Positive‐working aqueous base developable photosensitive polybenzoxazole precursor/organoclay nanocomposites

Positive‐working aqueous base developable photosensitive polybenzoxazole (PBO) precursor/organoclay nanocomposites have been prepared through the addition of an organoclay to a PBO precursor. The organoclay was formed by a cation exchange reaction between a Na⁺‐montmorillonite clay and an ammonium salt of dodecylamine. The PBO precursor used in this study was a polyhydroxyamide that was prepared from a low‐temperature polymerization of 2′2′‐bis(3‐amino‐4‐hydroxyphenyl) hexafluoropropane and 4,4′‐oxydibenzoyl chloride with an inherent viscosity of 0.3 dL/g. The photosensitive resin/clay formulations were prepared from the precursor with 2,3,4‐tris(1‐oxo‐2‐diazonaphthoquinone‐5‐sulfonyloxy)‐benzophenone photosensitive compound and 3–5 wt % organoclay. The PBO precursor/clay was subsequently thermally cured to PBO/clay at 350°C. Both X‐ray diffraction and transmission electron microscope analyses showed that the organoclay was dispersed in the PBO matrix in a nanometer scale. The thermal expansion coefficient of PBO/clay film, which contained 5 wt % organoclay, was decreased 33% compared to the pure PBO film. The PBO/clay nanocomposite films also displayed higher thermal stability, glass transition temperature, and water resistance than the pure PBO film. The photosensitive PBO precursor/clay nanocomposite showed a line/space pattern with a resolution of 5 μm and its sensitivity and contrast were not affected by the organoclay. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 2350–2356, 2005     

Poly(amide‐imide)/organoclay nanocomposites using glycine as a natural amino acid: study on fire and thermal behavior

In the present study, new functional poly(amide‐imide)/organoclay nanocomposite films were successfully fabricated through the solution intercalation technique. New poly(amide‐imide) (PAI) containing glycine was synthesized via solution polycondensation of 1,1',3,3'‐tetraoxo(5,5'‐biisoindoline‐2,2'‐diyl)diacetic acid with 4,4′‐diaminodiphenylsulfone. The synthesized PAI was characterized by ¹H NMR, Fourier transform infrared (FTIR) spectroscopy, gel permeation chromatography, elemental analysis and inherent viscosity. Then, PAI/organoclay nanocomposite films containing 4 and 8 wt% of organoclay were prepared via solution intercalation through blending of organoclay 30B with the PAI solution. The nanostructures and properties of the PAI/organoclay were investigated using FTIR spectroscopy, XRD, transmission electron microscopy (TEM), TGA, DSC and microscale combustion calorimetry. XRD and TEM revealed the good dispersion of organoclay in the polymer matrix. TGA indicated that the addition of organoclay into the PAI matrix increases the thermal decomposition temperatures and char yields of the nanocomposites. Organoclay shows a positive effect in improving the flame retardancy of the PAI, reflecting the decrease in heat release rate, the total heat release and the heat release capacity of the PAI nanocomposites, while the thermal stability of the PAI nanocomposites only increased slightly compared with the neat polymer. © 2013 Society of Chemical Industry     

Thermally Stable Phosphonium Organoclay-Reinforced Polyimide Nanocomposites

To prepare clay containing high-temperature processable polymer nanocomposites, new cation exchangeable agents with high thermal stability are required. In this work, we investigated the effect of a thermally stable phosphonium-modified organoclay on the properties of polyimides prepared from the reaction of 4,4′-oxydianiline with 3,3′,4,4′-benzophenonetetracarboxylic dianhydride. The organoclay was prepared from the reaction of pristine clay with octyltriphenylphosphonium bromide. Phosphonium-modified clay displayed a negligible weight loss (<5%) below 300°C. The thermal stability of the composites enhanced with the increasing amount of phosphonium-modified clay.     

