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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Dynamic Cooling Design for Injection Molding
The current system of injecting hot polymer into a comparatively cold mold results in the development of a solidified layer and reduction in part quality. As a consequence of this process limitation, molding systems continue to produce inferior components during production. This paper develops an innovative mold design and preheating process to dynamically control the temperature at the mold-polymer interface during the molding cycle. Simulation indicates that a preheat system can significantly reduce residual stress compared to conventional molding given equivalent cycle times.
Acoustic Telemetry in Injection Molding
The characterization of acoustic noise present in an injection mold during operation is presented for a remote in-cavity pressure sensor. This analysis is necessary to evaluate the use of ultrasound to carry process information out of the mold cavity. Experimental results are presented consisting of amplitude and frequency analysis of acoustic noise present in an injection mold as well as first attempts at transmission and demodulation of acoustic data.
Model Predictive Control of Injection Molding
A predictive model based controller is used for dynamically controlling the mold wall temperature in injection molding. The reference model is a physics based model developed using one-dimensional heat transfer analysis. The process involves preheating the inner mold surface and then rapidly cooling it to achieve faster cycle times and better part quality. The controller attempts to track a desired reference surface temperature profile by regulating the preheat time, preheat temperature, and coolant temperature. The state variables are monitored online and control set points are generated using the model as reference.
Experimental Validation of a Simulation Software for a Flat Specimen Injection Mold
The objective of this work was to compare simulation and experimental results for a flat specimen injection mold. The study was made using standard and film" gates. The results were obtained through a simulation program for the injection process C-MOLD for theoretical data and for the experimental data results were obtained in an injection molding machine. In both cases the injection molding conditions were the same. Differences between the gates and also between experimental and theoretical results mainly in the injection pressure and pattern flow were found."
Injection Nozzle Ultrasound Measurements
Ultrasonic measurements are a rich source of information during polymer processing. Difficulties in applying sensors to injection moulding nozzles have been overcome, and ultrasonic velocity measurements are being used to indicate process dynamics in terms of temperature and pressure change during injection. This work describes employment of a novel nozzle in which an ultrasonic signal is propagated along a path angled to the direction of melt flow, such that flow rate effects contribute to the received signal.
Creep Crack Growth in Oriented Polypropylene
Creep (slow) crack growth resistance in oriented polypropylene (PP) is investigated using a fracture mechanics approach. The equal channel angular extrusion (ECAE) process is used to induce structural anisotropy. A constant load single edge notched bend (SENB) test is performed at an elevated temperature on isotropic (unprocessed) and anisotropic (processed) PP. This test generates stress intensity (K) vs. crack growth rate (da/dt) relationships. The da/dt = Kn relationship reveals that the creep crack growth resistance and mechanical properties of PP can be greatly improved by ECAE.
Plastics Education in the Delft University Industrial Design Engineering Curriculm
Industrial Design Engineering graduates from Delft University have a background in a wide range of subjects, including plastics. They have been prepared for industrial product development practice by design exercises throughout the curriculum. In these exercises the students apply various subjects, including design of plastics components. The students' general technical and plastics background is expected to improve by curriculum adjustments currently being prepared. Product Design graduates have received additional training in designing with plastics.
Measurement of Entrance Pressure Drop of Polystyrene/Supercritical CO2 Solutions
Two slit dies with sudden contraction ratios of 4:1 and 18:1 were designed to investigate the effects of pressure and supercritical carbon dioxide (scCO2) content on the entrance pressure drop and rheological properties of PS/CO2 solutions. scCO2 was found to decrease the entrance pressure drop as well as the shear and extensional viscosities of PS.
Compatibilizing EPDM and Degraded PP through Hydrosilylation Reaction
A hydride-terminated PDMS was used as a coupling agent for EPDM and degraded PP (previously generated all the way in melt phase by peroxide initiated degradation) through a hydrosilylation reaction in the melt-phase. Different concentrations of PP with different degrees of degradation were used, and different amounts of catalysts were employed. Melt viscosity, blend morphology and gel were evaluated. The reaction was found to increase viscosity and to improve blend morphology.
Process Optimization in Microcellular Foam Extrusion
In this paper, the effects of operating conditions in a polystyrene microcellular foaming process, such as CO2 content, die pressure and die temperature, are explored. Experiments were performed on a two-stage single screw extruder. Below the solubility limit, the higher the CO2 concentration, the smaller the cell size and the greater the cell density. With an increase of die pressure, the cell size decreases and the cell density increases. The experimental results indicate die temperature plays a strong role in determining the cell size, cell density and cell structure.
