Recent progress on preparation and properties of nanocomposites from recycled polymers: a review

A review of plastic waste nanocomposites: assessment of features and applications

Hundreds of millions of metric tons of plastic waste are generated globally every year. Processing waste into secondary raw material is preferred over energy production and landfilling. However, mechanical recycling generally deteriorates the properties of plastic waste limiting its range of potential applications. Nanocomposite fabrication is a solution to recycle plastic waste into value-added applications due to improved properties generated by nanomaterial reinforcement, however received little study. The aim of this review is to present the current status, identify research gaps and provide topics for further research of polymer nanocomposites prepared from plastic waste in respect to utilized materials, processing methods, enhanced properties, sustainability, economics, nanomaterial safety, and applications. It is found that morphological, mechanical, thermal, flame retardancy, physical, barrier, electrical and shielding properties of plastic waste can be enhanced with low loadings of different nanomaterials making them promising materials for various applications including electronic, shielding, thermal, packaging, filtration, and water treatment. Utilization of plastic waste instead of virgin polymers can be beneficial in respect to economics and sustainability, but the energy intensive and expensive production of the most nanomaterials, and the plastic waste pretreatment methods can negate these benefits. To enhance sustainability, further research should be conducted on utilization of energy friendly nanomaterials in plastic waste nanocomposites. Further research is needed also on polymer nanocomposite safety because of the unknow composition of the plastic waste and the potential for nanomaterial release during nanocomposite's life cycle. All in all, further research and national regulations and guidance are needed on virgin polymer and plastic waste nanocomposites.

Lattice Matching and Microstructure of the Aromatic Amide Fatty Acid Salts Nucleating Agent on the Crystallization Behavior of Recycled Polyethylene Terephthalate

To solve the decrease in the crystallization, mechanical and thermal properties of recycled polyethylene terephthalate (rPET) during mechanical recycling, the aromatic amide fatty acid salt nucleating agents Na-4-ClBeAmBe, Na-4-ClBeAmGl and Na-4-ClAcAmBe were synthesized and the rPET/nucleating agent blend was prepared by melting blending. The molecular structure, the thermal stability, the microstructure and the crystal structure of the nucleating agent were characterized in detail. The differential scanning calorimetry (DSC) result indicated that the addition of the nucleating agent improved the crystallization temperature and accelerated the crystallization rate of the rPET. The nucleation efficiencies (NE) of the Na-4-ClBeAmBe, Na-4-ClBeAmGl and Na-4-ClAcAmBe were increased by 87.2%, 87.3% and 41.7% compared with rPET which indicated that Na-4-ClBeAmBe and Na-4-ClBeAmGl, with their long-strip microstructures, were more conducive to promoting the nucleation of rPET. The equilibrium melting points (Tm0) of rPET/Na-4-ClBeAmBe, rPET/Na-4-ClBeAmGl and rPET/Na-4-ClAcAmBe were increased by 11.7 °C, 18.6 °C and 1.9 °C compared with rPET, which illustrated that the lower mismatch rate between rPET and Na-4-ClBeAmGl (0.8% in b-axis) caused Na-4-ClBeAmGl to be the most capable in inducing the epitaxial crystallization and orient growth along the b-axis direction of the rPET. The small angle X-ray diffraction (SAXS) result proved this conclusion. Meanwhile, the addition of Na-4-ClBeAmGl caused the clearest increase in the rPET of its flexural strength and heat-distortion temperature (HDT) at 20.4% and 46.7%.

