Advances in Piezoelectric Polymer Composites for Energy Harvesting Applications: A Systematic Review

Polymeric piezoelectric composites for energy harvesting applications are considered a significant research field which provides the convenience of mechanical flexibility, suitable voltage with sufficient power output, lower manufacturing cost, and rapid processing compared to ceramic‐based composites. This review focuses majorly on the basic theory and principles behind piezoelectric energy harvesting (PEH) devices, followed by specified materials used for the different devices. Different structural configurations associated with fabrication of PEH devices are discussed in detail along with their major advantages and drawbacks. Numerous classes of piezoelectric polymers such as polyvinylidene fluoride, polylactic acid, cellulose, polyamides, polyurea, polyurethanes, and their composites used for energy harvesting applications as a productive alternative of lead‐based piezo‐ceramics, are extensively addressed and explored. Additionally, current global and Indian scenarios associated with PEH devices, major challenges associated with them, and the future perspective of such devices are also reported in this review.     

Processing and properties of polymeric nano‐composites

Polymeric nano‐composites are prepared by melt intercalation in this study. Nano‐clay is mixed with either a polymer or a polymer blend by twin‐screw extrusion. The clay‐spacing in the composites is measured by X‐ray diffraction (XRD). The morphology of the composites and its development during the extrusion process are observed by scanning electron microscopy (SEM). Melt viscosity and mechanical properties of the composites and the blends are also measured. It is found that the clay spacing in the composites is influenced greatly by the type of polymer used. The addition of the nano‐clay can greatly increase the viscosity of the polymer when there is a strong interaction between the polymer and the nano‐clay. It can also change the morphology and morphology development of nylon 6/PP blends. The mechanical test shows that the presence of 5–10 wt.% nano‐clay largely increases the elastic modulus of the composites and blends, while significantly decreases the impact strength. The water absorption of nylon 6 is decreased with the presence of nano‐clay. The effect of nano‐clay on polymers and polymer blends is also compared with Kaolin clay under the same experimental conditions.     

Improvement of mechanical properties of structural thermoplastic composites using a reactive (low molecular weight) matrix component

An innovative manufacturing process for continuous fiber composites with the polymeric matrix made up of polypropylene and epoxy resin, as a model reactive low molecular weight component, was developed; variable process parameters give rise to different morphologies of matrix components surrounding the woven fabric reinforcement. Furthermore, the combination of both thermoplastic and thermosetting polymers permitted intimate fibers impregnation, typical of thermosetting matrix composites, with short process cycle time, which usually occurs in manufacturing process of thermoplastic matrix composites. Polypropylene (PP) films, glass fibers fabric, and epoxy resin film were used to produce flat composite through film‐stacking technique. The preparation process focused on control of both epoxy resin cure process and polypropylene melting. The process was able to induce the two matrix components to form either a planar (sandwich‐like) structure or a three‐dimensional (3D) network by means of controlling the process parameters such as pressure and heating rate. The strong enhancement of the mechanical properties (Young's modulus and tensile strength of the composites with the 3D structure were almost twice as high of those of the composites with sandwich‐like matrix structure) was due to the different microstructures produced by the interplanar flow of the thermoplastic polymer. POLYM. COMPOS., 31:1762–1769, 2010. © 2010 Society of Plastics Engineers.     

The Synthesis of Urchin‐Like Serried Hydroxyapatite (USHA) and its Reinforcing Effect for Dental Resin Composites

The novel urchin‐like serried hydroxyapatite (USHA) is synthesized by homogeneous hydrothermal precipitation method through adjusting the pH value and temperature. The silanized USHA is thereby used as the reinforcing filler for dental resin composites. The structure and morphology of various HA nanostructures are characterized with X‐ray diffraction, Fourier transform infrared spectroscopy, and field‐emission scanning electron microscope. Thermogravimetric analysis is used to analyze the grafting ratio of 3‐methacryloxypropyl trimethoxysilane on the surface of USHA. Mechanical performance of dental resin composites reinforced with silanized USHA at different filler loadings are measured by a universal mechanical testing machine. The neat resin matrix is served as the control group. Results demonstrate that the optimization of USHA morphology gave a better understanding of the effect of the pH value and temperature on its structure transformation. After trials, USHA with the complete globular structure and the serried whiskers is synthesized at pH value of 12.5 under 105 °C. When the USHA loading is 30 wt%, the corresponding dental composite significantly improved the mechanical properties in comparison with the neat resin, especially for the compressive strength.     

