Kaolinite-Starch based Nano-Composites and Applications

Lightweight polymer nanocomposites with excellent processability and chemical resistance have been becoming research focus of electromagnetic interference (EMI) shielding materials. The EMI shielding performance of polymer nanocomposites greatly depends on electrical conductivity, which is in turn determined by the transport efficiency through the conducting network. However, it still remains a great challenge to construct high-quality conducting pathway in polymer matrices with least filler content by matrix-filler interface and rational structural design. Research on the key scientific issues of polymer nanocomposites was conducted, and some interesting results were achieved, including: (1) Several approaches for the design and tailoring of filler dispersion and matrix-filler interfaces were developed and a series of high-performance electrically conductive polymer nanocomposites with low percolation threshold were successfully prepared; (2) Some routes for constructing preformed three-dimensional architectures for conductance/shielding were proposed, facilitating the structural and functional integration design of polymer nanocomposites; (3) The construction of multi-interface structures in polymer nanocomposite enables the balance of high EMI shielding performance and lightweight feature. This perspective summarizes our recent research advances, and forecasts the future challenges and opportunities of polymer nanocomposites for electromagnetic shielding.

The interest in producing renewable polymers from natural resources is considerably increased as the need for the reduction of the amount of plastic waste in the environment becomes urgent. Biopolymers are considered as an alternative raw material for the development of biodegradable packaging to plastic produced from petroleum. Starch, a renewable biopolymer consisting of amylose and amylopectin, is the most commonly used agricultural raw material for edible film manufacturing because it has low cost, easy to handle and totally biodegradable. In order to maintain the quality of foods, it is necessary to select the correct materials and appropriate technologies for the production of the packaging. Current trends include the development of packaging that interacts with food, called active biofilms or active packaging. Nanocomposites with antimicrobial function are highly useful for the minimization of the growth of contaminant microorganisms during the processing or storage of food and thereby the extension of shelf-life and improvement of food safety. Thus, this work aims to review the literature to identify the main components used in packaging with nanoparticles and the results in food preservation. For this purpose, a bibliographic survey of the last 5 years was carried out in the databases of Scielo, Science direct, Google academic and Periodicals CAPES, with the following indexers: nanocomposites, nanotechnology, active packaging, and antimicrobial packaging. Some studies demonstrated that metal oxide nanocomposites in packaging provide enhances polymer barrier properties, making the material stronger, more flame resistant, with better thermal properties and having favorable surface wettability and hydrophobicity. Studies have shown that silver nanoparticles have antimicrobial activity against Gram-negative and Gram-positive bacteria and fungi. Also, chitosan nanostructures, a natural composite, have wide antimicrobial effects. Some studies have focused on antimicrobial effects of nanostructures combining chitosan and other antimicrobial agents as carvacrol, oregano and thyme essential oil. It was observed that chitosan nanocomposites combined with layered silicate were significantly more effective against Staphylococcus aureus and Escherichia coli than both pure. Packaging that increases the shelf-life of perishable food while reducing food waste is a sustainable opportunity for innovative technology.

