Advances in Natural Polymers: Composites and Nanocomposites: 18 (Advanced Structured Materials)

Possible use of these composites for different technical applications, each suiting specific requirements such as in automotive sector is also discussed based on the results of various mechanical properties. While the fracture surface of PLA matrix seems to be a smooth fragile fracture Figure 6a , surface of its nanocomposite without compatibilizer shows uneven fracture surface having some irregular protusions and holes Figure 6b and the one with compatibilizer shows more uneven, more holes and thread-like structures Figure 6c.

Also, similar to starch base composites, PEG in this composite covers the surface of nano fibrils. More uneven surface caused by the adhesive force at the interface is attributed to the observed highest strength properities of this composite. Careful reading of these tables also suggests proper selection of matrix-reinforcement system both micro and nano fibers with appropriate processing would result in optimal properties for any intended application in various areas such as building and construction, transportation, food science, nutrition and packaging, biomedical engineering, medical field, etc.

Some examples of these applications are mentioned in the next Section. Recognizing the importance of weight gains, sandwich composites including bio-based ones have also been studied for their structure and properties keeping in mind weight critical applications designed for stiffness in sectors such as aerospace, transport including ships and boats [ 41 , 42 , 67 - 72 ]. It is well known that a sandwich-structured composite is one of the special classes of composite materials, which gives high stiffness to weight and strength to weight ratio. This is fabricated by attaching two thin but stiff skins [Eg: Natural fibers such as Basalt fiber or Recycled paper] to a lightweight, but thick core [Eg: Also, normally, many sandwich structures use synthetic polymer foams or honeycombs, or other synthetic material.

Instead of synthetic core, bio based core materials such as cork or wood can also be used, which are entirely renewable resources and may be partly recyclable as well as easily composted. In the case of sandwich composites, the interface properties and changes in the global sandwich response are reported to be affected by the the processing temperature [ 41 , 42 ]. This is illustrated in Table 1b, which is corroborated by the fractographs shown in Figure 7a-7c. Separation of the upper facing can also be seen. The authors have observed some polymer remaining on the balsa Figure 7c.

Degradation of such composites and causes for the this have also been discusssed [ 42 ]. These include building and housing sectors including hurricane resistant housing, infrastructure, automotive sector Eg. Door panels, instrument panels, armrests, etc , textile geotextiles and nonwoven textiles , entertainment accessories archery bows, golf clubs and boat hulls , etc.

Other uses of green composites include new low dielectric constant material suited to electronics applications based on hollow keratin fibers and chemically modified soybean oil [ 73 ]. Some of the proposed possible fields of application of the green composite systems include: On the other hand, nano bio green composites seemed to have overtaken their micro composites in the development, production and usage aspects.

Some of the products developed or planned for development include automotive parts mirror housings, door handles and panels, trunk liners, roofs, upholstery, engine covers durable load bearing parts and building blocks in cars based on cellulose nano fibers [Personal discussions with Prof. Mohini Saini, University of Toronto, Canada], impellers and blades for vacuum cleaners, power tool housings and covers for portable electronic equipment Eg. Mobile phones [ 76 , 77 ]. Some of the others that are also being planned include: This is evident from the strong Great Wall of China during B.

Importance of such materials is underlined due to the decreasing non-renewable sources and their increasing costs, growing concern and regulatory demands for clean environment along with the thrust on increaseing use of renewable rsources. In addition, their unique characteristics such as biocompatibility, biodegradability and even exhibiting functional properties have driven scientists, engineers and technologists in academic and industrial research environments to transform the field of sustainable and green polymers and materials. Recognizing the above facts, the following should be considered, some of which may be future perspectives:.

Focus on use of modeling and simulation as well as Artificial Neural Network ANN to correlate various processing parameters dimensions and amount of reinforcements, duration and temperature for processing without affecting the inherent properties of constituent materials and properties obtained with a view to reduce the number of experiments to arrive at proper composite systems with suitable processing parameters to produce products for various intended applications. Since the properties of nano bio-fibers depend on the source from which they are produced, probably, research on spinning of different nano bio-fibers either individually or hybridizing with others should be attempted.

