The TiO2–Clay-LDPE Nanocomposite Packaging Films: Investigation on the Structure and Physicomechanical Properties

The role of nanoclays and TiO₂ nanoparticle loadings were investigated on low density polyethylene crystalline structure, in addition to studying packaging film properties such as barrier, thermal and mechanical properties. The polymer crystal study indicated for the orthorhombic crystal phase and about 20% lower degree of crystallinity for nanocomposites containing more than 2 wt.% TiO₂ nanoparticles. Based on the X-ray diffraction technique, the dispersion of nanoclays was improved to almost good degree of clay exfoliation with the company of 4 wt.% TiO₂ nanoparticles. In agreement with XRD results, the TEM morphological studies mainly suggest that TiO₂ has a helpful effect on nanoclay exfoliation. The increase in degradation temperature of nanocomposites may be attributed to the formation of inorganic char on polymer melt. The barrier properties of TiO₂/clay nanocomposite packaging films depend mainly on nanoclay loading with an unclear trend from TiO₂ nanoparticles. The increase in elastic modulus and the yield stress of nanocomposite films showed great effects on film mechanical properties by nanoclays.     

Mechanical Properties of Rigid Foam PVC-Clay Nanocomposites

The objective of this work is to investigate the effect of using different types of nanoclay fillers on the mechanical properties of rigid PVC foam. Four different types of commercially available nanoclays were used: Natural Calcium Montmorillonite (unmodified), Sodium Montmorillonite modified with a quaternary ammonium salt, Aluminum Magnesium Silicate clay, and Magnesium Lithium Silicate clay. The individual and combined effect of nanoclay concentration and blowing agent content in the polymer melt on the mechanical properties of the rigid foam is reported. Specific compressive strength, specific flexural modulus, and density were found to improve by introducing nanoclay in the polymer matrix. Whereas, tensile strength and modulus of elasticity showed some deterioration with the presence of nanoclay in the rigid PVC foam. On the other hand, impact strength and specific flexural strength did not show any significant changes.     

Mechanical and thermal properties of polypropylene nanocomposites using organically modified Indian bentonite

We report preparation and characterization of nanoclay from Indian bentonite and imported nanoclays, and their compounding with polypropylene (PP) and maleic anhydride‐grafted PP (MA‐g‐PP) in twin screw extruder. The compounded polymer/nanoclay nanocomposites (PNCs) are molded into a standard specimen for studying its tensile, flexural and impact strength. A wide angle X‐ray diffraction (WAXD) and transmission electron microscopy (TEM) study demonstrates intercalation of PP in nanoclays rather than exfoliation for both, indigenous and imported nanoclays. The tensile modulus increased by 41 and 39% for PNC1 (PNC with imported nanoclay) and PNC2 (PNC with indigenous nanoclay) with respect to PP. The flexural modulus for PNC1 and PNC2 also increases by 23 and 22% due to incorporation of 5% nanoclay in PP along with 5% MA‐g‐PP. POLYM. COMPOS., 2010. © 2009 Society of Plastics Engineers     

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     

Exfoliation and dispersion enhancement in polypropylene nanocomposites by in‐situ melt phase ultrasonication

A novel process using ultrasonics to enhance the exfoliation and dispersion of clay platelets in polypropylene‐based nanocomposites has been proposed and investigated. The materials studied were isotactic polypropylene of various molecular weights reinforced with organophilic montmorillonite clay (nanoclay) at 4–6 wt% loadings. X‐ray diffraction (XRD) and rheological measurements, on a model system of nanoclay in mineral oil, were first used to determine ultrasonic energy requirements. The effectiveness of the proposed ultrasonic processing technique on polypropylene nanocomposites was evaluated by XRD and transmission electron microscopy (TEM). The effects of added maleic anhydride–grafted polypropylene compatibilizer, polypropylene molecular weight, and pretreatment of the nanoclays on the nanocomposite exfoliation were also investigated. Results indicate that ultrasonic processing of polymer nanocomposites in the melt state is an effective method for improving exfoliation and dispersion of nanoclays. Issues regarding molecular weight degradation, optimization, mechanical properties, and continuous processing are beyond the scope of the present study and are currently being investigated in our laboratory. Polym. Eng. Sci. 44:1773–1782, 2004. © 2004 Society of Plastics Engineers.     

