Determination of epoxy groups in natural rubber (original) (raw)
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Partial conversion of epoxide groups to diols in epoxidized natural rubber
Epoxidized natural rubber (ENR) is fairly stable in its latex state. Only a small amount of the epoxide groups were converted to diols when the latex was boiled under mildly acidic or alkaline pH. Although the small amount of diols could not be determined accurately by 1H nuclear magnetic resonance (n.m.r.), their presence could be demonstrated by the degradation reaction using lead tetraacetate. The formation of -OH and carbonyl groups after the degradation could be clearly seen in the infra-red spectra. Higher level of diols could be introduced by reacting ENR-50 dissolved in toluene with a mixture containing water and acetic acid in tetrahydrofuran at 60°C. The amount of conversion of epoxide to diol increases with reaction time, and up to 23mo1% of diol in the rubber chain can be achieved after 24h of reaction. The extent of conversion can be determined from the 1H n.m.r, spectra of the samples. The ENR containing diols in the main chain could serve as a good intermediate for further chemical modifications. For example, cleavage of the diol groups with specific reagents could offer a convenient route to the production of liquid ENR.
Latex-state NMR spectroscopy for quantitative analysis of epoxidized deproteinized natural rubber
Polymers for Advanced Technologies, 2017
Method of quantitative analysis through latex-state 13 C NMR spectroscopy was established for in situ determination of epoxy group content of epoxidized natural rubber in latex stage. The epoxidized natural rubber latex was prepared by epoxidation of deproteinized natural rubber with freshly prepared peracetic acid in latex stage. The resulting epoxidized deproteinized natural rubber (EDPNR) latex was characterized through latex-state 13 C NMR spectroscopy. Chemical shift values of signals of latex-state 13 C NMR spectrum for EDPNR were similar to those of solution-state 13 C NMR spectrum for EDPNR. Resolution of latex-state 13 C NMR spectrum was gradually improved as temperature for the nuclear magnetic resonance (NMR) measurement increased to 70°C. Signal-to-noise ratio of latex-state 13 C NMR measurement was similar to that of solution-state 13 C NMR measurement at temperature above 50°C. The epoxy group content determined through latex-state NMR spectroscopy was proved to be the same as that determined through solution-state NMR spectroscopy.
2020
The degradation of epoxidized natural rubber (ENR-50) and liquid epoxidized natural rubber (LENR) was done via oxidative degradation method for the production of hydroxyl terminated epoxidized natural rubber (HTENR) and hydroxyl terminated liquid epoxidized natural rubber (HTLENR) has been analysed. Cobalt (II) acetylacetonate (CAA) were used as an oxidizing agent for chain scission reaction at temperature 60 C in the presence of ethanol. The reaction temperature was fixed at 60 C meanwhile reaction time and the amount of CAA were varied according to the reaction formulation. The HTENR and HTLENR obtained have been characterized using Gel Permeation Chromatography (GPC), Fourier Transform Infrared (FTIR) and Nuclear Magnetic Resonance (NMR). GPC were used to determine the molecular weight before and after the oxidative degradation of respected HTENR and HTLENR were compared with ENR-50 and LENR. The lowest Mn and Mw of HTLENR that were obtained from the oxidative degradation method ...
European Polymer Journal, 1990
The oxidations in air of epoxidized natural rubber (ENR) and its hydrobrominated product were studied and compared with the case of natural rubber (NR). By following the i.r. characteristic bands at 580, 840, 870, 1720, 1760 and 3200-3600cm -t during the oxidation, it was demonstrated that the hydrobrominated product of ENR is the most unstable both at room temperature and at 150 °. NR oxidizes more quickly and to a greater extent than ENR. The oxidation proceeds through consumption of double bonds, leading to the formation of new oxygen-containing functional groups (hydroperoxide, hydroxyl, carbonyl, carboxyl... ), changing the structure and properties of the materials. The absence of associated hydroxyl groups in the OH spectral region of hydrobrominated ENR products of low epoxide contents suggests the presence of randomly distributed epoxide groups in the polymer and indicates the random character of the epoxidation process of NR in latex.
A structural study of epoxidized natural rubber (ENR-50) ring opening under mild acidic condition
A structural study of ring opening reaction of purified epoxidized natural rubber (ENR) with acetic acid was conducted using the NMR techniques and its thermal characteristic was evaluated with TG/DTG and DSC analyses. 1 H-NMR revealed that 19.56% of epoxide was ring-opened from the total amount of the epoxide unit in ENR-50 and this was supported by FTIR spectros-copy. 13 C-NMR suggests the fixation of alkyl (R) i.e. acetate group to the epoxide carbon via ester linkage and formation of hydroxyl groups in the polymer chains. The attachment location of R occurred at both most (") and least (#) hindered carbons of the epoxide. The TG/DTG results of acid treated ENR-50 showed three decomposition steps at 235–338, 338–523, 523–627 8C due to the presence of the polymer chains mixture, i.e. ring-opened and intact epoxide of ENR-50. This increases the T g value of acid treated ENR-50 at 24.6 8C as compared to purified ENR-50 at 217.7 8C. V
Journal of Applied Polymer Science, 2004
Oxidative degradation of epoxidized natural rubber (ENR) was effectively performed in latex phase by using periodic acid at 30°C. The ENR was prepared from the epoxidation of natural rubber in latex phase using performic acid generated in situ by the reaction of hydrogen peroxide and formic acid. The prepared ENR latex was subsequently treated with periodic acid. It was found that the higher the amount of the periodic acid employed the faster the molecular weight of the ENR decreased. Different epoxidation levels of the ENR had no significant effect on the degradation reaction. Based on 1 H NMR analysis, the epoxide content in the epoxidized liquid natural rubber (ELNR) obtained was about the same as that observed in the ENR before degradation. FT-IR analysis showed an increase in carbonyl signal after prolonged reaction time or when higher amounts of periodic acid were employed.
