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Lignins are the most important aromatic renewable natural resource today, serving as a sustainable, environmentally acceptable alternative feedstock to fossil‐derived chemicals and polymers in a vast scope of value‐added applications. Lignin is a biopolymeric molecule that, together with cellulose, is a fundamental component of higher vascular plants structural cell walls. It can be extracted from by‐products of the pulp and paper industries, agricultural waste and residues, and biorefinery products. Lignin properties may vary depending on source and extraction method with carbon and aromatic as the main compositions in lignin structure. These rich compositions make lignin more valuable, allowing for the creation of high‐value‐added green composites. However, the complex structure of lignin creates low reactivity to interact with crosslinker, and hence chemical modification is substantial to overcome this problem. This review aimed to present and discuss lignin structure, variation of lignin chemical properties regarding its source and extraction process, recent advances in chemical modification of lignin to enhance its reactivity, and potential applications of modified lignin for manufacturing value‐added biocomposites with enhanced properties and lower environmental impact, such as food handling/packaging, seed coating, automotive devices, 3D printing, rubber industry, and wood adhesives. [ABSTRACT FROM AUTHOR]

The finite availability of petroleum and environmental considerations has given emphasis on the development of raw materials for polymers from renewable resources. Polymers from renewable resources are expected to gain great momentum nowadays as petroleum resources become less secure. The use of biopolymer blends and composites can bring out a revolution in the field of automobile, pharmaceutical, packaging industry, etc. Poly(lactic acid) or polylactide (PLA) is the most extensively researched and utilized biodegradable and renewable thermoplastic polyester, with a potential to replace conventional petrochemical‐based polymers. Besides its relatively high tensile strength and modulus compared to other thermoplastics such as polyethylene terephthalate, polypropylene, the low impact strength and less heat tolerance of the material makes it inadequate for more demanding applications. It is the most promising material for the production of environment friendly high performance products. It is proven to be superior to conventional plastics in terms of energy consumption and carbon dioxide emission in life cycle analysis. The general purpose of this review is to introduce PLA, a compostable, biodegradable thermoplastic made from renewable sources and their blends. In the first part of this review, we briefly discuss the advantages, limitations, production methods of PLA. The second part, the major objective of this paper, focuses on the various toughening modification of PLA and also about PLA based green composites using natural fibers and agricultural residues. It also highlights the major research progress and strategies applied to improve the brittleness of polylactic acid. POLYM. COMPOS., 39:81–101, 2018. © 2016 Society of Plastics Engineers [ABSTRACT FROM AUTHOR]

Exploration of natural fiber‐reinforced polymer composites (NFRPCs) in cutting‐edge applications is due to phenomenal properties, such as lightweight, low‐cost, and environmental aspects. NFs can effectively compete to the synthetic fibers in terms of mechanical, thermal and acoustic properties. As a result, the invention and innovation of natural fiber (NF) composites for commercial purposes has increased dramatically in recent years to meet the growing demand of the industrial sectors. Materials are the cornerstone of any manufacturing industry. NFRPCs are a good alternative to conventional materials because of their relatively high mechanical properties and lower production energy. NFs decrease the cost of the material by 5% while reducing the weight of the composite by 10% and the manufacturing energy by 80%. A lot of work has been done to enhance NFRPCs' mechanical properties to overcome their drawbacks, such as poor fiber‐to‐matrix adhesion, thermal stability, and moisture absorption. However, for better mechanical properties, it is crucial to understand the fibers' embedded manufacturing technique and the appropriate fiber weight percentage with appropriate matrix. This review article discusses composites made of NFs providing a comprehensive and up‐to‐date overview of the field of NFRPCs, focusing on recent advancements in preparation techniques, improvements in mechanical properties such as tensile, flexural and impact strength of NFRPCs with various fiber types, fiber weight ratio, fiber‐to‐matrix ratio for appropriate engineering applications, and elucidating future research directions by analyzing trends and challenges in the field. The aim of this review article is to provide a deep evaluation of the progress made in the field of NFRPCs, with the ultimate goal of advancing knowledge and understanding of this field. [ABSTRACT FROM AUTHOR]

