Nanocomposite polymer films containing carvacrol for antimicrobial active packaging

Nanocomposite films based on low‐density polyethylene (LDPE) containing carvacrol were prepared and characterized with the aim to get antimicrobial active packaging. Organo‐modified montmorillonite (MMT) was used as filler. The weak interaction between LDPE and clay led to the formation of intercalated systems. On the other hand, strong interaction between carvacrol and organosilicate allowed a good dispersion of the oil into the clay galleries, promoting the swelling of MMT stacks and a higher polymer/clay interface. As a result, carvacrol was protected against thermal degradation and its release from the films was efficiently delayed. Moreover, outstanding thermal oxidative stability as well as improved oxygen barrier properties were detected in the nanocomposite containing carvacrol. The presence of clay and carvacrol also increased LDPE crystallinity, due to an enhanced nucleation activity, while the mechanical properties of the films were slightly affected. The antimicrobial properties of carvacrol containing films were tested, showing a significant activity against several bacterial strains, which is preserved in presence of the clay. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers     

The combined effect of additives and processing on the thermal stability and controlled release of essential oils in antimicrobial films

Essential oils (EOs) have a long history as food preservatives and many advantages compared to synthetic preservatives. The major limitation of EOs as antimicrobial agents incorporated into a polymeric matrix is their low thermal stability and their high volatility from polymers. This study suggests a new methodology approach to bypass the key limitations of adding EOs into active packaging, as food preservatives. Antimicrobial active films based on linear low density polyethylene (LLDPE) and Montmorillonite (MMT) were produced by incorporating the EO thymol in a stepwise procedure. The production of the film composites, containing thymol, has been conducted, under a protocol of three stages: (1) production of a highly porous nano composite master batch; (2) impregnation of thymol into the master batch; and (3) cast film extrusion. Adding MMT incorporated together with a foaming agent at stage‐(1) increased significantly the heat stability of the EO during melt processing at stage‐(3). Finally, the film obtained showed a high antimicrobial activity. The results obtained have proven the synergistic interaction between MMT, foaming agent and thymol. As the MMT content in the film increased, the loss of EO in the processing decreased, leading to a natural antimicrobial film with improved antibacterial properties. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40564.     

Photodegradation of some low‐density polyethylene–montmorillonite nanocomposites containing an oligomeric compatibilizer

The photo‐oxidation behavior at the exposed surfaces of maleated low‐density polyethylene [LDPE poly(ethylene‐co‐butylacrylate‐co‐maleic anhydride) (PEBAMA)] and montmorillonite (MMT) composites was studied using attenuated total reflection Fourier transform infrared spectroscopy, X‐ray diffraction (XRD), transmission electron microscopy (TEM), and mechanical testing. Two different MMT clays were used with the maleated polyethylene, an unmodified clay, MMT, and an organically modified montmorillonite (OMMT) clay which was significantly exfoliated in the composite. The morphologies of sample films were examined by XRD and TEM. The results were explained in terms of the effect of the compatibilizing agent PEBAMA on the clay dispersion. It was found that the OMMT particles were exfoliated in the polymer matrix in the presence of the PEBAMA, whereas the MMT clay particles were agglomerated in this matrix. Both mechanical and spectroscopic analyses showed that the rates of photo oxidative degradation of the LDPE‐PEBAMA–OMMT were higher than those for LDPE and LDPE‐PEBAMA–MMT. The acceleration of the photo‐oxidative degradation for LDPE‐PEBAMA–OMMT is attributed to the effects of the compatibilizer and the organic modifier in the composite. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40788.     

LDPE composite films incorporating ceramic powder emitting far‐infrared radiation for advanced food‐packaging applications

A ceramic powder that emits far‐infrared radiation (FIR) was incorporated into low‐density polyethylene (LDPE) via melt‐compounding and subsequent melt‐extrusion processes. To investigate the feasibility of as‐prepared LDPE/FIR composite films for use in packaging applications, the composite films were characterized using Fourier transform infrared spectroscopy, X‐ray diffraction, scanning electron microscopy, thermogravimetric analysis, differential scanning calorimetry, FIR emissivity and emissive power, antimicrobial activity assays, and storage tests. The physical properties and antimicrobial activities of the composite films were found to strongly correlate with the changes in the chemical and morphological structures that originate from different contents of FIR ceramic powder. A higher content of FIR ceramic powder in the LDPE/FIR composite film provided increased FIR emissivity and emission power of the composite and resulted in good antimicrobial activity. Storage tests also showed that incorporation of FIR ceramic powder into LDPE film was an effective method for maintaining the freshness of lettuce. Furthermore, the incorporation of FIR ceramic powder into LDPE films induced higher thermal stability and crystallinity and enhanced their barrier properties, which suggest these LDPE/FIR composite films are potential candidates for advanced packaging materials for the food and medical industries. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43102.     

