Propionic Anhydride Modification of Cellulosic Kenaf Fibre Enhancement with Bionanocarbon in Nanobiocomposites

The use of chemical modification of cellulosic fibre is applied in order to increase the hydrophobicity, hence improving the compatibility between the fibre and matrix bonding. In this study, the effect of propionic anhydride modification of kenaf fibre was investigated to determine the role of bionanocarbon from oil palm shell agricultural wastes in the improvement of the functional properties of bionanocomposites. The vinyl esters reinforced with unmodified and propionic anhydride modified kenaf fibres bio nanocomposites were prepared using 0, 1, 3, 5 wt% of bio-nanocarbon. Characterisation of the fabricated bionanocomposite was carried out using FESEM, TEM, FT-IR and TGA to investigate the morphological analysis, surface properties, functional and thermal analyses, respectively. Mechanical performance of bionanocomposites was evaluated according to standard methods. The chemical modification of cellulosic fibre with the incorporation of bionanocarbon in the matrix exhibited high enhancement of the tensile, flexural, and impact strengths, for approximately 63.91%, 49.61% and 54.82%, respectively. The morphological, structural and functional analyses revealed that better compatibility of the modified fibre–matrix interaction was achieved at 3% bionanocarbon loading, which indicated improved properties of the bionanocomposite. The nanocomposites exhibited high degradation temperature which signified good thermal stability properties. The improved properties of the bionanocomposite were attributed to the effect of the surface modification and bionanocarbon enhancement of the fibre–matrix networks.     

Kapok/cotton fabric–polypropylene composites

Kapok/cotton fabric has been used as reinforcement for conventional polypropylene and maleic anhydride grafted polypropylene resins. Treating the reinforcement with acetic anhydride and sodium hydroxide has modified the fabric (fibres). Thermal and mechanical properties of the composites were investigated. Results show that fibre modification gives a significant improvement to the thermal properties of the plant fibres, whereas tests on the mechanical properties of the composites showed poor tensile strength. Mercerisation and weathering were found to impart toughness to the materials, with acetylation showing slightly less rigidity compared to other treatments on either the fibre or composites. The modified polypropylene improved the tensile modulus and had the least toughness of the kapok/cotton reinforced composites. MAiPP reinforced with the plant fibres gave better flexural strength and the same flexural modulus at lower fibre content compared with glass fibre reinforced MAiPP.     

Novel Thermoplastic Composites from Commodity Polymers and Man-Made Cellulose Fibers

Summary: A new class of fibre reinforced commodity thermoplastics suited for injection moulding and direct processing applications has been developed using man-made cellulosic fibres (Rayon tire yarn, Tencel, Viscose, Carbacell) and thermoplastic commodity polymers, such as polypropylene (PP), polyethylene (PE), high impact polystyrene (HIPS), poly(lactic acid) (PLA), and a thermoplastic elastomer (TPE) as the matrix polymer. For compounding, a specially adapted double pultrusion technique has been employed which provides composites with homogeneously distributed fibres. Extensive investigations were performed with Rayon reinforced PP in view of applications in the automotive industry. The Rayon-PP composite is characterized by high strength and an excellent impact behaviour as compared with glass fibre reinforced PP, thus permitting applications in the field of engineering thermoplastics such as polycarbonate/acrylonitrile butadiene styrene blends (PC/ABS). With the PP based composites the influence of material parameters (e.g. fibre type and load, coupling agent) were studied and it has been demonstrated how to tailor the desired composite properties as modulus and heat distortion temperature (HDT) by varying the fibre type or adding inorganic fillers. Man-made cellulose fibers are also suitable for the reinforcement of further thermoplastic commodity polymers with appropriate processing temperatures. In case of PE modulus and strength are tripled compared to the neat resin while Charpy impact strength is increased five-fold. For HIPS mainly strength and stiffness are increased, while for TPE the property profile is changed completely. With Rayon reinforced PLA, a fully biogenic and biodegradable composite with excellent mechanical properties including highly improved impact strength is presented.     

