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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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.
The Effect of Three-Lobe, Off-Set Kneading Blocks on the Dispersion of Calcium Carbonate in Polystyrene Resin
Resin suppliers and compounders often add fillers to resin base stocks to form high-value filled resins. These resins are typically used for automotive injection molded applications and color concentrates for in-house coloring. Materials are generally compounded on co-rotating, intermeshing twin-screw extruders using a variety of kneading block types. The goal of this work is to describe the effect of three-lobe kneading block configurations on the dispersion of calcium carbonate into polystyrene resins.
Rheology as a Tool for the Polymer Scientist
Rheology is a discipline that has applications both for analysis of polymer structure and for correlation and prediction of processing behavior. As such, rheology has impact over the entire development of a commercial resin. Described are several projects in the areas of polymer blending, aging and fabrication that illustrate the important role that rheology has played in their execution.
Processing Ignition-Resistant Polystyrene Resins in Injection Molding Machines
The demand for ignition-resistant polystyrene resins (IRPS) continues to increase. Moreover, economics at the molder are requiring that these materials cycle faster and still produce high-quality parts. A new high-flow IRPS resin was developed to meet these needs, and this paper describes a plasticating screw design and the process conditions for enhanced performance and improved economics for this resin.
The Effect of a Worn Feed Casing on Plasticating Extrusion
With continued use, a worn feed casing can cause severe rate reductions and unstable operation of plasticating extruders. This paper will present the performance of a commercial extruder with a worn feed casing, and laboratory experiments that show the factors that affect plasticating performance.
Influencing the Foam Structure of CO2-Blown Polypropylene Sheets
An investigation has been conducted to analyze the influence of different process parameters as well as material properties on the structure of CO2-foamed polypropylene sheets. The use of a linear and a branched polypropylene shows the influence of the rheological melt properties on the foam density and the structure. Using the branched polypropylene, densities down to 140 kg/m3 have been achieved. These samples also show a finer and more homogeneous foam structure than the samples made with the linear polypropylene.
Control of Morphology of Polypropylene and Noryl Blend via Melt Mixing
Morphological development of polypropylene/Noryl blends as a function of composition and processing conditions is studied. Effects of processing conditions such as screw speed and residence time, on the morphology and mechanical properties of PP/Noryl blends are investigated. The processing-morphology-property relationship in PP blends is discussed.
The Effect of Processing Variables on the Quality of Injection Molded Foamed Parts
The main objective of the work presented was to determine which operating variables of an injection foam molding process had a significant effect on the physical properties of the EVA foams produced. Statistical design of experiments techniques were used to first screen potential factors and then conduct experiments involving dominant factors to develop empirical response surface models for each of the responses. The models were then verified by testing their ability to predict the results of new experiments both inside and outside the model ranges.
Application of Fused Deposition Modelling in Spray Metal Tooling for Injection Moulding
This paper presents a modified spray metal tooling procedure based on FDM rapid prototyping process, where parting lines were defined in the design stage to simplify and accelerate the spray metal tooling. Core and cavity inserts for injection moulding of a gas turbine blade were created using the modified procedure and successfully injected using LDPE. The procedure significantly shortens and simplifies the tool fabrication process, particularly for complex shapes, when manual parting lines establishment is too complicated and time consuming.
The Effect of Crystallinity on Oxygen and Carbon Dioxide Gas Barrier Properties of PET
Gas barrier of cold crystallized poly(ethylene terephthalate) (PET) was studied as a function of crystallinity. Changes of permeability and solubility versus crystallinity showed complex behavior, which can not be understood in terms of traditional two-phase approach. The data, however, were amenable to interpretation by three-phase model where, in addition to regular amorphous and crystalline phase, the rigid" amorphous phase with density lower than the density of regular amorphous phase was considered."
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