Barrier and mechanical properties of injection molded montmorillonite/polyesteramide nanocomposites

Properties of injection‐molded biodegradable polyesteramide composites containing 5 and 13 wt% octadecylammonium‐treated montmorillonite clay have been studied. Oxygen transmission rates and mechanical properties were measured. X‐ray diffraction was used to assess the degree of intercalation of the clay layer stacks, and transmission electron microscopy (TEM) was used to assess the morphology and degree of layer delamination. A substantial reduction in oxygen permeability was observed when clay was added to the composites. The oxygen permeability of the 13 wt% clay sample was only 20% of that of the pure polymer. The in‐plane stiffness and in‐plane strength of the sheets were greatly improved without any embrittlement. These beneficial effects were probably due to the high degree of clay layer exfoliation and orientation observed by TEM. Heat shrinkage, toughness analysis, and cutting operations suggested that the polymer chains and the clay layers were oriented parallel to the plane of the sheet. TEM and X‐ray showed that stacked layers were still present but that these were significantly intercalated. The clay‐layer periodic spacing increased from 25 Å to approximately 35 Å during processing. POLYM. ENG. SCI. 45:135–141, 2005. © 2004 Society of Plastics Engineers     

Structure and melt rheology of long‐chain branching polypropylene/clay nanocomposites

Long‐chain branching polypropylene (LCB‐PP)/clay nanocomposites were prepared by melt blending in a twin‐screw extruder. The microstructure and melt rheology of these nanocomposites were investigated using x‐ray diffraction, transmission electron microscopy, oscillatory shear rheology, and melt elongation testing. The results show that, the clay layers are intercalated by polymer molecular chains and exfoliate well in LCB‐PP matrix in the presence of maleic anhydride grafted PP. Rheological characteristics, such as higher storage modulus at low‐frequency and solid‐like plateau in tan‐ω curve, indicate that a compact and stable filler network structure is formed when clay is loaded at 4 phr (parts per hundred parts of) or higher. The response of the nanocomposite under melt extension reveals an initial decrease in the melt strength and elongational viscosity with increasing clay concentration up to 6 phr. Later, the melt strength and elongational viscosity show slight increases with further increasing clay concentration. These results might be caused by a reduction in the molecular weight of the LCB‐PP matrix and by the intercalation of LCB‐PP molecular chains into the clay layers. Increases in the melt strength and elongational viscosity for the nanocomposites with decreasing extrusion temperature are also observed, which is due to flow‐induced crystallization under lower extrusion temperature. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Morphology and thermal and mechanical properties of phosphonium vermiculite filled poly(ethylene terephthalate) composites

A series of poly(ethylene terephthalate) (PET)/phosphonium vermiculite (P‐VMT) composites were prepared by a melt‐blending method, and we investigated the morphology and thermal and mechanical properties of the composites. We prepared P‐VMT with quaternary phosphonium salts using the common method followed by a cation‐exchange reaction. X‐ray diffraction showed that the phosphonium surfactants were partially intercalated into the vermiculite layers, The d‐spacing of the PET–clay sample was somewhat less than that of the P‐VMT because some degradation of the surfactant took place during melt processing. Compared with PET, the PET–clay composites had a lower decomposition temperature and showed a 17.4% increase in the tensile strength with a P‐VMT content of 3 wt %. Scanning electron microscopy and transmission electron microscopy demonstrated that P‐VMT had a homogeneous dispersion and good compatibility in the polymer matrix with a low content of additive and indicated that the P‐VMT content of 3 wt % was optimal. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Comparison of the influence of different compatibilizers on the structure and properties of ethylene vinyl acetate copolymer/modified clay nanocomposites

Nanocomposites of an ethylene vinyl acetate copolymer and clay were prepared by melt blending and extrusion. Two different compatibilizers, ethylene glycidyl methacrylate (EGMA) and maleic anhydride grafted polypropylene (MAPP), were used in these nanocomposites. The structural properties of the composites were characterized with X‐ray diffraction and transmission electron microscopy. The surface morphology was characterized with polarized optical microscopy. The tensile and permeability properties were studied. The thermal stability of the nanocomposites was characterized through thermogravimetric analysis. MAPP‐compatibilized nanocomposites had intercalated and partially exfoliated structures, whereas EGMA‐compatibilized nanocomposites had completely exfoliated structures. The EGMA‐compatibilized nanocomposites were thermally more stable than the MAPP‐compatibilized nanocomposites. The mechanical and permeability properties of the EGMA‐compatibilized nanocomposites were better than those of the MAPP‐compatibilized nanocomposites. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

Morphologies and properties of nanocomposite films based on a biodegradable poly(ester)urethane elastomer

