B. S. Kaith

Cellulose-Based Bio- and Nanocomposites: A Review

Cellulose macro- and nanofibers have gained increasing attention due to the high strength and stiffness, biodegradability and renewability, and their production and application in development of composites. Application of cellulose nanofibers for the development of composites is a relatively new research area. Cellulose macro- and nanofibers can be used as reinforcement in composite materials because of enhanced mechanical, thermal, and biodegradation properties of composites. Cellulose fibers are hydrophilic in nature, so it becomes necessary to increase their surface roughness for the development of composites with enhanced properties. In the present paper, we have reviewed the surface modification of cellulose fibers by various methods. Processing methods, properties, and various applications of nanocellulose and cellulosic composites are also discussed in this paper.

Synthesis and Characterization of Graft Co-Polymers of Flax Fiber with Binary Vinyl Monomers

Abstract Grafting of flax fiber with binary vinyl monomer mixtures such as methylmethacrylate (MMA)/ethyl acrylate (EA), MMA/acrylonitrile (AN), and MMA/acrylic acid (AA) was carried out. At a pressure of 8 Kg/cm2 under optimum reaction conditions 41.74% grafting resulted. Maximum grafting (109.9%) was found with MMA + EA binary monomer mixture. Synthesized graft co-polymers were characterized with FT-IR spectroscopy, scanning electron microscopy (SEM), TGA/DTA techniques, and X-ray diffraction (XRD). Thermal stability of flax-g-poly(MMA/AA) was found to more than that of flax fiber and other graft co-polymers. On grafting, percentage crystallinity decreases rapidly with reduction in its stiffness and hardness. Flax fiber showed the highest value of percentage crystallinity (76.96 %) and crystallinity index (0.7005) in comparison to flax-g-co-polymers.

Evaluation of optimum grafting parameters and the effect of ceric ion initiated grafting of methyl methacrylate on to jute fibre on the kinetics of thermal degradation and swelling behaviour

Abstract To effect useful changes in jute fibre, we graft copolymerized with methyl methacrylate (MMA) initiated by ceric ions and studied optimization of grafting parameters as a function of various reaction conditions. Jute and its graft copolymer thermally degrade in one and two stages, respectively, but follow the same degradation mechanism. The degradation mechanism and thermal kinetics were evaluated by applying seven kinetic degradation models. Both fibres decompose following the R-2 (PBR-cylindrical symmetry) kinetic equation. Initially, the thermal stability of the graft copolymer is better, as evident from higher energy of activation ( E act ) and higher initial decomposition temperature (IDT). Swelling ( P s) of graft copolymers increases as a function of grafting and at a particular graft level follows the order: DMF>H 2 0>iso-propanol.

Mercerization of Flax Fiber Improves the Mechanical Properties of Fiber-Reinforced Composites

In this article, modification of mercerized flax (MFx) through graft co-polymerization with methylmethacrylate (MMA) using ferrous ammonium sulphate–potassium per sulphate (FAS–KPS) redox initiator has been reported. Water uptake and moisture absorbance properties of methylmethacrylate grafted mercerized flax (MFx-g-MMA) and mechanical behavior of raw flax, mercerized flax, and MFx-g-MMA fibers reinforced—polystyrene matrix–based composites also have been evaluated. Four reaction parameters, reaction temperature, reaction time, initiator molar ratio, and monomer concentration, have been optimized to get maximum graft yield. Maximum graft yield of 138.35% has been obtained at optimum reaction conditions. The graft co-polymers thus formed were characterized by FTIR, TGA, and SEM techniques. Mercerized flax fiber reinforced showed better results than raw flax and MFx-g-MMA fibers reinforced composites.

Flocculation and adsorption properties of biodegradable gum-ghatti-grafted poly(acrylamide-co-methacrylic acid) hydrogels.

This study reports the microwave-assisted synthesis of gum-ghatti (Gg)-grafted poly(acrylamide-co-methacrylic acid) (AAm-co-MAA) hydrogels for the development of biodegradable flocculants and adsorbents. The synthesized hydrogels were characterized using TGA, FTIR and SEM. TGA studies revealed that the synthesized hydrogels were thermally more stable than pristine Gg and exhibited maximum swelling capacity of 1959% at 60°C in neutral pH. The optimal Gg-cl-P(AAm-co-MAA) hydrogel was successfully employed for the removal of saline water from various petroleum fraction-saline emulsions. The maximum flocculation efficiency was achieved in an acidic clay suspension with a 15 mg polymer dose at 40°C. Moreover, the synthesized hydrogel adsorbed 94% and 75% of Pb(2+) and Cu(2+), respectively, from aqueous solutions. Finally, the Gg-cl-P(AAm-co-MAA) hydrogel could be degraded completely within 50 days. In summary, the Gg-cl-P(AAm-co-MAA) hydrogel was demonstrated to have potential for use as flocculants and heavy metal absorbents for industrial waste water treatment.

Biodegradable and conducting hydrogels based on Guar gum polysaccharide for antibacterial and dye removal applications

Conducting hydrogels possessing antibacterial activity were developed using a two-step free-radical aqueous polymerization method to incorporate polyaniline chains into an adsorbent Guar gum/acrylic acid hydrogel network. The material properties of the synthesized samples were characterized using FTIR spectroscopy, thermal analysis and scanning electron microscopy techniques. Conducting hydrogels were tested for antibacterial activities against gram-positive Staphylococcus aureus and gram-negative Escherichia coli bacteria and demonstrated antibacterial activity. Synthesized hydrogel samples can be potential adsorbent materials for dye removal applications.

