Rajesh D. Anandjiwala

Flammability of Natural Fiber-reinforced Composites and Strategies for Fire Retardancy: A Review

Natural fiber-reinforced composites are finding new applications in many sectors. In certain industries, such as building and transport, reduced material flammability is a key requirement. Knowledge of the flammability of natural fiber-reinforced composites and the methods used to improve their fire resistance is necessary to ensure their use in these industries. The purpose of this review is to examine important aspects of the flammability of natural fiber-reinforced composites and to outline some of the more recent strategies used to improve their fire performance.

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.

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.

Development of Needle-punched Nonwoven Fabrics from Flax Fibers for Air Filtration Applications

This paper reports an exploratory study on the production and measurement of the air permeability, mechanical properties, pore size distribution and filtration efficiency of different nonwoven fabrics produced by systematically changing the machine variables to influence the physical parameters of the fabrics. Only flax fiber waste was utilized for this trial, so that the possibility of value addition to a cheap source of raw material could be explored. The changes in air permeability were interpreted in terms of fabric density profile and pore size distribution. The tensile strength, fiber orientation distribution and bond strength between the layers of multi-layered fabrics were investigated. The filtration parameters, such as filtration efficiency, dust holding capacity and pressure drop, were evaluated. Furthermore, the effect of calendering on pore size and filtration properties was evaluated to explore the possibility of fine-tuning the performance of filters. The results in this study showed an overall improvement in all filtration characteristics due to the calendering operation.

Composites from Bast Fibres-Prospects and Potential in the Changing Market Environment

Abstract Composite materials reinforced with natural fibres, such as flax, hemp, kenaf and jute, are gaining increasing importance in automotive, aerospace, packaging and other industrial applications due to their lighter weight, competitive specific strength and stiffness, improved energy recovery, carbon dioxide sequestration, ease and flexibility of manufacturing and environmental friendliness besides the benefit of the renewable resources of bast fibres. The market scenario for composite applications is changing due to the introduction of newer biodegradable polymers, such as PLA synthesized from corn, development of composite making techniques and new stringent environmental laws requiring improved recyclability or biodegradability for industrial applications where stress bearing capacities and micro-mechanical failures dictate serviceability. Bast fibre reinforced composites, made from biodegradable polymers, will have to compete with conventional composites in terms of their mechanical behaviour. Biocomposites, in which natural fibres, such as kenaf, jute, flax, hemp, sisal, corn stalk, bagasse or even grass are embedded in a biodegradable matrix, made as bioplastics from soybean, corn and sugar, have openedup new possibilities for applications in automotive and building products. Obviously, new approaches to research and development will be required to improve their mechanical properties, such as tensile, bending and impact resistance to match their performance and commercial competitiveness against petroleum based products. The research community has to look at the various possibilities of combining natural fibres, such as sisal, flax, hemp and jute with polymer matrices from non-renewable and renewable resources to develop cost effective biocomposites. This paper will review the newer products and techniques that can improve the properties of bast fibre based composites as well as potential structural and non-structural applications which can increase their market share.

