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In this paper, the use of hemp fibers modified with graphite oxide for the removal of methylene blue (MB) from aqueous solutions was investigated. Parameters such as contact time, pH, temperature, initial concentration of dye and ionic strength were varied and their effects on the adsorption recovery were evaluated. The adsorption process attained the equilibrium within 30 min while the adsorption capacity was found to increase with increasing contact time. The experimental data were fitted through a pseudo-second order model. Maximum adsorption capacity slightly increases with temperature changing from 54 mg/g to 58 mg/g at pH = 7.5, from 37 mg/g to 45 mg/g at pH = 3 and from 44 mg/g to 49 mg/g at pH = 12, by increasing the temperature from 20 °C to 80 °C indicating that the process is slightly endothermic (ΔH = 3.43 kJ/mol). The thermodynamic parameters were even calculated demonstrating that the process is spontaneous (ΔG ≈ −4.4 J/mol K and ΔS = 3.16 J/mol K)). Finally, a mathematical algorithm was applied to forecast the response surface model. A second order model was chosen to fit the experimental data and the statistical effect of the process parameters were estimated. A numerical optimization was even performed to individuate the optimal set of process parameters (pH = 9.25, T = 53.8 °C and C0 = 13.2 mg/L) which maximizes the removal capacity. A possible adsorption mechanism was even presented. So, it was proved the efficiency of the adsorption of a novel, inexpensive and sustainable composite material obtained from agro-waste resources by performing reusability cycles.

This research aims for designing and fabricating green and sustainable systems for an efficient removal of methylene blue from aqueous solutions. The hybrid beads, obtained by using ionotropic gelation technique and calcium chloride as cross-linking agent, are composed of sodium alginate matrix, hemp hurd as agro-waste resource and halloysite nanoclay (HNTs). The produced composite beads were characterized morphologically by using SEM and EDX techniques. The batch adsorption studies were performed up to 24 hours using methylene blue (MB) as model hazardous dye in order to investigate the effect of HNTs content (0-35% wt) and pH (2, 7 and 12) on the adsorption capacity. In neutral conditions, a maximum adsorption capacity of 32 mg/g was obtained for sample with 0% of HNTs while it increases up to 41, 43 and 50 mg/g for 5, 20 and 35%wt, respectively. Moreover, swelling/deswelling behavior and point of zero charge (PZC) analysis were even investigated since they are known to affect the adsorption process. A slight increase in PZC can be observed by adding clay nanotubes from 7.42 (0% wt HNTs) up to 7.98 (35% wt HNTs). The experimental data were fitted through first order model, pseudo-second order model and intraparticle diffusion model, demonstrating that the adsorption phenomenon is well described by second order process as well as that the process is mainly characterized by boundary diffusion and intraparticle diffusion. Finally, diffusion of dye was evaluated as function of HNTs content and H+ concentration appearing to decrease from pH=2 up to pH=7 and then to increase in alkaline medium (pH=12). Diffusion coefficient and recovery % trends were modeled through design of experiment methodology.

Poly(ethylene terephthalate) (PET) composites were loaded with four different carbon-based fillers: functionalized carbon nanotubes (CNT), exfoliated graphite (EG), and hybrid materials such as Mg(OH)2, which is primarily used as a flame retardant additive in plastics, dispersed over functionalized CNT and EG. The technology used to mix the different phases was high energy ball milling in dry conditions and at ambient temperature. Morphological organization, thermal and electrical properties of composites were evaluated and correlated with the type of filler. The electrical properties were analyzed over a wide temperature range, from 25 °C to 150 °C, and correlated to the starting structural organization of the composites and the morphological transformations occurred during the thermal heating. The addition of EG and CNTs to PET did not have influence on the amorphous arrangement of unfilled PET, while the loading of Mg(OH)2/EG and Mg(OH)2/CNT fillers favoured the PET crystallization. The crystallization inducted by temperature allowed an increasing in electrical conductivity of the starting amorphous samples. On the other hand, it was found a conductivity independent of temperature for semicrystalline samples (filled with Mg(OH)2/EG and Mg(OH)2/CNT). The charge transport, for the analyzed PET composites, is favoured by the higher degree of crystallinity.

L'article est en accès libre. Je n'arrive pas à ouvrir la fenêtre concernant l'embargo pour pouvoir le mettre en accès libre immédiat. Merci, Eric; International audience; In this article, we show that the chaos and urgency induced by the coronavirus disease 2019 (COVID-19) pandemic has led to massive fossil fuel-derived plastic production, largely ignoring recent environmental policies. Solutions for a sustainable and circular economy require radical innovations, consumer education and most importantly political willingness.

This study aimed to tune the release of non-steroidal, antiinflammatory and antimicrobial diclofenac sodium salt from a bactericidal, pH-sensitive polymer matrix in view of the development of a synergic and combined therapy. The polymer matrix was represented by A(BC)n linear or branched copolymers (n = 1, 2) synthesized by Atom Transfer Radical coPolymerization (ATRP). Manufactures were obtained and analysed in film form, using solvent casting technique. 2-(dimethylamino) ethyl methacrylate (DMAEMA), 2-(diethylamino) ethyl methacrylate (DEAEMA) and 2-(diisopropylamino) ethyl methacrylate (DIPAEMA) have been used as comonomer bearing the bactericidal amino-groups and to modulate the pH-sensitivity of the material. The electrolytic and structural factors of the amino-groups, juxtaposed with the copolymer structure, gave raise to different interactions with the negatively charged diclofenac and imparted a finer control on the drug release kinetics. Data evidenced that copolymers with DMAEMA released diclofenac faster than those with DEAEMA and DIPAEMA; thus, the lower was the amine Kb, the faster was the release. The correlation between copolymer structure and kinetic/equilibrium of the drug release was analysed and correlated with the Tg of copolymers when diclofenac was loaded.

