Simulating Wet Paper Webs with Surrogate Materials

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Simulating Wet Paper Webs with Surrogate Materials

• April 27, 2005
• Matt Moore - Pulp Paper Student, GT BSIE
  05with Bart Carter - Texas AM BSME 03, GT
  MSME 05

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Todays Agenda

• Background
• Goals
• Procedure
• Results
• Summary

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Background

• Challenge to increase the bulk of printing and
  writing grade papers without sacrificing
  productivity
• Obstacle Modern papermakers use high-impulse
  pressing to increase throughput, which tends to
  over-densify the paper web

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Goals

• Explore technologies to control sheet expansion
  so that bulking occurs without disruption of the
  sheet
• Identify the properties of an ideal wet paper
  web that will encourage bulking when flash
  evaporation is employed

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Project Procedures
The Three Steps to Success!

• Research
• Communication
• Engineering

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Research

• Understood the problem and related literature
  many articles on possible materials
• Became familiar with current research
  technologies and procedures at the IPST

Project Procedures
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Communication

• Worked in lab with Bart Carter, Mechanical
  Engineering masters student
• Communicated with Dr. David Orloff, IPST

Project Procedures
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Engineering

• Created plan of action/project design
• Established deliverables for semester

Project Procedures
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How to Simulate Paper?

• Use readily available commercial products
• Artificially recreate the pressure changes and
  delamination within a paper web

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How to Simulate Paper?

• Viscoelastic systems (wet paper) can be
  approximated using elastic systems (as the
  viscoelastic equations dx/dt approaches 0, the
  elastic equations become appropriate)

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Material Research

• Conducted thickness, tensile, and peel tests on
  possible solutions
• 3M Craft Decorating Tape
• UL Black Electrical Tape
• Scotch Tape
• Foam Double Sided Tape
• Which one has properties most similar to a
  papers wet web?

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Tensile Testing
Use t-testing to investigate the tapes properties
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Tensile Test Results Example

• Computer records the displacement and load,
  researcher calculates stress and strain in the
  tape

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Choosing the Tapes

• Chose UL black electrical and Clear 3M
• Why?
• Both have uniquely good properties, as opposed to
  the other tapes

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Blister Tests to Simulate Paper ExpansionDuring
Impulse Drying

• Custom plates with holes in middle
• Pressure is controlled by researcher
• 4 plates have different hole sizes
• 1/8, 3/16, 1/4, and 3/8

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Blister Test What Happens?

• Air pressure pushes up on tape, creating a
  blister
• Researcher records the critical pressure where
  the blister deforms

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But air escapes when you pressurize a real paper
web
Can that be simulated in a lab?
Yes put perforations in the tape
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Creating a Perforation

• Use a hot soldering iron to create a perforation
  in the tape.
• The perforation must be approximately circular
• Perforations can be analyzed later with computer
  image analysis

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Results

• Looks like an inverse relationship between
  perforation radius and critical pressure
  (important later)

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Things to Consider

• Obviously the critical force needed to break the
  bond remains the same for both perforated and
  non-perforated tapes
• Higher critical pressure is needed for
  interfacial fracture of tape and plate
• Why?

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The Surface Area

• The perforation effectively reduces the surface
  area on the tape, so the pressurized air has less
  material to push against
• When critical force is reached, the tape
  delaminates as usual

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Final Thoughts

• Important to stay below the critical force in a
  paper web
• In the new process, the critical pressures and
  forces must be established then sheet damage
  can be controlled

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• Questions?