Preparation and Characterization of Hydroxyl Terminated Liquid Epoxidized Natural Rubber
Chemical engineering transactions, 2020
Hydroxyl terminated liquid epoxidized natural rubber (HTLENR) was successfully synthesized via oxidative degradation of liquid epoxidized natural rubber (LENR) in the presence of cobalt (II) acetyl acetonate (CAA) as the oxidizing agent. The effect of reaction time on molecular weight, chemical structures and hydroxyl content of HTLENR were investigated. The weight average molecular weight (Mw) and polydispersity index (PDI) of the prepared HTLENR were determined using gel permeation chromatography (GPC). The result shows that as the reaction time increased, the Mw decreased indicating the occurrence of higher chain scission. It was found that the lowest Mw was achieved at 10 h reaction time where the Mw and Mn were 37,545 g/mol and 3,233 g/mol. The structural analysis and hydroxyl content of HTLENR on the other hand, were studied by using fourier transform infrared (FTIR) and nuclear magnetic resonance (NMR). The presence of OH group was confirmed by FTIR analysis with the appearan...
The investigation of optimum condition of natural rubber epoxidation reaction in latex phase
Majalah Kulit, Karet, dan Plastik, 2021
Natural rubber (NR) latex epoxidation is a chemical modifcation of natural rubber to produce natural rubber with higher polarity (oil resistant) which is commonly called epoxidized natural rubber (ENR). ENR is produced from the reaction of natural rubber latex with performic acid. Performic acid is formed from in situ reaction between formic acid and hydrogen peroxide. During epoxidation process, the carboxyl group of natural rubber is converted into epoxy group and various side reaction products such as carbonyl, hydroxyl, and hydro furan. These side products must be minimalized to optimize the epoxy level. The epoxidation reaction was carried out at 70 ° C for 6 hours using 2 types of latex: fresh latex (FL) and concentrated latex (CL). The addition of reactant was varied in two ways: dropwise (coded “1”) and poured all at once (coded “2”). The epoxy product and rate constant (k) were analyzed to obtain optimum reaction condition. The epoxy and side reaction content were determine...
Characterization of epoxidized natural rubber by 2D NMR spectroscopy
Polymer, 2007
Assignment of signals in aliphatic region of 1 H NMR spectrum for epoxidized natural rubber was carried out through NMR spectroscopy. The epoxidized natural rubber was prepared by epoxidation of purified natural rubber with peracetic acid in latex stage followed by degradation with propanal and ammonium persulfate. The resulting liquid epoxidized natural rubber was characterized through 1D-and 2D-NMR spectroscopy. The unknown signals in the aliphatic region of the 1 H NMR spectrum were assigned through 13 C NMR and two-dimensional heteronuclear shift correlation (HETCOR) measurement. The assignments were proved by two-dimensional inverse detected heteronuclear long-range shift correlation (HMBC) and two-dimensional homonuclear shift correlation (COSY) measurements, and they were supported with epoxidized squalene as a model compound through NMR spectroscopy.
Reactions Between Epoxidized Natural Rubber and Palm Oil-Based Alkyds at Ambient Temperature
The reactions between epoxidized natural rubber (ENR) and a low-molecular weight palm oil-based alkyd (A1) have been investigated. Experimental results (FTIR and toluene swelling tests) showed that the alkyd having both hydroxyl and carboxylic groups could react with the epoxide groups of ENR at ambient temperature to cause crosslinking. To establish the predominant reaction, alkyd A1 was chemically modified to vary the amount of hydroxyl and carboxylic groups. A1 was treated with maleic anhydride under two different temperatures of 130 and 185 C. At 130 C, the anhydride has reacted partially with the hydroxyl groups to produce alkyd A2 with higher carboxylic content and lower hydroxyl content. On the other hand, at 185 C, the anhydride has reacted completely to produce alkyd A3 with similar carboxylic acid content as A1 but lower hydroxyl content. Subsequent reactions of A2 and A3 with ENR under similar conditions have demonstrated that the predominant reaction with epoxide groups was due to the carboxylic groups from the fact that A2 could form higher amount of crosslinkages than A3, which has lower carboxylic content similar to A1. V C 2010 Wiley Periodicals, Inc. J Appl Polym Sci 120: [1503][1504][1505][1506][1507][1508][1509] 2011