New aramid‐based nanocomposites: Synthesis and characterization

New type of nanocomposites containing various proportions of montmorillonite in aromatic polyamide was prepared via solution intercalation method. Aramid chains were synthesized by reacting 4,4′‐oxydianiline with isophthaloyl chloride in N,N′‐dimethyl acetamide. Dodecylamine was used as swelling agent to change the hydrophilic nature of montmorillonite into organophilic. Appropriate amounts of organoclay were mixed in the polymer solution using high‐speed mixer for complete dispersion of the clay. Thin films cast from these materials after evaporating the solvent were characterized by XRD, TEM, mechanical, thermal, and water absorption measurements. The structure and morphology of the nanocomposites determined by XRD and TEM revealed the formation of exfoliated and intercalated clay platelets in the aramid matrix. Mechanical data indicated improvement in the tensile strength and modulus of the nanocomposites with clay loading up to 6 wt%. The glass transition temperature increased up to 12 wt% clay content and thermal stability amplified with increasing clay loading. The water absorption reduced gradually as a function of organoclay and approached to zero with 20 wt% organoclay in the aramid. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers     

Synthesis and properties of polyimide (containing naphthalene) nanocomposites with organo‐modified montmorillonites

2,7‐Bis(4‐aminophenoxy) naphthalene (BAPN), a naphthalene‐containing diamine, was synthesized and polymerized with a 3,3′,4,4′‐benzophenone tetracarboxylic dianhydride (BTDA) to obtain a polyimide (PI) via thermal imidization. To enhance the thermal and mechanical properties of the polymer, PI–Montmorillonite (MMT) nanocomposites were prepared from a DMAc solution of poly(amic acid) and a DMAc dispersion of MMT, which were organo‐modified with various amounts of n‐dodecylamine (DOA) or cetylpyridium chloride (CPC). FTIR, XRD, and TEM (transmission electron microscopy) were used to verify the incorporation of the modifying agents into the clay structure and the intercalation of the organoclay into the PI matrix. Results demonstrated that the introduction of a small amount of MMT (up to 5%) led to the improvement in thermal stability and mechanical properties of PI. The decomposition temperature of 5% weight loss (T_d,5%) in N₂ was increased by 46 and 36°C in comparison with pristine PI for the organoclay content of 5% with DOA and CPC, respectively. The nanocomposites were simultaneously strengthened and toughened. The dielectric constant, CTE, and water absorption were decreased. However, at higher organoclay contents (5–10%), these properties were reduced because the organoclay was poorly dispersed and resulted in aggregate formation. The effects of different organo‐modifiers on the properties of PI–MMT nanocomposite were also studied; the results showed that DOA was comparable with CPC. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci, 2006     

Novel POBD‐modified organoclay and its polyimide nanocomposites for removal of the Co(II) ion

An organophilic clay has been obtained via cation exchange reaction between sodium montmorillonite and the hydrochloride salt of 2‐(5‐(3,5‐diaminophenyl)‐1,3,4‐oxadiazole‐2‐yl)pyridine, POBD. Thermogravimetric analysis (TGA) showed that thermal decomposition of the organophilic clay starts at about 350°C, which shows that it is quite thermally stable compared with conventional montmorillonite modified with aliphatic long chain surfactants. POBD‐modified organoclay almost quantitatively removed the Co(II) ion from aqueous solution at pH = 10.0 (Q_t = 3.00 mg g⁻¹, R = 98.2%). A series of polyimide/clay nanocomposite materials (PCNs) consisting of POBD and benzophenone‐3,3′,4,4′‐tetracarboxylic dianhydride, BTDA were also prepared by an in situ polymerization reaction via thermal imidization. POBD‐modified organoclay was used as a surfactant at different concentrations. Intercalation of polymer chains within the organoclay galleries was confirmed by WXRD. Both the glass transition temperature and thermal stability are increased with respect to pristine PI at low clay concentrations. At high clay loadings, the aggregation of organoclay particles results in a decrease in T_g and thermal stability. In the SEM images of PCN 1 and 3%, too many micro cracks are observed in the background, and a flower‐shape pattern spreads uniformly over the entire surface. The maximum Co(II) uptake capacity and efficiency were observed at pH 10.0 within a 40‐h period for both PI and PCN films. POLYM. COMPOS., 2011. © 2011 Society of Plastics Engineers     

Preparation and characterization of microbial biodegradable poly(3‐hydroxybutyrate‐co‐4‐hydroxybutyrate)/organoclay nanocomposites

