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Testing flex resistance of rubber uppers

Outlining the use of SATRA’s STM 168 test machine in assessing the fitness for purpose of such materials.

Image © Tomaz Levstek |

Footwear incorporating rubber and polymeric uppers – particularly if designed for PPE applications – must be able to stand up to the rigours of daily use – including being flexed thousands of times without failing prematurely.

The SATRA STM 168 rubber materials flexing machine can hold up to 12 test specimens

The SATRA STM 168 rubber materials flexing machine has been designed to determine the flexing resistance of relevant components. The machine’s configuration allows a minimum of two and a maximum of 12 specimens to be evaluated simultaneously. Test pieces are clamped into the stations and are then flexed to form a crease that is an accurate representation of those formed during normal wear.

The machine is suitable for assessing rubber and polymeric uppers with a maximum thickness of 3 mm and a compression rating of up to 150 N. For specimens with a rating of over 100 N, a maximum of six specimens per test can be loaded into the machine.

Each machine is supplied with accessories necessary for use, is fully calibrated where applicable, and is issued with a calibration certificate. Tests conducted on this equipment are applicable to clause 6.5 of the 2011 and 2021 versions of EN ISO 20344, as referenced from clause 5.4.5 of EN ISO 20345 (2011 and 2022).

How can we help?

Please contact to purchase the SATRA STM 168 machine, or email for further information on its use to determine the flexing resistance of rubber and polymeric upper materials.

Publishing Data

This article was originally published on page 18 of the March 2023 issue of SATRA Bulletin.

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