A Communication from the PLACE Div. of TAPPI

Providing practical information to the converting and packaging industries…

EXECUTIVE SUMMAR
Improving Productivity With Automated Slitter Positioning

by Bryan Zimmerman, Tidland Corp.

APPLICATION: Significant opportunities exist to improve productivity through the use of automated slitter positioning technology.

Productivity is a measure of the outputs of a system that are possible for a given set of inputs. Automated slitter positioning technology has use to achieve significant improvements in production productivity. While a wide variety of automated slitting systems are available, the important characteristics that positively impact productivity can be analyzed in isolation from any particular automated slitting system design.

Automated slitter positioning technology offers many opportunities to improve productivity. Fast and accurate slitter setups increase production capability and flexibility. Automation improves product consistency, minimizes tool wear, and reduces worker exposure to production hazards. Automation also allows synergistic integration of the automated slitting system with other management and production systems.

The number of different types and configurations of automated slitting systems is huge. Available variations in size, slit count, drive mechanism, minimum slit width, controls, and many other factors enable the automated slitting system to be configured to meet the specific needs of the production environment. This paper discusses common configurations and feature sets. It also focuses on commonly achievable productivity improvements that are possible through the use of automated slitting system technology.

Achieving the benefits of automated slitter positioning depends upon installing slitting system hardware and controls that are appropriate for the application. Many types of automated slitting systems are available and numerous factors must be considered when choosing an automated slitting system to achieve maximum productivity improvements. Understanding the capabilities and applying technology intelligently is the best way to turn the potential of automated slitter positioning into a productive reality.



EXECUTIVE SUMMAR
Polymeric Nanocomposites Enabled By Controlled Architecture Materials

by James M. Nelson, 3M Dyneon LLC, et al.

APPLICATION: Controlled architecture materials (CAM) are specialty additives for the formation of polymer nanocomposites under melt-processing conditions. They provide interesting exfoliation solutions for clays of differing hydrophobicity in various polymers.

Polymer nanocomposites materials based on layered-silicate (i.e. montmorillonite clay) materials have been a topic of considerable recent activity. Results of these studies have shown that nanocomposite technology is useful to improve film barrier properties, increase modulus, increase heat distortion temperature, and improve flame retardancy. Good dispersion of nanoclays in the polymer matrix and a strong interface between the two phases are essential to achieve these improvements. Efficient dispersion of the clays is often hindered by the natural incompatibility between the hydrophilic clay and the hydrophobic matrices (especially polyolefins). In addition, the clay layers tend to bond strongly together making the dispersion of the clay into the polymer matrix more difficult.

From an applications standpoint, considerable interest lies in the examination of clay-filled polyolefins as potential replacements for engineering polymers. A shortcoming is its lower relative. Previous approaches have employed substantial loadings or larger sized fillers such as talc or glass fibers that can detrimentally impact composite processability, recycleability, ductility, and surface quality.

The interest in the use of nanocomposites in automotive applications involves the use of dispersed clays in rubber-modified thermoplastics to produce reinforced automotive exterior and interior parts where an optimum balance of stiffness and toughness is essential.

The exfoliation process can be performed in a number of ways. Conventional exfoliation methods include polymerizing a monomer around a pre-dispersed clay, dissolving a polymer and a clay in a mutually inclusive solvent, or using additives to aid in the exfoliation during melt compounding extrusion processes. A melt processing approach to nanocomposite formation is advantageous for environmental, breadth of product design, and lower switching cost arguments.



EXECUTIVE SUMMAR
Benefits Of New Technology Ionizers For Web Handling

by Scott Shelton, Simco Industrial Static Control

APPLICATION: Ionizers are critical to web handling processes because they control electrostatic charges to enhance product quality and throughput.

Ionizers in the form of static neutralizing bars have had common use to neutralize static charges on web and sheet materials since the 1930s. The devices mount within the process machine in proximity to the moving material. As the material passes by the neutralizing bar, the surface charges are reduced or eliminated at that point in the process.

