Abstract
Owing to the toxicity of polycyclic aromatic (PCA) oils, much attention has been paid to the replacement of PCA oils by other nontoxic oils. This paper reports comparative study of the effects of new vegetable oils, i.e., Moringa oil (MO) and Niger oil (NO), on rheological, physical and dynamic properties of silica–filled natural rubber composite (NRC), in comparison with petroleum–based naphthenic oil (NTO). The results reveal that MO and NO exhibit higher thermal stability and better processability than NTO. Cure characteristics of the rubber compounds are not significantly affected by the oil type. It is also found that the NRCs containing MO or NO have better tensile strength and lower dynamic energy loss than the NRCs containing NTO. This may be because both MO and NO improve filler dispersion to a greater extent than NTO as supported by storage modulus and scanning electron microscopy results. Consequently, the present study suggests that MO and NO could be used as the alternative non–toxic oils for NRC without any loss of the properties evaluated.
Highlights
Natural rubber composite (NRC) was prepared by mixing natural rubber (NR) with reinforcing filler such as silica and/or carbon black to improve physical properties and dynamic properties of NR
It can be seen that naphthenic oil (NTO) shows relatively poor thermal stability as proved by the lowest values of maximum decomposition rate temperature (Tmax) and onset temperature (Tonset) among the oils studied
The decomposition temperature range is broader than those of the vegetable oils. This might be due to the mixed composition of aromatic carbon, naphthenic carbon and paraffinic carbon in NTO
Summary
Natural rubber composite (NRC) was prepared by mixing natural rubber (NR) with reinforcing filler such as silica and/or carbon black to improve physical properties and dynamic properties of NR. The incorporation of high filler loading simultaneously requires the addition of plasticizers or oils such as petroleum–based oils to improve filler dispersion and reduce compound viscosity for easier processing. Plasticizers soften the compound by lubricating between rubber molecules and, promote filler incorporation and dispersion during mixing. The presence of plasticizer improves physical and dynamic properties of the NRC [1]. It has been reported that DAE oils contain relatively high content of polycyclic aromatic hydrocarbons (PAHs). Most research dealing with the utilization of green oils has been carried out in carbon black filled rubbers. Since there is a trend in the application of green and nontoxic oils, it is of interest to carry out research investigating the potential use of new vegetable oils for rubber processing applications
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