Recent advances in bio‐sourced polymeric carbohydrate/nanotube composites

Nanotubes (NTs), especially carbon nanotubes (CNTs), have attracted much attention in recent years because of their large specific surface area, and their outstanding mechanical, thermal, and electrical properties. In this review we emphasize the development of fascinating properties of polymeric carbohydrate/CNT composites, particularly in terms of their mechanical and conductivity properties and potential applications. Many methods used to modify CNTs during preparation of polymeric carbohydrate/CNT composites are presented. Moreover, we also discuss the enhanced mechanical and electrical effectiveness when hybrid CNTs or halloysite nanotubes were incorporated into different carbohydrate polymer matrices. Finally, we give a future outlook for the development of polymeric carbohydrate/CNT composites as potential alternative materials for various applications including sensors, electroactive paper, electrodes, sorbents for environmental remediation, packaging film, specialty textile, and biomedical devices. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40359.     

Studies on thermal degradation and flame retardant behavior of the sisal fiber reinforced unsaturated polyester toughened epoxy nanocomposites

Unsaturated polyester (UP) toughened nanocomposites were prepared using both sisal fibers and montmorillonite clays. The effect of fibers and Cloisite 30B (C30B) nanoclays on the mechanical properties, thermal stability, flame retardant, and morphological behavior of the UP toughened epoxy (Epoxy/UP) were systematically studied. The chemical structures of Epoxy, UP, and Epoxy/UP systems were characterized using Proton Nuclear magnetic resonance (¹HNMR) and Fourier transform infrared (FTIR) spectra. The homogeneous dispersion of nanoclay within the polymer matrix was analyzed using transmission electron microscopy (TEM) and X‐ray diffraction (XRD) analysis. Incorporation of sisal fibers and C30B nanoclays within Epoxy/UP system resulted in an increase in the mechanical, thermal, and flame retardance properties. Thermogravimetric analysis (TGA) has been employed to evaluate the thermal degradation kinetic parameters of the composites using Kissinger and Flynn‐Wall‐Ozawa methods. Cone calorimeter, UL‐94, and LOI tests revealed a reduction in the burning rate of the matrix with the addition of fibers and nanoclays. The results showed that the treated fiber reinforced nanocomposites had higher thermal stability and better flame retardant properties than the treated fiber reinforced composites. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42068.     

Olive leaf extract as a crosslinking agent for the preparation of electrospun zein fibers

Incorporating active agents, reinforcing structure by crosslinking, thus changing release properties, can be listed as possible modifications in preparation methods of biopolymer fibers. This study introduces oleuropein, major component of olive leaf extract (OLE), as a natural functional crosslinker for electrospun zein fibers, owing to its antioxidant and antimicrobial properties. Incorporation of OLE causes morphological and structural changes indicated by a decrease in fiber diameter up to 27%, an increase in intensity of NH bending region due to interaction with –OH groups and observation of characteristic oleuropein bands. Extract addition also enhances thermal stability. Zein fibers without OLE is fully degraded at 600°C, whereas 10% of OLE loaded zein fibers is left undegraded. Fifty percent of initial phenolic content loaded into fibers is released which indicate the effect of OLE incorporation as accumulation of oleuropein. OLE‐incorporated fibers immersed in PBS are less fused than pure zein fibers, due to the crosslinking effect. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41338.     

Effect of nanoclay on physical,mechanical, and microbial degradation of jute‐reinforced,soy milk‐based nano‐biocomposites

Jute‐reinforced, soy milk‐based nano‐biocomposites were fabricated using both natural and organically modified nanoclay to study their effect on physical, mechanical, and degradation properties. Different weight percentages of nanoclays were used to modify soy milk by solution casting process. The jute fibers were then impregnated in modified soy resin and compressed to fabricate nano‐biocomposites. About 5 wt% of organically modified nanoclay‐loaded jute composite showed maximum tensile and flexural strength. X‐ray diffraction and transmission electron microscopy (TEM) analysis of fabricated composites confirmed about the formation of nanostructure. Impact, microhardness, dynamic mechanical analysis results of nano‐biocomposites revealed that nanoclay has influenced to improve such physical and mechanical properties. Microbial degradation study of nano‐biocomposites was carried out in cultured fungal bed. Weight loss, tensile loss, and field emission scanning electron microscopy photographs of composites revealed that composites are biodegradable in nature. The prime advantages of these composite are their eco‐compatibility as jute and soy resin, the basic constituents of composites are biodegradable in nature. These composites can be utilized in automobile, packaging, furniture sectors by replacing nondegradable plastic‐based composite. POLYM. ENG. SCI., 54:345–354, 2014. © 2013 Society of Plastics Engineers     