The static neutralizing bar produces both negative and positive charged gas molecules called air ions. These are free ions that are attracted to the charged surface. Positive fields attract the negative ions and negative fields attract the positive ions until the surface is in electrical equilibrium. Periodic cleaning and evaluation of the static neutralizing bar is necessary to ensure it is operational and performing optimally. Traditional systems require some degree of knowledge of how they operate so they can be properly evaluated. Additional instrumentation is also necessary to perform the task. The new technology ionizers available today incorporate self-diagnosis circuitry with indicators that display system status and performance. Coupled with much higher performance, these features provide a considerable benefit to a web handling operation.

Various forms of energy generate air ions. They include electrical AC and DC, radioactive, and passive (induction). This paper focuses on electrically powered ionizers. Electrostatic charges that accumulate on the surface of a web can have serious effects on product quality. This is especially apparent when the material is to be printed or coated. The electric fields associated with the surface charges can influence airborne particulate and attract them to the surface. Particles in the environment may also be charged due to triboelectric charging. Some may be positive, some negative, and some neutral. The electric field from the charged web can attract particles of the opposite polarity should they enter into the range of the field. Neutral particles entering the field may become polarized and can also be attracted to the web. Either case results in particulate contamination of the surface adversely affecting the quality of the coated or printed product. Surface charges on the web can also result in uneven coatings and poor print quality.

The newer technology static neutralizing systems available in today’s market offer many distinct benefits to the end user in web handling applications. The neutralizing efficiency far surpasses that of the traditional ionizers while still offering the shockless features. This provides more efficient neutralizing of higher charges at higher web speeds and at greater distances from the web. The feedback of operational parameters of these systems proves invaluable to an operator. At a glance, the operator is assured the bar is operational, can view its relative efficiency level, and knows if it requires cleaning. These systems are essential to ensure product quality and safety in the manufacturing environment with the least amount of personnel time involvement.



EXECUTIVE SUMMAR
The Effect Of Orientation On MD Tear Of HMW-HDPE Films

by H. Mavridis, A. Bafna, and J. Merrick-Mack, Lyondell Chemical Co.

APPLICATION: Approaches to improved film MD tear require balance against their effect on film impact strength and tensile properties.

The specific machine direction (MD) tear strength (MD tear per thickness) of HMW-HDPE films generally decreases with decreasing film thickness. This is probably the result of increasing orientation as film thickness decreases. Producing thin films of enhanced MD tear strength should therefore be possible if the orientation in the film were somehow reduced. This study used a coextrusion approach to produce thin HMW-HDPE films fabricated under conditions of low draw-down and orientation. The coextrusion approach resulted in a two to four-fold increase in MD tear. Morphology characterization of the films via x-ray and atomic force microscopy (AFM) does show reduced orientation.

The film properties of HMW-HDPE films—especially Elmendorf tear strength and impact strength—have a strong dependence on film fabrication conditions. Other workers showed the dependence of several film properties such as MD tear, TD tear, impact strength, and tensile strength on critical blown film fabrication variables such as frost line height and blow-up ratio for HMW-HDPE. Newer work has focused on the morphology of HMW-HDPE films and its relationship to the observed properties.

The effects of thickness on the film properties of HMW-HDPE can be complex. Elmendorf tear strength is typically normalized for thickness by dividing the tear strength value by the film thickness. This has use for comparing the tear strength of films of different thicknesses. The specific MD tear decreases dramatically for decreasing thickness.

Higher orientation is imparted in a film for smaller thickness and thus the specific MD tear decreases. This reasoning is inferential because we do not have films of small thickness and low orientation to prove the point. In other words, we have thick films of low orientation and high MD tear and thin films of high orientation and low MD tear. The objective of this work is to somehow produce thin films of low orientation and compare them with “ordinary” thin and thick films.



For information about the PLACE Division of TAPPI, access the TAPPI web page at tappi.org. To obtain the complete papers whose expanded summaries appear in this section, go to the TAPPI web site at tappi.org., then click on "the PLACE" in the section designated Journals.


Telephone inquiries are welcome at the TAPPI Service Line by calling 800/332-8686 in the United States, 800/446-9431 in Canada, or 770/446-1400 in other countries. Send FAX to 770/446-6947. Address mail to TAPPI, 15 Technology Parkway South, Norcross, GA, 30092.

Submit manuscripts for publication to dbentley@tappi.org. Obtain information about the PLACE Division from tappi.org.


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