In the case of development of diverse nanocomposites consisting of different combinations of nano materials fibers or particles or platelets or tubes , and polymer matrices at various volume fractions, the self-assembly process, a simple approach belonging to biomimetic process of making nanocomposites, can be adapted. In fact, there have been many published reviews and papers since nintees dealing with various aspects of processing of such materials based on biomimetic engineering [ 81 - 88 ].

Some classical examples of natural high-performance composites abalone shells, bone and enamel with matrix proteins [ 89 , 90 ], high stiffness cactus spines, with their and the tunics of sea peaches composed of cellulose, proteins and mucopolysaccharides [ 91 ]. Even wood and other plant based fibers can also be considered as natural, but a complex and highly sophisticated composites, since cellulose microfibrils in these materials are embedded in lignin matrix self-assembly process. This new approach to making biomimetic nanocomposites is also demonstrated by the exfoliation of graphite into a matrix of genetically engineered proteins having two well-defined binding blocks diblock proteins and native nano-fibrillated cellulose [ 87 ] and also in the case of textiles [ 84 , 85 ].

Following the success of research on spinning of different nano bio-fibers either individually or hybridizing with others, incorporation of these into suitable bio-polymer may produce nano bio-composites as possible superior structural components lighter than their micro counterparts or for use in different areas such as biomedical, electrical and optical as a component for various functional devices. It is hoped with all the above new dimensions for green materials comprising of biopolymers and their composites would emerge in future considering them as a cost-effective alternative to wood and petro-based plastic products However, larger acceptance of these new generation of materials by the society is still expected, while the demand for agricultural products will increase, which may pave way for environmental friendly and sustainable future.

At the outset the author is grateful to Editorial office, in particular to Dr. James Franklin Editoral Assistant of this Journal not only for inviting me to contribute this paper, but persisting with his efforts to achieve the main goal of getting my contribution to this journal. My sincere thanks to Prof. Springer] for kindly giving permission to use many of figures from their publications in this paper.

He is also thankful to his co-researchers [Dr. J Min Mater Character Eng Compos Sci Technol Guan J, Hanna MA Selected morphological and functional properties of extruded acetylated starch-cellulose foams. Compos Part A J R Soc Interface 4: Mater Sci EngA Ashori A Wood-plastic composites as promising green-composites for automotive industries! Kasetsart J Nat Sci J Food Sci An overview about mechanical characteristics and application areas. Applied Science and Manufacturing Thesis in Engineering and Materials Scicence. An alternative to traditional composites.

J Technol Stud 1: Ciencia e Agrotecnologia Kaushik A, Singh M, Verma G Green nanocomposites based on thermoplastic starch and steam exploded cellulose nanofibrils from wheat straw. Cassava starch-green coir fibers from Brazil. Chemistry, Morphology and Properties. J Polym Environ Appl Compos Mater J Mater Sci Res 1: J Thermoplastic Compos Mater Tang C Next-generation renewable polymers. Chem Eng Trans Inter J Polym Ana Charact Heux L, Chauve G, Bonini C Nonflocculating and chiral-nematic self-ordering of cellulose microcrystals suspensions in nonpolar solvents.

Trends Food Sci Technol Azizi Samir MA, Alloin F, Dufresne A Review of recent research into cellulosic whiskers, their properties and their application in nanocomposite field. Influence of processing conditions. Chemistry, solubility and fiber formation. Scudamore R, Cantwell WJ The effect of moisture and loading rate on the interfacial fracture properties of sandwich structures. Experimental and Applied Mechani. Proulx T editor , Vol. Adv Mater SciEng Express Polym Lett 3: International Symposium on Polymers and the Environment: Lee KB Two-step activation of paper batteries for high power generation: Zweig SE Fromsmart tags to brilliant tags: Advances in drug stability monitoring.

International Journal of Polymer Science

Chowdhury H Final Report: A versatile biomimetic approach to environmentally friendly and energy-efficient processing of nanostructured composites. J R Soc Interface 3: Am J Bot It concluded that chemical treatment of the natural fiber improved adhesion between the fiber surface and the polymer matrix which ultimately enhanced physicomechanical and thermochemical properties of the NFPCs.

