In‐situ synthesis of poly(ethylene terephthalate)/clay nanocomposites using TiO2/SiO2 sol‐intercalated montmorillonite as polycondensation catalyst

A novel organic montmorillonite, which could act as both polycondensation catalyst of poly(ethylene terephthalate) (PET) and filler of PET/clay nanocomposites, was prepared. Original montmorillonite was first treated with different amounts of poly(vinylpyrrolidone) (PVP), and then intercalated by TiO₂/SiO₂ sol to gain polycondensation catalytic activity. The acquired clay possessed excellent thermal stability and would not degrade during the polycondensation step. PET/clay nanocomposites were prepared via in‐situ polymerization using the organo‐clay as polycondensation catalysts. The morphologies of the nanocomposites were characterized by X‐ray diffraction and transmission electron microscope. The results indicated that the amount of PVP and TiO₂/SiO₂ sol strongly affected the dispersion state of the clay, and finally, partially exfoliated PET/clay nanocomposites were obtained. The nanocomposites had better properties than pure PET due to the incorporation of the delaminated clay layers. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers     

New clay‐supported Ziegler–Natta catalyst for preparation of PE/Clay nanocomposites via in situ polymerization

Polyethylene/clay (PE/Clay) nanocomposites were prepared by the in situ polymerization of ethylene using the new Clay/butyl octyl magnesium (BOM)/Chloroform/EtOH/TiCl₄/tri ethyl aluminum (TEA) catalyst system in heptane where BOM and TEA were the support for the clay modification and cocatalyst, respectively. The influence of the modified clay using BOM on the catalyst and polymerization was investigated. Also, the effect of temperature, pressure, hydrogen, and the molar ratios of TEA/Ti on the catalyst yield and ethylene consumption (polymerization rate) were studied. It was found that the above clay‐supported catalyst was an efficient Ziegler–Natta type catalyst due to its suitable yield for the polymerization of ethylene toward the production of the PE/Clay nanocomposites. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Preparation and characterization of polyethylene (PE)/clay nanocomposites by <Emphasis Type="Italic">in situ</Emphasis> polymerization with vanadium-based intercalation catalyst

Summary  Complete exfoliation of clay during vanadium-based Zigler-Natta polymerization of ethylene has been successfully carried out by using clay and MgCl₂ hybrid supports. MgCl₂ offers catalyst loading sites, and the vanadium catalyst is avoided directly anchoring in the surface of the clay, so intercalation catalyst clay/MgCl₂/VOCl₃displays high activity for ethylene polymerization. Exfoliated PE/clay nanocomposites are confirmed by X-ray diffraction (XRD), and transmission electron microscopy (TEM). Strong interaction between the dispersed clay particles and the polymer matrices provides good thermal and mechanical properties. Compared with pure PE, all these nanocomposites show enhancement of the melting temperature (T_m) and the thermal decomposition temperatures. Additionally, the incorporation of clay into the PE matrix significantly improves the mechanical properties of these nanocomposites. The increased tensile strength has been observed in the range of 3.4 to 7.9 MPa. The tensile moduli of the PE/clay nanocomposite are 23.4%-45.3% higher than that of the pure PE.     

Improved dispersion of clay platelets in poly(butylene terephthalate) nanocomposite by ring‐opening polymerization of cyclic oligomers: Effect of the processing conditions and comparison with nanocomposites obtained by melt intercalation

Poly(butylene terephthalate) nanocomposites with organically modified montmorillonites have been prepared by in‐situ ring opening polymerization of PBT cyclic oligomers. High molecular weight polymers can be obtained by choosing the proper polymerization conditions and catalyst in very short polymerization time (10 min) and low temperature (205°C). A better dispersion of the clay and a consistently higher M_w have been obtained by this method respect to the standard melt intercalation approach, leading to improved thermo‐mechanical properties of the nanocomposite. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Free‐volume hole properties of two kinds thermoplastic nanocomposites based on polymer blends probed by positron annihilation lifetime spectroscopy

