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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PERFORMANCE OF A HELIBAR?? EXTRUDER USING A GROOVED BARREL
A new type of single-screw extruder with grooved barrel in the feeding and the melting section, called 'HELIBARR', was successfully introduced in recent years. The grooved feeding section is typically cooled passively by ambient air. The performance of a 35 mm D., 34 L/D HELIBAR was evaluated by running PP, PC and ABS in pellet form, HMW-HDPE in powder form, and HDPE as a blend of pellet and regrind. One barrier-type single-stage screw was used for all resins. The output rates of this extruder were 3-4 times higher than those expected for the same size extruder with smooth barrel, while the specific output rates (output rate per RPM) were more than twice and virtually independent of screw speed or head pressure. Furthermore, this extruder had excellent stability of the output rate and the melt temperature.
DEVELOPMENT OF AN ADAPTIVE PROCESS OPTIMIZATION OF HOT-TOOL WELDING USING AN INNOVATIVE ACTUATION CONCEPT
This paper is a continuation of work presented at ANTEC 2009 . It looks into the initial steps of the development of a self-optimizing hot-tool welding machine. A new machine concept permits the specimen to be pulled in a direction opposite to the joining direction. Using this feature it is possible to assess the strength of the weld directly at the hot plate welding machine. The strength was measured while the material was still in the molten state. In order to use these results for a selfoptimization it was necessary to establish a correlation between the short-time strength of the parts in the cooled state and their short-time strength in the still molten state. Using this concept, the control system of the welding machine can be adapted to find an optimum processing window with just a few test welds. The results show that the optimum of the parameter settings can be defined by measuring the tear forces on the welding machine. Based on these results a self-optimization and quality assurance during the running hot-tool welding process can be developed and tested.
WHY GRADIENT COPOLYMERS MAKE BETTER COMPATIBILIZERS OF IMMISCIBLE POLYMER BLENDS THAN BLOCK COPOLYMERS: DETERMINING CRITICAL MICELLE CONCENTRATIONS OF COPOLYMER IN HOMOPOLYMER
A fluorescence technique is used to determine critical micelle concentrations (CMCs) of styrene-containing block and gradient copolymers dispersed within a homopolymer. Block copolymer composition and molecular weight are varied to determine what factors impact the CMC. Gradient copolymers are shown to have higher CMCs than block copolymers due to the gradient in comonomer composition along the copolymer backbone. Gradient copolymers can be more effective as compatibilizing agents, as they are less likely to be trapped within micelles upon melt processing
IN-MOULD LAMINATION OF METAL SHEETS WITH INTEGRATED FORMING FOR METAL DECORATED PARTS
For high-class applications (e.g. automotive interior) metal decorated plastic parts impress the customers with a metallic look and cool-touch haptics. Producing these parts has been a highly complex process. The in-mould lamination process of metal sheets allows a shortened process chain. In the process the injected melt adheres to a primer system on the metal surface. Furthermore the pressurized melt causes a forming of the metal sheet. This new technology enables a one-step production of metal decorated plastic parts. This paper describes design principles for metal (stainless steel and aluminum) decorated parts first. Then the effects of the injection molding process parameters on the forming quality are shown. An approach to simulate the forming process is presented and evaluated by test results.
THE MORPHOLOGY OF MICRO-INJECTION MOLDED POLYOXYMETHYLENE
A micro-injection molding machine was used to obtain micro-moldings of high density polyethylene, polyoxymethylene, and polycarbonate, in order to study the effects of processing conditions on the microstructural characteristics and mechanical properties. The samples were microtomed and examined using a polarized light microscope for evaluation of morphology. Various microstructural features, such as morphological layer thickness and crystalline polymorphs, were observed and analyzed, in light of the thermo-mechanical history. These features were also correlated with both macro and local mechanical properties.
INTERNAL MIXERS: A NEW APPROACH TO COMPOUND TPE
The generation of process knowledge for the discontinuous compounding of TPE in internal mixers enabling companies of the rubber industries to produce TPE with defined material properties is the aim of the presented project. The properties of TPE strongly depend on its morphology. To adjust the material properties during the mixing in an internal mixer, it is important to understand how the morphology is influenced. Therefore, the melting of the thermoplastic phase and the dynamic vulcanisation of the elastomeric phase are investigated in dependence of the process parameters. The morphology of the TPE is then correlated with the material properties.
SWITCHOVER CONTROL IN THE POLYMER INJECTION FORMING PROCESS
Polymer Injection Forming (PIF) is a new technology to manufacture sheet metal/polymer macro-composite components in a one-operation production process. During the process a metal blank is formed inside an injection mold by means of the pressure of the molten polymer.Changing from velocity control to pressure control just before the mold is filled is a common practice in the traditional injection molding process. In this paper different switchover strategies for the PIF process were investigated. Shot to shot consistency obtained by these methods was evaluated by means of process variations in terms of cavity melt pressure.
