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. 2022 Apr 4;12(7):1209.
doi: 10.3390/nano12071209.

Bromide and Chloride Ionic Liquids Applied to Enhance the Vulcanization and Performance of Natural Rubber Biocomposites Filled with Nanosized Silica

Magdalena Maciejewska  1 , Anna Sowińska-Baranowska  1
Affiliations

Bromide and Chloride Ionic Liquids Applied to Enhance the Vulcanization and Performance of Natural Rubber Biocomposites Filled with Nanosized Silica

Magdalena Maciejewska et al. Nanomaterials (Basel). .

Abstract

In this study, the possibility of using ionic liquids (ILs) as auxiliary substances improving the vulcanization and physicochemical properties of natural rubber (NR) biocomposites filled with nanosized silica was investigated. Hence, the influence of ILs with bromide and chloride anions and various cations, i.e., alkylimidazolium, alkylpyrrolidinium and alkylpiperidinium cation, on the curing characteristics and crosslink density of NR compounds was determined. Furthermore, the effect of nanosized silica and ILs on the functional properties of the obtained vulcanizates, including mechanical properties under static and dynamic conditions, hardness, thermal stability and resistance to thermo-oxidative aging, were explored. Applying nanosized silica improved the processing safety of NR compounds but significantly increased the optimal vulcanization time compared to the unfilled rubber. ILs significantly improved the cure characteristics of NR compounds by increasing the rate of vulcanization and the crosslink density of NR biocomposites. Consequently, the tensile strength and hardness of the vulcanizates significantly increased compared to that without ILs. Moreover, the use of nanosized silica and ILs had a favorable impact on the thermal stability of the vulcanizates and their resistance to prolonged thermo-oxidation.

Keywords: composites; ionic liquids; nanosized silica; natural rubber (NR); vulcanization.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
Structure of IL cations (R-alkyl substituent): (a) imidazolium; (b) pyrrolidinium; (c) piperidinium.
Figure 2
Figure 2
Differential scanning calorimetry (DSC) curves of the silica-filled NR compounds containing ILs with: (a) bromide anion; (b) chloride anion.
Figure 3
Figure 3
Mechanical loss factor (tan δ) curves versus temperature of the silica-filled NR vulcanizates containing ILs with: (a) bromide anion; (b) chloride anion.
Figure 4
Figure 4
Influence of thermo-oxidative aging on the crosslink density of the silica-filled NR vulcanizates containing ILs with: (a) bromide anion; (b) chloride anion.
Figure 5
Figure 5
Influence of thermo-oxidative aging on the stress at 300% relative elongation (Se300) of the silica-filled NR vulcanizates containing ILs with: (a) bromide anion; (b) chloride anion.
Figure 6
Figure 6
Influence of thermo-oxidative aging on the tensile strength (TS) of the silica-filled NR vulcanizates containing ILs with: (a) bromide anion; (b) chloride anion.
Figure 7
Figure 7
Influence of thermo-oxidative aging on the elongation at break (Eb) of the silica-filled NR vulcanizates containing ILs with: (a) bromide anion; (b) chloride anion.
Figure 8
Figure 8
Influence of thermo-oxidative aging on the hardness of the silica-filled NR vulcanizates containing ILs with: (a) bromide anion; (b) chloride anion.
Figure 9
Figure 9
Thermogravimetric (TG) and derivative thermogravimetric (DTG) curves of the silica-filled NR vulcanizates containing ILs with bromide anion: (a) TG curves; (b) DTG curves.
Figure 10
Figure 10
TG and DTG curves of the silica-filled NR vulcanizates containing ILs with chloride anion: (a) TG curves; (b) DTG curves.
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