Two type of nanocomposites—an immiscible blend, high density polyethylene/polyamide 6 (HDPE/PA‐6) with organomodified clay, and a compatibilized blend, high density polyethylene grafted with acrylic acid/PA‐6 (PEAA/PA‐6) with organomodified clay—were prepared via melt compounding. X‐ray diffraction and transmission electron microscopy results revealed that the clay was intercalated and partially exfoliated. Positron annihilation lifetime spectroscopy has been utilized to investigate the free‐volume hole properties of two type of nanocomposites. The results show a negative deviation of free‐volume size in PEAA/PA‐6 blend, and a positive deviation in HDPE/PA‐6 blend, and I₃ has a greater negative deviation in compatibilized blend than in immiscible blend due to interaction between dissimilar chains. For nanocomposites based on polymer blends, in immiscible HDPE/PA‐6/organomodified clay system, the variation of free‐volume size with clay content is not obvious and the free‐volume concentration and fraction decreased. While in the case of compatibilized PEAA/PA‐6/organomodified clay nanocomposites, complicated variation of free‐volume properties due to interactions between two phases and organomodified clay was observed. And the interaction parameter β shows the interactions between polymers and organomodified clay. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 2463–2469, 2006     

Catalytic activity during the preparation of PE/clay nanocomposites by in situ polymerization with metallocene catalysts

Catalytic activity during the formation of polyethylene (PE)/clay nanocomposites by in situ polymerization with metallocenes was studied. Ethylene polymerization was carried out with the homogeneous metallocene in the presence of the clay particles and using the clay‐supported metallocene catalyst. It was found that the catalytic activity of the homogeneous metallocene does not decrease in the presence of the clay particles and only a slight decrease of activity occurs using the clay‐supported catalyst. The modification of the clay with MAO cocatalyst as well as its intercalation with ODA surfactant were found to play an important role during the in situ formation of the PE/clay nanocomposite. ODA‐intercalated clay apparently facilitates the activation and monomer insertion processes on zirconocene centers located in internal sites of the clay structure. Although metallocene supported on MAO‐treated clay exhibited somewhat lower catalytic activity than that supported directly on the ODA‐intercalated clay, both systems favored the production of PE nanocomposites containing highly exfoliated clay particles. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Effect of clay platelet dispersion as affected by the manufacturing techniques on thermal and mechanical properties of PMMA‐clay nanocomposites

In this work, the properties of Poly(methyl methacrylate) (PMMA)‐clay nanocomposites prepared by three different manufacturing techniques viz., solution mixing, melt mixing, and in‐situ bulk polymerization in presence of clay were studied. Morphological analysis revealed that the extent of intercalation and dispersion of the nanoclay were relatively higher in the in‐situ polymerized nanocomposites than those of solution and melt blended nanocomposites. Differential Scanning Calorimetric study indicated maximum increment in T_g of the PMMA in the in‐situ polymerized PMMA‐clay nanocomposites. Thermo gravimetric analysis showed improved thermal stability of PMMA in all the nanocomposites and the maximum improvement was for in‐situ polymerized nanocomposites. The storage moduli of all the nanocomposites were higher than the pure PMMA. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Synthesis of polypropylene/clay nanocomposites using bisupported Ziegler‐Natta catalyst

In this article, preparation of polypropylene/clay nanocomposites (PPCNC) via in situ polymerization is investigated. MgCl₂/montmorillonite bisupported Ziegler‐Natta catalyst was used to prepare PPCNC samples. Montmorillonite (MMT) was used as an inert support and reinforcement agent. The nanostructure of the composites was characterized by X‐ray diffraction, scanning electron microscopy, and transmission electron microscopy techniques. Obtained results showed that silica layers of the MMT in these PPCNC were intercalated, partially exfoliated, and uniformly dispersed in the polypropylene matrix. Thermogravimetric analysis showed good thermal stability for the prepared PPCNC. Differential scanning calorimetric was used to investigate both melting and crystallization temperatures, as well as the crystallinity of the PPCNC samples. Results of permeability analysis showed significant increase in barrier properties of PPCNC films. Effective parameters on molecular weight and flow ability of produced samples such as Al/Ti molar ratio and H₂ concentration were also investigated. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Influence of clay and predispersion method on the structure and properties of polystyrene (PS)‐clay nanocomposites

To prepare the polystyrene (PS)‐clay nanocomposites via an in situ emulsion polymerization, a clay predispersion method, i.e. dispersing the organic clay in the emulsifier solution by the assistance of ultrasonic, was proposed in this study. The conventional method, predispersing the organic clay into the monomer, was also presented for the comparison. The morphology analysis based on the X‐ray Deflection (XRD) and Transmission Electronic Microscopy (TEM) results suggested that the more uniform clay dispersion in the final nanocomposites could be achieved through the new method. The inorganic clay (Na‐MMT) and two organic clays (C₁₈‐MMT and VC₁₈‐MMT) synthesized by exchanging inorganic cations with the trimethyloctadecyl ammonium chloride (OTAC) and the vinylbenzyldimethyloctadecyl ammoniun chloride (VOAC) were chosen to investigate the influence of the clay surface modification on the properties of nanocomposites. The Dynamic Mechanical Analysis (DMA) results showed the storage modulus G′s of the nanocomposites had different enhancements over that of the pure PS, especially when the temperature approached the glass transition temperature (T_g). The T_gs of the nanocomposites, however, varied with the microstructure and the interactions between the polymer and the clay layers. The Na‐MMT and VC₁₈‐MMT increased the T_g, while the T_gs of PS/C₁₈‐MMT nanocomposites were slightly lower than that of the pure PS. POLYM. ENG. SCI., 2009. © 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.     

