Mechanical and Aging Properties of Hydrogenated Epoxidized Natural Rubber and Its Lifetime Prediction

Abstract

Natural rubber (NR) has restricted its application due to its potential for thermal- and oil-resistant materials. The weakness of NR can be eliminated by chemical modification to enhance aging properties. Formic acid and hydrogen peroxide have been used to prepare partially epoxidized natural rubber (ENR) in the latex state. Its residual unsaturated units were then modified using hydrazine and hydrogen peroxide to obtain hydrogenated ENR (HENR). 1H-NMR characterized the resulting products. NR and modified NRs were compounded and then vulcanized using a conventional milling process. This paper compares NR, ENR having 49.5% epoxide group content, and HENR having 49.5% epoxide group content and 24% hydrogenation degree in terms of tensile, thermal, oil, and ozone properties. Morphology and lifetime prediction were studied. Overall results show that the tensile strength of the HENR composite (14.7 MPa) was 79 and 71% lower than that of ENR (18.6 MPa) and NR (20.8 MPa) composites, respectively. In contrast, the modulus at 100% elongation of the HENR composite (2.0 MPa) was 167 and 200% higher than that of ENR (1.2 MPa) and NR (1.0 MPa) composites, respectively. Morphological studies of the tensile fractured surface of the vulcanizates, using scanning electron microscopy, confirmed a shift from ductility failure to brittle with the presence of the epoxide groups and low unsaturated bonds in the backbone chain. The results demonstrated that HENR could act as an ideal material, providing better thermal, oil, and ozone resistances while maintaining the mechanical properties of the rubber. The kinetic analyses of the thermal degradation of NR, ENR, and HENR were studied using thermogravimetric analysis (TGA) at three heating rates. Kissinger–Akahira–Sunose (KAS) was employed to calculate the activation energy (E a). The obtained data were used to predict the lifetime under the established temperature range and 0.05 conversion level. Overall, the results represented that HENR had a longer lifetime than NR and ENR for a temperature range between 25 and 200 °C, indicating that HENR had excellent thermal stability than NR and ENR. Therefore, the HENR should extend the applications to include gaskets and seals, especially for the automotive and oil industries.

Influence of acid concentration on thermomechanical, tensile and thermal properties of cyclized natural rubber

“…It is well accepted that the presence of unsaturated double bonds in the NR chains readily degraded when it is exposed to heat and oxygen, deteriorating the properties of rubber after aging. 4,5 As compared to the NR, the higher retention of property was achieved from the cyclized NRs, revealing that the cyclized NRs had greater resistance to degradation caused by heat aging. Increasing the degree of cyclization also improved the degree of property retention.…”

“…3 Owing to the structure of NR containing a lot of unsaturated double bonds, it is easily oxidized when exposed to heat, oxygen, ozone, or light in its environment, leading to poor aging characteristics and low thermal resistance. 4,5 Several techniques have been pursued to address these problems. Among the various alternatives, cyclic NR is of particular interest.…”

Enhanced performance of environmental resistance and reprocessability of epoxidized natural rubber via incorporating fluorinated short side chains and β‐hydroxyl ester bonds

“…19 As a kind of modified NR, ENR has excellent oil and air tightness resistance, good wet-grip and low rolling resistance due to the introduction of epoxy groups. [20][21][22] However, this epoxidation simultaneously brings some extent of loss to the aging resistance. 23 Therefore, we incorporated fluorinated components and constructed a reversible cross-linking molecular network between ENR molecular chains with sodium trifluoroacetate as a short fluorinated side chain, 2,2-dithiodibenzoic acid (DTSA) as a cross-linking agent, DMI as an esterification reaction promoter, and zinc acetate (Zn(Ac) 2 ) as an ester exchange catalyst in this work.…”

“…As a kind of modified NR, ENR has excellent oil and air tightness resistance, good wet‐grip and low rolling resistance due to the introduction of epoxy groups 20–22 . However, this epoxidation simultaneously brings some extent of loss to the aging resistance 23 .…”

Study of Solvent and Catalyst in Diimide Biphasic Hydrogenation System of Natural Rubber

“…Natural rubber plays a vital role in various aspects of human life, with applications in fields such as medical equipment and industry (Kim et al, 2020;Saengdee, Phinyocheep, and Daniel, 2020;Inoue and Nishio, 2007). Despite its significance, natural rubber contains carbon double bonds (Cifriadi, Chalid, and Puspitasari, 2017;Piya-areetham, Prasassarakich, and Rempel, 2013) that make it less resistant to oxidation, heat, ozone, and other environmental factors (Ngudsuntear et al, 2022). However, this limitation can be overcome by chemically modifying it, potentially making it a substitute for the thermally resistant Ethylene Propylene Diene Monomer (EPDM) rubber (Taksapattanakul et al, 2019;Inoue and Nishio, 2007).…”