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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FABRICATION OF MICRO-DIES FOR EXTRUSION OF POLYMER MELTS
The ongoing trend for miniaturization demands research in the field of micro-extrusion. This work compares two techniques for manufacturing micro-dies; mechanical manufacturing and laser ablation. A micro-die needs to fulfill requirements such as fast nozzle exchange and high accuracy. The nozzle channel needs to have a diameter of less than 0.5 mm, a high quality and high aspect ratio. The disadvantages and advantages of both techniques are discussed while experimental data supports the discussion. The results go well with the expected behavior based on the nozzle channels geometry. Laser ablation is the tool of choice when manufacturing micro-dies for extrusion.
SEAL LAYER MATERIALS CHARACTERIZATION IN TERMS OF CRYSTALLINITY AND RHEOLOGY
A series of commercial seal layer grades ethylene vinyl acetate (EVA) resins were investigated in terms of thermal and rheological properties. The effect of vinyl acetate (VA) content in Differential scanning calorimetry (DSC) experiments revealed that the increase of VA content leads to decrease in melting point and heat of fusion. In oscillatory shear measurements the effect of long-chain branching on high shear sensitivity and long relaxation time of resins was revealed. In addition, a significant strain hardening behavior in extensional viscosity measurements was observed which indicated high melt strength of these resins.
CRITICAL ASSESSMENT OF SCRATCH VISIBILITY DETERMINATION METHODOLOGIES
The major objective of this work is to critically assess the similarity and differences between the two industrial scratch visibility determination methodologies: Erichsen and ASTM/ISO scratch tests. The assessment relies on the two evaluation methodologies: L for Erichsen and contrast for ASTM/ISO. A good correlation between the two methods can only be established if a contrast criterion is also utilized for the Erichsen test. The surface deformation that gives rise to light scattering such as the scratch profile and the surface roughness on the scratch path were studied for both methods and their implication on scratch visibility will be discussed.
ACCELERATED ENVIRONMENTAL AGEING OF MATERIALS USED FOR COLLAPSIBLE FUEL STORAGE TANKS
The purpose of this work was to perform a comparative analysis of various candidate nitrile coated fabric materials supplied by potential vendors to be used as fuel storage tanks and compare the results to the currently fielded polyurethane storage tanks. Our strategy is to utilize advanced environmental ageing methods to simulate extended weathering conditions. Our results demonstrate that the nitrile coated fabrics performed well in our evaluation. Their breaking strengths are about equal to the currently fielded urethanes and they performed comparably when subjected to environmental ageing conditions.
HIGH TEMPERATURE MECHANICAL PROPERTIES OF PEROXIDE CROSS-LINKED ETHYLENE-OCTENE COPOLYMER
Ethylene-octene copolymer (EOC) was cross-linked by dicumyl peroxide (DCP). Thermoplastic vulcanizate (TPV) based on polypropylene (PP)/EOC-DCP was prepared by dynamic vulcanization. Gel content was noted. Tensile creep properties of these samples at elevated temperatures (70- 200?øC) were studied. Residual strain after 100% and 200% elongation were examined. EOC cross-linked with lower peroxide levels underwent creep failure easily at lower temperatures even with small loads. EOC with 0.6 wt. % of DCP was found to be the strongest even at higher temperatures and lower temperatures with heavier loads.
A STUDY ON INJECTION-STRUCTURE COUPLED ANALYSIS FOR THE PREDICTION OF INTEGRATED METAL INSERT INJECTION MOLDING PARTS
This study proposes an injection-structure coupled analysis to quickly predict the deformation of the insert parts of small precise connectors. The flow pattern was determined through an analysis of the plastic injection molding of small precise connectors, and a structural analysis was performed using injection pressure. For this purpose, an injection-structure mapping program was developed to use the injection molding pressure as the input to the boundary condition of the structural analysis. The effect of injection molding, which varies according to the process conditions of the metal insert parts of small connectors, was analyzed through structural analysis.
COMPARISON OF SERVO AND PNEUMATIC ULTRASONIC WELDING OF HDPE SHEAR JOINTS
Pneumatic and servo-driven ultrasonic welding of HDPE shear joints were studied. For pneumatic ultrasonic welding, the effects of weld force, down speed, and amplitude of vibration on weld strength were studied. For servo-driven ultrasonic welding, the effects of velocity, velocity profiling and collapse distance during hold on weld strength were studied. Our goal was not to optimize the welding conditions but rather compare the operation of the two systems. Both systems worked well and produced consistent welds. More work is needed with both systems to better understand the ramification of some of the controllable parameters.