PE/clay nanocomposites produced via in situ polymerization by highly active clay-supported Ziegler–Natta catalyst

The synthesis of polyethylene/clay (PE/clay) nanocomposites by means of in situ polymerization was achieved using the clay/BOM/chloroform/EtOH/TiCl₄/TEA catalyst system where butyl octyl magnesium (BOM) and triethyl aluminum (TEA) were a modifier for the clay and cocatalyst, respectively. It was found that the catalyst had high activity in ethylene polymerization. The microstructure of the resulting PE/clay nanocomposites was characterized by X-ray diffraction, transmission electron microscopy, and scanning electron microscopy. The examinations evidenced the nanocomposite formation with exfoliated clay in the PE matrix. The thermal properties of the produced nanocomposites were studied by differential scanning calorimetry, oxidation induction time, and thermal gravimetric analysis. Furthermore, the mechanical properties of the nanocomposites were evaluated by the impact and tensile tests. The examinations indicated the improved thermal stability and mechanical properties. Meanwhile, a wide range of molecular weights were produced in the presence of hydrogen.     

Polyethylene nanocomposites by gas‐phase polymerization of ethylene in the presence of a nanosilica‐supported zirconocene catalyst system

BACKGROUND: Much of the current research related to the development of in situ nanocomposites of olefins by polymerizing them with metallocenes in the presence of surface‐treated fillers is carried out in the slurry phase. In slurry‐phase methods a large amount of solvent is required and there is always a need of purification of the final product due to the possibility of traces of solvents present in the product. To overcome these drawbacks, to perform solvent‐free metallocene‐catalysed polymerizations with in situ incorporation of inorganic nanoparticles, we have used a gas‐phase polymerization technique as this does not require solvents and also utilizes monomer feed stocks efficiently. RESULTS: The catalyst used for the synthesis of in situ polyethylene nanocomposites by gas‐phase polymerization was nanosilica‐supported zirconocene. The fillers used were Cloisite‐20A, kaolin and nanosilica. Three different in situ polyethylene nanocomposites, i.e. Cloisite‐20A‐filled polyethylene (CFPE), kaolin‐filled polyethylene (KFPE) and nanosilica‐filled polyethylene (SFPE), were prepared by gas‐phase polymerization. The nanocomposites were obtained in the form of fine powder. The polyethylene content in the developed nanocomposites is in the orthorhombic crystalline phase. Using our approach, it is observed that the nanofillers are completely encapsulated by a thin layer of polyethylene. Significantly higher molecular weight polyethylene was formed in the case of KFPE in comparison to CFPE and SFPE. The thermal decomposition temperature, melting temperature and enthalpy are also observed to be higher for KFPE. CONCLUSIONS: The gas‐phase polymerization technique has been successfully carried out for the synthesis of in situ polyethylene nanocomposites. Copyright © 2007 Society of Chemical Industry     

PE/Clay Nanocomposite with Bimodal Molecular Weight Distribution Produced Via In-Situ Polymerization

A Ti-based Ziegler–Natta catalyst supported on the clay was used for producing the polyethylene/clay nanocomposites through in situ polymerization. This catalyst showed high activity in the ethylene polymerization. The two-step polymerization approach, i.e. in the presence and absence of hydrogen, was laid out to broaden the molecular weight distribution of the polyethylene/clay nanocomposite. The molecular weights and molecular weight distribution of the nanocomposites were characterized by the gel permeation chromatography. It was found that the molecular weight distribution was remarkably widened towards bimodal distribution by using the above mentioned approach. The thermal properties of the produced nanocomposites were studied by differential scanning calorimetry and thermal gravimetric analysis. The microstructure of the resulting bimodal polyethylene/clay nanocomposite was investigated by X-ray diffraction and transmission electron microscopy. The thermal gravimetric analysis indicated an improved thermal stability of the produced nanocomposites. In addition, the studies proved the nanocomposite formation with the exfoliated structure of the clay in the polyethylene matrix.     

