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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VERIFYING AND IMPROVING THE PLASTIC DEFORMATION OF AUTOMOTIVE INTERIOR PARTS AT EARLY DESIGN STAGE
In the plastic injection molded product development and fabrication, warpage is one of the crucial problems to dominate product quality. In general, the integration of product design, mold design, material selection, and various operation conditions has been regarded as the major factor to warpage. However, the real major effects on the warpage are still not fully under control. In this study, two methods are adopted to systematically investigate warpage quality. One is based on manually flow domain modification under CAE simulation direction and the other is benefited from DOE suggestion of process condition revision. Following the flow behavior guideline, the warpage of original design was improved over 50%, due to suitable pressure compensation to the shrinkage. Meanwhile, according to DOE result, it shows mold temperature is one of the most sensitive parameter. After using the suggested parameters from DOE, the poor warpage problem was also be improved up to 50%.
PROCESSING WINDOW FOR SWIRL-FREE MICROCELLULAR INJECTION MOLDED POLYETHYLENE (LDPE) AND POLYPROPYLENE (PP) PARTS USING SUPERCRITICAL NITROGEN (N2) AS A BLOWING AGENT
The surface swirl-marks on foamed plastic parts is an important issue with microcellular injection molding. Based on nucleation theories and experimental results, processing temperature windows for microcellular injection molded LDPE/N2 and PP/N2 parts were established. Comparisons of the predicted processing windows with the experimental results showed good agreement. Thus, based on these processing windows, the appropriate combination of gas dosage and processing temperature, which leads to swirl- free parts for microcellular injection molding, can be determined.
THE INFLUENCES OF PROCESSING TEMPERATURES AND NUCLEATING AGENT IN FOAMING OF A THIN-WALLED INJECTION MOLDED PART
The injection foam molding of a thin-walled polypropylene part of 1 mm thickness at low, moderate, and high melt temperatures using carbon dioxide, with and without talc, was conducted and the effect of process temperatures and nucleating agent on the cell morphology was thoroughly investigated. The results indicated that by using a modified gate geometry and proper control of the process parameters, a uniform microcellular fine-celled part could be successfully produced. Furthermore, the analysis of foams results produced at different temperatures, with and without talc, showed that in microcellular fine-cell foaming of thin-walled injection molded parts, temperature effect is more dominant.
ISOTHERMAL CRYSTALLIZATION-INDUCED FOAMING OF POLYPROPYLENE UNDER HIGH PRESSURE CARBON DIOXIDE
Crystals can strongly influence plastic foaming behavior, final foam structure and properties. Using an improved visualization system, foaming process of polypropylene was captured and compared with differential scanning calorimetry analysis. It was observed that crystals nucleated and grew into spherulite. At low temperatures, cell nucleation occurred at crystals’ boundaries due to CO2 exclusion from crystal growth fronts and increase in tensile stresses in surrounding amorphous regions. At higher temperatures, these two mechanisms became less apparent.
A STUDY ON RECYCLING OF POLYHYDROXYBUTYRATE (PHB) COPOLYMER AND ITS EFFECT ON MATERIAL PROPERTIES.
This study focuses on the ability of PHB copolymer to be processed a number of times and use of different virgin to regrind ratios. This work studied the effect of regrind levels and heat history on material properties of PHB Copolymer. The material was recycled for 10 regrind generations and also was studies for 7 regrind ratios with virgin material. 79% reduction in viscosity and 10% reduction in ultimate tensile strength were observed for 10 regrind generation. Also a drop of 5% was observed in the viscosity and ultimate tensile strength with a 50:50 virgin to regrind ratio.
