Maya Jacob John

Electrospun chitosan-based nanocomposite mats reinforced with chitin nanocrystals for wound dressing

The aim of this study was to develop electrospun chitosan/polyethylene oxide-based randomly oriented fiber mats reinforced with chitin nanocrystals (ChNC) for wound dressing. Microscopy studies showed porous mats of smooth and beadless fibers with diameters between 223 and 966 nm. The addition of chitin nanocrystals as well as crosslinking had a positive impact on the mechanical properties of the mats, and the crosslinked nanocomposite mats with a tensile strength of 64.9 MPa and modulus of 10.2 GPa were considered the best candidate for wound dressing application. The high surface area of the mats (35 m(2)g(-1)) was also considered beneficial for wound healing. The water vapor transmission rate of the prepared mats was between 1290 and 1,548 gm(-2)day(-1), and was in the range for injured skin or wounds. The electrospun fiber mats showed compatibility toward adipose derived stem cells, further confirming their potential use as wound dressing materials.

Environmental friendly method for the extraction of coir fibre and isolation of nanofibre.

The objective of this work was to develop an environmental friendly method for the effective utilization of coir fibre by adopting steam pre-treatment. The retting of the coconut bunch makes strong environmental problems which can be avoided by this method. Chemical characterization of the fibre during each processing stages confirmed the increase of cellulose content from raw (40%) to final steam treated fibres (93%). Morphological and dynamic light scattering analyses of the fibres at different processing stages revealed that the isolation of cellulose nano fibres occur in the final step of the process as an aqueous suspension. FT-IR and XRD analysis demonstrated that the treatments lead to the gradual removal of lignin and hemicelluloses from the fibres. The existence of strong lignin-cellulose complex in the raw coir fibre is proved by its enhanced thermal stability. Steam explosion has been proved to be a green method to expand the application areas of coir fibre.

Review on flammability of biofibres and biocomposites

The subject on flammability properties of natural fibre-reinforced biopolymer composites has not been broadly researched. This is not only evidenced by the minimal use of biopolymer composites and/or blends in different engineering areas where fire risk and hazard to both human and structures is of critical concern, but also the limited amount of published scientific work on the subject. Therefore, it is necessary to expand knowledge on the flammability properties of biopolymers and add value in widening the range of their application. This paper reviews the literature on the recent developments on flammability studies of bio-fibres, biopolymers and natural fibre-reinforced biocomposites. It also covers the different types of flame retardants (FRs) used and their mechanisms, and discusses the principles and methodology of various flammability testing techniques.

Physicomechanical properties of nanocomposites based on cellulose nanofibre and natural rubber latex

Cellulose nanofibres (CNF) with diameter 10–60 nm were isolated from raw banana fibres by steam explosion process. These CNF were used as reinforcing elements in natural rubber (NR) latex along with cross linking agents to prepare nanocomposite films. The effect of CNF loading on the mechanical and dynamic mechanical (DMA) properties of NR/CNF nanocomposite was studied. The morphological, crystallographic and spectroscopic changes were also analyzed. Significant improvement of Young’s modulus and tensile strength was observed as a result of addition of CNF to the rubber matrix especially at higher CNF loading. DMA showed a change in the storage modulus of the rubber matrix upon addition of CNF which proves the reinforcing effect of CNF in the NR latex. A mechanism is suggested for the introduction of the Zn–cellulose complex and its three dimensional network as a result of the reaction between the cellulose and the Zinc metal which is originated during the composite formation.

A comparative study on properties of micro and nanopapers produced from cellulose and cellulose nanofibres.

Cellulose nanocrystals (CNCs) and cellulose nanofibres (CNFs) were successfully extracted from cellulose obtained from maize stalk residues. A variety of techniques, such as Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), X-ray diffraction (XRD) and thermogravimetric analysis (TGA) were used for characterization and the experimental results showed that lignin and hemicellulose were removed to a greater extent by following the chemical methods. Atomic force microscopy (AFM) results confirmed that the diameters of CNCs and CNFs were ranging from 3 to 7 nm and 4 to 10nm, respectively, with their lengths in micro scale. CNCs suspension showed a flow of birefringence, however, the same was not observed in the case of suspension containing CNFs. XRD analysis confirmed that CNCs had high crystallinity index in comparison to cellulose and CNFs. Nanopapers were prepared from CNCs and CNFs by solvent evaporation method. Micropapers were also prepared from cellulose pulp by the same technique. Nanopapers made from CNFs showed less transparency as compared to nanopapers produced from CNCs whereas high transparency as compared to micropaper. Nanopapers produced from CNFs provided superior mechanical properties as compared to both micropaper and nanopapers produced from CNCs. Also, nanopapers produced from CNFs were thermally more stable as compared to nanopapers produced from CNCs but thermally less stable as compared to micropapers.

