An alternative antioxidant for sulfur-vulcanized natural rubber: Henna

Abstract

Oxidative aging of natural rubber (NR) leads to the deterioration in the physical and mechanical properties. Using various antioxidants during compounding is a common way to improve the aging resistance of NR. The most widespread used antioxidants are phenolic and amine-based synthetic antioxidants and 2,2,4-trimethyl-1,2-dihydroquinoline in rubber industry. However, synthetic antioxidants cause some environmental problems during their production and tend to be replaced by natural alternatives. In this study, henna has been evaluated as a natural antioxidant in NR-based rubber compounds for efficient and conventional sulfur vulcanization systems. Performance of henna was evaluated in terms of rheological, mechanical, aging, and temperature scanning stress-relaxation properties of the compounds. It has been concluded that henna could be used as an alternative antioxidant for sulfur vulcanization of natural rubber matrix, compensating little deteriorations in vulcanizate properties. Short- and long-term performances of henna were also found to be related to vulcanization system.

Relationship between stress relaxation behavior and thermal stability of natural rubber vulcanizates

“…Furthermore, they also found that the change of stress relaxation behavior was caused by the cleavage of crosslinks or scission of main chains. Similar observation was also noticed by Oncel et al [15] when they studied the oxidative thermal aging behaviour of the NR containing new type of antioxidants. Karaagac et al [16] used TSSR to investigate the stress relaxation of NR and ethylene propylene diene rubber and revealed the effect of molecular weight on the pattern of stress relaxation.…”

“…Temperature scanning stress relaxation (TSSR) measurement is a well-known technique used for determining stress relaxation behaviors of thermoplastic elastomers [13] . However, it was also useful for analysing relaxation behaviour or thermo-mechanical behaviour of unfilled rubbers vulcanizates [14][15][16] . Vennemann et al [14] determined the relaxation behavior of NR crosslinked with different vulcanization systems by using TSSR.…”

Vulcanization of chlorinated polyethylene / chloroprene rubber compounds at lower temperatures in the presence of reactive silanes

“…In most cases, high level of cross‐link density causes rubber vulcanizates to have relatively higher hardness values. However, high level of cross‐link density and stable cross‐link structure ensure to maintain tensile modulus in a narrow range during thermal aging 42 . When A and E vulcanizates are compared, increase in the modulus is obviously lower for amino silane vulcanizates.…”

“…Since the non‐isothermal relaxation test is carried out for wide temperature range, it can also refer thermal stability of the vulcanizates over service temperatures 27,42 . It is observed from Table 5 that, low amount of CPE incorporation could provide better modulus stability during heating under 50% extension.…”

Jojoba seed powder as eco‐friendly antioxidant for rubber products

“…2 Öncel et al studied the antioxidant effect of henna for NR and found that it is a good alternative to commercial antioxidants. 11 Based on these reports that revealed that the use of plant extracts improved the aging property of the rubber compounds, this work aimed to explore the antioxidant effect of jojoba seed powder (JSMP) in NBR-based formulation and at the same time this work is an attempt to beneficially dispose of jojoba seed meal. To the best of the authors' knowledge, there has been no report(s) on the use of JSMP in rubber compounds.…”