Preparation and characterization of poly(styrene‐b‐butadiene‐b‐styrene)/montmorillonite nanocomposites

With some polymerizable small molecules grafting onto the montmorillonite surface, we disposed the clay through in‐situ emulsion polymerization, and the structure of the modified montmorillonites were studied through Fourier transform infrared spectroscopy (FTIR) and X‐ray diffraction (XRD). The nanocomposites of poly(styrene‐b‐butadiene‐b‐styrene) (SBS)/montmorillonite with excellent mechanical properties were prepared by mixing SBS and the modified montmorillonite on the double rollers at 150°C. The exfoliation of the layered silicates was confirmed by XRD analysis and transmission electron microscopy (TEM) observation. After mechanical kneading of the molten nanocomposites, the exfoliation structure of the silicates is still stable for polystyrene macromolecules grafting onto the silicates. Upon the addition of the modified montmorillonite, the tensile strength, elongation at break and tear strength of the nanocomposites increased from 22.6 MPa to 31.1 MPa, from 608% to 948%, from 45.32 N/mm to 55.27 N/mm, respectively. The low‐temperature point of glass‐transition temperature (T_g) of the products was about −77°C, almost constant, but the high‐temperature point increased from 97°C to 106°C. In addition, the nanocomposites of SBS and modified montmorillonites showed good resistance to thermal oxidation and aging. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers     

Synthesis,structure, and thermal properties of new polypropylene nanocomposites prepared by using MgCl2‐mica/TiCl4 based catalyst

Preparation of polypropylene/mica nanocomposites via in situ polymerization is investigated. The nanocomposites were successfully synthesized using a Ziegler‐Natta catalyst based on MgCl₂/modified mica/TiCl₄. Muscovite mica was organically modified with quaternary ammonium salt, and with triethylaluminum. The treatment with triethylaluminum increased the disorder in the stacking of clay layers, producing a more active catalyst for propylene polymerization, although the mica containing catalysts had lower activity than the standard one prepared without clay. The nanostructure of the composites was characterized by X‐ray diffraction. The results showed that part of the mica layers were exfoliated in the polymer matrix, although tactoids were still present. Small‐angle X‐ray scattering analysis was used to determine how mica and its concentration influence the size of the polymer nanocrystals. Differential scanning calorimetry was used to investigate both melting and crystallization temperatures, as well as the crystallinity of the nanocomposite samples. Thermogravimetric analysis showed that polypropylene/mica nanocomposites presented much higher thermal stability than the polypropylene without mica, which means that mica had a barrier effect against heat. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45587.     

Synthesis of poly(ε‐caprolactone)/clay nanocomposites using polyhedral oligomeric silsesquioxane surfactants as organic modifier and initiator

Poly(ε‐caprolactone)/clay nanocomposites were synthesized by in situ ring‐opening polymerization of ε‐caprolactone in the presence of montmorillonite modified by hydroxyl functionalized, quaternized polyhedral oligomeric silsesquioxane (POSS) surfactants. The octa(3‐chloropropyl) polyhedral oligomeric silsesquioxane was prepared by hydrolytic condensation of 3‐chloropropyltrimethoxysilane, which was subsequently quaternized with 2‐dimethylaminoethanol. Montmorillonite was modified with the quaternized surfactants by cation exchange reaction. Bulk polymerization of ε‐caprolactone was conducted at 110°C using stannous octoate as an initiator/catalyst. Nanocomposites were analyzed by X‐ray diffraction, transmission electron microscopy, thermo gravimetric analysis, and differential scanning calorimetry. Hydroxyl functionalized POSS was employed as a surface modifier for clay which gives stable clay separation for its 3‐D structure and also facilitates the miscibility of polymer with clay in the nanocomposites due to the star architecture. An improvement in the thermal stability of PCL was observed even at 1 wt % of clay loading. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Nonisothermal crystallization behavior of melt‐intercalated polyethylene‐clay nanocomposites

The influence of nanoclay particles on the nonisothermal crystallization behavior of intercalated polyethylene (PE) prepared by melt‐compounding was investigated. It is observed that the crystallization peak temperature (T_p) of PE/clay nanocomposites is slightly but consistently higher than the neat PE at various cooling rates. The half‐time (t_0.5) for crystallization decreased with increase in clay content, implying the nucleating role of nanoclay particles. The nonisothermal crystallization data are analyzed using the approach of Avrami (Polymer 1971, 12, 150), Ozawa (Polym Eng Sci 1997, 37, 443), and Mo and coworkers (J Res Natl Bur Stand 1956, 57, 217), and the validity of the different kinetic models to the nonisothermal crystallization process of PE/clay nanocomposites is discussed. The approach developed by Mo and coworkers successfully explains the nonisothermal crystallization behavior of PE and PE/clay nanocomposites. The activation energy for nonisothermal crystallization of neat PE and PE/clay nanocomposites is determined using the Kissinger (J Res Natl Bur Stand 1956, 57, 217) method. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 3809–3818, 2006     