Novel biodegradable poly(3‐hydroxybutyrate‐co‐4‐hydroxybutyrate) [P(3HB‐co‐4HB)]/organoclay nanocomposites were prepared via solution casting. Exfoliated nanocomposite structure was confirmed by wide‐angle X‐ray diffraction (WAXD) and transmission electron microscopy (TEM) for the nanocomposites with low organoclay loadings (≤3 wt%), whereas the mixtures of exfoliated and unexfoliated organoclays were appeared in the nanocomposite with an organoclay content of 5 wt%. The organoclay fillers accelerated significantly the cold crystallization process of P(3HB‐co‐4HB) matrix. The thermal stability of the nanocomposites was in general better than that of pristine P(3HB‐co‐4HB). Considerable increase in tensile modulus was observed for the nanocomposites, especially at an organoclay content of 3 wt%. These results demonstrated that the nanocomposites improved the material properties of P(3HB‐co‐4HB). POLYM. COMPOS., 2012. © 2012 Society of Plastics Engineers     

The effect of polyoxypropylene‐montmorillonite intercalates on polymethylmethacrylate

Polymethylmethacrylate (PMMA)‐layered silicate nanocomposites have been prepared by in situ polymerization of commercial type of methylmethacrylate monomer (MMA), for denture base material, into organoclay. Organoclay was prepared through an ion exchange process between sodium cations in montmorillonite and NH₃⁺ groups in polyethertriamine hydrochloride and polyoxypropylene triamine hydrochloride with different molecular weight (5000, 440). X‐ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) have been used to investigate the structure of the resulting composites. Both intercalated and exfoliated nanocomposites were obtained depending on the type and amount of organoclay. The thermal decomposition temperatures of the nanocomposites were found to be higher than that of pristine polymer. PMMA was strongly fixed to inorganic surfaces, due to cooperative formation of electrostatic bonding between NH₃⁺ group and negatively charged surface of layered silicate and amide linkage between PMMA and polyethertriamine or polyoxypropylene triamine. The effect of the organoclay on the hardness, toughness, tensile stress, and elongation at break of the polymer was studied and was compared with pristine polymer. The hardness and Izod impact strength of PMMA‐organoclay nanocomposites were enhanced with the inclusion of clay. Tensile properties appear to be enhanced at certain organoclay content. However, the water absorption is slightly higher than the pristine PMMA. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers     

Investigation of nanostructure and properties of aromatic–aliphatic polyamide‐based nanocomposites with clay additives

Aromatic–aliphatic polyamide/clay nanocomposites were produced using solution intercalation technique. Surface modification of the clay was performed with ammonium salt of aromatic diamine and the polyamide chains were produced by condensation of 4‐aminophenyl sulfone with sebacoyl chloride (SCC) in dimethyl acetamide. Carbonyl chloride endcapped polymer chains were prepared by adding extra SCC near the end of polymerization reaction. The nanocomposites were investigated for organoclay dispersion, water absorption, mechanical, and thermal properties. Formation of delaminated and intercalated nanostructures was confirmed by X‐ray diffraction and TEM studies. Tensile strength and modulus improved for nanocomposites with optimum organoclay content (8 wt %). Thermal stability and glass transition temperatures of nanocomposites increased relative to pristine polyamide with augmenting organoclay content. The amount of water uptake for these materials decreased as compared with the neat polyamide. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Effect of clay on mechanical and gas barrier properties of blown film LDPE/clay nanocomposites

Low density polyethylene (LDPE)/clay nanocomposites, which can be used in packaging industries, were prepared by melt‐mix organoclay with polymer matrix (LDPE) and compatibilizer, polyethylene grafted maleic anhydride (PEMA). The pristine clay was first modified with alkylammonium salt surfactant, before melt‐mixed in twin screw extruder attached to blown‐film set. D‐spacing of clay and thermal behavior of nanocomposites were characterized by Wide‐Angle X‐ray Diffraction (WAXD) and differential scanning calorimetry (DSC), respectively. WAXD pattern confirmed the increase in PEMA contents exhibited better dispersion of clay in nanocomposites. Moreover, DSC was reported the increased PEMA contents caused the decrease in degree of crystallinity. Mechanical properties of blown film specimens were tested in two directions of tensile tests: in transverse tests (TD tests) and in machine direction tests (MD tests). Tensile modulus and tensile strength at yield were improved when clay contents increased because of the reinforcing behavior of clay on both TD and MD tests. Tensile modulus of 7 wt % of clay in nanocomposite was 100% increasing from neat LDPE in TD tests and 17% increasing in MD tests. However, elongation at yield decreased when increased in clay loading. Oxygen permeability tests of LDPE/clay nanocomposites also decreased by 24% as the clay content increased to 7 wt %. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