The addition of 0.2–5% nanoscale (40–80 nm) α-phase or microscale (40 μm) γ-phase Al2O3 particles in PTFE effectively reduce the matrix wear rate by 99.99%, whereas microscale (> 0.5 μm) α-Al2O3 or nanoscale (40–80 nm) γ-Al2O3 only reduce PTFE wear by ~ 90% under identical loading, dispersion and testing conditions. This paradoxical material system best illustrates the complexity of tribology and the importance of filler–matrix interactions at small scales. We studied the independent effect of the Al2O3/PTFE interface area and alumina structure by systematically varying the particle size over two orders of magnitude for both α- and γ-Al2O3/PTFE composites. Detailed characterizations of filler size, surface area and tribofilm’s chemical composition were conducted. The results found: (1) DLS median particle sizes conformed reasonably to vendor reported values and percentages of microscale filler aggregates correlated weakly with wear rates, (2) electron microscopy of the as-worn composite surface suggested a strong relation between the characteristic size of ‘unreinforced’ polymer domain and composite wear rate, (3) third bodies (i.e., transfer films, debris) played an important role in counterface abrasion, (4) wear rate correlated strongly with filler’s specific surface area and ultralow wear was only maintained ~ 0.3–10 m2/g nominal specific filler–matrix area values, (5) ultralow wear coincided with perfluorinated carboxylic salt rich tribofilms which supported a previously proposed wear reduction mechanism that mechanochemically degraded PTFE chelate with alumina and cause crosslinked and wear-resistant tribofilms, (6) tribofilm Al-F bond signal increased with filler surface area and high wear coincided with excessive tribofilm Al-F signal for γ-Al2O3/PTFE systems. Based on these results and literature hypothesis, we proposed that (1) the 1 μm α-Al2O3 provided the least filler–matrix interface and largest unreinforced polymer domain in PTFE, which lead to the least crosslinked and compartmentalized tribofilms; (2) in γ-alumina filled composites, Al-F bond forms as a product of mechanochemically degraded PTFE but also blocks chelation between the degraded PTFE and alumina fillers, (3) the 20 nm γ-Al2O3 provided the most filler–matrix interface which leads to excessive aluminum fluoride that blocked the filler–matrix chelation, prevented the tribofilm crosslinking and lead to high wear rates. This hypothesis was additionally supported by small molecule experiments in this study. However, this study provides no direct insight into how sensitive the filler–matrix tribochemical interaction is to filler phase or aggregate strength (strong, weak or fully dense).

We have used amido-amine functionalized carbon nanotubes (CNTs) that form covalent bonds with cross-linked epoxy matrices to elucidate the role of the matrix-filler interphase in the enhancement of mechanical and thermal properties in these nanocomposites. For the base case of nanocomposites of cross-linked epoxy and pristine single-walled CNTs, our previous work (Khare, K. S.; Khare, R. J. Phys. Chem. B 2013, 117, 7444-7454) has shown that weak matrix-filler interactions cause the interphase region in the nanocomposite to be more compressible. Furthermore, because of the weak matrix-filler interactions, the nanocomposite containing dispersed pristine CNTs has a glass transition temperature (Tg) that is ∼66 K lower than the neat polymer. In this work, we demonstrate that in spite of the presence of stiff CNTs in the nanocomposite, the Young's modulus of the nanocomposite containing dispersed pristine CNTs is virtually unchanged compared to the neat cross-linked epoxy. This observation suggests that the compressibility of the matrix-filler interphase interferes with the ability of the CNTs to reinforce the matrix. Furthermore, when the compressibility of the interphase is reduced by the use of amido-amine functionalized CNTs, the mechanical reinforcement due to the filler is more effective, resulting in a ∼50% increase in the Young's modulus compared to the neat cross-linked epoxy. Correspondingly, the functionalization of the CNTs also led to a recovery in the Tg making it effectively the same as the neat polymer and also resulted in a ∼12% increase in the thermal conductivity of the nanocomposite containing functionalized CNTs compared to that containing pristine CNTs. These results demonstrate that the functionalization of the CNTs facilitates the transfer of both mechanical load and thermal energy across the matrix-filler interface.

