SPE Library
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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Conference Proceedings
A New Hot Runner Nozzle Speeds Color Change and Eliminates Flowlines (Part I)
In this part of our investigation, several manufacturing and design variants of hot runner manifolds were tested to evaluate their effect on hot runner color change performance. It was found that melt channel layout and size optimization are more critical for engineering successful hot runner color change applications than using contoured melt channel turns or plugs, for example. It was also found that the pressure drop and processing window constraints could limit the reduction of melt channel sizes. It was demonstrated that this restriction coupled with the laminar flow of the polymer makes the optimization of some hot runner applications difficult for fast color change. In the second part of this paper a new nozzle design is presented as a solution for such cases.
A New Hot Runner Nozzle Speeds Color Change and Eliminates Flowlines (Part II)
This work investigates the effect of hot runner design features on the color change time. It was found that color change performance is affected mainly by the nozzle tip design. In pinpoint gated hot runners, the flow is converted from circular to annular through one or more tip portals. This flow disturbance generates melt stagnations in the nozzle-well, that hinder color change, and creates weldlines/flowlines that may affect part quality. Likewise, in valve gated hot runners, the flow disruption by the valve stem produces similar drawbacks. In view of that, the extrusion concept of spiral mandrel die was used to develop a hot runner nozzle that improves color dispersion, speeds color change and eliminates flowlines. The new nozzle's performance and the challenges of crossbreeding extrusion and injection molding technologies are reviewed.
New Injection Moldable ESD Thermoplastic Composites Containing Conducting Networks Formed through Structuring in Melt Processing
This paper describes new injection moldable composites having resistivities within a desired static dissipative range 106 - 109 ohms/sq. The new compounds are based on very low carbon black loading (1-2 wt%) sufficient to achieve ESD protection, compared with the 15-25 wt% carbon black based conventional compounds. The phenomenon of filler encapsulation and the selective localization of carbon black particles in multi-component systems are investigated. Quaternary-component systems comprising polypropylene/ nylon/glass fiber/carbon black can be described by a triple-percolation" morphology i.e. three continuities of a continuous glass fiber network continuous nylon phase encapsulating glass fibers and continuous carbon black pathways. The minor polymer affinity to the filler and the attraction of carbon black to the minor polymer are controlling factors in determining the unique blend's morphology."
A New Instrument for Measuring Dynamic Mechanical Properties of Samples Immersed in Fluid
A new dynamic mechanical analyzer with special fluid bath furnace has been developed to measure the mechanical and thermal properties of materials while immersed in fluids or exposed to humidity. This technique is superior to traditional methods of first exposing the material and then performing the measurements.Such experiments are performed on several materials including oil filter paper and an epoxy coating. The former material is immersed in engine oil and shows post-curing behavior. The epoxy is measured in both air and salt water (saline). The saline experiments show that the traditional method (in air) can lead to anomalous results.
New MDO Medium Molecular Weight High Density Polyethylene Films
Machine Direction Orientation (MDO) can enhance many film properties such as tensile strength, elongation, stiffness, optics (haze and gloss) and water vapor transmission rate (WVTR). Few or no medium molecular weight (MMW) HDPE film have previously been offered (or available) due to MDO processing issues, namely stretch resonance, which is a phenomena where the film stretches unevenly. This paper describes a new line of MMW-HDPE MDO films that are now commercially available, made possible through the use of a proprietary processing aid (PA) that overcomes the stretching problem previously encountered with MMW-HDPE resins. Film physical property data for two MDO MMW-HDPE films are presented.
A New Method for Producing Lower Density Ultramicrocellular Foams Using CO2
Our recent work on polymer-gas interactions under subambient conditions revealed a processing window leading to the production of ultramicrocellular foams with cell size around 0.4 ?m. We have now found that even more intriguing cellular structures with lower density can be obtained by re-saturating the ultramicrocellular foam with the blowing agent and subjecting the resulting solid solution to another expansion cycle. PMMA foams with ultrafine cell structure and with densities as low as 0.076 kg/L have been obtained in this work. Morphological characteristics of these foams along with the sorption/desorption kinetics in the system PMMA-CO2 will be reported.
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.
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