Structure and properties of multi‐walled carbon nanotubes/polyethylene nanocomposites synthesized by in situ polymerization with supported Cp2ZrCl2 catalyst

Multi‐walled carbon nanotubes (MWCNTs)/polyethylene (PE) nanocomposites were prepared via in situ polymerization with MWCNTs supported Bis‐ (cyclopentadienyl) zirconium dichloride (Cp₂ZrCl₂) catalyst. X‐ray photoelectron spectroscopy (XPS) and field emission scanning electron microscope (FESEM) results implied that Cp₂ZrCl₂ catalyst was immobilized in the surface of the MWCNTs supports via a bridge of methylaluminoxane (MAO). The efficient dispersion of MWCNTs in PE matrix and the strong compressive forces associated with PE on the MWCNTs were demonstrated by means of transmission electron microscope (TEM), FESEM and Raman spectra. With introducing 0.2 wt% MWCNTs, both the tensile strength and elongation of MWCNTs/PE nanocomposite were improved by factors of 1.6 (from 29 to 45 MPa) and 1.5 (from 909% to 1360%) comparing with the pure PE, respectively. Morphology observation of fractured surface revealed that the PE firmly adhered to the nanotubes, which was responsible for the significant improvement of the mechanical properties of nanocomposites. Thermal stabilities of the nanocomposites were significantly improved. In addition, the MWCNTs/PE nanocomposites showed very high ultraviolet (UV) shielding property, which could increase photooxidative stability of the PE. POLYM. COMPOS., 2010. © 2009 Society of Plastics Engineers     

Synthesis and characterization of exfoliated poly(styrene‐co‐methyl methacrylate) nanocomposite via miniemulsion atom transfer radical polymerization: an activators generated by electron transfer approach

Exfoliated poly(styrene‐co‐methyl methacrylate) nanocomposites were synthesized using activators generated by electron transfer for atom transfer radical polymerization (AGET ATRP). Miniemulsion polymerization was used for its abundant advantages to encapsulate inorganic materials and eliminate organic solvents from products for environmentally friendly purposes. Cetyltrimethylammonium bromide (CTAB) as a cationic surfactant, which is an effective surfactant at higher temperatures, was used to stabilize the miniemulsion system. Successful miniemulsion AGET ATRP was carried out by using 4,4'‐dinonyl‐2,2'‐bipyridine (dNbPy) as a hydrophobic ligand. Formation of monodispersed droplets and particles with sizes in the range of 200nm was examined by dynamic light scattering (DLS). Conversion and molecular weight study were also carried out using gravimetry and gel permeation chromatography, respectively. By adding clay content, a decrease in the conversion and molecular weight of the nanocomposites are observed. However, an increase in the PDI values of nanocomposites was observed by the addition of nanoclay content. Thermogravimetric analysis results demonstrate that thermal stability of all the nanocomposites in comparison with the neat copolymer increases. Differential scanning calorimetry results show that T_g decreases by increasing clay content. Monodisperse distribution of spherical shape particles with sizes in the range of ∼ 200 nm was demonstrated by using scanning electron microscopy images of nanocomposite containing 1 wt% of nanoclay, which is more compiled with DLS results. Transmission electron microscopy results shows well‐dispersed exfoliated clay layers in the polymer matrix of PSMNM 1, which is coincidence with X‐ray diffraction data. POLYM. COMPOS., 2011. © 2011 Society of Plastics Engineers     

Synthesis and characterizations of poly(α‐naphthylamine)—Nanocomposites

Poly(α‐naphthylamine) (PNA)—natural clay nanocomposites were prepared by in situ polymerization method through oxidative initiation method. Effect of nanoclay on the rate of polymerization (R_p) of Naphthylamine (NA), thermal stability of PNA, and conductivity of PNA were tested. Effect of nanoclay on the morphology of PNA was also tested. The TGA results inferred that the % weight residue remain above 700°C was increased with the increase of amount of clay. XRD results confirmed the intercalation of PNA into the basal spacing of natural clay. TEM showed the presence of nanosized particle in the PNA‐natural clay nanocomposites. The conductivity value of polymer‐nanocomposite has increased with the increase of amount of natural clay. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers