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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Displacement and Strain Analysis in a Non Homogeneous Material
Electronic holography moiré is applied to the measurement of interfacial conditions between particle and matrix in a non homogeneous rubber material. A tensile specimen is subjected to creep loading. The loads are applied in steps and measurements are carried out at equal intervals of time. The final output is provided by the Holo-Moiré Strain Analyzer and gives the principal strains and their directions in the region of observation. A definition of adhesion as an experimental measurable quantity through the evaluation of contour integrals is introduced.
Applications of Large Volume Processors in Polymer Processing
In recent years, pressure from economic and environmental requirements has been experienced in the field of polymer production. This trend towards single stage operational units, in processes such as low shear devolatilization of elastomer solutions, radical polymerization and polycondensation reactions, phase changing processes and the conversion from batch to continuous operation continues and has lead to the development of large volume, twin shaft horizontal processors (LVPs).These processors have been designed for applications requiring medium to long residence times (20-120 minutes).As an example of this new family of processors, the multi-purpose Reasol®, a new counter-rotating twin shaft processor, is introduced. Trials with model polymers have been performed in a 60L unit at the developer's test center. Its performance is described here by power consumption, RTD (residence time distribution) and self-cleaning and devolatilization efficiency.Trials show that product transport through the new LVP is characterized by a narrow RTD with a high degree of self-cleaning. Typically, the RTD exhibits a Peclet number in the region of 25-35. It is also shown that, unlike typical twin-screw extruders, the shape of the RTD curve is largely unaffected by the rotor speed or mass rate. Furthermore, rotor speed has a relatively small effect on mean residence time thus allowing the freedom to optimize rotor speed with respect to other processing objectives such as heat transfer, surface renewal or shear rate.The indications are that the characteristics of the RTD, power consumption and devolatilization are analogous to more traditional equipment such as twin screw extruders in spite of the larger free volume and residence time and the lower shear.The new LVP is commercially available up to sizes of 12,500 litres net processing volumes.
Predicting Plastic Energy Dissipation (PED) Using Phenomenological Constitutive Equations for Glassy and Semicrystalline Polymer Solids
It has been experimentally demonstrated that Plastic Energy Dissipation (PED) is a dominant melting mechanism in twin-rotor co- and counter-rotating processing equipment. Such devices force compacted polymer particulates to undergo repeated compressive, volume-wise, large compressive deformations, resulting in massive dissipative heating of the solid particulates and rapid melting. The large magnitude of PED has two important consequences: it results in very rapid end efficient volume-wise melting, enabling very fast processing rates and produces a very narrow “age distribution” melt, important for reactive processing. To date the experimental evaluation of PED, during large unconfined compressive cylindrical sample deformations, at appreciable strain rates, can be used to arrive at reasonable engineering estimates of the melting lengths for given polymers in specific processing equipment operating under given processing conditions. But this task involves a large number of PED-evaluation experiments, because of the lack of constitutive equations which are capable of describing the compressive stress-strain behavior of solid polymers at “engineering” strains and strain rates. The object of this presentation is to evaluate and modify existing constitutive relations for amorphous polymers using the large experimental date that have been generated in our laboratories. An acceptable constitutive relation will not only reduce the number of experiments necessary to evaluate PED and estimate melting lengths, but a needed element in the development of PED melting simulation models.
2D Composite Models of Modular Intermeshing Co-Rotating Twin Screw Extruders
A new 2D composite model with the hybrid FEM/FDM was developed for simulating the fully filled and starved regions with the associated pressure profiles of a modular intermeshing co-rotating twin screw extruder. 1D composite models combine the screw characteristic curve of individual element to analysis flow of an entire modular screw and the flow fields of the whole region are not calculated again. Based on the linear relationship of the drag flow rate and the screw rotating speed under the single screw extrusion theory, the new mesh with artificial screw rotation speed boundary conditions was used to simulate the entire flow analysis for the co-rotating twin screw extrusion process in our 2D composite models.To demonstrate applicability, the results provided by our 2D composite models were found to similar to those of 1D composite models, through Fenner’s single screw example. The pressure and filling factor profiles in a modular TEX44 extruder provided by 2D composite models show good agreements with Fukuoka's calculated results and experiment data.
Sequential Mixing Methods of Environmentally Benign Nanocomposites from Cellulose Acetate/Plasticizer/Organoclay System
Injection molded nanocomposites have been successfully fabricated from cellulose acetate (CA), triethyl citrate (TEC) plasticizer and organically modified clay. The effect of sequential mixing methods and plasticizing conditions on the performance of these nanocomposites has been evaluated. The mechanical and thermal properties of nanocomposites are correlated with the XRD and TEM observations. Cellulosic plastic-based nanocomposites with 75-minute pre-prasticized CA/TEC/organoclay showed the best exfoliated structure.