INVESTIGATION OF SUPERCRITICAL FLUID-LADEN PELLET INJECTION MOLDING FOAMING TECHNOLOGY(SIFT)
A novel method of producing injection molded parts with a foamed structure has been developed. Compared with conventional microcellular foaming technologies, it lowers equipment costs without scarifying the production rate, making it a good candidate for mass producing foamed injection molded parts. In this study, further research on this method was conducted including: (1) comparison of different physical blowing agents, (2) shelf life of carbon dioxide laden pellets, and (3) optimization of the process conditions
EFFECTS OF UNSUPPORTED WALL HEIGHT ON LINEAR VIBRATION WELDING OF PMMA TO ABS
Vibration welding is very popular in the automotive industry due to the short cycle time and high quality joints. It is frequently used in welding of PMMA lenses to ABS backing in automotive tail lights. The welding fixtures are designed to accommodate dimensional variations in the parts often resulting in welding of long and tall unsupported walls. Therefore, linear vibration welding of vertical PMMA plates to horizontal ABS plates in a T-joint with the vibration motion being transverse to the PMMA plate was studied. The effects of unsupported wall height of PMMA, amplitude of vibration, meltdown, and pressure on joint strength were evaluated. As expected, for short unsupported walls high quality welds with short weld times were produced. However, as the wall height increased, longer weld times were required to produce welds until the height was so large that the PMMA plate would bend rather than produce relative motion at the interface.
PACKING PARAMETERS EFFECT ON INJECTION MOLDING OF POLYPROPYLENE NANOSTRUCTURED SURFACES
In today´s industry, applications involving surface patterning of sub-µm to nanometer scale structures have shown a high growth potential. To investigate the injection molding capability of replicating sub-µm surface texture on a large scale area, a 30x80 mm2 tool insert with surface structures having a diameter of 500 nm was employed. The tool insert surface was produced using chemical-based-batch techniques such aluminum anodization and nickel electroplating. During the injection molding process, polypropylene (PP) was employed as material and packing phase parameters (packing time, packing pressure) were investigated. The replicated surface topographies were quantitatively characterized by atomic force microscopy using specific three-dimensional surface parameters and qualitatively inspected by scanning electron microscopy. Results showed that the degree of replication from the toll to the polymer part was mainly influenced by packing pressure level and distance from the gate.
DEPENDENCE ON MELT VISCOSITY OF FOAM PC/ABS INJECTION MOLDING AND MECHANICAL PROPERTY
This research has developed a novel PC/ABS blend foam injection moldings by focusing on the relationship between foaming agent, PC/ABS ratio, melt viscosity and mechanical properties in foaming PC/ABS materials. Higher melt viscosity exhibited high notched impact strength and smaller microcellular foam internal structure. Moreover, ABS could act as foam nucleating site so that the increment of ABS contents would increase foam internal structure, which benefit for light weight materials with high impact performance.
FRICRIVETING OF CIVIL ENGINEERING COMPOSITE LAMINATES FOR BRIDGE CONSTRUCTION
This article presents a feasibility-study of the new joining technology Friction Riveting (FricRiveting) on glass fiber reinforced thermoplastic composites and lightweight alloys. Glass fiber reinforced polyetherimide and titanium grade 2 were selected as an alternative solution for truss girder connections in composite bridge construction. Joints without extensive damaging of the fiber network were selected for mechanical testing based on their heat input generation. Fairly strong joints with tensile strengths within 1900 to 4000 N were achieved in this preliminary study. Tensile strength could be directly associated with the anchoring performance of the deformed tip of the rivet. The higher the Aspect Ratio (the penetration of the rivet divided by the width of the deformed rivet tip) the stronger were the joints. Fracture analysis of the tensile specimens revealed a new failure type (full rivet pullout) not observed in previous works. Further process optimization is required to achieve the levels observed for non-reinforced thermoplastic polyetherimide.
FOAMING OF POLY(ETHYLENE-CO-OCTENE) WITH SUPERCRITICAL CARBON DIOXIDE ACROSS ITS MELTING RANGE
The objective of this work is to devise a strategy to produce high quality poly(ethylene-co-octene) foams through the study of the crystallization behaviors of foams attained across the melting range of the material. Experiments were conducted in a batch-foaming apparatus at different saturation temperatures and pressures. Through proper control of processing parameters, and thereby crystallization behavior and melt strength of the polymer matrix, POE foams with a micro-cellular morphology of 1.3x109cell/cm3 were achieved.
