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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Aspects of Electrospinning Process Control from Fundamental Mechanisms
For large-scale application of electrospinning technology, it is important to know how to maximise and control the deposition rate of spun fibre. Driving polarity, substrate material and current flow were examined to quantify their effect on fibre deposition rate. Conductivity of the substrate and polarity of driving electric charge were found to affect the mass deposition rate. Higher deposition rates were the result of the production of thicker fibres and an increase in deposition speed.
Influence of Processing Parameters on Shrinkage of LDPE Parts in Gas-Assisted Injection Molding
The part properties are determined by quality of gas penetration in gas-assisted injection molding (GAIM), while processing conditions determine gas penetration. This research aimed to investigate some of the processing parameters, such as shot size, gas delay time and gas pressure. The effect of processing parameters on shrinkage ratio was discussed, as well as that how they influenced the part performance.
Nitroxide-Mediated Controlled Degradation of Polypropylene
The purpose of this work is to evaluate a new polypropylene (PP)–based nitroxyl radical generator (NOR) and offer comparisons with a commonly used peroxide in the production of controlled-rheology polypropylene (CRPP) resins. CRPP resins are produced by reactive processing in a batch mixer by using different amounts of either the NOR or a peroxide initiator at different temperatures. Molecular weight and rheological properties are determined for all CRPP produced and a comparison between the effectiveness of the NOR and the peroxide initiator is provided.
Optimum Design of PET Bottle Bases against Stress Cracking
Petaloid shaped base for the carbonated soft drink bottles made out of (polyethylene terephthalete) (PET) is quiet common; and there are currently a few bottle designs with slightly different petaloid base in the market. While the petaloid bases provide stability to the bottles; stress cracking of the base during hot climates occurs.In this study, dimensions of the petaloid base against stress cracking are optimized via a FEA software package. Based on the simulation results, a new design for the petaloid base and optimum process conditions for the production of PET bottles are proposed.
A New Approach for the Injection of Physical Blowing Agents in Foam Extrusion
A new injection technique for introducing physical blowing agents into molten polymer is studied for its application in foam extrusion. Therefore, a special injection device is mounted on a standard laboratory scale single screw extruder. By means of this device, CO2 is injected into PS melt. In this paper first results of these preliminary tests are shown. The foams produced with this new technique exhibit a cell size in the range of 100 microns.
Reduction of Cooling Time by Using Atomized Water in Blow Molding
In the blow molding process, the blown part is primarily cooled by contact to the mold. Using internal cooling it is possible to reduce the cooling time. Using atomized water, is a new method to increase the heat flow at the internal surface. At the IKV the blow mandrel and the blow molding machine are modified to inject atomized water. The achievable cooling time reduction depends on the amount of the injected atomized water. The test series show that a reduction of cooling time up to 41% is achievable.
Crash-Simulation for Short-Fiber Reinforced Thermoplastic Parts
The anisotropic material behavior of injection-molded, short-fiber reinforced thermoplastic parts can be taken into account in mechanical simulation today by linking process simulation and structural analysis. However, the prediction of the crashworthiness of short-fiber reinforced parts is still performed predominantly using isotropic material models as a substitute. An approach to include anisotropic material behavior into crash-simulation has been developed at the Institute of Plastics Processing in order to advance simulation quality.
Dynamics of Hot Runner Purging
Purging of hot runners consumes an inordinate amount of time, materials and money. A study to get an efficient color or resin change makes use of the viscosity reduction by varying process parameters, and using purge additives that influence viscosity and self cleaning characteristics. This paper reports a part of a study on how that shear rate and the temperature in the hot runner manifold and barrel affect purging. The results show that very high and low melt temperatures in both of them affect purging. The best temperature setting is a low temperature in the hot runner manifold and a low temperature in the barrel.
Wood Fiber Reinforced Polyamides
Wood fibers are often used to reinforce polyolefins but not high temperature polymers like polyamide 6 and 66. These polyamides melt above 200 °C, which is often considered the maximum processing temperature for wood fibers. A variety of techniques for compounding and molding wood fiber/polyamide composites will be presented. These techniques are evaluated by examining fiber dispersion, fiber attrition and composite mechanical properties.
A Novel Approach for Measuring the Specific Volume of (Semi-Crystalline) Polymers at Elevated Cooling Rates Using X-Rays
A new method to determine the specific volume of polymers over a wide range of temperature and pressure based on X-ray attenuation was developed. This method allows the application of different cooling rates enabling the investigation of the density depending on the thermal history. Experiments were performed to investigate the devolution of the specific volume of an isotactic polypropylene at elevated pressures and cooling rates.
