of polymers consists on branched or linear molecules which melt when heated and, using this property, this type of polymer can be molded using heat. When the thermoplastic melts, a mass of tangled molecules is formed but in the cooling process they can form a glass or crystallize. Even if the crystallization process happens, it is only partially because the rest becomes more mobile, also referred to non-crystalline or amorphous state. In certain cases and for some temperature region, the thermoplastics form a liquid-crystal phase . The thermoplastics can be classified according to their performances, consumption level and degree of specificity. Polyethylene (PE), polypropylene (PP), polyvinyl chloride (PVC), polystyrene (PS) are examples of commodity thermoplastics; acrylonitrile-butadiene-styrene (ABS) and styrene acrylonitrile (SAN) are known as copolymers with more specific applications. Polyamide (PA), polycarbonate (PC), polymethylmethacrylate (PMMA), polyoxymethylene or polyacetal (POM), polyphenylene ether (PPE), polyethylene terephthalate (PET) and polybutyleneterephthalate (PBT) are some examples of engineering thermoplastics; while polysulfone (PSU), polyetherimide (PEI) and polyphenylene sulfide (PPS), are engineering thermoplastics with more specific performances. Thermoplastics like ethylene-tetrafluoroethylene (ETFE), polytherether ketone (PEEK), liquid crystal polymer (LCP), polytetrafluoroethylene (PTFE), perfluoroalkoxy (PFA), fluorinated ethylene propylene (FEP), polyimide (PI) and polyvinylidene fluoride (PVDF) are for high-tech uses and have limited consumption. Finally, polybenzimidazole (PBI) is a thermoplastic for highly targeted uses with a very restricted consumption .
The pace of research on dielectric properties of heterogeneous materials has accelerated in recent years. Industries such as the aerospace, electronics and others, have continuously provided the impetus pushing the development of new materials in a fascinating and rich variety of applications. Examples abound, ranging from shielding enclosures to capacitive video disk units to antistatic devices and electromagnetic absorbing materials. The trend towards a wider variety of applications is almost certain to continue (Brosseau C. et al., 1997).
Carbon nano tube (CNT) yarn is an axially aligned CNT assembly. It has great potential many applications. In this study, the mechanical and electricalproperties of the aerogel-spun CNT yarns and CNT/Polydimethylsiloxane (PDMS) composite yarns were investigated. The CNT/PDMS yarn was fabricated by droplet infiltration of PDMS solution into the aerogel-spun CNT yarn. The mechanical properties of the CNT/PDMS yarns were significantly improved with an average strength of 837.29 MPa and modulus of 3.66 GPa, over 100% improvement compared to the original CNT yarns. The electrical conductivity of the CNT/PDMS yarn increased from 1636 S/cm to 3555 S/cm. The electromechanical properties of CNT/PDMS yarns demonstrated that such CNT yarn could be suitable for strain sensors.
strength of CNT reinforced cementitious composites was also discussed in a different publication by Manzur and Yazdani (2016). The utilization of CNF in the cement matrix started in the early 1990s (Chen and Chen 1993) when short CNFs were introduced in cement mortar, producing an increase of 85% in flexural strength, 205% in flexural toughness and 22% in compressive strength. In 2000, Chung showed that cement- CNF composites for smart structures had increased flexural strength and toughness, improved impact resistance, reduced drying shrinkage and enhanced freeze-thaw durability (Chung 2000). Li et al. (2004) displayed the microstructure of the cement mortar with nanoparticles. The compressive strength and flexural strength of the cement mortar with nanoparticles were higher than plain cement paste. A break-through study (Balagurur and Chong 2008) on the integration of micro CNFs in the cement paste showed that the usage of silica fume and methyl cellulose led to decreased electrical resistivity and increased tensile strength. Li et al. (2007) demonstrated that the abrasive resistance, compressive and flexural strengths of concrete improved significantly with the addition of nanoparticles and polypropylene fibers. Gao et al. (2009) performed tests on mechanical and electricalproperties of self- consolidating concrete with CNF. The concrete containing 1% of CNF produced the best performance in terms of compressive strength and electrical resistivity.
with a low percolation threshold (0.064 wt%). One of the early works with VGCNF/epoxy revealed that the degree of VGCNF dispersion is relevant for the composite mechanical strength . The authors dispersed the VGCNF via acetone solvent/epoxy solution and mixing. The mechanical properties of VGCNF/epoxy composites were also studied by Zhou et al. . The loading effect on the thermal and mechanical properties of the compo- sites was investigated by dispersing the VGCNF through high-intensity ultrasonication. In turn, Prasse et al.  used sonication and conventional stirring to disperse the VGCNF. Anisotropy has an effect on the electrical prop- erties: composites with VGCNF preferentially parallel to the electric field show lower electrical resistance and higher dielectric constant. This effect can be explained by the formation of a capacitor network, as demonstrated by Simões et al. [9,10] for CNT/polymercomposites. Furthermore, studies of systems such as VGCNF/poly (vinylidene fluoride) demonstrated that the matrix prop- erties, such as the crystallinity or phase type, also influ- ence the type of conduction mechanism in VGCNF/ polymercomposites . In a previous study , the electricalproperties of VGCNF/epoxy composites pre- pared by simple hand mixing were studied, and it was confirmed that conductivity is due to the formation of a tunneling network. As stated before, the VGCNF homo- genous dispersion in the matrix is important for
Carbon nanotubes (CNTs) exhibit excellent mechanical and thermal properties. Designing composites that employ CNTs as the reinforcing or filler material offer the potential to create bulk materials with greatly enhanced mechanical and thermal properties. Unfortunately, the resulting property enhancement in CNT, and other carbon nanomaterial, enhanced composites vary greatly. In macroscale composites, like carbon fiber/epoxy composites, the large interface area and relatively low surface area to volume ratio of the carbon fiber/epoxy results in excel- lent transfer of load or thermal energy across the interface, thus allowing the carbon fiber to enhance the mechanical or thermal properties of the composite. In nanocomposites, the high sur- face area to volume ratio between the reinforcing and matrix materials requires tightly coupled interactions at the interface. Additionally, due to the high surface area to volume ratio of the nanomaterial filler, there is added difficulty in ensuring the re- inforcing materials are uniformly dispersed. These two major differences between macroscale and nanoscale composites re- sults in the existing predictive models failing to predict the effec- tive composite properties. To improve the understanding of the roles that interface bonding and the dispersion of the reinforcing material play on the effective properties, we present the results of a detailed experimental study. To study the role of the rein- forcing material/matrix interface bonding, we fabricate CNT/poly- mer composites where the CNTs are functionalized with differ- ent functional groups. To study the role of the nanoparticle filler dispersion, we fabricate CNT polymercomposites with different dispersing techniques. This work shows that CNT dispersion is critical for fabricating CNT composites with enhanced mechani- cal properties.
designs (Folkes, 1992). The effectiveness of reinforcement essentially depends on the adhesion between matrix and fiber, so this is a key factor in determining the final properties of the composite material, particularly its mechanical properties (Yosoyima et al., 1984; Yosoyima et al., 1990; and Pukzky et al., 1995). In the present work, an attempt has been made to study the influence of glass fiber and carbon fiber reinforced epoxy polymer matrix on the mechanical properties. The hybrid composites were developed by varying the reinforcements from 15%, 30%, 45% and 60% of glass fiber and carbon fiber in 40% epoxy matrix under vacuum bag process. The hardness and tensile properties were studied as per the ASTM standards.
The type and concentrations of CNTs significantl fluences the phase morphology and rheological pr ties of polymer in the final composite form. Limited un- derstanding of the rheological behavior of the composite materials has been reported. Pötschke et al.  thor- oughly investigated the rheological behavior of polycar- bonate (PC) containing between 0.5 to 15 wt% CNTs with the help of dynamic oscillatory shear measurement technique at 260˚C. They studied the various masterbatch diluted composites and pure PC on complex viscosity at various frequencies as shown in the Figure 19. An in- crease in complex viscosity associated with addition of CNTs was found much higher than the changes of vis- cosity reported for carbonnanofiber having larger di- ameters for carbon black composites.
of these nitrogen containing groups. All other infiltrated buckypapers studied by Piao et al.  led to positive S-values, whereby the molecular structures of the used polymers did not contain nitrogen groups. From this, a clear correlation can be shown with the results of the present study. Positive S-values were obtained for all polymers which do not contain an amide group in their molecular structure, namely PBT, PP, PC and PVDF. Only for the polyamides (PA6, PA66, PARA) and ABS the switching from p-type to n-type was observed using SWCNT Tuball. The different kinds of PA contain amid groups. ABS contains a nitrile group instead of an amide group. Interestingly, for SWCNT HiPco such a switching only took place in ABS, which indicates a different degree of interaction with or electron donation through the PA matrices compared to SWCNT Tuball. More investigations are needed to study the influence of the structural parameters of SWCNTs on this behavior. To our knowledge, it has not yet been researched which parameters are decisive for thermoelectric properties in general and which for the doping efficiency of polymers. J. Compos. Sci. 2019, 3, x 11 of 18
The advantages of natural fibers over traditional reinforcing materials such as glass fiber, carbon fiber etc are their specific strength properties, easy availability, light weight, ease of separation, enhanced energy recovery, high toughness, non-corrosive nature, low density, low cost, good thermal properties, reduced tool wear, reduced dermal and respiratory irritation, less abrasion to processing equipment, renewability and biodegradability (Lawton and Fanta 1994; Simon et al 1998; Chauhan et al 1999, 2001; Joshi et al 2004; Singha et al 2004)[1-5]. It has been observed that natural fiber reinforced composites have properties similar to traditional synthetic fiber reinforced composites. Natural fiber composites have been studied and reviewed by a number of researchers (Dufresne 1997; Dufresne and Vignon 1998; Mao et al 2000; Kaith et al 2003; Nakagaito et al 2004, 2005; Bhatnagar and Sain 2005)[6-9]. During the past decade, a number of significant industries such as the automotive, construction or packaging industries have shown massive interest in the progress of new bio-composites materials. One of the most appropriate examples of this is the substitution of inorganic fibres such as glass or aramid fibers by natural fibers (Bledzki and Gassan 1999; Chauhan et al 1999; Chakraborty et al 2006)[10-12]. All these properties have made natural fibers very attractive for various industries currently engaged in searching for new and alternate products to synthetic fiber reinforced composites.
W hile carbon nanotubes have m any interesting properties which could make them suitable for various applications, one m ajor obstacle to their full exploitation is the problem o f batch purity. As m entioned in the previous section concerning the arc- discharge production method, carbon nanotubes are not the only product and this also true for nanotubes created using any other production method. A typical soot product from the arc-discharge cham ber (see Figure 3.3) contains anywhere betw een 50-70% non-nanotube m aterial such as amorphous carbon and graphitic nanoparticles (such as carbon “onions” which are m ulti-walled fullerene molecules). Residual m etallic particles m ay also be present depending on w hether a catalyst was employed. All o f these non nanotube species are unwanted impurities and pose a problem to both the study o f intrinsic nanotube properties and any potential applications. O f critical im portance to address this issue is a purification m ethod that does not damage the nanotubes in order to retain their unique properties. Another important requirem ent for any real-world applications is a high yield o f pristine nanotubes.
Given the growing interests and economic incentives for extending the safe storage period of nuclear wastes beyond 100 years, it is critical to ensure that the structural integrity of the storage systems can be maintained for long periods of time. Fiber reinforced cement composites provide an excellent alternative for amelioration, protection, and deterioration prevention of the containment structure based on a demonstrated resistance to corrosion, control of crack propagation and exceptional strength to weight ratios . Lately, with the recent advances in nanotechnology, the use of carbon nanofibers (CNFs) in cement composites has received increasing attention due to the promising potential for the development of superior structural and multifunctional materials . CNFs possess a number of unique properties, such as high specific strength, chemical resistance, and electrical and thermal conductivity, making them excellent candidates for nanoscale reinforcement in cement composites [3, 4]. While most studies to date have been conducted to examine the direct structural, mechanical, and electricalproperties provided by the CNFs [5-7], the long-term chemical and structural stability of these materials in response to severe conditions such as decalcifying environments and the potential impact of the CNF dispersion on the chemo-mechanical behavior of CNF-cement composites has received little attention.
