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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.
Paul T. Callaghan, Ryan J. Cormier, Maria L. Kilfoil, May 2002
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.
M. Jamal El-Hibri, Edward M. Buckwald, William W. Looney, May 2002
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."
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.
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.
Jang-Hoon Oh, J. Thomas Lindt, Mette H. Ottøy, May 2002
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 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.
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.
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.
F. Erchiqui, A. Derdouri, A. Garcia-Réjon, May 2002
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.
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.
C.Y. Lew, W.R. Murphy, T. McNally, G.M. McNally, May 2002
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.
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.
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.
A.J. Pontes, R. Pantani, G. Titomanlio, A.S. Pouzada, May 2002
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.
S. Cherukupalli, R. Paradkar, A.A. Ogale, A.J. McHugh, L. Henrichsen, May 2002
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 .
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."
Taras Vasilkeyvsky, Ihor D. Skrypnyk, Jan L. Spoormaker, May 2002
The load carrying capacity of plastic boxes diminishes with time, due to the visco-elastic behaviour of plastics. Structural optimisation of boxes is possible by applying Multipoint Approximation Response Surfaces (MARS) in combination with Finite Element Method pro-grams like MSC/MARC. The MARC program has an open structure and the non-linear viscoelastic constitutive relationships can be accounted for, using the user subroutine HYPELA.Results from structural optimisation calculations will be presented, with the mass as the objective function and the load carrying capacity determined by buckling as the major constraint.Results from experimental verification of buckling loads will be given as well.
J.M. Nóbrega, O.S. Carneiro, F.T. Pinho, P.J. Oliveira, May 2002
The current state of a computational code that is being developed to aid the design of extrusion dies for thermoplastic profiles is presented. This code encompasses three main parts: i) flow modelling routines based in the finite volume method, to calculate the 3D flow field using non-isothermal models; ii) geometry and mesh generators; ii) optimisation algorithm based on the non-linear simplex method.Currently the code solves the flow balancing problem using simultaneously different strategies: length and thickness control of the die flow channel. Its application is illustrated using one case study.
Recently, Husky sought to investigate further optimization of the performance of their Thermal Sprue TS 750 series. A test rig for evaluating the sprue performance was constructed for that purpose. The temperature distribution was measured along the nozzle tip to track the thermal profile of the sprue with various settings and design parameters. The comparison between measurements on the test rig and on a mold validated the simulated thermal environment created in the test rig. While this approach proved to be useful, there is still a need for trial and error procedures because each set of parameters has to be adjusted to obtain the corresponding thermal profile of the sprue. Furthermore, no prediction of the thermal profile could be done using only the processing conditions or changes in the sprue geometry.
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Any article that is cited in another manuscript or other work is required to use the correct reference style. Below is an example of the reference style for SPE articles:
Brown, H. L. and Jones, D. H. 2016, May.
"Insert title of paper here in quotes,"
ANTEC 2016 - Indianapolis, Indiana, USA May 23-25, 2016. [On-line].
Society of Plastics Engineers
Note: if there are more than three authors you may use the first author's name and et al. EG Brown, H. L. et al.