Starch nano-biocomposites based on needle-like sepiolite clays

A Review of the Effect of Plasticizers on the Physical and Mechanical Properties of Alginate-Based Films

In recent years, there has been a growing attempt to manipulate various properties of biodegradable materials to use them as alternatives to their synthetic plastic counterparts. Alginate is a polysaccharide extracted from seaweed or soil bacteria that is considered one of the most promising materials for numerous applications. However, alginate potential for various applications is relatively limited due to brittleness, poor mechanical properties, scaling-up difficulties, and high water vapor permeability (WVP). Choosing an appropriate plasticizer can alleviate the situation by providing higher flexibility, workability, processability, and in some cases, higher hydrophobicity. This review paper discusses the main results and developments regarding the effects of various plasticizers on the properties of alginate-based films during the last decades. The plasticizers used for plasticizing alginate were classified into different categories, and their behavior under different concentrations and conditions was studied. Moreover, the drawback effects of plasticizers on the mechanical properties and WVP of the films are discussed. Finally, the role of plasticizers in the improved processing of alginate and the lack of knowledge on some aspects of plasticized alginate films is clarified, and accordingly, some recommendations for more classical studies of the plasticized alginate films in the future are offered.

Structure of Starch-Sepiolite Bio-Nanocomposites: Effect of Processing and Matrix-Filler Interactions

Sepiolite clay is a natural filler particularly suitable to be used with polysaccharide matrices (e.g., in starch-based bio-nanocomposites), increasing their attractiveness for a wide range of applications, such as packaging. Herein, the effect of the processing (i.e., starch gelatinization, addition of glycerol as plasticizer, casting to obtain films) and of the sepiolite filler amount on the microstructure of starch-based nanocomposites was investigated by SS-NMR (solid-state nuclear magnetic resonance), XRD (X-ray diffraction) and FTIR (Fourier-transform infrared) spectroscopy. Morphology, transparency and thermal stability were then assessed by SEM (scanning electron microscope), TGA (thermogravimetric analysis) and UV-visible spectroscopy. It was demonstrated that the processing method allowed to disrupt the rigid lattice structure of semicrystalline starch and thus obtain amorphous flexible films, with high transparency and good thermal resistance. Moreover, the microstructure of the bio-nanocomposites was found to intrinsically depend on complex interactions among sepiolite, glycerol and starch chains, which are also supposed to affect the final properties of the starch-sepiolite composite materials.

Study of the water sorption and barrier performances of potato starch nano-biocomposites based on halloysite nanotubes

The barrier performances, in terms of water vapor sorption properties, gas and water barrier performances were analyzed on different starch-based nano-biocomposites. These multiphase systems were elaborated by melt blending starch and halloysite nanotubes at different contents with different plasticizers (glycerol, sorbitol and a mix of both polyols). The influence of the composition was investigated onto the structure, morphology, water sorption and barrier performances. As recently reported, halloysite nanoclay is a promising clay to enhance the properties of plasticized starch matrix. The barrier performances of nanofilled starch-based films were examined through gas and water permeabilities, diffusivity and water affinity. Glycerol-plasticized starch films give fine and more homogeneous nanofiller dispersion with good interfacial interactions, compared to sorbitol ones (alone or mixed), due to stronger and more stable hydrogen bonds. Tortuosity effects linked to the halloysite nanotubes were evidenced by gas transfer analysis, and exacerbated by the good interactions at interfaces and the resulting good filler dispersion. The influence of morphology and interfacial interactions towards water affinity was highlighted by moisture barrier properties. This was a key factor on the reduction of water diffusion and uptake with nanoclay content. A preferential water transfer was observed as a function of a plasticizer type in relation with the phenomenon of water plasticization in the nanocomposite systems.

Effect of Sepiolite-Loaded Fe2O3 on Flame Retardancy of Waterborne Polyurethane

In this study, a kind of inorganic composite flame retardant (Sep@Fe2O3) was prepared by combining solution deposition and calcination methods using sepiolite microfiber material as carrier. This inorganic compound flame retardant was combined with waterborne polyurethane (WPU) through layer-by-layer method to prepare WPU composites. The SEM and EDS, TEM, and XRD were used to characterize the microscopic morphology and crystal structure of WPU composites. Thermogravimetric analysis tests confirmed the good thermal stability of WPU/Sep@Fe2O3 composites; at the temperature of 600°C, the carbon residual percentage of WPU/Sep, WPU/Fe2O3, and WPU/Sep@Fe2O3 composites is 7.3%, 12.2%, and 13.4%, respectively, higher than that of WPU (1.4%). Vertical combustion tests proved better flame-retardant property of WPU/Sep@Fe2O3 composite-coated cotton than noncoated cotton. The microcalorimeter test proved that the PHRR of WPU/Sep@Fe2O3 composites decreased by 61% compared with that of WPU. In addition, after combining with Sep@Fe2O3, the breaking strength of WPU increased by 35%.

Cooperative Effects of Cellulose Nanocrystals and Sepiolite When Combined on Ionic Liquid Plasticised Chitosan Materials

Cellulose nanocrystals (CNCs) and/or sepiolite (SPT) were thermomechanically mixed with un-plasticised chitosan and chitosan/carboxymethyl cellulose (CMC) blends plasticised with 1-ethyl-3-methylimidazolium acetate ([C₂mim][OAc]). Examination of the morphology of these materials indicates that SPT aggregates were reduced when CNCs or [C₂mim][OAc] were present. Inclusion of CNCs and/or SPT had a greater effect on material properties when the matrices were un-plasticised. Addition of SPT or CNCs altered the crystalline structure of the un-plasticised chitosan matrix. Moreover, a combination of SPT and CNCs was more effective at suppressing re-crystallisation. Nonetheless, the mechanical properties and surface hydrophobicity were more related to CNC/SPT-biopolymer interactions. The un-plasticised bionanocomposites generally showed increased relaxation temperatures, enhanced tensile strength, and reduced surface wettability. For the [C₂mim][OAc] plasticised matrices, the ionic liquid (IL) dominates the interactions with the biopolymers such that the effect of the nanofillers is diminished. However, for the [C₂mim][OAc] plasticised chitosan/CMC matrix, CNCs and SPT acted synergistically suppressing re-crystallisation but resulting in increased tensile strength.

The Quantitative Nanomechanical Mapping of Starch/Kaolin Film Surfaces by Peak Force AFM

Starch films modified with additives are materials increasingly being used in the production of packaging. These types of biopolymers can, to a considerable degree, replace plastic, contributing to the reduction in both production and waste management costs. However, they should be characterised by specific mechanical and surface parameters which determine their application. In the presented work, the PeakForce Quantitative Nanomechanics Mapping (PFQNM) method was applied to analyse a starch-based biopolymer modified with two different kaolin clay contents (5% and 10%). The technique used facilitates the assessment of the correlation of Atomic Force Microscope AFM height parameters with nanomechanical ones which provide the definitions of mutual interactions and allow the possibility to analyse materials in respect of various details. The investigated material was mapped in the Derjaguin-Muller-Toporov (DMT) modulus, adhesion and height domains. The results obtained indicated the impact of additives on the determined parameters. Increases in the DMT modulus and the adhesion force, along with the kaolin content, were observed. The enhancement of starch films with kaolin clay also induced growth in the surface roughness parameters.

