Gasoline permeation behavior and mechanical properties of polyamide 6/nanoclay,polyamide 6/PE‐g‐maleic anhydride blend,and polyamide 6/PE‐g‐maleic anhydride/clay nanocomposite

In this article, polyamide 6 (PA6)/clay nanocomposites, PA6/polyethylene grafted maleic anhydride (PE‐g‐MA) blends, and PA6/PE‐g‐MA/clay nanocomposites were prepared and their gasoline permeation behavior and some mechanical properties were investigated. In PA6/clay nanocomposites, cloisite 30B was used as nanoparticles, with weight percentages of 1, 3, and 5. The blends of PA6/PE‐g‐MA were prepared with PE‐g‐MA weight percents of 10, 20, and 30. All samples were prepared via melt mixing technique using a twin screw extruder. The results showed that the lowest gasoline permeation occurred when using 3 wt % of nanoclay in PA6/clay nanocomposites, and 10 wt % of PE‐g‐MA in PA6/PE‐g‐MA blends. Therefore, a sample of PA6/PE‐g‐MA/clay nanocomposite containing 3 wt % of nanoclay and 10 wt % of PE‐g‐MA was prepared and its gasoline permeation behavior was investigated. The results showed that the permeation amount of PA6/PE‐g‐MA/nanoclay was 0.41 g m^?2 day^?1, while this value was 0.46 g m^?2 day^?1 for both of PA6/3wt % clay nanocomposite and PA6/10 wt % PE‐g‐MA blend. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40150.     

Rheological,mechanical, optical,and transport properties of blown films of polyamide 6/residual monomer/montmorillonite nanocomposites

Exfoliated nanocomposites of polyamide 6 (PA6) with residual monomer and an organically treated montmorillonite (3 and 5 wt %) were produced by twin‐screw extrusion. The composites had their steady state, dynamic, and transient rheological properties measured by parallel‐plates rheometry; their exfoliation level was characterized by wide angle X‐rays diffraction (WAXD) and transmission electron microscopy (TEM). The characterization showed as follows: (i) the nanoclay's lamellas were well dispersed and distributed thru the PA6, (ii) the postpolymerization of the residual monomer produced more branched chains than linear ones in the pure PA6, (iii) the nanoclay's lamellas acted as entanglement points in the nanocomposites, and (iv) the molecular weight of the PA6 in the nanocomposites decreased. Blown films of the nanocomposites were produced by single screw extrusion; the die pressure during the film blowing of the nanocomposites strongly decreased. The tensile mechanical properties of the blown films were also measured. Along the machine direction (MD), the best mechanical properties were obtained with the 5 wt % nanocomposite, whereas along the transverse direction (TD), the 3 wt % nanocomposite had the best behavior. The glass transition temperature (T_g) of the blown films was measured by dynamic mechanical thermal analyses (DMTA). The 5 wt % nanocomposite had the highest T_g of all the films. The optical properties were measured by spectrophotometry; the nanoclay decreased the films' haze, but the level of transmittance was not affected. The water vapor and oxygen permeability rates of the nanocomposites films were found to be lower than in the pure PA6 blown film as a result of a tortuosity effect. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Effect of uniaxial stretching on thermal,oxygen barrier,and mechanical properties of polyamide 6 and poly(m‐xylene adipamide) nanocomposite films

In this study, the effect of uniaxial stretching on the thermal, oxygen barrier and mechanical properties of aliphatic polyamide 6 (PA6) and aromatic Poly(m‐xylene adipamide) (MXD6) nylon films as well as their in‐situ polymerized nanocomposites with 4 wt% clay were studied. Cast films were prepared by extrusion process and rapidly cooled using an air knife. The precursor films were uniaxially stretched at 110°C with draw ratios varying from 1.5 to 5. DSC results showed that the cold crystallization temperature (T_cc) of the uniaxially stretched MXD6 and MXD6/clay films drastically shifted to the lower temperatures when draw ratio increased. The aromatic nylon films had lower oxygen permeability than those of the aliphatic films, due to more rigidity and chain packing. However, the oxygen permeability of the stretched films increased with draw ratio (DR) up to a critical value for each sample, while further stretching resulted in a reduction in the oxygen permeation. This phenomenon was related to the changes in free volume upon uniaxial stretching. The ability of different geometrical models to describe the experimental relative permeability data was investigated. The Bharadwaj model that took into account clay orientation was the most successful one to predict the oxygen barrier characteristics of the stretched nanocomposites at high draw ratios. The Young's modulus and tensile strength of the aliphatic and aromatic nylons increased with uniaxial deformation, while the flexibility and elongation at break of the former decreased with increasing DR. A larger increase in the Young's modulus of the uniaxially stretched nanocomposite films compared with the neat samples was observed and could be related to the improvement in the clay orientation as well as a better alignment of the crystalline phase due to incorporating the clay platelets in the polymer matrix. In contrast, the flexibility of the stretched MXD6 improved remarkably (ca., 25 times) compared with the precursor film (DR = 1) when the draw ratio increased to 1.5. This could be related to the effect of hot stretching on the enhancement of polymer chains relaxation and mobility at low draw ratios. POLYM. ENG. SCI., 55:1113–1127, 2015. © 2014 Society of Plastics Engineers     