Compression and tensile properties of self-reinforced poly(ethylene terephthalate)-composites

Tensile and compression properties of self-reinforced poly(ethylene terephthalate) (SrPET) composites has been investigated. SrPET composites or all-polymer composites have improved mechanical properties compared to the bulk polymer but with maintained recyclability. In contrast to traditional carbon/glass fibre reinforced composites, SrPET composites are very ductile, resulting in high failure strains without softening or catastrophic failure. In tension, the SrPET composites behave linear elastically until the fibre-matrix interface fails, at which point the stiffness starts decreasing. As the material is further strained, strain hardening occurs and the specimen finally fails at a global strain above 10%. In compression, the composite initially fails through fibre yielding, and at higher strains through fibre bending. The stress-strain response is reminiscent of an elastic-perfectly plastic material with a high strain to failure (typically over 10%). This indicates that SrPET composites are not only candidates as semi-structural composites but also as highly efficient energy absorbing materials.     

Thermogravimetric and dynamic mechanical thermal analysis of pineapple fibre reinforced polyethylene composites

The thermal behaviour of pineapple leaf fibre (PALF) reinforced polyethylene composites was studied by thermogravimetric and dynamic mechanical thermal analysis. Fibre treatment was carried out using isocyanate, silane and peroxide to improve the interfacial adhesion between fibre and matrix. The effects of fibre loading and surface modification on the thermal properties were evaluated. It was found that at high temperature PALF degrades before the polyethylene matrix. The storage modulus increased with increase of fibre loading and decreased with increase of temperature. The treated fibre composites impart better properties compared to untreated system. Tan δ showed a distinct peak at low temperature ascribed to the glass transition temperature of polyethylene but no peak was observed for PALF fibre. The relative damping increased with fibre loading. Cole-Cole analysis was made to understand the phase behaviour of the composite samples.     

Effect of wood sawdust filler on the mechanical properties of Indian mallow fiber yarn mat reinforced with polyester composites

The research article focused on the effect of wood sawdust as secondary filler reinforcement in Indian mallow fiber yarn mat reinforced with polyester composites. Composites were fabricated along the transverse and longitudinal orientation in six different combinations by compression molding machine. The mechanical properties of composites by single and double layer yarn mat with and without wood sawdust filler were evaluated while loading composites specimen on warp and weft direction at the first time in this research paper. The Indian mallow fiber double layer longitudinal orientation yarn mat/wood sawdust filler/polyester composite specimen along the warp direction was found to exhibit optimum mechanical properties compared to other composites. Furthermore, the Indian mallow fiber yarn mat composites were fabricated with helmet and civil construction pipes at first time in this work to replace the synthetic fiber through natural fiber. Scanning electron microscopy was performed to study the morphologies of internal crack and fractured surface of composites.     

Damping analysis of nonwoven natural fibre-reinforced polypropylene composites used in automotive interior parts

The aim of this work is to evaluate the dynamic properties of nonwoven flax, hemp, kenaf and glass fibre-reinforced polypropylene (PP) composites. Also, the influence of some parameters, such as the type of reinforcement, the fibre/matrix weight ratio, the fibre orientation and the porosity content, on the damping behaviour of these nonwoven composites is investigated. To this end, a free flexural vibrations analysis was conducted to experimentally identify their natural frequencies and their associated loss factors. The obtained results show that the nonwoven composites reinforced by natural fibres present higher loss factors compared with those of the glass-PP composite. These interesting damping properties make these nonwoven composites very attractive for automotive applications where the dissipation of vibrations is highly requested.     

Study on insulating thermal conductive BN/HDPE composites

Thermal conductivity of boron nitride (BN) reinforced high density polyethylene (HDPE) composites was investigated under a special dispersion state of BN particles in HDPE, i.e., BN particles surrounding HDPE matrix particles. The results indicated that the special dispersion of BN in matrix gives the composites high thermal conductivity at low filler content; moreover, the smaller BN particles can more easily form conductive chains of filler compared to the larger filler particles. Examining the dependence of electrical insulation and mechanical properties of the composites on BN content demonstrated that the reinforced composites containing 30% by volume of filler has good electrical insulation and mechanical properties.     