Mechanically adaptive cellulose‐poly(acrylic acid) polymeric composites in wet–dry cycles

Polymeric composites consisting of cellulose and poly(acrylic acid) (PAA) are prepared by coagulation/bulk polymerization method. Scanning electron microscopy and thermal gravimetric analysis are used to investigate the homogeneity and the heat‐induced water loss of the composites, respectively. The water absorbed in the composites has strong hydrogen bonding with the polymer chains, as determined by differential scanning calorimetry. The mechanical and structural properties of the composites vary reversibly when the composites are applied into specifically explored wet–dry cycles, which are comprehensively measured by dynamic mechanic analysis, wide‐angle X‐ray diffraction, and Fourier transform infrared. It is unprecedented to explore the cellulose‐PAA composites as a mechanical adaptive material. The cellulose and the PAA chemically react with each other. Most of the cellulose content remains in amorphous state. Thus, the water molecules can diffuse into the composites, leading to the wet–dry mechanical adaptability of the composites. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Polythiophene‐based materials for nonvolatile polymeric memory devices

Polymeric materials used in memory devices have attracted significant scientific interest due to their several advantages, such as low cost, solution processability, and possible development of three‐dimensional stacking devices. Polythiophenes, including tethered alkyl substituted polythiophenes and block copolymers, poly(3,4‐ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) and composites, are one of the most attractive polymeric systems for memory applications because of their commercial availability, high conductivity, and mechanical strength. In this article, recent studies of functional polythiophene for memory applications are reviewed, mostly focusing on the role of the materials in the memory functionality, optimizing the chemical structure of the polythiophene and the component of each layer in memory device. A critical summary of the proposed mechanisms, including filament formation, electric field‐induced charge transfer and reduction‐oxidation (redox) driven, is given to explain the resistive switching phenomena in the polythiophene system. In addition, the challenges facing the research and development in the field of polythiophene electronic memories are summarized. POLYM. ENG. SCI., 54:2470–2488, 2014. © 2013 Society of Plastics Engineers     

An electrical approach to monitor wire and cable thermal oxidation aging condition based on carbon black filled conductive polymer composite

Polymeric materials are widely used as insulation and jacketing materials in wire and cable. When such materials are used for long‐term applications, they undergo thermal oxidation aging in the environment. It is necessary to develop an in situ and nondestructive condition monitoring (CM) method to follow the aging of cable materials. The main objective of this work was to investigate low‐density polyethylene/carbon black (LDPE/CB) conductive polymer composites as potential sensor materials for this purpose. LDPE/CB composites with a carbon black loading below the percolation threshold underwent accelerated thermal oxidation aging experiments. The results indicated that the substantial resistivity decreases of the LDPE/CB composites could be directly related to the increases in volume fraction of the conductive carbon black, which was mainly caused by the mass loss of polymer matrix and sample shrinkage during the thermal oxidation aging process. Compared to existing CM method based on density change, the electrical resistivity is more explicit regarding its absolute changes throughout the thermal oxidation aging. The change in resistivity spanned over four orders of magnitude, whereas the composite density only increased 10%. The results offer strong evidence that resistivity measurements, which reflect property changes under thermal aging conditions, could represent a very useful and nondestructive CM approach as well as a more sensitive method than density CM approach. Crystallinity changes in materials investigated by modulated DSC and TGA measurements indicated deterioration of crystalline regions in polymer during the thermal oxidation aging. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 513–520, 2004     

Polystyrene/vinyl ester resin/styrene thermoplastic elastomer composites: Miscibility,morphology, and mechanical properties

Polystyrene/Styrene‐Ethylene‐Propylene‐Styrene/Vinyl Ester Resin (PS/SEPS/VER) blends used as matrix of ultra high molecular weight polyethylene (UHMWPE) fiber‐reinforced composites, which included both physical crosslinking points of thermoplastic resin SEPS and chemical crosslinking network of thermosetting resin PS/VER, were prepared by solution blending and hot‐molding. Morphology and mechanical properties of the PS/SEPS/VER composites were investigated in this work. The microstructure of PS/SEPS/VER composites observed by means of scanning electron microscopy (SEM) was correlated with mechanical properties. It is worth noting that, stiffness increased sharply with the addition of VER within a certain range. Impact properties verified the structure that the physical crosslinking points of SEPS were immersed in the chemical crosslinking network of PS/VER. Dynamic mechanical analysis revealed that, incorporation of VER changed the storage modulus and loss tangent. In brief, addition of VER had improved mechanical properties, thermal stability, and fluidity of the composites during processing, indicating a successful result for preparing resin matrix material with outstanding comprehensive performances. Analog map was presented to facilitate better understanding of the special structure of PS/SEPS/VER. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Light‐weight polypropylene composites reinforced with whole chicken feathers