Biodegradable poly(ester)urethane (PU) elastomer‐based nanocomposite films incorporated with organically modified nanoclay were prepared with melt‐extrusion compounding followed by a casting film process. These films were intended for application as biodegradable food packaging films, with their enhanced gas barrier, mechanical, and thermal properties and good flexibility. From both X‐ray diffraction measurements and transmission electron microscopy observations, the coexistence of intercalated tactoids and exfoliated silicate layers in the compounded PU/clay nanocomposite films was confirmed. In addition, the morphology exhibited a clay dispersion state in the matrix and was influenced by the incorporated nanoclay content. The effects of the nanoclay loading level on the thermal, mechanical, and barrier properties of the compounded nanocomposites were also investigated. As a result, it was revealed that the addition of nanoclay up to a certain level resulted in a remarkable improvement in the thermal properties in terms of thermal stability and the degree of thermal shrinkage; mechanical properties, including dynamic storage modulus and tensile modulus; and oxygen/water‐vapor barrier properties of the nanocomposite films. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Effect of the polymer microstructure on the behavior of syndiotactic polypropylene/organophilic layered silicate composites

Syndiotactic polypropylenes (sPPs) with several microstructures (i.e., syndiotacticities and molecular weights) and synthesized by means of two metallocenic catalysts were melt‐blended with 1 and 3 wt % organophilic layered silicates in the presence of a compatibilizer. X‐ray diffraction and transmission electron microscopy analysis showed that the clay was well dispersed in the composites, although the filler morphology depended on the polymer microstructure. Polypropylenes with low syndiotacticities and molecular weights presented the best clay dispersion. Nonisothermal differential scanning calorimetry analysis showed that the polymer microstructure and the clay content modified the thermal behavior of the composites. The compatibilizer and the clay acted as nucleant agents to increase the crystallization temperature of the matrix. Moreover, the double endothermic peak observed during heating scan and associated with the melt/recrystallization/remelt processes of the pure polymer matrix was reduced in the composites. With regard to the mechanical properties under tensile conditions, a synergic effect of the compatibilizer and the clay was observed. In particular, the addition of the compatibilizer alone was able to increase by about 20% the elastic modulus relative to the neat samples, whereas increases between 35 and 50% were measured when the clay was also added, depending on the polymer microstructure. Our results show that the microstructure of sPPs had strong effects on the behavior of its composites with clay in the presence of a compatibilizer. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

The influence of processing route on the structuring and properties of high‐density polyethylene (HDPE)/clay nanocomposites

The effect of different processing routes on structure and properties of high‐density polyethylene (HDPE)‐clay nanocomposites was assessed. Different compatibilizer/clay ratios (α) were also studied to determine if interactions exist between processing route and polymer‐clay compatibility. HDPE/HDPE‐g‐MA/clay with α values of 1 to 4 were melt compounded (twin screw extrusion), and then processed via three routes: compression moulding, compression moulding followed by biaxial stretching or blown film extrusion. The structure was examined using X‐ray diffraction (XRD) and transmission electron microscopy (TEM). Tensile and oxygen barrier properties were determined. It was found that biaxial extensional forming produced the best enhancement in properties. An interaction between processing route and polymer‐clay compatibility is evident. Halpin‐Tsai (H‐T) model was employed to predict relative modulus values. It showed good agreement with the experimental data. For biaxial extension at α = 4.0, the experimental relative modulus is greater than the predicted value. This may indicate the existence of a “nano” effect at the polymer‐clay interface. POLYM. ENG. SCI., 2012. © 2012 Society of Plastics Engineers     

The effect of organo‐modifier on the structure and properties of poly[ethylene–(vinyl alcohol)]/organo‐modified montmorillonite composites

Ethylene–(vinyl alcohol) (EVOH)/organo‐modified montmorillonite clay (OMMT) composites were prepared using commercial OMMTs with two different organo‐modifiers. The first one has polar groups, which interact with EVOH chains, whereas the second one is non‐polar. Composites with a high weight percentage of OMMT were prepared by melt‐extrusion in a twin‐screw extruder. Films were prepared in a cast‐film line in order to evaluate the tensile and fracture parameters. The morphology of the EVOH/OMMT composites was characterized using wide‐angle X‐ray scattering and transmission electron microscopy, complemented by image analysis. The mechanical properties were evaluated using uniaxial tensile tests; the fracture behaviour was analysed using the essential work of fracture (EWF) method. Results show differences in composite morphologies and crystalline fraction, depending on the content and the nature of the organo‐modifier. The mechanical and fracture behaviours are strongly influenced by those parameters, which act in opposite senses. The EWF method is shown to be a useful tool for the analysis of the structure–properties relationships of these composites. Copyright © 2010 Society of Chemical Industry     