Poly(vinyl alcohol) nanocomposites with different clays: Pristine clays and organoclays

Poly(vinyl alcohol) (PVA)/clay nanocomposites were synthesized using the solution intercalation method. Na ion‐exchanged clays [Na⁺–saponite (SPT) and Na⁺–montmorillonite (MMT)] and alkyl ammonium ion‐exchanged clays (C₁₂–MMT and C₁₂OOH–MMT) were used for the PVA nanocomposites. From the morphological studies, the Na ion‐exchanged clay is more easily dispersed in a PVA matrix than is the alkyl ammonium ion‐exchanged clay. Attempts were also made to improve both the thermal stabilities and the tensile properties of PVA/clay nanocomposite films, and it was found that the addition of only a small amount of clay was sufficient for that purpose. Both the ultimate tensile strength and the initial modulus for the nanocomposites increased gradually with clay loading up to 8 wt %. In C₁₂OOH–MMT, the maximum enhancement of the ultimate tensile strength and the initial modulus for the nanocomposites was observed for blends containing 6 wt % organoclay. Na ion‐exchanged clays have higher tensile strengths than those of organic alkyl‐exchanged clays in PVA nanocomposites films. On the other hand, organic alkyl‐exchanged clays have initial moduli that are better than those of Na ion‐exchanged clays. Overall, the content of clay particles in the polymer matrix affect both the thermal stability and the tensile properties of the polymer/clay nanocomposites. However, a change in thermal stability with clay was not significant. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 3208–3214, 2003     

Structural characterization of LDPE/EVA blends containing nanoclay‐flame retardant combinations

The combination of different types of organo‐modified montmorillonite (MMT) with aluminum hydroxide (aluminum trihydrate—ATH), as a flame retardant system for polyethylene‐ethylene vinyl acetate (LDPE/EVA), blends were studied. Five different types of organically modified montmorillonite clays, each with different modifier, were used. The structural characterization was carried out by X‐ray diffraction (XRD) and scanning electron microscopy in transmission mode (STEM). The mechanical and rheological properties were also evaluated. The XRD analysis showed a clear displacement of the d₀₀₁ signal, which indicates a good degree of intercalation, especially for the MMT‐I28 and MMT‐20, from Nanocor and Southern Clay Products, respectively. The presence of ATH and the compatibilizer did not have any effect on the exfoliation of the studied samples. The thermal stability and flame retardant properties were evaluated by thermogravimetric analysis (TGA), limiting oxygen index (LOI—ASTM D2863), and flammability tests (Underwriters Laboratory—UL‐94). The effect of different compatibilizers on the clay dispersion and exfoliation was studied. The results indicated that the addition of montmorillonite makes it possible to substitute part of the ATH filler content while maintaining the flame retardant requirements. The thermal stability of MMT/ATH‐filled LDPE/EVA blends presented a slight increase over the reference ATH‐filled LDPE/EVA blend. Compositions with higher clay content (10 wt %) showed better physicochemical properties. The increased stability of the higher clay content compositions results from the greater inorganic residual formation; this material has been reported to impart better performance in flammability tests. The mechanical properties and flame retardancy remained similar to those of the reference compound. The reduced ATH content resulted in lower viscosities and densities, facilitating the processing of the polymer/ATH/clay compounds. Extrusion of these compounds produced a lower pressure in the extrusion head and required reduced electrical power consumption. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Short‐ and long‐term loss of carvacrol from polymer/clay nanocomposite film – a chemometric approach