Morphological,rheological and thermal studies in melt processed compatibilized PA6/ABS/clay nanocomposites

Multicomponent compatibilized blends of polyamide 6 (PA6) and styrene-butadiene-acrylonitrile (ABS) with co-continuous morphology are among commercial alloys with an interesting combination of properties. To further enhance the properties different amounts of nanoclay were incorporated into these blends through a one step melt mixing process. The effect of nanoclay addition on rheological, thermal stability, crystallization and morphological properties of the nanocomposites were investigated and compared with those of the neat blends. The nanoscale dispersion of the clay layers in the blends were confirmed through X-ray diffraction and transmission electron microscopy methods. Rheological investigation indicated an increased viscosity and melt elasticity for the nanocomposite systems. The viscosity of nanocomposites followed a shear thinning flow behavior and decreased with increasing shear rates. The changes in the rheological properties were accompanied by refinement of the co-continuous morphology. For thermal degradation under N₂ atmosphere, the onset and maximum of degradation temperatures for the nanocomposites were as high as the neat blends, while significant improvement in thermal stability (about 60 °C by 3 wt% clay addition) was observed in the air environment. In addition agglomerated clay particles did not significantly affect thermal stability of the polymer matrix. Non-isothermal crystallization results indicated that the clay layers had a retarding effect on the crystal growth rate and facilitated the formation of α crystalline form. In addition no nucleation effect was observed during the crystallization process due to incorporation of nanoclay into the blends.     

Effect of clay addition on the morphology and thermal behavior of polyamide 6

The nanostructure, morphology, and thermal properties of polyamide 6 (PA6)/clay nanocomposites were studied with X‐ray scattering, differential scanning calorimetry (DSC), and transmission electron microscopy (TEM). The wide‐angle X‐ray diffraction (WAXD) and TEM results indicate that the nanoclay platelets were exfoliated throughout the PA6 matrix. The crystallization behavior of PA6 was significantly influenced by the addition of clay to the polymer matrix. A clay‐induced crystal transformation from the α phase to the γ phase for PA6 was confirmed by WAXD and DSC; that is, the formation of γ‐form crystals was strongly enhanced by the presence of clay. With various clay concentrations, the degree of crystallinity and crystalline morphology (e.g., spherulite size, lamellar thickness, and long period) of PA6 and the nanocomposites changed dramatically, as evidenced by TEM and small‐angle X‐ray scattering results. The thermal behavior of the nanocomposites was investigated with DSC and compared with that of neat PA6. The possible origins of a new clay‐induced endothermic peak at high temperature are discussed, and a model is proposed to explain the complex melting behavior of the PA6/clay nanocomposites. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 1191–1199, 2007     

Preparation of thermoplastic elastomer nanocomposites based on polyamide‐6/polyepichlorohydrin‐co‐ethylene oxide

This work is aimed at determining the effect of nanoclay and polyepichlorohydrin‐co‐ethylene oxide (ECO) content on the microstructure and mechanical properties of PA6/ECO thermoplastic elastomers (TPEs). TPE nanocomposites were prepared in a laboratory mixer using polyamide 6 (PA6), ECO, and an organoclay by a two‐step melt mixing process. First, the PA6 was melt blended with Cloisite 30B and then mixed by ECO rubber. X‐ray diffraction results and transmission electron microscopy image showed that the nanoclay platelets were nearly exfoliated in both the phases. The SEM photomicrograph of PA6 with ECO showed that the elastomer particles are dispersed throughout the polyamide matrix and the size of rubber particles is less than 3 μm. Introduction of organoclay in the PA6 matrix increased the size of dispersed rubber particles in comparison with the unfilled but otherwise similar blends. The nanoscale dimension of the dispersed clay results in an improvement of the tensile modulus of the nanocomposites. POLYM. ENG. SCI., 2011. © 2010 Society of Plastics Engineers     

