# Distinct stick-slip modes in adhesive polymer interfaces

## TL;DR

This study reveals multiple distinct stick-slip modes in adhesive polymer interfaces, including newly identified slip and separation pulses, and explores how these modes depend on sliding velocity, load, and adhesion.

## Contribution

It introduces two new wave types, slip pulse and separation pulse, expanding understanding of stick-slip phenomena beyond Schallamach waves in polymer interfaces.

## Key findings

- Identified and characterized slip pulse and separation pulse waves.
- Demonstrated mode transitions with changing velocity and load.
- Highlighted the role of adhesion in wave propagation.

## Abstract

Stick-slip, manifest as intermittent tangential motion between two solids, is a well-known friction instability that occurs in a number of natural and engineering systems. In the context of adhesive polymer interfaces, this phenomenon has often been solely associated with Schallamach waves, which are termed slow waves due to their low propagation speeds. We study the dynamics of a model polymer interface using coupled force measurements and high speed \emph{in situ} imaging, to explore the occurrence of stick-slip linked to other slow wave phenomena. Two new waves---slip pulse and separation pulse---both distinct from Schallamach waves, are described. The slip pulse is a sharp stress front that propagates in the same direction as the Schallamach wave, while the separation pulse involves local interface detachment and travels in the opposite direction. Transitions between these stick-slip modes are easily effected by changing the sliding velocity or normal load. The properties of these three waves, and their relation to stick-slip is elucidated. We also demonstrate the important role of adhesion in effecting wave propagation.