Influence of ZnO on the properties of elastomeric compositions and their leached extract

Torani, Daiane; Crespo, Janaina da Silva; Brandalise, Rosmary Nichele

doi:10.1590/0104-1428.07218

Daiane Torani

Universidade de Caxias do Sul – UCS, Caxias do Sul, RS, Brasil

Janaina da Silva Crespo

Universidade de Caxias do Sul – UCS, Caxias do Sul, RS, Brasil

Rosmary Nichele Brandalise ^* * rnbranda@ucs.br

Universidade de Caxias do Sul – UCS, Caxias do Sul, RS, Brasil

http://orcid.org/0000-0002-4719-6093

* rnbranda@ucs.br

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Figure 1
Reaction between ZnO and stearic acid forming zinc stearate and the molar masses of each chemical substance in the reaction.

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Figure 2
Crosslinking density and vulcanization rate of the elastomeric compositions developed with different ZnO contents in phr.

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Figure 3
Zinc stearate formation and vulcanization mechanisms for Step 1 compositions. Adapted from Joseph et al.^[¹⁴14 Joseph, A. M., George, B., Madhusoodanan, K. N., & Rosamma, A. (2015). Current status of sulphur vulcanization and devulcanization chemistry: process of vulcanization. Rubber Science, 28(1), 82-121. Retrieved in 2019, September 6, from htps://www.researchgate.net/publication/275519885^] and Coran^[¹¹11 Coran, A. Y. (2013). Vulcanization. In: Mark, J. E., Erman, B., & Roland, M. The science of rubber compounding (pp. 337-338). Boston: Elsevier. http://dx.doi.org/10.1016/B978-0-12-394584-6.00007-8.
http://dx.doi.org/10.1016/B978-0-12-3945... ^].

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Figure 4
Tear strength and hardness for the FC1/AE/0, F1/AE/1, F1/AE/3 and F1/AE/5 compositions.

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Figure 5
Tensile strength, elongation at break and modulus at 300% for the FC1/AE/0, F1/AE/1, F1/AE/3 and F1/AE/5 compositions.

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Figure 6
Tensile strength and elongation at break retention for the FC1/AE/0, F1/AE/1, F1/AE/3 and F1/AE/5 compositions after thermo-oxidative ageing during a period of 7 and 14 days exposure (the dotted line corresponds to 100%).

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Table 1
Composition and coding for the elastomeric formulations.

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Table 2
Rheological and rheometric properties of the elastomeric compositions developed for different ZnO contents in phr.

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Table 3
Decomposition temperatures of the elastomeric compositions developed with different ZnO contents in phr.

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Table 4
Stoichiometric ratio of the elastomeric compositions developed with different ZnO contents in phr.

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Table 5
Zn content in mg of Zn⋅L^-1 for the elastomeric compositions released in the leached extract in accordance with ASTM 6234-13 with statistical analysis of the samples studied after each step under study.

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(1)

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(2)

	Raw material (phr content)
Codification	NR ^{^d} d NR-natural rubber;	ZnO ^{^e} e ZnO-zinc oxide;	sulfur	stearic acid	CBS ^{^f} f CBS-accelerator;
FC^a a FC- control formulation; /AE^c c AE-estearic acid; /0^g g The number indicates the ZnO content in the composition.	100	0	2	2	0.6
F1^b b F1-formulation; /AE/1	100	1	2	2	0.6
F1/AE/3	100	3	2	2	0.6
F1/AE/5	100	5	2	2	0.6

Codification	Mooney viscosity [ML 1+4 100 °C]	M_L (dN·m)	M_H (dN·m)	t_s1 (min)	t₉₀ (min)	CRI ^* * Cure rate index - CRI = 100/(t90-ts1). (min^-1)
FC1/AE/0	49.68	1.32	4.04	6.06	7.18	89.3
F1/AE/1	37.98	1.26	6.99	5.31	9.21	25.6
F1/AE/3	42.01	1.21	7.84	6.03	11.06	19.9
F1/AE/5	37.83	1.09	7.86	5.18	10.18	20.0

Compositions	T_onset (°C)	T_endset (°C)	T_Max (°C)	Mass loss (%)	Residues (%)
FC1/AE/0	358.8	411.9	385.7	99.8	0.2
F1/AE/1	359.2	416.0	386.2	98.8	1.2
F1/AE/3	360.2	416.7	386.5	97.2	2.8
F1/AE/5	361.8	417.5	388.2	95.4	4.6

Composition	X ^a a X – ZnO amount utilized in the formulations considering 99.5% purity; (g)	Y ^b b Y – amount calculated by Equation 2, required for reaction with the ZnO amount employed considering the stoichiometric ratio. (g)	Stearic acid amount employed in the formulation (g)
F1/AE/1	10.7	74.7	13.1
F1/AE/3	31.5	219.9	13.1
F1/AE/5	51.5	360.1	13.1

Composition	Before Cure (mg⋅L-1)	After cure (mg⋅L-1)	After aging (mg⋅L-1)
F1/AE/1	0.18	0.20	0.45
F1/AE/3	0.79	0.69	1.44
F1/AE/5	1.15	1.19	2.16
ANOVA
Source of variation	SQ	gl	MQ	F	P Value	F critical	Significant
Before Cure	0.86	1	0.86	26.6123	0.035	18. 5128	Yes
After Cure	0.81	1	0.81	12. 9392	0.069	18. 5128	No
After Aging	3.09	1	3.09	23. 8828	0.039	18. 5128	Yes

[1] * rnbranda@ucs.br

Brasil

Brasil

Influence of ZnO on the properties of elastomeric compositions and their leached extract

Abstract