Review on hygroscopic aging of cellulose fibres and their biocomposites.

This review presents critical literature on effects of humidity and temperature on the properties of natural fibres and its composites. The drawback of moisture absorption on the mechanical properties of natural fibre and its composites is evaluated. Numerous researchers have been working to address the moisture absorption issue, with specific attention paid to the surface treatment of fibres and refining the fibre-matrix interface. Because of the natural fibres positive commercial and environmental outcomes, as well as their desirable properties such as high specific strength, natural fibre reinforced composites are displaying a good potential to be used in various applications such as automotive, aerospace and packaging. This review addresses a comprehensive survey on hygroscopic factors (long term environmental aging) affecting natural fibres and their performance as reinforcement in polymer composites. The effects of cellulose surface chemistry and topography on hydrophobicity are addressed. Furthermore, the review also addresses the progress in the development of superhydrophobic materials based on cellulose material for better moisture resistance. In addition, recent investigations dealing with bio-based coatings prepared from renewable resources are also discussed.

Dynamic Mechanical and Dielectric Behavior of Banana/glass Hybrid Fiber Reinforced Polyester Composites

Hybrid composites of glass and banana fiber (obtained from the pseudo stem of Musa sapientum) in polyester matrix, are subjected to dynamic mechanical analysis over a range of temperature and three different frequencies. The effect of temperature on the storage modulus (E′), loss modulus (E′′), and loss factor or damping efficiency (tan δ) is determined. All the properties are compared with those of the neat polyester samples and the un-hybridized composites. The effects of the layering pattern of the two fibers on the ultimate viscoelastic behavior of the composites are also investigated. Composites are prepared with banana as the surface layer and glass as the surface layer and also as an intimate mixture of glass and banana. At temperatures above T g,, the storage modulus values are found to decrease even with the addition of glass fiber for the geometry where glass is the core material. The value of the storage modulus of the composites with the above mentioned geometry is found to be different, above and below Tg, the value above Tg being lower than that below Tg unlike in unhybridized composite. The loss modulus curves and the damping peaks are found to be flattened by the addition of glass. Layering pattern or the geometry of the composites is found to have a profound effect on the dynamic properties of the composite. An intimately mixed composite is found to have the highest storage modulus values in all compositions. The values are consistent with the results of tensile strength. The tan δ curve is found to be affected by the layering pattern followed and gives insight into the interaction in the material. The dielectric behavior of the composites are also found to be dependent on the glass fiber volume fraction as well as the layering pattern employed.

Green Composites from Natural Fibers and Natural Rubber: Effect of Fiber Ratio on Mechanical and Swelling Characteristics

ABSTRACT Sisal and oil palm fibers were incorporated into a natural rubber matrix, and the influence of fiber ratio on the cure and tensile properties of hybrid fiber-reinforced natural rubber composites were analyzed. Tensile strength and modulus was found to decrease with the loading of oil palm fiber. Longitudinally oriented composites showed better mechanical properties than transversely oriented composites. Maximum torque values were found to increase with oil palm fibers content. A positive hybrid effect was observed for the tensile properties. Anisotropic swelling experiments were performed to determine the extent of fiber/matrix interaction.

Cellulosic fibre-reinforced green composites

Increased environmental awareness and societal needs serve as a catalyst for developing new eco-friendly materials like green composites. In the recent past, researchers have reported the results of their studies on green composites of different plant fibres and various biodegradable matrices. This article is an overview of the various aspects of green composites. Composites based on important biodegradable matrices like rubber, poly (lactic acid), poly(butylene succinate), poly(hydroxybutanoate) and soy-based matrices have been discussed. Special emphasis has been given to natural rubber-based green composites.

Bio-based products from xylan: A review

Obtaining chemicals and materials in sustainable ways is of growing importance. A potential source of sustainable chemicals and materials is lignocellulosic biomass residues generated as waste from agriculture. Hemicellulose which is a large component in lignocellulosic biomass residues, provides many potential applications such as the generation of chemicals, packaging materials, drug delivery and biomedical applications. This review deals with the various techniques which can be used for the extraction of hemicellulose from biomass residues, purification and some potential applications of the extracted hemicellulose. The methods that have been used to further produce chemicals from extracted hemicellulose as well as their applications are discussed.