Multifactorial evaluation of an ultra-fast process for electrospinning of recycled expanded polystyrene to manufacture high-efficiency membranes for nanoparticle air filtration

The increased production of polystyrene waste has led to the need to find efficient ways to dispose of it. One possibility is the use of solid waste to produce filter media by the electrospinning technique. The aim of this work was to develop an ultra-fast electrospinning process applied to recycled polystyrene, with statistical evaluation of the influence of polymeric solution parameters (polymer concentration and percentage of DL-limonene) and process variables (flow rate, voltage, and type of support) on nanoparticle collection efficiency, air permeability, and fiber diameter. An extensive characterization of the materials and evaluation of the morphology of the fibers was also carried out. It was found that recycled expanded polystyrene could be used in electrospinning to produce polymeric membranes. The optimized condition that resulted in the highest nanoparticle collection efficiency was a polymer concentration of 13.5%, percentage of DL-limonene of 50%, voltage of 25 kV, and flow rate of 1.2 mL/h, resulting in values of 99.97 ± 0.01%, 2.6 ± 0.5 × 10-13 m2, 0.19 Pa-1, and 708 ± 176 nm for the collection efficiency of nanoparticles in the range from 6.38 to 232.9 nm, permeability, quality factor, and mean fiber diameter, respectively. All the parameters were found to influence collection efficiency and fiber diameter. The use of DL-limonene, a natural solvent, provided benefits including increased collection efficiency and decreased fiber size. In addition, the electrostatic filtration mechanism was evaluated using the presence of a copper grid as a support for the nanofibers. The findings demonstrated that an electrospinning time of only 5 min was sufficient to obtain filters with high collection efficiencies and low pressure drops, opening perspectives for the application of polystyrene waste in the development of materials with excellent characteristics for application in the area of atmospheric pollution mitigation.

Effect of Rice Husk and Wood Flour on the Structural, Mechanical, and Fire-Retardant Characteristics of Recycled High-Density Polyethylene

Given the rising consumption of plastic products, it is becoming imperative to prioritize the recycling of plastic items as a solution to reducing plastic waste and environmental pollution. In this context, this research focuses on assessing the impact of incorporating rice husk and wood flour into recycled high-density polyethylene (rec-HDPE) to analyze its mechanical properties, flammability, and thermal stability. The combined rec-HDPE content of wood flour and rice husk varied between 0% and 20%. The rec-HDPE content of maleic anhydride grafted polyethylene (MAPE) was fixed at 3%. Mechanical characteristics such as flexural, tensile, and impact strengths were assessed. Cone calorimetry (CC) tests, limited oxygen index (LOI) tests, and horizontal and vertical burning tests were performed to determine the flammability or fire retardancy of these composites. On the other hand, to characterize the thermal characteristics of these composites, thermogravimetric analysis (TGA) was used. To further characterize the fluctuation in these characteristics, scanning electron microscopy (SEM) and infrared spectroscopy (FTIR) studies were carried out. The mechanical characteristics were found to be increased in response to adding rice husk or wood flour. An 8% increase in tensile strength and a 20% increase in elastic modulus enhancement were recorded for a 20% rice husk-added composite. SEM revealed the reason for the variation in tensile properties, based on the extent of agglomeration and the extent of uniform distribution of fillers in rec-HDPE. Following these lines, the 20% rice husk-added composite also showed a maximum increase of around 6% in its flexural strength and a maximum increase of 50% in its flexural modulus. A decrease in impact strength was recorded for rice husk and wood flour-reinforced composites, compared with unreinforced rec-HDPE. Hybrid composites displayed a lack of mechanical strength due to changes in their nature. FTIR tests were performed for a much more elaborate analysis to confirm these results. Twenty percent of rice husk-added rec-HDPE displayed the best thermal properties that were tested, based on TGA and derivative thermogravimetric (DTG) analysis. This 20% composite also displayed the best fire-retardancy characteristics according to UL 94 tests, cone calorimetry tests, and limited oxygen index tests, due to the barrier created by the silica protective layer. These tests demonstrated that the incorporation of both fillers-rice husk and wood flour-effectively enhanced the thermal, mechanical, and fire-retardant attributes of recycled HDPE.

