Chemical modification of natural rubber in latex stage for improved thermal, oil, ozone and mechanical properties
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ORIGINAL PAPER
Chemical modification of natural rubber in latex stage for improved thermal, oil, ozone and mechanical properties Laksana Saengdee 1,2 & Pranee Phinyocheep 1
&
Philippe Daniel 2
Received: 10 December 2019 / Accepted: 10 August 2020 # The Polymer Society, Taipei 2020
Abstract In this work, chemical modification of natural rubber in latex stage was focused on a green condition and to improve thermal, ozone and mechanical properties. Two chemical modifications including epoxidation followed by hydrogenation of natural rubber latex (NRL) were carried out continuously in one-pot system. The NRL was treated with in situ performic acid generated from the reaction of formic acid and hydrogen peroxide to obtain partially epoxidized product or epoxidized natural rubber (ENR) latex which was then further modified its residual unsaturated units using hydrazine and hydrogen peroxide to perform hydrogenation reaction. The chemical structure of the obtained modified rubber so called hydrogenated epoxidized natural rubber (HENR) was characterized by 1H-NMR and ATR-FTIR. Two types of HENR including HENR-1 (27 mol% degree of hydrogenation and 17 mol% degree of epoxidation) and HENR-2 (25 mol% degree of hydrogenation and 28 mol% degree of epoxidation) were subjected to investigate their thermal properties compared to the NR, ENR and hydrogenated NR (HNR). It was found that the modified NRs possess higher thermal property and increased Tg as compared to NR, due to both incorporation of epoxide units and reduced unsaturation of the molecular chain. The prepared HENRs were found to maintain the strain induced crystallization character which is the feature of NR. The vulcanized HENR-1 and HENR-2 showed superior tensile strength compared to vulcanized NR. In addition, the oil and ozone resistances of modified NRs were also improved. The preparation of HENR in one-pot latex system is a facile condition and save energy for any solvent recovery. The procedure can be considered as a potential green and sustainable development of NR. Keywords Natural rubber . Epoxidation . Hydrogenation . Oil resistance . Ozone resistance
Introduction Natural rubber (NR) is an intriguing renewable rubber produced from Hevea brasiliensis tree in which it has become one of the most important raw materials in a vast of industries, including the production of tires for automobile and airplane, industrial and engineering goods, medical devices such as tracheal tube and medical gloves. The outstanding properties of NR lead to rubber products performing high fatigue resistance, high resilience, low heat build-up, low creep and good tack property [1–4]. Additionally, because of awareness of the * Pranee Phinyocheep [email protected] 1
Department of Chemistry, Faculty of Science, Mahidol University, Bangkok, Thailand
2
Institut des Molécules et des Matériaux du Mans, IMMM-UMR-CNRS 6283, Le Mans Université, Le Mans, France
environment conservation and declination of utilization of petroleum-based synthetic rubbers, the use of NR as an eco
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