Contribution of nanoclays to the performance of traditional flame retardants in ABS

The purpose of this study was to investigate contribution of nanoclays to the flame retardancy performance of a traditional brominated flame retardant compound with various combinations of antimony trioxide and zinc borate. The matrix polymer acrylonitrile butadiene styrene (ABS) was compounded by melt mixing in a laboratory size twin‐screw extruder. X‐ray diffraction analysis and transmission electron microscopy revealed that nanoclay silicate layers were mainly intercalated with certain level of exfoliation in ABS matrix. Flammability analysis investigated by mass loss calorimeter, limiting oxygen index, and UL‐94 tests indicated that use of nanoclays improved all flame retardancy parameters significantly. For instance, the increase in the limiting oxygen index was up to 32% O₂, while the suppression in peak heat release rate value was as much as 82%, of course in each specimen the highest rating of V‐0 in UL‐94 test was obtained. Thermogravimetric and other residue analyses pointed out that these contributions were especially due to the condensed phase flame retardancy mechanism of nanoclay which contributes stronger and carbonaceous char formation acting as a barrier to heat and flammable gases and retarding volatilization via tortuous pathway. POLYM. COMPOS., 2012. © 2012 Society of Plastics Engineers     

Synergistic effect of aluminum hydroxide and nanoclay on flame retardancy and mechanical properties of EPDM composites

The composites based on ethylene–propylene–diene monomer rubber (EPDM) with aluminum hydroxide (ATH), nanoclay, vulcanizing agent, and curing accelerator were prepared by conventional mill compounding method. The thermal stability and the flame retardant properties were evaluated by thermogravimetric analysis (TGA), limiting oxygen index (LOI), UL‐94 test, cone calorimeter, and smoke density chamber tests. The results indicated that the substitution of the nanoclay in the EPDM/ATH composites increased the 50% weight loss temperature and the LOI value, and reduced the peak heat release rate (pk‐HRR), the extinction coefficient (Ext Coef), the maximal smoke density (Dm), and the whole smoke at the first 4 min (VOF4) of the test specimens. The synergistic flame retardancy of the nanoclay with ATH in EPDM matrix could imply that the formation of a reinforced char/nanoclay layer during combustion prevents the diffusion of the oxygen and the decomposed organic volatiles in the flame. The mechanical properties of the composites have been increased by replacing more of the nanoclays into the EPDM/ATH blends. The best loading of the nanoclay in EPDM/ATH composites is 3 wt %, which keeps LOI in the enough value, the V‐0 rating in the UL‐94 test, and the improved mechanical properties with better dispersion and exfoliation of the nanoclays shown by transmission electron microscopy (TEM) micrographs. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 2042–2048, 2013     

Starch esters with improved mechanical properties through melt compounding with nanoclays