Thermal and mechanical characterization of composite materials from industrial plastic wastes and recycled nylon fibers for floor paving tiles application

Industrial plastic waste is growing globally at an alarming rate and environmental pollution from traditional landfill disposal and incineration treatments are of great concern. As a strategy to reduce plastic pollution, value-added composite materials from industrial plastic wastes reinforced with recycled nylon fibers for use in floor paving tile applications were developed. This is to address the disadvantages of existing ceramic tiles which are relatively heavy, brittle, and expensive. The plastic waste composite structures were produced via compression molding technique at an optimized randomly oriented constant fiber volume fraction of 50 wt% after the initial sorting, cleaning, drying, pulverizing, and melt-mixing. The molding temperature, pressure, and time for the composite's structures were 220 ℃, 65 kg.cm^-3, and 5 min respectively. The composites' thermal, mechanical, and microstructural properties were characterized in accordance with appropriate ASTM standards. From the results obtained, the differential scanning calorimetry (DSC) of mixed plastic wastes and nylon fiber wastes showed a processing temperature range of 130-180 ℃, and 250 ℃ respectively. Thermal degradation temperature (TGA) of the plastic and nylon fiber waste composites were stable above 400 ℃ with maximum bending strength, however, the reinforced plastic waste sandwiched composite structures had outstanding mechanical properties indicating unique characteristics suitable for floor paving tiles. Hence, the current research has developed tough and lightweight tiles composites that are economically viable, and their application will contribute to the development of the building and construction sectors thereby reducing about 10-15% of annual plastic waste generation and a sustainable environment.

The Effect of the Addition of Copper Particles in High-Density Recycled Polyethylene Matrices by Extrusion

In this study, the effect of the recycling process and copper particle incorporation on virgin and recycled pellet HDPE were investigated by thermo-chemical analysis, mechanical characterization, and antibacterial analysis. Copper particles were added to pellet HDPE, virgin and recycled, using a tabletop single screw extruder. Some copper particles, called copper nano-particles (Cu-NPs), had a spherical morphology and an average particle size near 20 nm. The others had a cubic morphology and an average particle size close to 300 nm, labeled copper nano-cubes (Cu-NCs). The thermo-chemical analysis revealed that the degree of crystallization was not influenced by the recycling process: 55.38 % for virgin HDPE and 56.01% for recycled HDPE. The degree of crystallization decreased with the addition of the copper particles. Possibly due to a modification in the structure, packaging organization, and crystalline ordering, the recycled HDPE reached a degree of crystallization close to 44.78% with 0.5 wt.% copper nano-particles and close to 36.57% for the recycled HDPE modified with 0.7 wt.% Cu-NCs. Tensile tests revealed a slight reduction in the tensile strength related to the recycling process, being close to 26 MPa for the virgin HDPE and 15.99 MPa for the recycled HDPE, which was improved by adding copper particles, which were near 25.39 MPa for 0.7 wt.% copper nano-cubes. Antibacterial analysis showed a reduction in the viability of E. coli in virgin HDPE samples, which was close to 8% for HDPE containing copper nano-particles and lower than 2% for HDPE having copper nano-cubes. In contrast, the recycled HDPE revealed viability close to 95% for HDPE with copper nano-particles and nearly 50% for HDPE with copper nano-cubes. The viability of S. aureus for HDPE was lower than containing copper nano-particles and copper nano-cubes, which increased dramatically close to 80% for recycled HDPE with copper nano-particles 80% and 75% with copper nano-cubes.

Recycling and Reutilizing Polymer Waste via Electrospun Micro/Nanofibers: A Review

The accumulation of plastic waste resulting from the increasing demand for non-degradable plastics has led to a global environmental crisis. The severe environmental and economic drawbacks of inefficient, expensive, and impractical traditional waste disposal methods, such as landfills, incineration, plastic recycling, and energy production, limit the expansion of their applications to solving the plastic waste problem. Finding novel ways to manage the large amount of disposed plastic waste is urgent. Until now, one of the most valuable strategies for the handling of plastic waste has been to reutilize the waste as raw material for the preparation of functional and high-value products. Electrospun micro/nanofibers have drawn much attention in recent years due to their advantages of small diameter, large specific area, and excellent physicochemical features. Thus, electrospinning recycled plastic waste into micro/nanofibers creates diverse opportunities to deal with the environmental issue caused by the growing accumulation of plastic waste. This paper presents a review of recycling and reutilizing polymer waste via electrospinning. Firstly, the advantages of the electrospinning approach to recycling plastic waste are summarized. Then, the studies of electrospun recycled plastic waste are concluded. Finally, the challenges and future perspectives of electrospun recycled plastic waste are provided. In conclusion, this paper aims to provide a comprehensive overview of electrospun recycled plastic waste for researchers to develop further studies.

