Preliminary Study on Photochemical Degradation of Natural Rubber Latex

Abstract

Summary Liquid natural rubber (LNR) is considered as a new material which can be obtained from degradation of natural rubber (NR). In this work, the degradation of NR latex using photochemical degradation under UV light has been studied. In this preliminary result, the degradation degree was found to depend on parameters such as dry rubber content (DRC) of latex and reaction temperature. At the optimized parameters, the molecular weight (Mn) of NR was able to reduce from about 500 kg/mol to as low as 13 kg/mol. The molecular structure of LNR obtained was similar to that the NR, however, the presence carbonyl and hydroxyl groups were observed on the LNR chain as a result of the chain cleavage.

Preparation and Characterization of Low-Molecular-Weight Natural Rubber Latex via Photodegradation Catalyzed by Nano TiO2

“…The oxidation reactions by singlet oxygen, radical-induced auto-oxidation from hydrogen peroxide, and hydroperoxide photolysis resulting from UV light led to the formation of by-products such as hydroperoxy, hydroxyl, carbonyl, and epoxide groups [63]. These results were in agreement with reports by previous researchers that the degradation of NR by an oxidizing agent and hydroxyl radical leaves carbonyl and hydroxyl groups as the end groups [26,57,64,65,66].…”

“…These new small signals at the chemical shifts of 1.28, 3.47, 3.65, and 3.84 ppm could be assigned to methylene protons adjacent to the secondary alcohol, protons of the hydroxyl group, hydroxylated methane protons, and hydroxylated methylene protons, respectively [62,63]. The pattern of this spectrum was similar to that in our previous work for LNR prepared without TiO 2 [26].…”

“…This may have been due to the difficulty for the reagents and UV light to penetrate the membrane of the rubber particles [24]. In a recent work, when NR latex in the presence of hydrogen peroxide was exposed to UV light at an elevated temperature, significant degradation occurred wherein the molecular weight of the NR was reduced [25,26]. The use of TiO 2 as a photocatalyst in the degradation of NR latex was also studied.…”

Preparation and Characterization of Low-Molecular-Weight Natural Rubber Latex via Photodegradation Catalyzed by Nano TiO2

“…The oxidation reactions by singlet oxygen, radical-induced auto-oxidation from hydrogen peroxide, and hydroperoxide photolysis resulting from UV light led to the formation of by-products such as hydroperoxy, hydroxyl, carbonyl, and epoxide groups [63]. These results were in agreement with reports by previous researchers that the degradation of NR by an oxidizing agent and hydroxyl radical leaves carbonyl and hydroxyl groups as the end groups [26,57,64,65,66].…”

“…These new small signals at the chemical shifts of 1.28, 3.47, 3.65, and 3.84 ppm could be assigned to methylene protons adjacent to the secondary alcohol, protons of the hydroxyl group, hydroxylated methane protons, and hydroxylated methylene protons, respectively [62,63]. The pattern of this spectrum was similar to that in our previous work for LNR prepared without TiO 2 [26].…”

“…This may have been due to the difficulty for the reagents and UV light to penetrate the membrane of the rubber particles [24]. In a recent work, when NR latex in the presence of hydrogen peroxide was exposed to UV light at an elevated temperature, significant degradation occurred wherein the molecular weight of the NR was reduced [25,26]. The use of TiO 2 as a photocatalyst in the degradation of NR latex was also studied.…”

Conversion of Natural Rubber Into Renewable Polyol for Bio‐Based Polymer Synthesis

“…The degradation of natural rubber can be carried out through mechanical, thermal, or chemical reactions. The cleavage of carbon bonds can occur due to the photoactivity of reactive radical species or through chemical degradation via redox reactions [12]. Liquid epoxidized natural rubber (LENR) is commonly prepared by reacting epoxidized natural rubber (ENR) in emulsion/ latex state using periodic acid [13] or in the presence of sodium nitrite and hydrogen peroxide [14].…”

Preparation and Characterization of Low-Molecular-Weight Natural Rubber Latex via Photodegradation Catalyzed by Nano TiO2

“…The oxidation reactions by singlet oxygen, radical-induced auto-oxidation from hydrogen peroxide, and hydroperoxide photolysis resulting from UV light led to the formation of by-products such as hydroperoxy, hydroxyl, carbonyl, and epoxide groups [63]. These results were in agreement with reports by previous researchers that the degradation of NR by an oxidizing agent and hydroxyl radical leaves carbonyl and hydroxyl groups as the end groups [26,57,64,65,66].…”

“…These new small signals at the chemical shifts of 1.28, 3.47, 3.65, and 3.84 ppm could be assigned to methylene protons adjacent to the secondary alcohol, protons of the hydroxyl group, hydroxylated methane protons, and hydroxylated methylene protons, respectively [62,63]. The pattern of this spectrum was similar to that in our previous work for LNR prepared without TiO 2 [26].…”

“…This may have been due to the difficulty for the reagents and UV light to penetrate the membrane of the rubber particles [24]. In a recent work, when NR latex in the presence of hydrogen peroxide was exposed to UV light at an elevated temperature, significant degradation occurred wherein the molecular weight of the NR was reduced [25,26]. The use of TiO 2 as a photocatalyst in the degradation of NR latex was also studied.…”

Conversion of Natural Rubber Into Renewable Polyol for Bio‐Based Polymer Synthesis

“…The degradation of natural rubber can be carried out through mechanical, thermal, or chemical reactions. The cleavage of carbon bonds can occur due to the photoactivity of reactive radical species or through chemical degradation via redox reactions [12]. Liquid epoxidized natural rubber (LENR) is commonly prepared by reacting epoxidized natural rubber (ENR) in emulsion/ latex state using periodic acid [13] or in the presence of sodium nitrite and hydrogen peroxide [14].…”

Preparation and Characterization of Low-Molecular-Weight Natural Rubber Latex via Photodegradation Catalyzed by Nano TiO2

“…The oxidation reactions by singlet oxygen, radical-induced auto-oxidation from hydrogen peroxide, and hydroperoxide photolysis resulting from UV light led to the formation of by-products such as hydroperoxy, hydroxyl, carbonyl, and epoxide groups [63]. These results were in agreement with reports by previous researchers that the degradation of NR by an oxidizing agent and hydroxyl radical leaves carbonyl and hydroxyl groups as the end groups [26,57,64,65,66].…”

“…These new small signals at the chemical shifts of 1.28, 3.47, 3.65, and 3.84 ppm could be assigned to methylene protons adjacent to the secondary alcohol, protons of the hydroxyl group, hydroxylated methane protons, and hydroxylated methylene protons, respectively [62,63]. The pattern of this spectrum was similar to that in our previous work for LNR prepared without TiO 2 [26].…”

“…This may have been due to the difficulty for the reagents and UV light to penetrate the membrane of the rubber particles [24]. In a recent work, when NR latex in the presence of hydrogen peroxide was exposed to UV light at an elevated temperature, significant degradation occurred wherein the molecular weight of the NR was reduced [25,26]. The use of TiO 2 as a photocatalyst in the degradation of NR latex was also studied.…”

Conversion of Natural Rubber Into Renewable Polyol for Bio‐Based Polymer Synthesis

“…The degradation of natural rubber can be carried out through mechanical, thermal, or chemical reactions. The cleavage of carbon bonds can occur due to the photoactivity of reactive radical species or through chemical degradation via redox reactions [12]. Liquid epoxidized natural rubber (LENR) is commonly prepared by reacting epoxidized natural rubber (ENR) in emulsion/ latex state using periodic acid [13] or in the presence of sodium nitrite and hydrogen peroxide [14].…”