Thermal,mechanical, and gas barrier properties of ethylene–vinyl alcohol copolymer‐based nanocomposites for food packaging films: Effects of nanoclay loading

For the application of single‐layer food packaging films with improved barrier properties, an attempt was made to prepare ethylene‐vinyl alcohol (EVOH) copolymer‐based nanocomposite films by incorporation of organically modified montmorillonite nanoclays via a two‐step mixing process and solvent cast method. The highly intercalated tactoids coexisted with exfoliated clay nanosheets, and the extent of intercalation and exfoliation depended significantly on the level of clay loadings, which were confirmed from both XRD measurements and TEM observations. It was revealed that the inclusion of nanoclay up to an appropriate level of content resulted in a remarkable enhancement in the thermal, mechanical (tensile strength/modulus), optical, and barrier properties of the prepared EVOH/clay nanocomposite films. However, excess clay loadings gave rise to a reduction in the tensile properties (strength/modulus/elongation) and optical transparency due to the formation of clay tactoids with a larger domain size. With the addition of only 3 wt % clay, the oxygen and water vapor barrier performances of the nanocomposite films were substantially improved by 59 and 90%, respectively, compared to the performances of the neat EVOH film. In addition, the presence of clay nanosheets in the EVOH matrix was found to significantly suppress the moisture‐derived deterioration in the oxygen barrier performance, implying the feasibility of applying the nanocomposite films to single‐layer food packaging films. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40289.     

The TiO2–Clay-LDPE Nanocomposite Packaging Films: Investigation on the Structure and Physicomechanical Properties

The role of nanoclays and TiO₂ nanoparticle loadings were investigated on low density polyethylene crystalline structure, in addition to studying packaging film properties such as barrier, thermal and mechanical properties. The polymer crystal study indicated for the orthorhombic crystal phase and about 20% lower degree of crystallinity for nanocomposites containing more than 2 wt.% TiO₂ nanoparticles. Based on the X-ray diffraction technique, the dispersion of nanoclays was improved to almost good degree of clay exfoliation with the company of 4 wt.% TiO₂ nanoparticles. In agreement with XRD results, the TEM morphological studies mainly suggest that TiO₂ has a helpful effect on nanoclay exfoliation. The increase in degradation temperature of nanocomposites may be attributed to the formation of inorganic char on polymer melt. The barrier properties of TiO₂/clay nanocomposite packaging films depend mainly on nanoclay loading with an unclear trend from TiO₂ nanoparticles. The increase in elastic modulus and the yield stress of nanocomposite films showed great effects on film mechanical properties by nanoclays.     

Hybrid biomimetic electrospun fibrous mats derived from poly(ε‐caprolactone) and silk fibroin protein for wound dressing application

To achieve excellent biofunctionality of Bombyx mori silk fibroin (SF), we explored a novel hybridization method to combine the unique properties of SF with poly(ε‐caprolactone) (PCL) electrospun fibers. The hybrid electrospun fibers demonstrate excellent hydrophilicity and biocompatibility that are important to tissue engineering applications. The biomimetic fibrous structure was fabricated by conventional electrospinning of PCL. The individual surfaces of PCL electrospun fibers were coated with silk fibroin protein using a lyophilization technique. The SF coating layers were durable which were further developed by surface modification with fibronectin to improve their biological function. The hybrid electrospun fibers show excellent support for normal human dermal fibroblast (NHDF) cells adhesion and proliferation than neat PCL fibers, while the surface‐modified hybrid electrospun fibers show significantly enhanced proliferation of NHDF cells on their surface. This study indicates the new opportunity of fabrication technique that can construct a biomimetic fibrous structure while the original function as a biomaterial remained existing. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41653.     

