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Abstract: Aerogels, in recent times, have become materials of extensive research due to their fascinating capabilities in different fields. High porosity, large surface area, low thermal conductivity and low density make them significant in fields such as medicine, environmental engineering, food packaging, and so on. Biodegradability, low toxicity and biocompatibility, in addition to the aforementioned properties, offered by bio-based aerogels, especially polysaccharide based aerogels, give them a huge advantage over conventional inorganic ones. Polysaccharide based aerogels synthesised from starch, cellulose, pectin, alginate, chitosan, carrageenan and agarose precursors enable sustainable developments in the biomedical, cosmetic, electronic, construction and food industries. This review focuses on the biomedical applications of polysaccharide based aerogels, with special emphasis on its implications in drug delivery, tissue engineering, medical implantable devices, wound dressing, biosensors and bio-imaging. The future perspectives of these smart materials have also been subjected to discussion.

Environmental concerns and increasing awareness about sustainability issues are driving the push to develop bio-based composites from renewable and sustainable resources. A clear understanding of fiber-matrix interaction at the interfaces is vital for the design and production of these composite materials because stress transfer between load-bearing fibers occurs at these interfaces, and this can determine their mechanical and thermal behaviors. A detailed study of different attributes such as processing technology parameters, types of biopolymers, and chemical and physical treatments is essential to effect interface modification and facilitate a better understanding of these composites from an application perspective. In this article, we attempt to critically review adhesion in biocomposites with special emphasis on the effects of various surface modifications and the processing technology adopted. The review also addresses various characterization techniques adopted for evaluating adhesion in biocomposites.

Banana fibers are an agricultural waste material with a great exploitation potential due to their cellulose-rich content. Raw banana fibers (RBF) were treated with 3-aminopropyltriethoxy silane and glycidoxypropyltrimethoxy silane to improve the inherent limitations of banana fibers, namely its poor cell adhesion. The fibers’ modification was evaluated by inverse gas chromatography (IGC). Similar γ values were observed between the RBF and silane-treated fibers (39–41 mJ/m2), which indicates similar reactivity towards apolar probes. However, the decrease in the entropic parameter indicates the silane covalent bonding with the cellulose chains making a stiffer structure. Organosilane grafting was confirmed by an increased basic character in the silane-treated fibers (Kb/Ka from 1.03 to 2.81). The surface morphology also changed towards higher contact area (SBET increases 6.7 times) and porosity (Dp increases up to 67%). Both morphological and functional group reactivity changes suggest that the organosilane treatment offers new opportunities for these fibers to be used as adsorbents for proteins as well as to cell adhesion. Therefore, IGC proved a simple and viable technique in the characterization of silane-treated fibers.

Aerogels are comprised of a distinct class of nanostructured materials with superior porosity and physicochemical properties that can be attuned and are composed of a clustered nanoparticle network. While a few types of aerogels have already entered the market in building products, fabrics, and aerospace engineering, their complete scope for other manufacturing industries needs to be measured. While they integrate the attributes of strongly separated solids with macroscopic morphology, they establish rather remarkable physical and chemical characteristics, thereby creating a new family of solids exhibiting versatile prospects for a wide variety of applications. The formulation choice of the aerogel is of paramount importance for inculcating innovative features to the content. Biobased aerogels, specifically nanocellulosic aerogels, are rather “smart” materials which provide fascinating properties at the interface of various materials. These natural resources are ample and affordable, rendering them economical and viable for aerogel preparation, while also tackling waste management concerns. Based on currently available knowledge, this chapter discusses key advances in the field of nanocellulose-based aerogels and foams. It mainly deals with different processing techniques, structure, morphology, analysing tools, inherent properties, and various applications of nanocellulosic aerogels.