Biobased nanocomposites were manufactured through the melt intercalation of nanoclays and starch esters synthesized at the Fraunhofer Institute for Applied Polymer Research (IAP) from high amylose starch. Starch acetates (SAs) and starch propionates (SPs) were tested in combination with glycerol triacetate (triacetin) as a plasticizer for concentrations up to 30 and 20 wt %, respectively, with different types of organomodified and unmodified montmorillonites (MMTs). The mechanical properties of injection‐molded test bars were determined by a tensile experiment giving the strength, modulus, and elongation of the composites. X‐ray diffraction (XRD) analysis and transmission electron microscopy (TEM) were used to study clay dispersion and intercalation/exfoliation. Dynamic mechanical analysis was used to track the temperature dependence of the storage modulus and tan δ behavior of the starch/clay hybrid. Because they were the best performing compositions, SP with 5 wt % plasticizer and SA with 20 wt % plasticizer were filled with 5 wt % nanoclay. For SP, a certain increase in modulus was observed for all clays. However, the strength was practically unchanged, and the elongation decreased in most cases. One exception was found for the 2.5 wt % organomodified clay composition, where the elongation increased. For SA, the addition of 5 wt % nanoclay always increased the strength and modulus, in one case up to 60 and 75%, respectively. In the particular case with 5 wt % unmodified clay, the strength, modulus, and elongation increased by 30, 40, and 1000%, respectively. This was a dramatic improvement in the ductility of the material without losses in the strength and stiffness. XRD and TEM revealed the existence of exfoliated modified clay throughout the starch matrix, whereas for the unmodified case (with the exceptional increase in the elongation), no intercalation was observed. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Polyurethane adhesives containing functionalized nanoclays

The development and commercialization of nanoclays (NCs) offers new possibilities to tailor adhesives on the nanoscale range. Three types of functionalized nanoclays were included in the current study, two novel ones and one commercial nanoclay. The novel ones were based on aminosilane and amidoamine hyperbranched polymer, and the commercial nanoclay possessed hydroxyl functionality. All the three functionalities were expected to react with the polyurethane (PU) based thermoset adhesive. Fourier transform infrared (FT-IR) spectroscopy was used to follow the disappearance of the isocyanate group of the polyurethane thermoset adhesive. Thermo-mechanical properties were studied using dynamic mechanical analysis (DMA). Shear and peel properties of adhesively-bonded joints were evaluated using the appropriate test standards. Atomic force microscopy (AFM) was used to analyze the nanoscale morphology of cryogenically fractured surfaces. DMA measurements indicated that the glass transition temperature (T _g) of neat PU was 32°C. Incorporation of nanoclays in concentrations of 1, 3 and 5 wt% affected the glass transition temperature significantly. The functionalized nanoclays increased the T _g gradually to the range of 60 to 62°C for 5 wt% loading. The incorporation of functionalized nanoclays into PU improved the shear strength by 170, 160 and 195% for the hydroxyl-, aminosilane- and hyperbranched-treated NCs, respectively. The functionalized nanoclays exhibited higher peel strength compared to the neat PU by 30% for the hydroxyl modified clay and by 40% for aminosilane-modified clay (at 1 wt% concentration) and almost no change for the hyperbranched modified one. AFM analysis indicated that different fracture mechanisms occurred with respect to the type and concentration of nanoclay used.     

Biodegradable PBAT/Starch Nanocomposites

Starch-based biodegradable banocomposites of poly(butylene adipate-co-terephthalate) [PBAT] and organically modified nanoclays were prepared using melt intercalation technique in Haake Torque Rheocord 9000. Two different organically modified nanoclays Cloisite C20A and Cloisite C30B at various wt% (1, 3, 5) have been used for fabrication of nanocomposites. Starch was gelatinized to prepare thermoplastic starch (TPS) for increasing the compatibility with the PBAT matrix. Subsequently, films of PBAT/TPS blends at various TPS contents (10, 20, 30, 40) wt% and PBAT/TPS Organoclay biodegradable blend nanocomposites at different wt% of nanoclays were prepared using solvent casting method. The interfacial region between the biodegradable polymer matrix and the clays were also modified with grafting of Maleic anhydride (MA) with PBAT chains, during melt blending through two stage reactive extrusion process. Mechanical tests revealed an increase in tensile modulus and elongation at break with the incorporation of 30 wt% TPS and C30B nanoclay to the tune of 44.45% and 776.9% as compared with PBAT matrix. PBAT/TPS30 wt%/C30B3wt% shows maximum tensile modulus and elongation at break due to intercalation of silicate layers resulting from similarity in the surface polarity and interactions of C30B with TPS. Morphology of PBAT/TPS30%/C30B3% biodegradable blend nanocomposite studied using WAXD and SEM indicated intercalation and improved dispersion of TPS within PBAT with incorporation of C30B. Dynamical mechanical analysis of PBAT/TPS/C30B biodegradable blend nanocomposite revealed an increase of storage modulus and glass transition temperatures of PBAT with addition of nanoclays. Further Biodegradation test also confirmed higher biodegradability of PBAT in presence of TPS and C30B.     