Additive manufacturing (AM) is being used more widely because of the simplicity of the operating procedures. It decreases material consumption during part production and eliminates material waste. Fused deposition modeling (FDM), a well‐known AM process, uses thermoplastic polymer as a feedstock to manufacture the end design. Pure thermoplastic‐based products are still utilized as prototypes in several sectors due to their lack of strength and durability. This problem has been solved by strengthening the thermoplastics by adding a reinforcing element. Composites are made of polymers and various constituents known as reinforcing components. This article overviews natural reinforced polymer composites used in the FDM process. Mechanical and Thermal properties are presented based on natural filler percentage, and this article only considered natural composite filaments for the FDM process. [ABSTRACT FROM AUTHOR]

Hybrid polymer composites (synthetic and/or natural fiber) are highly prominent in the fields of automotive, aerospace, construction, and marine. This work aims at developing a novel epoxy/glass/ramie (EGR) hybrid composite incorporated with ammonium polyphosphate (APP) using a vacuum bag technique, thus by changing the weight percentage of APP. The hybrid composites were characterized for the fire‐retardant (vertical and horizontal burning test), mechanical (hardness, tensile, and flexural testing), wettability, porosity (ethanol infiltration), and vibrational properties. The flammability data show that the hybrid composites made of 10, 15, and 20 weight percentages of APP obtained V‐1, V‐0, and V‐0 grades in the UL‐94 vertical burning test. Furthermore, there is an enhancement in hardness properties, but it reduces the tensile and flexural strength. However, the integration of APP reduces the water absorption rate of the composite from 11% to 5%. This study found that APP‐reinforced EGR hybrid composite improves fire resistance, thereby reducing the water absorption rate, which hikes the usage of the material for structural application. [ABSTRACT FROM AUTHOR]

Research in hybrid and flexible natural fiber‐reinforced polymer composites has included advances in innovative and environmentally sustainable devices. However, in practice, controversies still exist regarding the relationship between electrical and materials performance targets in a system design context. This work aimed to investigate the alternating conductivity of a novel pressure sensor based on semiconducting polyaniline (PANI)‐coated vegetable fiber (VF, Euterpe oleracea Mart., Acai) in silicone polydimethylsiloxane (PDMS) rubber. We used alternating electrical conductivity measurements, σ*(ω) ∝ ωs (frequency range—ω from 1 Hz to 10 MHz; s ~ 0.6), to adjust the optimal operating frequency region to enhance the pressure sensing performance of the PDMS‐PANI‐VF composites. A generalized effective‐medium approach to the pressure‐induced conductivity in terms of loading pressure, percolation regime, and the interpolation between Bruggeman's symmetric and asymmetric media theories was obtained. We have found a solution for inducing percolation in composites with a low concentration of fiber inclusions by uniaxial pressure (P), characterized by the expression σ ∝ (P−P0)t (0 ≤ t ≤ 4.0, 0 ≤ P0 ≤ 250 kPa). The sensor demonstrates maximum sensitivity of 1.5 Pa−1 in the operating electrical frequency from 1 to 100 Hz, and a wide linearity range from 0 to 250 kPa. The result provides new insight into the AC universality, s, and t behaviors of natural fiber‐reinforced polymer composites to enhance pressure sensitivity of a new concept and technology for resource‐efficiency optimization of sustainable environmental devices. [ABSTRACT FROM AUTHOR]

In the present study, polyamide 12 (PA12) and 2,2′‐(1,4‐phenylene)bis(2‐oxazoline) (PBO) were used to modify polyamide 11 (PA11), and then microcrystalline cellulose (MCC) reinforced PA11 composites was prepared via hot pressing. The results showed that the thermoplastic elastomer PA12 was in favor of the toughness of the composites, 12% PA12 increased the impact strength by 53%. The molecular chains of PA11/PA12 blends were extended by PBO, and then had positive effects on the mechanical properties, as evidenced by the fact that the flexural strength and the impact strength of the composites with 0.3% PBO were increased by 13% and 14%, respectively. In addition, morphology analysis indicated PBO was in favor of the interfacial bonding of the composites. MCC significantly increased the flexural strength and modulus by 68% and 283%, respectively. [ABSTRACT FROM AUTHOR]