Biodegradable colourimetric films incorporating anthocyanins which can respond to food spoilage is a novel and green development in packaging field. However, when it comes to commercial applications, these biodegradable matrices lack sufficient mechanical strength and water resistivity. Hence nanomaterials are being incorporated into the matrix to improve its properties. The aim of this work was to develop intelligent starch based biopolymer film by incorporating carbon dot (CD) and anthocyanin extracted from clitoria ternatea flower (CTE). The starch/CD/CTE film (SED) was prepared by solution casting technique and characterised as novel, high sensitive, pH indicator film having the potential to monitor the freshness of packed pork. SEM, FTIR and XRD analysis showed homogenous distribution of CD and CTE in starch matrix. SED films exhibited highest mechanical, barrier, thermal and antioxidant properties due to synergistic effect of CD and CTE. Besides, SED films exhibited colour variations in different pH due to the presence of anthocyanin in CTE. Hence SED film was used as a low cost visual indicator for monitoring freshness of packed pork sample. The film showed visual colour changes from purple to green as storage time increased. This study shows that food grade ingredients can be used to prepare active smart films which can in turn be used to monitor the freshness of food product like pork.

Researchers and scientists working on the development of functional and high-performance materials usually turn to naturally occurring sources with hierarchical organization because of their availability, renewability, biocompatibility, flexibility, biodegradability, and availability of multiple reactive sites for introducing novel functionalities. Nanoscale materials based on lignocellulosic fibers get huge attention in the research field because of these reasons. This chapter points out the principal sources of cellulose, the main processes used for their extraction, strategies used for the extraction of nanocellulose, their properties and characteristics, and the applications of nanocellulose based bionanocomposites.

International audience; Natural rubber (NR)/carbon nanotube (CNT) composites containing ionic liquid (IL) at different concentrations have been prepared by using an internal mixer in the conventional mechanical mixing method. The role of a green solvent IL 1-butyl-3-methyl imidazolium chloride (BMIC) on the curing kinetics, mechanical, morphological and thermal properties of NR-CNT composites has been studied. It has been found that BMIC strongly influenced rheometric data and mechanical properties. The addition of the IL (1-ethyl-3-mehylimidazolium chloride) significantly increased the vulcanization rate, decreased scorch and cure times. The plasticizing effect of IL on the composite is well understood from the results of different analysis. The increment in the free volume of the nanocomposites by the effect of IL was studied using positron annihilation lifetime spectroscopy. The mechanical properties such as tensile strength and elongation at break increased with small amount of IL. With high amount of IL, tensile strength and elongation at break decreased due to plasticizing effects, contributing towards retarding the strain-induced crystallization in NR/CNT/IL composites. Differential scanning calorimetry analysis was done and the improvement in dispersion of the CNTs by the addition of IL has been investigated through transmission electron microscopy analysis.

The main disadvantages of the biodegradable polymers towards a wide range of applications are their poor mechanical and thermal resistance as well as barrier properties. It can be overcome by the use of biopolymers as the fillers, which enhance the biodegradability also. This chapter outlines the improvement in various properties achieved by composites after reinforcement.

The bio based or biopolymer based material are of great interest because of their sustainability, eco-efficiency, and wide range of applications, are lead to the development of the next generation of materials. The combination biopolymer with several polymer matrices produces composite materials that are competitive with synthetic composites and used in wide range of applications. This chapter outlines the various applications of the biopolymer reinforced composites such as packaging, water treatment and biomedical applications.

Starch, as an agro-sourced polymer, has received much attention recently due to its strong advantages such as low cost, wide availability, and biodegradability. In this chapter the different steps in the processing of starch based aerogels are discussed. We also focus on the morphological properties by discussing the porosity and SEM analysis of starch aerogels.

One of the most attractive advantages of bio-based polymers is their excellent biodegradability. Polysaccharide/protein-based aerogels accomplish the biodegradability that silica aerogel lacks and hence have received considerable attention from both academic and industrial researchers over the past decade. The rate of degradation of these bio-based aerogels depends upon its crystallinity and porosity, and unlike polysaccharide aerogels, protein-based aerogels composites exhibit relatively low degradation rates compared with their solid counterparts. This chapter gives an overview of the degradation behaviour of different bio-based aerogels, the knowledge of which will reduce landfill and hence environmental pollution.

Since the conception of aerogels in 1931 by Steven Kistler, they have become an advanced material of interest to scientists around the globe. Over recent years, as with other emerging materials, aerogels have taken a paradigm shift to more bio-based precursors. The underlying theme in this chapter, and in this book in general, comprises of a useful summary of the current progress and topical developments in the study of such bio-based aerogels composed of polysaccharides and proteins.