Polyolefin nanocomposites: Formulation and development

The preparation of nanoclay‐reinforced polypropylene nanocom posites by means of melt processing was investigated. In order to optimize the dispersion of the nanoclay and the nanoclay‐matrix interface, experiments were performed with three different nanoclays, two different maleic‐anhydride–grafted PP coupling agents, and two different mixing procedures. The physicochemical and mechanical properties of the prepared samples were characterized by means of various techniques. The coupling agents increase the degree of clay intercalation and exfoliation, the latter resulting in part from a “peeling off” mechanism. Significant improvements in tensile and flexural strength and modulus are obtained with Cloisite® 15A nanoclay and a coupling agent characterized by high molecular weight and low grafting content, and these improvements are also accompanied by an increase in Izod impact strength. Little difference was observed between the two mixing procedures used. The improvements were not as pronounced when the coupling agent was characterized by low molecular weight and high grafting content, or when Cloisite® 30B nanoclay was used. In the latter case, there was evidence of greater thermal instability than for Cloisite® 15A. Polym. Eng. Sci. 44:1212–1219, 2004. © 2004 Society of Plastics Engineers.     

Research Progress on Properties and Applications of Polymer/Clay Nanocomposite

This review covers significant properties and applications of nanoclays in polymer-based nanocomposites with special emphasis on future potential. Various strategies have been adopted for nanocomposite synthesis including delamination of nanoclays through melt shearing, in situ polymerization, and sol–gel method. Proper dispersion of nanoclay results in improved properties of bulk polymer (thermal stability, mechanical strength, gas barrier, and flame retardancy). Light weight, low cost, and improved physical properties of polymer/clay materials increase their demand in modern material industries (aerospace, automobile, barrier materials, construction, and biomedical). Due to extensive use of these nanocomposites in technical fields, there are still many stones left unturned.     

Study on the structure and properties of nanocomposites based on high-density polyethylene/starch blends

The effects of nanoclay on the structure and final properties of high density polyethylene (HDPE)/thermoplastic starch (TPS) blends were investigated. Neat blends as well as nanoclay containing samples were prepared by melt blending in an internal mixer. Also, a poly (ethylene-g-maleic anhydride) (PE-g-MA) copolymer was used as compatibilizer in some of the formulations. Nanocomposites with intercalated structures were obtained in the samples lacking the compatibilizer, based on the rheological, X-ray diffraction (XRD) and transmission electron microscopy (TEM) results. However, some of the silicate layers were nearly exfoliated in the presence of the compatibilizer. The nanoclay was located preferably in the HDPE matrix as well as at the interface of the HDPE matrix and TPS dispersed phase. The ability of the nanoclays in decreasing the average size of TPS phase in the HDPE matrix was confirmed by scanning electron microscopy (SEM) observations. Furthermore, thermo-gravimetric analysis (TGA) showed that the nanoclays could enhance the thermal stability of the samples. It seems that nanoclays performed as an insulator and mass transport barrier to the small molecules generated during decomposition, and assisted in the formation of char after thermal decomposition of the polymer matrix. All the samples containing the compatibilizer possessed higher tensile strength and elongation at break, but lower modulus, compared to the corresponding un-compatibilized samples. Finally, incorporation of the nanoclays was found to be in favor of developing nanocomposites with higher biodegradability as evidenced through a biodegradation test by fungi as well as water uptake experiments.     

