Paper and paper board testing is important to the pulp and paper industry because of the demands placed upon it for a wide range of applications. In printing, for example, paper is handled from either cut sheets or rolls (webs) and the tensile strength and elongation properties must meet stringent customer requirements. We measure the tensile breaking strength of paper and board by testing paper strips, and measuring breaking load and stretch following the procedure in T 404. Additional requirements for testing of pulp hand sheets are detailed in standard T 220. These include evaluation of bursting strength, tensile breaking load, breaking length and tear factor.
Tensile Energy Absorption
Tensile energy absorption (TEA) of paper is defined as the area under the load-elongation curve (i.e., energy) related to the surface area of paper between the grips. This result is typically used to characterize the energy absorbing capacity of paper (see T 494), and use of a microprocessor or computer to calculate energy greatly simplifies data reduction.
The amount of stretch in paper and board is a critical measure of quality, since it is a necessary requirement for a sheet to fold well and resist local stress when used in packaging, corrugated board and tissues. We suggest that after initially clamping a sample in the upper grip, to apply a small stress to remove waviness. The sample is then pulled to rupture within a specified time, as detailed in T 457.
For products such as paper towels and bags, which are stressed after being moistened, many mills evaluate the web tensile properties from hand sheets, which can require special fixturing, as described in T 456.