Biopolymers and biocomposites draw our attention in various applications due to their versatile properties. But the lack of good interfacial adhesion between the hydrophilic filler particles and hydrophobic polymer matrix make these composites less attractive for various applications. The use of adhesion promoters, additives or chemical modification of the filler surface can help to improve the interfacial adhesion between filler particles and polymer macromolecules and their dispersion in the matrix, and thus improve the overall mechanical performance of the composites. Interfacial adhesion between filler and matrix remains the key issue in terms of overall performance, since it influences the final properties of the composites. This review focuses on biopolymers, biomatrices, their modifications and processing techniques and characterization of interfacial modifications.

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.

Cellulose was extracted from lignocellulosic fibers and nanocrystalline cellulose (NC) prepared by alkali treatment of the fiber, steam explosion of the mercerized fiber, bleaching of the steam exploded fiber and finally acid treatment by 5% oxalic acid followed again by steam explosion. The average length and diameter of the NC were between 200-250 nm and 4–5 nm, respectively, in a monodisperse distribution. Different concentrations of the NC (0.1, 0.5, 1.0, 1.5, 2.0 and 2.5% by weight) were dispersed non-covalently into a completely bio-based thermoplastic polyurethane (TPU) derived entirely from oleic acid. The physical properties of the TPU nanocomposites were assessed by Fourier Transform Infra-Red spectroscopy (FTIR), Thermo-Gravimetric Analysis (TGA), Differential Scanning Calorimetry (DSC), X-Ray Diffraction (XRD), Dynamic Mechanical Analysis (DMA) and Mechanical Properties Analysis. The nanocomposites demonstrated enhanced stress and elongation at break and improved thermal stability compared to the neat TPU. The best results were obtained with 0.5% of NC in the TPU. The elongation at break of this sample was improved from 178% to 269% and its stress at break from 29.3 to 40.5 MPa. In this and all other samples the glass transition temperature, melting temperature and crystallization behavior were essentially unaffected. This finding suggests a potential method of increasing the strength and the elongation at break of typically brittle and weak lipid-based TPUs without alteration of the other physico-chemical properties of the polymer.

The objective of this work was to develop a simple process to obtain an aqueous stable colloid suspension of cellulose nano fibrils from various lignocellulosic fibres. For the preliminary analysis we have studied three different fibres: banana (pseudo stem), jute (stem) and pineapple leaf fibre (PALF). To study the feasibility of extracting cellulose from these raw fibres we have adopted steam explosion technique along with mild chemical treatment. These processes included usual chemical procedures such as alkaline extraction, bleaching, and acid hydrolysis but with a very mild concentration of the chemicals. The chemical constituents of the fibre in each processing step were determined by ASTM standard procedures. Morphological, spectroscopic and thermal analyses of the fibres were carried out and found that the isolation of cellulose nanofibres occurs in the final step of the processing stage and they possess improved thermal stability for various advanced nanotechnological applications.

Steam explosion process is employed for the successful extraction of cellulose nanofibrils from pineapple leaf fibres for the first time. Steam coupled acid treatment on the pineapple leaf fibres is found to be effective in the depolymerization and defibrillation of the fibre to produce nanofibrils of these fibres. The chemical constituents of the different stages of pineapple fibres undergoing treatment were analyzed according to the ASTM standards. The crystallinity of the fibres is examined from the XRD analysis. Characterization of the fibres by SEM, AFM and TEM supports the evidence for the successful isolation of nanofibrils from pineapple leaf. The developed nanocellulose promises to be a very versatile material having the wide range of biomedical applications and biotechnological applications, such as tissue engineering, drug delivery, wound dressings and medical implants.

Polypropylene (PP)/banana fiber (BF) composites were fabricated from PP fiber and short BF by novel commingling method. The dynamic mechanical analysis (DMA) of the composites was performed with reference to BF loading and fiber surface treatments. By the incorporation of BF into the PP matrix, the storage modulus and loss modulus have been found to increase, whereas damping factor has been found to decrease. Glass transition temperature was found to increase with increase in BF loading. The viscoelastic properties of the composites were also found to depend on fiber surface treatments. The activation energy of the composites for the glass transition has been found to be increased by the increase in BF loading. Surface treatment of the BF further increased the activation energy of the composites, indicating a stronger interface for treated fiber composites. Scanning electron microscopy (SEM) photographs of the BF showed the physical changes induced by the surface treatments. Fourier transform infrared spectroscopy (FTIR) was used to ascertain the existence of the type of interfacial bonds. The use of theoretical equations to predict the storage modulus has also been discussed. POLYM. ENG. SCI., 2010. © 2009 Society of Plastics Engineers

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.