Effects of swelling agents on the crystallization behavior and mechanical properties of polyamide 6/clay nanocomposites

Montomorillonite was organically modified with three different swelling agents: n‐dodecylamine, 12‐aminolauric acid, and 1,12‐diaminodecane. These organoclays and polyamide 6 (PA6) were blended in a formic acid solution. X‐ray diffraction analysis showed that the clay still retained its layer structure in the PA6/clay nanocomposite. Consequently, these materials were intercalated nanocomposites. The effects of the swelling agent and organoclay content on the crystallization behavior of the PA6/clay nanocomposites were studied with differential scanning calorimetry. The results showed that the position and width of the exothermic peak of the PA6/clay nanocomposites were changed during the nonisothermal crystallization process. The clay behaved as a nucleating agent and enhanced the crystallization rate of PA6.The crystallinity of PA6 decreased with an increasing clay content. Different swelling agents also affected the crystallization behavior of PA6. The effects of the type and content of the swelling agent on the tensile and flexural properties of PA6/clay nanocomposites were also investigated. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 1686–1693, 2003     

Effect of carbon nanotube on PA6/ECO composites: Morphology development,rheological, and thermal properties

Thermoplastic elastomer (TPE) nanocomposites based on polyamide‐6 (PA6)/poly(epichlorohydrin‐co‐ethylene oxide) (ECO)/multiwall carbon nanotube (MWCNTs) were prepared by melt compounding process. Different weight ratios of ECO (20, 40, and 60 wt %) and two kinds of functionalized and non‐functionalized MWCNTs were employed to fabricate the nanocomposites. The morphological, rheological, and mechanical properties of MWCNTs‐filled PA6/ECO blends were studied. The scanning electron microscopy of PA6/ECO blends showed that the elastomer particles, ECO, are well‐dispersed within the PA6 matrix. The significant improvement in the dispersibility of the carboxylated carbon nanotubes (COOH‐MWCNTs) compared to that of non‐functionalized MWCNTs (non‐MWCNTs) was confirmed by transmission electron microscopy images. The tensile modulus of samples improved with the addition of both types of MWCNTs. However, the effect of COOH‐MWCNTs was much more pronounced in improving mechanical properties of PA6/ECO TPE nanocomposites. Crystallization results demonstrated that the MWCNTs act as a nucleation agent of the crystallization process resulted in increased crystallization temperature (T_c) in nanocomposites. Rheological characterization in the linear viscoelastic region showed that complex viscosity and a non‐terminal storage modulus significantly increased with incorporation of both types of MWCNTs particularly at low frequency region. The increase of rheological properties was more pronounced in the presence of carboxylic (COOH) functional groups, in the other words by addition of COOH‐MWCNTs. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45977.     

The role of crystallinity and reinforcement in the mechanical behavior of polyamide‐6/clay nanocomposites

The mechanical behavior of compression‐molded polyamide‐6 (PA6) reinforced with 2 wt% of organo‐nanoclay (montmorillonite intercalated with ω‐amino dodecanoic acid) has been studied and compared to that of PA6. The tensile strength and the Young's modulus of the PA6/clay were 15% higher than those of PA6. Differential scanning calorimetry, Fourier transform infrared spectroscopy, and X‐ray diffraction showed that the crystalline structures of PA6 and PA6/clay differed considerably. A crystallinity of 25% with a dual structure composed of the γ and α forms was obtained in PA6/clay, while a crystallinity of 31% with the α form as the dominant crystalline structure was obtained in PA6. To understand the role of the crystalline structure of PA6, the molding process was modified to obtain PA6 specimens with different levels of crystallinity and different crystalline forms. Quenching molten PA6 at a cooling rate sufficiently high to prevent crystallization gave a material that was predominantly amorphous (crystallinity of 7%) with traces of the mesomorphic β or γ* form. Annealing this material at 80°C considerably increased crystallinity to 21%, which was also of the mesomorphic β or γ* form. PA6 with a predominant crystalline γ form could not be generated. Comparisons with PA6/clay in terms of crystallinity and mechanical behavior lead to the conclusion that the improvements in rigidity and strength observed when montmorillonite is added to PA6 are related to the reinforcing filler and not to a modification of the crystalline structure.     

