retardancy. One such composition achieves a UL 94 rating of V-0 at 1.6 mm thickness, a notched Izod impact value at room temperature up to 11.6 ft-lbs/in and also exceeds a threshold of 100°C in heat distortion temperature (HDT) at 66 psi load. This bio-derived blend with >30% bio-content has exceptional properties and has taken PLA into the realm of engineering plastics. These enhancements will enable PLA to replace petrochemical- based materials in many demanding durable applications.
OBSERVATION AND ANALYSIS OF DEFROMATION AND FAILURE MECHANISMS OF ORIENTED POLYMERIC FOAM MATERIALS
Various models of foam deformation have been formulated during last decade, but most of the models make use of basic concepts of continuum mechanics in combination with finite element method with limited consideration of specific micro-mechanisms of foam deformation and fracture. Three types of deformation and fracture mechanisms of oriented foams were classified: 1) Large reversible deformation, 2) Large elasto-plastic deformation and 3) Brittle fracture of faces and/or edges of individual cells. In this paper, five polymeric materials which have completely different deformation behaviors are selected and their fracture behavior was observed by scanning electron microscope. Among them, three polymeric foams with distinctively different deformation and fracture mechanisms are selected based on the classification for detail analyses.
THE EFFECT OF GLASS FIBER LENGTH ON ORIENTATION DISTRIBUTION WITHIN INJECTION MOLDED COMPOSITES
The Method of Ellipses has been applied to short and long fiber polymer composites to evaluate fiber orientation. The resulting orientation distributions are compared at various percentages of fill for injection molded center-gated discs. Preliminary results suggest that an increase in magnitude in fiber length leads to significantly reduced fiber orientation in the radial direction (Arr). There is little effect on the Arz component of the orientation tensor, however, except at large percentages of fill.
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