CO2 sorption and diffusion in polymethyl methacrylate–clay nanocomposites

This study reports the glass transition temperature (T_g), and sorption and diffusion of subcritical CO₂ gas in polymethyl methacrylate (PMMA) nanocomposites containing organically modified smectite clay, Cloisite 20A (C20A). A range of methods for preparing the PMMA‐clay nanocomposites was investigated and a solution coprecipitation method was selected as the most appropriate. Using this method, PMMA nanocomposite containing 2, 4, 6, and 10 wt% nanoclay loadings were prepared. Wide‐angle X‐ray diffraction (XRD) analysis and scanning electron microscopy (SEM) indicated that the 2 wt% nanocomposite materials had a well‐dispersed intercalated clay structure. The T_g for PMMA‐C20A nanocomposites, as measured by differential scanning calorimetry (DSC), was found to be independent of the clay loading. CO₂ solubility studies from 0 to 65°C and pressures up to 5.5 MPa using an in situ gravimetric technique were performed on compression‐molded films. The organoclay was found to have no effect on the solubility of CO₂ in PMMA, and therefore the solubility of CO₂ in the nanocomposite can be determined from the solubility of CO₂ in the matrix polymer alone. Diffusion coefficients were determined using the appropriate transport models for these test conditions and the diffusion coefficients for CO₂ in PMMA‐C20A composites were found to increase with organoclay loading. It is believed that the processing path taken to prepare the nanocomposites may have resulted in the agglomeration of the C20A organoclay, thereby preventing the polymer chains from fully wetting and intercalating a large number of clay particles. These agglomerations are responsible for the formation of large‐scale holes within the glassy nanocomposite, which behave as low resistance pathways for gas transport within the PMMA matrix. POLYM. ENG. SCI., 45:904–914, 2005. © 2005 Society of Plastics Engineers     

Nanocomposites of poly(trimethylene terephthalate) with organoclay

Two different kinds of clay were organomodified with cetylpyridinium chloride (CPC) as an intercalation agent. Poly(trimethylene terephthalate) (PTT)/organoclay nanocomposites were prepared by the solution intercalation method. Wide‐angle X‐ray diffraction (WAXD) indicated that the layers of clay were intercalated by CPC and the interlayer spacing was a function of the cationic exchange capacity (CEC) of the clay: the higher the CEC, the larger the interlayer spacing is. The WAXD studies showed that the interlayer spacing of organoclay in the nanocomposites depends on the amount of organoclay. From the results of differential scanning calorimetry analysis it was found that clay behaves as a nucleating agent and enhances the crystallization rate of PTT. The maximum enhancement of the crystallization rate for the nanocomposites was observed in nanocomposites containing about 5 wt % organoclay with a range of 1–15 wt %. The thermal stability of the nanocomposites was enhanced by the addition of 1–10 wt % organoclay as found from thermogravimetric analysis. The thermal stability of the PTT/organoclay nanocomposites was related to the organoclay content and the dispersion in the PTT matrix. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 3315–3322, 2003     

Bottle‐to‐bottle recycling of PET via nanostructure formation by melt intercalation in twin screw compounder: Improved thermal,barrier, and microbiological properties

Attempts have been made to modify the properties of the injection processing‐scraped PET (denoted as RPET) via intercalation with different levels of organically modified nanoclay (montmorillonite) by melt blending in a corotating twin screw compounder. The clay platelets dispersion state has been qualitatively correlated with the melt linear viscoelastic as well as tensile and barrier properties of the prepared nanocomposites. Oxygen permeation of the nanocomposite PET films showed significant reduction compared with the pristine PET polymer. All the PET/nanoclay composites exhibited no bacterial growth, with no potentiality to generate acetaldehyde, as measured by GC/Mass analyzer. X‐ray diffractometry and transmission electron microscopy performed on the scraped PET/organoclay nanocomposite samples showed increase in d₀₀₁ spacing of the clay layers and their dispersion throughout the PET matrix. Differential scanning calorimetry analysis showed higher crystallization temperature as well as crystallization enthalpy (ΔH_c) for the nanocomposite samples, compared with the unprocessed virgin PET. The RPET nanocomposite samples composed of 3 and 5% of nanoclay exhibited enhanced melt elastic modulus and pseudosolid‐like behavior at low shear frequencies measured by rheomechanical spectroscopy than the unfilled pristine‐scraped PET, indicating the formation of nanoscopic network structure by the clay platelets, which leads to the development of nanostructured resin. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Preparation and characterization of polyethylene–clay nanocomposites by using chlorosilane‐modified clay

