Kyei-Manu William Amoako, Herd Charles R, Chowdhury Mahatab, Busfield James J C, Tunnicliffe Lewis B
School of Engineering and Materials Science, Queen Mary University of London, London E1 4NS, UK.
Birla Carbon, Marietta, GA 30062, USA.
Polymers (Basel). 2022 Mar 16;14(6):1194. doi: 10.3390/polym14061194.
The influence of carbon black (CB) structure and surface area on key rubber properties such as monotonic stress-strain, cyclic stress-strain, and dynamic mechanical behaviors are investigated in this paper. Natural rubber compounds containing eight different CBs were examined at equivalent particulate volume fractions. The CBs varied in their surface area and structure properties according to a wide experimental design space, allowing robust correlations to the experimental data sets to be extracted. Carbon black structure plays a dominant role in defining the monotonic stress-strain properties (e.g., secant moduli) of the compounds. In line with the previous literature, this is primarily due to strain amplification and occluded rubber mechanisms. For cyclic stress-strain properties, which include the Mullins effect and cyclic softening, the observed mechanical hysteresis is strongly correlated with carbon black structure, which implies that hysteretic energy dissipation at medium to large strain values is isolated in the rubber matrix and arises due to matrix overstrain effects. Under small to medium dynamic strain conditions, classical strain dependence of viscoelastic moduli is observed (the Payne effect), the magnitude of which varies dramatically and systematically depending on the colloidal properties of the CB. At low strain amplitudes, both CB structure and surface area are positively correlated to the complex moduli. Beyond ~2% strain amplitude the effect of surface area vanishes, while structure plays an increasing and eventually dominant role in defining the complex modulus. This transition in colloidal correlations reflects the transition in stiffening mechanisms from flexing of rigid percolated particle networks at low strains to strain amplification at medium to high strains. By rescaling the dynamic mechanical data sets to peak dynamic stress and peak strain energy density, the influence of CB colloidal properties on compound hysteresis under strain, stress, and strain energy density control can be estimated. This has considerable significance for materials selection in rubber product development.
本文研究了炭黑（CB）结构和表面积对关键橡胶性能（如单调应力应变、循环应力应变和动态力学行为）的影响。在等效颗粒体积分数下，对含有八种不同炭黑的天然橡胶复合材料进行了研究。根据广泛的实验设计空间，这些炭黑的表面积和结构性能各不相同，从而能够提取与实验数据集的稳健相关性。炭黑结构在定义复合材料的单调应力应变性能（如割线模量）方面起主导作用。与先前的文献一致，这主要是由于应变放大和封闭橡胶机制。对于包括穆林斯效应和循环软化在内的循环应力应变性能，观察到的机械滞后与炭黑结构密切相关，这意味着中等到大应变值下的滞后能量耗散在橡胶基体中孤立存在，并且是由于基体过度应变效应引起的。在小到中等动态应变条件下，观察到粘弹性模量的经典应变依赖性（佩恩效应），其大小根据炭黑的胶体性质显著且系统地变化。在低应变幅度下，炭黑结构和表面积均与复数模量呈正相关。超过约2%的应变幅度，表面积的影响消失，而结构在定义复数模量方面发挥着越来越大且最终占主导地位的作用。这种胶体相关性的转变反映了强化机制从低应变下刚性渗流颗粒网络的弯曲到中高应变下应变放大的转变。通过将动态力学数据集重新缩放到峰值动态应力和峰值应变能密度，可以估计炭黑胶体性质对复合材料在应变、应力和应变能密度控制下的滞后的影响。这对橡胶产品开发中的材料选择具有重要意义。
