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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A New Multifunctional Peroxide Initiator for High Molecular Weight, High Productivity, and Long-Chain Branching
The current organic peroxides most commonly used as polymerization initiators are either monofunctional or difunctional. In this work we present the performance characteristics of a new commercial organic peroxide that contains four peroxide groups. Using batch lab-scale, continuous micro-pilot experiments, and simulation we demonstrate several features of the tetrafunctional initiators in styrene polymerization. Principal advantages are 1) increases in molecular weight compared to standard initiators or thermal polymerization, 2) greater than a 20% improvement in production rate with no loss in molecular weight, and 3) the ability to introduce long-chain branching into the resin to improve rheological and processing characteristics.
A New Test Device for Ultra-Low Permeation Rates Measurement
The new and more stringent regulations due in the USA by 2004 call for technical development on both fuel barrier structures and on innovative fuel system designs. They also require enhanced evaluation techniques, especially for assessing ultra-low permeation rates on such high performance systems. The purpose of our development was initially to design a tool able to measure permeability factors on material samples such as films or plates. The in-depth analysis of the technique revealed significant benefits, which makes it a powerful tool to evaluate and select components or sub assemblies of a fuel system as well as large parts such as tank shells.
New Weatherable Film Technology to Eliminate Painting of Automotive Exteriors
Automobile manufacturers are searching for ways to eliminate the traditional painting process employed in assembly plants to decorate and protect the exterior of an automobile. The entire paint facility in a typical assembly plant runs anywhere from $200 million to $600 million and can occupy 50 percent or more of the factory floor. Add to this the cost of environmental compliance, energy, raw materials and labor and it's easy to see why elimination of the paint operation can be a huge benefit to car manufacturers.GE Plastics has developed a polymeric film that can eliminate the need to paint. The film is a proprietary product of polyester carbonates based on resorcinol arylates. This film can be applied over a variety of substrates through an in-mold decoration (IMD) process to yield Class A, exterior panels and trim - that can then be assembled without the need for painting. This product generates an ultraviolet (UV) screener, which extends outdoor life. In addition to the weatherability, the material also exhibits improved scratch and chemical resistance over other thermoplastics.
New Advanced Digital Vibration Welder to Weld Thermoplastic Assemblies
As larger components/applications are being designed from thermoplastics, there is a growing need for welding equipment to accommodate larger parts. Historically, vibrations welders have been used to weld relatively large parts, especially compared with other processes, such as ultrasonic welding. However, recently there have been applications emerging into the market place that are too large for standard vibration welding equipment. In order to accommodate these larger applications, this paper reviews a new digital welding machine that is more powerful, more flexible and designed to weld thermoplastic parts quicker and more efficiently than traditional vibration welders. Two applications, the PC/ABS rear lamp and the PP water reservoir, were examined and it was found that with the use of the digital vibration welding machine, these applications could be welded in less time and with more consistency compared to the analog vibration welding machine.
NMR Spectroscopy and Velocimetry of Polymer Melts under Deformation
In the rheology of complex fluids, the central question concerns the relationship of molecular organisation and dynamics to macroscopic constitutive behaviour. The key to addressing this issue lies in the use of spectroscopic techniques which are capable of accessing information at the molecular level during deformational flow. Examples include optical birefringence and dichroism measurements, neutron and X-ray scattering, and most recently, nuclear magnetic resonance. Through terms in the spin Hamiltonian which are sensitive to order and dynamics, NMR spectroscopy gives us access to the molecules. Through the use of magnetic field gradients, NMR microscopy and velocimetry gives us access to the mechanics. As will be shown, these two approaches are highly complementary. Furthermore, amalgamation of spectroscopic and gradient methods can be used to localise NMR so that we can select any part of the flow field for analysis.We have used 2H NMR quadrupole interaction spectroscopy to measure the deformation of PDMS melts under shear in a Couette cell. The signals were acquired from a per-deuterated benzene probe molecule that provides a motionally-averaged sampling of the entire segmental ensemble. The dependence on shear rate of the SXX (velocity) and SYY (velocity gradient), SZZ (vorticity) and SXY (shear) elements of the segmental alignment tensor has been measured, as well as the angular dependence of the deuterium quadrupole splitting at fixed shear rate. We show that the data agree quite well with the Doi-Edwards theory but significantly better when convected-constraint-release effects are included.
Notched Impact Resistance of Sulfone Polymers: Factors Influencing the Significance of the Izod Test
The notched impact resistance of polysulfone (PSU), polyphenylsulfone (PPSU) and a blend of these two polymers is compared using the Izod test over a range of temperatures (-30 °C to 90 °C) and notch radii (0.08 to 0.76 mm). Izod impact testing, often relied on to characterize the notch sensitivity of resins, suffers from credibility issues due to its single point" nature. The limitation of the test is illustrated by comparing the Izod values for PSU PPSU and the blend over a wide range of conditions. Comparison with other high temperature amorphous resins is also provided. A multiple-radius testing approach is proposed to enhance the usefulness of Izod data."