Thermal degradation and fire resistance of unsaturated polyester, modified acrylic resins and their composites with natural fibres

The thermal degradation and fire resistance of different natural fibre composites were studied. Unsaturated polyester (UP) and modified acrylic resins (Modar) were used as matrix composites. The smoke emission of the materials was also analysed, as well as, the performance against the fire of the biocomposites and glass reinforced composites was compared. Thermal degradation indicated that the Modar matrix composites were more resistant to temperature than the composites with UP matrix. Flax fibre, due to their low lignin content, exhibit the best thermal resistance among the natural fibres studied.From the results obtained about the thermal and fire resistance of the composites it is possible to conclude that the flax fibre seems to be the most adequate to be used, due to the long time to ignition and the long period prior to reach the flashover. On the other hand, the jute fibre composites showed a short duration but a quick growing fire with the lowest smoke emission. The low smoke is an important advantage, which reduces one of the main hazards of fire.     

Why do we observe significant differences between measured and ‘back-calculated’ properties of natural fibres?

The drive towards sustainability, even in materials technologies, has fuelled an increasing interest in bio-based composites. Cellulosic fibres, such as flax and jute, are being considered as alternatives to technical synthetic fibres, such as glass, as reinforcements in fibre reinforced polymer composites for a wide range of applications. A critical bottleneck in the advancement of plant fibre composites (PFRPs) is our current inability to predict PFRP properties from data on fibre properties. This is highly desirable in the cost- and time-effective development and design of optimised PFRP materials with reliable behaviour. This study, alongside limited other studies in literature, have found that the experimentally determined (through single fibre tests) fibre properties are significantly different from the predicted (‘back-calculated’ using the popular rule-of-mixtures) fibre properties for plant fibres. In this note, we explore potential sources of the observed discrepancy and identify the more likely origins relating to both measurement and errors in predictions based on the rule-of-mixtures. The explored content in this discussion facilitates the design of a future investigation to (1) identify the sensitivity of the discrepancy between measured and predicted fibre properties to the various potential origins, (2) form a unified hypothesis on the observed phenomenon, and (3) determine whether the rule-of-mixtures model (in specific cases) can be improved and may be able to predict properties precisely.     

Cellulose man-made fibre reinforced polypropylene—correlations between fibre and composite properties

A series of viscose fibres from the tyre cord type varying in mechanical parameters and titre were compounded with polypropylene to produce fibre reinforced composites. Single fibre strength is analysed in detail and conclusions are drawn with respect to effective strength values in composite applications. Composites were analysed in terms of tensile and impact properties. Correlations between single fibre and composite properties are studied. High fibre elongation leads to favourable composite impact properties via high composite elongations at break. Using water as a plastisizing agent increasing fibre elongation, notched Charpy impact strength can be improved by more than 50%. Using a modified rule of mixtures and a shear lag model for the composite modulus it was shown how a titre reduction improves the composite stiffness by an increased interfacial area. A direct fibre-composite strength correlation was not found.     

Seawater ageing of flax/poly(lactic acid) biocomposites

Natural fibre reinforced biopolymer composites, or biocomposites, are an alternative to the glass fibre reinforced thermoset composites widely used today in marine applications. Biocomposites offer good mechanical properties and total biodegradability, but if they are to be adopted for marine structures their durability in a seawater environment must be demonstrated. In the present study unreinforced PLLA (Poly(l-Lactic acid)), injected and film stacked flax composites with the same PLLA matrix have been examined. All the samples were aged in natural seawater at different temperatures in order to accelerate hygrothermal ageing. Changes to physico-chemical and mechanical behaviour have been followed by weight measurements, thermal and gel permeation chromatography (GPC) analyses, and tensile testing, completed by acoustic emission recording and scanning electron microscopy (SEM) examination. The matrix tensile stiffness is hardly affected by seawater at temperatures to 40 °C but the composite loses stiffness and strength. Fibre/matrix interface weakening is the main damage mechanism induced by wet ageing, but both matrix and fibre cracks also appear at longer periods.     

