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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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
EFFECTS OF HYDROLYTIC DEGRADATION ON THE MECHANICAL PROPERTIES OF RENEWABLE BIOPLASTICS: POLY(TRIMETHYLENE MALONATE) AND POLY(TRIMETHYLENE ITACONATE)
Hydrolytic degradation of two renewable copolymers, poly(trimethylene malonate) (PTM) and poly(trimethylene itaconate) (PTI), was performed in aqueous solutions adjusted to pH values ranging approximately from 5.5 to 11. The influence of the degradation on the elastic modulus of these bioplastics was examined by a new atomic force microscopy (AFM) mode. Elastic modulus was monitored as a function of degradation time (100 to 10000 min) in DI water to determine changes. After degradation for one week the elastic modulus of PTI has decreased by 71 %. PTM was found to be hygroscopic. Due to significant swelling and uneven surfaces—in both the dry and wet state—PTM samples could neither be easily imaged nor its nanomechanical properties evaluated by AFM.
LIFETIME PREDICTION OF PLASTIC PARTS – A CASE STUDY
Lifetime prediction of plastics is a very difficult proposition, but one that is becoming increasingly important as plastics are used in more demanding and critical applications. The lifetime of a plastic part is influenced greatly by many factors including the type of plastic, stress level, temperature, type of loading, and environmental conditions. All these factors make absolute lifetime prediction a nearly impossible task. However, by understanding how these factors influence plastics over time, one can begin to make educated predictions with some level of accuracy. This paper will discuss techniques that can be used to predict the lifetime of a part. A case study is given on how lifetime prediction was used to understand and ultimately solve the cracking of an industrial fan made of glass reinforced polypropylene
ONE- AND THREE- DIMENSIONAL ALIGNMENT OF GRAPHENE USING NEW FABRICATION STRATEGIES FOR THERMALLY CONDUCTIVE LLDPE-GRAPHENE COMPOSITE
Thermoplastic foams characteristically are good thermal insulators. In contrast, this paper compares two new fabrication techniques to align Graphene NanoPlatelets (GNPs) in Linear Low Density PolyEthylene (LLDPE). These new composites with aligned graphene due to foams possess effective thermal conductivity (keƒƒ) that was up to 13-fold over that of neat LLDPE. SEM micrographs revealed 1-D and 3-D alignment of GNPs by dry-blending and compounding fabrication methods.
A METHOD FOR THE EVALUATION OF RESPIRATORS IN A NANORICH ENVIRONMENT
Nanostructures have been a topic of great scientific interest for the past several decades for the possibility of their use in enhanced composites. However, the precautions for the safe use of these low bulk density materials are commonly overlooked. The airborne release of these materials, such as carbon nanotubes (CNTs), carbon nanofibers (CNFs) and nanoclays, into the air during compounding is inevitable. In conventional polymer processing these fillers pose a potential threat until they are encapsulated in a polymer matrix. This occurs while transporting or feeding nanostructures into the process. Typically, the operator uses a respirator to avoid inhaling nanostructures into the body that escape engineering controls and it is therefore important to investigate how efficient these respirators are at capturing these airborne materials. To carry out this study, a special device was built to simulate the dynamic breathing process of air inhalation to determine the permeation of nanostructures through various respirators of different safety ratings. This will provide new information concerning the environmental impact of nanostructures in the prevention of exposure to human beings of airborne nanostructures.
TROUBLESHOOTING THE CO ROTATING TWIN SCREW EXTRUDER
Twin screw extrusion technology originated in the early 20th century and it revolutionized material compounding. The technology is used in the polymer, chemical, food, and recently in the pharmaceutical industries. Considering the numerous materials twin screw extrusion can operate with, it is evident that each process behaves uniquely. The problems that occur during these unique processes can be solved or prevented using similar guidelines and strategies. The following paper provides a strategy on successfully troubleshooting the co-rotating twin screw extruder and it offers possible solutions to several problematic scenarios that frequently are experienced.
IMPROVING SURFACE QUALITITY OF FOAMED POLYCARBONATE (PC) PARTS USING WATER AS THE PHYSICAL BLOWING AGENT
This paper presents a new process for producing microcellular injection molded plastic parts using water as the physical blowing agent and micro-scaled particles as the cell nucleating agents. Distilled water with dissolved salt were fed through the hopper of an injection molding machine and mixed with polycarbonate (PC) in the machine barrel. Dog-bone bars were molded with different shot volumes, water/salt solution feed rates, and salt concentrations. The resulting surface roughness and microstructure were compared with conventional solid and microcellular injection molded parts.
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