PAPER CURL, DIMENSIONAL STABILITY, 
EFFECTS OF SHRINKAGE AND XEROGRAPHIC PAPER ARTICLES FOR SALE

Available electronic articles:

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Loading Curve Variables vs CME (4 pages, .pdf, $10)

Loading curve data and CME were used to evaluate changes in things like bonding. Similar paper grades, such as copy paper products, seem to be produced with similar furnish and bonding qualities. The use of only the load-elongation curve seems to suffice to make an evaluation.

Effects of Paper Shrinkage (8 pages, .pdf, $10)

A model is discussed that increasing paper dimensions at the “reference moisture content” in manufacture or after manufacture (a) decreases coefficient of moisture expansion, (b) increases internal strain, (c) decreases strain to break and (d) increases tensile stiffness and tensile strength.  The converse is also true.  The effect of exposure to high humidity is also a subject of discussion.

Property Relationships (5 pages, .pdf, $10)

This article is a data supplement to Predicting Modulus and Properties. It essentially is a series of graphs of mechanical properties relationships.

Stiffness Index (5 pages, .pdf, $10)

This article discusses the evaluation of inherent paper stiffness by accounting for the effects of weight and caliper. It provides a way to know whether stiffness has been improved by changes we make in composition and manufacture. It avoids the need to make multiple runs with exactly the same basis weight, caliper and MD/CD stiffness ratio.

Residual Strain (8 pages, .pdf, $10)

Applied strain is used to describe residual strain. At a given RH, strain rate, stress relaxation time, and recovery time, residual strain is approximately a linear function of the applied strain. Test results do not vary much among machine made papers or test direction (MD or CD).

Predicting Modulus & Properties (18 pages, .pdf, $10)

This article discusses approaches to mea¬suring and predicting specific elastic modulus in a papermaking process and how it could be used to predict other paper properties.

Residual Strain From Heating (5 pages, .pdf, $10)

This presentation contains a number of graphs which show the effect of heating has on increasing residual strain significantly. Such data could relate to many papermaking and copying processes that use elevated temperatures.

Accelerating Creep by Heating (6 pages, .pdf, $10)

Accelerated creep from humidity cycling previously has been studied and is an established phenomenon but little or no reference has been made to heat accelerated creep. This report provides data on heat accelerated creep and puts forth an idea on how to analyze accelerated creep.

Tensile Loading Tutorial (8 pages, .pdf, $10)

It is essential to understand the principles involved in putting paper in tension. This articles is a short tutorial on the subject The article has the author's viewpoint in mind.

Curl From One Sided Drying (4 pages, .pdf, $10)

This article discusses curl observed using a HOT BEND or WARM OVEN test even though there is no top to bottom unbalanced fiber orientation within the sheet thickness. This example points out that any top vs. bottom differences found should be verified by moistening, drying and testing again.

Paper Curl Self-Tutorial (11 pages, .pdf, $10)

This is a self study tutorial using the format: (1) a question, (2) a response (sometimes with subheadings) and (3) additional study information. For example, “describe a simple experiment to show the concept of curl” is asked, followed by the description.

Curl Basics (5 pages, .pdf, FREE)

This article reviews how curl occurs when layers within a sheet expand or contract unevenly when they originally started out at equal length. Uneven shrinkage (or expansion) produces a bending moment because of uneven shear forces. A model of a sheet made up of two layers of equal thickness is discussed.

Fundamentals of Paper Curl (18 pages, .pdf, $10)

Topics of the article include: Showing concept of curl experimentally, What causes dimensional change, How curl forms (low RH, composition difference and fiber orientation between layers, internal strain), Effect of bending a sheet, Xerographic curl, Control ideas on furnish, wet end, size press, drying, and converting. There is a summary of fundamentals, and an appendix describing curl using calculations. 11 references.

Dimensional Stability (18 pages, .pdf, $10)

Measurements of CME (coefficient of moisture expansion) can be used to improve understanding of other properties such as elastic modulus and tensile strength. Topics include: Typical variations in CME, Model describing a concept, Some fundamentals in terms of an RMC (reference moisture), changes in moisture and tensile straining, Examples of fundamentals, Effect of tensile loading and internal strain, A mechanical method to measure CME suggestion, Controlling and minimizing CME, Procedure for characterizing CME, 34 references.

Aspects of Dimensional Stability (15 pages, .pdf, FREE)

This article contains information in condensed form about dimensional stability. It covers many aspects of the subject.

Measuring Dimensional Stability (2 pages, .pdf, $10)

Plate dried handsheets have zero shrinkage and practically the same CME (coefficient of moisture expansion). To determine the inherent CME of different pulps or furnishes it is necessary to use free dry handsheets. Each pulp will have a different shrinkage and CME.