Mechanical and thermal properties of toughened PA6/HDPE/SEBS‐g‐MA/Clay nanocomposite

Preparation and morphology of Polyamide 6 (PA6)/high density polyethylene (HDPE)/Styrene/Ethylene–Butylene/Styrene grafted with maleic anhydride (SEBS‐g‐MA)/Modified clay nanocomposites were studied. Mixing was performed using melting process in an extruder co‐rotating twin screw. After etching the materials with boiling toluene and THF at room temperature, the morphology of sample checked by scanning electron microscopy (SEM) analyses. X‐ray diffraction (XRD) used for evaluation of the effects of organo‐clay addition in the structure of nanocomposites. XRD traces showed that the characteristic (001) peak of the nanocomposites shifted to the lower degree region. XRD and SEM results showed more uniformly distribution and dispersion of HDPE in the PA6 matrix. Better sample morphology obtained, regarding less distance, and more uniformity between nanoparticles. The mechanical properties like tensile strength, impact strength, hardness and thermal properties of these toughened nanocomposites are discussed in terms of the nanoclay, SEBS‐g‐MA contents and morphology. Adding nanoclay improved hardness of nanocomposites product but reduced toughness and thermal properties. Meanwhile the presence of SEBS‐g‐MA as a compatibilizer improved toughness, thermal properties, hardness property, and the balance properties are achieved. POLYM. ENG. SCI., 55:29–33, 2015. © 2014 Society of Plastics Engineers     

Morphology and properties of nylon 6 and high density polyethylene blends in presence of nanoclay and PE‐g‐MA

In this study, we report the synergistic effect of nanoclay and maleic anhydride grafted polyethylene (PE‐g‐MA) on the morphology and properties of (80/20 w/w) nylon 6/high density polyethylene (HDPE) blend. Polymer blend nanocomposites containing nanoclay with and without compatibilizer (PE‐g‐MA) were prepared by melt mixing, and their morphologies and structures were examined with scanning electron microscopy (SEM) and wide angle X‐ray diffractometer (WAXD) study. The size of phase‐separated domains decreased considerably with increasing content of nanoclay and PE‐g‐MA. WAXD study and transmission electron microscopy (TEM) revealed the presence of exfoliated clay platelets in nylon 6 matrix, as well as, at the interface of the (80/20 w/w) nylon 6/HDPE blend–clay nanocomposites. Addition of PE‐g‐MA in the blend–clay nanocomposites enhanced the exfoliation of clays in nylon 6 matrix and especially at the interface. Thus, exfoliated clay platelets in nylon 6 matrix effectively restricted the coalescence of dispersed HDPE domains while PE‐g‐MA improved the adhesion between the phases at the interface. The use of compatibilizer and nanoclay in polymer blends may lead to a high performance material which combines the advantages of compatibilized polymer blends and the merits of polymer nanocomposites. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Influence of addition of styrene–ethylene/butylene–styrene copolymer on rheological,mechanical, and tribological properties of polyamide nanocomposites

To develop new tribomaterials for mechanical sliding parts, investigations were carried out on the influence of adding styrene–ethylene/butylene–styrene block copolymer (SEBS) on the rheological, mechanical, and tribological properties of polyamide 6 (PA6) nanocomposite, which is a commercial product of layered silicate (clay) filled polyamide 6 (PA6/Clay). Two kinds of block copolymers, unmodified SEBS (SEBS) and maleic anhydride‐grafted SEBS (SEBS‐g‐MA), were added with PA6/Clay nanocomposite. Dynamic viscoelastic properties in the molten state of these nanocomposites and their tensile, impact, and tribological properties of these nanocomposites were evaluated. Dynamic viscoelastic properties were found to increase with the addition of SEBS and were influenced, in particular, by block copolymers containing SEBS‐g‐MA. Influence of the addition of SEBS on mechanical properties of these systems differed for each mechanical property. Although tensile properties decreased with SEBS, Izod impact properties were improved with the addition of SEBS‐g‐MA. Tribological properties were improved with the addition of block copolymer, and the influence of the amount of addition was higher than the type of block copolymer used. These results indicate that new tribomaterials developed have sufficient balance amongst moldability, mechanical, and tribological properties. POLYM. COMPOS., 2010. © 2009 Society of Plastics Engineers     