Low-Mass Liquid Crystalline Materials Blended in Recycled Thermoplastic Polyester Elastomer for Corrosion Inhibitor Application

In this work, the development and application of multicomponents obtained from recycled polyethylene terephthalate (r-PET) waste and monotropic liquid crystals as anticorrosion coatings are reported. The r-PET raw material was alcoholyzed and reproduced as a thermoplastic polyester elastomer (TPEE) with different amounts (n%, n = 0, 1, 3, and 5) of 1,6-hexanediamine (HDA). Then, a fluorine-containing liquid crystal (4-cyano-3-fluorophenyl 4-ethylbenzoate (4CFE)) was incorporated into the TPEE mixture via solvent blending to modify and enhance the water resistance. The adhesion behavior of the coating on glass and iron substrates was evaluated by cross-cut tests and immersion tests in aqueous NaCl. In the corrosion resistance measurements, all of the coating samples fabricated with 10 ± 1 mm thickness were less active toward electrochemical corrosion (P_EF% > 99%) than the bare iron plate, indicating that our work provided better protection against corrosion of the iron plate.

Comparative Analysis of Carbon, Ecological, and Water Footprints of Polypropylene-Based Composites Filled with Cotton, Jute and Kenaf Fibers

Composites containing natural fibers are considered environmentally friendly materials which is related to the reduced use of fossil fuels and the emission of carbon dioxide compared to petroleum-based polymers. Nevertheless, a complete evaluation of their environmental impact requires a broader view. This paper presents a carbon, ecological, and water footprints assessment of polypropylene-based composites filled with cotton, jute, and kenaf fibers based on a standardized European pallet (EUR-pallet) case study. Obtained results were compared with unmodified polypropylene and composite with glass fibers. Incorporation of 30 wt% of cotton, jute, and kenaf fibers into a polypropylene matrix reduced its carbon footprint by 3%, 18%, and 18%, respectively. Regarding the ecological footprint, an 8.2% and 9.4% reduction for jute and kenaf fibers were noted, while for cotton fibers, its value increased by 52%. For these footprints, the use of jute and kenaf fibers was more beneficial than glass fibers. Nevertheless, the application of natural fibers caused a 286%, 758%, and 891% drastic increase of water footprint of the final product, which was mainly affected by cultivation and irrigation of crops. Therefore, in a holistic view, the incorporation of natural fibers into the polypropylene matrix definitely cannot be impartially considered as an environmentally friendly solution.

Challenges of plastic waste generation and management in sub-Saharan Africa: A review

Recently, the issues of land-based plastics and their associated challenges in the marine world have been widely publicised in the media and scientific literature. Thus far, despite these communications, there have been few reports that have focused on the issues that acute plastic waste generation and its poor management pose to human health and the global environment. Also, articles on ways to mitigate these issues particularly in sub-Saharan Africa have not been documented. Indeed, there is significant scope for improvements in plastic waste management in developing countries, which offer a wide range of economic and environmental benefits. Plastic waste generation in sub-Saharan Africa is dependent on many factors like urbanization, etc. Currently, the population of sub-Saharan Africa is around 1 billion as of the year 2019, the amount of generated waste is 180 million tonnes at the rate of 0.5% per capita per day, the amount that is openly dumped is 70% and the plastic waste generated annually is 17 million tonnes. Therefore, this study aims to provide an overview of the plastic lifecycle and problems associated with plastic waste management in sub-Saharan Africa, including current practices, public participation and opinion, and government regulations. In addition, this highlight aims to outline the impact of plastic waste proliferation on man and the environment; and the economic and environmental benefits of proper plastic waste management. Critical discussion of current processes and the suitability of potential solutions provide the basis for proposition on mitigation measures to avert the negative impact of plastic waste.