The increase in environmental consciousness and community interest, the new environmental regulations and unsustainable consumption of petroleum, led to thinking of the use of environmentally friendly materials. Natural fiber is considered one of the environmentally friendly materials which have good properties compared to synthetic fiber [ 1 ]. Current pointers are that interest in NFPCs industry will keep on growing quickly around the world.

The utilization of NFPCs has expanded considerably in the shopper merchandise as developing industry sectors throughout the last few years. Natural fibers in simple definition are fibers that are not synthetic or manmade. They can be sourced from plants or animals [ 3 ]. The use of natural fiber from both resources, renewable and nonrenewable such as oil palm, sisal, flax, and jute to produce composite materials, gained considerable attention in the last decades, so far. The plants, which produce cellulose fibers can be classified into bast fibers jute, flax, ramie, hemp, and kenaf , seed fibers cotton, coir, and kapok , leaf fibers sisal, pineapple, and abaca , grass and reed fibers rice, corn, and wheat , and core fibers hemp, kenaf, and jute as well as all other kinds wood and roots [ 4 ].

The most common and commercially natural fibers in the world and world production have been shown in Table 1. Fiber reinforced polymer matrix got considerable attention in numerous applications because of the good properties and superior advantages of natural fiber over synthetic fibers in term of its relatively low weight, low cost, less damage to processing equipment, good relative mechanical properties such as tensile modulus and flexural modulus, improved surface finish of molded parts composite, renewable resources, being abundant [ 5 ], flexibility during processing, biodegradability, and minimal health hazards.

NFPCs with a high specific stiffness and strength can be produced by adding the tough and light-weight natural fiber into polymer thermoplastic and thermoset [ 6 ]. On the other hand, natural fibers are not free from problems and they have notable deficits in properties. The natural fibers structure consists of cellulose, hemicelluloses, lignin, pectin, and waxy substances and permits moisture absorption from the surroundings which causes weak bindings between the fiber and polymer.

Furthermore, the couplings between natural fiber and polymer are considered a challenge because the chemical structures of both fibers and matrix are various. These reasons for ineffectual stress transfer during the interface of the produced composites. Accordingly, natural fiber modifications using specific treatments are certainly necessary.

• The Protest (A Short Story)?
• Nanostructured materials for applications in drug delivery and tissue engineering?
• Dr Vijay Kumar Thakur.
• Caught By The Billionaire - Right In The Jewels (A BDSM Romance).
• Ready for Marriage?: The Marriage Ultimatum / Laying His Claim / The Bride Tamer (Mills & Boon Spotlight).
• e-Polymers.
• .

These modifications are generally centered on the utilization of reagent functional groups which have ability for responding of the fiber structures and changing their composition. As a result, fiber modifications cause reduction of moisture absorption of the natural fibers which lead to an excellent enhancement incompatibility between the fiber and polymer matrix [ 7 ]. The wide applications of NFPCs are growing rapidly in numerous engineering fields. The different kinds of natural fibers reinforced polymer composite have received a great importance in different automotive applications by many automotive companies such as German auto companies BMW, Audi Group, Ford, Opel, Volkswagen, Daimler Chrysler, and Mercedes , Proton company Malaysian national carmaker , and Cambridge industry an auto industry in USA.

Beside the auto industry, the applications of natural fiber composites have also been found in building and construction industry, sports, aerospace, and others, for example, panels, window frame, decking, and bicycle frame [ 8 ]. In a review of chemical treatments of natural fibers, Kabir and coworkers [ 9 ] concurred that treatment is an important factor that has to be considered when processing natural fibers.

They observed that fibers loose hydroxyl groups due to different chemical treatments, thereby reducing the hydrophilic behavior of the fibers and causing enhancement in mechanical strength as well as dimensional stability of natural fiber reinforced polymer composites. Their general conclusion was that chemical treatment of natural fibers results in a remarkable improvement of the NFPCs. Natural fiber polymer composites NFPC are a composite material consisting of a polymer matrix embedded with high-strength natural fibers, like jute, oil palm, sisal, kenaf, and flax [ 10 ].