Tensile Fatigue Behavior of Staple Yarns

The failure of warp yarns on a loom is often caused by repeated cyclical elongation at small stresses well below the breaking point applied under static load. The phenom enon, commonly known as fatigue, is caused by the gradually diminishing resistance of the material, attributable to cumulative damage. Generally, there is no prior indi cation of impending failure due to fatigue. In this work, we have studied the fatigue behavior of warp yarn under cyclical elongation accompanied by abrasion action as measured on a Sulzer-Ruti Webtester on the basis of three criteria—failure, damage rate, and visual appearance. Fatigue behavior expressed in terms of cycles at failure exhibits a wide scatter, displaying a pattern that deviates from normal distribution. A three-parameter Weibull distribution fitted to experimental results consistently displays a unimodal pattern. The rate of fatigue damage expressed in terms of loss in tensile property indicators has proven useful in assessing the fatigue-sustaining capacity of yarn and thereby predicting impending failure. SEM photographs display the abrasion fatigue damage inflicted on the fine structure of yarns and fibers. We have systematically studied, the effect of fatigue parameters that characterize the intensity of fatigue action, such as base tension, speed of fatiguing, abrasion pin position, and strain amplitude. Increasing intensity of fatigue action results in rapid yarn deterioration. Base tension and abrasion pin deflection have profound effects on fatigue. Fatiguing speed and strain amplitude tend to accelerate yarn deterioration, though the experimental results show a slower rate but greater variability. Representing fatigue data based on failure criterion in terms only of characteristic lifetime, which is one of the three parameters of the Weibull distribution, is not enough. A representation in terms of complete distribution yields more useful information about the extent of dispersion and the extreme value in the experimental results.

Large-Scale Extension and Recovery of Plain Woven Fabrics: Part I: Theoretical

This paper describes an attempt at a theoretical study of large-scale tensile defor mation of plain woven fabrics. The basis of the investigation is to use a more realistic approximation of nonlinear yarn bending behavior for both the undeformed fabric state and the stress analysis than has been used by most previous workers. A theoretical model is proposed for the load-extension behavior of plain woven fabric during the first cycle of loading and unloading. In order to demonstrate the possibility of extending this to include cyclic behavior, a theoretical analysis of load-extension behavior over several cycles of loading and unloading is developed.

Mechanical, thermal, and fire properties of polylactide/starch blend/clay composites

Polylactide (PLA)/starch blend/clay and PLA/clay composites are prepared by melt blending. Structural and thermal characterizations are performed by differential scanning calorimetry, X-ray diffraction analysis, and thermogravimetric analysis. The fire properties are assessed on a dual cone calorimeter. Combustion residue and char formation is characterized by optical microscopy and attenuated total reflection infrared spectroscopy. Although the clay is not fully intercalated/exfoliated, the composites exhibit a higher thermal stability and much reduced peak heat release rate, and the PLA/starch blend composite retains its mechanical properties. For the PLA/starch blend composite, smoke release is also considerably reduced. Catalyzed, oxidative decomposition is shown to occur early in the thermal decomposition of the composites, prior to increased thermal stability. The inclusion of clay promotes char formation and increases the quantity of carbonaceous char in the combustion residue. There is minimal migration of the clay to the surface prior to ignition and char is formed mainly after ignition and during burning. During the later stages of burning some of the char formed is converted to CO2.

Nanotechnology in fibrous materials–a new perspective

This issue reviews various areas where nanotechnology has come up predominately in fibrous materials, namely in electrospun polymeric nanofibers and polymer layered silicate nanocomposites. It includes synthesis, characterization, various methods of collecting nanofibers, factors affecting electrospinning, methods of increasing the productivity of the electrospinning process, and different electrospinning designs. It also covers synthesis and characterization of polymer nanocomposites. Various properties of nanocomposites are discussed. The rheological behavior and morphology of nanocomposites are covered. Different modeling and simulation methods applicable to electrospun nanofibers and polymer layered silicate nanocomposites are discussed. Some of the potential application areas of electrospun nanofibers, polymer layered silicate nanocomposites, and various products available in the market based on nanotechnology are also discussed. Some of the lacking areas and future prospects in nanofibrous structures (nanofibers and nanocomposites) are emphasized in this issue.

Relationship between Process Parameters and Properties of Multifunctional Needlepunched Geotextiles

Geotextiles are commonly produced by needlepunching technology and generally used for various civil engineering applications. Some of these applications require geotextiles to perform more than one function including separation, drainage, and filtration. In this study, the effect of process parameters, namely, feed rate, stroke frequency, and depth of needle penetration has been investigated on various properties of needlepunched geotextiles. These process parameters are then empirically related with the properties of geotextiles. Subsequently, an expert system has been developed to predict the properties of geotextiles for any desired application.