There are recent papers which present the results of research of the composites with nanoscale fillers [14, 15] and its mixtures. Thus, it was shown in  that the addition of carbon nanotubes (CNT) in the CM with carbon black increases conductivity of CM. In addition, carbon black particles also increase the viscosity and crack resistance of nanocomposites, hence confirming a synergistic effect of carbon black as a multifunctional filler. In [17, 18], Zhao et al. investigated composites with carbon nanotubes and graphite nanoplatelets (GNPs). Low percolation transition was observed due to improved interaction between different carbon fillers as a result of a modified process of the samples manufacture. Not indi- vidual particles of carbon fillers are added to the polymer, and graphite nanoplates on which carbon nanotubes are grown and aligned. These structures are considered as one whole hybrid particle, it has a complex morphology.
Thermal interface materials (TIMs) are vital for microelectronics packaging as they are responsible for improving interfacial thermal contacts between components, such as microprocessors, and heat sinks, thus ensuring sufficient heat removal from these components . Conventional TIMs are made by dispersing inorganic fillers such as boron nitride (BN), aluminium nitride or silicon carbide in polymer matrices. These are primarily marketed as thermal pastes. Thermal pastes offer superior thermal interfacial contacts but they have issues of pump-out or dry out from interfaces when exposed to thermal and power cycle resulting in increase in thermal contact resistance which threatens microelectronic devices long term reliability . Polymercomposites are commonly used as adhesive TIMs since, as well as offering good thermal conductivity, their compliant nature suits gap-filling applications thereby improving contacts between the mating surfaces and also binding the surfaces to improve mechanical stability . High thermal conductivity and low thermal contact resistance are the most desirable characteristics of TIMs .
nanoscale. With these superior physical properties, CNTs are very attractive materials for future light weight structural aerospace applications. Recent manufacturing advances have led to the availability of bulk formats of CNTs such as yarns, tapes, and sheets in commercial quantities, thus enabling the development of macro-scale composite processing methods for aerospace applications. The fabrication of unidirectional CNT yarn/polymercomposites and the effect of processing parameters such as resin type, number of CNT yarn layers, CNT yarn/resin ratio, consolidation method, and tension applied during CNT yarn winding on the mechanical properties of unidirectional CNT yarn composites are reported herein. Structural morphologies, electrical and thermal conductivities, and mechanical performance of unidirectional CNT yarn/polymercomposites under tensile and short beam shear loads are presented and discussed. The application of higher tension during the winding process and elevated cure pressure during the press molding step afforded a compact structural morphology and reduced void content in the composite.
Abstract The structural and physico-chemical characteristics of thermoplastic polymers filled with multiwall carbon nanotubes (CNTs) such as polyethylene (PE), polyamide 6 (PA 6) and layered fiberglass with PA 6 are investigated. The influence of their concentrations and homogeneity degree of nanotubes distribution is studied. The properties of new composites are compared with the well investigated polytetrafluoroethylene (PTFE)–CNTs and polypropylene (PP)–CNTs systems. It is shown that an addition of CNTs into thermoplastic polymeric materials leads to the significant changes in structural characteristics, growth of strength, electrical, thermal properties. It is coursed by the formation of CNTs continuous network in the original matrix, the crystallinity degree of the matrix depending on the concentration of CNTs. In turn, the crystallinity degree of the matrix is increased by homogeneity arising of the composite as a result of the strong interaction of the matrix with nanofiller. The changes of not only bulk but also the surface properties of the composites are observed, which explains the best biocompatibility of the nanocomposites observed in natural conditions experiments (in vivo).
