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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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.
CORRELATION OF FILM CASTING BEHAVIOR WITH NON-LINEAR RHEOLOGY FOR A SERIES OF HDPE’S WITH DIFFERENT DEGREES OF SPARSE LONG CHAIN BRANCHING
The degree of film-width reduction or necking during film-casting is analyzed for several metallocene-catalyzed high density polyethylenes HDPE with varying degrees of sparse long-chain branching LCB. It is found that the addition of sparse LCB reduces the degree of necking to a greater degree than broadening the MWD. Analysis of the uniaxial extensional and dynamic shear rheology with the pom-pom constitutive model reveals that a distribution of branches along shorter relaxation time modes is important in reducing necking at higher drawdown ratios.
CORRELATION OF FILM CASTING BEHAVIOR WITH NON-LINEAR RHEOLOGY FOR A SERIES OF HDPE'S WITH DIFFERENT DEGREES OF SPARSE LONG CHAIN BRANCHING
The degree of film-width reduction or necking during film-casting is analyzed for several metallocene-catalyzed high density polyethylenes, HDPE, with varying degrees of sparse long-chain branching, LCB. It is found that the addition of sparse LCB reduces the degree of necking to a greater degree than broadening the MWD. Analysis of the uniaxial extensional and dynamic shear rheology with the pom-pom constitutive model reveals that a distribution of branches along shorter relaxation time modes is important in reducing necking at higher drawdown ratios.
MODELING INTERFACIAL STRENGTH OF POLYBUTYLENE SUCCINATE(PBS)/POLYPROPYLENE(PP) MULTILAYER INJECTION-MOLDED PART USING FINITE ELEMENT METHODS
Polypropylene (PP)-based sandwich injection moldings containing biodegradable polymers in the core were carried out. Interfacial adhesion between the skin and the core is essential for obtaining sufficient mechanical strength for commercial applications. In order to investigate the interfacial strength between the skin and the core, the ASTM/ISO scratch test was used and critical delamination load for delamination was determined. For comparison, an 180o peel test was also conducted, whereby the skin was peeled off from the core, to measure its adhesive force in a different way. Numerical simulation using FEM was applied to these experiments to study interfacial strength. Destruction of the interfacial layer was defined by either a critical stress or critical strain criterion. The critical strain criterion appears to better describe the phenomenon in these two experiments. FEM simulation could qualitatively correlate with these behaviors, suggesting that delamination could be described as a strain dominant phenomenon.
A NEW INTERPRETATION TO THE TALC-ENHANCED POLYMERIC FOAMING PROCESS
Cell nucleating agents are commonly used in polymeric foaming processes to enhance cell nucleation. It has been widely believed that the enhancement was through the promotion of heterogeneous nucleation. Even though it has been observed by other researchers that additional bubbles were nucleated near the growing cells despite the low gas concentration the mechanisms have not yet been clearly identified. It seems that with the presence of talc particles the shear and/or extensional fields generated by the growing cells that are near them have a stronger effect on bubble nucleation than the depleted gas concentration. Using the concept of the critical radius for bubble nucleation and the stress fields generated around the talc particles this paper presents a mechanism of cell nucleation for this case.
A NEW INTERPRETATION TO THE TALC-ENHANCED POLYMERIC FOAMING PROCESS
Cell nucleating agents are commonly used in polymeric foaming processes to enhance cell nucleation.It has been widely believed that the enhancement was through the promotion of heterogeneous nucleation. Even though it has been observed by other researchers that additional bubbles were nucleated near the growing cells despite the low gas concentration, the mechanisms have not yet been clearly identified. It seems that, with the presence of talc particles, the shear and/or extensional fields generated by the growing cells that are near them have a stronger effect on bubble nucleation than the depleted gas concentration. Using the concept of the critical radius for bubble nucleation and the stress fields generated around the talc particles, this paper presents a mechanism of cell nucleation for this case
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