Nanoclay and long-fiber-reinforced composites based on epoxy and phenolic resins

In this study, high-performance thermoset polymer composites are synthesized by using both long fibers and nanoclays. Epoxy and phenolic resins, the two most important thermoset polymers, are used as the polymer matrix. The hydrophobic epoxy resin is mixed with surface modified nanoclay, while the hydrophilic phenolic resin is mixed with unmodified raw nanoclay to form nanocomposites. Long carbon fibers are also added into the nanocomposites to produce hybrid composites. Mechanical and thermal properties of synthesized composites are compared with both long-fiber-reinforced composites and polymer- layered silicate composites. The optimal conditions of sample preparation and processing are also investigated to achieve the best properties of the hybrid composites. It is found that mechanical and thermal properties of epoxy and phenolic nanocomposites can be substantially improved. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Zein‐based ultrathin fibers containing ceramic nanofillers obtained by electrospinning. I. Morphology and thermal properties

This work presents the first results on the development and characterization of novel nanobiocomposite fibers prepared by electrospinning of zein/clay mixtures (from 99/1 to 75/25 wt/wt) from ethanol‐based solutions. To do so, commercial ceramic materials of different nature, such as organomodified and unmodified mica, kaolinite, montmorillonite, and zeolite were employed and compared. A significant decrease in fiber diameter was observed as the clay fraction increased in the hybrid material. The highest clay contents also produced fibers but with extended beaded regions. All fillers nanodispersed well in the fibers at low loadings but unmodified mica particles were also seen excluded from the fibers, most likely due to excessive size. Surprisingly, the ceramic laminar structures, i.e. the phyllosilicates, were all seen to embed within the ultrathin fibers in what appears as an unreported rolled morphology due to the extensional forces generated by the electrospinning process. Electrospun nanobiocomposite fibers with optimal ceramic nanoparticle contents are currently investigated as an adequate procedure to prepare naturally occurring composite additives, coatings, and interlayers with enhanced performance in terms of mechanical, thermal, barrier, and control release properties for packaging, active packaging, biomedical, and pharmaceutical applications. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Multifunctional polymer materials with enhanced mechanical,thermal and gamma radiation shielding properties from dicyanate ester of bisphenol-A/bisphenol-A based benzoxazine resin and short kevlar/basalt hybrid fibers

In execution of obtaining outstanding functional materials that possess the features of advanced mechanical behaviour, high thermal resistance and enhanced gamma radiation shielding properties, this present article aimed to boost qualitatively and quantitatively the desired performances of dicyanate ester of bisphenol-A/bisphenol-A based benzoxazine resin using hybrid fibers consisting of kevlar fibers and basalt fibers. To achieve this, the desired amounts of the hybrid fibers were initially surface treated using the silane coupling agent technique and then incorporated within the blend matrix with a total weight selected to be 40 wt%. According to the mechanical results, a noteworthy increase in the flexural and impact strength properties of the reinforced hybrid composites was chiefly observed as compared to the unfilled samples’ properties. Based on the thermal stability studies, the reinforced hybrid composites also showed excellent thermal resistances. The hybrid composites’ shielding properties, which were evaluated using a Cobalt-60 (⁶⁰Co) as an irradiation source, revealed outstanding gamma-radiation shielding enhancements. The scanning electron microscope confirmed that the improvements in the investigated properties were essentially ascribed to the good dispersion and interfacial adhesion of the two high-performance hybrid fibers within the blend matrix with respect to their advanced properties. Therefore, the enhanced mechanical, thermal and nuclear shielding properties promote the use of the as-developed hybrid composites in domestic and industrial applications.     

Are nanoclay-containing polymer composites safe for food packaging applications?—An overview

The growth in polymer-based innovative packaging technology has brought about a revolution in extending the shelf life of many food and aquatic products. One of the emerging areas in this field is polymer nanocomposite (PNC) technology, which involves the incorporation of various chemicals and nanoadditives into polymers to improve their inherent properties or to add required functionality. Because the nanoparticles may interact with food components during processing, storage, or distribution and may migrate into food, PNC-based packaging materials require awareness and understanding of their potential impact on human health and the environment. Interest in migration and cytotoxic analysis of PNC has gained considerable momentum in recent years. The focus of this article is on clay-containing PNCs because the global trend in PNCs shows that 50% of all nanofillers constitute nanoclays of either natural or synthetic origin. This article presents a summary of perspectives on international regulations on test parameters and migration of chemicals from materials that come into contact with food, followed by a critical review of (1) complaints concerning the polymers, compatibilizers, and adhesive tie layers used in polymeric packages, (2) migration of constituents from PNC-based films/articles, and (3) toxicity evaluation of nanoclays and migration of nanoclays from PNCs. Finally, we believe a review article of this nature will help academic and industrial researchers who want to bring advanced PNC-based products into the market for food packaging applications. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47214.     