Novel Acrylic, Weatherable Impact Modifiers with Excellent Low Temperature Impact Performance
A new family of impact modifiers based on a proprietary acrylate has been developed. This class of core/shell impact modifiers achieves lower temperature impact performance than previously attainable with standard acrylic modifiers at conventional use levels in engineering thermoplastics. Moreover, they display excellent weatherability and thermal stability.These unique impact modifiers can be used alone or with other additives to allow the adjustment of melt viscosity and modifier dispersion resulting in optimum processability and impact values in various engineering resin applications.This unique combination of properties expands the utility of conventional core/shell to molded-in-color applications.
A Novel Approach to Modeling Viscoelastic Properties of Thermoplastic Polymer Melts, with Applications to Polylactides
We illustrate the utility of the Havriliak-Negami (HN) functional form as a basis for modeling linear viscoelastic properties of polymer melts, including miscible blends. Parameters obtained by fitting rheometric data with the HN model are physically interpretable and hence comprise useful yet compact and efficient summaries of linear viscoelastic behavior. Such parameter sets can also supplant discrete-line relaxation spectra as inputs for constitutive-equation models that predict non-linear properties from linear-viscoelasticity measurements. Published results for various polylactide (PLA) melts are conveniently schematized using the approach we suggest.
A Novel Couette Viscometer for Polymer Solutions in Supercritical Fluids
The shear viscosity of solutions of polystyrene in supercritical CO2 was examined in the newly developed high-pressure Couette viscometer between 130 and 200°C at CO2 pressures up to 20.6MPa (3,000psi). Our flow curves allow reasonable estimates of the zero shear viscosity as a function of temperature and pressure, otherwise difficult to obtain. In contrast to the conventional capillary instruments, the Couette viscometer prevents gas evolution during the measurement and affords inherently uniform pressure and shear conditions. These features allow a representative thermodynamic and deformation history to be established during the measurement, relevant to subsequent nucleation and structure development during e.g. the formation of microcellular foams.
A Novel Device for Characterization of Profile Flexural Properties
A novel device for characterization of profile flexural properties is presented. The device is called the Vibration Decay Evaluator (VDE). Flexural modulus, profile stiffness, and damping response characteristics of profiles are determined. The characteristics are determined by digital observation of the naturally damped free vibration of a profile. The characteristics are determined from the vibration response through the use of computational algorithms based in structural mechanics and system dynamics theory. The VDE has been validated as an effective tool for rapid evaluation of full profile characteristics to support extrusion operations. A patent is pending on the device.
A Novel Tuning Method for Predictive Control of Melt Temperature and Plastication Screw Speed in Injection Molding
Melt temperature and screw rotational speed are important parameters in the injection molding process since they affect other injection molding processing conditions, cycle time and product quality. It has been shown that in injection molding, predictive control in comparison to the conventional control provides better close loop process dynamics. However, the magnitudes of controller parameters were non-optimal, and were generally chosen after several iterations. A simple and effective tuning strategy was developed for predictive control, and was implemented for controlling melt temperature and screw speed. Better temperature and screw speed responses were obtained when using this new tuning method.
Novel Ultrasonic Process for In-Situ Copolymer Formation and Compatibilization of Immiscible Polymers
The in-situ compatibilization of polymer blends in melt state was found to occur during ultrasonic assisted extrusion without use of any chemicals. Plastic/rubber blends were ultrasonically treated during continuous extrusion at high pressures and temperatures. The tensile strength, elongation at break, Young's modulus, toughness and impact properties of ultrasonically treated blends were significantly improved as compared to the untreated blends. The results of extraction experiments pointed towards copolymer formation during the ultrasonic treatment of the blends at a very short time (in the order of seconds). This in-situ ultrasonic copolymerization at the interface nanolayers enhanced intermolecular interaction, improved adhesion at the interface and stabilized morphology of the blends. The copolymers created at the interface nanolayers are believed to be a major reason for enhancing mechanical properties. This novel process can be applied for preparing plastic/rubber blends to make thermoplastic elastomers or plastic/plastic and rubber/rubber blends, and for making novel copolymers from practically any pairs of existing polymers to achieve desirable chemical and physical properties.
Numerical and Experimental Analysis of the Material Behavior during a Bubble Inflation Test
Recent progress in computer-aided polymer processing analysis demonstrates the need for accurate description of the material behavior under the conjugated effect of applied stress and temperature. Using the bubble inflation experiment and solving for non-linear governing equations of the inflation process, material constants for Mooney-Rivlin and Lodge models are determined. The results for ABS at a typical thermoforming temperature (143C) are presented. Also, the inflation process of thermoplastic polymers was numerically investigated by using the finite element method. A 3 node membrane element based incompressible formulation is analyzed to predict the deformations encountered during the inflation of the membrane. The predicted bubble height at the pole corresponds well to the experimental measurements.