On the Correlations between Thermodynamic and Dynamic Fragility of Polymers
The correlation between the thermodynamic measure of fragility Cpl/Cpg(or Cpl/Cpc) and the dynamic fragility index m (1) , are presented for small molecule organic, polymeric and inorganic glass forming liquids. The results are consistent with three classes of behavior: 1) a decrease in m with increasing Cpl/Cpg for the polymeric glass formers; 2) a nearly constant value of m independent of Cpl/Cpc for small molecule organics and hydrogen bonding small molecules; 3) an increasing value of m with increasing Cpl/Cpc for inorganic glass formers as originally considered by Angell. (1)
Simulation and Analyses of the Polymer-Pellet-Flow into the First Section of a Single Screw
The flow of plastics pellets into the first flights of the screw is frequently neglected when analyzing the solids conveying process in single-screw extruders. In order to gain better insight into the complex correlations that exist between pellet properties, barrel and screw geometry, the inflow process is simulated and investigated in experimental terms. Based on these findings a simple physico-mathematical model is worked out. The aim is to develop an optimum filling geometry in respect of feed behavior and solids conveyance.
Scratch Behavior in Molecularly Oriented Polycarbonate
In this paper the scratch behavior of molecularly oriented polycarbonate (PC) is investigated. Controlled molecular orientation is achieved through the equal channel angular extrusion (ECAE) process. Ford five-finger scratch test is used to investigate the orientation effect on the scratch resistance (in terms of scratch depth) in the ECAE-oriented PC. This study shows that controlled molecular orientation can improve the scratch resistance in polymers.
Investigation of the Volume Recovery of Glass-Forming Polymers
Up to now, the time dependent behavior of glass-forming polymers has been modeled with only moderate success. This could be explained by the fact that the relaxation times depend on the time-temperature- pressure history of the material rather than on the instantaneous state as is generally assumed. We have developed new volume recovery experiments to examine this assumption. The impact of our results on the current theoretical models will be discussed.
Full 3-D Prediction of Warpage of Injection Molded Parts
A full 3-D CAE system has been developed to predict warpage of thermoplastic injection molded parts. The system consists of pre/post processors and full 3-D solvers of mold cooling, polymer filling, packing and warpage. The validity of the warpage prediction was verified by using a box-shaped part and a L-shaped one. Although they were thin-walled parts, it was confirmed that the full 3-D simulation was necessary for the accurate prediction of their warpage.
Flow Visualization of Polymer Processing Additives Effects
Flow visualization was used to understand how polymer-processing additives (PPA) eliminate sharkskin in linear low-density polyethylene (LLDPE). A sapphire capillary die was used to image the coating of the PPA onto the die wall. Depth resolved optical microscopy was used to measure the velocity profiles. When added, the PPA migrates to and coats the die wall, induces slippage, and eliminates sharkskin. The interface between the PPA and LLDPE is characterized by long stripes in the flow direction.
Structure-Property Relationships in HMW-HDPE Blown Films
The influence of processing conditions on the performance of HMW-HDPE blown films was investigated in relation to their molecular orientation characteristics. The presence of two distinct populations of lamellar stacks in such HMW-HDPE blown films and their influence on the physical properties was also considered. Finally, the dart impact strength of certain HMW-HDPE blown films was observed to increase with increasing draw-down ratios (decreasing film thickness); the morphological features that drive this unique structure-property relationship was explored as well.
Process Monitoring at the National Institute of Standards and Technology: Celebrating 100 Years of Measurement Excellence
Two events that coincide in the year 2001 are the NIST centennial year anniversary and the inauguration of the SPE Special Interest Group on Process Monitoring and Control. To celebrate these two events, this paper will highlight polymer process monitoring activities at NIST describing the full range of measurement and sensor developments for real-time monitoring of resin temperature, rheology, morphology, molecular orientation, and dielectric properties of polymers, filled polymers and polymer blends.
Forward to Better Understanding of Optical Characterization and Development of Colored Polyamides for the Infra-Red/Laser Welding: Part I-Efficiency of Polyamides for Infra-Red Welding
The influence of a wide range of the infrared (IR) wavelengths (from 830 to 1,064 nm) on the optical properties of welded thermoplastics was evaluated for unfilled, filled and reinforced polyamide 6, 66 and amorphous grades. Presented results and developed recommendations will help, designers, technologists and materials scientists in welded parts design, materials selection and new materials development for various laser welding (LW) applications.
Ethylene Styrene Interpolymers for Injection Molded Toys
Due to increasing regulatory pressure, the toy industry has found itself being challenged to find suitable replacements for flexible PVC in flexible injection molded toys. Plasticized PVC is typically used for flexible toys where design requires painting of the molded toy. A new family of compounds suitable for such toy applications has been developed. These compounds are based on ethylene styrene interpolymers and exhibit short cycle time, high tensile strength, and excellent paintability.
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