TY - BOOK

T1 - Advanced Filler Network Characterization in Rubber

AU - Syed Javaid Iqbal, Syed Imran Hussain

N1 - Doctoral thesis

PY - 2021

Y1 - 2021

N2 - The present work is aimed at introducing new characterization techniques in filled rubber compounds. Rubber fillers such as carbon black are often used to enhance the physical properties of rubber compounds. With a sufficient amount of carbon black, a percolated filler network is formed, spanning the volume of the rubber compound. This phenomenon not only significantly improves the mechanical material behaviour, but also introduces a more complex mechanical response. Further enhancement is possible with the addition of reinforcing resins such as Novolaks, phenol–formaldehyde resins with a formaldehyde-to-phenol molar ratio of less than one. Based on the systematic studies performed, the two reinforcing materials are observed to exhibit synergistic behaviour resulting from their physical and chemical interaction. The reinforcing resin modifies the activity of the filler surface creating a more compact filler network. This leads to a lower filler network percolation threshold as well as increasing the reinforcing behaviour. This conclusion was derived from various thermo-mechanical measurements such as temperature stress scanning relaxation (TSSR) and dynamic mechanical analysis (DMA). The findings were also validated with advanced microscopical techniques such as atomic force microscopy (AFM) and transmission electron microscopy (TEM). A direct consequence of the filler network is a strain dependent behaviour such as the dynamic and quasi-static strain dependent softening effects known as Payne and Mullins effects, respectively. Within the conventional dynamic mechanical analysis (DMA) of rubber compounds, the mechanical response signal is often assumed to be rheologically linear (sinusoidal function) since in Fourier space, the first harmonic is more pronounced than the subsequent higher harmonics. However, valuable information contained in the higher harmonics can be utilised in order to further characterise the compound properties. One such approach is the large amplitude oscillatory shear (LAOS) technique which analyses the harmonics as a function of large strain deformation. While several studies have contributed to the understanding of this strain dependent nonlinearity, less emphasis was placed on the nonlinearity of the frequency domain. Utilising a resonance-based high frequency DMA, nonlinearities in the frequency domain were established by the observation of the superharmonic resonance, for the first time in rubber technology. Two distinct nonlinearities were observed, polymer induced nonlinearity and filler induced nonlinearity. The new method based on the superharmonic resonance has been successfully applied to characterise the filler network through the evaluation of the microdispersion of carbon black and its interaction with reinforcing resins.

AB - The present work is aimed at introducing new characterization techniques in filled rubber compounds. Rubber fillers such as carbon black are often used to enhance the physical properties of rubber compounds. With a sufficient amount of carbon black, a percolated filler network is formed, spanning the volume of the rubber compound. This phenomenon not only significantly improves the mechanical material behaviour, but also introduces a more complex mechanical response. Further enhancement is possible with the addition of reinforcing resins such as Novolaks, phenol–formaldehyde resins with a formaldehyde-to-phenol molar ratio of less than one. Based on the systematic studies performed, the two reinforcing materials are observed to exhibit synergistic behaviour resulting from their physical and chemical interaction. The reinforcing resin modifies the activity of the filler surface creating a more compact filler network. This leads to a lower filler network percolation threshold as well as increasing the reinforcing behaviour. This conclusion was derived from various thermo-mechanical measurements such as temperature stress scanning relaxation (TSSR) and dynamic mechanical analysis (DMA). The findings were also validated with advanced microscopical techniques such as atomic force microscopy (AFM) and transmission electron microscopy (TEM). A direct consequence of the filler network is a strain dependent behaviour such as the dynamic and quasi-static strain dependent softening effects known as Payne and Mullins effects, respectively. Within the conventional dynamic mechanical analysis (DMA) of rubber compounds, the mechanical response signal is often assumed to be rheologically linear (sinusoidal function) since in Fourier space, the first harmonic is more pronounced than the subsequent higher harmonics. However, valuable information contained in the higher harmonics can be utilised in order to further characterise the compound properties. One such approach is the large amplitude oscillatory shear (LAOS) technique which analyses the harmonics as a function of large strain deformation. While several studies have contributed to the understanding of this strain dependent nonlinearity, less emphasis was placed on the nonlinearity of the frequency domain. Utilising a resonance-based high frequency DMA, nonlinearities in the frequency domain were established by the observation of the superharmonic resonance, for the first time in rubber technology. Two distinct nonlinearities were observed, polymer induced nonlinearity and filler induced nonlinearity. The new method based on the superharmonic resonance has been successfully applied to characterise the filler network through the evaluation of the microdispersion of carbon black and its interaction with reinforcing resins.

U2 - 10.15488/11028

DO - 10.15488/11028

M3 - Doctoral thesis

CY - Hannover

ER -