Polymer‐Clay Nanocomposites Based on Blends of Polyamide‐6 and Polyethylene

The preparation of polyamide‐6/clay, high‐density polyethylene/clay, and high‐density polyethylene/ polyamide‐6/clay nanocomposites is considered. X‐ray diffraction (XRD), differential scanning calorimetry (DSC), and Fourier Transform Infrared (FTIR) measurements show that the clay enhances the crystallization of the γ‐form of polyamide‐6. The clay also acts as a nucleation agent and causes a reduction of spherulitte size. Scanning electron microscopy (SEM) analysis of fracture surfaces shows that the clay reduces the PA‐6 particle size in the HDPE/PA‐6/clay nanocomposites and changes the morphology. Mechanical properties and the effect of maleated polyethylene are also reported.     

Morphology and melt rheology of nylon 11/clay nanocomposites

Nylon 11 (PA11)/clay nanocomposites have been prepared by melt‐blending, followed by melt‐extrusion through a capillary. Transmission electron microscopy shows that the exfoliated clay morphology is dominant for low nanofiller content, while the intercalated one is prevailing for high filler loading. Melt rheological properties of PA11 nanocomposites have been studied in both linear and nonlinear viscoelastic response regions. In the linear regime, the nanocomposites exhibit much higher storage modulus (G′) and loss modulus (G″) values than neat PA11. The values of G′ and G″ increase steadily with clay loading at low concentrations, while the G′ and G″ for the sample with 5 wt % clay show an inverse dependence and lie between the modulus values of the samples with 1 and 2 wt % of clay. This is attributed to the alignment/orientation of nanoclay platelets in the intercalated nanocomposite induced by capillary extrusion. In the nonlinear regime, the nanocomposites show increased shear viscosities when compared with the neat resin. The dependence of the shear viscosity on clay loading has analogous trend to that of G′ and G″. Finally, a comparison has been made between the complex and steady viscosities to verify the applicability of the empirical Cox‐Merz rule. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 542–549, 2006     

Investigation of thermal degradation and flammability of polyamide‐6 and polyamide‐6 nanocomposites

In this paper, polyamide‐6 and polyamide‐6 nanocomposites were prepared by direct melt intercalation technique. The thermal degradation behavior of both polyamide‐6 and polyamide‐6 clay nanocomposites has been studied. The apparent activation energy of the nanocomposites is almost the same with that of pure polymer under nitrogen, but the apparent activation energy of the nanocomposites is greatly enhanced in air atmosphere. This increasing trend coincides with the thermal analysis and the cone calorimeter results, which may suggest that the polymer/clay nanocomposites have a higher thermal stability and lower flammability. The kinetic analysis also indicates that the pyrolytic degradation and the thermal oxidative degradation of PA6 and PA6/OMT nanocomposites are two kinds of different reaction models. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 2297–2303, 2007     

Effect of clay exfoliation and organic modification on morphological,dynamic mechanical,and thermal behavior of melt‐compounded polyamide‐6 nanocomposites

Polyamide‐6/clay nanocomposites were prepared employing melt bending or compounding technique followed by injection molding using different organically modified clays. X‐ray diffraction and transmission electron microscopy were used to determine the molecular dispersion of the modified clays within the matrix polymer. Mechanical tests revealed an increase in tensile and flexural properties of the matrix polymer with the increase in clay loading from 0 to 5%. C30B/polyamide‐6 nanocomposites exhibited optimum mechanical performance at 5% clay loading. Storage modulus of polyamide‐6 also increased in the nanocomposites, indicating an increase in the stiffness of the matrix polymer with the addition of nanoclays. Furthermore, water absorption studies confirmed comparatively lesser tendency of water uptake in these nanocomposites. HDT of the virgin matrix increased substantially with the addition of organically modified clays. DSC measurements revealed both γ and α transitions in the matrix polymer as well as in the nanocomposites. The crystallization temperature (T_c) exhibited an increase in case of C30B/polyamide‐6 nanocomposites. Thermal stability of virgin polyamide‐6 and the nanocomposites has been investigated employing thermogravimetric analysis. POLYM. COMPOS., 28:153–162, 2007. © 2007 Society of Plastics Engineers     

Interfacial interactions and performance of polyamide 6/modified attapulgite clay nanocomposites