Improving Curl Proposal (20 pages, .pdf, $10)

A reasonable and practical approaches to curl problems are used to determine the structural properties of paper and board as they relate to curl. In end use applications curl is often more than "moisture change" curl, but include the effects of internal strain and moisture, as seen in xerographic curl. The article is essentially directed toward paper manufacturing.curl, but include the effects of internal strain and moisture, as seen in xerographic curl.

Fuser Curl Mechanisms (8 pages, .pdf, $10)

Observations on fuser curl of 75gsm paper are explained in some detail. For example, why there is curl away from the print side at higher moisture content.

Fuser Curl At Higher Dwell Times (3 pages, .pdf, $10)

This article explores some of the curl results from increased heating times not normally used in a fuser. At very low dwell times, curl increases toward the fuser roll, at intermediate times, curl moves away from the fuser, and at still higher dwell times, curl moves toward the fuser again. This is essentially a third order response. Paper from different manufacturers also respond differently.

Curl Terminology (2 pages, .pdf, $10)

A way to describe curl in terms of it cylinder axis.

Hot Bend Curl Test (8 pages, .pdf, $10)

Paper strips are heated on a curved surface for several seconds. It is a good procedure for evaluating effect of wire/felt fiber orientation. The curved surface is a metal test block that is heated on a hotplate.

Warm Oven Curl Test (2 pages, .pdf, $10)

Sheets are suspended in 180-200 deg. F. for 1-2 minutes, removed and hanging curl is measured. Useful in evaluating effect of wire/felt fiber orientation.

Procedure to Characterize CME (2 pages, .pdf, $10)

Procedures used to determine dimensional stability can easily affect the results obtained. By following the same procedures each time results should be comparable. This is procedure for determining CME characteristics for any method used to make the measurements.

Curl Tests summarized (3 pages, .pdf, $10)

Short descriptions of some curl test methods besides the HOT BEND and WARM OVEN.

Xerographic Paper Self Tutorial (10 pages, .pdf, $10)

This tutorial can help you understand what properties xerographic papers need to perform well in copy machines, duplicators, and laser printers. The only difference between a laser printer and other machines is the image is placed on the photoreceptor by means of a laser

Xerographic Paper Properties (4 pages, .pdf, FREE)

This article summarizes properties and quality procedures important xerographic papers used in faster machines.

Basis Weight Conversion Factors (1 pages, .pdf, $10)

Converts from one basis weight system to another with convenient factors.

Inkjet Paper Testing (2 pages, .pdf, $10)

This article describes a method that uses liquids of differing surface tensions, usually mixtures of an alcohol and water. Other sizing test methods (such as KBB, Hercules and Cobb) use a single liquid, which is of limited value in comparison.

Static Problems (3 pages, .pdf, $10)

This article describes several things can contribute to a buildup of static. Knowing these, static can be reduced or eliminated.

Twenty Questions (Copy Paper) (2 pages, .pdf, $10)

Questions (and answers) that may be asked about copy paper and its performance

Imperial Weights and Sizes (3 pages, .pdf, FREE)

The name applied to those weights and measures appointed by statute to be used throughout the United Kingdom in 1836 and today is a term loosely applied to the same traditional sizes and linked weights of the pre-metrication era.

Loose Debris Evaluation Methods (1 pages, .pdf, $10)

The article provides short descriptions of six ways to quantify loose debris.

Curl From One Side Wetting (an overview) (5 pages, .pdf, $10)

Printing processes that use aqueous inks or offset that uses an aqueous fountain solution are subject to getting paper curl. The initial wetting can produce curl away from the printed side which later moves toward the printed side. Minimizing or eliminating these curls are often a complicated issue. This article discusses some of the aspects of this issue.

Twelve Steps to Curl (1 pages, .pdf, $10)

This article lists various ways we can get curl, with a brief description of an antidote.  For example, for too much drying/heating on one side, one can adjust top vs. bottom dryer heat.

Do the Decurl Tango (6 pages, .pdf, $10)

You can follow these steps in a reasonable order to determine what is happening on a paper machine that produce a paper's curl properties. Ability to obtain samples may be a shortcoming.

Paper Science Notes-Xerographic Paper (81 pages, .pdf, $20)

Information on significant properties such as smoothness, stiffness, static, moisture content, porosity, effect of preprinting, hard vs conformable fuser rollers, why voids occur in printing, effect of filler on input feeder performance, effect of composition, recycled paper, toner adhesion variables, paper problem analysis outline, curl,paper properties lists. It covers just about everything related to xerographic/laser printing. Originally published in hard copy form in 1994. Information contained therein should be useful to manufacturers of paper and laser printers.

The Seven Steps To Fixing Laser Curl Problems (2 pages, .pdf, $10)

If your laser printer or copier is curling the output paper, you can use these seven steps to help solve the problem.

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Charles (Chuck) GreenCharles (Chuck) Green, retired
Publisher, CPPN Electronic Library
Consulting: Curl, Xerographic Paper, Paper Physics
23 Maryvale Drive, Webster, NY 14580
585-265-9734

http://www.PaperCurl.com