Nanosheet composed of gold nanoparticle/graphene/epoxy resin based on ultrasonic fabrication for flexible dopamine biosensor using surface-enhanced Raman spectroscopy

Construction of a fast, easy and sensitive neurotransmitters-based sensor could provide a promising way for the diagnosis of neurological diseases, leading to the discovery of more effective treatment methods. The current work is directed to develop for the first time a flexible Surface-Enhanced Raman Spectroscopy (SERS) based neurotransmitters sensor by using the ultrasonic-assisted fabrication of a new set of epoxy resin (EPR) nanocomposites based on graphene nanosheets (GNS) using the casting technique. The perspicuous epoxy resin was reinforced by the variable loading of GNS giving the general formula GNS/EPR1-5. The designed products have been fabricated in situ while the perspicuous epoxy resin was formed. The expected nanocomposites have been fabricated using 3%, 5%, 10%, 15% and 20% GNS loading was applied for such fabrication process. The chemical, physical and morphological properties of the prepared nanocomposites were investigated by using Fourier transforms infrared spectroscopy, X-ray diffraction, Thermogravimetric analysis, Differential Thermal gravimetry, and field emission scanning electron microscopy methods. The GNS/EPR1-5 nanocomposites were decorated with a layer of gold nanoparticles (Au NPs/GNS/EPR) to create surface-enhanced Raman scattering hot points. The wettability of the Au NPs/GNS/EPR was investigated in comparison with the different nanocomposites and the bare epoxy. Au NPs/GNS/EPR was used as a SERS-active surface for detecting different concentrations of dopamine with a limit of detection of 3.3 µM. Our sensor showed the capability to detect low concentrations of dopamine either in a buffer system or in human serum as a real sample.

Thermomechanical and Morphological Properties of Poly(ethylene terephthalate)/Anhydrous Calcium Terephthalate Nanocomposites

Calcium terephthalate anhydrous salts (CATAS), synthetized by reaction of terephthalic acid with metal (Ca) oxide were incorporated at different weight contents (0–30 wt. %) in recycled Poly(ethylene terephthalate) (rPET) by melt processing. Their structure, morphology, thermal and mechanical properties (tensile and flexural behavior) were investigated. Results of tensile strength of the different formulations showed that when the CATAS content increased from 0.1 to 0.4 wt. %, tangible changes were observed (variation of tensile strength from 65.5 to 69.4 MPa, increasing value for E from 2887 up to 3131 MPa, respectively for neat rPET and rPET_0.4CATAS). A threshold weight amount (0.4 wt. %) of CATAS was also found, by formation at low loading, of a rigid amorphous fraction at the rPET/CATAS interface, due to the aromatic interactions (π−π conjugation) between the matrix and the filler. Above the threshold, a restriction of rPET/CATAS molecular chains mobility was detected, due to the formation of hybrid mechanical percolation networks. Additionally, enhanced thermal stability of CATAS filled rPET was registered at high content (T_max shift from 426 to 441 °C, respectively, for rPET and rPET_30CATAS), essentially due to chemical compatibility between terephthalate salts and polymer molecules, rich in stable aromatic rings. The singularity of a cold crystallization event, identified at the same loading level, confirmed the presence of an equilibrium state between nucleation and blocking effect of amorphous phase, basically related to the characteristic common terephthalate structure of synthetized Ca–Metal Organic Framework and the rPET matrix.

Regeneration and Recovery of Plastics

Plastics are the most essential commodities in the world and are replacing the metals, wood, glass, cements and other materials in some application areas. Plastics are easy handling, resource-saving, non-toxic with esthetically attractive. Oil and gas are the major feedstocks for plastics, besides sugar and corn as renewable feedstocks. Plastics represent a serious waste-handling problem, with only 10%–12% of the plastic waste generated worldwide being regenerated/recycled. After disposal, plastic waste takes very long time to decompose naturally and impact the environment during the degradation process. The above situation has necessitated the invention of efficient technologies for regeneration and recovery of plastics all over the world.

