Performance of Nano- and Microcalcium Carbonate in Uncrosslinked Natural Rubber Composites: New Results of Structure–Properties Relationship

Abstract

Calcium carbonate (CaCO3) is one of the most important inorganic powders and is widely used as filler in order to reduce costs in the rubber industry. Nanocalcium carbonate reduces costs and acts as a semireinforcing filler that improves the mechanical properties of rubber composites. The objective of this study was to investigate the effect of nano-CaCO3 (NCC) and micro-CaCO3 (MCC) on the properties of natural rubber composites, in particular, new results of structure–properties relationship. The effects of NCC/MCC on the properties of rubber composites, such as Mooney viscosity, bound rubber, Mullins effect, and Payne effect, were investigated. The result of the Mullins effect of rubber composites filled with NCC was in good agreement with the results of Mooney viscosity and bound rubber, with higher Mooney viscosity and bound rubber leading to higher stress to pull the rubber composites. The Payne effect showed that the value of different storage moduli (ΔG’) of rubber composites filled with 25 parts per hundred rubber (phr) NCC was the lowest due to weaker filler network, while the rubber supplemented with 100 phr NCC had more significant ΔG’ values with increase in strain. The results of rubber composites filled with MCC showed the same tendency as those of rubber composites filled with NCC. However, the effect of specific surface area of NCC on the properties of rubber composites was more pronounced than those of rubber composites filled with MCC. Finite element analysis of the mechanical property of rubber composites was in good agreement with the result from the experiment. The master curves of time–temperature superposition presented lower free volume in the composites for higher loading of filler, which would require more relaxation time of rubber molecules. This type of nanocalcium carbonate material can be applied to tailor the properties and processability of rubber products.

Effect of Fillers on the Recovery of Rubber Foam: From Theory to Applications

“…The DMA results presented in Table 5 reveal that the storage modulus in both the glassy state and rubbery state of the NRF with filler loading is higher than the control NRF. The addition of filler decreases the free volume within the foam, which causes more rigidity, resulting in a higher storage modulus in the glassy state [ 33 ]. The storage modulus in the rubbery state of the control NRF is lower than the NRF with filler loading.…”

“…Increasing filler loading increases the volume fraction of filler (∆ V f ), which causes a higher stress relaxation rate of rubber molecules where they require more time to unload the applied force [ 17 , 33 ]. This affects the degree of freedom of the rubber molecules to be more pronounced, i.e., when there is a greater number of interactions between the rubber chains and filler, the stress relaxation rate is increased, resulting in an increase in entropy [ 33 , 34 ]. Therefore, we can propose a model of the control NRF ( Figure 12 a) compared to the NRF with filler loading ( Figure 12 b).…”

Current challenges in thermodynamic aspects of rubber foam

“…In general, the storage modulus relates to the dynamic mechanical properties whereas tan δ relates to the dissipation energy of a material 46 , 47 . Rubber chains are freezing at the glassy plateau below the glass transition temperature, the foam sample with high NR content (control + 10% NR) represents a high storage modulus at the glassy plateau, indicating the lower free volume for high density samples 46 . However, the storage modulus of other two samples is quite similar.…”

Effect of SiO2 Particles on the Relaxation Dynamics of Epoxidized Natural Rubber (ENR) in the Melt State by Time-Resolved Mechanical Spectroscopy

“…The reinforcement of elastomers through the introduction of inorganic fillers is not only widely used for large scale manufacture of rubber products but also to formulate smart materials tailored to meet specific requirements in different fields of application [ 1 , 2 , 3 ]. The effective improvement of the material final properties achieved in elastomer-based composites depends on several factors, including the geometric feature dimensions of the reinforcing fillers [ 4 ], the extent of dispersion within the host matrix and their possible orientation [ 5 ], as well as their chemical nature, governing the possible establishment of strong polymer–filler interactions and, hence, the characteristics of the interfacial region [ 6 ].…”