The Facile Modification of Polyacrylate Emulsion via Hexadecane to Enhance Controlled-release Profiles of Coated Urea

Abstract

Development of controlled-release urea (CRU) has attracted research attention because of food scarcity problems and environmental concerns. To slow down the nutrient release of CRU coated with waterborne polyacrylate, conventional emulsion polymerization (CEP), conventional emulsion polymerization containing hexadecane (CEP + HD), and miniemulsion polymerization (MP) were carried out to discern the influence of polymerization technique and hexadecane on the properties of emulsions, films, and on the resultant nutrient release profiles of controlled-release urea. The addition of hexadecane improved water resistance, decreased the glass-transition temperature, and slowed down the nutrient release. CEP + HD was superior to MP in retarding nutrient release since the majority of HD was distributed in the exteriors of the particles of the former and interiors of the particles of the latter. Exterior HD improved water resistance more effectively, while interior HD reduced glass-transition temperature more significantly. Overall, our findings showed that incorporation of HD into polyacrylate emulsion produces excellent coatings that delay the release of urea. It has great potential application in controlled-release fertilizers coated with waterborne polymers.

Experimental Evaluation of the Miniemulsion Polymerization of Vinyl Pivalate: The role of the Main Process Variables

“…Table 5 presents the values of the glass transition temperatures (T g ) of the latexes obtained through the DSC curves. The glass transition temperatures of all the latexes synthesized in this work ranged from 50 to 72 °C and were lower in relation to the PVPi samples obtained in other works in the literature by suspension or emulsion polymerization, in which the T g values were in around 81 °C [24,39] for samples with the same ranges of average molar mass. The reduced values observed here for the latexes are related to the miniemulsion polymerization process, in which co-stabilizer, hexadecane, used to prevent Ostwald ripening, can act as a plasticizer because it is a non-volatile substance and remains in the polymeric structure, causing a reduction in intermolecular forces between the chains, increasing molecular mobility and consequently reducing T g .…”

“…The plasticizer effect is also noticed in the miniemulsions obtained with higher amounts of hexadecane (comparing samples PVPi‐01 with PVPi‐02, PVPi‐03 with PVPi‐04, PVPi‐05 with PVPi‐06, PVPi‐07 with PVPi‐08, PVPi‐09 with PVPi‐10, and PVPi‐11 with PVPi‐12), corroborating the previous results, in which there is a significant reduction in T g with the increase in the concentration of co‐stabilizer. [ 40 ]…”

“…The third and fourth stages in the range of 400 to 500 °C and 500 to 700 °C, respectively, corresponding to a loss of ≈12% are related to the polymer backbone degradation and the decomposition of organic matter. [24,39] Because the thermogravimetric analysis was carried out under an inert atmosphere, a residual content of 1.0 to 2.9% is observed for carbonaceous residues of the polymer. [41] The colloidal stability of PVPi was analyzed by dynamic light scattering (DLS), determining D p and polydispersity index (PdI) at different time intervals, as shown in Figure 5 for PVPi-11 sample.…”

Degradation of Polyacrylate in the Outdoor Agricultural Soil Measured by FTIR-PAS and LIBS

“…The rest of the mixture and the initiator solution (52 mL, 0.01 g/mL, KPS) were fed alternately in four doses over 3 h, and then, the polymerization was conducted under air atmosphere for an additional 3 h. The films were obtained by the casting method. The PA emulsion was cast onto a nonstick substrate, and water was evaporated completely in an oven at 80 °C for 8 h. The basic properties of synthesized polymers were: particle size in emulsion, 100–250 nm; glass-transition temperature ( T g ), 6.38 °C; tensile stress at break (MPa), 4.66; Elongation at break (%), 1013; and Young’s modulus (MPa), 36 [20].…”

Optimization of metal–organic (citric acid) frameworks for controlled release of nutrients

“…5C), which are both signicantly lower than that reported for coated controlled-release fertilizers (N cumulative release rate over 80% within 70 days). 37,38 Interestingly, the N in the water was mostly present as NH 4 + -N (Fig. S1 †), while urea and NO 3 À -N were undetected.…”