Use of recycled polypropylene/poly(ethylene terephthalate) blends to manufacture water pipes: An industrial scale study

Poly(ethylene terephthalate) (PET) and polypropylene (PP) are two major polymeric materials that constitute many single-use plastic products. A common strategy to reduce polymeric waste is via mechanical recycling, a low cost and efficient process. However, from an industrial point of view, the reliability of this process is more easily achieved by a downgrade in the final properties of these materials, which limits the usage of recycled-based materials to less demanding applications. Furthermore, due to the intrinsic heterogeneity of the PP or PET waste, the use of these materials in industrial processing, tuned and developed for virgin neat materials, poses serious integrity problems. This aspect is particularly relevant in the case of plastics originating from the food packaging industry. This work explores the possibility of incorporating either PP or PET originated from plastic solid waste (PSW), in pipe manufacturing, with competitive mechanical properties compared to those prepared from virgin materials. To achieve this industrial solution, a process was developed using PP/PET 70/30 wt% formulations and the impact of replacing the virgin material by the different PSW in the microstructure, thermal and mechanical properties of the final material was analyzed. The impact of using a compatibilizer able to counteract the natural immiscibility between the PP and PET domains was also assessed. The developed formulation with recycled PET is a good example of the applicability of work developed at a laboratory scale into industrial-scale production.

Nanotechnology-Based Strategy to Upgrade the Performances of Plastic Flexible Film Waste

The aim of this work was to improve the performances of Fil-s (film-small), a recycled material obtained from plastic flexible film waste that is made of polyethylene and a minor amount of polypropylene, with traces of polar contaminants (polyamides, maleic anhydride, etc.). The idea was to upgrade the material’s mechanical properties by applying a nanotechnology-based strategy that takes advantage of the composition of Fil-s. In particular, different amounts of copolyamide (CoPA) and its masterbatch with an organic-modified nanosilicate were melt compounded with Fil-s in a twin-screw extruder. The good affinity between Fil-s and CoPA, proved by means of spectroscopic and rheological analysis, allowed for the obtaining of a well-refined morphology for the neat and hybrid blends. This resulted in very interesting increments of the strain at break, which was particularly impressive (10 times higher) in the case of the blend with the lower amount of copolyamide masterbatch, but without sacrificing the stiffness and strength of Fil-s.

Development of Flame-Retarded Nanocomposites from Recycled PET Bottles for the Electronics Industry

Recycled polyethylene-terephthalate (rPET) nanocomposites of reduced flammability were prepared by combining aluminum-alkylphosphinate (AlPi) flame retardant (FR) and natural montmorillonite (MMT), in order to demonstrate that durable, technical products can be produced from recycled materials. During the development of the material, by varying the FR content, the ratio and the type of MMTs, rheological, morphological, mechanical and flammability properties of the nanocomposites were comprehensively investigated. Related to the differences between the dispersion and nucleation effect of MMT and organo-modified MMT (oMMT) in rPET matrix, analyzed by Scanning Electron Microscopy (SEM), Energy Dispersive X-Ray Spectroscopy (EDS) and Differential Scanning Calorimetry (DSC), mechanical properties of the nanocomposites changed differently. The flexural strength and modulus were increased more significantly by adding untreated MMT than by the oMMT, however the impact strength was decreased by both types of nanofillers. The use of different type of MMTs resulted in contradictory flammability test result; time-to-ignition (TTI) during cone calorimeter tests decreased when oMMT was added to the rPET, however MMT addition resulted in an increase of the TTI also when combined with 4% FR. The limiting oxygen index (LOI) of the oMMT containing composites decreased independently from the FR content, however, the MMT increased it noticeably. V0 classification according to the UL-94 standard was achieved with as low as 4% FR and 1% MMT content. The applicability of the upgraded recycled material was proved by a pilot experiment, where large-scale electronic parts were produced by injection molding and characterized with respect to the commercially available counterparts.

