Tensile Strain Measurement in Recycled Paperboard Grades
Recycled paperboard strain measurement requires direct optical extensometry under ISO 1924-3 to isolate true sheet elongation from clamp slippage.
Atmospheric Conditioning
Conditioning Protocol
Controlled environment protocols ensure that cellulose-based materials reach a stable state before physical testing begins. Standardized atmospheric conditioning involves exposing paper or board samples to specific temperature and humidity levels for a set duration, typically 23 degrees Celsius and 50 percent relative humidity under ISO 187. This process allows the hygroscopic fibres to reach moisture equilibrium with the surrounding air.
Variations in water content notably alter the mechanical properties of a sheet.
Response Characteristic
Fibre swelling or contraction resulting from moisture exchange dictates the repeatability of laboratory measurements. Because atmospheric conditioning stabilizes the physical dimensions of the specimen, it prevents discrepancies in tensile strength and stiffness results. A sample tested immediately after removal from a high-humidity storage area will show higher extensibility and lower burst resistance than one properly prepared.
Standard procedures often require pre-conditioning at low humidity to eliminate hysteresis effects, which ensures that the final equilibrium state is always approached from the dry side. This specific sequence of environmental exposure reduces the variability inherent in the cellulose structure.
Plant Requirement
Plant conditions during the printing or corrugating stages determine how well a substrate performs on high-speed equipment. When atmospheric conditioning is neglected during material storage, the resulting moisture gradients lead to curl, waviness or tight edges. These defects interfere with suction feeds and plate registration.
Dimensional stability remains the primary goal for any facility handling sensitive paper grades.