Evolution of Payne effect of silica-filled natural rubber in curing process

Vulcanisation is the key process for determining the final properties of elastomers due to the relationship between curing condition and viscoelastic behaviour. This study focuses on the variations in the dynamic behaviour of silica-filled natural rubber caused by crosslinking. The rubber samples with different degrees of curing (DOC) are prepared by thermal quenching during the crosslinking process. The strain sweep mode is used to study the Payne effect. The Kraus model is used to fit the test data. The relationship between the parameters of Kraus model and DOC is obtained at small strain (< 10%). The storage modulus at small strain amplitudes (usually < 0.01%) \( G^{\prime}_{ 0} \) is proportional to DOC; however, the storage modulus at large strain amplitudes \( G^{\prime}_{\infty } \) has small changes with DOC. The characteristic value of the strain amplitude \( \gamma_{\text{C}} \) shifts to large strain and the maximum loss modulus \( G^{\prime\prime}_{\text{m}} \) decreases with the increase of DOC. In addition, a deviation between Kraus model and experiment is observed when the strain is larger than 10%, and the loss modulus increases with the increase of strain amplitude. The deviation decreases when DOC increases. The mechanism for this deviation is discussed and the interaction between silica filler and rubber chain might be responsible for the observed deviation.