Kinetics Of Grafting Reaction Research Articles

Controlled release of phosphorous fertilizer bound to carboxymethyl starch-g-polyacrylamide and maintaining a hydration level for the plant

A controlled release fertilizer system based on phosphate bound-carboxymethyl starch-graft-polyacrylamide (P-CMS-g-PAM) has been prepared in order to deliver the phosphate fertilizer to the plant at a constant rate thereby. This system aims to increase fertilizer phosphorus use efficiency (FPUE) and maintain a hydration level for the plant at the same time. Two types of starch phosphate monoesters were prepared using mono-ammonium (MAP) and di-ammonium phosphate (DAP). First, starch was converted to carboxymethyl starch and then was phosphorylated with mono-ammonium dihydrogen phosphate and di-ammonium dihydrogen phosphate. After phosphorylation, the samples were grafted with acrylamide in the presence of methylene bisacrylamide as a crosslinking agent. The prepared systems of P-CMS-g-PAM were differently characterized by Fourier transformer infrared (FT-IR), thermogravimetric analysis (TGA), scanning electron microscope (SEM) and phosphorous analysis. The swelling behavior was investigated. The kinetics of grafting reaction were also studied. The release behavior of phosphate bound was studied at pH 7 and 25 °C. The mechanism of the phosphate release from P-CMS-g-PAM was examined using the Korsmeyer-Peppas model.

PH and thermal-dependent ultrafiltration membranes prepared from poly (methacrylic acid) grafted onto polyethersulfone synthesized by simultaneous irradiation in homogenous phase

Polyethersulfone (PES) and monomer methacrylic acid (MAA) were chosen to synthesize the grafted polymer PES-g-PMAA by simultaneous γ-ray irradiation in homogenous phase. Membranes prepared from pristine PES and PES-g-PMAA with different degrees of grafting (DGs), have been obtained. The kinetics of grafting reaction and the DG values were studied through sulphur elemental analysis. The morphology study of the membranes showed formation of sponge-like structure in the sub-layer of membrane, along with grafting PMAA onto the PES chains. By ultrafiltration experiments, a regular pH-dependent permeability and thermal-dependent permeability of PES-g-PMAA membranes was demonstrated through introduction of PMAA onto the PES which reduced the water flux of the membranes. The pH-dependent permeability could be attributed to pH-sensitive reconfiguration of PMAA molecule chains on the surface of membrane pore, while thermal-dependent permeability might be caused by better thermal-sensibility of PMAA chains inside the membrane.

Styrene-assisted grafting of maleic anhydride onto deproteinized natural rubber

Grafting of maleic anhydride (MA) onto deproteinized natural rubber (DPNR) was carried out using a differential microemulsion polymerization technique. To improve the grafting efficiency (G.E) and reduce the gel content in the grafts, deproteinizing the NR latex was conducted before the grafting reaction and styrene (ST) comonomer was used to increase the G.E. The effects of initiator and monomer concentration, reaction temperature, reaction time, monomer addition rate, and ST/MA ratio on G.E and gel content were investigated. Kinetics of grafting reaction in either the presence or absence of ST was investigated. The results showed that introduction of copolymerizing styrene could significantly improve both the G.E and the grafting content. The G.E increased with increasing ST/MA ratio. The optimal grafting condition was initiator and MA concentrations of 7wt% and 9wt% of dried rubber content, ST/MA mole ratio of 4:1, and MA addition rate of 0.6ml/min at 60°C for 4h. The addition of styrene to the grafting process enhances the graft copolymerization rate of MA grafting onto DPNR.

Free-radical kinetics of grafting reactions for creating novel graft copolymers in emulsion polymerization

The polymerization of vinyl neo-decanoate in the presence of polybutadiene has been studied. The rate of transfer to polymer has been determined, and has been found to be very high, resulting in the formation of a highly grafted copolymer.

Mechanism and grafting reactions in seeded emulsion polymerization with emulsified monomer feeding

The seeded emulsion polymerization of styrene with emulsified monomer feeding was performed by polyethyl acrylate (PEA) latex as seed emulsion. It was shown that the grafting reactions occurred between two components on the composite latex particles. The loci of seeded polymerization were studied by the kinetics of grafting reaction. The highest grafting efficiency in the initial period of seeded emulsion polymerization supported the fact that the surfaces of PEA particles are the sites of polymerization of styrene. The grafting efficiency decreased with increasing monomer-to-polymer ratio and initiator concentration. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 72: 1495–1499, 1999