Clay was modified by trimethylchlorosilane; after modification, hydroxyl groups at the edge of layers were reacted and CEC value was drastically decreased. Polyethylene–clay composites were prepared by melt compounding. Wide angle X‐ray diffraction (WAXD) and transmission electron microscopy (TEM) showed that intercalated nanocomposites were formed using organoclay ion‐exchanged from chlorosilane‐modified clay, but conventional composites formed using organoclay directly ion‐exchanged from crude clay. Dynamic mechanical analysis (DMA) of PE and PE–clay composites was conducted; the results demonstrated that nanocomposites were more effective than conventional composites in reinforcement and addition of organoclay resulted in the increase of glass transition temperature (T_g), but crude clay had no effect on T_g of PE–clay composites. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 676–680, 2004     

Synthesis of poly(arylene disulfide)–vermiculite nanocomposites via in situ ring‐opening polymerization of macrocyclic oligomers

Exfoliated poly(4, 4′‐oxybis(benzene)disulfide)/vermiculite (POBDS/VMT) nanocomposites were successfully synthesized via in situ melt intercalation of cyclo(4, 4′‐oxybis(benzene)disulfide) oligomers (COBDS) into octadecylammonium‐exchanged VMT (organo‐VMT). The POBDS/VMT nanocomposites were melt fabricated in a two‐step process. First, the COBDS/VMT nanocomposite precursor was fabricated by melt delaminating organo‐VMT with COBDS at a temperature slightly higher than its melting point. Subsequently, exfoliated POBDS‐VMT nanocomposites can be prepared in situ via instant melt ring‐opening polymerization of the COBDS‐VMT nanocomposite precursor. The nanoscale dispersion of VMT layers within POBDS polymer was confirmed by X‐ray diffraction, scanning electron microscopy and transmission electron microscopy. High molecular weight POBDS polymer was formed in a few minutes at the same time as the nanocomposite formation. The results of dynamic mechanical analysis showed that the storage modulus and glass transition temperature of the nanocomposites are much higher than those of the POBDS matrix, even with a very small amount of VMT addition. This methodology provides a potential approach to synthesize high‐performance polymer/clay nanocomposites. Copyright © 2004 Society of Chemical Industry     

Polyimide/organo‐montmorillonite nanocomposites: A comparative study of the organoclays modified with aromatic diamines

Six organophilic clays have been obtained through cation‐exchange between sodium montmorillonite (Na^+‐Mt) and the hydrochloride salts of aromatic diamines (DA1–6). The results obtained by thermogravimetric analysis (TGA) showed that the organophilic clays start to decomposition within 150–340°C, which shows that they are thermally stable compared with conventional montmorillonite modified with aliphatic long‐chain quaternary alkyl ammonium salts. The highest thermal stability and interlayer basal spacing were observed for the organoclay obtained from 3,3′‐sulfonyl dianiline (DA2), and therefore it was chosen for preparing clay/polymer nanocomposite materials (CPN). Polyimide/clay nanocomposite materials consisting of benzophenone‐3,3′,4,4′‐tetracarboxylic dianhydride (BTDA) and 2‐(5‐(3,5‐diaminophenyl)‐1,3,4‐oxadiazole‐2‐yl)pyridine (POBD) were also obtained by an in situ polymerization reaction through a thermal imidization. DA2‐Mt was used as filler at different concentrations. Both the thermal stability and the glass transition temperature (T_g) are increased with respect to pure polyimide (PI) at low clay loadings. At high clay concentrations, the organoclay particles make aggregate and as results of this phenomena T_g and thermal stability are decreased. POLYM. COMPOS., 36:613–622, 2015. © 2014 Society of Plastics Engineers     

Polyimide nanocomposites prepared from high-temperature, reduced charge organoclays