Synthesis and properties of poly(acrylamide-aniline)-grafted gum ghatti based nanospikes

In this work, we have synthesized poly(acrylamide-aniline)-grafted gum ghatti based crosslinked conducting hydrogel via a two-step synthesis method. The first step involved the microwave assisted synthesis of a semi-interpenetrating polymer network (semi-IPN) based on acrylamide and gum ghatti using N,N′-methylene-bis-acrylamide and ammonium persulfate as a crosslinker-initiator system. The semi-IPN has been observed to exhibit as much as 2183% swelling in aqueous solution. The effect of several variables such as time, solvent, pH, microwave power, crosslinker amount, aniline concentration, initiator concentration and monomer concentration on the swelling capacity was explored. In the final step, polyaniline was entrapped within a semi-IPN (optimized reaction condition) followed by doping with hydrochloric acid, which leads to the formation of conducting IPN. The synthesized hydrogels, as monitored by the swelling behaviour were characterized by Fourier transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy and thermogravimetric analysis. Finally, the synthesized crosslinked networks have been used in malachite green (MG) adsorption. The result indicates that IPN of poly(acrylamide-aniline)-grafted gum ghatti are potential candidates for dye removal from water.

Screening and RSM optimization for synthesis of a Gum tragacanth–acrylic acid based device for in situ controlled cetirizine dihydrochloride release

The present research work was aimed at the development and optimization of a Gum tragacanth–acrylic acid based hydrogel for in situ release of cetirizine dihydrochloride under different pH conditions such as 2.0, 7.0 and 9.2 at 37 °C. Various process variables like solvent, temperature, pH, treatment time, initiator molar ratio, concentration of monomer and cross-linker were screened using a fractional factorial design approach. Using a half normality plot, the most significant parameters for maximizing swelling are found. These significant parameters (solvent, pH and monomer) are further optimized using center composite design. The ANOVA model predicted that the interaction between pH and monomer concentration had an antagonistic effect on percentage swelling. The sequential experimental design approach was able to optimize the reaction parameters for getting the candidate polymer with maximum swelling capacity, thereby maximizing water absorption capacity by fivefold. Characterization of the candidate hydrogel Gt-cl-poly(AA) was done using FTIR and SEM techniques. The candidate polymer with maximum water absorption capacity was found to exhibit maximum drug absorption which later on was released in a Case II diffusion manner at pH 2.0 and 7.0. However, a non-Fickian mechanism was exhibited at pH 9.2. The hydrogel has been found to show colon specific release behavior of the drug. The initial diffusion coefficient has a greater value than the later diffusion coefficient indicating a higher drug release rate during the early stage.

Synthesis and flocculation properties of gum ghatti and poly (acrylamide-co-acrylonitrile) based biodegradable hydrogels

This article reports the development of biodegradable flocculants based on graft co-polymers of gum ghatti (Gg) and a mixture of acrylamide and acrylonitrile co-monomers (AAm-co-AN). The hydrogel polymer exhibited an excellent swelling capacity of 921% in neutral medium at 60°C. The polymer was used to remove saline water from various petroleum fraction-saline water emulsions. The flocculation characteristics of the hydrogel polymer were studied in turbid kaolin solution as a function of the amount of polymer and the solution temperature and pH. Biodegradation studies of hydrogel polymer were conducted using the soil composting method, and the degradation process was constantly monitored using scanning electron microscopy and Fourier transform infrared spectroscopy techniques. The results demonstrated an 89.47% degradation of the polymer after 60 days. Finally, the hydrogel polymer adsorbed 98% of cationic dyes from the aqueous solutions.

Response surface methodology and optimized synthesis of guar gum-based hydrogels with enhanced swelling capacity

Guar gum based hydrogel was optimally synthesized using a response surface methodology (RSM) approach for enhanced swelling capacity. Maximization of the water absorption capacity of the synthesized hydrogel was achieved through sequential experimental design based optimization. A fractional factorial screening (Resolution-IV) approach was used to screen significant process variables for maximization of percentage swelling in phase-1. Studied reaction parameters were: (i) monomer concentration, (ii) initiator concentration, (iii) cross linker concentration, (iv) polymerization time, (v) reaction temperature, (vi) vacuum level, and (vii) pH of reaction mixture. A Pareto chart indicated monomer concentration, pH and initiator concentration as significant process variables which were further optimized using full factorial design (23) in phase-2. RSM based center composite design (CCD) was applied to maximize the percentage swelling for the two most significant variables (pH and initiator concentration) in phase-3. Statistical modeling using ANOVA predicted a near neutral range for pH (∼7.0) and an initiator concentration of 21–23 × 10−6 mol L−1 as optimum operating conditions for maximizing the percentage of swelling (5307%). Hydrogels were found to be highly pH sensitive and should be kept in a narrow range for maximization of percentage swelling. Thus, the sequential experimental design was helpful in achieving two fold increases in percentage swelling in a systematic way. Synthesized super absorbent polymers can be used as effective water-saving materials for horticultural and agricultural applications.