Compatibilization Mechanism of Nanoclay in Immiscible PS/PMMA Blend Using Unmodified Nanoclay

Organically modified nanoclays have been reported to play the role of a compatibilizer for immiscible polymer blends. However, the mechanism of compatibilization by nanoclay has been reported differently. In this work, we investigated the exact mechanism of compatibilization of nanoclay in immiscible polystyrene (PS)/poly(methyl methacrylate) (PMMA) blend in the presence of sodium-montmorillonite (Na-MMT) through selective dispersion of clay in the matrix phase. Through a detailed investigation of the morphology of PS/PMMA/Na-MMT blend nanocomposites, the plausible mechanism behind the compatibilization effect of clay in immiscible blends has been proposed.     

Polypropylene–clay micro/nanocomposites as fused deposition modeling filament: effect of polypropylene-g-maleic anhydride and organo-nanoclay as chemical and physical compatibilizers

Amongst various polymers used as fused deposition modeling filaments, polypropylene is one which undergoes rigorous shrinkage during printing. This is a drawback for 3D-printer process and related applications, and to overcome this hurdle, mostly, mineral fillers are utilized; however, this additive reduces mechanical properties. To enhance mechanical and shrinkage properties, unmodified clay sheets extracted from bentonite mineral were used as a reinforcing agent, polypropylene grafted maleic anhydride (PP-g-MA) and nanoclay were used as compatibilizers. The compounding was carried out by a twin-screw extruder rather than a single-screw extruder to procure filaments. Afterwards, with fused deposition modeling, dumb-bells and disks were produced for testing. Scanning electron microscopy was employed to examine the morphological feature and dispersion of nanoclay and montmorillonite in the composites. X-ray diffraction was also used to study the dispersion of the nanoclays. The composite disks and dumb-bells were fabricated with a 3D printer to evaluate their rheological properties. Our results showed that the complex viscosity decreased drastically due to aligning the polymer chains along the clay sheets. Mechanical property measurements revealed that the tensile modulus was improved by 60% compared to that of the PP.

     

Influence of Nanoclay Localization on Structure–Property Relationships of Polylactide‐Based Biodegradable Blend Nanocomposites

This article highlights the recent research achievements regarding the development of nanoclay‐containing biodegradable composites of polylactide (PLA)‐based immiscible blends. The structure–property relationships of particular blends, namely, PLA/poly(ε‐caprolactone), PLA/poly(butylene succinate), and PLA/poly[(butylene succinate)‐adipate], are studied with respect to the nanoclay incorporations. For different nanoclay types and concentrations, the morphologies of these nanocomposites are probed and correlated to their viscoelastic, mechanical, and thermal properties, along with their crystallization behavior and kinetics and gas permeability. The nanoclay dispersion and distribution characteristics are found to be key parameters influencing the final properties. In particular, nanocomposites with a higher degree of nanoclay dispersion exhibit significant enhancement in their mechanical, thermal, and barrier properties, and some agglomerations are effective as regards favorable crystallization behavior. In terms of the clay localization, the positioning of nanoclays at the interface reduces the minor phase size remarkably, because of the droplet encapsulation that counteracts coalescence. However, for improved understanding of the influence of nanoclay localization on the structure–property relationships of these blends, further systematic study is required. That is, nanocomposites with different localizations but the same nanoclay loads should be compared. This can be achieved by tuning the processing protocols and the nanoclay inclusion orders in the blends.     

Development of an epoxy based intumescent system comprising of nanoclays blended with appropriate formulating agents

A novel intumescent coating technology for metallic surfaces was developed using functionalized clays, which were intercalated and exfoliated into nanodimensions. The nanoclays were formulated in epoxy resins and blended with appropriate additives to design intumescent coatings for metallic surfaces. With the high dispersion of nanoclay the flame retardancy is improved. The extent and the homogeneity of the exfoliation and dispersion of the clay particles were assessed employing small-amplitude oscillatory shear. The performance and properties of the coatings were evaluated by means of fire resistance testing, thermo-gravimetric analysis and mechanical properties. The incorporation of the nanoclays significantly increased the elasticity and the viscosity of the intumescent formulations and improved the fire resistance of the epoxy coatings. It is observed that significant gains in flame retarding properties could be achieved when the clay platelets could be adequately exfoliated and dispersed.     