MOLECULAR NETWORK CONNECTIVITY IN EPOXY-AMINE THERMOSETS
Nanoscale interrogation of the fracture surfaces of cured epoxy systems has revealed the presence of non- homogenous network structures. This complicated network structure contains areas with varying levels of crosslink density. The connectivity of the network drives important material parameters such as mechanical properties and solvent and water permeation. This work presents an analysis of the network development of a typical aerospace- grade epoxy system with special attention paid to the influence of network connectivity on the fracture toughness.
POLYMER PARTICLE INTERACTIONS IN NANOCOLLOIDS
The rheological properties of complex fluids has been one of the interesting research subject due to the macroscopic behaviour (namely shear thinning and shear thickening) exhibited when they are subject to shear force. All concentrated suspensions under right conditions can exhibit the non-Newtonian flow behaviour, however, the required conditions and the underlying mechanism are not well understood in literature. To this respect, this study systematically investigates the effects of physicochemical parameters on the flow behavior of colloidal nanoparticle suspension (CNS) to shed a light on the mechanism behind the shear thickening behavior of CNS. We have also presented the outcomes of experimental studies of CNS with a low particle volume fraction, and anisotropic and flocculated microstructures through measuring their viscosity and electrical resistance under various shear forces together with utilizing several relevant characterization methods (i.e., Dynamic Light Scattering, Transmission Electron Microscopy and Capacitance Measurement). It is observed that studied CNS display shear thickening/thinning flow behavior depending on their microstructure forms due to the interaction forces among particles and associated changes in floc sizes, which are controlled by the shear induced hydrodynamical forces. The detailed valuation of the experimental results indicates that the shear thickening phenomena in low volume fraction, anisotropic and flocculated systems is mainly attributed to the increase in the total surface area and the effective volume fraction of particles due to both hydrodynamic and interparticle forces.
A STUDY ON THE ACOUSTIC PERFORMANCE OF BIO-BASED COMPOSITE FOAMS OF PLA AND PHBV
Bio-based foams are the solution to environmental concerns regarding petrochemical-based foams. However, bio-based foams possess weak structure. To increase the potential of replacing current petrochemical foams, mechanical characteristics of bio-based foams need to be improved. This paper studies the effect of blending two bio-based polymers on mechanical and acoustic properties of resulting polymer composite foams. Blends of Polylactide (PLA) and polyhydroxybutyrate-co-valerate (PHBV) were foamed and characterized in terms of acoustic, mechanical properties and foam morphology.
DEVELOPMENT OF BEAD FOAMING TECHNOLOGY FOR HIGH PERFORMANCE PEEK. 1.THERMAL ANALYSIS
In this paper the evolution of double peak melting behavior of PEEK was investigated for bead foaming purposes. A regular differential scanning calorimetry (DSC) and a high pressure DSC were used to simulate the double peak generation without and with the dissolved CO2, respectively, to simulate the bead foaming. The effect of saturation temperature saturation pressure, and saturation time were investigated in this simulation. It was found that the required saturation temperature to obtain an appropriate double peak structure decreases by increasing the saturation pressure.
PARTICLE SIZE AND CONCENTRATION EFFECTS ON MECHANICAL PROPERTIES OF POLYETHER BASED TPU/SILICA NANOCOMPOSITES
Polyether based thermoplastic polyurethaneurea (TPU)/silica nanocomposites were prepared and characterized. Poly(tetramethylene oxide) glycol (PTMO-2000), Polyethylene glycol (PEG-2000) based TPU with 20 and 30 % urea hard segment content was synthesized and used for the current study. Silica nanoparticles were prepared according to Stöber method in 2-propanol. Thermal and mechanical properties of novel PTMO-base TPU/silica nanocomposites with silica loadings of 1-40% by weight and with average silica sizes of 20-180 nm at constant loading % were determined. The effects of (i) amount of silica loading and (ii) size of silica on thermal and mechanical properties of the resultant thermoplastic nanocomposites were investigated by infrared spectroscopy, differential scanning calorimetry, scanning electron microscopy techniques, and stress-strain and nanoindentation tests. It was shown that even distribution of silica in PTMO-based TPU polymers influenced the thermal and mechanical properties of nanocomposites with respect to both filler content and filler size. Incorporation of silica nanoparticles with lower particle size provided higher modulus and tensile strength and led to a stiffer structure of TPU/silica nanocomposites while retaining their elastomeric properties.