RESIDUAL STRESS EVALUATION OF EASTMAN TRITANƒ?› COPOLYESTER, POLYCARBONATE AND THEIR BLENDS WITH ABS
This study evaluates the residual stress levels in objects molded with Eastman's Tritan copolyesters and Edgetek XT (Tritan blends with ABS) compared to molding grades of Polycarbonate and PC/ABS. A layer removal technique and chemical solvent testing are employed for stress evaluation. Both methods show that molded-in stress levels of Tritan based materials are generally 0.2-0.5X lower than levels measured in PC-based products. Additionally, testing shows that ABS has little impact on the stress levels of either Tritan or PC. These results strongly reveal why Tritan containing products exhibit excellent chemical resistance performance in a variety of market applications.
EFFECT OF CRYSTALLIZATION AT FILM INTERFACE IN HEAT SEALING PROCESS
Heat sealing is a general technique used for joining polymer film. The mechanism was not clarified. Heat seal temperature at sealed film interface is an important factor to control heat seal properties. In this study temperature profile at sealed film interface in-situ heat seal process was precisely measured by a fine thermocouple. Molecular structure development at film interface was investigated by WAXD and DSC. In heating and cooling process temperature profiles were obtained. The heating and cooling rate depended on crystallization behavior in heat sealing process. We concluded that crystallization is a major factor to affect heat seal properties.
MANUFACTURING OF AGAROSE-BASED CHROMATOGRAPHIC ADSORBENTS WITH CONTROLLED PORE AND PARTICLE SIZES
The effect of ionic strength and quenching temperature on the mechanical properties and structure of agarose-based chromatographic adsorbents in micro-beads for bioseparation was investigated. The pore size/size distribution of the beads was measured by analysis of their AFM images. Their mechanical properties were determined by a micromanipulation technique based on compression of single micro-particles. It was found that the mean pore size and stiffness of agarose beads increase with ionic strength and slow cooling. These two parameters do not affect the particle size/size distribution.
THE PREDICTION OF INJECTION MOULDED PRODUCT MASS THROUGH PROCESS SIGNALS
The injection moulding process has a complicated set of process parameters and is subject to variations over time resulting from material, environmental and machine component changes. In order to maintain product quality it has been proven that monitoring the process signals is beneficial towards identifying possible changes in the moulded product. Here, the process signals (melt pressure, temperature and screw displacement) are utilised along with material pressure-specific volume-temperature (pvT) characteristics to estimate the moulded product mass. The successful validation of this method presented over a range of processing conditions.
THE EFFECT OF NANOTUBE FEEDING POSITION IN TWIN-SCREW EXTRUSION OF PP BASED NANOCOMPOSITES
The influence of feeding conditions of multiwalled carbon nanotubes (MWNT), namely Baytubes C150P and Nanocyl ›NC7000, into polypropylene (PP) was investigated with respect to achieve high electrical conductivity and suitable nanotube dispersion. Both MWNT types were fed at selected concentrations either in the hopper of the twin-screw extruder or using a side feeder under otherwise same conditions (rotation speed, throughput, temperature profile). The electrical resistivity was measured on pressed plates and injection moulded samples and the state of the filler dispersion was studied using transmission light microscopy (LM). Mechanical properties, like tensile and impact strength were characterised on injection moulded samples.
EFFECTS OF GAS AND D-LACTIC ACID CONTENTS ON THE STRUCTURE AND PROPERTIES OF MICROCELLULAR INJECTION MOLDED POLY (LACTIC ACID)
This paper investigated the effect of gas content on the tensile properties and microstructure of two grades of poly (lactic acid) (PLA) that differ in terms of D-lactic acid (D-LA) content. SCF Nitrogen (N2) was used as the physical blowing agent for molding microcellular PLA tensile bars. The properties of microcellular PLA were found to be dependent upon the D-LA content. Under the most favorable conditions, high cell density and small cell size was obtained. A high cell nucleation rate and a high degree of crystallinity with different levels of D-LA enhanced microcellular structure formation at higher levels of N2.
SIMULATION OF EPP BEAD MANUFACTURING IN BATCH FOAMING PROCESS THROUGH HIGH PRESSURE DIFFERENTIAL SCANNING CALORIMETER (HPDSC)
To simulate the evolution of the melting behavior of polypropylene (PP) during the manufacturing of expanded PP bead foams (EPP) through batch process, a high pressure differential scanning calorimeter (HP-DSC) machine was used. The EPP bead foam has two original melting peaks which are suitable for bead foams during the steam chest molding process to produce final products with well sintered beads and good firmness. The influence of various saturation temperatures, time, and pressure on the double crystal melting peak creation is investigated in this work. The results can bring an overestimation of the optimized parameters for the batch process.