Starch, cellulose, pectin, gum, alginate, chitin and chitosan derived (nano)materials for sustainable water treatment: A review

Natural biopolymers, polymeric organic molecules produced by living organisms and/or renewable resources, are considered greener, sustainable, and eco-friendly materials. Natural polysaccharides comprising cellulose, chitin/chitosan, starch, gum, alginate, and pectin are sustainable materials owing to their outstanding structural features, abundant availability, and nontoxicity, ease of modification, biocompatibility, and promissing potentials. Plentiful polysaccharides have been utilized for making assorted (nano)catalysts in recent years; fabrication of polysaccharides-supported metal/metal oxide (nano)materials is one of the effective strategies in nanotechnology. Water is one of the world's foremost environmental stress concerns. Nanomaterial-adorned polysaccharides-based entities have functioned as novel and more efficient (nano)catalysts or sorbents in eliminating an array of aqueous pollutants and contaminants, including ionic metals and organic/inorganic pollutants from wastewater. This review encompasses recent advancements, trends and challenges for natural biopolymers assembled from renewable resources for exploitation in the production of starch, cellulose, pectin, gum, alginate, chitin and chitosan-derived (nano)materials.

Characterization of surface properties of chitosan/bentonite composites beads by inverse gas chromatography

Chitosan/bentonite (CSBt) composites beads were prepared by dropwise of a solution containing chitosan and bentonite to an alkaline NaOH solution. Fourier Transform Infrared Spectroscopy, X-ray diffraction analysis, X-ray photoelectron spectroscopy, XPS and Brunauer-Emmett-Teller BET analysis have been used to provide new insights on the composition and morphology of CSBt composites beads surface. In this study, inverse gas chromatography (IGC) was implemented to characterize physico-chemical properties of CSBt composites surface. IGC at infinite dilution (IGC-ID) was used to understand the effect of CS on dispersive component of the surface energy of the bentonite. The increasing amount of CS leads to significantly decrease of Bt γ_s^d emphasizing the Bt coating with CS. The IGC at finite concentration (IGC-FC) was also implemented allowing us to reach several parameters such as: specific surface area with organic probes and the distribution functions of the adsorption energy sites on the solid surface. In this case, the most significant decreases were observed in the specific surface area obtained with the octane and isopropanol probes. The distribution function of the adsorption energy sites obtained with isopropanol revealed the decrease in the number of the high energy sites with increase of CS/Bt mass ratio.

Urea Formaldehyde Resin Resultant Plywood with Rapid Formaldehyde Release Modified by Tunnel-Structured Sepiolite

In order to reduce the cost of plywood and save edible resources (wheat flour), a cheap and resourceful clay, sepiolite, was used to modify urea formaldehyde (UF) resin. The performances of filler-filled UF resins were characterized by measuring the thermal behavior, cross section, and functional groups. Results showed that cured UF resin with SEP (sepiolite) formed a toughened fracture surface, and the wet shear strength of the resultant plywood was maximum improved by 31.4%. The tunnel structure of SEP was beneficial to the releasing of formaldehyde, as a result, the formaldehyde emission of the plywood bonded by UF resin with SEP declined by 43.7% compared to that without SEP. This study provided a new idea to reduce the formaldehyde emission, i.e., accelerating formaldehyde release before the product is put into use.

Hierarchical Structure and Thermal Property of Starch-Based Nanocomposites with Different Amylose/Amylopectin Ratio

Starch-based materials with reinforced properties were considered as one of the most promising materials to replace the petro-based packaging products, and actually, the molecular structures of starch usually determined the structures and properties of end-used starchy products. Here, starch-based nanocomposites were fabricated by starch esters derived from native starches with different amylose contents and organically modified montmorillonite (OMMT). The fractured surface under scanning electron microscopy (SEM) exhibited wrinkles formed by macromolecular aggregation owing to the interaction competition between the plasticizer and nanofiller with the starch ester. The more intense interaction within amylopectin-rich films promoted the formation of much randomly exfoliation of OMMT observed by Transmission electron microscopy (TEM). As the amylose content increased, the interaction between the starch ester and the nanofiller was weakened, leading to the dispersion morphology of an ordered arrangement and partly intercalated structures in the dimension of 12.92 to 19.77 nm. Meanwhile, such interaction also affected both the inner ordered structure integrity of starch ester and the layer structure consistency of nanofiller according to X-ray diffraction results. Further, the stronger interaction between amylopectin and the nanofiller endowed higher thermal stability to the amylopectin-rich starch-based nanocomposites. In short, these results are beneficial for the application of starch-based nanocomposites in the food packaging industry by regulating the interaction between starch and nanofillers.