Composites of woven sisal in polyester matrix using three different weave architectures: (plain, twill, and matt) were prepared using a resin transfer molding technique with special reference to the effect of resin viscosity, applied pressure, weave architecture, and fiber surface modification. More than the applied pressure, the resin viscosity, and fiber surface modification, the weave architecture was found to have maximum influence on the ultimate composite properties. The resin permeability, which is related to fiber wetting, was found to be dependent on the weave architecture and the fiber surface morphology. Sisal fibers in woven form, with a fiber volume of 32%, were found to improve the properties of polyester tremendously, irrespective of the resin used and the injection pressure. The maximum improvement in tensile strength was observed for resin with a viscosity of 420 cps. While the tensile strength showed a 32% improvement, the tensile modulus showed a 100% improvement by reinforcing fabrics with the weave architecture with maximum fibers in the loading direction, for the same resin. The flexural strength gave an improvement of 19% while the flexural modulus gave a 55% improvement. Fabrics with maximum fibers in the loading direction (matt weave) proved to be the best reinforcement to impart maximum properties. Finally, the fracture surfaces were examined by scanning electron microscopy to get an insight into fiber/matrix interactions.

Alkali treatment coupled with high pressure defibrillation and acid treatment have been tried on banana fibers obtained from the pseudo stem of the banana plant Musa sapientum. The structure and morphology of the fibers have been found to be affected on the basis of the concentration of the alkali and acid and also on the pressure applied. Steam explosion in alkaline medium followed by acidic medium is found to be effective in the depolymerization and defibrillation of the fiber to produce banana nanowhiskers. The chemical constituents of raw and steam exploded fibers were analyzed according to the ASTM standards. Structural analysis of steam exploded fibers was carried out by FTIR and XRD. The fiber diameter and percentage crystallinity of the modified fibers were investigated using X-ray diffraction studies. Characterization of the fibers by SFM and TEM supports the evidence for the development of nanofibrils of banana fibers.

Using a Dynamic Mechanical Analyzer (DMA), mechanical properties like modulus and phase transition temperature of polyester composites of banana fibers (treated and untreated) are measured simultaneously. The shifting of phase transition temperature is observed in some treatments. The performance of the composite depends to a large extent on the adhesion between polymer matrix and the reinforcement. This is often achieved by surface modification of the matrix or the filler. Banana fiber was modified chemically to achieve improved interfacial interaction between the fiber and the polyester matrix. Various silanes and alkalies were used to modify the fiber surface. Chemical modification was found to have a profound effect on the fiber/matrix interaction, which is evident from the values of phase transition temperatures. Of the various chemical treatments, simple alkali treatment with 1% NaOH was found to be the most effective.

Banana fiber obtained from the sheath of the banana plant, Musa sapientum, has been used in the preparation of composites with polyester matrix. The effect of fiber loading on the dielectric constant, volume resistivity, and dielectric loss factor of the composites were determined with special reference to the effect of frequency. The fibers were modified chemically in order to have better compatibility with the matrix. The surfaces of the modified fibers were characterized using techniques like solvatochromism, zeta potential measurements, X-ray Photo electron spectroscopy (XPS), and Scanning Electron Microscopy (SEM). The effect of fiber surface modification on the mechanical as well as electrical properties of the composites was evaluated. Fiber surface modification was found to influence both mechanical as well as electrical properties of the composite. The mechanical properties were found to be improved based on the improved interaction between the fiber and the matrix which in turn was found to be dependent on the surface polarity of the chemically modified fibers. The value of the dielectric constant was found to be influenced when the fiber loading reaches an optimum value. The dielectric constant values of the treated fiber composites were found to be lower than the untreated composites. The electrical conductivity of the composites was found to be dependent on the chemical modification as well as the fiber loading employed. Maximum conductivity was observed for composites with an optimum fiber loading of 40% as well as for those treated with methacryloxy silane. In addition to the other techniques, conductivity measurements can be used as an effective tool to evaluate interfacial adhesion in 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.