Montmorillonite clays modified with the dihydrochloride salt of 1,3-bis(3-aminophenoxy)benzene (APB) were used in the preparation of polyimide/organoclay hybrid films. Organoclays with varying surface charge based upon APB were prepared and examined for their dispersion behavior in the polymer matrix. High molecular weight poly(amide acid) solutions were prepared in the presence of the organoclays. Films were cast and subsequently heated to 300 °C to cause imidization. The resulting nanocomposite films, containing 3 wt% of organoclay, were characterized by transmission electron microscopy and X-ray diffraction. The clay's cation exchange capacity (CEC) played a key role in determining the extent of dispersion in the polyimide matrix. Considerable dispersion was observed in some of the nanocomposite films. The most effective organoclay was found to have a CEC of 0.70 meq/g. Nanocomposite films prepared with 3-8 wt% of this organoclay were characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), and thin-film tensile testing. High levels of clay dispersion could be achieved even at the higher clay loadings. Results from mechanical testing revealed that while the moduli of the nanocomposites increased with increasing clay loadings, both strength and elongation decreased.     

Synthesis and characterization of colorless polyimide nanocomposite films

A poly(amic acid) was prepared through the reaction of 4,4′‐(hexafluoroisopropylidene)diphthalic anhydride and 2,2′‐bis(trifluoromethyl) benzidine in N,N‐dimethylacetamide. Hybrid films were obtained from blend solutions of the precursor polymer and the organoclay dodecyltriphenylphosphonium–mica, with the organoclay content varying from 0 to 1.0 wt %. The cast films of poly(amic acid) were heat‐treated at different temperatures to create polyimide (PI) hybrid films. These PI hybrid films showed excellent optical transparency and were almost colorless. The intercalation of PI chains in the organoclay was examined with wide‐angle X‐ray diffraction and electron microscopy. In addition, the thermomechanical properties were tested with differential scanning calorimetry and thermogravimetric analysis, and the gas permeability was determined. The addition of only a small amount of the organoclay was sufficient to improve the thermal and mechanical properties of the PI, with the maximum enhancement being observed with 0.5 wt % organoclay. However, the water vapor permeability decreased with the clay loading increasing from 0 to 0.5 wt %. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

4,4′‐Bismaleimidodiphenyl methane modified novolak resin/titania nanocomposites: Preparation and properties

4,4′‐Bismaleimidodiphenyl methane modified novolak resin/titania nanocomposites were prepared by the sol–gel process of tetrabutyl titanate in the presence of 4,4′‐bismaleimidodiphenyl methane modified novolak resin prepolymers with acetyl acetone as a stabilizer. These nanocomposite materials were characterized by Fourier transform infrared analysis, dynamical mechanical analysis, thermogravimetric analysis, transmission electron microscopy, and field emission scanning electron microscopy. Nanometer titania particles were formed in the novolak resin matrix, and the average original particle size of the dispersed phase in the nanocomposites was less than 150 nm, but particle aggregates of larger size existed. The introduction of the titania inorganic phase with a nanoscale domain size did not improve the glass‐transition temperature of the nanocomposites but lowered the thermal resistance of the material because of the incomplete removal of acetyl acetone coordinated with tetrabutyl titanate, and it improved the modulus of the material at lower temperatures (<200°C) but lowered the modulus at higher temperatures (>250°C). © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 52–57, 2006     

Microstructure and thermal properties of ethylene‐(vinyl acetate) copolymer/rectorite nanocomposites

Ethylene‐(vinyl acetate) copolymer (EVA)/rectorite nanocomposites were prepared by direct melt extrusion of EVA and organo‐rectorite. The microstructures and thermal properties of EVA nanocomposites were characterized by X‐ray diffraction (XRD), scanning electron microscopy (SEM), solid‐state nuclear magnetic spectroscopy, positron annihilation spectroscopy, thermal gravimetric analysis (TGA) and dynamic mechanical analysis techniques. XRD pattern and SEM images show that the intercalated structure is formed and rectorite is finely dispersed in EVA matrix. When organoclay content of the hybrid increases to 7.5 wt%, or pristine rectorite was used instead of organoclay, the crystallization behavior of EVA nanocomposite changes greatly and the ratio of the monoclinic to orthorhombic crystal increases significantly. The relative fractional free volume of the nanocomposite decreases with the increasing organo‐rectorite content, and the values of damping factor (tan δ) for all nanocomposites are lower than that of pure EVA. These facts illuminate that intercalated structure restricts the segment motion and mobilization of polymer chain. TGA results of EVA nanocomposites in air indicate that deacylation of EVA is accelerated because of the catalytic effect and the thermal degradation of the main chain is delayed owing to the barrier effect of silicate layers. Copyright © 2005 Society of Chemical Industry