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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Practical Approach to Screw Breakage and How to Avoid Failures
The use of practical mathematical expressions can be used to evaluate the mechanical strength of a rotating shaft. Similar expressions can be used in the design of a feedscrew. The purpose of this paper is to investigate the factors that influence the mechanical strength of a feedscrew and to show how to use these expressions from a practical standpoint to avoid failure during operation.
Effect of Screw Surface Properties on Extruder Performance
The surface condition of the screw and die can have a significant effect on extruder performance; however, little information about these effects is available in the open literature. This paper discusses various aspects of the screw surface conditions and how these can change the characteristics of the process and extruded product quality.
Die Lip Sensitivity in Cast Film Dies
Die designs for production of cast polymer films typically include a flex lip for varying the geometry of the lip opening. The cast film process requires die lip gaps ranging from 0.4 mm to 0.8mm. Flex lip gap and the adjustment of said gap becomes increasingly difficult to control as it is reduced. An examination is made of the issue of die lip sensitivity with different polymers extruded at different lip openings.
Metering Channel Flows and Troubleshooting Single-Screw Extruders
The manufacturing costs for a process depend highly on the proper operation of the extrusion equipment. In general, proper operation requires that the metering section of the screw be the rate-limiting step. Using drag flow and pressure flow calculations for the metering section is a simple method to determine if the section is the limiting step. This paper shows how these types of calculations can be used to determine if the screw and process are functioning properly.
Reactive Extrusion of Starch-Polyacrylamide Graft Copolymers
Graft copolymers of starch and polyacrylamide have been prepared using a twin screw extruder. The effects of monomer/starch ratio and moisture content on conversion, graft efficiency, graft molecular weight, and frequency of grafting are discussed. Conversion of monomer to polymer exceeding 90% and grafting efficiencies exceeding 60% can be achieved by this process, with residence times of approximately 250 seconds or less.
Compatibilizing of PET/PA Blends with a New Coupling Agent in a Twin Screw Extruder
Polyethylene terephthalate (PET) and Polyamide (PA) can be compatibilized in one process step on a twin screw extruder using a novel coupling agent. This reagent is able to react with PET as well as with PA which leads to Copolyesteramids. Until now a compatibilisation was only possible in a three step process, this new reagent makes a one step process possible.
Chemical Coupling of Rubber Polymers with Modified PTFE Micro Powder during the Rubber Mixing Process
A special mixing procedure has been developed for chemical coupling of PTFE micro particles with the polymeric matrix in rubber compounds. Beforehand the non-reactive PTFE is modified to enable the chemically coupling. It is supposed that parts with chemically bonded PTFE particles will show higher abrasion resistance and a better friction behavior compared to those with physically bonded particles. Thus the production of novel wear resistant elastomers should be possible.
The Effect of Multilayer Rheology on Coextrusion Die Design
Multilayer coextrusion is a process in which two or more polymers are extruded and joined together in a feedblock or die to form a single structure with multiple layers. This paper will discuss the proper techniques for using rheology data to design coextrusion dies based on experimental rheology data for monolayer and multilayer structures.
The Effect of Process Aids on Interfacial Instabilities in Coextrusion Flows: Theoretical and Experimental Investigation
In this paper, the effect of process aids on the interfacial instabilities in coextrusion flows is investigated theoretically via viscoelastic FEM simulations as well as experimentally. Theoretically determined processing/materials rules according to which a stabilization effect with process aids can be achieved are compared and discussed with experimental results.
Interlayer Adhesion of Co-Extruded Sheets before and after Biaxial Stretching
In order to quantify interlayer adhesion of co-extruded sheets with strong interlayer adhesion, a test method was developed to first initiate delamination by uniaxial stretching and then measure interlayer adhesion by peel test. The method was applied to co-extruded sheets before and after biaxial stretching. Interlayer adhesion with peel force as high as 5330N/m (30lb/in) have been measured for the as co-extruded sheets. Reduction of interlayer adhesion as a function of biaxial stretching was revealed.
Continuous Compounding of EPDM Formulations on Co-rotating, Intermeshing Twin Screw Extruders
A 58 mm twin screw trial was run to evaluate machine design, shear and heat transfer effects in a generic EPDM formulation. The effects of product rate, screw speed, screw design, barrel temperature, and screw cooling were evaluated on product temperature, Mooney viscosity, and cure time. Scale up is evaluated in terms of heat transfer (cooling), volumetric and torque limits. Operation at high specific rate, low barrel temperatures, and the use of screw cooling provide improvements for rate. Commercially viable throughput rates were achieved in the trial.