Usually, polymers can be categorized into two categories, thermoplastics and thermosets.

Покупки по категориям

The structure of thermoplastic matrix materials consists of one or two dimensional moleculars, so these polymers have a tendency to make softer at an raised heat range and roll back their properties throughout cooling. This structure gives to thermoset polymer good properties such as high flexibility for tailoring desired ultimate properties, great strength, and modulus [ 3 , 4 ]. Thermoplastics widely used for biofibers are polyethylene [ 11 ], polypropylene PP [ 12 ], and poly vinyly chloride PVC ; hereas phenolic, polyester, and epoxy resins are mostly utilized thermosetting matrices [ 10 ].

Different factors can affect the characteristics and performance of NFPCs.

Advances in science and technology of polymers and composite materials : e-Polymers

The hydrophilic nature of the natural fiber [ 5 ] and the fiber loading also have impacts on the composite properties [ 13 ]. Usually, high fiber loading is needed to attain good properties of NFPCs [ 14 ]. Generally, notice that the rise in fiber content causes improving in the tensile properties of the composites [ 8 ]. Another vital factor that considerably impacts the properties and surface characteristics of the composites is the process parameters utilized. For that reason, appropriate process techniques and parameters should be rigorously chosen in order to get the best characteristics of producing composite [ 10 ].

The chemical composition of natural fibers also has a big effect on the characteristics of the composite represented by the percentage of cellulose, hemicellulose, lignin, and waxes. Table 2 shows the chemical composition of some common natural fibers [ 4 ]. Many researchers [ 8 , 11 , 15 — 17 ] have examined and researched the suitability, competitiveness, and capabilities of natural fibers embedded in polymeric matrices.

Most Downloaded Articles

On the other hand, some researchers studied and compared between different natural fiber composites and their stability in various applications [ 20 ]. The properties of natural fiber composite are different to each other according to previous studies, because of different kinds of fibers, sources, and moisture conditions. The performance of NFPCs relies on some factors, like mechanical composition, microfibrillar angle [ 20 ], structure [ 10 ], defects [ 22 ], cell dimensions [ 23 ], physical properties [ 4 ], chemical properties [ 24 ], and also the interaction of a fiber with the matrix [ 25 ].

Since every product in market has drawbacks, similarly, natural fiber reinforced polymer composites also have drawbacks. The couplings between natural fiber and polymer matrix are problem taken into consideration, as a result of the difference in chemical structure between these two phases. This leads to ineffective stress transfer during the interface of the NFPCs. Thus, the chemical treatments for the natural fiber are necessary to achieve good interface properties. The reagent functional groups in the chemical treatments have ability to react on the fiber structures and alter the fiber composition [ 9 ].

Natural fibers include a functional group named as hydroxyl group which makes the fibers hydrophilic. During manufacturing of NFPCs, weaker interfacial bonding occurs between hydrophilic natural fibre and hydrophobic polymer matrices due to hydroxyl group in natural fibres. This could produce NFPCs with weak mechanical and physical properties [ 8 ]. There are considerable enhancement and suggestions for the natural fibers that can be implemented in order to enhance their mechanical properties resulting in high strength and structure.

Once the base structures are made strong, the polymers can be easily strengthened and improved [ 26 ]. There are number of aspects that effects of composite are performance level or activities, of which to name a few are the following; a orientation of fiber [ 5 ], b strength of fibers [ 8 ], c physical properties of fibers [ 27 ], d interfacial adhesion property of fibers [ 28 ] and many more.

NFPCs are such composites whose mechanical efficiency is dependent upon the interface provided by fiber-matrix along with the stress transfer function in which stress is transferred to fiber from matrix. This has been reported by many investigators in several researches [ 1 , 23 , 29 ]. Characteristic components of natural fibers such as orientation [ 30 ], moisture absorption [ 31 ], impurities [ 32 ], physical properties [ 33 ], and volume fraction [ 34 ] are such features that play a constitutive role in the determination of NFPCs mechanical properties.

