8:00 am – 11:30 am:
M4-Extrusion: Twin Screw I
(Moderator: Costas Tzonganakis)-Room S320F
Cailiang Zhang, Zhejiang University
Polymer blending is a convenient and effective way of producing new materials with property synergies and without creating new molecules. In most cases, Twin Screw Extruders (TSE) is used for carrying out polymer blending processes due to their unique mixing performances. However, it is very challenging to investigate flow, mixing and reaction performances of polymer blending processes in a TSE because of short residence time and complex operation conditions. For this reason, a concept of compatibilizer-tracer developed in this work is able to take this challenge. The reactive compatibilizer-tracer, which bears reactive groups capable of reacting with its counterpart upon forming a copolymer for in-situ compatibilization of a reactive polymer blend and at the same time fluorescent labels allowing determining very small amounts of the in-situ formed compatibilizer. The use of the reactive compatibilizer-tracer together with transit experiments has allowed assessing the effects of processing parameters such as screw configuration, feeding mode, blend composition and screw speed on flow, mixing and reaction performances of polymer blend in a TSE. The results provide fundamental insights into flow, mixing and reaction performances of a TSE for polymer blending.
8:30 am – 9:00 am:
Effect of High Speed Twin and Quad Screw Compounding on the Molecular Weight, Molecular Weight Distribution, and Mechanical Properties of Polyethylene Composites
Mansour Albareeki, UMass Lowell
In this study, a particulate-filled polymer composite was compounded with ultra-high-speed twin and quad screw extruders to investigate the effects of screw speed and intermeshing area on 1) the molecular weight and molecular weight distribution and 2) the mechanical properties of the resultant composites. In general, the quad screw extruder produced significant decreases in the molecular weight of the neat polymers, with greater decreases observed with higher molecular weight polyethylenes. Examination of Gʺ/Gʹ crossover points showed that higher screw speeds produced decreases in molecular weight, but narrowing of the molecular weight distribution. These results were more affected by material system than extruder type. Since the quad screw extruder provided better filler dispersion combined with reductions in molecular weight, it produced no change in elongation at yield and break for filled LDPE, decreases in elongation at yield and increases in elongation at break for MDPE, and increases in modulus that were not significantly affected by screw speed. The flexibility of the materials created Izod impact results that showed no major changes with extruder type or speed.
9:00 am – 9:30 am:
Experimental Validation of Fill Ratio, Resin Pressure, Resin Temperature Obtained From the 2.5D Hele-Shaw Model in Flow of Corotating Twin Screw Extruder
Masatoshi Ohara, TOSHIBA MACHINE CO., LTD.
Filling ratio, resin pressure and resin temperature are important process parameters related to the residence time distribution and thermal history of resin in a twin-screw extruder. This study presents a series of experimental results of these parameters and compares them with the values obtained from the 2.5D Hele-Shaw model calculation developed in our group recently for a twin screw extruder. Homo polypropylene with melt flow rate of 7.0 g/10-min was feed to a ϕ 26 mm co-rotating twin screw extruder. Temperature and pressure of resin were measured using sheathed temperature sensor and pressure transducer contacting to molten resin. Fill ratio distribution was measured by our laser light section method. The experimental results of resin pressure, temperature and fill ratio agreed well with the simulation results. It was validated that the Hele-Shaw model is valid for co-rotating twin screw extruder.
9:30 am – 10:00 am:
Designing and Computational Validation of Extensional Mixing Elements (EMEs) for Improved Dispersive Mixing in Extrusion Operations
Vivek Pandey, Case Western Reserve University
Extensional Mixing Elements (EMEs) have been developed to impart extension dominated flow in twin screw extruders (TSE) through hyperbolic contraction channels. In this manuscript, EMEs for TSE have been made more aggressive by incorporating double hyperbolic contraction (contraction in horizontal as well as vertical direction) and were also successful in designing novel modular screw design for single screw extruder (SSE) to have dispersive and distributive mixing simultaneously. The design geometry of EMEs have also been optimized for both TSE and SSE using computational simulations.
10:00 am – 10:30 am:
Characterization of Stress in a Twin-Scre Extruder for Processing and Extrusion of Extrinsically Self-Healing Thermoplastics
Connor Armstrong, University of Maryland, College Park
LSAMP Bridge to Doctorate graduate research fellow at the University of Maryland, College Park
10:30 am – 11:00 am:
Improved Nanoclay Dispersion in Ethylene Vinyl Alcohol via Sub-critical Gas-assisted Processing
Thomas Ellingham, UW-Madison
Ethylene vinyl alcohol (EVOH) was melt compounded with an organo-modified nanoclay (NC) at a loading level of 5% by weight in a twin-screw extruder (TSE) using a sub-critical gas-assisted process (SGAP). Carbon dioxide (CO2) and nitrogen (N2) were used as blowing agents to induce foaming inside of the barrel of the extruder and as the melt exits the die. Samples processed with SGAP without mixing elements demonstrated better dispersion of NC versus the traditional extrusion process with mixing elements due to the additional stresses that bubble expansion provides during foaming.
11:00 am – 11:30 am:
New Involute Extruder Screw Elements for Improved Productivity and Quality
Paul Andersen, Process Engineering Consultant, Coperion
The co-rotating fully intermeshing twin-screw extruder has evolved significantly in the 60 years since it was commercialized in 1957. While this equipment might be considered a “mature” technology, it has not experienced a decline in new developments as might be expected, but rather a significant number of advancements. The technology continues to evolve. For example in the last 20 years several significant developments have been introduced. These include a) the implementation of high torque (power) designs, b) the use of increased screw rpm in conjunction with high torque for improved operating flexibility and productivity, and c) a breakthrough technology for feeding difficult to handle low bulk density materials. However, one area of twin-screw technology that has not evolved as much is screw elements geometry. Conveying elements and kneading blocks have remained essentially the same since the original Erdmenger design patents filed in the late 1940’s and early 1950’s. However, to take advantage of increased torque and power transmission capacity introduced in the newest generation of twin-screw compounding extruders, solids feed conveying and melt/mixing capacity in, for example, some highly filled compounds, had to be improved. Coperion has developed special involute screw and kneading elements with a new (Patent: EP 2 483 051 B1) cross section design to help achieve this objective. This paper will focus on the comparison of standard kneading blocks vs new involute kneading elements, specifically looking at some significant aspects related to performance.
11:30 am – 12:00 pm:
Resolving Feed Issues for Specialty Compounds in the TriVolution Compounder
Gonzalo Marulanda, B&P Littleford
During the last 5 years the TriVolution® compounder has proven to be an efficient compounder to surpass limitations found in a variety of specialty compounds. The increased rates on the machine have brought up machine limitations that where hidden, in particular when related to feed capacity and degassing capacity of the equipment. Working solutions are presented for case studies that address 3 specific issues: • Feeding of clay like materials which cannot be handled by an enlarged single screw feed such as PVC masterbatch or graphite filled processes. • Feeding of highly filled carbon black LLDPE masterbatches which can produce torque oscillation in the process due to difficulties in deaeration. • Feeding of processes with over 50% liquid composition and low/medium bulk density solids where deaeration and cleanliness of the yoke area are difficult. The solutions presented can be applied to a variety of other processes that offer similar difficulties.