Numerical Simulation of Bulk Polymerization of ?-Caprolacton in Extrusion
Reactive extrusion is an efficient and environment-friendly technique for both continuous polymerizing monomers and chemical modification of polymers. In the present study, the process of bulk polymerization of ?-caprolactone was simulated by Finite Element Method (FEM), with considering different operational factors and reactive conditions. Two unwrapped channel models, 1-D model and 2-D model, are tried in the simulation. Temperature in the cross section of channel were assumed to be equal (to average temperature Tave) in 1-D model whereas temperature were locally different in 2-D model. The calculation shows that the 2-D model gives good results for the reactive process.
Nylon 12-Layered Silicate Nanocomposites
Nylon 12-layered silicate nanocomposites based on synthetic tetrasilisic fluoromica were prepared by melt compounding using a conventional single screw extruder. Wide-angle X-ray diffraction (WAXD), transmission electron microscopy (TEM) and scanning electron microscopy were used for characterization of the morphologies obtained. Predominantly disordered exfoliated morphologies were produced when quaternary alkylammonium modified organoclay was blended with Nylon 12. The mechanical properties of this nanocomposite were enhanced significantly, most noticeably the percentage elongation at break which exceeded 500% compared to 180% for neat Nylon 12, while tensile strength and flexural modulus increased by over 50%. Thermal analysis showed the nanocomposites exhibited glass transition temperatures up to 12 degC higher, and marked reduction in the melt viscosity compared to the pristine Nylon 12.
Observation of the Cavitation Phenomena upon the Gross Melt Fracture Regime in LLDPE Extrusion
We present observation of a cavitation phenomenon in LLDPE extrusion. In the gross melt fracture regime, cavitation was always observed in the first 0.5 ~ 1.5 mm upstream of the exit. We saw cavities at the wall form (seemingly out of nothing) grow to a length and width of about 150 ?m, then shrink down and disappear. From velocity measurements of these structures, we conclude that their width in the radial direction is much smaller than those in the axial and lateral direction and that they are in contact with the wall. The process for the growth and disappearance is approximately 20 ~ 25 ms. The shape of the cavities is highly irregular. From several precise investigations, we concluded that the unstable flow and melt fracture in the entrance region is main source for the cavitation phenomenon, and the cavitation was initiated from the unstable flow by the extensional flow at the die exit.
On Detecting, Characterizing and Counting Defects and Impurities by Color Image Co-Ding Analysis
This paper describes a new, simple and automated procedure for detecting, characterizing and counting otherwise invisible impurities such as black specs and yellow degraded residues in polymer resins and blends, or structural defects such as gels, fisheyes and flow lines in finished products such as calandered film and extruded profile.The method is based on the computer assisted Color Image Coding (CIC) analysis of a sample's digital image acquired from a high resolution flatbed scanner. The analytical results, stored on a relational database management system, are easily archived on customary data media for later retrieval.
On the Prediction of Ejection Force for Tubular Moldings
Guaranteeing the quality of technical parts made by injection molding implies a precise characterization of the processing phase. In the case of parts with deep cores, the ejection step of the molding cycle is often critical. The prediction of the ejection force may contribute to optimizing the mold design and guaranteeing the integrity of the moldings. Data obtained from a fully instrumented mold (pressure, temperature and force) producing a tubular molding are compared with predictions from a simulation algorithm based on a thermo-mechanical model. Semi-crystalline (iPP) and amorphous (PS) materials were used to expand the amplitude of the research.
Online Measurements and Heat Transfer Issues in Blown Film Extrusion
Real time measurements of diameter, velocity, temperature and crystallinity during the blown film extrusion of a linear low-density polyethylene (LLDPE) film are reported. The micro structural variation along the machine direction of the film was observed with online Raman spectroscopy. Based on these measurements, the variation of heat transfer coefficient along the machine direction was calculated from the energy equation governing the process. Experimental values for the coefficient indicate a maximum in the vicinity of the freeze line and match with trends from recent computational fluid dynamics studies  but not with conventional model predictions reported in literature .
On-Line Viscosity Measurements on Fiber Forming Polymers
Intrinsic or relative solution viscosities and melt flow index are widely used in the specification of many polymer resins used in the fiber industry. The solution viscosities provide a measure of the molecular weight of a polymer that is based upon theory, however, the precision of these measurements can be relatively poor. A relationship exists between solution viscosities and the zero shear rate melt viscosity of a polymer, where the latter is four times as sensitive to the molecular weight as the former. This paper discusses the practical application of this relationship using an on-line rheometer to monitor the fiber forming polymers. It will be shown that polymers that are indistinguishable by solution or MFR measurements can be easily differentiated in real time" and in the process from melt viscosities measured by the on-line rheometer."
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