Healing of bone fractures highly depends on the biocompatibility, stability in biological conditions, biodegradability, technical functionality, and shelf‐life of biomaterials. Metallic biomaterials offer excellent mechanical properties and biocompatibility. However, metallic bone implants result in stress shielding, release of toxic ions, excessive wear, and corrosion. Polymer materials are being explored for bone implants due to their light‐weight, biocompatibility, biodegradability, and absence of stress shielding. In the new era, additive manufacturing (AM) is being preferred due to its capability of fabricating customer specific implants with minimum material wastage. However, AM based polymer implants lack in mechanical strength and biological properties. Surface modification of polymeric substrates using coatings and incorporation of bioadditives have been regarded as alternatives for improvement of mechanical and biological properties. This review discusses about various coating techniques and gives an overview about coatings and bioadditives that can be used for enhancement of properties. From the review, it is evident that reinforcement of hydroxyapatite to polylactic acid resulted in prevention of crack growth during shape recovery cycles which can be used for self‐fitting implants. Coatings have been successful in enhancing hydrophilicity, mechanical properties, anti‐biofouling, antibacterial and anti‐coagulative properties, adhesion, proliferation, and differentiation of cells on the coated surface. This review also discusses the challenges that need to be overcome for progression in this field. [ABSTRACT FROM AUTHOR]

The utilization of eco‐friendly and biodegradable natural biopolymers is globally expanding due to environmental problems caused by non‐degradable synthetic polymers. This study examined the physical, mechanical, and antibacterial properties of corn starch‐based films incorporated with Hibiscus sabdariffa L. extract (HE) and different concentrations (0.5, 1, and 1.5 wt% of starch) of graphene oxide (GO). The addition of HE and GO into the starch matrix resulted in increased thickness, moisture content, solubility, and swelling degree in the composite films. FTIR spectrum proved intermolecular interactions among starch, HE, and GO. Moreover, SEM images showed that films presented a continuous surface without cracks and bubbles, without separation of phases between starch, HE, and GO verifying the compatibility of the constituents in the film matrix. On the other hand, the addition of the plant extract and GO significantly reduced the tensile strength of the films (except the film containing 0.5% GO) and increased the percentage of elongation at break. Furthermore, all films displayed strong antibacterial activity against both the Gram‐positive and Gram‐negative bacteria. Obtained results suggest that the novel antibacterial starch films incorporated with HE and GO are promising to be used as wound dress or food coating. [ABSTRACT FROM AUTHOR]

In this study, a novel hybrid system containing lignin and cellulose nanocrystals (CNC) is developed to reinforce natural rubber (NR) and produce high‐performance biocomposites. Firstly, the effect of lignin content in lignin/NR biocomposites is investigated. Despite lignin's advantages as an inexpensive biopolymer, its addition to NR results in longer cure time, reduced tensile strength and increased loss factor (tan δ); that is, lignin addition has a negligible reinforcing effect compared to conventional fillers, such as carbon black (CB). On the other hand, adding only 7.5 parts per hundred rubber (phr) of CNC to lignin/NR compounds decreased the curing time (14%) and loss factor (55% at 10% strain), while increasing the bound rubber content (37%), modulus at 100% strain (101%) and tensile strength (36%). CNC/lignin/NR bionanocomposites exhibited comparable mechanical properties and even better dynamical mechanical properties (53% lower loss factor at 10% strain) than conventional composites reinforced with CB. The optimum lignin content in the NR composite was 40 phr, while the percolation threshold for CNC was around 7 phr. [ABSTRACT FROM AUTHOR]