Preparation and Characterization of Thermoplastic Potato Starch/Halloysite Nano-Biocomposites: Effect of Plasticizer Nature and Nanoclay Content

Nano-biocomposites based on halloysite nanoclay and potato starch were elaborated by melt blending with different polyol plasticizers such as glycerol, sorbitol or a mixture of both. The effects of the type of plasticizer and clay content on potato starch/halloysite nano-biocomposites were studied. SEM analyses combined with ATR-FTIR results showed that a high content of sorbitol had a negative effect on the dispersion of the halloysite nanoclay in the starchy matrix. XRD results demonstrated that incorporation of halloysite nanoclay into glycerol-plasticized starch systems clearly led to the formation of a new crystalline structure. The addition of halloysite nanoclay improved the thermal stability and decreased the moisture absorption of the nano-biocomposites, whatever the type of plasticizer used. Halloysite addition led to more pronounced improvement in mechanical properties for glycerol plasticized system compared to nanocomposites based on sorbitol and glycerol/sorbitol systems with a 47% increase in tensile strength for glycerol-plasticized starch compared to 10.5% and 11% for sorbitol and glycerol/sorbitol systems, respectively. The use of a mixture of polyols was found to be a promising way to optimize the mechanical properties of these starch-based nanocomposites.

Development of organic–inorganic hybrid beads from sepiolite and cellulose for effective adsorption of malachite green

A facile approach has been developed to fabricate well defined organic–inorganic hybrid beads from widely available bamboo pulp and sepiolite, in expectation of an alternative green adsorbent for the removal of organic dyes.

Nanoclays for Lipase Immobilization: Biocatalyst Characterization and Activity in Polyester Synthesis

The immobilization of Candida antarctica lipase B (CALB) was performed by physical adsorption on both neat and organo-modified forms of sepiolite and montmorillonite. The influence of different parameters, e.g., solvent, enzyme loading, cross-linking, and type of clay support, on immobilization efficiency and catalyst hydrolytic activity has been investigated. The highest hydrolytic activities were obtained for CALB immobilized on organo-modified clay minerals, highlighting the beneficial effect of organo-modification. The esterification activity of these CALB/organoclay catalysts was also tested in the ring-opening polymerization of ε-caprolactone. The polymerization kinetics observed for clay-immobilized catalysts confirmed that CALB adsorbed on organo-modified montmorillonite (CALB/MMTMOD) was the highest-performing catalytic system.

Functional Nanocomposites Based on Fibrous Clays

This chapter is focused on functional nanocomposites based on the use of the microfibrous clays sepiolite and palygorskite as efficient fillers for diverse types of polymer matrices, from typical thermoplastics to biopolymers. The main features that govern the interaction between the silicates and the polymer matrix are discussed. The introduction addresses the structural and textural features of the fibrous silicates, as well as the possible synthetic approaches to increase the compatibility of these nanofillers with the polymeric matrix. Additionally, these clays can be easily functionalized through their surface silanol groups based on chemical reactions or by anchoring of nanoparticles. This allows for the preparation of a wide variety of functional polymer–clay nanocomposites. Thereafter, some relevant examples of nanocomposites derived from conventional polymers are reported, as well as of those based on polymers that exhibit electrical conductivity. Lastly, selected works employing sepiolite or palygorskite as fillers in polymeric matrixes of natural origin are discussed, showing the wide application of these resulting nanocomposites as bioplastics, as well as in biomedicine, environmental remediation and the development of sensor devices.