Hybridization of Banana fibers with glass fibers has been found to reduce the water absorption behavior of the composites in an earlier work by us. Banana fibers were hybridized with glass and different layering patterns were followed in the preparation of the composites. The effect of the various layering patterns on the water absorption of the composites was studied. It was found that water diffusion occurs in the composite depending on the layering pattern as well as the temperature. In all the experiments, it has been found that composites with an intimate mixture of glass and banana show the maximum water uptake except for temperature of 90°C. At 90°C the maximum water uptake is found to be for composites where there is one layer of banana and another layer of glass. The water uptake follows the same trend as that in all other temperatures till a time span of 4900 min is reached. The kinetics of diffusion was found to be Fickian in nature. The various thermodynamic parameters like sorption coefficient, diffusion coefficient. Enthalpy change, entropy change, and activation energy of the various composites were calculated. From all the calculations it has been concluded that layering pattern is an important parameter which controls the water absorption of the composites. The layering pattern Cg-b-g was found to have the lowest water uptake. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007

Corn starch nanocrystals were found to serve as an effective reinforcing agent for natural rubber (NR). Starch nanocrystals were obtained by the sulfuric acid hydrolysis of starch granules. After mixing the latex and the starch nanocrystals, the resulting aqueous suspension was made into coagulum and then it is mixed with the dry NR and cross linking agents, in two roll mill followed by compression molding. The composite samples were prepared by varying filler loadings, using a colloidal suspension of starch nanocrystals and NR latex and dry rubber. The morphology of the nanocomposites prepared was analyzed by Field Emission Scanning Electron Microscopy (FESEM) and FESEM analysis revealed the size and shape of the crystal and their homogeneity dispersion in the composites. The crystallinity of the nanocomposites was studied using XRD analysis which indicated an overall increase in crystallinity with increased in filler content. The mechanical properties of the nanocomposites such as stress-strain behaviour, tensile strength, tensile modulus and elongation at break were measured according to ASTM standards. The tensile strength and modulus of the composites were found to improve tremendously with increasing nanocrystal content. This dramatic increase observed in the modulus and the tensile strength can be attributed to the formation of starch nanocrystal network. This network immobilizes the polymer chains leading to an increase in the modulus and other mechanical properties. The DMA studies of the composites were carried out and it reveals the effective reinforcing mechanism of starch nanocrystal on NR matrix.

With the environmental appeal around the planet for a sustainable development, there is the need to develop new materials from renewable resources, which can be degraded in a short time in the environment, thereby maintaining the proper balance of the carbon cycle. Biopolymers from various natural botanical resources can act as a substitute for petroleum-based synthetic polymers because of their low cost, ease of availability, and biodegradability along with other organic wastes to soil humic materials. Materials which are biodegradable and fully sustainable are termed as “Green Composites”. This development not only solves the white pollution problem but also stops the overdependence on petroleum products. Development of Green Composites made from soy protein and starch has been a great challenge for the scientific community, since these materials do not possess all the desirable characteristics of the synthetic polymers, being mostly often, highly hydrophilic and also presenting poor mechanical properties to be used as engineering’s materials. Cellulose macro- and nano-fibers can be used as reinforcement in composite materials to enhance mechanical, thermal, and biodegradation properties of the composites. In this chapter we will be dealing mainly with the preparation, properties, and applications of cellulose fiber-reinforced green composites based on soy protein and starch.

The role of fibre/matrix interactions in chemically modified banana fibre composites were investigated using dynamic mechanical analysis and compared with those of untreated fibre composites. The dynamic modulus value and damping parameter, used to quantify interfacial interaction in composites were investigated with special reference to the effect of temperature and frequency. Increased dynamic modulus values and low damping value show the improved interactions between the fibre and the matrix. The damping peaks were found to be dependent on the nature of chemical treatment. Both storage modulus and damping values measured experimentally are consistent and point to the effectiveness of silane A174 coupling agent (γ-methacryloxypropyl trimethoxy silane) for improving fibre–matrix adhesion. Activation energy values for the transitions of the composites were determined from Arrhenius plots. Cole–cole plots were made to evaluate the heterogeneity of the system.