The development of nano-composite materials is making a significant impact on modern technology due to their wide range of applications and their superior properties1. Several methods have been proposed and developed to prepare polymer nano-composites. Graphene nano-composites, in particular, have attracted the interest of researchers because of their excellent properties, such as high electrical conductivity, high thermal stability and excellent mechanical strength 2–3. Graphene, a two-dimensional carbon atoms structure, exhibits exceptional properties4–5. Incorporating these nano-fillers with high performance polymers results in a unique combinations of properties.This paper reports on the synthesis and characterization of graphene and LLDPE (Linear Low Density Polyethylene)/graphene nano-composites with different weight ratios of graphene. Graphene was synthesized from graphene oxide, which was prepared by using modified hammers method. The obtained few layers of graphene were confirmed by different characterization methods such as FTIR, XRD, Raman spectroscopy and SEM. LLDPE/Graphene composites at different weight ratios of graphene, i.e. 1, 4, and 8 wt% were compounded in twin screw extruder. Extruded granules of LLDPE/Graphene materials were used in the preparation of nano-composites by compression molding. In this research, we used the LLDPE as the polymer matrix, because PE (polyethylene) is one of the most common plastic resins in the world and it is produced on a large scale in the State of Qatar by Qatar Petrochemical Company (QAPCO). LLDPE has grown most rapidly within the PE family due to its good balance of mechanical properties and process-ability compared to other types of PE. The effect of graphene ratio on the mechanical, thermal and electrical properties were investigated. LLDPE/Graphene composites with 4% graphene showed higher tensile strength and tensile modulus than the other graphene loading composites. Agglomeration was a problem in the composites with high wt% of the graphene which caused the reduction in tensile properties. Graphene marginally increased the melting temperature of the nano-composites whereas crystallization temperature, thermal stability and electrical conductivity were increased with increase of graphene loading. The results obtained showed that the graphene can increase the thermal stability of the polymer mixture. Increment of thermal stability is due to the high thermal stability of the graphene and the formation of phonon and charge carrier networks in the matrix. The electrical conductivity of LLDPE is 4.28 × 10− 11 and for nano composites is 9.2 × 10− 05. The high electrical conductivity of the graphene converts the LLDPE polymer insulator to an electrical conductor. Electrically conductive PE based composite materials can be used as electron magnetic-reflective materials, as well as in high voltage cables. The enhancement in mechanical, thermal and electrical properties of LLDPE/Graphene nano-composites achieved by melt mixing of graphene into the polymer can enable mass production of new and low cost novel materials with superior tensile strength, thermal stability and electrical conductivity.

Environmental pollution is a serious issue nowadays due to urbanization and overpopulation. Pollutants such as heavy metals, fertilizers, pesticides, herbicides, industrial effluents and organic compounds are the major source of environmental pollution. Combination of these diverse compounds and its degradation in natural environment is very tough. To overcome this problem, nanotechnology plays a significant role in the environmental remediation. The application and performance of various nanomaterials in ecological remediation depends mainly on methodologies preferred for the elimination of target pollutants from wastewater. The superior properties like high surface area and efficiency of nanomaterials are key reason for the elimination of pollutants from contaminated water. Adsorption, absorption, chemical reaction, filtration and photocatalysis-mediated nanotechnology degrades highly contaminated sites effectively. The environmental remediation could be explored by several engineered nanomaterials such as carbon, graphene, chitosan, polymer supported, metal oxide, membranes, dendrimers and fibrous clay-based nanocomposites. Nanoremediation helps to diminish cost of overall cleaning up of large-scale contaminated sites compared to conventional method of remediation. Nano-based remediation reduces degradation time and has the potential of 100% pollutant remediation capacity. This chapter affords the knowledge on environmental pollutant remediation using nanomaterials.KeywordsNanomaterialsEnvironmental pollutantsNanoremediationPhotocatalysisLarge-scale remediation

Preparation of poly(vinyl alcohol)-grafted graphene oxide/poly(vinyl alcohol) nanocomposites via in-situ low-temperature emulsion polymerization and their thermal and mechanical characterization

The thermal and mechanical properties of cassava starch films are analyzed in relation to the starch–kaolinite interactions. The kaolinite filler induces a lowering of the crystallinity in accordance with an increase plasticization of the starch matrix. The increase of plasticization induces a decrease of the elastic modulus and an increase of the elongation at break. A retardant effect to the starch matrix decomposition is observed. The filler–matrix interface at which the plasticizer infiltration is enhanced and the reduction of starch chain–chain interactions appears as keys of the observed properties changes. POLYM. COMPOS., 36:184–191, 2015. © 2014 Society of Plastics Engineers