Light‐weight composites reinforced with whole chicken feathers have better flexural strength than composites reinforced with feather fibers (barbs) and nearly thrice higher tensile strength and seven times higher tensile modulus than composites reinforced with powdered chicken feather quill. Chicken feathers are not only inexpensive and abundantly available but also have unique properties such as low density and hollow centers that make them preferable as reinforcement materials, especially for light‐weight composites. However, the traditional methods of developing composites do not provide the flexibility of using feathers in their native form as reinforcement. So far, the components in feathers such as barbs or quills have been used separately and/or feathers have been mechanically processed to destroy their native form in order to use feathers as reinforcement in composites. A new method of making composites using nonwoven webs as matrix allows the incorporation of reinforcing materials in their native form such as whole chicken feathers to develop composites. This research shows that whole chicken feathers can be used as reinforcement in composites with better flexural, tensile, and acoustic properties than composites made from processed chicken feathers. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Incorporation of 4‐aminobenzene functionalized multi‐walled carbon nanotubes in polyaniline for application in formic acid electrooxidation

Incorporation of carbon nanotubes (CNTs) in conducting polymer can lead to new composites with enhanced electrical and mechanical properties. However, the development of such composites has been hampered by the inability to disperse CNTs in polymer matrix due to the lack of chemical compatibility between polymers and CNTs. Covalent sidewall functionalization of carbon nanotube provides a feasible route to incorporate carbon nanotube in polymer. In this work, 4‐aminobenzene groups were grafted onto the surface of multi‐walled carbon nanotube (MWNT) via C? C covalent bond. Polyaniline (PANI)/MWNT composites were fabricated by electrochemical polymerization of aniline containing well‐dissolved functionalized MWNTs. The obtained composites can be used as catalyst supports for electrooxidation of formic acid. Cyclic voltammogram results show that platinum particles deposited in PANI/MWNT composite films exhibit higher electrocatalytic activity and better long‐term stability towards formic acid oxidation than that deposited in pure PANI films. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Elastic properties of large‐open‐mesh 2D braided composites: Model predictions and initial experimental findings

Conventional applications of two‐dimensional tubular braided composites mostly require closed‐mesh braiding; however, some stiffness‐critical applications may require use of open‐mesh braiding. Most likely candidates for the open‐mesh braided composites are in the medical field, such as braided catheters and stents. Analytical and experimental investigation of the open‐mesh braided tubular composites is very limited in the open literature; therefore, this study is an initial attempt to close this gap. The article investigates elastic properties of the open‐mesh braided composites (e.g., braided catheters) and open‐mesh composites with holes (i.e., stent‐like structures). Analytical results are also compared with that of experimental results. Findings may be used in design of braided medical tubular composites. POLYM. COMPOS., 31:2017–2024, 2010. © 2010 Society of Plastics Engineers     

Thermoplastic vibration welding: Review of process phenomenology and processing–structure–property interrelationships

Vibration welding offers a robust method for physically joining thermoplastics to fabricate complex hollow assemblies from simpler injection‐molded articles without using an external heat source, adhesives, or mechanical fasteners. Vibration welding involves a complex interplay of several phenomena—solid (Coulomb) friction, melting, high strain‐rate, pressure‐driven, strong (high‐strain) melt flows, solidification, and microstructure development—which ultimately govern the strength and integrity of the weld. Defects in the weld region may lead to catastrophic failure of the welded assembly. In this article, the current understanding of the processing–structure–property relationships in the context of vibration welding of thermoplastics and polymer‐matrix composites is reviewed. Experimental as well as analytical methods of investigation of the vibration welding process phenomenology are presented. The interrelationships between the microstructure in the weld region and the resulting weld strength and fatigue behavior are then discussed in the light of this phenomenological information for neat polymers, filled polymers, polymer blends, and foams. This review is also aimed at identifying the areas requiring further investigation with regard to understanding vibration welding phenomenology and weld structure–property relationships. POLYM. ENG. SCI., 2011. © 2010 Society of Plastics Engineers     

Conductivity study on semicrystalline and amorphous polymers filled with conducting additives

Summary Polymeric conducting composites were obtained on the basis of polypropylene and polystyrene and conducting fillers (iron, copper and carbon black). The materials obtained by means of physical blends of the components were characterized through complex impedance diagrams. The respective data provided evidence of the fact that the conduction mechanism of such composites depends both on the chemical and structural properties of the polymeric matrix and on the nature of the conducting additive.     

Bioinspired Design of LDH‐Based Mobile Building Materials with Enhanced Mechanical and Ultraviolet‐Shielding Performance

Glass fiber reinforced polytetrafluoroethylene composites (PTFE/GF composites) with the excellent performance have been given considerable attention due to their increasing applications in large architecture areas such as stadiums, amusement parks, parking lots, etc. However, the brittleness of glass fiber can hinder the performance of PTFE/GF composites. The PTFE/MLDH (modified ZnAl‐layered double hydroxide)/GF composites inspired by layer‐layer structure are prepared via the multi‐layered dipping method, which consists of GF acting as a reinforcement, PTFE acting as matrix, and MLDH acting as the layer‐layer structure. The results of study show that the high strength and surperflexibility of PTFE/MLDH/GF composites are higher than pure PTFE/GF composites. Especially, when the PTFE/MLDH/GF composites contain 1.6 wt% MLDH, the folding endurance reaches up to 39 035 times, the tensile strength reaches up to 163.57 MPa, and strain reaches up to 8.33%. More significantly, the strength and surperflexibility are illustrated by a mechanism model and it is used to further broaden the application of PTFE/GF composites in mobile building materials. Moreover, it is discovered that the PTFE/MLDH/GF composites have unique translucent performance and excellent ultraviolet‐shielding properties in this study, which further broaden its range of applications.     

Cassava: Its polymer,fiber, composite,and application

Cassava is a type of plant which has different purposes of use. It is used to produce various foods, bio‐fibers, bio‐composites, and bio‐polymers. Besides, it is now used as renewable energy source of starch. The intention of the paper is to focus on the importance of cassava fibers, polymers, and composites as well as its potential applications, another focus point of this research is the biodegradable polymer development which is taken out from cassava starch. Moreover, this work gives a comprehensive review about surface treatments as well as the most recent developments of cassava polymer/fiber based bio‐composites and the summary of main result presented in the literature, focusing on properties of cassava composite and applications. These applications were related to various industrial application as well as others such as the production of xylenes, ethanol and bio‐fuel, food, food packaging and cassava foam . POLYM. COMPOS., 38:555–570, 2017. © 2015 Society of Plastics Engineers     

Comparative evaluation of different methods of inclusion of silver into sulfadiazine‐based polyurethane urea composites

This paper approaches two series of composites: one series incorporating silver nanopowder in sulfadiazine‐based polyurethane urea through a solution‐dispersion method, and another series of composites incorporating silver sulfadiazine in the hard domain of the main chains of the polyurethane. The morphology, structure, and physical properties of these silver composites with different hard segment structures were characterized and compared. It was found that using silver sulfadiazine as a chain extender causes an orderly dispersion of the silver ions along the backbone chain. This leads to an improvement in all properties for these composites, as opposed to composites which incorporated silver nanopowder. Thus, this paper expands on the development of a new and simple method of including silver during the synthesis reaction of the polymer matrix, by chain extension with silver sulfadiazine. Using silver sulfadiazine as a chain extender ensures the repartition of the silver on the molecular backbone chain which allows the silver ions to retain specific properties, unlike other composites which tend to lose silver over time through surface migration. POLYM. COMPOS., 38:2156–2165, 2017. © 2015 Society of Plastics Engineers     

Lignin‐polystyrene composite foams through high internal phase emulsion polymerization