Layered double hydroxides (LDHs) constitute a large family of anionic inorganic clays having interesting and sometimes unexplored characteristics. They are natural, cheap, and simple to be produced, with a high degree of purity. In addition, they can be easily modified by means of organic molecules, and organic modification is an inevitable step for the intercalation of polymer macromolecules into the layers of LDH. The obtained hybrids can be used to prepare polymeric nanocomposites with new properties. The layered structure of LDHs enables the intercalation of polymer macromolecules, and hence the formation of polymer nanocomposites with peculiar functionalities for targeted applications. With appropriate host molecules, nanohybrid LDH molecules can be used as functional fillers able to protect packaged food from bacteria spoilage and pollutant environment. This chapter reviews the state of the art of LDH-active hybrids (i.e., antimicrobials, oxygen scavengers, etc.), with particular attention to their potential use in food-packaging applications. The incorporation process into polymer matrices (either biodegradable or not), the structure of these nanocomposites and the resulting properties (thermal, mechanical, and barrier) are also described. Possible trends and future perspectives are finally proposed and discussed.

Layered double hydroxides (LDHs) have received great attention for years in numerous fields. Controlled and flexible layer composition, as well as the vast assortment of possible anionic guests, and easy adaptability for multipurpose applications, have been some of the many reasons behind their extraordinary success. However, versatility does not only involve the composition or the dimensions of the crystals but also their morphology. Aside from conventional hexagonal, flat structures, three-dimensional assemblies have been reported with architectures closely resembling those of flowers. The possibility of interconnecting the LDH nanosheets in rosette-like geometries has arisen the interest in finding new ways to control, modulate, and guide the particle growth obtaining hierarchical structures to be adapted to specific targets. This review is focused on describing the different strategies implemented to build flower-like assemblies, and on investigating their applications, looking for specific advantages of the use of a three-dimensional architecture over a bi-dimensional one.

The paper reports the formulation of an active packaging based on PET coated with a Layered Double Hydroxide (LDH) hosting 2-acetoxybenzoic anion (salicylate) as antimicrobial molecule. The release of the molecule anchored to the LDH, compared to the molecule free dispersed into the coating, appeared much slower. Permeability of carbon dioxide and oxygen through the packaging at different temperatures was evaluated, as well as the capability of the active material to inhibit Pseudomonas, Listeria and Lactobacillus. Table grape was stored in thermal stress conditions (i.e. 10 °C) into the active packaging and the total mesophilic aerobic count and yeasts and moulds population was evaluated up to 14 days of storage. The experimental results were used for a theoretical prediction of shelf life of the packed grapes and compared with the same fruit packed into untreated material. Global and specific migration of salicylic acid from the active packaging demonstrated, in compliance with the migration limits of the EU regulation, the suitability of the considered material for food contact.

Layered double hydroxide (LDH) nanofillers were considered as hosts of p-hydroxybenzoate as an antimicrobial molecule for active coating. A food grade resin with LDH-p-hydroxybenzoate and two different types of food grade zeolites was used to prepare active coatings for Polyethylene terephthalate (PET) trays. The release kinetics of the active molecule were followed using UV spectrophotometry and the experimental results were analyzed with the Gallagher&ndash, Corrigan model. The thermal properties of the coating mixtures and the PET coating were analyzed and found to be dependent on the coating&rsquo, s composition. On the basis of CO2 transmission rate and off-odors tests, the best coating composition was selected. Global migration in ethanol (10% v/v), acetic acid (3% w/v), and vegetable oil, and specific migration of p-hydroxybenzoic acid revealed the suitability of the material for food contact. Antimicrobial tests on the packaging demonstrated a good inhibition against Salmonella spp. and Campylobacter jejuni. Red meat was packed into the selected active materials and results were compared to uncoated PET packaging. Color tests (browning of the meat) and analysis of Enterobacteriaceae spp. and total viable count evolution up to 10 days of storage demonstrated the capability of the considered active packaging in prolonging the shelf life of red meat.

Antimicrobial packaging systems are recognized as effective approaches to prolong food shelf life. In this context, Bio-based PA11 loaded with a food-grade zeolite were prepared using ball milling technology in the dry state. Zeolite was filled with sodium salicylate, as an antimicrobial agent, and incorporated into the polymer matrix (~50 wt % of salicylate) at different loadings (up to 10 wt %). Structural characterization and an analysis of the physical properties (thermal, barrier, mechanical) were conducted on the composites&rsquo, films and compared with the unfilled PA11. The successful entrapment of the antimicrobial molecule into the zeolite&rsquo, s cavities was demonstrated by the thermal degradation analysis, showing a delay in the molecule&rsquo, s degradation. Morphological organization, evaluated using SEM analysis, indicated the homogeneous distribution of the filler within the polymer matrix. The filler improves the thermal stability of PA11 and mechanical properties, also enhancing its barrier properties against CO2 and O2. The elongated form of the zeolite particles, evaluated through SEM analysis, was used to model the permeability data. The controlled release of salicylate, evaluated as a function of time and found to depend on the filler loading, was analyzed using the Gallagher‒Corrigan model.

