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. 2021 Jul 7;14(14):3804.
doi: 10.3390/ma14143804.

Zinc Complexes with 1,3-Diketones as Activators for Sulfur Vulcanization of Styrene-Butadiene Elastomer Filled with Carbon Black

Magdalena Maciejewska  1 , Anna Sowińska  1 , Agata Grocholewicz  1
Affiliations

Zinc Complexes with 1,3-Diketones as Activators for Sulfur Vulcanization of Styrene-Butadiene Elastomer Filled with Carbon Black

Magdalena Maciejewska et al. Materials (Basel). .

Abstract

Zinc oxide nanoparticles (N-ZnO) and zinc complexes with 1,3-diketones of different structures were applied instead of microsized zinc oxide (M-ZnO) to activate the sulfur vulcanization of styrene-butadiene rubber (SBR). The influence of vulcanization activators on the cure characteristics of rubber compounds, as well as crosslink density and functional properties of SBR vulcanizates, such as tensile properties, hardness, damping behavior, thermal stability and resistance to thermo-oxidative aging was explored. Applying N-ZnO allowed to reduce the content of zinc by 40% compared to M-ZnO without detrimental influence on the cure characteristic and performance of SBR composites. The activity of zinc complexes in vulcanization seems to strongly depend on their structure, i.e., availability of zinc to react with curatives. The lower the steric hindrance of the substituents and thus the better the availability of zinc ions, the greater was the activity of the zinc complex and consequently the higher the crosslink density of the vulcanizates. Zinc complexes had no detrimental effect on the time and temperature of SBR vulcanization. Despite lower crosslink density, most vulcanizates with zinc complexes demonstrated similar or improved functional properties in comparison with SBR containing M-ZnO. Most importantly, zinc complexes allowed the content of zinc in SBR compounds to be reduced by approximately 90% compared to M-ZnO.

Keywords: 1,3-diketones; cure characteristics; mechanical properties; vulcanization; zinc complexes.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
Structure of zinc 1-(4′-methoxyphenyl)-3-phenylpropane-1,3-dione (MBPP-Zn).
Figure 2
Figure 2
Structure of zinc 1-(4′-t-butylphenyl)-3-(4″-methoxyphenyl)propane-1,3-dione (tBuMBPP-Zn).
Figure 3
Figure 3
Structure of zinc 1,3-bis-(4′methoxyphenyl)propane-1,3-dione (MMBPP-Zn).
Figure 4
Figure 4
Structure of zinc 1-heptyl-3-phenylpropane-1,3-dione (HeBPP-Zn).
Figure 5
Figure 5
Differential Scanning Calorimetry (DSC) curves of SBR compounds containing M-ZnO and N-ZnO as activators.
Figure 6
Figure 6
DSC curves of SBR compounds containing zinc complexes with 1,3-diketones as activators.
Figure 7
Figure 7
Fourier Transform Infrared (FTIR) spectra of: (a) pure SBR rubber; (b) SBR vulcanizates containing ZnO and zinc complexes with 1,3-diketones as activators.
Figure 8
Figure 8
Scanning electron microscopy (SEM) image and Energy-dispersive X-ray spectroscopy (EDS) maps for SBR vulcanizate containing M-ZnO: (a) SEM image; (b) EDS map for C; (c) EDS map for O; (d) EDS map for S; (e) EDS map for Zn.
Figure 9
Figure 9
SEM image and EDS maps for SBR vulcanizate containing N-ZnO: (a) SEM image; (b) EDS map for C; (c) EDS map for O; (d) EDS map for S; (e) EDS map for Zn.
Figure 10
Figure 10
SEM image and EDS maps for SBR vulcanizate containing MBPP-Zn: (a) SEM image; (b) EDS map for C; (c) EDS map for S; (d) EDS map for Zn.
Figure 11
Figure 11
Loss factor (tan Δ) curves versus temperature of SBR vulcanizates containing ZnO and zinc complexes with 1,3-diketones as activators.
Figure 12
Figure 12
The influence of prolonged thermo-oxidation on the properties and crosslink density of SBR vulcanizates containing ZnO and zinc complexes with 1,3-diketones as activators: (a) crosslink density; (b) hardness; (c) stress at 100% relative elongation; (d) tensile strength; (e) elongation at break.
Figure 12
Figure 12
The influence of prolonged thermo-oxidation on the properties and crosslink density of SBR vulcanizates containing ZnO and zinc complexes with 1,3-diketones as activators: (a) crosslink density; (b) hardness; (c) stress at 100% relative elongation; (d) tensile strength; (e) elongation at break.
Figure 13
Figure 13
Thermogravimetric (TG) and Derivative Thermogravimetric (DTG) curves of SBR vulcanizates containing ZnO and zinc complexes with 1,3-diketones as activators: (a) TG curves; (b) DTG curves.
Figure 14
Figure 14
Thermal stability of zinc complexes with 1,3-diketones: (a) TG curves; (b) DTG curves.
See this image and copyright information in PMC

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