Paper and Board Strength Tests
Paper and board products are widely used in our daily lives. Sheet strength is critical to the performance of most grades, not only in their end uses, but also in converting and finishing operations. Because different paper and board grades are subjected to different stresses and strains, several different strength tests have been developed. The most common are tensile, burst, stiffness, tear, internal bond, and ring crush. This module will discuss common strength tests for paper and board grades, as well as sheet parameters that affect strength properties.
Request a demoCourse Details
Learning Objectives
• Identify the organization whose standardized testing procedures are followed most often in the U.S. • Identify important factors to consider during sample collection and sample conditioning • Explain why paper and board sheet strength properties are important • Explain why it is important to keep track of the machine direction during sampling and testing • Describe tensile, TEA, stretch, burst, stiffness, tear, internal bond, ring crush, and SCT testing, including principles and units
Specs
| Course Level | Intermediate |
| Languages | English, Portuguese |
| Compatibility | Audio, Video |
| Based on: | Industry Standards and Best Practices |
Key Questions
Why is sample conditioning important?
Water interferes with fiber bonding so the moisture content of the sheet affects many paper properties, especially strength properties. Temperature also affects results because air can hold different amounts of water vapor at different temperatures.
What factors can impact strength properties?
Paper strength depends on the strength and arrangement of individual fibers, the number and distribution of fiber-to-fiber bonds, and additives. Fiber strength can be affected by pulping, bleaching, and refining and bonding can be impacted by refining and we pressing.
Why is it important to keep track of the machine direction for a sample?
MD and CD strength properties can be significantly different. Many grades have specific requirements. For example a high MD strength might be required for converting.
What are the major strength tests?
The most common tests are tensile, burst, stiffness, tear, internal bond, and ring crush.
What is zero-span tensile?
Zero-span tensile is a modification of the tensile test that eliminates the gap between clamps. Zero-span tries to measure the fiber strength instead of the sheet strength and is considered the maximum tensile strength of the sheet.
Sample Video Transcript
The tear test measures the force that is required to continue tearing a sample from an initial cut through a standard sample width. It is expressed in units of grams or millinewtons. There are several available test methods, but the most common uses the Elmendorf Tear Tester. With this tester, a sample strip is clamped in two places, and a slit is cut between them. A pendulum supporting one clamp is released, and it swings away from the other clamp, registering the force required to continue the tear as Elmendorf units on an arc scale. The tearing force can be calculated by multiplying the Elmendorf units by a factor. Fiber orientation greatly affects tearing resistance. So it is important to test and report CD and MD results separately.
Course Applies To
Demos + Pricing
Learn more about our courses, get pricing, and see our platform.