Mozzarella cheese can be considered by far the world’s most popular Italian dairy product. Extending the shelf life of mozzarella cheese is an important issue in the dairy industry due to the high risk of contamination by several bacteria species, including spoilage pseudomonads. In this work, active packaging was prepared by coating traditional polyethylene terephthalate (PET) containers of “ovoline” mozzarella cheese with a food-grade resin mixed with a layered double hydroxide (LDH) in which salicylate anion was intercalatedby ionic exchange.. This antimicrobial molecule is listed in EC-Directive 10/2011/EC of 14 January 2011. Morphological arrangement of the molecule into the LDH layers was evaluated by X-ray diffraction (XRD) and controlled release followed by UV spectroscopy. Then, active trays were used to pack the mozzarella cheeses stored for 20 days at 4 °C and under thermal abuse (15 °C). Samples from both conditions showed coliform reduction (by ca. 2 log CFU/g) throughout the storage period. Depending on temperature, total mesophilic aerobic bacteria, Pseudomonas spp., yeasts, and mold loads were reduced in the first 3 days, at 4 °C. Slower acidification and lower proteolysis were also found in treated samples in comparison to control ones. The fitting of the Gompertz function to coliforms and spoilage pseudomonads highlighted an increase in the shelf life of mozzarella cheese of ca. 2 days at 4 °C. These results suggest that salicylate–LDH-coated PET may be applied to extend the shelf-life of mozzarella cheese and also counteract its spoilage if accidental interruptions to refrigeration occur.

The paper is focused on a deep analysis of transport properties of natural hemp fibers (HF) functionalized through a mechano-chemical treatment assisted by high energy ball milling. The effect of milling time on fibers’ morphology was investigated by means of the scanning electron microscopy and FTIR spectroscopy. The results show that the mechanical effect induced a reduction of the mean diameter of hemp fibers and, simultaneously, the achievement of a close packing of cellulose chains. The barrier properties appeared to be dependent either on the packing of cellulose or the water cluster formation. Fick’s law solution in cylindrical coordinates was used to simulate experimental sorption kinetics and to extrapolate the diffusion parameters. The change of diffusion with equilibrium moisture content was described through an empirical relationship. Sorption isotherms were explained on the basis of Park model which accounts for a dual mode sorption at low activities as well as the water clustering phenomenon occurring at high activities. The mean cluster size (MCS) of water molecules was estimated through the application of Zimm Lundberg theory. Finally, the spreading pressure calculation allowed to estimate the driving force of diffusion inside the systems.

Multiscale polymeric composites combining a biodegradable matrix with low cost and biocompatible hybrid nanocarriers promise to supply a new generation of multipurpose devices for drug delivery. The aim of this work was to investigate the release mechanisms of sodium benzoate (NaBz) from halloysite nanotubes (HNTs) embedded in a biodegradable polymer matrix (poly(ϵ-caprolactone)). To that purpose, different amounts of NaBz molecules were successfully incorporated into HNTs using a simple environmentally friendly procedure. The resulting HNT-NaBz nano-hybrids were then incorporated into a poly(ϵ-caprolactone) matrix by high energy ball milling at ambient temperature and in dry conditions. Analysis of the resulting composites showed important effects of the HNT-NaBz nano-hybrids on the thermal and mechanical properties. Controlled drug release, followed by UV spectrophotometry, was also found to be dependent on the HNT-NaBz relative fractions. Experimental data were thus analyzed using a modified Gallagher − Corrigan model and correlated with the nano-hybrid morphologies. © 2016 Society of Chemical Industry

Layered double hydroxide (LDH) modified with different organic molecules were obtained via co-precipitation method. The prepared inorganic-organic hybrids were dispersed at 3 wt% in a low density polyethylene (LDPE) matrix by high energy ball milling (HEBM). Films were obtained and structural organization and thermal, mechanical and oxygen barrier properties investigated. In order to evaluate a possible application in food packaging field, overall migration tests were also conducted on selected composites. They were used acetic acid 3% and ethanol 10%, to simulate foods with acidic and hydrophilic character in non-swelling conditions, and alcoholic foods and dairy products under more swelling conditions, respectively.

Novel active coatings from renewable sources were developed using a pectin matrix and a modified layered double hydroxyde (LDH), as filler. The active molecule, ionically bonded to the LDH, was sodium salicylate. The hybrid filler loading was 5 wt% of LDH-salicylate, with a total content of active molecule into the composites of 1.6 wt%. The degree of plasticization of the composites varied in the range 4–16 vol % of glycerol. Morphological, thermal and barrier properties of the composites were analyzed. The x-ray analysis showed a complete delamination of the hybrid filler at any glycerol loading. The thermal degradation behavior and mechanical properties resulted strictly influenced by the glycerol content. Barrier properties (sorption, diffusion and permeability) to water vapor indicated that composite plasticized with 4 vol% of glycerol showed the best improvement of barrier properties. This suggested that the interaction pectin-active filler-degree of glycerol plays a significant role in determining the transport phenomena. Fresh apricots were coated with the active composite plasticized with 4 vol % of glycerol, demonstrating the efficiency of this formulation in extending the preservation of such fruits.

A novel antimicrobial packaging system, as active coating on a commercial Poly(ethylene terephthalate) (PET) film, was formulated and tested in vitro against the spoilage bacteria of Mozzarella cheese. It is based on layered double hydroxide (LDHs) intercalated with salicylate and carbonate anions dispersed in a solvent-based heat seal. The population of spoilage microorganisms (total coliforms, Pseudomonas, fungi), along with the functional microbiota of Mozzarella cheese (lactic acid bacteria) was characterized. Microbial shelf life was evaluated at 18 °C, to simulate thermal abuse. Experimental results show an increase in the microbial shelf life of the packaged Mozzarella cheese of about 20 days, confirming that the investigated active coating may exert an inhibitory effect on the microorganisms responsible for spoilage phenomena, without affecting the functional microbiota of the product.