Application of GRP for Chimney Liners Exposed to Sulfur Dioxide and Sulfur Trioxide
Innovative development and application of a multilayer GRP structure for chimney liners exposed to sulfur dioxide and sulfur trioxide are described.The structure is made by winding. It includes a chemical proof layer, a constructional layer and an external layer.Inspections have shown no deterioration of GRP after three months of operation. GRP are affective constructional material of the universal purpose.
Novel Technique for Predicting Long Term Resistanse of Chemical Resistant GRP
A novel technique of estimating the lifetime of chemical resistant GRP is described.Destruction of GRP is considered as a heterogeneous chemical reaction of the first or zero order with constant energy of activation.Based on these estimations, it is recommended to use GRP for chimney liners exposed to sulfur dioxide and sulfur trioxide. Received results were used for forecasting of service life of GRP.
Rheological, Thermal and Mechanical Behavior of Polyolefins/Sea Shells Composites
The rheological, thermal and mechanical behavior of polypropylene (PP) and high density polyethylene (HDPE) filled with sea shells composites at different concentrations of filler were investigated. The composites were prepared by extrusion and injection molding. Most filler addition to composites promoted a slightly increase on the melt viscosity, improve the tensile modulus and the thermal stability in all composites studied.
Study on the Characteristic of Axial Circular Flow Field in Co-Rotating Intermeshing Twin-Screw Extrusion
In order to improve the mixing ability and elongate the mean residence time in twin-screw extruders, the axial circular flow was introduced in this study. A non-intermeshing section was set in the co-rotating twin-screw extruder, in which one screw was equipped with reverse conveying elements and the other with forward conveying elements. In the current work, a three-dimensional simulation of the flow in the axial circular flow section was developed by FEM package, ANSYS. Based on the calculated pressure and velocity profile, the pressure-throughput behavior and mixing ability of the axial circular flow section were discussed. Compared with the conventional conveying elements, the circular flow section has reduced ability to conveying but its distributive mixing capability was largely increased. Visualization experiments showed that the simulation results were in good agreement with the experimental outcomes.
3-D Modeling of Polymerization in Conveying Screw Element in Twin-Screw Extruder
The polymerization of ?-caprolactone in fully intermeshing conveying screw elements of co-rotating twin screw extruders was simulated with Fluent. The effects of the pitch on the element, temperature, flow rate, and screw rotating speed upon the reaction progression were investigated. It was found that the back-flow in the screw element affects the progress of polymerization. The simulation result from 3-D model differs significantly from 1-D model, especially in relation to slow reactions. This is because reaction is very sensitive to temperature change, and the value of heat transfer coefficient at the barrel and screw surface used in 1-D model may not represent the real conditions in extruders.
Investigation on Extrusion Property of PSE?Polygon Screw Element in Co-Rotating Twin Screw Extruder
PSE (Polygon Screw Element) is a new screw element, designed to meet the development of co-rotating twin-screw extruders toward high rotating speed and excellent mixing capability. In the present study, a three-dimensional flow field simulation of PSE element was carried out by the ANSYS FEM package. Pressure profile and shear stress profile were obtained. The mixing ability of PSE element was also analyzed. The simulation results of the flow field in PSE element were verified by experiments. It was found that the energy consumed in PSE element is smaller, whereas its mixing ability is better than the kneading block. Furthermore, PSE element is suitable for the fiberglass reinforced processing.
A New Machine Conception for the Extrusion of Biodegradable Foams and the Influence of Process Parameters on Product Propert
Foamed products based on renewable raw material have a high application potential e.g. for packaging because of their biodegradeability. This may permit renewable raw materials to substitute polymers like polystyrene in some applications.A common way to process renewable raw material like starch is to produce starch based resins with twin screw extruders. These resins can be used on conventional polymer processing machines, but the step of compounding the starch on twin screw extruders causes costs which make these resins economically unattractive.Due to a new extrusion technology these costs can be reduced by a direct processing of starchy material like maize. A characteristic of this extruder is a very short (2 L/D), conic, multiple flighted screw in a barrel with spiral grooves. The energy for the plasticizing process is yielded just by the transfer of mechanical energy of the rotating screw into friction in a shear gap between screw and barrel.In order to understand the process different geometries of screw and barrel have been used in the experiments, additionally the process parameters have been varied. The results lead to an optimised configuration of the extruder and to a better understanding of the influence of process parameters on the product properties.