Experimental study of shrinkage and ejection forces of reinforced polypropylene based on nanoclays and short glass fibers

This study presents the influence of nanoclays and glass fibers on the shrinkage and ejection forces of polypropylene‐based composites for tubular parts produced by injection molding. An instrumented mold was used to measure cavity pressure, surface temperature and ejection forces in the tubular parts during the injection cycle. The materials used for the study were polypropylene homopolymer Domolen 1100L, nanoclays for polyolefin nanocomposites (P‐802 nanoMax, used in percentages of 2%, 6%, and 10%) and reinforced polypropylene homopolymer with a content of 10% and 30% glass fiber (Domolen P1‐013‐V10‐N and Domolen P1‐102‐V30‐N, respectively). Part shrinkage was measured 48 h after production. The results show that the incorporation of nanoclays reduces shrinkage and ejection forces while glass fibers decrease shrinkage and increase ejection forces due to an increase in elastic modulus. Nanoclays decrease the ejection forces when compared to glass fibers and pure PP. The effects of nanoclays are less pronounced than those of glass fibers. Moldings produced with different materials were also analyzed to assess the effect of mold temperature on the ejection forces. Shrinkage rises slightly by increasing the mold temperature while the ejection force decreases. POLYM. ENG. SCI., 58:55–62, 2018. © 2017 Society of Plastics Engineers     

Mechanical,thermal, and dielectric properties of aluminum nitride/glass fiber/epoxy resin composites

The treated hybrid fillers of aluminum nitride/glass fibers (AlN/GF) were performed to prepare the AlN/GF/epoxy composites by casting method. Results showed that the flexural and impact strength of the composites were increased firstly, but decreased with the excessive addition of AlN. The mechanical properties were optimal with 5 wt% treated AlN. The thermal conductivities of the composites were improved with the increasing content of AlN, and the thermal conductive coefficient λ was 1.412 W/mK with 70 wt% treated AlN, about seven times higher than that of pure epoxy resin. The dielectric constant and dielectric loss of the composites were increased with the increasing content of AlN. For a given AlN/GF hybrid fillers loading, the surface treatment of AlN/GF hybrid fillers exhibited a positive effect on the mechanical properties and thermal conductivities of the composites. POLYM. COMPOS., 35:381–385, 2014. © 2013 Society of Plastics Engineers     

Oxidation Transitions for SiC Part II. Passive‐to‐Active Transitions

Oxidation of SiC can occur in a passive mode, where a protective film is generated, or in an active mode, where a volatile suboxide is generated. The transitions from active‐to‐passive and passive‐to‐active are particularly important to understand as they occur via different mechanisms. In Part II of this article, the passive‐to‐active transition is explored. Three different types of SiC are examined—Si‐rich SiC, stoichiometric SiC, and C‐rich SiC. In addition to an in situ transition from passive‐to‐active, the effect of a preformed film on all three types of SiC is explored. It appears that the passive‐to‐active transition occurs when the SiO₂ scale begins to react with the SiC substrate. This reaction generates SiO(g) and CO(g), which build pressure beneath the SiO₂ scale, eventually causing the oxide to rupture. In addition, the SiO(g) can oxidize a distance away from the surface leading to the formation of SiO₂ needles and further promoting this SiO₂/SiC reaction. Thermodynamic and kinetic data are used to predict transition pressures of oxygen, which show reasonable agreement with those measured.     

Pullulan‐based films and coatings for food packaging: Present applications,emerging opportunities,and future challenges

Societal and industrial demands for lower environmental impact, cost effectiveness, and high‐performance goods and services are increasingly impacting the choice of technologies which are developed and deployed in consumer products. Like many other sectors, food packaging is moving to new technologies; the use of biopolymers is one of the most promising strategies toward an optimized use of traditional packaging materials (e.g., oil‐based plastics) without impairing the goal of extending shelf life. Among other food packaging materials, pullulan is attracting much attention due to its unique features. The goal of this review is to provide an overview of current and emerging applications of pullulan within the food packaging sector. In particular, the functional properties of interest for the food packaging industry will be discussed in light of the physicochemical attributes of this exopolysaccharide. Future challenges that may dictate the successful penetration of pullulan in the food packaging market are also outlined. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40539.     