The aim of this study was the assessment of high energy ball milling technique to develop poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) nanocomposites containing bacterial cellulose nanowhiskers (BCNW). Crystallization behaviour of PHBV/BCNW nanocomposites was studied under non-isothermal and isothermal conditions using differential scanning calorimetry. The changes in PHBV crystalline structure were also studied using X-ray diffraction. The results confirmed that BCNW acted as nucleating agents and, hence, favored the crystallization of the PHBV. The oxygen permeability of the nanocomposites was reduced by ~22 % when compared to that of the neat PHBV. This work provides a new insight into the development of polyhydroxyalkanoate composites by means of the high energy ball milling technique., J. Ambrosio-Martín would like to thank the Spanish Ministry of Economy and Competitiveness for the FPI grant BES-2010-038203. M. J. Fabra is recipient of a “Juan de la Cierva” contract from the Spanish Ministry of Economy and Competitiveness. The authors acknowledge financial support from the MINECO (MAT2012-38947-C02-01 project) and from the FP7 ECOBIOCAP project.

Membranes based on poly(&epsilon, caprolactone)/poly(3-hydroxybutyrate) blends (PCL/PHB at 50 wt%) were obtained by electrospinning and curcumin encapsulated at 1 wt% as active agent, as drug delivery systems for biomedical applications. PCL and PHB were also separately electrospinned and loaded with 1 wt% of curcumin. The processing parameters of PHB were drastically different from PCL and the blend PCL/PHB, in fact, the temperature used was 40 &deg, C, and the distance injector&ndash, collector was 28 cm. Different conditions were used for PCL: lower temperature (i.e., 25 &deg, C) and shorter distance injector&ndash, collector (i.e., 18 cm). The blend was processed in the same conditions of PCL. The fibers obtained with PHB showed diameters in the order of magnitude of micron (i.e., &asymp, 3.45 &micro, m), while the PCL mats is composed of fiber of nanometric dimensions (i.e., &asymp, 340 nm). PCL/PHB blend allowed to obtain nanometric fibers (i.e., &asymp, 520 nm). Same trend of results was obtained for the fibers&rsquo, porosity. The morphology, thermal, mechanical and barrier properties (sorption and diffusion) through water vapor were evaluated on all the electrospun fibers, as well as the release behavior of curcumin, and correlated to the processing parameter and the fibers&rsquo, morphologies.

Two-dimensional (2D) nanomaterials have received much attention in recent years, because of their unusual properties associated with their ultra-thin thickness and 2D morphology. Besides graphene, a new 2D material, molybdenum disulfide (MoS2), has attracted immense interest in various applications. On the other hand, ball-milling process provides an original strategy to modify materials at the nanometer scale. This methodology represents a smart solution for the fabrication of MoS2 nanopowders extremely-efficient in adsorbing water contaminants in aqueous solution. This work reports a comprehensive morphological, structural, and physicochemical investigation of MoS2 nanopowders treated with dry ball-milling. The adsorption performances of the produced nanopowders were tested using methylene blue (MB) dye and phenol in aqueous solution. The adsorption capacity as a function of ball-milling time was deeply studied and explained. Importantly, the ball-milled MoS2 nanopowders can be easily and efficiently regenerated without compromising their adsorption capacity, so to be reusable for dye adsorption. The eventual toxic effects of the prepared materials on microcrustacean Artemia salina were also studied. The present results demonstrate that ball-milling of MoS2 offers a valid method for large-scale production of extremely efficient adsorbent for the decontamination of wastewaters from several pollutants.

This paper reports the preparation of green pesticides based on nano-hybrids composed of a Layered Double Hydroxide (LDH) with cinnamate anion. The dispersion into a pectin matrix was obtained using high energy ball milling in wet conditions. Structure and physical properties of the fillers and the composites films were evaluated. Controlled release of cinnamate was followed using UV spectrophotometry and the release kinetics were found to be dependent on the filler loading. The experimental results were analyzed by the Gallagher-Corrigan model. Antimicrobial activity was evaluated on different bacterial strains, as well as plant pathogens belonging to the genus Phytophthora using modified agar diffusion, broth microdilution and dual culture methods, respectively. Experimental results suggested the possibility to use the analyzed composites as green protective coatings for crops’ protection.

Nowadays, there is growing increase of plastics use in the world of food industry and medicine. In this context there is a need of, apart from conventional properties of plastics, minimizing growth of harmful microorganisms. In this article new polymer based materials are prepared, characterized and evaluated against their antibacterial action. New materials based on poly(ethylene-co-vinyl acetate) are prepared by solution blow spinning, SBS. Mats of nanocomposites constituted by micrometric fibers are obtained with compositions ranging from 0% to 6% by weight of Cu nanoparticles, CuNp. In order to understand the effect of the CuNp on the E. coli cell adhesion and biofilm formation, morphology, structure, thermal and surface properties of the nanocomposites are studied by several techniques. SBS allows preparing the nanocomposites with quite uniform dispersion of CuNp within the polymer. Neither the presence of CuNp nor the SBS process induce changes in the structure and in the thermo-degradation of EVA40. The presence of CuNp exerts antibacterial effect against the DH5α E. coli. There is a direct action of the CuNp on the extracellular polymeric substances and on the bacterial metabolism. CuNp also affect HaCaT cells growing, delaying the process at higher amounts of Cu but keeping their viability.

