Mechanical Properties of Polybutadiene Rubber with Oxidation Defects: from Molecular Simulations

The mechanical properties of polybutadiene rubber were studied by atomistic molecular dynamics simulations to explore the influences of oxidation defects. Five typical systems were constructed to mimic the intermediate products during oxidation aging, considering oxidation reactions to generate hydroxyl groups, chain scission, and chain re-crosslinking. In comparison to predefined distribution, random distribution of defects increases energy dissipation and generally abates the mechanical strength and elasticity. Scission reactions can weaken the strain hardening behavior because more energy is dissipated owing to the interactions of the formed end groups. In a re-crosslinked chain, the local stress near the defects is much higher than at other positions along the chain. The additionally formed C-C bonds neither increase the mechanical strength nor enhance the elasticity. This stress concentration effect near the defects explains the microscopic mechanism of rubber fractures due to oxidation aging.

Automated summary

The mechanical properties of polybutadiene rubber were studied using atomistic molecular dynamics simulations. The presence of oxidation defects was found to have a negative impact on the rubber, leading to increased energy dissipation, decreased mechanical strength, and elasticity. Chain scission and re-crosslinking further weakened the mechanical properties, and stress concentration near the defects explained the microscopic mechanism of rubber fractures due to oxidation aging.