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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Numerical Investigation of the Effect of Screw Temperature on the Melting Profile in a Single-Screw Extruder
Sensitivity of the melting profile to the screw temperature in a single-screw, plasticating extruder was analyzed using a three-dimensional finite element simulation of the melting process. Numerical predictions are compared with the corresponding experimental data from screw freezing experiments. Against the conventional intuition, the predicted melting rate in the compression section of the extruder was found to decrease with increasing screw temperature.
Viscoelastic Flow Model Applied to Tubing Extrusion
Two designs of tube tooling with different draw down ratios were analyzed using a multi-mode viscoelastic flow model to reduce the post-extrusion shrinkage in a cable jacketing process with polyvinylidene diflouride (PVDF). The analysis focused on reducing both elongation and hoop stresses, which were believed to correlate most closely with the shrinkage. Results showed both elongation and hoop stresses were reduced. Cable tensile tests were conducted to compare with the numerical findings.
Properties of Thermoplastic Polyurethanes Derived from H12MDI
Thermoplastic polyurethanes (TPU) based on aliphatic diisocyanates such as 4,4'-dicyclohexylmethane diisocyanate (H12MDI) are indispensable in a variety of industrial, optical, and medical device applications. Relative to 4,4'-diphenylmethane diisocyanate (MDI) based TPUs, H12MDI based TPUs exhibit superior aesthetics, light stability, and biocompatibility. However, the use of H12MDI as a diisocyanate has a major impact on other properties of the final TPU. In this study, the thermal, mechanical, and rheological properties of a typical H12MDI based TPU were characterized and compared to an analogous MDI based TPU.
Purification Procedures to Obtain Chitin Whiskers Employing Shrimp Shells
Two routes for purification of shrimp shells to obtain chitin whiskers were evaluated. The best result was found when demineralization was performed with 1M HCL followed by sample deproteinization with 5% w/v KOH. In order to obtain chitin whiskers an acidic hydrolysis was performed with several acids: HCL, H2SO4 and H3PO4. Chitin whiskers with lengths between 90 and 170 nm were obtained with phosphoric acid. The process was evaluated by FTIR, TGA and TEM.
Analysis of Viscous Heating Effects in a Pressure Slit Rheometer Using Radial Functions Method (RFM)
A pressure rheometer was built to measure rheological properties of polymers at elevated pressures and temperatures. However the viscosity at high deformation rates decreases more than the predicted theoretical value represented by the Cross-WLF model. This paper studies the role of viscous heating in the resulting viscosity deviations by means of simulation using the Radial Functions Method (RFM).
Optical and Mechanical Durability of Polymeric Materials for Solar Collectors
The cost of solar collectors can be reduced by using polymeric glazing and absorber materials, but the durability of their optical and mechanical properties must be demonstrated. Polycarbonate glazings with ultraviolet screening layers have been shown to survive accelerated light intensity for an equivalent 20 years outdoor exposure in Miami, FL. The mechanical properties of two candidate absorber materials—metallocene-based multi-density polyethylene and polypropylene—have been measured as a function of wet and dry thermal exposure.
Surface Damage Threshold in Laser Transmission Welding of Polycarbonate
Paper identifies experimentally the process conditions leading to specimen surface damage of laser-transparent polycarbonate during laser transmission welding. Influence of surface finish, defects and contamination is determined. Surface damage mechanisms are discussed. The surface damage threshold (SDT) is measured over a range of laser speeds and powers. Suggestions are provided for increasing the SDT.
Olefin Block Copolymers as Polyolefin Blend Compatibilizer
Novel olefin block copolymers synthesized via catalytic block technology were evaluated for polyolefin blend compatibilization. It was found that OBC is an effective polyolefin blend compatibilizer for polypropylene-high density polyethylene blend. Significant improvements in mechanical properties were observed. Morphology showed that OBC compatibilized blends displayed reduction in phase size. Cryo-fractured surface analysis and adhesion data from microlayered tapes with OBC as tie layers suggested improved interfacial adhesion for OBC compatibilized blends.
Fiber Jamming and Fiber Matrix Separation during processing of fiber reinforced composites
Fiber jamming is perhaps the least understood defect in molding of polymer composites. This paper presents a dimensional analysis developed to predict fiber distribution in ribbed sections. The model shows that parameters like mold closing speed and polymer viscosity can be optimized to decrease fiber matrix separation.
Influence of a Triangular Stress Concentrator on the Mechanical Properties of Plastic Parts
The influence of a stress concentrator on the mechanical properties of injected plastic parts was studied. Polystyrene plaques with different dimensions of a triangular concentrator were injected. Melt temperature, injection and holding/packing pressures and injection speed were modified in order to determine their influence on the stress concentrator factor (Kt). The experimental results were compared with the simulation ones. It was verified that Kt depends on geometrical parameters and process conditions of the injected plastic parts.
Effect of the Process Conditions over the Adhesion between Two Overmolded Polymers
The effect of the injection molding process conditions (melt and mold temperatures, holding/packing pressure and injection velocity) over the adhesion resistance of two overmolded materials was studied. The materials used were a Thermoplastic Vulcanized Elastomer (TPV) (Santoprene 8211-55) and a Polypropylene (PP) (Moplen HP501H). The measurement of the adhesion resistance was done by Tensile Test and it was observed that the melt and mold temperature are the parameters that affect in greater degree the adhesion resistance.
New Coating Equipment to Produce Long Fibre Thermoplastic Matrix Towpregs at Industrial Scale
This work describes modifications made in a previously developed powder coating equipment used to produce long fiber thermoplastic matrix towpregs. The major modifications include the incorporation of new deposition and heating techniques that enable producing GF/PP towpregs at rates compatible with the industrial production requirements (approx. 10 m/min). GF/PP and GF/PVC towpregs were produced in this new equipment and tested to verify its polymer content and degree of impregnation. This paper presents and discusses the results already obtained.
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.
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