Two-dimensional (2D) nanomaterials have received much attention in recent years, because of their unusual properties associated with their ultra-thin thickness and 2D morphology. Besides graphene, a new 2D material, molybdenum disulfide (MoS2), has attracted immense interest in various applications. On the other hand, ball-milling process provides an original strategy to modify materials at the nanometer scale. This methodology represents a smart solution for the fabrication of MoS2 nanopowders extremely-efficient in adsorbing water contaminants in aqueous solution. This work reports a comprehensive morphological, structural, and physicochemical investigation of MoS2 nanopowders treated with dry ball-milling. The adsorption performances of the produced nanopowders were tested using methylene blue (MB) dye and phenol in aqueous solution. The adsorption capacity as a function of ball-milling time was deeply studied and explained. Importantly, the ball-milled MoS2 nanopowders can be easily and efficiently regenerated without compromising their adsorption capacity, so to be reusable for dye adsorption. The eventual toxic effects of the prepared materials on microcrustacean Artemia salina were also studied. The present results demonstrate that ball-milling of MoS2 offers a valid method for large-scale production of extremely efficient adsorbent for the decontamination of wastewaters from several pollutants.

The formulation of cost-effectiveness sustainable materials is extensively growing and becoming an attractive approach for both industrial and academic fields. In this context, the bio-based aliphatic polyamide 11 (PA11) has acquired significant interest as environmentally friendly thermoplastic option. In addition, its formulation with selected natural antioxidant and/or reinforced compounds through green processing methods, might improve physical and mechanical properties without sacrificing the intrinsic bio-based nature of the matrix. In this work, we have investigated and compared the photo oxidative degradation processes occurring on PA11 composites based on thymol and halloysite nano tubes prepared by using ball-milling method. In particular, halloysite nanotubes were used as green nano-container of a natural antioxidant molecule, and reinforced nano-filler as well. Molecular and structural information of photo-exposed samples were obtained by using size exclusion chromatography (SEC) and matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS). Thermal and mechanical properties were also tested as well as thymol release. Data collected confirmed that PA11 filled with HNTs-Thymol nano-hybrid showed superior durability performance if compared to both pure PA11 and PA11 blend realized by simply adding thymol and HNTs to polymer matrix. Furthermore, we found that HNTs and thymol combined in the nano-hydrid form exhibited an active and synergic role to achieve a major photo stabilization of PA11 biocomposite, without sacrificing its mechanical properties. (C) 2018 Elsevier Ltd. All rights reserved.

This paper reports the surface treatment of layered double hydroxide (LDH) by using ionic liquid (IL) composed of phosphonium cation combined with 2-ethylhexanoate (EHT) counter anion as surfactant agent. Then, different amounts (1, 3, 5 and 7 wt %) of thermally stable organically modified LDH (up to 350 °C) denoted LDH-EHT were incorporated into polycaprolactone (PCL) matrix by mechanical milling. The influence of LDH-EHT loading has been investigated on the physical properties, such as the thermal and barrier properties, as well as the morphologies of the resulting nanocomposites. Thus, intercalated or microcomposite morphologies were obtained depending on the LDH-EHT loading, leading to significant reduction of the diffusion coefficient respect to water vapor. The modulation of barrier properties, using low functionalized filler amount, is a very important aspect for materials in packaging applications.

This chapter reviews hydrolytic degradation and biodegradation of poly(lactic acid) (PLA). Hydrolytic degradation, which induces morphological and compositional changes, is considered the most important step in biodegradation. The main factors influencing hydrolytic degradation (temperature, pH, sample morphology, and molecular weight) are considered and analyzed. An overview of biodegradation under composting conditions is also given. The chapter also analyses the possibilities of modulating degradation and biodegradation rates according to the expected lifetime of objects made of PLA. This can be considered frontier research in this field.

Halloysite nanotubes (HNTs) were loaded with lsozyme, as antimicrobial molecule, at a HNTs/lysozyme ratio of 1:1. Such a nano-hybrid was incorporated into a poly (ε-caprolactone) (PCL) matrix at 10 wt % and films were obtained. The nano-composites were submitted to a cold drawn process at three different draw ratios, λ = 3, 4, and 5, where λ is l(final length)/l0(initial length). Morphology, physical, and barrier properties of the starting nanocomposite and drawn samples were studied, and correlated to the release of the lysozyme molecule. It was demonstrated that with a simple mechanical treatment it is possible to obtain controlled release systems for specific active packaging requirements.

Phosphonium ionic liquid (IL) combined with 2-ethylhexanoate counter anion has been used as interfacial agent of layered double hydroxide (LDH). First, the intercalation of hexanoate anion between the LDH layers was confirmed by thermogravimetric analysis (TGA) and X-ray diffraction (XRD). Then, this thermally stable organophilic LDH was introduced at different amount (1, 3 and 5 wt%) into pectin matrix leading to an increase of the thermal stability of the resulting nanocomposites (+35–40 °C). In addition, the good distribution of the modified LDH led to an increase of the mechanical performances through the elastic moduli (+60%) as well as a significant increase of the water barrier properties of two orders of magnitude for the pectin containing 5 wt% of LDH-Ionic Liquid.

