Detecting onset of chain scission and crosslinking of gamma-ray irradiated elastomer surfaces using frictional force microscopy

TL;DR

This study demonstrates that frictional force microscopy can detect the onset of chain scission and crosslinking in gamma-ray irradiated elastomers by analyzing changes in surface friction properties.

Contribution

The paper introduces a novel application of AFM in frictional mode to identify chemical changes in elastomers caused by gamma-ray irradiation.

Findings

Friction increases initially with gamma-ray dose due to chain scission.

Friction decreases after a certain dose, indicating crosslinking.

Surface smoothness increases with irradiation dose.

Abstract

We report here that atomic force microscope (AFM) in frictional force mode can be used to detect onset of chain scission and crosslinking in polymeric and macromolecular samples upon irradiation. A systematic investigation to detect chain scission and crosslinking of two elastomers: (1) Ethylene-propylene-diene monomer rubber (EPDM) and (2) Fluorocarbon rubber (FKM) upon gamma-ray irradiation has been carried out using frictional force microscopy (FFM). From the AFM results we observed that both the elastomers show a systematic smoothening of its surfaces, as the gamma-ray dose rate increases. However, the frictional property studied using FFM of the sample surfaces show an initial increase and then a decrease as a function of dose rate. This behavior of increase in its frictional property has been attributed to the onset of chain scission and the subsequent decrease in friction has been attributed to the onset of crosslinking of the polymer chains. The evaluated qualitative and semi-quantitative changes observed in the overall frictional property as a function of gamma-ray dose rate for the two elastomers are presented in this paper.