Microwave induced synthesis of graft copolymer of binary vinyl monomer mixtures onto delignified Grewia optiva fiber: application in dye removal.

Vinod Kumar Gupta,Gaurav Sharma,Bhanu Priya,Deepak Pathania,Amar Singh Singha

doi:10.3389/fchem.2014.00059

Vinod Kumar Gupta, Gaurav Sharma + Show 3 more

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https://doi.org/10.3389/fchem.2014.00059

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Abstract

Grafting method, through microwave radiation technique is very effective in terms of time consumption, cost effectiveness and environmental friendliness. Via this method, delignified Grewia optiva identified as a waste biomass, was graft copolymerized with methylmethacrylate (MMA) as an principal monomer in a binary mixture of ethyl methacrylate (EMA) and ethyl acrylate (EA) under microwave irradiation (MWR) using ascorbic acid/H2O2 as an initiator system. The concentration of the comonomer was optimized to maximize the graft yield with respect to the primary monomer. Maximum graft yield (86.32%) was found for dGo-poly(MMA-co-EA) binary mixture as compared to other synthesized copolymer. The experimental results inferred that the optimal concentrations for the comonomers to the optimized primary monomer was observed to be 3.19 mol/L × 10−1 for EMA and 2.76 mol/L × 10−1 for EA. Delignified and graft copolymerized fiber were subjected to evaluation of physicochemical properties such as swelling behavior and chemical resistance. The synthesized graft copolymers were characterized with Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), thermogravimetric analysis (TGA) and X-ray diffraction techniques. Thermal stability of dGo-poly(MMA-co-EA) was found to be more as compared to the delignified Grewia optiva fiber and other graft copolymers. Although the grafting technique was found to decrease percentage crystallinity and crystallinity index among the graft copolymers but there was significant increase in their acid/base and thermal resistance properties. The grafted samples have been explored for the adsorption of hazardous methylene dye from aqueous system.

Highlights

Natural biomasses such as natural fibers are utilized by humans for household or other conventional applications (Necula et al, 2010; Ramanaiah et al, 2011a; Sharma et al, 2013)
microwave irradiation (MWR) produces free radicals on polymeric backbone and monomer, which can be explained through the following mechanism: Table 1 | Evaluation of optimum reaction parameter for grafting of binary vinyl monomer mixture onto delignified Grewia optiva fiber
On the other hand r1 values clearly indicate the formation of a copolymer between the different monomers in the binary mixtures, which suppresses the formation of principal monomer homopolymerization, which resulting in higher graft yields

Summary

Introduction

Natural biomasses such as natural fibers are utilized by humans for household or other conventional applications (Necula et al, 2010; Ramanaiah et al, 2011a; Sharma et al, 2013). The wider applicability of natural fibers has been due to the exhibition of diverse properties like low density, low health hazards, biodegradability, better wear resistance, and a high degree of flexibility, low cost, renewability, and high specific strength. These fibers have been found to be sensitive to moisture, chemicals, water, and their properties are degraded when they come in contact with harsh environmental conditions. Graft copolymerization of binary mixtures of vinyl monomers has special importance in comparison to simple grafting of individual monomers This technique of grafting of monomer mixtures has the advantage of creating grafted chains with tailor made properties for specific applications. The synergistic effect of the comonomers in grafting mixtures plays an important role in controlling the composition and graft yield onto cellulose (Singha et al, 2013; Thakur et al, 2014)

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