Processing and properties of polymeric nano‐composites

Polymeric nano‐composites are prepared by melt intercalation in this study. Nano‐clay is mixed with either a polymer or a polymer blend by twin‐screw extrusion. The clay‐spacing in the composites is measured by X‐ray diffraction (XRD). The morphology of the composites and its development during the extrusion process are observed by scanning electron microscopy (SEM). Melt viscosity and mechanical properties of the composites and the blends are also measured. It is found that the clay spacing in the composites is influenced greatly by the type of polymer used. The addition of the nano‐clay can greatly increase the viscosity of the polymer when there is a strong interaction between the polymer and the nano‐clay. It can also change the morphology and morphology development of nylon 6/PP blends. The mechanical test shows that the presence of 5–10 wt.% nano‐clay largely increases the elastic modulus of the composites and blends, while significantly decreases the impact strength. The water absorption of nylon 6 is decreased with the presence of nano‐clay. The effect of nano‐clay on polymers and polymer blends is also compared with Kaolin clay under the same experimental conditions.     

Morphology and mechanical properties of polypropylene/organoclay nanocomposites

Polypropylene (PP) nanocomposites were prepared by melt intercalation in an intermeshing corotating twin‐screw extruder. The effect of molecular weight of PP‐MA (maleic anhydride‐ modified polypropylene) on clay dispersion and mechanical properties of nanocomposites was investigated. After injection molding, the tensile properties and impact strength were measured. The best overall mechanical properties were found for composites containing PP‐MA having the highest molecular weight. The basal spacing of clay in the composites was measured by X‐ray diffraction (XRD). Nanoscale morphology of the samples was observed by transmission electron microscopy (TEM). The crystallization kinetics was measured by differential scanning calorimetry (DSC) and optical microscopy at a fixed crystallization temperature. Increasing the clay content in PP‐ MA330k/clay, a well‐dispersed two‐component system, caused the impact strength to decrease while the crystallization kinetics and the spherulite size remained almost the same. On the other hand, PP/PP‐MA330k/clay, an intercalated three‐component system containing some dispersed clay as well as the clay tactoids, showed a much smaller size of spherulites and a slight increase in impact strength with increasing the clay content. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 1562–1570, 2002     

Microstructure and properties of poly(ethylene terephthalate)/organoclay nanocomposites prepared by water‐assisted extrusion: Effect of organoclay concentration

Poly(ethylene terephthalate) (PET)/Cloisite 30B (C30B) nanocomposites containing different concentrations of the organoclay were prepared using two different twin‐screw extrusion processes: conventional melt mixing and water‐assisted melt mixing. The reduction of the molecular weight of the PET matrix, caused by hydrolysis during the water‐assisted extrusion, was compensated by subsequent solid‐state polymerization (SSP). X‐ray diffraction, scanning electron microscopy, and transmission electron microscopy analyses showed intercalated/exfoliated morphology in all PET/C30B nanocomposites, with a higher degree of intercalation and delamination for the water‐assisted process. Rheological, thermal, mechanical, and gas barrier properties of the PET nanocomposites were also studied. Enhanced mechanical and barrier properties were obtained in PET‐C30B nanocomposites compared to the neat PET. The nanocomposites exhibited higher tensile modulus and lower oxygen permeability after SSP. The elongation at break was significantly higher for SSP nanocomposites than for nanocomposites processed by conventional melt mixing. POLYM. ENG. SCI., 54:1879–1892, 2014. © 2013 Society of Plastics Engineers     

Effect of alkylammonium salt on the dispersion and properties of Poly(p‐phenylene sulfide)/clay nanocomposites via melt intercalation

To explore the possibility of making poly(p‐phenylene sulfide) (PPS) nanocomposites via melt intercalation and improving the mechanical properties of PPS, in this study we first modified clay (montmorillonite) with alkylammonium salt by cation exchange and then mixed the modified clay together with the PPS matrix by twin‐screw extrusion. Because the PPS/clay composites were made at a high temperature (300°C), thermogravimetric analysis experiments were carried out first to check the thermal stability of the alkylammonium salt treated clay and the obtained composites. Possible degradation of the alkylammonium salt during processing caused a decrease in the interlayer spacing of the clay. Scanning electron microscopy, transmission electron microscopy, and X‐ray diffraction were used to investigate the dispersion of the clay sheet in the matrix. The clay layers were homogeneously dispersed in the PPS matrix with a nanometer scale, and an exfoliated structure was achieved at a low load of clay. The alkylammonium salt modifier enhanced the interaction between the PPS and clay on the one hand, but on the other hand, it also acted as a plasticizer and caused decreases in the glass‐transition temperature and tensile properties. More work is needed to find a modifier and processing conditions by which the modifier can help the dispersion of clay and also be completely degraded after the formation of an exfoliated structure. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 1724–1731, 2006     

Properties of amylopectin/montmorillonite composite films containing a coupling agent

The addition of clay to polymers has the combined effects of enhancing both the strength/stiffness and the barrier properties. This investigation presents a novel approach to further enhance the strength/stiffness of cast plasticized amylopectin (AP)/Na⁺‐montmorillonite clay films using a water‐soluble coupling agent, poly[(isobutylene‐alt‐maleic acid, ammonium salt)‐co‐(isobutylene‐alt‐maleic anhydride)], between the filler and the matrix. The addition of clay increased the strength and stiffness of the film and the addition of 0.4 parts of a coupling agent per 1 part clay further increased these properties. The trends were the same after each treatment, and there were always significant differences in stiffness and strength between the films without clay and with clay with 0.4 parts of the coupling agent. The increase in stiffness/strength in the presence of a small amount of the coupling agent suggested that it had a bridging effect, presumably through strong secondary bonds to the clay and to the matrix. Infrared spectroscopy and moisture swelling experiments indicated that ester bonds were formed between the coupling agent and AP. X‐ray spectroscopy and transmission electron microscopy revealed that the clay‐particle/polymer structure was qualitatively independent of the presence of the coupling agent showing a mixture of intercalated clay stacks and exfoliated platelets. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 4160–4167, 2007     

Thermal and mechanical properties of poly(ethylene terephthalate)/lamellar zirconium phosphate nanocomposites

The preparation of nanocomposites of poly (ethylene terephthalate) (PET) and lamellar zirconium phosphorous compounds by melt extrusion was investigated. Two types of zirconium phosphorous compounds were synthesized by the direct precipitation reaction method: α‐zirconium bis(monohydrogen orthophosphate) monohydrate (ZrP) and organic–inorganic hybrid layered zirconium phenylphosphonate (ZrPP). Composites containing 2 and 5 wt % ZrP and ZrPP were prepared in a twin‐screw extruder and specimens were obtained by injection molding. The extent of dispersion of the layered filler in the composite matrix was investigated by X‐ray diffraction and transmission electron microscopy (TEM). The crystallization and thermal properties were analyzed by differential scanning calorimetry and thermogravimetry, and the mechanical properties were evaluated by tensile tests. Whereas ZrP‐containing composites showe characteristic diffraction peaks at 2θ 11.7° (d = 7.54 Å), indicative of no delamination, ZrPP showed practically no low‐angle diffraction peak at 2θ 5.5° (d = 15.24 Å), indicating loss of the layered order. TEM images of ZrPP particles indicated the formation of an intercalated/partially delaminated nanocomposite. The behavior was attributed to the higher affinity of the polyester with phenyl groups on the platelet surface of ZrPP. In both cases, the addition of the fillers increased the crystallization rate and the modulus. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 3868–3876, 2006     

The effects of clay dispersion on the mechanical,physical, and flame‐retarding properties of wood fiber/polyethylene/clay nanocomposites

In this study, nanosized clay particles were introduced into wood fiber/plastic composites (WPCs) to improve their mechanical properties and flame retardancy, which are especially important in various automotive and construction applications. A high degree of exfoliation for nanoclay in the wood fiber/high density polyethylene (HDPE) composites was successfully achieved with the aid of maleated HDPE (PE‐g‐MAn), through a melt blending masterbatch process. The structures and morphologies of the composites were determined using X‐ray diffraction (XRD) and transmission electron microscopy (TEM), respectively. This article presents the effects of clay content and degree of clay dispersion on the mechanical and physical properties and flame retardancy of wood fiber/HDPE composites that contained a small amount of clay, in the range of 3–5 wt %. We concluded that achieving a higher degree of dispersion for the nanosized clay particles is critical to enhance the mechanical properties and the flame retardancy of WPCs when small amounts of clay are used. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Polystyrene/calcium phosphate nanocomposites: Morphology,mechanical, and dielectric properties

Matrix mediated synthesis of nanoparticles was utilized to prepare calcium phosphate nanoparticles with a size of 10 nm. The particles were characterized by X‐ray diffraction (XRD) and transmission electron microscopy (TEM) techniques. Nanocomposites of polystyrene and nano‐calcium phosphate were prepared by the melt‐mixing technique. The composites were characterized by TEM to assess the dispersion of the nanoparticles. SAXS measurements of the composites and the fit with Beaucage model described the fractal dimensions of the particles. Mechanical properties of the composites significantly improved with the addition of nanofillers. Dielectric behavior of the nanocomposites was measured with respect to the filler content, temperature, and frequency. The dielectric constant increases with increase in temperature and decreases with increase in frequencies. Dielectric constant increased with filler content in all frequencies; however, lower frequencies showed marked effect. α‐Relaxation of the composites from the dissipation factor of the composites showed higher values for the lower frequencies. Electrical conductivity increased with respect to the filler content and volume resistivity showed the reverse trend. The theoretical prediction of the dielectric constant showed close agreement with the experimental value. POLYM. ENG. SCI. 2012. © 2011 Society of Plastics Engineers     

Properties of organo‐clay/natural rubber nanocomposites: Effects of organophilic modifiers

The effect of various modifiers on the structure and properties of clay/natural rubber nanocomposites are investigated with the aim to evaluate the effect of size and structure of the modifier. Nanocomposites are prepared by melt intercalation method. Mechanical properties of the cured rubber containing nanoclay are compared with the reference compound without the filler. No improvement of mechanical properties is observed for small organic cations; however, stress and strain at break of clay/rubber nanocomposites increase with rising number of octyl chains in the interlayer spaces of organo‐clays. Concerning organo‐cations with the same number of carbon atoms, more effective are the modifiers with several shorter carbon chains compared to those with one long chain. The composites exhibit hybrid structure of nanocomposite and microcomposite as revealed by X‐ray powder diffraction (XRD), transmission electron microscopy (TEM), and scanning electron microscopy (SEM). The details of the structure are supported by DMTA and hysteresis measurements. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Mechanical and thermal properties of gamma irradiated ethylene propylene diene monomer rubber/vermiculite clay/maleic anhydride composites

Vermiculite clay (VMT) was first treated with 2 M of hydrochloric acid. The VMT, before and after acid‐treatment, was characterized by X‐ray diffraction (XRD) and transmission electron microscopy. The untreated (VMT) and acid‐treated vermiculite clay DVMT) at different contents (2.5–10 phr) and maleic anhydride (MA) at different contents (3–10 phr) were mixed with ethylene polyethylene diene rubber (EPDM) via direct melt compounding in an internal mixer. The mechanical and thermal properties of gamma irradiated composites were studied. The results indicated that the physical properties of gamma irradiated EPDM/DVMT/MA nanocomposites were greatly improved after loading with either DVMT or MA. The improvement was achieved when the content of DVMT clay was 5 phr, MA 7 phr and irradiation dose at 75 kGy. J. VINYL ADDIT. TECHNOL., 25:E3–E11, 2019. © 2018 Society of Plastics Engineers     

Effects of clay dispersion and content on the rheological,mechanical properties,and flame retardance of HDPE/clay nanocomposites

Full exfoliation of clay/high density polyethylene (HDPE) nanocomposites was successfully achieved with the aid of maleated HDPE (PE‐g‐MAn), by melt blending in a twin‐screw extruder employing a long residence time configuration. The morphology of the composites was determined using wide‐angle X‐ray diffraction and transmission electron microscopy. The effects of clay content and state of clay dispersion on the rheological, tensile properties, and flame retardancy of nanocomposites containing very small amounts of clay, in the range of 0.05–1.0 wt %, were investigated in this study. It was demonstrated that achieving a higher degree of exfoliation for nanosized clay particles is key to enhancing the rheological, mechanical, and flame retarding properties even when small amounts of clay (less than 1%) are used. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

The effect of filler type and content and the manufacturing process on the performance of multifunctional carbon/poly-lactide composites

Two nanosized carbonaceous fillers, vapor grown carbon nanofibers and exfoliated graphite nanoplatelets, were used to prepare poly(lactide acid) composites at various concentrations from 0 up to 20 wt.%. The two fillers were also combined in order to explore possible synergistic actions. Two compounding processes, melt mixing and polymer dissolution, and two forming methods, injection and compression molding, were used to manufacture the composites. The flexural properties, impact strength, storage and loss modulus, Vicat softening temperature, and electrical conductivity of neat matrix and composites were determined as a function of the filler type and content, and of the processing method used. The filler dispersion within the polymer matrix, the presence of agglomerates and the existence of voids were studied using field-emission scanning electron microscopy. It is concluded that compounding by polymer dissolution followed by compression molding leads to composites with the lowest percolation threshold and surface conductivity and highest storage modulus whereas extrusion injection molding results in composites with the highest mechanical properties. The results can be used to engineer biodegradable composites with specific properties for targeted applications.