The composites made‐up from renewable fillers and polymer matrix have drawn great attention due to the renewable nature, improved thermal and mechanical properties, environmental issues and most importantly to reduce dependency on fossil fuel resources. In this work, kraft lignin in its modified form (butylated lignin) was used to make composites with polystyrene successfully through bulk polymerization and high internal phase emulsion (HIPE) polymerization. The kraft lignin was first modified to butyrated lignin by esterification using 1‐Methylimidazole as a catalyst in order to increase the compatibility as fillers with both monomer and polymer, which was further studied and verified through Hansen solubility parameter model. The thermal, mechanical, and structural properties of the lignin/polymer composites were systematically investigated. The incorporation of lignin in the composites could increase the modulus significantly and almost double (1,391 MPa) at 15 wt% of lignin loading as compared with bare composites. Excellent porous structure and mechanical properties are maintained with the lignin content as high as 10 wt% of the total foam mass. POLYM. ENG. SCI., 59:964–972, 2019. © 2018 Society of Plastics Engineers     

Jute‐fiber‐reinforced polyurethane green composites based on Mesua ferrea L. seed oil

Two types of environmentally friendly jute‐fiber‐reinforced green composites based on Mesua ferrea L. were prepared with poly(urethane ester) and poly(urethane amide) resin blends with commercially available partially butylated melamine–formaldehyde and epoxy resins through solution impregnation and hot‐curing methods. The composites were cured at a temperature of about 130–140°C under a pressure of 35 ± 5 kg/cm² for about 2 h. The mechanical properties, such as tensile strength, flexural strength, elongation at break, hardness, and density, of all of the composites were measured and compared. The mode of interaction between the filler and the matrix were studied by Fourier transform infrared spectroscopy and scanning electron microscopy of the fractured composite samples. The water uptake in different chemical media was observed, and we found that all of the composites possessed excellent hydrolytic stability against almost all of the media except the alkali. Thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) were used to analyze the thermal behavior of the composites. TGA of the composites showed degradation much above that of the virgin blends, which indicated their high thermostability. The glass‐transition temperatures, as shown by DSC analysis, were found to be much higher. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Effects of filler geometry on internal structure and physical properties of polycarbonate composites prepared with various carbon fillers

BACKGROUND: The effects of filler geometry are important for understanding the internal structure and physical properties of polymer composites. To investigate the effects of filler geometry on electrical conductivity as well as morphological and rheological properties, three types of polycarbonate (PC) composites were prepared by melt compounding with a twin‐screw extruder. RESULTS: The electrical conductivity of PC/carbon black (CB) and PC/graphite (carbon) nanofibre (CNF) composites did not show a percolation threshold through the entire filler loading ranges. However, PC‐blend‐carbon nanotube (CNT) composites showed a percolation electrical threshold for a filler loading of 1.0 to 3.0 wt% and their maximum electrical conductivity approached 10^?3 S m^?1. PC‐blend‐CB and PC‐blend‐CNF composites showed Newtonian behaviour like pure PC matrix, but PC‐blend‐CNT composites showed yield stress as well as increased storage modulus and strong shear thinning behaviour at low angular frequency and shear rate due to strong interactions generated between CNT–CNT particles as well as PC molecules and CNT particles on the nanometre scale. CONCLUSIONS: The electrical conductivity of the PC composites with different carbon constituents was well explained by the continuous network structure formed between filler particles. The network structure was confirmed by the good dispersion of fillers as well as by the yield stress and solid‐like behaviour observed in steady and dynamic shear flows. Copyright © 2009 Society of Chemical Industry     

Synthesis of bio‐based polymeric nanocomposites from acrylated epoxidized soybean oil and montmorillonite clay in the presence of a bio‐based intercalant

Polymeric nanocomposites were synthesized from functionalized soybean‐oil‐based polymer matrix and montmorillonite (MMT) clay using an in situ free radical polymerization reaction. Acrylated epoxidized soybean oil combined with styrene was used as the monomer. Organophilic MMT (OrgMMT) was obtained using a quaternized derivative of methyl oleate, which was synthesized from olive oil triglyceride, as a renewable intercalant. The resultant nanocomposites were characterized using X‐ray diffraction and atomic force microscopy. The effect of increased nanofiller loading on the thermal and mechanical properties of the nanocomposites was investigated using thermogravimetric analysis and dynamic mechanical analysis. It was found that the desired exfoliated nanocomposite structure was achieved when the OrgMMT loading was 1 and 2 wt%, whereas a partially exfoliated or intercalated nanocomposite was obtained for 3 wt% loading. All the nanocomposites were found to have improved thermal and mechanical properties as compared with virgin acrylated epoxidized soybean‐oil‐based polymer matrix. The nanocomposite containing 2 wt% OrgMMT clay was found to have the highest thermal stability and best dynamic mechanical performance. Copyright © 2010 Society of Chemical Industry