There are various methods by which to evaluate zipper strength. The basic strength can be determined based on the results of the following inspection methods, from which overall strength appropriate for respective uses can be judged.（Based on JIS-S3015 and ASTM D2061）
Chain crosswise strength (per 2.5cm):
An engaged zipper chain is pulled crosswise as shown at a constant speed.
Top stop holding strength：
The lower part of an engaged zipper is held securely, then the slider pulled to the top is pulled further up.
Bottom stop holding strength:
The slider is pulled down to the bottom stop, and each side of the chain is pulled outwards in opposite directions.
Separating unit crosswise strength:
The slider lock is engaged in the middle of a chain, then each side of the chain is pulled outwards in opposite directions.
Slider lock strength:
The slider lock is engaged in the middle of a chain, then each side of the chain is pulled outwards in opposite directions.
Slider tab pull off strength (90 degree):
Tension force is applied to both the pull-tab and the bottom of the body of an assembled slider.
In addition to the 90°angle shown, a 45°angle is also tested.
(Tensile Testing Machine Speed: 100 mm/min)