EVALUATION OF TITANIUM DIOXIDE PIGMENTS IN A RENEWABLY-RESOURCED POLYMER
A primary attribute of pigmentary titanium dioxide is its ability to ensure opacity while providing a white background in a variety of plastic matrices. The mixing behavior of titanium dioxide at high solids loadings in a renewably resourced polymer was evaluated via compounding processing data and viscosity performance at various temperatures. The study involved the determination of the viscosity behavior of several different surface treated titania pigments when compounded in a polytrimethylene terephthalate resin containing 37% renewably sourced material, by weight, derived from corn.
BENIGN PROCESSING OF HIGH PERFORMANCE POLYMERIC FOAMS OF POLY(ARYLENE ETHER SULFONE)
An environmentally benign process to produce high performance polymeric foams from poly(arylene ether sulfone) was developed. The high performance polymeric foams were produced by utilizing carbon dioxide and water as the physical blowing agents because they are plasticizers for the polymer. By controlling the vitrification of the poly(arylene ether sulfone) through the diffusion of the plasticizers and foaming temperature the cell size and foam density could be readily varied. The foam density varied between 15 to 85% of the unfoamedpolymer and cell sizes ranged between 1 to 200 ?¬m. Theaffect of the cell size and density on tensile properties will be discussed.
STRUCTURE AND PROPERTIES OF ELECTROSPUN PLA SINGLE NANOFIBERS
Electrospinning has been recognized as simple and efficient method to produce micron and nanometer-sized fibers. The technique utilizes electrostatic forces to draw an electrically charged polymer solution jet into fine fiber. To stretch and align the electrospun fibers in one direction, additional mechanical drawing force was provided with the aid of a rotating disc, used as a collector for the deposited fibers. Due to the fine cross sectional area, the solution jet is subjected to high elongational stress and this phenomenon is anticipated to be capable of inducing structural modification within the polymer. In the presented work, poly(L-lactide) (PLLA) with different molecular weight (Mw) were electrospun into nanofibers. Different take-up velocities were applied by a disc collector. The thermal behavior of electrospun PLLA fibers was studied using modulated differential scanning calorimetry (MDSC) and higher ƒ??H was observed for fibers collected with higher Mw and take-up velocity. The molecular orientation was confirmed to be aligned in the fiber direction by 2D wide-angle X-ray diffraction (WAXD) and polarized fourier transform infrared (PFTIR). The degree of molecular orientation increased with increasing take-up velocity. To characterize the mechanical properties, single electrospun PLLA nanofibers were evaluated using a Nanotensile Tester.
MELT RHEOLOGY AND X-RAY ANALYSIS OF GRADIENT COPOLYMERS: SEQUENCE DESIGN FOR PROCESSIBILITY
Gradient copolymers have great versatility in terms ofsequence distribution of monomers along the polymerbackbone for control over their level of nanophaseheterogeneity and flow properties. Using a gradientcomposition rather than a block-type distribution, it ispossible to design longer chains which undergonanophase segregation at lower temperatures yet becomemore homogeneous and melt processible at accessibletemperatures. These behaviors are investigated for a rangeof block and gradient architectures using melt rheologyand small-angle x-ray scattering.
JOIN THE JET SET - DEVELOPMENTS IN THE USE OF UV INK JET FOR INDUSTRIAL DECORATING
As demand for product differentiation and customization increase, UV ink jet has shown the ability to meet even the most challenging design requirements. Not only do UV jet inks allow for the customization of desired parts, but they retain all the traditional UV advantages of rapid cure, solvent elimination, etc. UV ink jet has been used to decorate substrates as diverse as plastic, wood, glass, metal, and ceramics. Formulators are continuously working to improve UV jet inks to operate under many and various challenging conditions. UV jet inks have been able to overcome such challenging requirements as extreme deformation, chemical resistance, and abrasion resistance while maintaining the inherent characteristics that make the products jettable. UV ink jet has proven to be an exceedingly versatile technology that can be applied in a broad range of applications.
THE DYNAMIC BEHAVIOR OF A CONCENTRATED POLYMERIC SUSPENSION CONTAINING NON-BROWNIAN GLASS FIBERS IN SIMPLE SHEAR FLOW
In this paper we study the dynamic behavior of a concentrated short glass fiber suspension subject to simple shear flow. In particular we are interested in determining the relationship between the stress growth functions (shear and first normal stress) and the evolution of the fibersƒ?? orientation distribution within the sample.Stress growth experiments in start up of flow are performed on a Rheometrics Mechanical Spectrometer (RMS-800). Samples at rest are deformed at a constant strain rate for a specified time (i.e. strain) that correlates various points of interest on a stress growth vs. strain plot.The sample temperature is then lowered below the suspension melt temperature ƒ??freezingƒ? the fiber orientation which is then characterized using confocal laser microscopy. The experimental results are compared to predictions based on the generalized Jeffery equation.It is found that the theory over predicts the rate at which the fiber orientation evolves.
