Effect of Controlled Chain-Scission Damage on Viscoelasticity in Double Network Elastomers

Background The relationship between molecular-scale chain scission and bulk viscoelasticity in soft polymer networks remains incompletely understood, particularly in multiple network elastomers, where energy dissipation arises from the interaction between irreversible chain-scission damage and reversible time-dependent mechanics. Objective This study aims to elucidate how cumulative, progressive chain-scission damage influences bulk viscoelasticity in double network elastomers through both experiments and constitutive modeling. Methods A non-swelling, platinum-cured silicone double network elastomer was synthesized and served as a model system to investigate damage-induced effects on viscoelasticity. Cyclic tensile loading was applied to introduce systematically controlled chain-scission damage. The changes in viscoelastic properties were characterized via stress relaxation tests and dynamic mechanical analysis. A constitutive model coupling hyperelasticity with damage-induced viscosity through stretch-mediated chain-scission kinetics and chain-length-dependent disentanglement kinetics was established to describe the observed damage-viscosity coupling. Results Experiments revealed that cumulative bond breaking in the double network elastomer contributes not only to Mullins-type softening but also to measurable increases in apparent relaxation time and viscoelastic dissipation rate. The proposed model successfully reproduced damage-related effects, including both irreversible primary hysteresis caused by network damage and narrower, persistent secondary hysteresis due to damage-induced viscoelastic dissipation. Conclusion Although the damage-induced viscoelastic dissipation was small compared to the energy directly dissipated by bond breaking, our results provide direct experimental evidence and quantification that internal molecular damage can modulate bulk time-dependent constitutive behavior. These findings lay the foundation for predictive modeling of dissipative mechanics mediated by damage–viscoelasticity coupling in complex multiple network elastomers.