Effect of Die Geometry and Extensional Rheological Properties on Vortex Development in Rectangular Dies
The vortex development of a low-density polyethylene in different flat dies under various processing conditions has been analyzed by the Finite Element Method employing the modified White-Metzner model as constitutive equation. The theoretical results are compared with the velocity distributions measured by Laser-Doppler Velocimetry (LDV).
Optimization of Rotational Molding Cycle through Thermal Data Acquisition
The DataPaq Rotomolding Telemetry System in conjunction with the Medkeff/Nye Shuttle PD developmental rotational molder was used to study and monitor internal mold and oven temperatures. Continuous internal temperature readout along with the software package were used to optimize the cycle of linear low density polyethylene (LLDPE). Designed experiments were employed to investigate process parameters and select physical and mechanical properties.
An Experimental Study on Shear Stress Characteristics of Polymers in Single-Screwextruders
Frictional forces (for temperatures less than melting or devitrification temperature) and viscous forces (for higher temperatures) have important roles on solids conveying and melting processes in single-screw, plasticating extruders. These forces are related to the shear stresses at polymer-metal interfaces. This paper presents the shear stresses and melting fluxes at four sliding velocities and at temperatures ranging from ambient temperature to 230°C for LDPE, ABS, HIPS, and LLDPE resins at a fixed pressure of 0.7 MPa.
Summary Results of a Novel Single Screw Compounder
A novel single screw mixer is described having multiple elongational flow fields, upstream axial mixing, and thin film degassing. SEMs show high magnification examples of mixing including a PS/PE immiscible polymer blend, ceramic nano particles, and iscrete carbon nano tubes. Novel degassing over the mixer is cited using three vents in a 36/1 L/D single screw to process undried PETG.
Advances in Adhesion with CO2-Based Atmospheric Plasma Surface Modification
The use of gas and/or liquid-phase carbon dioxide (CO2) with atmospheric plasma discharge surface pretreatment technology can remove micron and submicron particulates and hydrocarbon-based contaminations on plastics and metals. The cleaning process is based upon the expansion of either liquid or gaseous carbon dioxide through an orifice. The paper provides an understanding of the basic removal mechanism and provides experimental evidence of remarkable adhesion improvements relative to a broad range of applications in electrical, medical, and automotive manufacturing communities.
Fundamental Structure-Property Relationship of Polymer Nanocomposites
The structure-property relationship of a set of model polymer nanocomposite systems has been investigated. The findings suggest that degree of exfoliation and aspect ratio of nanoplatelets in polymer matrices can greatly influence physical, mechanical and rheological behaviors of polymers. Most importantly, there appears to be a limit to which polymer nanocomposites can be applied for structural applications.
The Role of Chain Branching in Extrusion Blow Molding of Polyvinylidene Fluoride
The effect of long chain branching in polyvinylidene fluoride in extrusion blow molding is investigated in light of the enhanced rheological properties. The presence of long chain branching increased the melt strength; melt elasticity and strain hardening of the branched samples as opposed to their linear counterparts. These enhanced properties suggest better sag resistance during blow molding and higher blow-up ratio while achieving uniform wall thickness.
Efficiency Gains and Control Improvements Using Different Barrel Heating Technologies for the Injection Molding Process
This paper compares the energy efficiency and control response of band-heaters with a new technology that uses non-contact induction to heat the barrel directly through an interposed layer of thermal insulation. Quantitative results from both laboratory injection molding machine runs and bench-top tests are reviewed. The effect of barrel diameter, surface condition and band-heater type on efficiency and control response are also considered, as are the implications of thermocouple depth.
Evaluation of Fracture Toughness for Thin-Wall Injection Moulded Plastics
Evaluation of fracture toughness was studied by means of essential work of fracture (EWF), using 1mm thickness injection moulded double-edge notched tensile (DENT) specimens with two types of materials, ABS and PP. Stress level analysis is discussed in this paper by means of maximum nominal stress.
Full 3D Injection Molding Analysis and Modeling Tips for Complex Models
3D injection molding analysis is getting popular to get accurate result in the industry. However, mesh generation time and memory size for complex models are being demanded more than those of general model or conventional 2.5D analysis. This paper adopts simulation technology such as CVFEM(Control Volume Finite Element Method) or fast multipole method based on BEM(Boundary Element Method) and shows real case for large models. It does not only develop effective method to reduce modeling time, but it also performs analysis with significant performance enhancement.
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