Structure–properties relationships in clay nanocomposites based on PVDF/(ethylene–vinyl acetate) copolymer blends

The relationships between the microscopic structure and the macroscopic properties in two sets of clay nanocomposites based on polymer blends comprised of poly(vinylidene fluoride) (PVDF) and ethylene–vinyl acetate copolymer (EVAc) were examined. In nanocomposites based on a polymer blend matrix with high content of polar groups (VAc) the dispersion of polar nanoclay leads to significant enhancement in toughness and a substantial increase in viscosity. However, in nanocomposite blends based on a less polar matrix (i.e. with fewer VAc groups) it is the hydrophobic organoclay that leads to higher modulus and stronger viscoelasticity. The dispersion of nanoparticles and the mechanical response are discussed in terms of emulsifying efficiency of the clay particles in the immiscible polymer blend, an effect that largely depends on the localized interactions between the polymer groups and the clay surface modifier. The potential of nanoclays to serve as matrix sensitive structure-directing agents in tailor-made materials is demonstrated.     

Mechanical properties and drug release rate of poly(vinyl alcohol)/poly(ethylene glycol)/clay nanocomposite hydrogels: Correlation with structure and physical properties

Poly(vinyl alcohol)/poly(ethylene glycol) hydrogels containing curcumin as a drug and the various amounts of a montmorillonite nanoclay are prepared using the freezing–thawing method. Nanoclay quantity influence on the physicomechanical properties and the drug release rate of the hydrogel as well as relationship between them is investigated. X-Ray diffraction and Atomic force microscopy analysis reveal the nanoclays have an intercalation structure in the hydrogel, and the hydrogel crystallization decreases with increasing the nanoclay inclusion. From the SEM micrographs observation, it was revealed that due to the presence of the nanoclay in the hydrogel, its porosity decreased. The naonoclay has an amount-depended dual effect on the hydrogel swelling. The swelling mechanism is a normal Fickian diffusion for all the hydrogel samples. Strong physical interactions between the nanoclays and the polymer chains in the nanocomposite hydrogels are evidenced by the rheological studies. These interactions lead to significant reinforcement of the hydrogel tensile strength, intensified by the nanoclay amount. Interestingly, the nanoclays show the capability of accelerating and, also, decelerating the drug release of the hydrogel. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47843.     

Physicomechanical and antimicrobial characteristics of hydrogel based on poly(vinyl alcohol): Performance improvement via inclusion of chitosan-modified nanoclay

The effect of a chitosan-modified nanoclay (CMNC) on the physical, mechanical, and antimicrobial properties of poly(vinyl alcohol) (PVA) hydrogels prepared by the electron beam irradiation method is reported in comparison with pristine nanoclay (PNC). The X-ray diffraction (XRD) results confirm that the chitosan modification process of nanoclay led to an enhancement in the clay gallery spacing. The inclusion of nanoclays in the PVA matrix decreased the gel content while it increased the swelling degree of the hydrogels. Both PNC and CMNC played a role, depending on their amounts, in swelling of the hydrogel. The swelling kinetic studies revealed a diffusion-controlled swelling process. The diffusion coefficient of water molecules in hydrogels was decreased in the presence of PNC, while it increased with CMNC. Rheological investigations verified the influential role of nanoclays in decreasing the chemical crosslink density of the hydrogel. CMNC exhibited a higher reinforcing effect on hydrogel mechanical properties than PNC did, although the rheological analysis, in agreement with the XRD results, indicated a better dispersion of PNC in the PVA matrix. According to the antimicrobial tests, perfect inhibition of bacteria growth was obtained only for the hydrogels with CMNC. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47444.