Mark A. Spalding

Data Analysis of an Extrusion Experiment

The objective of this work is to demonstrate the usefulness of high-speed data acquisition in characterizing the extrusion process. This article analyzes the barrel pressures and motor current data acquired using a high-speed data acquisition system. Graphical analysis shows the relationship between screw design and screw speed.

Elimination of a Restriction at the Entrance of Barrier Flighted Extruder Screw Sections

Barrier flighted screws have been used for many years to increase rates, to eliminate flow surging due to solid bed break up, to lower melt temperatures, and to minimize temperature fluctuations in the extrudate. For most barrier screws, the melt separation flight starts at a location where the melt pool starts to accumulate. However, if the start of melting occurs downstream from this point, compacted solid polymer can be wedged into the start of the barrier entrance. For some barrier screws, this wedging can lead to a restriction in the flow, decreasing the rate of extrusion by up to 30%. This paper will discuss the phenomenon and show how to eliminate the problem.

Computer Automation of Two Oxygen Permeation Instruments

Oxygen permeation measurements are critical to the research and de velopment of food-packaging containers and films Such measurements must be ac curate, reliable, and fast to keep pace with rapidly changing markets and products This paper describes the construction and automated operation of a pair of OX- TRAN 1 10/50 oxygen permeation instruments using a personal computer and a CAMILE2 data acquisition and control system. The new automated system requires less operator attention, performs monitored permeation measurements 24 hours per day, and permits two different permeation experiments to be performed simultane ously. For permeation measurements of films, the automated system has increased the testing productivity of the instruments by 2.5 times.

Selecting Equipment To Minimize Production Costs and Maximize Profitability

Specifying and installing the proper equipment for a process is the key to minimizing the long-term cost of producing products. But often the objective to purchasing equipment is to minimize the initial capital cost. Minimizing this initial purchase cost, however, may require the purchaser to add costly modifications to the line after installation, creating higher operating costs, lengthy troubleshooting, and a delay to market entry. Principles and strategies are presented here that show how to avoid this mistake, and case studies are provided as learning tools.

Use of process data obtained from a data acquisition system for optimizing and debugging extrusion processes

Debugging and optimization of extruder performances are often complicated by the lack of transient process data. Most production extruders have excellent process controllers, but they generally lack data acquisition systems. Because of these equipment limitations, all transient, unsteady-state data for a process are unavailable for analysis. Highlighted in this article are four case studies where transient data were collected and used (1) for the diagnosis and elimination of extrusion instabilities; (2) to show differences between competing resin processability; and (3) in extrusion research. In all cases, a portable data acquisition system was temporarily connected to the extruder control panel and was used to collect transient process data. For extruder instability problems, the data collected were used to help diagnose and eliminate the problems quickly, bringing the extrusion lines up to standard production in the shortest possible time, minimizing costly recycle, and maximizing the profits for the processors.

Troubleshooting and mitigating gels in polyethylene film products

The term “gel” refers to any small defect that distorts a film product. Eliminating gel defects from extruded polyethylene film products can be difficult, time consuming, and expensive due to the problems complexity and the off-specification product produced. This paper discusses how to: identify gel types, common root causes, and technical solutions for mitigating gels in film products produced using single-screw extruders.

The incumbent resin effect for single-screw extrusion of polyethylene resins: The effect of resin changeover on gels in the product

Innovative polyethylene films are constantly being developed by switching the existing or incumbent resin with a new or challenger resin. If the extrusion equipment is designed properly, the film with the challenger resin will be acceptable for further testing and marketing. However, if the extrusion equipment is not designed properly, old degraded material from the incumbent resin will be pushed out of the extruder by the challenger resin, contaminating the test film. In many cases, the challenger resin is incorrectly blamed for the gels. This paper describes the incumbent resin effect, presents a case study, and provides technical solutions.

High-Modulus Low-Cost Carbon Fibers from Polyethylene Enabled by Boron Catalyzed Graphitization

Currently, carbon fibers (CFs) from the solution spinning, air oxidation, and carbonization of polyacrylonitrile impose a lower price limit of ≈

Alkylation of isobutane with C4 olefins. 1. First-step reactions using sulfuric acid catalyst

10 per lb, limiting the growth in industrial and automotive markets. Polyethylene is a promising precursor to enable a high-volume industrial grade CF as it is low cost, melt spinnable and has high carbon content. However, sulfonated polyethylene (SPE)-derived CFs have thus far fallen short of the 200 GPa tensile modulus threshold for industrial applicability. Here, a graphitization process is presented catalyzed by the addition of boron that produces carbon fiber with >400 GPa tensile modulus at 2400 °C. Wide angle X-ray diffraction collected during carbonization reveals that the presence of boron reduces the onset of graphitization by nearly 400 °C, beginning around 1200 °C. The B-doped SPE-CFs herein attain 200 GPa tensile modulus and 2.4 GPa tensile strength at the practical carbonization temperature of 1800 °C.