This study investigates the multifunctional potential of ZnO/CuO/Clay heterojunction nanocomposites (NCs) synthesized via the solution combustion method. Six NCs were prepared by varying ZnO/CuO ratios within two clay molar fractions (0.25 and 0.5 mol). Structural and compositional analyses (field emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray spectroscopy (EDS), inductively coupled plasma optical emission spectroscopy (ICP-OES), dynamic light scattering (DLS), and Brunauer-Emmett-Teller (BET)) confirmed successful heterojunction formation, uniform elemental distribution, stable colloidal behavior, and a mesoporous nanostructure. Ultraviolet-visible diffuse reflectance spectroscopy (UV-vis DRS) revealed enhanced visible-light absorption with increasing CuO and decreasing clay content, thereby improving the NC's optical characteristics and resulting in enhanced photocatalytic performance. Band gap measurements revealed CuO's band gap narrowing effect, while ZnO and clay increased it. Antibacterial assays against Escherichia coli and Staphylococcus aureus showed significantly enhanced activity, with lower MIC values observed for NCs containing 0.25 mol clay. This behavior can be attributed to the smaller particle size, improved nanoparticle (NP) dispersion, reduced aggregation, increased porosity, and greater active surface area of these NCs compared to those with 0.5 mol clay. Transmission electron microscopy (TEM) imaging confirmed membrane disruption as a key antibacterial mechanism, supported by reactive oxygen species (ROS) generation, ion release, and synergistic interaction with clay nanosheets. Cytotoxicity tests on cancerous HT-29 cells demonstrated dose- and time-dependent behavior for the 0.75CuO/0.25Clay NC and dose-dependent behavior for the 0.75ZnO/0.25Clay NC, both with minimal toxicity to normal HFF cells. Antioxidant evaluation showed significant 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity (57%), comparable to ascorbic acid (60.2%). Overall, these results highlight solution combustion-synthesized ZnO/CuO/Clay NCs as promising bioactive materials for photocatalytic, antibacterial, anticancer, and antioxidant applications in medicine, food packaging, and environmental remediation.

This Research on polymeric materials was widely focused on the development of polymer nano composites with various nano fillers during the last decades. In this context, the present lecture gives an overview on recent developments on halloy site nano tubes reinforced nano composites, including the processing, characterization and potential applications in industry. The naturally derived nano tubular halloysites represent a distinctive class of nanofiller for industrially significant polymers. Usage of such natural nanotubes not only enhances the material properties but also improves the sustainability and environmental impact of the manufactured products. Additionally, HNTs are biocompatible, and find various applications in biomedical field. In the present work, environmentally friendly HNTs were introduced into various thermoplastics such as polypropylene, polyamide-66, bio based polyamide 11 and thermoplastic starch matrices to generate novel nano composite materials through an advantageous melt-processing method. The effects of HNTs content on the structural, optical, thermal, mechanical, viscoelastic and dielectic properties were investigated. The incorporation of HNTs generates notable performance enhancements through reinforcement effects, highly efficient nucleation activity. In particular, compared to other nano fillers such as nano clays and carbon nanotubes, excellent mechanical properties have been observed (and especially a unique combination of strength, rigidity and ductility). A focus will also be made on the tuning of structural and mechanical properties of the thermoplastic starch through residence time, addition of different combinations of plasticizers and HNTs content. Finally, strategy of preparing conducting composite via the addition of polyaniline functionalized halloy site nano tubes into polymer matrix are presented in order to enhance the application of halloy site nano tubes. Such HNTs filled nano composites can provide an effective balance between performance, cost effectiveness and easy processing, and should be of great interest in the area of multifunctional polymer nano composite materials. Polymer nanocomposites are new class of materials that are filled with nanofillers, and which usually exhibit exceptionally superior thermomechanical performance and physical properties at very lower filler loadings compared to conventional polymer composites [1]. Improvements in mechanical properties, such as stiffness and toughness, electrical, dimensional stability, barrier and thermal properties as well as fire retardant enhancements, with respect to the bulk polymer, are usually observed. The interfacial interactions and degree of dispersion state of fillers in polymer matrix is important in determining the final performance of polymer nanocomposites [2]. manuscripts Halloysite nanotubes have recently become the subject of research attention as a new type of additive for enhancing the mechanical, thermal and fire-retardant performance of polymers [3] Halloysite is mainly composed of aluminosilicate and has a predominantly hollow tubular structure with the chemical composition Al2(OH)4Si2O5(2H2O). It is a weathering product of volcanic rocks of rhyolitic up to granitic composition and occurs in great deposits. Common halloysites can be found in form of fine, tubular structures with a length of 300~1500 nm in length and inner diameter and outer diameters being 15-100 nm and 40-120 nm, respectively. Even if the usage of a silica based, natural occurring nanotube as reinforcing material for polymers is still new, HNTs are considered as the ideal materials for preparing polymer