Mechanical properties of PLA, epoxy, PP, and polyester matrices can be affected by many types of natural fibers and to show some of them, Figure 1 is included. NFPCs show even better mechanical properties than a pure matrix in cases where jute fibers are added in PLA polylactic-acid ; in this case, Conversely, composites of PP were improved with the incorporation of hemp, kenaf, and cotton [ 5 ]. However, due to the rubber phase present in gum compound, a greater range of flexibility is present in such materials which results in reduced stiffness and storage modulus.

It is also known that stiffness and stress transfer in composites increases with an increased or excessive addition of fiber which provides a better loss modulus and also a better storage modulus. A group of researchers led by Ismail et al. When the fiber content is increased, torque of the fibers is also increased and with smallest possible particle size of OPWF, highest torque was noticed. However, increasing the factor of OPWF in ENR compounds showed reduced tensile strength and while reaching the break point a considerable elongation is evident.

It also evident increase in elongation, tear strength, tensile modulus and hardness due to higher loading of OPWF. A higher tensile strength and tear strength as tensile modulus were identified in composites that were filled with even smallest proportion of OPWF [ 10 ]. The fracture behavior of composites is also affected due to the nonlinear mechanical behavior of natural fibers, under the influence of tensile-shear loads [ 1 ]. Table 3 shows the mechanical properties for common types of natural fiber in the world [ 38 ].

The bonding strength between fiber and polymer matrix in the composite is consider a major factor in order to get superior fiber reinforcement composites properties. Because of pendant hydroxyl and polar groups in fiber, this leads to extremely high moisture absorption of fiber, resulting in weak interfacial bonding between the fiber and the hydrophobic matrix polymers.

To develop composites with good mechanical properties, chemical modification of fibre carried out to reduce the hydrophilic behavior of fibers and the absorption of moisture [ 15 , 39 ]. The different surface treatments of advanced composites applications were reviewed by several researchers [ 40 — 42 ]. The effects of different chemical treatments on cellulosic fibers that were employed as reinforcements for thermoplastics and thermoset were also examined. For the treatments, the different kinds of chemical treatment include silane [ 43 ], alkali [ 44 ], acrylation [ 45 ], benzoylation [ 46 ], maleated coupling agents [ 47 ], permanganate [ 48 ], acrylonitrile and acetylation grafting [ 49 ], stearic acid [ 50 ], peroxide [ 51 ], isocyanate [ 52 ], triazine [ 53 ], fatty acid derivate oleoyl chloride , sodium chloride, and fungal [ 9 ].

The impact of alkaline treatment on surface properties of Iranian cultivated natural fibers was studied by Cordeiroa et al. The research revealed that alkaline treatment gets rid of some chemical components on the surface of the fibers, comprising uranic acid hemicellulose , aromatic moieties extractives , and nonpolar molecules from the partial lignin depolymerisation. There is a stronger effect on chemical components of nonwood fibers. Improving the crystallinity of nonwood fibers, in the softwood fibers result in only a minor increase.

Le Troedec et al. The effects were on the mechanical properties of the composite materials from mixtures of hemp fiber and lime by differential thermal evaluation and tests. The observation was that every treatment had a direct effect on the fiber surface. The fracture behavior and the mechanical properties of a NFPC depend on the properties of constituents and region of the fiber surface, or interphase, where the stress transfer occurs.

Furthermore, the tailoring of the interphase by different kinds of surface treatments and carefully characterizing it provides a better knowledge of the behavior of the NFPCs. Moreover, different fiber surface treatments modify the natural fiber microstructure specifically under high loading rates. The alkali concentration on the fiber surfaces results in better mechanical properties of the resulted composite.

However, the rising of alkali concentration maybe causes fiber surface damage, leading to a decrease of mechanical properties. The effect of different chemical treatment on the mechanical properties and characteristic of sisal-oil palm hybrid fiber reinforced natural rubber composites have been studied by John et al.

With chemical treatment, the torque values increased which lead to greater crosslinking. Van de Weyenberg et al. It was discovered that the employment of long flax slivers may not necessarily lead to more superior composite properties. The highest enhancement of the flexural properties of the flax fiber reinforced epoxy composites can be gotten by chemical treatments. Some modifications in the chemical and physical properties of the lignocellulosic fibers can be observed after the treatment of the fiber of rubber wood with laccase enzymes.