Effect of the Full-Slip Condition along Rotors on the Mixing Efficiency of Internal Mixers
The importance of slip for applications such as extrusion, cable coating, thermoforming, etc. has been widely discussed in the literature. Recent experimental works suggested that slipping along the rotors also impacts the quality of the mixing in batch mixers typically used for Carbon Black dispersion. In batch applications, the slip reduces the mixing efficiency, hence requiring a longer process to get a given mixing quality.Recent developments in CFD allow to include the slip in the numerical models. The advantage of numerical simulation is the ability to turn on or off this phenomenon. Also, the effect of particles behavior along the rotors on both the flow pattern and the mixing efficiency of internal mixer is studied. Two 3D transient simulations are performed with the POLYFLOW package: one simulation assumes sticking boundary conditions along the rotors whereas the other involves a full slip condition.The results obtained in both simulations are compared and validated against experimental results: the slip condition modifies dramatically both the velocity and the shear rate fields. Therefore, the distributive and dispersive mixings generated by the two models are significantly different. Eventually, we observe a better match between numerical and experimental results when the slip condition is taken into account.
Effect of Morpholgy on Mechanical Properties of Composites Prepared by Reaction-Induced Phase Separation
A new class of fiber-reinforced composite materials was designed in our laboratory by using a hybrid of thermoplastic and thermosetting polymers. The thermosetting polymer phase separates upon curing reaction and creates morphology on the fiber surfaces. Effect of the morphology is studied on the fracture toughness of the composite, with the aim of enhancing the mechanical properties of the resulting fiber reinforced composite.
NMR Analysis for a Secret Ingredient
Finding very small amounts of a secret compound in complex mixtures presents a big challenge for analysts. A dispute between two companies involved building plasters with a polymer viscosity modifier. The case hinged on confidential information about the exact structure of the polymer, which one company had apparently taken illicitly from the other. FTIR revealed little, so NMR was used to identify the compound in deuterated DMF extracts from the plasters. They showed that the plasters possessed compounds of identical structure. The case was settled without trial.
Polymer-Clay Nanocomposites: Tailoring Structures with Processing Conditions
Nanocomposites based on nylon-12 and synthetic fluoromica were compounded using a single-screw extruder at different combination of shear and residence time and analysed with respect to their morphology, rheological, mechanical, and thermal properties. Transmission electron microscopy (TEM) and X-ray diffraction (XRD) revealed unique structural arrays of the exfoliated layers which were found to be dependent on the extent of shear and residence time during processing. Rheological analysis showed that the melt viscosity of the nanocomposites was considerably lower compared to the unfilled polymer. Furthermore the melt viscosity and properties of each nanocomposite varied depending on orientation of the exfoliated layers. The results show that it may be possible to tailor the structures and properties of the nanocomposites using controlled extrusion conditions.
Some New Observations Relative to Melting in Single Screw Extruders
The focus of this investigation was to evaluate literature and run experiments to help understand the mechanism of melting in single screw extruders. Literature data was re-analyzed using video capture and analysis programs to determine the rate of loss of material in the cross channel and solid bed thickness directions. The analysis demonstrates that the polymer solid bed goes to zero dimension in the thickness direction well before the solid bed width is consumed. This observation was confirmed in our laboratory using a specially built glass barrel extruder. These results suggest that the melting in single screw extruders is dominated by the loss of bed thickness and not bed width as predicted by current literature.
The Influence of Morphology on the Failure of Polyethylene Pipes in Hydrostatic Pressure Tests
Failure times of plastic and metal pipes subjected to hydrostatic pressure at various levels assist pipe manufacturers to not only design pipes for certain applications, but also to give them an indication of the useful service life-times of these pipes. In order to understand the influence exerted by semicrystalline morphology on the failure of polyethylene pipes under hydrostatic pressure, a medium-density polyethylene resin was converted into various pipes by altering the extrusion processing conditions. These pipes were subsequently subjected to hydrostatic pressure at a constant hoop stress and the failure times were recorded. The failure times were observed to depend strongly on the morphology of the pipes.
Computer Aided Troubleshooting of Extrusion Problems
When a problem occurs in an extrusion operation it is important to diagnose the problem, determine possible solutions, and implement the best solution in the shortest possible time. In-house personnel are often not well trained in efficient troubleshooting techniques and problem solving. Outside technical assistance may not be immediately available and may not lead to an expedient solution of the problem. As a result, it is important for extrusion companies to have tools available in-house that can help in the troubleshooting and problem solving process.A new tool available to the plastics industry is an expert system that allows computer aided troubleshooting of extrusion problems. This program allows the user to systematically analyze a large number of extrusion problems. In the end the program presents the user with a number of possible solutions to the problem. This paper will describe the capabilities of the program.
Study of the Micropelletization Process
A study has been performed to examine the rheological impact of micropelletization on several polyethylene grades with melt index values between 1-5 g/10 min. The experiments were done on a 50 mm 30:1 L/D extruder with an underwater micropelletizer attached. A 2-D finite element simulation was used to assist in the analysis by comparing the observed results to the predicted shear stresses in the die. The average micropellet size collected was 0.525 mm diameter. Minor sharkskin was observed on the surface of micropellets due to the high stresses experienced in the pelletizer die. However, the rheological properties of the micropellets did not change in comparison to the virgin resins.
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