In this work, new copolymers containing either MMA and 18C6 crown-ether pendants, or PEG, MMA and 18C6 crown-ether pendants were synthesized to test the idea that sequestering structural alkali-earth ions from the bacterial outer membrane (OM) may lead to bacterial death. The copolymers were obtained either via uncontrolled radical polymerization or ATRP; the latter approached allowed us to produce not only linear copolymers but also branched Y-like structures. After checking for the capability of complexing magnesium and calcium ions, the antimicrobial activity of all copolymers was tested placing their casted plaques in contact with pure water E. coli suspensions. All plaques adsorbed alkali-earth ions and killed bacteria, albeit with different antimicrobial efficiencies. Differences in the latter characteristic were attributed to different plaque roughness. The role of the 18C6 crown-ether pendants was elucidated by pre-saturating plaques with Mg/Ca ions, the marked reduction in antimicrobial efficiency indicating that losing the latter from OM due to surface complexation does play an important role in killing bacteria at short (

Composites based on Poly(ethylene terephthalate) (PET) and Halloysite nanotubes (HNTs) were prepared through high energy ball milling (HEBM) at ambient temperature and with no solvents. A wide range of HNTs loading was used (i.e. 1–7 wt%) and films produced. Morphological organization and physical (thermal, degradation, mechanical) properties were analyzed and correlated to HNTs content. HNTs were also filled with an antimicrobial model molecule, sodium benzoate, to test the effectiveness of such nano-containers as filler for polymers to be used in active packaging, enlightening very good perspectives in this field.

The synthesis of star-like A(B)n copolymers based on the hydrophilic poly(ethylene glycol) monomethyl ether (m-PEG, block A) and the hydrophobic poly(methyl methacrylate) (PMMA, blocks B) is reported. We obtained copolymers made of one m-PEG chain and 2 or 4 PMMA blocks using a combined “arm first”—“core first” approach. Such structures were called tree-shaped copolymers where the m-PEG was considered as the trunk and PMMA arms as the branches. Star-like copolymers (B)nA-A(B)n built by two tree-shaped fragments with a poly(propylene oxide) (PPO) as the central junction, were also synthesized according to a previously reported procedure. The latter were called star-shaped structures and the synthesis was performed to obtain architectures different from the tree-shaped one but characterized by a similar length of the PMMA arms. Microstructural analysis was carried out through 1H-NMR and GPC, and the thermal and transport properties (sorption and diffusion) to liquid water were investigated and correlated to...

The lamellar structure of montmorillonite (MMT) clays exhibits an interesting potential to improve the barrier properties of thermoplastic polyurethanes (TPU). However direct melt blending of an ester-based TPU and functional organoclays, despite showing good filler dispersion, did not allowed for improving neither barrier properties (i.e., sorption and diffusion to water vapor) not mechanical performances with respect to the unfilled TPU. Therefore, two alternative strategies involving poly(e-caprolactone) (PCL)/organoclay masterbatches were explored to investigate the possibility to prepare materials with improved mechanical and barrier properties. In the first strategy, a PCL/organoclay masterbatch with high inorganic content was obtained by melt-blending (coined “free PCL” masterbatch), whereas in the second strategy PCL-grafted organoclay nanohybrids, also with high inorganic content were synthesized by in situ intercalative grafting/ring-opening polymerization of e-caprolactone (CL). Purposely, ROP of CL was initiated from hydroxyl groups available onto the MMT surface actually organo-modified by alkylammonium cations bearing hydroxyl functions (coined “nanohybrid PCL” masterbatch). These highly-filled PCL masterbatches (with ca. 25 wt% in inorganics) were then added into the ester-based TPU to prepare nanoclay/polyurethane nanocomposites by melt-blending. The morphology and dispersion of the resulting materials were characterized by X-ray diffraction and transmission electron microscopy. Improved sorption and diffusion properties towards water vapor as well as mechanical properties were measured. Herein, these results are discussed as a function of both clay dispersion and matrix/organoclay interaction.

PLA nanocomposites at various Halloysite (HNT) loadings are produced by melt-mixing and then shaped as films. HNT is additionally surface-treated by silanization reaction with 3-(trimethoxysilyl)propyl methacrylate (TMSPM). The morphology, thermal and transport properties to water vapor (sorption, diffusion, permeability) of nanocomposite films are examined and compared to those of neat PLA. Due to the good nanofiller dispersion within PLA matrix, favorable interactions between components and other specific characteristic features (thermal, mechanical, optical), these nanocomposites are potentially interesting for use as environmental friendly packaging materials.

In this paper the barrier properties to water vapour of polylactic acid (PLA) films prepared with different thermal treatments were analyzed with the aim of correlating them to the morphology of the samples. The crystallization kinetics of the material was assessed during isothermal steps reached after cooling from the melt or heating from the solid. The temperature at which the maximum crystallization rate was attained was selected as the crystallization temperature for the samples analyzed for barrier properties. The structural and morphological organization was analyzed by means of X-ray diffraction analysis, differential thermal analysis (DSC) and optical analysis. Sorption and diffusion experiments were conducted either varying the temperature or the morphology of the samples. It was found that sorption was mainly dependent on the amount of the permeable non crystalline phase, while diffusion was also dependent on the morphological organization of the crystalline domains. Open image in new window

Novel biodegradable composites were prepared using PLA and a nano-hybrid composed of halloysite nanotubes (HNTs) filled with Lysozyme, as antimicrobial. The nano-hybrid was characterized from a structural point of view and the Lysozyme content evaluated by thermogravimetric analysis. Several composites were prepared using ball milling, in dry conditions at ambient temperature, varying the nano-hybrid loading (i.e. 3, 5, 10 wt%). The structural organization and physical properties (thermal, mechanical and barrier to water vapor) ware analyzed and correlated to the nano-hybrid content. Controlled Lysozyme release into saline solution was followed using UV spectrophotometry. The release kinetics was found to be dependent on HNTs-Lysozyme relative fractions. The experimental results were analyzed by a modified Gallagher-Corrigan model.