Banana fibers obtained from the sheath of the banana plant (Musa Sapientum) whose major constituent is cellulose were modified using various chemical agents in order to improve their compatibility with the polymer matrix. The change in the surface composition of the raw and chemically modified fiber was investigated using various techniques such as solvatochromism, electrokinetic measurements, and XPS. Surface characterization by XPS showed the presence of numerous elements on the surface of the fiber. Investigation of the surface after alkali treatment on the other hand showed the removal of most of the elements. Silane treatment was found to introduce a considerable amount of silicon on the surface of the fiber. The [O]/[C] ratio was found to decrease in all cases except for the fluorinated and vinyl silane treated fibers. Detailed investigation of the deconvoluted C 1s spectra revealed the change in the percentage atomic concentration of the various elements on the fiber surface. The dissolution of the various surface components by alkali treatment, which was earlier revealed by SEM, was further confirmed by XPS. The XPS results were found to perfectly agree with the solvatochromic and electrokinetic measurements.

The static and dynamic mechanical properties of banana and glass woven fabric-reinforced polyester composites have been determined with special reference to the effect of fiber volume fraction, layering pattern, and the weaving architecture. Even though articles related to natural fiber composites are abundant in the literature, work on natural fiber textile composites is found to be rare. Composites with high tensile strength can be obtained using banana and glass in the fabric form, using two layers of the fabric. The impact strength of the composites increases with the number of layers and the fiber volume fraction. By incorporating the fabric, the G0 curve shows an improved rubbery plateau indicating that the incorporation of the fabric induces reinforcing effects in the polyester matrix. The storage modulus has been found to be the highest for composites with four layers of the fabric. In all the composite samples, the relaxation peak of polyester is visible as peak in G00 at about 98 C. In the case of composites with four layers of the fabric, two peaks and one shoulder are seen. Increase in the number of layers made a second relaxation peak visible. The damping peaks have been found to be lowered by the incorporation of more number of layers.

This article deals with the aspects of interfacial and surface characterization of natural fibers and their composites. Vegetable fibers and their composites have attracted the attention of scientists worldwide because of their favorable properties. The different chemical modifications of natural fibers and characterization aspects have been discussed. The adhesion between fiber and matrix is a major factor in determining the response of the interface and its integrity under stress. Therefore characterization of the interface is of utmost importance. Both fiber surface and polymer matrix surface can be modified to obtain a strong interface. Various treatments being used for the lignocellulosic surfaces and the characterization techniques have been illustrated. The four main techniques of interfacial characterization that are enumerated in this article are the micromechanical techniques, spectroscopic, microscopic and swelling techniques. The micromechanical techniques like fiber pull-out and fragmentation...

The water sorption characteristics of banana fiber–reinforced polyester composites were studied by immersion in distilled water at 28, 50, 70, and 90°C. The effect of hybridization with glass fiber and the chemical modification of the fiber on the water absorption properties of the prepared composites were also evaluated. In the case of hybrid composites, water uptake decreased with increase of glass fiber content. In the case of chemically modified fiber composites, water uptake was found to be dependent on the chemical treatment done on the fiber surface. Weight change profiles of the composites at higher temperature indicated that the diffusion is close to Fickian. The water absorption showed a multistage mechanism in all cases at lower temperatures. Chemical modification was found to affect the water uptake of the composite. Among the treated composites the lowest water uptake was observed for composites treated with silane A1100. Finally, parameters like diffusion, sorption, and permeability coefficients were determined. It was observed that equilibrium water uptake is dependent on the nature of the composite and temperature. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 91: 3856–3865, 2004

