Common Physical Tests for Paper and Board
Depending on the grade and end use, different tests are performed to assess the quality of the paper or board being produced on a machine. Physical tests assess physical properties of the sheet, such as density, thickness, and different kinds of strength. Common physical tests include basis weight or grammage, moisture content, caliper, density, bulk, smoothness, porosity, stiffness, tensile strength, burst strength, tear strength, and folding endurance. This module will introduce some common physical tests, followed by a discussion on the importance of sample collection and conditioning, sheet formation, and moisture content.
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Learning Objectives
• List common criteria used to differentiate between paper and board grades • List some common paper and board grades • Describe basis weight testing, including principles and units • Describe moisture testing, including principles and units • Describe caliper, density and bulk testing, including principles and units • Describe smoothness testing, including principles and units • Describe porosity testing, including principles and units • Identify the organizations which have established standard testing, sampling, and conditioning procedures • Explain how sheet formation and moisture content can affect test results • Describe the importance of standardized sampling techniques and sample conditioning
Specs
| Course Level | Intermediate |
| Languages | English, Portuguese, Russian |
| Compatibility | Audio, Video |
| Based on: | Industry Standards and Best Practices |
Key Questions
Which standardized test methods are most commonly used in the U.S.?
The standards managed by the Technical Association of the Pulp and Paper Industry (TAPPI) are most common.
What is basis weight?
Basis weight refers to the weight in pounds of a ream of paper, where a ream is defined as 500 base size sheets. Different grades have different base sizes so basis weight cannot be directly compared across grades. Grammage (grams per square meter) is another way to express the weight per area, and values can be directly compared.
What is caliper?
Caliper is the thickness measurement of paper or board.
How is smoothness measured?
There are many different ways to measure smoothness (optical, friction, profile measurements, ink contact area) but air flow measurements are must commonly used.
Why is porosity measured?
Porosity determines the ability of a sheet to absorb ink or water, protect certain products, or act as a filter.
Sample Video Transcript
Porosity is a measure of the air resistance or air permeability of a sheet. This property effects the ability of a sheet to package and protect certain products, to absorb liquids like water and ink, or to act as a filter. Various instruments have been developed and are used, and most of them work in one of two ways. They either measure the length of time it takes for a specific volume of air at a controlled pressure to pass through a defined area the sheet. Or they measure the air flow rate through an area of the sheet while maintaining a constant pressure difference.
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