This review aims to provide a description of the recent advances in the preparation of polymer nanocomposites via mechanical milling. An assessment of possible future scenarios that could be created by the utilization of improved experimental methodologies and a deeper understanding of structure-property relationship is also provided. It is then reported, in a logical sequence, crucial information on five subjects: (i) the motivation of fundamental and applied research in the field of thermoplastic and thermosetting polymer nanocomposites, (ii) the mechanochemical response of polymeric substances to mechanical activation, (iii) the broad spectrum of experimental behaviours exhibited by the most studied classes of polymers, (iv) the methodology for the mindful utilization of mechanical processing to mix polymers and disperse heterophases, and (v) the physico-chemical approach to describing the kinetics of mechanically activated transformations. In addition, critical questions regarding the advantages and disadvantages of mechanical processing compared to more conventional dispersion methods are highlighted. Finally, the general trends in the current research are discussed, and possible future perspectives in this field are briefly described.

Nanohybrid active fillers are gaining interest from basic and applied research, due to their potential to provide quality and safety benefits. Great attention has been devoted in the last decade to the hybrid organic-inorganic systems, in particular to those in which inorganic materials are dispersed at a nanometric level in polymeric matrices. This review presents some important examples of the most used inorganic nanometric fillers, with antimicrobial activity for potential active packaging applications. Particular emphasis is given to biodegradable polymer matrices such as aliphatic polyesters, polysaccharides, proteins, and their blends. As food contact materials, they present the possibility of being carriers of different additives, such as antioxidant, antimicrobial, nutraceuticals, and flavoring agents. Current regulation issues are also reported and discussed and possible trends and perspectives in the food contact field shortly commented.

Novel hybrid materials, obtained by direct Catalytic Chemical Vapour Deposition (CCVD) growth of carbon nanotubes (CNT) over a clay mineral catalyst, were incorporated into Polylactic acid (PLA) through melt mixing. Nanocomposites in the form of films were exposed to UV irradiation at constant temperature (30 degrees C) and relative humidity (50%). Young's Modulus measurements show a strong mechanical degradation with the UV irradiation time. The decrease was higher in neat PLA compared with nanocomposites and was attributed to the extensive macromolecular chain scission due to the UV irradiation. From thermogravimetric characterization it was found that the degradation temperature decreases with the photoageing. The addition of the hybrid filler causes an initial decrease of this temperature (up to 3%) and a slight increase thereafter. A similar behaviour was found for the enthalpy relaxation during the morphological rearrangement which occurred in the glass transition process. Indeed, the electrical conductivity of the nanocomposites was found to monotonically increase with the UV irradiation time. (C) 2012 Elsevier B.V. All rights reserved.

Poly(e-caprolactone)-coated (covalently grafted and physisorbed) multi-walled carbon nanotubes (MWCNTs) were synthesized by ring-opening polymerization (ROP) of e-caprolactone initiated from primary amines grafted on the MWCNT surface through the exposure to atomic nitrogen generated in a microwave-induced plasma. The morphology of the recovered nanohybrids and the amount of grafted polymer chains were studied by transmission electron microscopy (TEM) and thermogravimetric analysis (TGA), respectively. These nanohybrids were used as highly filled masterbatches to be dispersed within either poly(e-caprolactone) (PCL) or high-density polyethylene (HDPE) matrices in the molten state. The thermal behavior as well as the electrical properties of the so-produced nanocomposites were characterized and correlated to their morphology. The HDPE filled with PCL-coated MWCNTs nanohybrids showed better electrical properties than HDPE filled with non-modified MWCNTs. The electrical properties improvement was associated to a better dispersion of the PCL-coated MWCNTs and, also, to the exclusive presence of PCL coating in tunneling junction between the nanotubes.

Preparation and analysis of morphology, mechanical, and electrical properties of nanocomposites based on ethylene vinyl acetate (EVA) copolymer and commercial multiwalled carbon nanotubes (CNTs) was achieved. The used techniques for obtaining nanocomposites were the conventional melt-mixing and the in situ ethylene polymerization/coating reaction, as catalyzed directly from CNT surface, with different polyethylene content (i.e. 55.0% and 66.6%). Nanocomposites were also prepared using crude CNTs. The incorporation in the molten state of such polyethylene surface-coated CNTs, used as “masterbatch,” in EVA was demonstrated a good strategy for allowing the complete destructuring of the native bundle-like aggregates, leading to the preparation of polymer nanocomposites with largely improved properties, even at very low nanofiller content. Copyright © 2011 John Wiley & Sons, Ltd.

Multi walled carbon nanotubes have been incorporated into a linear low density polyethylene matrix through high energy ball milling technique at room temperature, without any chemical modification or physical treatment of the nanotubes. Highly oriented samples, with different draw ratios, were obtained by drawing at 80 °C the composite films. SEM and FTIR results on the drawn PE films demonstrate that the molecular chains in both crystalline and amorphous phases are well oriented along the drawing direction. The effect of different weight percent loadings of nanotubes and draw ratio on the morphology, thermal, mechanical and electrical properties of the composite fibers have been investigated.

Preparation and analysis of morphologic and electrical properties of high-performance multi-walled carbon nanotube/polyamide 6 nanocomposites was achieved. The MWNTs were surface-coated by in situ polymerization of ethylene as catalyzed directly from the nanotube surface previously treated by a highly active metallocene-based complex. The so-produced polyethylene-coated MWNTs were melt-mixed with the PA6 matrix. Pristine MWNTs were also dispersed in PA6. The in situ ethylene polymerization/coating reaction allowed the destructuring of the native bundle-like aggregates leading to the preparation of nanocomposites with improved properties even at very low nanofiller content.