Improvement of Fibre-Matrix-Adhesion of Natural Fibres by Chemical Treatment

Plastics, also called synthetic polymers, are playing an important role in daily living. To raise more applications it is necessary to modify known polymeric systems to reach improved materials/material systems. A possibility to create new optimised materials out of neat polymers is offered by compounding them with different filling material. Besides chemical modification of polymers, mixing, combining or use of different fillers, one possibility is given by the composite technique, whereas the combination of the polymeric matrix and the embedded reinforcement (e.g. fibre) are yielding in optimised materials adjusted to the required properties. Concerning the polymeric matrix, either thermoplastic or thermoset material can be used. In case of the reinforcement, either synthetic (carbon-, glass- or polymeric fibres) or natural fibres are introduced to composites. To obtain an appropriate adhesion of the matrix to the reinforcement system, synthetic fibres are equipped with an avivage. For natural fibres, there are no such materials available and the hydrophilic property of this system surface prevents an adhesion to hydrophobic polymers, as well as to sizings. In this paper, ways are shown to modify the natural fibres via chemical treatment to yield higher physical properties at better adhesion. Also we will explain activities on the use of natural fibres as reaction systems and processing tools as well as the attempt to isolate the different compounds of the neat fibre via selective work-up.     

The addition of acid treated carbon nanotube on the interfacial adhesion of carbon fiber reinforced UHMWPE composite

Carbon fiber reinforced Ultra High Molecular Weight Polyethylene (CF/UHMWPE) composites have been filled with acid treated carbon nanotube to enhance the adhesion. According to the modification, the interlaminar shear strength (ILSS) of composites has been greatly improved. Dynamic wetting method, XPS and SEM are used to examine the microscopic properties of resultant composites. The enhanced ILSS is attributed to the CNT interlock, which improves the wetting between carbon fibers and resins. Copyright © 2017 John Wiley & Sons, Ltd.     

A review on plant fiber reinforced thermoset polymers for structural and frictional composites

In recent past years, utilization of synthetic materials has become a matter of immense concern due to increasing environmental awareness in terms of safety, sustainability and maintaining ecological balance. A substantial amount of work has been carried out on various aspects of plant based natural fiber reinforced thermoset polymer composite materials due to their numerous inherent properties like high specific strength, low cost and degradability. Current issues and challenges associated with mechanical and tribological properties of only plant based natural fiber reinforced thermoset composites have been highlighted in the present study. Various factors influencing mechanical and tribological characteristics have been discussed keeping the focus on plant fiber reinforced thermoset composites. A detailed discussion on mechanical (tensile, compressive, flexural, impact strength) and tribological properties (friction and specific wear rate) have been reported. Interfacial adhesion was found to be a dominating factor with respect to mechanical and tribological properties. Wear and frictional characteristics of plant fiber based thermoset composites can be controlled using suitable fillers and reinforcement orientation. A discussion on interfacial adhesion and its effect on composite performance have also been included.     

Effects of Water and Chemical Solutions Ageing on the Physical,Mechanical, Thermal and Flammability Properties of Natural Fibre-Reinforced Thermoplastic Composites

Biocomposites comprising a combination of natural fibres and bio-based polymers are good alternatives to those produced from synthetic components in terms of sustainability and environmental issues. However, it is well known that water or aqueous chemical solutions affect natural polymers/fibres more than the respective synthetic components. In this study the effects of water, salt water, acidic and alkali solutions ageing on water uptake, mechanical properties and flammability of natural fibre-reinforced polypropylene (PP) and poly(lactic acid) (PLA) composites were compared. Jute, sisal and wool fibre- reinforced PP and PLA composites were prepared using a novel, patented nonwoven technology followed by the hot press method. The prepared composites were aged in water and chemical solutions for up to 3 week periods. Water absorption, flexural properties and the thermal and flammability performances of the composites were investigated before and after ageing each process. The effect of post-ageing drying on the retention of mechanical and flammability properties has also been studied. A linear relationship between irreversible flexural modulus reduction and water adsorption/desorption was observed. The aqueous chemical solutions caused further but minor effects in terms of moisture sorption and flexural modulus changes. PLA composites were affected more than the respective PP composites, because of their hydrolytic sensitivity. From thermal analytical results, these changes in PP composites could be attributed to ageing effects on fibres, whereas in PLA composite changes related to both those of fibres present and of the polymer. Ageing however, had no adverse effect on the flammability of the composites.     