Attapulgite (AT) clay was firstly treated with sodium polyacrylate (PAS), then polyamide 6 (PA6)/AT nanocomposites were prepared by simple melt compounding. Transmission electron microscope (TEM) and Fourier transform infrared spectrometry (FT‐IR) of treated AT confirm the success of purifying and surface modification of the original AT by PAS. X‐ray diffraction spectra for the nanocomposites show that the microstructure of AT in PA6 matrix is almost unchanged. It indicates that a strong interfacial adhesion exists between AT and PA6 matrix through analyzing fracture surfaces of the nanocomposites, the variation of glass transition temperature (T_g) obtained by dynamic mechanical analysis, and interfacial interaction factors; field emission scanning electron microscopy on the fracture surfaces of the nanocomposites shows that a uniform dispersion of AT is obtained. The above two aspects conform to the improvement of mechanical and thermal properties of the nanocomposites. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers     

Morphological and Rheological Properties of Polyamide 6/Poly(propylene)/Organoclay Nanocomposites

Summary: Polyamide 6 (PA6)/Poly(propylene) (PP)/organoclay (octadecylamine intercalated montmorillonite) systems with and without compatibilizer (maleated poly(propylene) and ethylene/propylene‐based rubber (PPgMA and EPRgMA, respectively)) were produced by extrusion melt blending and the clay dispersion was characterized by transmission electron microscopy (TEM) and X‐ray diffraction (XRD). The rheological behaviour of the nanocomposites was determined by various methods, viz melt flow index (MFI), capillary and plate/plate rheological measurements. Attempts were made to trace the rheological parameters that reliably reflect the observed changes in the clay dispersion. It was found that some parameters in the viscoelastic range derived from frequency sweep measurements using a plate/plate rheometer are a suitable indicator for changes in the clay dispersion. High initial viscosity with a strong reduction as a function of frequency was attributed to improved clay exfoliation. The latter was also reflected by a high initial shear storage modulus (G′) along with its small change with the frequency.

Variation of the storage modulus (G′) as a function of frequency for the PA6/PP nanocomposites. Note: this figure also indicates how the slopes at low and high shear rates were determined.     

Structural,rheological, and mechanical properties of PA6/SAN/SEBS ternary blend/organoclay nanocomposites

The aim of this study was to investigate the effect of nanoclay addition on the morphological and mechanical properties of PA6/SAN/SEBS ternary blend. Two different nanoclays with different modifiers and two different mixing sequences were used to investigate the role of thermodynamic and kinetic, respectively, in the nanoclays localization. XRD, SEM, TEM, melt rheology, tensile and Izod impact tests were used to characterize the nanocomposites. Results of characterization of nanocomposites showed that clay localization is a very influential parameter to determine the type of morphology and, consequently, mechanical properties of ternary/clay nanocomposites. It was demonstrated that presence of nanoclay in the matrix results in the increase of stiffness, while localization of nanoclay at the interface improves the toughness and tensile strength. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41969.     

Crystallization and thermal behavior of microcellular injection‐molded polyamide‐6 nanocomposites

This article presents the effects of nanoclay and supercritical nitrogen on the crystallization and thermal behavior of microcellular injection‐molded polyamide‐6 (PA6) nanocomposites with 5 and 7.5 wt% nanoclay. Differential scanning calorimetry (DSC), X‐ray diffractometry (XRD), and polarized optical microscopy (POM) were used to characterize the thermal behavior and crystalline structure. The isothermal and nonisothermal crystallization kinetics of neat resin and its corresponding nanocomposite samples were analyzed using the Avrami and Ozawa equations, respectively. The activation energies determined using the Arrhenius equation for isothermal crystallization and the Kissinger equation for nonisothermal crystallization were comparable. The specimen thickness had a significant influence on the nonisothermal crystallization especially at high scanning rates. Nanocomposites with an optimal amount of nanoclay possessed the highest crystallization rate and a higher level of nucleation activity. The nanoclay increased the magnitude of the activation energy but decreased the overall crystallinity. The dissolved SCF did not alter the crystalline structure significantly. In contrast with conventionally injection‐molded solid counterparts, microcellular neat resin parts and microcellular nanocomposite parts were found to have lower crystallinity in the core and higher crystallinity near the skin. POLYM. ENG. SCI., 46:904–918, 2006. © 2006 Society of Plastics Engineers