Stepwise reinforcement strategy for guar gum/sodium alginate based films: Introduction of carboxylated cellulose nanofibers by different methods and further calcium ion crosslinking

Dispersion in the melt is a very serious issue that affects properties of composites based on cellulosic fillers as these materials tend to form agglomerates. The aim of this study is to test the efficiency of various methods to improve the dispersion of cellulosic fillers in PBAT polymer. First, periodate oxidation treatment was carried out on the fillers in an attempt to reduce the amount of hydroxyl groups responsible of the agglomeration of cellulosic fillers in composite materials. Secondly, as several studies have demonstrated the positive effect of using tert-butanol (TB) as a freeze-drying medium for preventing the aggregation of cellulosic particles, this method was tested to produce composites with reduced amount of agglomerates. Finally, the addition of a third component as a compatibilizer which has a similar chemical structure to cellulose such as starch was also tested. No significant improvement of mechanical properties was noticed in using TB as a freeze-drying medium or with periodate oxidation treatment on the cellulosic fillers at least in improving dispersion in PBAT composites. However, the addition of starch as a compatibilizer has proved its effectiveness through the creation of a percolating network and a better dispersion of the fillers in the polymer matrix.

This chapter introduces some of the major environmental issues. It discusses the relevance and implications of these issues to selected industrial sectors. Many people have heard of the major environmental issues, such as the greenhouse effect, the ozone hole, and deforestation. Noise is the most ubiquitous of environmental pollutants. Waste production continues to grow in most countries, and is one of the major environmental impacts of the modern consumer-oriented society. Natural systems act as environmental 'buffers', but their capacity to ameliorate environmental pressures is often reduced by human disturbance. Industrialisation, urbanisation, and the extension of agriculture have all caused increased environmental pressures. Pressure on industries is increasing as public awareness rises and legislation and policies on environmental subjects tightens. The production of electricity is a major source of pollution and environmental damage. Power stations are a major source of atmospheric pollutants and the construction of stations consumes land and massive quantities of building materials.

Pollution in waterbodies is a major issue, and researchers work to assess sources of pollution in order to mitigate its impact on the environment. A major source of pollution is from animal fecal matter and sewage effluents, contributing to water quality issues worldwide. Tracking the source of the fecal pollution is necessary, providing the foundation on which to build an effective solution. In this study, we propose to track the fecal pollution sources by the sterol composition and explore the cluster structure of fecal pollution sources according to their sterol signatures. The sterol composition of various animal fecal and effluents were sourced from different peer reviewed journals (n = 10). Various clustering methods including hierarchical clustering analysis are performed on the data to explore the similarity of different fecal pollutions and clusters based on the sterol composition. The results from the analysis reveal that human, dingo, and rosella fecal have the highest proportion of coprostanol, cholesterol and campesterol respectively. Rosella, wastewater effluents, humans, and pigs are shown to have a definite cluster. Overall, our results show that clusters produced by hierarchical clustering can be used in tracking source of fecal pollution and should be adopted in assessing source of fecal pollution.

Fil: Merino, Danila. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnologico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnologia de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingenieria. Instituto de Investigaciones en Ciencia y Tecnologia de Materiales; Argentina