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Flex fatigue describes damage that develops when polyester fabric, coatings or laminated structures are bent repeatedly during use.

Tear strength measures how well fabric resists a small cut or damage from growing into a larger rip. This guide explains why strong polyester can still tear and what buyers should evaluate.

Knitted polyester stretches in multiple directions, so bursting methods can provide useful strength data. A mechanical ball-burst test drives a rounded probe into fabric, whereas diaphragm methods inflate a membrane beneath the clamped textile. The loading geometry and reported units differ; results cannot be converted by a universal factor.

Bulk density measures the apparent mass per occupied volume of a bed of PET chips, including void spaces between particles. Variation can affect volumetric handling, hopper levels and feeding consistency, particularly where equipment controls volume rather than mass. It is distinct from true polymer density and does not directly measure melt viscosity.

Heat setting can stabilize polyester knit dimensions, but polyester-elastane blends contain an elastic component whose recovery may deteriorate under unsuitable thermal and mechanical exposure. Temperature, dwell time, imposed width and fabric tension must be optimized together instead of selecting the highest available setting.

Synthetic microfibres may detach from textiles during laundering, surface abrasion and garment wear. Dry rubbing and washing impose different physical stresses and use different collection methods, so raw particle counts cannot be treated as the same release metric. Fabric surface structure, filament damage and wash protocols all influence results.

Pool disinfection exposes swimwear to active chlorine that can alter some textile colours. ISO 105-E03:2010, confirmed as current in 2026, specifies a controlled laboratory exposure. The chosen concentration and colour-change grading must be recorded before comparing swimwear materials.

Disperse dyes are supplied as fine dispersions for dyeing hydrophobic polyester. Zeta potential describes the electrical potential associated with the shear plane of a dispersed particle and can help screen electrostatic dispersion stability. It is not a replacement for testing particle-size distribution, dispersant chemistry or behaviour under actual dyehouse temperature.

Ribbon winding occurs when repeated winding paths stack filaments or yarn across similar zones of a package. The issue is linked to near-repeating traverse and spindle speed ratios and may produce dense bands that disturb unwinding during knitting or warping.