A combination of partial least squares (PLS) regression and design of experiments was used to analyse and define the short‐ and long‐term loss mechanisms of carvacrol from polymer/clay nanocomposite films used as an antimicrobial food packaging material. Three formulation x variables were evaluated: type of nanoclay, concentration of nanoclay and concentration of compatibilizer agent. Five experimental y responses were measured: loss of carvacrol from the films stored at room conditions on the third and fifth days (short‐term loss); on the forty‐fifth and sixtieth days (long‐term loss); and the polymer/clay level of intercalation. All variables and responses were simultaneously calibrated by an ANOVA‐validated (P < 0.05) comprehensive PLS interaction model with a satisfactory R² = 0.956 and Q² = 0.505. A differentiation and discrimination of the mechanisms that control the loss of carvacrol over different periods of time was observed. Short‐term loss seems to be controlled mainly by direct molecular interactions in the interlayer space between carvacrol and the nanoclay organomodifier. Long‐term loss seems to be mainly controlled by diffusion within the nanocomposite matrix once carvacrol has left the nanoclay interlayer space, and it is closely related to the levels of intercalation reached in the nanocomposite. © 2016 Society of Chemical Industry     

Soy protein isolate nanocomposite film enriched with eugenol,an antimicrobial agent: Interactions and properties

Nanocomposites films were designed from soy protein isolates (SPI), clays (Na⁺‐MMT), and eugenol an antimicrobial agent. Interactions between Na⁺‐MMT and eugenol were evidenced by a shift of the d‐spacing by X‐ray diffraction analysis. The addition of Na⁺‐MMT (5 and 7.5% w/w) in SPI solution increased its shear thinning behavior and its consistency. Accordingly, a good exfoliation of clays in SPI films was observed. The glass transition temperature of SPI films was impacted by the clays addition but not the water vapor permeability. In contrast, the addition of eugenol in SPI solution did not affected the consistency but induced a decrease of the SPI film T_g and an increase of the water vapor permeability. The presence of eugenol counterbalanced the effect of clays on consistency of film‐forming solution. The clay intercalation process was facilitated and the water vapor permeability and active agent release were modified. The presence of clay did not affect the antibacterial effect of eugenol/SPI films. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45941.     

Novel Cationic RAFT‐Mediated Polystyrene/Clay Nanocomposites: Synthesis,Characterization, and Thermal Stability

Two novel cationic RAFT agents, PCDBAB and DCTBAB, were anchored onto MMT clay to yield RAFT‐MMT clays. The RAFT‐MMT clays were then dispersed in styrene where thermal self‐initiation polymerization of styrene to give rise to exfoliated PS/clay nanocomposites occurred. The RAFT agents anchored onto the clay layers successfully controlled the polymerization process resulting in controlled molecular masses and narrow polydispersity indices. The nanocomposites prepared showed enhanced thermal stability, which was a function of the clay loading, clay morphology, and slightly on molecular mass.

     

Thermal,mechanical, and barrier properties of polyethylene/surlyn/organoclay nanocomposites blown films prepared by different mixing methods

(Low‐density polyethylene) (LDPE)/clay nanocomposites were prepared by melt blending in a twin‐screw extruder by using different mixing methods. Zinc‐neutralized carboxylate ionomer was used as a compatibilizer. Blown films of the nanocomposites were then prepared. The effect of mixing method on the clay dispersion and properties of the nanocomposites was evaluated by wide‐angle X‐ray diffraction analysis, mechanical properties, thermal properties, and barrier properties. The structure and properties of nanocomposites containing different amounts of nanoclay prepared by selected mixing techniques were also investigated. It was found that melt compounding of Surlyn/clay masterbatch with pure LDPE and Surlyn (two‐step‐a method) results in better dispersion and intercalation of the nanofillers than melt mixing of LDPE/Surlyn/clay masterbatch with pure LDPE and surlyn (two‐step‐b method) and direct mixing of LDPE with clay. The films containing ionomer have good barrier properties. A wide‐angle X‐ray diffraction pattern indicates that intercalation of polymer chains into the clay galleries decreases by increasing the clay content. Barrier properties and tensile modulus of the films were improved by increasing the clay content. In addition, tensile strength increased in the machine direction, but it decreased in the transverse direction by increasing the clay content. DSC results showed that increasing the clay content does not show significant change in the melting and crystallization temperatures. The results of thermogravimetric analysis showed that the thermal stability of the nanocomposites decreased by increasing the clay content more than 1 wt%. J. VINYL ADDIT. TECHNOL., 21:60–69, 2015. © 2014 Society of Plastics Engineers     