EFFECTS OF PROCESS PARAMETERS ON ADDITIVE ASSISTED LASER SINTERING OF POLYETHERETHERKETONE
New approaches have been done to develop the selective laser sintering process and materials. Within this process a layer to layer fusion plays an important role to achieve good bonding and part properties. This paper deals with the additive assisted laser sintering of polymers, which allows an adjustable sintering depth and independency from the optical absorption behavior of the polymer. Within this study an approach is presented to correlate the observed sintering behavior of polyetheretherketone with process and material parameters. A statistical model has been used to describe a correlation and identify the important parameters and effects within the process.
POLYPHENYLENE ETHER MACROMONOMER: X. VINYL TERMINATED TELECHELIC MACROMERS
Unique low molecular weight polyphenylene ether telechelic copolymers (PPE-M) were designed for use in thermosetting resins. Indeed, PPE macromonomers have been heralded as a breakthrough in the search for materials that broadly enhanced performance of thermoset materials. For example, the phenolic terminated macromer gave broad enhancements of performance with epoxy resins and cyanate esters. Another important class of thermoset resins involves vinyl or unsaturated monomers. Therefore, various vinyl-terminated PPE macromonomers were prepared and their performance was quantified in vinyl-based thermoset resins. The vinyl groups were allyl, methacryl, allyl hydroxyl propyl, and vinyl benzyl.
INFLUENCE OF THE TOOL MATERIAL ON THE MICROSTRUCTURE AND MECHANICAL PROPERTIES OF PMMA LAP JOINTS WELDED BY FRICTION SPOT
The development of new polymer welding techniques is currently a key subject in the field of science and technology of joining. Industrial sectors such as the automotive, airspace and civil engineering are examples where polymer welding is largely applied. Recently, the feasibility of the friction spot welding process was demonstrated on thermoplastics. The objective of this work was to evaluate the influence of tool material on the properties of polymeric friction spot welds on poly (methyl-methacrilate). Microstructure, lap shear resistance and fracture mechanisms of single lap joints produced with stainless steel and titanium tool materials were investigated for this purpose.
GLASS FIBRE-REINFORCED POLYETHYLENE COMPOSITES IN ROTATIONAL MOULDING
Fibre-reinforced mouldings are of growing interest to the rotomoulding industry through their outstanding price/performance ratio. However, a particular problem that arises when using reinforcements in this process is low shear, good mixing of resin/reinforcement is not optimum under those conditions. There is also a problem of the larger/heavier reinforcements segregating out of the powder to lay-up on the inner part surface. In this paper we report on studies to incorporate glass-fibres into rotomoulded parts. Results indicate that pre-compounding is necessary to gain performance enhancement and the single-layer part made from glass-reinforced, pre-compounded powder exhibited the highest tensile and flexural modulus.
EXPERIMENTAL STUDY OF THE EFFECT OF MOLDING AND COATING ON THE DURABILITY OF OPTICAL POLYCARBONATE PRODUCTS
Polycarbonate (PC) has become widespread in public transportation vehicles, lenses, as well as glazing due to its light weight, outstanding unique engineering properties, and extreme levels of toughness and ductility. PC is usually injection molded, or sometimes extruded and thermoformed, into desired 2D/3D complex shape, then applied with hardcoats to improve its weathering and abrasion resistance performance. The effect of molded-in stress on the brittleness and microcracking of silicone-based hardcoats during the coating process was quantified, and the impact resistance performance of weathered and aged polycarbonate samples was studied with different coating system.
TENSILE BEHAVIOR OF SYMMETRIC AND ASYMMETRIC STRUCTURAL COMPOSITE FOAMS
Structural composite foams were produced by enclosing a foamed core between two composite skins. The effect of layer thickness and composition was studied using different amounts of chemical blowing agent (1 and 1.5%) and flax fibres (0, 15, 30%). The samples were produced by compression molding and characterized in tension. Videos were also taken. The results show that for symmetric structures, both skins break simultaneously, whereas asymmetric foams present two consecutive skin breaks. As expected, increasing CBA content decreased all the properties, while increasing fibre content led to higher Young's modulus and lower strain at break.
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