thermal, and electricalproperties. However, at the state of the art, their full potential has not been reached when combined with polymer matrices in nanocomposites. In this work, an overview of the research in carbon nanotube-polymer nanocomposites has been provided, with emphases on the principles of carbon nanotube functionalization. Many techniques have been attempted with varying success to functionalize the inherently inert nature of the surface of carbon nanotubes. There are two major approaches, i.e., chemical and physical functionalization. Fluorination, cycloaddition, carbene and nitrene addition, chlorination, bromination, hydrogenation, and silanization belong to the chemical methods that can provide covalent functional groups onto the surface of carbon nanotubes. The physical methods include wrapping of polymer around the carbon nanotubes, use of surfactants of various ionic nature, and the endohedral method. The state of research into carbon nanotube-polymercomposites for mechanical reinforcement has been reviewed, and particular interest is also given to interfacial bonding of carbon nanotubes to polymer matrices as it applies to stress transfer from the polymer matrix to the carbon nanotube. The carbon nanotube-polymer interaction is believed to play an important role in determining the overall properties of the nanocomposites. The interfacial characteristics directly affect the efficiency of carbon nanotube reinforcements in improving thermal, electrical, and mechanical properties of the polymer nanocomposite. The interaction studies in carbon nanotube-polymercomposites have been critically reviewed. Different techniques of measuring interaction, including experimental and modelling methods, were described, and advantages and challenges of each method were discussed. Furthermore, various techniques of interaction improvement were discussed under the two main classes of covalent and noncovalent interactions. The excellent mechanical properties of carbon nanotubes combined with unique transport properties render a huge potential for structural and functional applications of carbon nanotube-polymercomposites. Although numerous studies have dedicated to the development of carbon nanotube-polymercomposites for various purposes, their applications in real products are still in their early stage of realization.
Abstract— I n recent years natural polymers have been widely used in biomedical applications. Application of natural and biocompatible polymers in wound dressing, medical sutures and tissue engineering are extensively growing. Additional properties are provided when metal nanoparticles such as silver and gold are incorporated in to the fibers. However, nowadays nanofibers due to their inherent properties such as higher surface to area with these nanoparticles are used for biomedical application. In this study chitosan has been converted into nanofibers and the effect of silver nanoparticle on the antibacterial properties of the nanocomposite fibers has been investigated. Chitosan (Cs)/poly (vinyl alcohol) (PVA) solutions in 2% (v/v) aqueous acetic acid were electrospun. The effects of different total concentrations of polymer solutions and mass ratios of Cs and PVA on the fibers formation and its morphology have been investigated by SEM. Effect of spinning parameters on the nanofiber diameter have been investigated. Fine nanofibers, without bead were obtained from 8% total concentration of polymer in aqueous acetic acid solution and 40/60 mass ratio of Cs/PVA. To improve the antibacterial properties of nanofibers silver was incorporated in to the electrospinning solution by two different ways ie., i) addition of silver nanoparticles into the electrospinning solution and ii) addition of silver nitrate salt and then reducing it to silver. Antibacterial activity of nanofibers against St.aureus as gram-positive and P.aeruginosa as gram-negative bacteria shows that nanofibers containing silver nanoparticles have stronger antibacterial activity than nanofibers without silver. Moreover, cell culture test shows that cells can grow easily on these nanofibrous webs.
The rapid proliferation of advanced electronic devices for many commercial and military applications, such as data transmission, telecommunications, wireless network systems, and satellite broadcasting as well as radar and diagnostic and detection systems, has led to numerous electromagnetic compatibility and electromagnetic inter- ference (EMI) problems. The interaction of electromag- netic waves originating from different sources can lead to a decrease in quality and a misinterpretation of transferred data, and it has thus become vital to avoid such interference and electromagnetic wave pollution through the use of ap- propriate absorbing and shielding materials. Carbonaceous materials - such as graphite and/or carbon black - are often used as dielectric electromagnetic absorbers, generating di- electric loss by improving the electrical conductivity of the mixture. In particular, nanostructured materials and carbon fiber composites have been the subjects of growing interest