Ultrasonic Monitoring of Barrel Wear and Screw Status
Four types of high temperature (HT) ultrasonic sensors have been installed at barrels and a flange of a 30-mm twin-screw extruder to non-intrusively and non-destructively measure barrel and screw wear, as well as screw misalignment and deflection during polymer extrusion. The sensors included sol-gel sprayed ultrasonic transducers (UTs), non-clad and clad buffer rod sensors, and stand-alone HTUTs. This study has demonstrated the capability of these ultrasonic sensors in monitoring the barrel and screw statuses at the pumping, mixing and melting zones of the extruder.
Development of a Stiff, Void Free, Low Density Plastic Wood Replacement
Process studies attempting to produce a low density, wood like replacement involving Kenaf, Polypropylene and hollow glass spheres (bubbles") blends along with processing aids and compatibilizers have been investigated using a counter-rotating non-intermeshing (CRNI) twin screw extruder. Bubble breakage was higher than anticipated based on related work but in spite of the fairly low bubble survival rates nailability of the boards was improved. Bubble breakage and mechanical properties are presented along with a discussion of the narrow process window."
Hydraulic Conveying of Plastic Pellets
Today’s plastic production plants can have a yearly capacity of more than 400,000 t. New catalysts enable them to produce a great variety of increasingly softer product grades in the same reactor. Together with logistic concepts that increase conveying distances, the polymer industry has reached the limits of traditional dilute and dense phase pneumatic conveying systems.This paper presents a new concept to convey plastic pellets as water slurry to overcome the limitations of pneumatic conveying. A further benefit of this technology is the gentle handling of attrition sensitive plastics like Polycarbonate and Polyester.
PTFE Paste Extrusion: Effect of Physical Properties of Lubricants
Preforming and the physical properties of the lubricants play a crucial role on PTFE paste extrusion. Since the most significant effects on liquid migration are due to viscosity and the wettability, the lubricants were characterized in terms of both flow and surface properties. These two properties were altered independently to study their relative effects on PTFE paste processing. Based on this study, it was concluded that preform quality and the extrusion pressure increase with increase of viscosity and improvement in the wettability characteristics of the lubricant.
The Determination of the Best" Viscosity Model for Shear Thinning Fluids from Capillary Rheology Experiments"
This paper describes an algorithm used to determine a single viscosity correlation from capillary rheometer experiments. One can choose any one of seven commonly used models for shear thinning fluids. The program then determines the constants in the chosen model which best describes all of the experimental data in a statistical (i.e., least sum of squares) sense. By comparing the results from several different models, one can determine in a matter of minutes the model, which best describes the measured rheology data.
High Performance Polyethylene Resins for the Thin Wall Injection Molding Market
A new single-site catalyst and process technology has been used to produce resins for thin wall injection molding lid applications. The performance of the single-site resins is compared with conventional Ziegler-Natta resins. The single-site polyethylenes provide superior processability with less mold deposit and organoleptic concerns. Additionally, these resins possess equivalent or better stiffness and toughness versus competitor products along with an unusually high level of clarity in the final parts.
Effect of Cyclic Cooling on Power Consumption of the Injection Moulding Process
The performance of a cyclic mold cooling system has been investigated with particular emphasis on process power consumption. A highly instrumented proportional-hydraulic injection molding machine was used to produce tensile test specimens from HDPE. Mold temperature was monitored at high frequency during each cycle, as was nozzle melt pressure, temperature and power consumption. Reduced cycle times were achieved with cyclic cooling and savings in power consumption of up to 23% were recorded over conventional methods.
A Novel Microcellular Co-Injection Molding Process
This paper presents the development of a novel microcellular co-injection molding process that combines aesthetic and processing advantages of injection molding with the benefits and property attributes of microcellular plastics (MCPs). While eliminating the swirling patterns seen on surface of microcellular plastic parts, this process is capable of producing lightweight parts with lower energy requirements, better dimensional stability, reduced sink marks, and desirable microcellular structure with fine cells and high cell density.
Real-Time, Non-Intrusive and Non-Destructive Ultrasonic Monitoring of Injection and Co-Injection Molding Processes
Integrated ultrasonic sensors directly coated onto mold inserts of a molding machine together with rugged ultrasonic system are used for real- time, non- intrusive and non- destructive monitoring of injection and co- injection molding processes. Monitoring of flow front arrival, flow speed, filling completion, solidification, part detachment and thickness of skin and core inside the mold has been demonstrated.
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