Fabrication of EPYR/GNP/MWCNT carbon-based composite materials for promoted epoxy coating performance

The present study is aimed to fabricate composite materials containing epoxy resin (EPYR) reinforced by mixed carbon-based nano-fillers in the form of graphene nano-platelet (GNP) and multi-walled carbon nanotube (MWCNT) using the dissolution casting technique with the help of ultrasonic assistance. The pure epoxy resin was reinforced by variable loading of mixed GNP/MWCNT in situ, and the epoxy resin is denoted as EPYR/GNP/MWCNT_2–30. The numbers 2–30 corresponded to the final mass ratio of the nano-fillers. The designed products were reinforced by variable percentages of GNP/MWCNTs. XRD, FT-IR, thermal analyses, FE-SEM, TEM and electrical conductivity were utilized as identification techniques to confirm the structures of these composite materials. An excellent evidence for the composite formation was given by XRD diffraction patterns and FT-IR spectroscopy. The introduced amounts of mixed nano-fillers showed significant effects on the thermal, conducting and coating behaviors of pure EPYR. Pure EPYR and EPYR/GNP/MWCNT_20,30 showed higher thermal stabilities than other materials in the range of 400–410 °C. EPYR/GNP/MWCNT₂₀ also showed remarkable increase in the thermal stability compared to other materials. T₁₀ represents the temperatures at which 10% weight losses are examined. Pure EPYR and its related EPYR/GNP/MWCNT_2–30 displayed similar thermal stabilities at T₁₀ temperature (330 ± 4 °C). The morphological features were examined by SEM and TEM; these features showed that the nanocomposite components were extremely compatible. The in situ electrical conductivity values showed noticeable enhancement for the formulations of EPYR/GNP/MWCNT_2–10. Moreover, the coating performance of EPYR was tested by water uptake experiments and electrochemical impedance; both tests proved that the mixed GNP/MWCNT nano-fillers remarkably improved the pure EPYR coating due to the ionic charge transfer resistance and elevated barrier behaviour. The coating resistance variations values (CRv) of EPYR/GNP/MWCNT₁₀ were the highest among the measured composition values, closely followed by those of EPYR/GNP/MWCNT₂₀ and EPYR/GNP/MWCNT₃₀.

Composite materials containing epoxy resin and reinforced by mixed carbon-based nano-fillers (GNP/MWCNT) have been fabricated using the dissolution casting technique with the help of ultrasonic assistance for promoted epoxy coating performance.

Time Dependence of Morphology and Mechanical Properties of Injection Molded Recycled PET

During research, injection molded samples were prepared from recycled poly(ethylene-terephthalate) granulate, and their mechanical properties were investigated as a function of time. To understand the changes in mechanical properties, both morphology of injection molded samples and recycled granulates were investigated. A three-phase morphological model was applied for the evaluation of morphological properties while mechanical properties were determined by tensile and impact tests. Relationship was found between morphological and mechanical characteristics as a function of time elapsed since production. Crystalline ratio, tensile strength, and modulus of injection molded specimens increased while impact strength decreased in the four weeks after production.

Manipulating selective dispersion of reduced graphene oxide in polycarbonate/nylon 66 based blend nanocomposites for improved thermo-mechanical properties

Selective dispersion of rGO in PC/nylon blend by varying mixing sequence of rGO during melt mixing.

Preparation and Characterization of Octenyl Succinic Anhydride Modified Taro Starch Nanoparticles

The polar surface and hydrophilicity of starch nanoparticles (SNPs) result in their poor dispersibility in nonpolar solvent and poor compatibility with hydrophobic polymers, which limited the application in hydrophobic system. To improve their hydrophobicity, SNPs prepared through self-assembly of short chain amylose debranched from cooked taro starch, were modified by octenyl succinic anhydride (OSA). Size via dynamic light scattering of OSA-SNPs increased compared with SNPs. Fourier transform infrared spectroscopy data indicated the OSA-SNPs had a new absorption peak at 1727 cm^-1, which was the characteristic peak of carbonyl, indicating the formation of the ester bond. The dispersibility of the modified SNPs in the mixture of water with nonpolar solvent increased with increasing of degree of substitution (DS). OSA-SNPs appear to be a potential agent to stabilize the oil-water systems.