Dense films based on the hydrophobic Pebax&reg, 2533 were prepared by using solution casting in different solvents as well as compression molding and subjected to photo&ndash, aging under ultraviolet (UV) irradiation. The influence of the preparation method, including the casting solvents, as well as the UV irradiation time selected to treat the samples, were evaluated in terms of permeation rates of pure gases (CO2, N2, O2, CH4, He, and H2). The transport data were correlated with the microstructure and surface properties by using differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS), as well as water contact angle measurements. The obtained results showed that a controlled photo-oxidation process reduces the hydrophobicity of the Pebax&reg, 2533 films, increasing their permeability without compromising their integrity.

Sodium montmorillonite was incorporated into a poly(epsilon-caprolactone)-starch blend by means of a ball mill. The structural organization and physical (mechanical, thermal and barrier) properties were analyzed and correlated with the milling conditions. Scanning electron microscopy and X-ray characterization show that the milling process can improve the compatibilization between the PCL and the starch phases, while promotes the dispersion of clay minerals at nanometric level. The milling time strongly influences the mechanical and barrier properties. In particular, the best results in terms of elastic modulus and permeability coefficient were achieved with a complete delamination of the pristine clay structure. In summary, the milling process not only has demonstrated to be a promising compatibilization method for immiscible PCL-starch blends, but it can be also used to improve the dispersion of nanoparticles into the polymer blends. (C) 2008 Elsevier Ltd. All rights reserved.

Lignin powder, obtained from an abundant and low-cost source, straw, through a low-environmental-impact process, steam explosion, was used for the preparation of blends with a biodegradable polyester, poly(e-caprolactone) (PCL), with an innovative technique, high-energy ball milling. Lignin strongly stabilized PCL against UV radiation. The modulus of the blends increased with the addition of lignin; nevertheless, the elongation at breaking decreased. Through thermal characterization (differential scanning calorimetry and dynamic mechanical analysis), lignin and PCL were found to be immiscible. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

We have successfully synthesized poly(lactide), poly(glycolide), and poly(lactide- co -glycolide) copolymers in bulk by ring-opening homo- and copolymerization of glycolide and l -lactide, using sodium hydride as the environmentally friendly and nontoxic initiator. Random copolymers were obtained, and the microstructure was characterized by nuclear magnetic resonance ( 1 H and 13 C NMR) and matrix-assisted laser desorption ionization mass spectrometry (MALDI MS). The mechanism of reaction was elucidated by analysis of the polymer end groups. Homopolymer and copolymers films and their blends were obtained, and structure and physical properties analyzed. Thermal degradation analysis showed superior characteristics of copolymers with respect to the blends. Transport properties of water vapor were also evaluated and correlated to the copolymer composition.

Nanocomposites of polylactide (PLA) and functionalized graphene sheets (FGS) were obtained via melt compounding. Pre-incorporation of the FGS fillers into lactic acid oligomers (OLLA) by in situ melt polycondensation was performed with the aim of improving the FGS dispersion and distribution into the polymeric matrix. To evaluate the effect of the pre-incorporation step, a comparison with direct addition of the filler to the melt mixing process was carried out. Addition of OLLA and FGS led to enhanced better barrier properties. Specifically, reductions of up to 45% and 41% in oxygen and water vapor permeability were achieved, respectively. Mechanical and electrical properties of the PLA and its nanocomposites were also studied and correlated with both the addition of oligomers and the incorporation method., J. Ambrosio-Martın would like to thank the Spanish Ministry ofEconomy and Competitiveness for the FPI grant BES-2010–038203. M.J. Fabra is recipient of a “Juan de la Cierva” contractfrom the Spanish Ministry of Economy and Competitiveness. Theauthors acknowledge financial support from the MINECO(MAT2012–38947-C02-01 project) and from the FP7 ECOBIO-CAP project.

This work aims to evaluate the possibility to introduce natural nano-containers for active molecules, such as halloysite nanotubes (HNTs), into an environmentally friendly material: natural zein. Composites were prepared in a wide range of HNTs composition (i.e. 1–10 wt%) and structural and physical properties were analyzed. HNTs were also filled with an active molecule commonly used as preservative in food packaging, such as potassium sorbate (KS), and the diffusion of such molecule was evaluated. The zein thermal degradation resulted significantly improved with the filler content. Mechanical properties showed a reinforcement of zein matrix. HNTs were filled with potassium sorbate and dispersed into the zein matrix.

While our society is becoming more and more aware of the importance of sustainable development, green chemistry and renewability, poly(glycolide) (PGA), poly(lactide) (PLA) and their copolymers have already proven to be a valid, renewable alternative to the petrobased plastics in a wide range of applications. The most efficient way to obtain these polymers is via ring-opening polymerization (ROP) of their cyclic esters, and the most common initiator is tin octoate. Although it is FDA approved, its cytotoxicity raises several issues, along with the need of a more benign initiator. We have already reported the polymerization of ?-caprolactone promoted by sodium hydride (NaH). We now report on the use of NaH as initiator in the ROP of L-lactide, glycolide and in their copolymerization for the synthesis of poly[glycolide-co-(L-lactide)]s (PLGAs). NaH is not only a commercially available, cheap and easy-to-handle compound, but also a non-toxic initiator. Polymerization runs have been performed in bulk, without solvents, and random copolymers were obtained in the case of PLGAs. Their microstructure was characterized by nuclear magnetic resonance (1H and 13C NMR) and matrix assisted laser desorption time of flight mass spectrometry (MALDI MS). Thermal properties were studied via thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). Transport properties to water vapour were also evaluated and correlated to the copolymer composition.