These chemical treatments lead to the amorphous lignin content, changing the hemicellulose content and ultimately the natural crystallinity [ 57 ]. The fiber has treatment effect on morphological and single fiber tensile strength of EFB fiber. It was revealed that it changed the properties of the fiber surface topography after the treatment.

For tensile modulus, the alkaline treatment has enhanced the tensile properties of sugar palm fiber reinforced epoxy composites at better soaking times and concentrations of alkaline. On the other hand, the increase the alkaline concentration may lead to fiber damage [ 58 ]. The coated process enhanced the mechanical and physical properties and also improved the fiber performance. The ABS treatment led to reducing the water absorption and also decreased the biodegradation potential of the fiber in contact with soil.

With the coating, the tensile strength and elasticity moduli of the OPEFB fibers became better than what they were in the past. The surface area between fiber and soil particles increased by coating fiber, which led to improving the shear strength parameters of the fiber reinforced soils [ 66 ]. Due to eco-friendly and sustainability nature, natural fiber composites prefers as compared to conventional synthetic fibre based composites. They are applied in diversified domains [ 9 , 18 , 20 , 38 , 67 ] such as building materials [ 68 ], aerospace industry, and automotive industry [ 69 ].

Natural fibers and polymers are organic materials and are very sensitive to alter any features if flame is introduced to them. Flame retardancy is another aspect that has become greatly significant in order to fulfill safety measures taken while developing natural fiber composites. In the presence of flame, burning of composites takes place in five different steps as shown below: If flame retardancy has been achieved in the aforementioned steps, no matter whether ignition step has been conducted or not, the procedure will be terminated before an actual ignition is set up.

There are two forms of products that are obtained upon burning of composites; these two include high cellulose content and high lignin content. High cellulose provides chances of higher flammability whereas higher values of lignin show there is a greater chance of char formation [ 71 ]. Thermal resistance is provided by flax fibers [ 72 ]; however, silica or ash is another important feature that is helpful in extinguishing fire [ 73 ]. In order to enhance fire resistance of various NFPCs, different procedures are undertaken. Fire barriers are kind of barriers that can be applied to phenolics, ceramics, intumescents, glass mats, silicone, ablatives, and chemical additives too.

Coatings and additives used in the system of intumescent are found to be very promising fire barrier treatments in which these barriers are expanded upon heating resulting in a cellular surface that is charred even. However, with the help of this charred surface, internal or underlying components and protected against flux and heat. One of the well-known or profound flame retardants for reinforced polymers natural fibers is used with the combination of char developing cellulose material [ 74 ].

The only method of reducing combustion in this scenario is through increasing stability and char formation in the polymer. This will result in reduced flammability, decrease visible smoke, and restrict the volume of products produced due to combustions [ 72 ]. Fire retardant coating is another method that helps in enhancement of fire resistance property of composites.

There was a problem providing the content you requested

This coating is done at the end or finishing stage or impregnation. Due to changes in the fibers and lingo-cellulosic particles, fire resistance is altered during the process of manufacturing [ 75 ]. The two most widely used metal hydroxide flame retardants are known to be aluminum hydroxide [Al OH 3 ] and magnesium hydroxide [Mg OH 2 ] which are purposefully added to polymers.

The chemical reaction through which these two flame retardants decompose are as follows: For this reason, aluminum hydroxide is not considered to be thermally stable as it cannot be used for polyamides, polypropylene, or others whereas magnesium hydroxide can be used. Flame retardancy is not an easy thing to be imparted and it is only possible if there is an extensive high loading of inorganic filler. Hapuarachchi and Peijs [ 78 ] studied the development of fully bio-based natural fiber composite that has enhanced features of fire or flame retardancy. This natural fiber composite was developed with the help of PLA polymers that were derived from crops accompanied with 2 kinds of nanofillers which are able to produce synergy corresponding to flame retardancy.

High strength composites are resultant products of natural fiber reinforcement in polymers which also provide extra or improved biodegradability, low cost, light weight, and enhanced properties related to mechanical structure [ 29 ].