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

Abstract

Global enhancement of crop yield is achieved using chemical fertilizers; however, agro-economy is affected due to poor nutrient uptake efficacy (NUE), which also causes environmental pollution. Encapsulating urea granules with hydrophobic material can be one solution. Additionally, the inverse vulcanized copolymer obtained from vegetable oils are a new class of green sulfur-enriched polymer with good biodegradation and better sulfur oxidation potential, but they possess unreacted sulfur, which leads to void generations. In this study, inverse vulcanization reaction conditions to minimize the amount of unreacted sulfur through response surface methodology (RSM) is optimized. The copolymer obtained was then characterized using Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC). FTIR confirmed the formation of the copolymer, TGA demonstrated that copolymer is thermally stable up to 200 °C temperature, and DSC revealed the sulfur conversion of 82.2% (predicted conversion of 82.37%), which shows the goodness of the model developed to predict the sulfur conversion. To further maximize the sulfur conversion, 5 wt% diisopropenyl benzene (DIB) as a crosslinker is added during synthesis to produce terpolymer. The urea granule is then coated using terpolymer, and the nutrient release longevity of the coated urea is tested in distilled water, which revealed that only 65% of its total nutrient is released after 40 days of incubation. The soil burial of the terpolymer demonstrated its biodegradability, as 26% weight loss happens in 52 days of incubation. Thus, inverse vulcanized terpolymer as a coating material for urea demonstrated far better nutrient release longevity compared with other biopolymers with improved biodegradation; moreover, these copolymers also have potential to improve sulfur oxidation.

Synthesis and performance evaluation of slow-release fertilizers produced from inverse vulcanized copolymers obtained from industrial waste

“…This method involves the usage of color reagent, which was prepared by mixing the 25 ml of DAM solution (prepared by dissolving 2.5 g of diacetyl monoxime in 100 ml of distilled water), 15 ml of TSC solution (prepared by dissolving 0.25 g of thiosemicarbazide in 100 ml of distilled water) and 460 ml of acid reagent (prepared by mixing 10 ml of sulfuric acid, 240 ml of distilled water and 250 ml of phosphoric acid). 20,21,28 2 g of coated urea was placed in a conical flask containing 200 ml of distilled water. To estimate the amount of the nitrogen released in distilled water from coated urea, after every 24 h 2.5 ml of the aliquot was taken and mixed with 7.5 ml of the color reagent and heated to a temperature of 85 °C for 30 min in a water bath followed by cooling at room temperature.…”

“…The obtained red color solutions were then analysed using Shimadzu UV-1800 UV-Vis spectrophotometer at 526 nm wavelength. 13,20,21…”

“…For biodegradability test same procedure was followed as explained in our previous reports. 13,20,21…”

“…Therefore, it arises a need to produce a copolymer which does not possesses any unreacted sulfur particle and can be considered as a sustainable copolymer. 20…”

Fly ash geopolymer as a coating material for controlled-release fertilizer based on granulated urea

“…7,8 Various types of coating materials have been used to produce urea based CRF such as sulphur, synthetic polymers, or biopolymers. [9][10][11][12] Suherman et al 13 reported that sulphur-coated urea exhibited a delayed urea release rate with 0.038 to 0.047 g s −1 as compared to uncoated urea release rate of 0.060 g s −1 . In another study, nutrient release in soil from uncoated urea was 100% while sulphur-coated urea showed ∼32% release aer 7 days of application.…”