Environmental awareness across the world has motivated researchers to focus their attention on the use of cellulosic fiber as reinforcement in polymer matrices. Lignocellulosic fibers are an abundantly available resource in all countries, which is cheap and easily renewable. Also, due to their properties, cellulosic plant fibers exhibit a great potential for use in polymer reinforcement. As a result, considerable research and development efforts have been directed towards the use of cellulosic fibers as a reinforcing material in composites. The use of cellulosic fiber reinforced composites has continuously increased during recent years, which benefits the cultivation of fiber plants and the economy of the country. This research area continues to be of interest to both industry and academia, the use of cellulosic fibers in composite applications being investigated throughout the world. Cellulosic fiber reinforced composites are reasonably strong, lightweight, harmless to human health and the environment, and biodegradable, hence they have the potential to be used in various applications. Recent progress in cellulosic fiber composites research has illustrated their great potential as structural components in automobiles, aerospace structures, construction, and building, and so forth. This study is an effort to create awareness about the research works that have been published in the field of natural fiber composites. This review briefly illustrates the main paths and results of major research published in the field of natural fiber reinforced polymer composites. The topics covered include the aspects of fiber treatment to improve the mechanical properties of the composites, manufacturing methods, performance of hybrid composites, effect of laminate configuration, and many different applications of natural fiber composites. By presenting a systematic view of the work performed in this area so far, this review will hopefully serve as a starting point for the development of new ideas in the research on natural fiber polymer composites. [ABSTRACT FROM AUTHOR]

In recent days, natural fiber reinforced polymer composite is more popular due to its extensive properties suitable for various potential applications. The attention towards natural fibers is because of low cost, biodegradable, recyclability, nonabrasive, combustible, lightweight, and nontoxic properties. However, there is a need for furthermore fundamental knowledge for the raw materials processing and fabrication of composite structures, which is still challenging in current days. Natural fiber sources exist all over the world, which is obtained from animals, plants and minerals. The quality of the natural fibers depends on the extraction methods and different processing techniques. These natural fibers surface characteristics could be enhanced by selecting suitable surface treatment and chemical treatment. These fiber treatments reduce the water intake percentage, improve the adhesive nature, and enhance the overall performance of resulting polymer composites. Among all the chemical treatments, alkaline treatment (NaOH) is the most preferred chemical treatment because of its effectiveness and its low cost. This review article proposes the natural fibers detailed classification, composition, structure, properties, and extraction methods, chemical and surface treatments. We also summarize the previous research work findings on the fibers treatment, properties of natural/natural hybrid polymer composites and natural/synthetic hybrid polymer composites with applications. [ABSTRACT FROM AUTHOR]

Poly‐ether‐ether‐ketone (PEEK) possesses excellent biocompatibility and similar elastic modulus as bones but suffers from poor osseointegration; usually, the addition of hydroxyapatite (HA) is considered as an effective way to improve the osseointegration of PEEK implant interface. To investigate the effect of HA content and particle size on the mechanical behaviors and osteogenesis in vitro of PEEK‐HA composites, the PEEK‐HA specimens with variable HA content and particle size have been fabricated by powder mixing‐heat press method and characterized by mechanical and biological tests. The results showed that the tensile/bending strength and elongation at break of PEEK‐HA are significantly impaired as the increasing HA amount, but the modulus improves. The compressive strength and modulus are improved as the increasing amount of HA. The PEEK‐HA with smaller HA particle size possesses higher‐performance tensile/bending and lower‐performance compressive properties. In osteogenesis tests in vitro, the results reveal that the cells amount attached on the substrate rises and the cells flatten more evenly with numerous cytoplasmic processes on greater area with the increasing HA content and decreasing particle size. The PEEK‐HA group that HA content is 20 wt% and particle size is 20 nm exhibits optimal‐performance osteogenesis in vitro, while maintaining sufficient mechanical properties. [ABSTRACT FROM AUTHOR]