THE EFFECTS OF COMONOMER DISTRIBUTION PROFILE ON THE BLOWN FILM PROPERTIES OF SINGLE SITE CATALYZED POLYETHYLENES
To understand better the effects of comonomer distribution profiles on blown film properties, single site catalyzed (SSC) bi-component (narrow MWD homopolymer blended with narrow MWD copolymer) octene polyethylenes were prepared to exhibit both narrow MWD and highly reverse comonomer distribution profiles (final density of 0.917 to 0.930 g/cm3). Their blown film properties were compared with those from PE resins having conventional comonomer distribution profiles including hexene mPE and SSC octene PE. Blown film structure-property relationships are presented, and the excellent toughness results are generally explainable with the tie chain concept. However, exceptions exist for some MD tear strength data.
THERMAL OXIDATIVE STABILITY TESTS A RE-EXAMINATION
DSC and TGA are two of the most widely used methods for studying thermal oxidative stability of polymers. Previous studies have shown that comparable Oxidative Induction Times ( OIT) can be obtained by either method. However since the two methods measure totally different sample properties during the oxidation process we conducted a more detailed study beyond the OIT quantity. Polymers which undergo chain scission and crosslinking are compared with both techniques. A further elaboration of a more general kinetics model was also attempted. Result of these evaluations toward assessing the oxidative stability and possible shelf life prediction will be presented
CONJUGATED POLYMER PHOTOVOLTAIC SOLAR CELLS ' MANUFACTURING, TROUBLESHOOTING AND MORPHOLOGY
Deposition of nanoscale films was used to manufacture organic photovoltaic solar cells. The cells use conjugated polymers as donors and fullerenes as acceptors, which were spin-coated onto a PET-ITO substrate and finished with a sputtered aluminum layer. In order to achieve an actual working cell the measurement of the thickness of nanoscale thin films must be understood completely. The thickness of the coating layers were measured using Atomic Force Microscopy (AFM), UV spectroscopy, an Ellipsometer, White Light Interferometer, Transmission Electron Microscope (TEM), and a high powered microscope with a micrometer with a nanoscale resolution. Cell morphology was studied using atomic force microscopy and UV spectroscopy. The effects of annealing, PEDOT:PSS and LiF insertion, electric fields, solution concentration, and use of carbon nanotubes will be explored in the future.
LOW CTE THERMOPLASTIC AND CROSSLINKED ELASTOMERS
A new process method to prepare and characterize elastomers with lower coefficients of thermal expansions is studied. A styrene butadiene styrene (SBS) thermoplastic elastomer containing physical as well as chemical crosslinks is used to achieve a two-step cured double-network material. Prior to the second-step cure, uniaxial extension step is introduced. Results from conventional monotonic tensile tests, differential scanning calorimeter (DSC) and thermo-mechanical properties are presented. Based on the results it is observed that an interesting material is obtained showing switchable mechanical properties, slightly higher Tg and lower coefficient of thermal expansion.
PLASTICS INDUSTRY BUSINESS STRATEGIES DURING HARD TIMES
The major economic downturn of 2008-2010 has brought great changes in the US manufacturing sector. Not just most major banks, but two automobile manufacturers are now government-controlled with all of the accompanying political baggage and unpredictability. The plastics industry has seen a number of polymer producers shut down US plants with the intention of sourcing in the future from Persian Gulf plants. Is it time for processors to move offshore or is there still business here in the US? Actually, some processors are finding business at home ƒ?? a bit of which has moved back to the US from offshore ƒ?? as well as opportunities for export. Globalization creates business opportunities in the US as well as overseas, for managers canny enough to find them. The global economic shakeout seems to be at least partially levelling the playing field and this paper will review these opportunities.
INVESTIGATION ON THE TEAR PROPERTY OF POLYETHYLENE BLOWN FILMS AT VARIABLE ANGLES
Tear is a key physical property of polyethylene (PE) blown films. There are many variables which affect the overall tear property such as tear path, plastic deformation wake, and so on. In this study, five blown PE films were prepared and tested by the Elmendorf tear test at five sampling angles, i.e. 0 (MD), 30, 45, 60, 90 (CD) degrees.Tear values were analyzed statistically and the variation of the tear data was investigated based on the observation of the tear samples. The mechanism of severely curved crack, i.e. J-tear, was also studied to understand the tear property variation of blown PE films.
MANUFACTURING AND CHARACTERIZATION OF NANO-COMPOSITE LINEAR STRAIN SENSORS
This study explores the potential of using polymer nanocomposites for a strain sensor application. This work focuses on the development of such strain sensors made by casting vapor-grown carbon fiber (VGCF) reinforced polydimethylsiloxane (PDMS). The tensile properties are determined as a function of the VGCF content. Furthermore, the percolation threshold is determined; and the electrical conductivity of nanocomposites with VGCF content above the percolation threshold is measured. Finally, the relationship between electrical conductivity and mechanical strain is determined for loading/unloading cycles to verify the durability and repeatability of the sensors.
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