Chitosan/clay nanocomposite film preparation and characterization

Nanocomposites of chitosan and nanoclays (MMT‐Na⁺ and Cloisite 30B) were prepared by solvent casting. The structural properties, thermal behaviors, and mechanical properties were characterized using X‐ray diffraction (XRD), transmission electron microscopy (TEM), atomic force microscopy, differential scanning calorimetry, thermogravimetry analyses, and an Instron universal testing machine. XRD and TEM results indicated that an exfoliated structure was formed with addition of small amounts of MMT‐Na⁺ to the chitosan matrix. Intercalation along with some exfoliation occurred with up to 5 wt % MMT‐Na⁺. Micro‐scale composite (tactoids) formed when Cloisite 30B was added to the chitosan matrix. Surface roughness increased with addition of a small amount of clay. Tensile strength of a chitosan film was enhanced and elongation‐at‐break decreased with addition of clay into the chitosan matrix. Melt behavior and thermal stability did not change significantly with addition of clays. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 1684–1691, 2006     

Rigid PVC/(layered silicate) nanocomposites produced through a novel melt‐blending approach

On the basis of the fusion behavior of poly(vinyl chloride) (PVC), the influence of compounding route on the properties of PVC/(layered silicate) nanocomposites was studied. Four different compounding addition sequences were examined during the melt compounding of PVC with montmorillonite (MMT) clay, including (a) a direct dry mixing of PVC and nanoclay, (b) an addition of nanoclay at compaction, (c) an addition of nanoclay at the onset of fusion, and (d) an addition of nanoclay at equilibrium torque. Both unmodified sodium montmorillonite (Na⁺‐MMT) and organically modified montmorillonite (Org.‐MMT) clays were used, and the effect of the addition sequence of the clay during compounding on its dispersion in the matrix was evaluated by X‐ray diffraction and transmission electron miscroscopy. The surface color change, dynamic mechanical analysis, and flexural and tensile properties of PVC/clay nanocomposites were also studied. The experimental results indicated that both the extent of property improvement and the dispersion of nanoparticles in PVC/(layered silicate) nanocomposites are strongly influenced by the degree of gelation achieved in PVC compounds during processing. The addition of nanoclay to PVC must be accomplished at the onset of fusion, when PVC particles are reduced in size, in order to produce nanocomposites with better nanodispersion and enhanced mechanical properties. Overall, rigid PVC nanocomposites with unmodified clay (Na⁺‐MMT) were more thermally stable and exhibited better mechanical properties than their counterparts with organically modified clay (Org.‐MMT). J. VINYL ADDIT. TECHNOL., 2009. © 2009 Society of Plastics Engineers     

Physical properties of poly(trimethylene terephthalate)/organoclay nanocomposites obtained via melt compounding and in situ polymerization

Two series of poly(trimethylene terephthalate) (PTT) nanocomposites, containing an organically modified montmorillonite (MMT) clay (1,2‐aminododecanoic acid (ADA)–intercalated MMT) were prepared via melt compounding and in situ polymerization methods using dimethyl terephthalate (DMT) and 1,3‐propanediol (PDO). The effect of different methods of preparation and varying organoclay contents (1−5 wt%) on the structural, morphological, thermal, and mechanical properties were investigated. The results of wide‐angle X‐ray diffraction (WAXD) and transmission electron microscope (TEM) suggested the possible existence of intercalation morphology between ADA‐MMT and the PTT matrix obtained from melt compounding, and mostly exfoliation state from in situ polymerization depending on the amount of organoclay. From DSC studies, in melt compounding case, the addition of ADA‐MMT in PTT increases melt‐crystallization (T_cm) peak temperature by 14−15°C irrespective of the clay content. However, the melting temperature (T_m) of pristine PTT remains unchanged with increasing clay content. In the case of in situ polymerization, the T_cm and T_m peaks are shifted towards lower temperature with increasing clay content. Dynamic mechanical thermal analysis (DMTA) studies on melt compounded samples revealed a marginal lowering of glass transition temperature (T_g) irrespective of clay content, and a noticeable decrease in T_g with increasing clay content for in situ polymerized samples. The PTT/ADA‐MMT nanocomposites via melt compounding showed higher initial modulus and yield stress, and lower strain at break compared with in situ polymerization with increasing clay content. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers     

Preparation and mechanical properties of polypropylene/clay nanocomposites for automotive parts application

Nanocomposites of polypropylene with organically modified clays were compounded in a twin‐screw extruder by a two‐step melt compounding of three components, i.e., polypropylene, maleic anhydride grafted polypropylene (PPgMA), and organically modified clay. The effect of PPgMA compatibilizers, including PH‐200, Epolene‐43, Polybond‐3002, and Polybond‐3200, with a wide range of maleic anhydride (MA) content and molecular weight was examined. Nanocomposites' morphologies and mechanical properties such as stiffness, strength, and impact resistance were investigated. X‐ray diffraction patterns showed that the dispersion morphology of clay particles seemed to be determined in the first compounding step and the further exfoliation of clays didn't occur in the second compounding step. As the ratio of PPgMA to clay increased, the clay particles were dispersed more uniformly in the matrix resin. As the dispersibility of clays was enhanced, the reinforcement effect of the clays increased; however, impact resistance decreased. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 427–433, 2005     

Effects of the nature and combinations of solvents in the intercalation of clay with block copolymers on the properties of polymer nanocomposites

Polystyrene (PS) nanocomposites were prepared by the free‐radical polymerization of styrene in the presence of organically modified montmorillonite (MMT) clays. MMT clay was modified with a low‐molecular‐weight and quarternized block copolymer of styrene and 4‐vinylpyridine [poly(styrene‐b‐4‐vinylpyridine) (SVP)] with 36.4 wt % PS and 63.6 wt % poly(4‐vinylpyridine) (P4VP). Special attention was paid to the modification, which was carried out in different compositions of a solvent mixture of tetrahydrofuran (THF) and water. The swelling behavior of the MMT clay was studied by an X‐ray diffraction technique. The diffraction peak shifted to lower 2θ angles for all of the modified clays, which indicated the intercalation of the quarternized SVP copolymer into the MMT layers in different degrees. Higher interlayer distances, which showed a high degree of block copolymer insertion, were obtained for solvent compositions with THF in water. The resultant nanocomposites were characterized by X‐ray diffraction, atomic force microscopy, scanning electron microscopy, thermogravimetric analysis, and dynamic mechanical analysis. The desired exfoliated nanocomposite structure was achieved when the MMT modification was conducted in 50 or 66 wt % THF, whereas the other modifications all resulted in intercalated structures. The resulting exfoliated nanocomposite was found to have better thermal stability and dynamic mechanical performance compared to the others, even with 2% clay loading. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Influence of the structure of the onium iodide salts on the properties of modified montmorillonite

Dialkyl imidazoline, alkyl pyridine and alkyl quinoline containing salts have been synthesized and used as new surfactants for cationic exchange of layered silicates, such as montmorillonite (MMT) in order to evaluate their role in the formation of intercalated MMT clays. The new salts have been characterized by FTIR, ¹H, ¹³C‐NMR spectra. These compounds have been intercalated into the layers of MMT via a solution dispersion technique and the extent of the interlayer space expansion was confirmed by using wide angle X‐ray diffraction and FTIR spectra. Thermogravimetry analysis shows that these salts can be used in place of ammonium salts to produce organophilic clays with higher thermal stability than commercial alkyl ammonium‐treated MMT. Moreover, the results also show that the imidazolium‐modified clays have a greater thermal stability compared to the quinolinium and the pyridinium‐modified clay. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Natural rubber/cis‐1,4‐polybutadiene nanocomposites: Vulcanization behavior,mechanical properties,and thermal stability

Natural rubber/cis‐1,4‐polybutadiene (NR/BR) blends with two types of layered nanofillers, montmorillonite (MMT) and layered double hydroxide (LDH), both in pristine and organically modified forms are produced and investigated. Faster curing is found for all the NR/BR blends, except for the one containing the unmodified MMT. This effect can be attributed to the groups placed in the interlayer regions of the clays; more precisely to ammonium groups for the organo‐MMTs and to ? OH groups for LDHs. Mechanical properties and thermal stability of rubber compounds are investigated. It has been demonstrated that the performance of the final nanocomposite is significantly affected by the kind of clay. Particularly, the organo‐MMTs provoke an improvement of the mechanical properties and increase the thermal stability of about 4–5° C in respect to the pure NR/BR matrix. On the contrary, the poor compatibility of unmodified MMT and of LDH clays with the rubber blend is evident and no enhancement on the composite performance has been observed. POLYM. ENG. SCI., 2013. © Society of Plastics Engineers     