Studies on Electrical, Thermal and Corrosion Behaviour of Cashew Tree Gum Grafted Poly(Acrylamide)

The present work aimed to study the thermal transitions, electrical properties and corrosion behaviour of cashew tree gum (CTG), poly (acrylamide) (PAM) and cashew tree gum grafted poly (acrylamide) (CTG-g-PAM) copolymer. Various amounts of acrylamide monomer were grafted onto cashew gum using a radical polymerization method. The formation of graft copolymer was analysed by FTIR, UV, SEM, DSC and electrical conductivity measurements. The FTIR and UV spectrum infers the occurrence of strong intermolecular interaction between cashew gum and poly (acrylamide). SEM photographs revealed that the acrylamide unit was well inserted into the cashew gum segments. The DSC analysis showed a significant decrease in glass transition temperature with an increase in amount of acrylamide chains. CTG shows higher AC conductivity than PAM and the conductivity of graft copolymer increases with the concentration of acrylamide up to certain concentration of monomer and thereafter the value decreases. The dielectric properties such as dielectric constant and dielectric loss tangent values of PAM was lower than CTG and the dielectric values also shows a similar trend as AC conductivity. CTG, PAM and its graft copolymer with various amount of poly (acrylamide) have been investigated as a corrosion inhibition for mild steel in hydrochloric acid. The inhibition efficiency increased with increase in concentration of PAM in the graft copolymer. PAM was found to have the high inhibition efficiency than CTG, due to the difference in their molecular structures. The corrosion rate of all the samples enhanced with the raise in temperature whereas the inhibition efficiency deceases.

Emerging trends in eco-compliant, synergistic, and hybrid assembling of multifunctional polymeric bionanocomposites

The quest to develop eco-benign polymeric hybrid materials arose out of the need to protect the environment from the harmful effects of synthetic petroleum polymeric waste and meet the specific needs of industries such as oil and gas, aerospace, automotives, packaging, electronics biomedicals, pharmaceuticals, agricultural, and construction. This has resulted in synergistic hybrid assembling of natural fibers, polymers, biopolymers, and nanoparticles. Bionanocomposites based on inorganic nanoparticle reinforced biofiber, polymers and biopolymers, and polysaccharides such as chitosan, alginate, and cellulose derivatives, and so on, exhibiting at least a dimension at the nanometer scale, are an emerging group of nanostructured hybrid materials. These hybrid bionanocomposites exhibit structural and multifunctional properties suitable for versatile applications similar to polymer nanocomposites. Their biocompatibility and biodegradability provide opportunities for applications as eco-benign green nanocomposites. This review presents state-of-the-art progress in synergistic nanotechnological assembling of bionanocomposites relative to processing technologies, product development, and applications.

Chlorinated polyethylene (CPE)/ethylene methacrylate copolymer (EMA)/sepiolite nanocomposite via a facile one-step covalent modification technique

Facile one-step organo-modification of sepiolite improves polymer–filler interfacial adhesion, thereby advances mechanical properties and thermal stability of the CPE/EMA/sepiolite nanocomposite.

Elaboration, morphology and properties of starch/polyester nano-biocomposites based on sepiolite clay

The incorporation of nano-sized sepiolite clays into thermoplastic starch/poly(butylene adipate-co-terephthalate) (TPS/PBAT) blends has been investigated with the goal of improving the matrix properties. TPS/PBAT nano-biocomposites were elaborated with two different proportions of the polymeric phases. The influence of the sepiolite nanoclays on the mechanical, thermal and structural properties of the corresponding blends was evaluated. SEM images confirmed the good dispersion of the sepiolite clay, with a low occurrence of small aggregates in the polymeric matrix. Wide-angle X-ray diffraction showed no significant alteration of the crystalline structures of PBAT and starch induced by the sepiolite clay. The addition of sepiolite slightly affected the thermal degradation of the nano-biocomposites; however, the mechanical tests revealed an increase in some mechanical properties, demonstrating that sepiolite is a promising nanofiller for TPS-based materials.