Synthesis and Characterization of Sustainable Inverse Vulcanized Copolymers from Non‐Edible Oil

Abstract

Inverse vulcanization is a facile solvent‐free process, which offers interesting sustainable copolymers from the reaction of sulfur with petro‐based monomers or edible vegetable oils. However, sulfur reaction with the former contradicts green chemistry, whereas the latter reduces the viability of the product and can contribute to the food crisis. Herein, we report the preparation of sulfur‐based polymer (SBP) by the reaction of rubber seed oil, RSO (a non‐edible oil), to produce a sustainable sulfur‐based copolymer for the first time. The properties of the new polymer were evaluated using different techniques such as Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy coupled with energy dispersive X‐rays (SEM‐EDX‐mapping), powdered X‐ray diffractometer (p‐XRD), thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC). The polymer was found to be soluble in tetrahydrofuran, thermally stable to 200 °C, and a low glass transition temperature (−6.41 to −7.85 °C for a polymer with 50 to 70 wt % S). The polymer morphological and DSC analysis demonstrated a uniform surface possessing a small amount of unreacted microscale sulfur particles that is lesser than similar polymers from other oils, which was confirmed by DSC. The P‐XRD analysis revealed the amorphous nature of the copolymer caused by a heavily crosslinked structure. The effect of the post‐polymerization treatment on the properties of the copolymers was also investigated which revealed that increasing the curing temperature or quenching medium temperature increases the glass transition temperature of the copolymer. The polymer properties were dramatically improved by reducing the amount of the unreacted sulfur by the addition of a small amount of 1,3‐diisopropeynyl benzene (crosslinker), leading to 99.75 % sulfur conversion, the highest ever value achieved in such SBPs. It can be concluded that the use of RSO with sulfur enhances the sustainability of SBP and promotes their adding products

Conversion of palm oil to new sulfur-based polymer by inverse vulcanization

“…Figure 3 demonstrates the FTIR spectra of poly (S-Palm oil) 70:30 together with pure palm oil as a reference. Pure palm oil shows a very similar spectrum compared to other vegetable oils in literature due to the composition similarity of different vegetable oil species [22,33]. Particularly, palm oil shows a small vinylic C=C double bond stretching peak at 1655 cm -1 and vinylic C-H stretching vibration at 3006 cm -1 .…”

“…Later on, some bio-based monomers such as limonene [19], diallyl disulfide [20], and squalene [21] and vegetable oils like rubber seed [22,23], sunflower, linseed, olive [24], canola [25], and soybean [26] oils showed potential to react with elemental sulfur by inverse vulcanization technique. The reactions of sulfur with various monomers both petro-based and bio-based and the properties of the obtained copolymers have been recently reviewed [3,6].…”

A Degradable Inverse Vulcanized Copolymer as a Coating Material for Urea Produced under Optimized Conditions

“…A 25-mL glass vial was filled with the designed weight of the elemental sulfur and placed in a thermoset oil bath preheated to a required reaction temperature under vigorous stirring to initiate the formation of the thiyl radicals. First, the elemental sulfur upon heating starts to melt, after which when the temperature reaches >159 • C, octet structure of the sulfur starts to open to form the thiyl radicals, which is accompanied by the color change from yellow color to orange color liquid; at this point, the designed amount of the jatropha oil is added in a dropwise manner to avoid a sudden decrease in temperature [30][31][32]. After adding jatropha oil to the glass vial, a plaque mixture was formed, which was allowed to react under vigorous stirring for the designed time.…”

“…Vegetable oils consist of an unsaturated portion and a saturated portion, of which the unsaturated portion can act as a comonomer to produce sulfur-based polymers; nevertheless, the complex structure of vegetable oils and also their impurity (saturated portion) make it more difficult to produce controlled sulfur-based polymers using vegetable oils as monomers [21,23,24]. Oils of different vegetables including canola [25][26][27][28], castor [29], rubber seed [30,31], palm [32], linseed [33], corn [34], olive [33], sunflower [33], rice bran [29], soybean [35], and cottonseed [36] have been employed as monomers in the production of sulfur-enriched polymers. Due to the presence of the unsaturated section of vegetable oils, their copolymerization with sulfur results in composite structures because of the presence of the unreacted sulfur.…”

Copolymerization of palm oil with sulfur using inverse vulcanization to boost the palm oil industry

“…32,40 Poly (S-Palm oil) showed zero solubility in conventional organic solvents such as toluene, chloroform, THF, DMF, n-hexane, ethanol, methanol, 2-Propanol, acetonitrile, and 1,4-dioxane. Besides rubber seed oil which was fully soluble in THF and partially soluble in chloroform, 34 poly (S-Canola oil) which was proved to be soluble in pyridine, 43 poly (S-Algae oil) in CHCl 3 , THF, and C 2 H 2 Cl 4 , 40 and also polymers made using sunflower, olive, and linseed oils which were partially soluble in H 3 C(CH 2 ) 5 CH 3 , 39 no solubility was reported for other sulfur-based polymers using vegetable oils. In general, vegetable oils with more linolenic acid and linoleic acid portions result in highly crosslinked sulfur-based polymers.…”