Effects of cationic and anionic clays on the hydrolytic degradation of polylactides

Polylactide (PLA)/montmorillonite (MMT) cationic clay and PLA/hydrotalcite (HT) anionic clay composites at 5wt% clay were melt compounded and characterized for morphology before and after hydrolytic degradation. Semicrystalline and amorphous polymers were used as well as noncalcined and calcined clays. The addition of cationic clays led to the formation of microcomposites, whereas the addition of anionic clays produced a much finer dispersion and enhanced polymer intercalation corresponding to that found in nanocomposites. Hydrolytic degradation rate constants of cationic microcomposites and, particularly, of anionic nanocomposites are lower than those of the unfilled polymers, possibly due to the reduction of the carboxylic group catalytic effect through neutralization with the hydrophilic alkaline filler. Comparison of calcined MMT and HT clays vs. their noncalcined counterparts suggest that calcination can further reduce hydrolytic degradation rates, particularly for semicrystalline PLA. Based on the calculated activation energies, the degradation kinetics did not differ significantly above and below the assumed T_g of 58–60°C. The results of this work would be applicable to controlled release pharmaceutical formulations containing clay/drug combinations produced by melt compounding with a biodegradable polymer matrix. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers     

Thermally stable low‐density polyethylene/polyhydroxybutyrate pairs: Synergy between organomodified nanoclay and LDPE‐g‐MAH

Nanocomposites of low‐density polyethylene/polyhydroxybutyrate (LDPE/PHB) containing organomodified montmorillonite (OMMT) and/or LDPE grafted maleic anhydride (LDPE‐g‐MAH) were prepared with a wide range of composition ratios using a vertical co‐rotating twin‐screw microCompounder. To infer the effect of OMMT and LDPE‐g‐MAH on the thermal stability of prepared nanocomposites, all samples were characterized by thermogravimetric analysis while changing clay and compatibilizer contents. Accordingly, two commonly used kinetic models (Coats–Redfern and Horowitz–Metzger) were employed to correlate the thermal stability of the samples with kinetic parameters, including activation energy and pre‐exponential factor. Furthermore, morphological features of LDPE/PHB in the presence or absence of OMMT and LDPE‐g‐MAH were studied using scanning electron microscopy, transmission electron microscopy, and wide‐angle X‐ray diffraction analysis. It was found that for a specific OMMT composition ratio (1 wt %), the thermal stability is enhanced due to an exfoliated structure. However, for samples containing more organoclay (>=3 wt %), the thermal stability was reduced showing the competition between the barrier effect of organoclay platelets and the catalyzing effect of ammonium salts. Moreover, when using LDPE‐g‐MAH as compatibilizer, it acted as a good coupling agent in all compositions in LDPE major phase systems in contrast to PHB major phase samples. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45922.     

Novel LDPE/vermiculite/ciclopiroxolamine hybrid nanocomposites: Structure,surface properties,and antifungal activity

The increasing number of indwelling medical materials and devices are connected with infections caused by yeast, especially Candida albicans. This pathogen produces biofilms on synthetic materials, which facilitates adhesion of the organisms to devices and renders them relatively refractory to medical therapy. Since antimicrobial polymer nanocomposites present one of the promising possibilities, this study explores a new approach to achieving this goal by developing nanocomposite based on low density polyethylene (LDPE) with clay mineral vermiculite as an active carrier for antifungal compound. The set of LDPE/clay nanocomposite with increasing amount of antifungal nanofiller was prepared by melt compounding procedure. As antifungal agent was selected generally used active substance ciclopiroxolamine and this compound was loaded into natural vermiculite through ultrasound technique. The structure of all prepared samples was studied by X-ray diffraction analysis and Fourier transforms infrared spectroscopy. Further thermal properties of polyethylene/clay nanocomposites were investigated by thermogravimetric analysis and the surface properties were evaluated by light optical microscopy, scanning electron microscopy and atomic force microscopy. From mentioned characteristics, we conclude that presence of nanofiller in LDPE primarily causes shift of thermal degradation to higher temperatures and increasing of microhardness. All prepared LDPE nanocomposites possess an excellent and prolonged antifungal activity against Candida albicans.