The continuous delivery of E‐waste from petroleum‐based products creates ecological and environmental problems due to non‐biodegradable polymers, which release harmful chemicals and toxic gases. This results in biodegradable polymers/fibers appearance, which are biocompatible and degrade in the surrounding environments without causing any environmental pollution and these relieve environmental burden. However, the bio‐based materials are unable to meet certain properties in the way of flexibility, dielectric properties, electrical properties, water and gas vapor barrier properties. The current day's research focus is towards the implementation of biodegradable composites properties by introducing different nanostructures. The biopolymers/biofibers are used as raw material in concern with environmental aspects. Nowadays researchers are supplementing a new form of materials known as nanofillers in various biopolymer‐based composites in a small amount. This nanofillers will act as additives and helps in enhancing the different properties such as mechanical, thermal, flame retardancy and water absorption behavior of the nano composite materials as well as maintaining the optimum density of them. The nanocomposites applications are extended in various sectors for the reason of higher surface area, aspect ratio, and superior properties. This review outlines the types of biofibers/biopolymers and their characterization, types of nanofillers, and their characterization, and summarizes the various functional properties of nanocomposites with their applications. [ABSTRACT FROM AUTHOR]

The demand for plastic packaging material has continued to increase worldwide, a phenomenon that had led to more negative impacts on the environment, especially waste pollution issues caused by the petrochemical industry producing plastics and polymers. As a result, this research aimed to study the production of biodegradable packaging by blending polylactic acid (PLA) and polybutylene succinate (PBS) with 5–20% (w/w) sweet bamboo (Dendrocalamus asper Backer) kraft pulp (SKP). Subsequently, several analyses were used to evaluate the biopolymer properties to determine if the composite could be used to produce biodegradable packaging. The addition of SKP 5% (w/w) provided the PLA/PBS composite with the highest thermal and mechanical properties. Furthermore, the effect of a plasticizer was studied by combining 5%, 10%, or 15% (w/w) Mesamoll in the PLA/PBS composite with 5% (w/w) SKP. This addition changed all composite properties and in particular provided good water vapor barrier properties. Finally, this research revealed that SKP plays a role as a nucleating agent in plasticized PLA/PBS composite. [ABSTRACT FROM AUTHOR]

In recent times, the field of biopolymer (BP) blends has been the focus of intensive fundamental and applied researches. Such BP combinations possess unique properties that are different from those of the individual components. However, most polyester polymers are thermodynamically immiscible because of their poor interactions. In the past, a third component, known as a well‐defined diblock or triblock copolymer, whose chemical structure is identical to that of the main components, was usually used as a compatibilizer in order to emulsify the interfacial phase, decreasing the interfacial tension and refining the phase size. Currently, nanofillers are used to improve the phase morphologies of immiscible BP blends. The main advantage of using nanofillers, when compared to copolymers, is that the former can simultaneous act as nano‐reinforcements and compatibilizers. In this review, the addition of nanofillers as the third component in the BP blend systems are reported in relation to their morphologies, barrier properties, shape memory, thermal, and mechanical properties. The effects of selectively localized nanofillers on the properties of the BP blends are also explored, with the aim of establishing the relationships between the localization of the fillers and the overall properties of the BP blends. Furthermore, the effect of the processing techniques on the localization of the nanofillers/BP blend is also reported. The review article discusses recent progress from 2014 up to 2019 on filler localization of BP blend nanocomposites. [ABSTRACT FROM AUTHOR]

In recent years, biopolymers are getting wide attention with the perspective of developing high‐performance biocomposites with low environmental impact owing to their unique and useful features such as abundant availability, renewability, eco‐friendliness and lightweight. Biopolymer composites are expected to replace many conventional materials in optical, biological, and engineering applications as the investment and research on these materials increase substantially. The desired properties of biopolymer composites can be achieved by blending an appropriate biopolymer with suitable additives, which pave the way for polymer‐filler interaction. A variety of parameters such as chemical composition, degradation kinetics and mechanical properties of biopolymer composites can be tailored according to the application needs. The interfacial interactions between the biopolymer and the nanofiller have a significant effect on the mechanical properties of biopolymer composites. The present review is focused on the recent advances in the mechanical properties of various biopolymer composites. In the first part of this review, the unfamiliar mechanical characterization techniques such as fatigue test, nanoindentation and nondestructive testing of biopolymer composites have been discussed. In the later part, the various popular processing techniques of biocomposite fabrication have been discussed. In addition, in the conclusion section, few challenges associated with the processing and mechanical performance of biopolymer composites have been described. [ABSTRACT FROM AUTHOR]