Polymer/metal nanocomposites for biomedical applications

Polymer/metal nanocomposites consisting of polymer as matrix and metal nanoparticles as nanofiller commonly show several attractive advantages such as electrical, mechanical and optical characteristics. Accordingly, many scientific and industrial communities have focused on polymer/metal nanocomposites in order to develop some new products or substitute the available materials. In the current paper, characteristics and applications of polymer/metal nanocomposites for biomedical applications are extensively explained in several categories including strong and stable materials, conductive devices, sensors and biomedical products. Moreover, some perspective utilizations are suggested for future studies.

Modeling the strength and thickness of the interphase in polymer nanocomposite reinforced with spherical nanoparticles by a coupling methodology

In this work, the strength (σi) and thickness (t) of interphase in polymer nanocomposites reinforced with spherical nanoparticles are modeled by the developed form of Leidner-Woodhams and Pukanszky models for tensile strength. The "σi" and "t" are expressed as functions of "B" parameter in Pukanszky model and the properties of matrix and nanofiller such as the strength of matrix and the nanoparticles radius and volume fraction. Additionally, the effects of the mentioned parameters on "σi" and "t" are discussed. The calculations show that "B" has dissimilar effects on "σi" and "t" levels. A high level of "B" in Pukanszky model suggests a high level of "σi", while a thin interphase is obtained in this condition. Also, the content of nanoparticles plays different roles in the levels of "σi" and "t" based on the extent of interfacial adhesion between polymer and nanoparticles (B value). The influences of "B" on "t" at different nanofiller contents are described by the possibility of nanoparticles aggregation at various values of "B".

Assumption of interphase properties in classical Christensen–Lo model for Young's modulus of polymer nanocomposites reinforced with spherical nanoparticles

The significant reinforcement of polymer nanocomposites containing spherical nanoparticles which exceeds the predictions of classical models is commonly attributed to the formation of an interphase between polymer and nanoparticles.

Recyclability assessment of nano-reinforced plastic packaging

Packaging is expected to become the leading application for nano-composites by 2020 due to the great advantages on mechanical and active properties achieved with these substances. As novel materials, and although there are some current applications in the market, there is still unknown areas under development. One key issue to be addressed is to know more about the implications of the nano-composite packaging materials once they become waste. The present study evaluates the extrusion process of four nanomaterials (Layered silicate modified nanoclay (Nanoclay1), Calcium Carbonate (CaCO3), Silver (Ag) and Zinc Oxide (ZnO) as part of different virgin polymer matrices of polyethylene (PE), Polypropylene (PP) and Polyethyleneterephtalate (PET). Thus, the following film plastic materials: (PE-Nanoclay1, PE-CaCO3, PP-Ag, PET-ZnO, PET-Ag, PET-Nanoclay1) have been processed considering different recycling scenarios. Results on recyclability show that for PE and PP, in general terms and except for some minor variations in yellowness index, tensile modulus, tensile strength and tear strength (PE with Nanoclay1, PP with Ag), the introduction of nanomaterial in the recycling streams for plastic films does not affect the final recycled plastic material in terms of mechanical properties and material quality compared to conventional recycled plastic. Regarding PET, results show that the increasing addition of nanomaterial into the recycled PET matrix (especially PET-Ag) could influence important properties of the recycled material, due to a slight degradation of the polymer, such as increasing pinholes, degradation fumes and elongation at break. Moreover, it should be noted that colour deviations were visible in most of the samples (PE, PP and PET) in levels higher than 0.3 units (limit perceivable by the human eye). The acceptance of these changes in the properties of recycled PE, PP and PET will depend on the specific applications considered (e.g. packaging applications are more strict in material quality that urban furniture or construction products).