Natural fibers are replacing synthetic fibers as reinforcement in various matrices. The composites so prepared can effectively be used as a substitute for wood and also in various other technical fields like automobile parts. However, to improve the adhesion between the fiber and matrix, chemical modification is suggested. The effect of chemical modification on the dynamic mechanical properties of banana fiber reinforced polyester composites has been analyzed to investigate the interfacial properties. The interfacial phenomenon in turn was found to be related to the acid base interactions involved, which occur due to the specific interactions between less reactive functional groups of each partner at the interface. The acid base interactions were investigated, by solvatochromy and the zeta potential measurements. Solvatochromy revealed that the overall polarity parameter was highest for the silane A151 (vinyl tri ethoxy silane) treated fiber, compared to other treatments. ζ-Potential measurements of the untreated and variously treated fibers also showed that the chemical modification alters the polarity of the already acidic cellulose fibers. The observations of the solvatochromic measurements and ζ-potential measurements are consistent. The results of the polarity parameters were correlated with the results of dynamic mechanical analysis. The storage modulus value was found to be the highest for the silane A151 treated fiber composite.

The dynamic mechanical analysis of banana fiber reinforced polyester composites was carried out with special reference to the effect of fiber loading, frequency and temperature. The intrinsic properties of the components, morphology of the system and the nature of interface between the phases determine the dynamic mechanical properties of the composite. At lower temperatures (in the glassy region), the E ′ values are maximum for the neat polyester whereas at temperatures above T g , the E ′ values are found to be maximum for composites with 40% fiber loading, indicating that the incorporation of banana fiber in polyester matrix induces reinforcing effects appreciably at higher temperatures. The loss modulus and damping peaks were found to be lowered by the incorporation of fiber. The height of the damping peaks depended on the fiber content. When higher fiber content of 40% was used, an additional peak in the tan δ curve, pointing to micro mechanical transitions due to the immobilized polymer layer was evident. The glass transition temperature associated with the damping peak was lowered up to a fiber content of 30%. The T g values were increased with higher fiber content. Cole–Cole analysis was made to understand the phase behavior of the composite samples. A master curve was constructed based on time–temperature super position principle, which allows the prediction of long-term effects. Apparent activation energy of the relaxation process of the composites was also analyzed. The value was found to be maximum for composites with 40% fiber content.

Changes in the surface composition of chemically treated cellulose fibres obtained from the sheath of banana plants were investigated using electrokinetic (ζ-potential) measurements. Scanning electron microscopy (SEM) was used to observe changes in the surface morphology of the fibres. Spectroscopic methods were also used to analyse the changes on the cellulose fibre surface. Chemical treatments such as alkali treatment, acetylation, treatment with a triazine coupling agent, various silanes, etc. reduced the hydrophilicity of the fibres. The surface morphology of the fibres showed considerable changes. Chemical treatments reduced the acidity of the already polar cellulose fibre. The high iso-electric point (IEP) of the silane A1100-treated fibres shows that basic groups dominate at these surfaces. The observations are consistent with the values obtained using solvatochromic measurements.

Cellulosic fibers have been used as cost-cutting fillers in plastic industry. Among the various factors, the final performance of the composite materials depends to a large extent on the adhesion between the polymer matrix and the reinforcement and therefore on the quality of the interface. To achieve optimum performance of the end product, sufficient interaction between the matrix resin and the cellulosic material is desired. This is often achieved by surface modification of the resin or the filler. Banana fiber, the cellulosic fibers obtained from the pseudo-stem of banana plant (Musa sepientum) is a bast fiber with relatively good mechanical properties. The fiber surface was modified chemically to bring about improved interfacial interaction between the fiber and the polyester matrix. Various silanes and alkali were used to modify the fiber surface. Modified surfaces were characterized by SEM and FTIR. The polarity parameters of the chemically modified fibers were investigated using the solvatochromic ...

Isolation of cellulose nanofibers from renewable resources is becoming an important area of research. The use of these novel nature-based materials has garnered interest from the scientific community because of their high strength and stiffness combined with low weight, biocompatibility, and renewability. The nanodimensions of cellulose fibrils result in a high surface area and hence the powerful interaction of these celluloses with surrounding species, such as water, organic and polymeric compounds, nanoparticles, and living cells. In this context, cellulose nanofibers from banana plant have attracted much interest due to its potential use as a reinforcing agent in novel eco-friendly nanocomposite preparation. This chapter introduces the current knowledge on the extraction of nanocellulose from banana plant and the different characterization techniques employed to understand the reinforcing potential of these nanofibers.