Standard Method
Tensile testing methodologies evaluate the non-recoverable elongation of a textile specimen after it undergoes repeated cyclic loading to a specified strain level. One of the most common procedures for this measurement is permanent set din 53835, which defines the test parameters for elastic knitted and woven fabrics. The method determines the structural stability of fabrics intended for stretch garments.
Beyond these elastic materials, other standard test methods are more appropriate.
Elongation Behaviour
Fibers subjected to repeated stretching do not return fully to their original dimensions due to internal molecular slippage. This permanent deformation represents the permanent set, expressed as a percentage of the original specimen length. The testing procedure specifies the number of cycles, the extension limits, and the recovery time before the final measurement is taken.
If the recovery time is too short, the measured set will be artificially high. This occurs because the polymer chains have not had enough time to relax to their lowest energy state. Understanding this behavior helps garment designers choose fabrics that will not bag or lose their shape during wear.
Cyclic Testing
Standardized testing machines use pneumatic grips to hold the fabric specimen while applying cyclic tension. The force and extension are recorded continuously to plot the hysteresis loop of the fabric. This loop reveals the energy loss and elastic recovery efficiency of the textile structure.
Analyzing these curves allows manufacturers to verify the performance of elastane blends.
Deformation Analysis
High values of permanent set indicate that the garment will quickly lose its fit and appearance. Conversely, low values guarantee that the product will maintain its shape after multiple wash and wear cycles. Adhering to the standard ensures consistent product quality in stretch apparel.