Synthesis,characterization and properties of cellulose‐grafted glycine derivatives

Novel Schiff base cellulose derivatives were successfully prepared by a bridge‐coupling reaction from dialdehyde cellulose (DAC), which was obtained by the selective oxidation of sodium periodate to cotton fibers, in which the glycine (Gly) was bonded onto the DAC chains by a Schiff base reaction with p‐nitrobenzaldehyde as a bridge. The structures of the graft copolymer (DAC‐g‐Gly) were characterized by Fourier transform infrared spectroscopy, X‐ray diffraction, solid‐state NMR, and scanning electronic microscopy. The thermodynamic properties were analyzed by thermogravimetric analysis and differential scanning calorimetry, and the biodegradability was also tested by the microbial degradation and the active sludge method. The results indicate that Gly was connected to DAC by chemical bonding, which changed the thermal stability, and that DAC‐g‐Gly could be biodegraded significantly. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40929.     

The influence of cinnamon and litsea cubeba essential oils on methylcellulose films

The aim of this study was to prepare active, biodegradable methylcellulose films and evaluate their properties after incorporating cinnamon (Cinnamomum cassia) and litsea cubeba (Litsea cubeba) essential oils. The properties of the methylcellulose films were modified with the addition of essential oils. The surfaces were smooth and homogeneous in all samples. The film with cinnamon oil showed higher antibacterial activity against Staphylococcus aureus and Escherichia coli and the film with litsea cubeba showed higher antioxidant activity against ABTS radical. The biodegradation time of the films in black sand and beach soil was 20 days. The films produced that presented the highest potential to become active packaging were the film with litsea cubabe oil as antioxidant packaging and the film with cinnamon oil as antibacterial packaging.     

LDPE/clay/carvacrol nanocomposites with prolonged antimicrobial activity

Over the past decade there is an immense effort to develop antimicrobial packaging systems, which incorporates natural biopreservatives, such as essential oils (EOs). The highly volatile nature of EOs, which is advantageous for their efficient diffusion and mode of action, presents a major obstacle for their incorporation with polyolefins via conventional high‐temperature melt compounding and processing. This study presents a new approach to use organo‐modified montmorillonite (MMT) clays, as active carriers for carvacrol (used as a model EO), aiming to minimize its loss throughout the polymer compounding. Different MMT clays are pretreated with carvacrol, resulting in the oil molecules intercalation in between the clay galleries and enhanced carvacrol thermal stability. These hybrids are incorporated within low‐density polyethylene (LDPE) and the resulting films are characterized in terms of their nanostructure, thermal properties, and antimicrobial activity. The LDPE/(clay/carvacrol) nanocomposites exhibit excellent and prolonged antimicrobial activity against E. coli bacteria, while LDPE/carvacrol films loss their antimicrobial functions within several days. The superior antimicrobial behavior is ascribed to the significantly higher carvacrol content and its enhanced thermal stability within the films. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41261.     

Effect of nanoclay on electrical and mechanical properties of polyurethane conductive coatings filled with nickel‐coated carbon fibers

There is a considerable amount of researches focused on the properties of nanocomposite containing nanoclays, yet there were only few studies about nanoclay conductive coatings. The influence of montmorillonite nanoclay on the electrical and mechanical properties of polyurethane conductive coatings filled with nickel‐coated carbon fibers was investigated in this study. Moreover, the role of nanoclay with regard to the resistivity of coatings with different conductive fillers or different resins, the effects of resin to hardener ratio and mixing time on the resistivity and hardness of coatings were also evaluated. POLYM. ENG. SCI., 54:1120–1125, 2014. © 2013 Society of Plastics Engineers     

Extrusion processing of green biocomposites: Compounding,fibrillation efficiency,and fiber dispersion

The efficiency of twin‐screw extrusion process to fibrillate cellulose fibers into micro/nanosize in the same step as the compounding of green bionanocomposites of thermoplastic starch (TPS) with 10 wt % fibers was examined. The effect of the processing setup on micro/nanofibrillation and fiber dispersion/distribution in starch was studied using two types of cellulose fibers: bleached wood fibers and TEMPO‐oxidized cellulose fibers. A composite with cellulose nanofibers was prepared to examine the nanofiber distribution and dispersion in the starch and to compare the properties with the composites containing cellulose fibers. Optical microscopy, scanning electron microscopy, and UV/Vis spectroscopy showed that fibers were not nanofibrillated in the extrusion, but good dispersion and distribution of fibers in the starch matrix was obtained. The addition of cellulose fibers enhanced the mechanical properties of the TPS. Moisture uptake study revealed that the material containing TEMPO‐oxidized fibers had higher moisture absorption than the other composites. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39981.