Fretting Behavior of Thermoplastic Polyurethanes

Chao Wang,Michael Berer,Thomas Schwarz,Florian Grün,Andreas Hausberger,Gerald Pinter

doi:10.3390/lubricants7090073

Chao Wang, Michael Berer + Show 4 more

Open Access

https://doi.org/10.3390/lubricants7090073

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Abstract

Fretting tests were conducted with five different thermoplastic polyurethanes against a steel ball. Their fretting behaviors were investigated under various test parameters, such as normal load and displacement amplitude. In order to test the sliding performances, tribological tests were conducted using a ring-on-disc setup. The results show that their fretting behaviors can be related to the dynamic mechanical properties, which were characterized by dynamic mechanical analysis (DMA). The three fretting regimes were identified by means of hysteresis and wear scar analysis. In addition, investigations were carried out until the transition regimes occurred. Different wear processes were revealed for each of the three regimes. Differences were identified using dissipated energy. The profiles of wear scars and the counterparts were analyzed using a microscope. The coefficient of friction was calculated separately for the partial slip and gross slip regimes. In the mixed fretting regime, the coefficient of friction is almost at the same level among the five materials. In the partial slip regime, however, it can be distinguished. Temperature measurements were conducted on the counterparts during the tests. Overall, the material that showed the best tribological properties also performed the best in the fretting tests.

Highlights

Thermoplastic polyurethane elastomers (TPUs) are multiblock copolymers with hard and soft segments
Our prior study defined the method of investigation for the fretting behavior of polymeric Our prior study defined the method of investigation for the fretting behavior of polymeric materials [12]
It is notable that the fretting behavior of TPUs was related to the dynamic mechanical materials [12]

Summary

Introduction

Thermoplastic polyurethane elastomers (TPUs) are multiblock copolymers with hard and soft segments. Due to their unique structure, they have high tensile strength and the ability to be processed with thermoplastic methods. These unique properties make TPUs useful in a great variety of applications. TPUs can be applied as a substitution for vulcanized rubber, for example [1]. Due to their excellent mechanical properties, seals made of TPU can maintain an effective dynamic sealing geometry at high pressure for extended periods [2]. Qi researched the stress–strain behavior of TPUs and a constitutive model was introduced, which can reflect their nonlinear, time-dependent, and softening behaviors [4]

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