Interfacial and wetting properties of carbon fiber reinforced epoxy composites with different hardeners by electrical resistance measurement

In this research, interfacial and wetting properties of N,N,N,N-tetraglycidyl-4,4-diaminodiphenylmethane (TGDDM) epoxy resin with two hardeners with different chemical structure were evaluated by electrical resistance (ER) measurement. The heat of reaction of TGDDM epoxy with the two different hardeners, 33 and 44 di-amino di-phenyl sulphone (DDS), was analyzed by differential scanning calorimetry (DSC). The TGDDM epoxy exhibited different mechanical properties with the two different DDS hardeners. Combined ER, wetting measurements and the microdroplet test were used for evaluating the spreading effect and interfacial shear strength (IFSS) of carbon fiber (CF) reinforced TGDDM epoxy composites with these different hardeners. The heat of reaction and mechanical properties of TGDDM/DDS were influenced by the chemical structure and different free volumes of the epoxy resins. The relationships between the ER-wetting results and the IFSS were internally consistent. Ultimately it was demonstrated that ER measurements makes it possible to estimate the interfacial and wetting properties of CF reinforced epoxy composites.     

Study on the evaluation of mechanical and thermal properties of natural sisal fiber/general polymer composites reinforced with nanoclay

Composite materials, made by replacing traditional materials, are used because of their capability to produce tailor-made, desirable properties such as high tensile strength, low thermal expansion, and high strength to weight ratio. The need for the development of new materials is essential and growing day by day. The natural sisal/general polymer (GP) reinforced with nanoclay composites has become more attractive due to its high specific strength, light weight, and biodegradability. In this study, sisal–nanoclay composite is developed and its mechanical properties such as tensile strength, flexural strength, and impact strength are evaluated. The interfacial properties, internal cracks, and internal structure of the fractured surface are evaluated using scanning electron microscope. The thermal disintegration of composites are evaluated by thermogravimetric analysis. The results indicate that the incorporation of nanoclay in sisal fiber/GP can improve its properties and can be used as a substitute material for glass fiber-reinforced polymer composites.     

Effect of ageing of sisal fibres on properties of sisal - Polypropylene composites

A composite laminate based on natural sisal fibre and polypropylene was prepared by compression moulding. The mechanical properties of the composite were assessed under tensile, flexural and impact loading. Changes in the stress-strain characteristics, yield stress, tensile strength, and tensile (Young's) modulus, due to ageing have been analysed. Important findings with the fresh and aged fibres and their behaviour in composites have been reported and analysed.     

Preparation and properties of natural rubber composites reinforced with pretreated carbon nanotubes

In order to achieve dramatic improvements in the performance of rubber materials, the development of carbon nanotube (CNT)‐reinforced rubber composites was attempted. The CNT/natural rubber (NR) nanocomposite was prepared through solvent mixing on the basis of pretreatment of CNTs. Thermal properties, vulcanization characteristics, and physical and mechanical properties of the CNT/NR nanocomposites were characterized in contrast to the carbon black (CB)/NR composite. Through the addition of the CNTs treated using acid bath followed by ball milling with HRH (hydrated silica, resorcinol, and hexamethylene tetramine) bonding systems, the crystallization melting peak in differential scanning calorimetry (DSC) curves of NR weakened and the curing rate of NR slightly decreased. Meanwhile, the over‐curing reversion of CNT/NR nanocomposites was alleviated. The dispersion of the treated CNTs in the rubber matrix and interfacial bonding between them were rather good. The mechanical properties of the CNT‐reinforced NR showed a considerable increase compared to the neat NR and traditional CB/NR composite. At the same time, the CNT/NR nanocomposites exhibited better rebound resilience and dynamic compression properties. The storage modulus of the CNT/NR nanocomposites greatly exceeds that of neat NR and CB/NR composites under all temperature regions. The thermal stability of NR was also obviously improved with the addition of the treated CNTs. Copyright © 2008 John Wiley & Sons, Ltd.