EFFECTS OF PROCESSING PARAMATERS ON COLOUR MISMATCH DURING COMPOUNDING
In the present study, the effect of three processing parameters, temperature, screw speed, and feed rate, was investigated for polycarbonate compounding. The parameters were varied individually to five different levels to analyze their effect on color formulations. An intermeshing twin-screw extruder (TSE) was employed for the three different grades associated with the same color being used on site at SABIC IP in Cobourg, Ontario. The compounded polycarbonate were molded into flat coupons, which were then analyzed for their CIE L*, a*, and b* values, measured with a spectrophotometer. Historical data was obtained and analyzed using Stat-Ease Design- Expert® software for Analysis of Variance (ANOVA). The effects of these processing parameters were studied to evaluate their effect on three different grades.
POLYMER SCIENCE AND ENGINEERING IN COSTA RICA
The plastic industry in Costa Rica has been well positioned starting with the fabrication of plastic bags for commercial usage and banana plantations around sixty years ago. Currently there are in Costa Rica about one hundred companies which include certain type of polymer transformation into their operations. These companies can be found in fields like packaging, appliances, medicine, computer processors, textiles, and construction, to mention only few of them. Engineers hired for these companies are mainly industrial, mechanical and chemical engineers with few or null knowledge in polymer science and engineering. It is because of this that thirty years ago the only polymer college program currently in Costa Rica was established at the School of Chemistry of the Universidad Nacional (UNA). The program initially was called Research of Agro Industrial Resources, focused on the extraction of high-value lignocellulosic materials from agro industrial residues of coffee, banana, or pineapple processing. The program changed its name to Laboratory of Polymer Research and Technology (abbreviated as POLIUNA) and has evolved to research on synthetic polymers and polymer composites over the years. More recently, the laboratory has been involved in several scientific projects concerning nanoscience and nanotechnology with applications in materials, medicine and biotechnology.
SIMULATION OF THE FOUNTAIN FLOW EFFECT BY MEANS OF THE RADIAL FUNCTIONS METHOD (RFM)
The fountain flow effect has important implications in the quality of injection and compression molded parts: it affects the orientation of the macromolecules and, therefore, the mechanical and optical properties of molded pieces. In the case of reinforced parts, it also affects the fiber orientation and distribution. The fountain flow effect is modeled using the Radial Functions Method (RFM). Good agreement between the obtained results and the existing data in the literature was attained. Two cases were considered: power law model in a slit and Newtonian fluid in a vertical pipe.
ON-LINE SENSORING IN EXTRUSION-BASED PROCESSES: PAST, PRESENT AND FUTURE
The challenges materials processing and compounding face nowadays are related not only with the design and control of better and more efficient machines but, essentially, with the manipulation of the molecular structure of the materials, with a view to obtaining innovative high performing products. Extruders are a fundamental part of any extrusion process and intermeshing co-rotating twin-screw extruders, in particular, have special application niches, being the equipment of choice for blending and compounding operations, mainly because of their good distributive and dispersive mixing capabilities. In fact, they are used in most important modern polymer applications such as compounding of filled polymer systems and masterbatches, polymer melt homogenization, polymer modification and the polymer blending. Very often, the last two operations involve, apart from polymer processing, chemical reactions, classical examples of which are the peroxide induced degradation of polypropylene to prepare grades with controlled rheology, and the grafting of maleic anhydride onto polyolefins to improve their compatibility with other polymers. Although these are widespread value-added processes in the polymer industry, there is often a gap in the fundamental knowledge of the properties and physical and chemical composition of the materials being processed during the extrusion process because the extruders are “black boxes” in which the properties of the initial materials, as well as those of the final product, are known, but not the kinetics of the transformation process. This poses severe limitations to current operations because without this knowledge any optimization effort of material structure and/or properties is done by trial- and-error and, thus, is very time consuming and offers no guarantees that the final product is, in fact, optimal. In this work, we present a review of recent developments in on-line sensors that allow for the monitoring of the rheological, chemical and s
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