The poor thermo‐mechanical and flame‐retardant properties of biopolymers are currently limiting their application and potential exploitation as sustainable polymers. The use of agricultural by‐products as a functional filler for biopolymers is here presented to address the production of environmentally friendly and economically sustainable biocomposites. To this aim, hemp hurd and alfalfa particles were melt‐blended with a poly(3‐hydroxybutyrate‐co‐3‐hydroxyhexanoate) (PHB) co‐polymer. The 30 wt% of filler achieves an improvement of 150% in stiffness. The same composites show an increase in the heat deflection temperature over 100°C. Flame‐retardant properties were also evaluated evidencing strong reductions in flame spread rates (−40%) and combustion kinetics (−30%). The achieved performances are compared with those reported in the literature for PHB composites pointing out how these completely renewable materials can compete with other currently studied solutions. The new presented composites show an opportunity for the production of functional and sustainable materials through the valorization of agricultural by‐products. POLYM. COMPOS., 40:3429–3437, 2019. © 2019 Society of Plastics Engineers [ABSTRACT FROM AUTHOR]

Proton Exchange Membranes (PEMs) based on nanocomposite consisting of Chitosan and Poly (ethylene oxide) (PEO)/modified montmorillonite (H+‐MMT) was prepared by solution casting technique. To appraise PEM performance, the structural properties, hydrolytic stability and transport properties of the prepared membranes were investigated using various characterization methods like FT‐IR, XRD, SEM, AFM, water uptake, swelling ratio, ion exchange capacity (IEC), and proton conductivity measurements. Fabricated blend membranes showed favorable PEM characteristics such as afford comparable proton conductivity, moderate ion exchange capacity and reasonable water uptake. Proton conductivities of the blend membranes are about 2.99 × 10−2 S/cm at room temperature. All the membranes are homogenous that could be revealed from the XRD studies. All the results obtained from this study can be used to conclude that the Chitosan/PEO membrane with H+‐MMT filler is a promising high performance PEM candidate for fuel cell applications in future. POLYM. COMPOS., 40:E301–E311, 2019. © 2017 Society of Plastics Engineers [ABSTRACT FROM AUTHOR]

Short‐running of mineral oil, the increasing waste problem and the raising consciousness of our society are increasing biopolymer's potential for becoming an important alternative for petroleum based plastics. However, applications of biopolymers are still limited, which is partly caused by insufficient properties and high prices of some biopolymers. This study focuses on a polymer blend of poly(3‐hydroxybutyrate‐co−3‐hydroxyvalerate) and poly(butylene adipate‐co‐terephthalate) which is reinforced with organomodified montmorillonite. Moreover, two natural propolis additives and an industrial antimicrobial are added to the materials with the objective to convey them antimicrobial properties. The effect of environmental factors such as water absorption, aging by weathering test, and antimicrobial attack on the thermal behavior and colorimetry of the biopolymer nanocomposites is investigated. These results contribute to the understanding of the structure‐property relationship of biocomposite materials for various applications, e.g. in packaging. POLYM. COMPOS., 39:915–923, 2018. © 2016 Society of Plastics Engineers [ABSTRACT FROM AUTHOR]

Depletion of petroleum resources, together with increasing environmental concerns, calls for new solutions for many of our needs such as fuels, heating, materials, technical oils, and so on. Because of the ubiquitous use of petroleum-based products in their persistence in the environment and their fossil-fuel derived, alternatives to these traditional plastics are being explored. Totally, 'green' biomaterials are of extra interest. Thus, strong composites containing both 'green fibers' from plants and 'green/biopolymers' from plants would be an ideal solution and they represent an emerging area in polymer science. Introduction and production of these composites into the material market would be important for environmental sustainability as their use can decrease the volume of petroleum-derived plastic waste dumps. This article reviews the current research efforts, techniques of production, trends, challenges, and prospects in the field of green composites from protein-based polymers. Green composites are comparatively cheap and abundant, but further research and development is needed for a broader utilization. POLYM. COMPOS., 38:1504-1518, 2017. © 2015 Society of Plastics Engineers [ABSTRACT FROM AUTHOR]