Theoretical and experimental analyses of rheological,compatibility and mechanical properties of PVMQ/XNBR-g GMA/XNBR/GO ternary hybrid nanocomposites

Iranian Polymer Journal - Effects of graphene oxide (GO) on various properties of rubber hybrid nanocomposites based on PVMQ/XNBR-g-GMA/XNBR (phenyl-vinyl-methyl-polysiloxane/carboxylated nitrile...     

Polyvinylpolypyrrolidone-Supported Chlorosulfonic Acid: An Efficient Catalyst for One-Pot Synthesis of Dihydropyrimidinones and Octahydroquinazolin-2,5-diones

Polyvinylpolypyrrolidone-supported chlorosulfonic acid has been successfully applied to perform one-pot reaction of arylaldehydes, urea, ethylacetoacetate, or cyclic 1,3-diketo compounds under solvent-free condition at 70°C to provide a series of dihydropyrimidinones and octahydroquinazolin-2,5-diones in good to excellent yields. The method offers several advantages such as high yield, short reaction time, simple workup, easy preparation, and reusability of the catalyst. The [PVPP-SO₃H]⁺Cl^? catalyst was characterized via Fourier transform infrared spectroscopy (FT-IR) and thermal gravimetric analysis (TGA). Moreover, the catalyst could be recycled several times without significant loss of its catalytic activity. Clean methodologies, easy work-up procedure, high yield, and simple preparation of the catalyst are some advantages of this article.     

Synthesis of polyamides from p-Xylylene glycol and dinitriles

A series of polyamides were prepared by direct polyamidation of the p-Xylylene glycol with various commercially available dinitriles via Ritter reaction. All the synthesized polyamides showed good solubility in amide type solvents such as N-methyl-2-pyrrolidone, N,N-dimethyl acetamide, N,N-dimethyl formamide, and dimethyl sulfoxide. They exhibited inherent viscosities in the range of 0.25–0.62 dl/g. Elemental analysis, differential scanning calorimetry, thermogravimetric analysis, infrared and H¹-NMR spectroscopies were used to characterize the polymers. According to the DSC analysis, the glass transition temperatures of the polyamides were found to be 95–174°C. Thermogravimetric analysis indicated that the polymers show the 10% weight loss temperatures in the range of 250–350°C.     

Synthesis of poly(ether amide)s from p‐xylylene glycol and bis(ether nitrile)s

BACKGROUND: Poly(ether amide)s have been well studied in terms of improving the physical and thermal properties of aromatic polyamides. Poly(ether amide)s of high enough molecular weight to be useful for industrial purposes are generally difficult to prepare. The objective of this project was to introduce a simple and commercially feasible process to prepare poly(ether amide)s by a polymerization reaction at relatively low temperature. RESULTS: A series of poly(ether amide)s were prepared by direct polyamidation of p‐xylylene glycol with bis(ether nitrile)s via the Ritter reaction using concentrated H₂SO₄ in acetic acid. The synthesized poly(ether amide)s showed good solubility in polar aprotic solvents. The resultant poly(ether amide)s had inherent viscosities in the range 0.36–1.03 dL g^?1. The glass transition temperatures of the poly(ether amide)s were determined using differential scanning calorimetry to be in the range 190–258 °C. Thermogravimetric analysis data for these polymers indicated the 10% weight loss temperatures to be in the range 290–390 °C in nitrogen atmosphere. CONCLUSION: The Ritter reaction was applied for the synthesis of a variety of poly(ether amide)s with moderate to high molecular weights. This procedure provides a simple polymerization process for the convenient preparation of poly(ether amide)s in high yield at room temperature. Copyright © 2009 Society of Chemical Industry     

Studies of thermal,mechanical properties,and kinetic cure reaction of carboxyl-terminated polybutadiene acrylonitrile liquid rubber with diepoxy octane

Epoxy resins, despite their unique properties, have limitations in many applications due to their low fracture toughness. One of the most effective methods to overcome this limitation is to use toughening agents, such as carboxyl terminated poly butadiene-acrylonitrile (CTBN) in the epoxy matrix. CTBN can react with various compounds, such as epoxies. In this study, we investigated the severity of CTBN sedimentation with di epoxy octane (DEO) in the presence basis catalysts. The studied of the physical properties of the synthesized copolymer in the presence of pyridine compared to other catalysts increases mechanical properties (248.43% elongation, 0.63 MPa strength, and 32 hardness with Shore A) and decreases the glass transition temperature (−45.1) of the copolymer. Investigated the cure kinetics of the CTBN-DEO reaction was in the presence of pyridine using a nonisothermal technique of differential scanning calorimetry, and the curing kinetic parameters, such as activation energy (E_a), pre-exponential factor (A), and rate constant (k), were calculated by different kinetic methods. The obtained curing kinetic values with different kinetic methods are well-matched, the E_a values are in the range of 91.3–97.1 kJ.mol⁻¹ and the A values are in the range of 0.48 × 10¹¹–1.51 × 10¹¹ S⁻¹.     

Analysis and modeling of modified styrene–acrylonitrile/carboxylated acrylonitrile butadiene rubber nanocomposites filled with graphene and graphene oxide: Interfacial interaction and nonlinear elastoplastic behavior

Nonlinear elastoplastic behavior of the nanocomposites based on the styrene–acrylonitrile/carboxylated acrylonitrile butadiene rubber (SAN/XNBR) blend was investigated using experimental and theoretical analysis. Graphene, graphene oxide nanoparticles, and glycidyl methacrylate-grafted-XNBR (XNBR-g-GMA) as a compatibilizer were incorporated in the SAN/XNBR blends. In this regard, the focus of this study is on modeling of the stress–strain behavior of these nanocomposites, considering the effect of the interfacial interactions made by compatibilizer. For this purpose, field emission scanning electron microscopy (FESEM) and transmission electron microscope (TEM) techniques were used to investigate the relationship between microstructure and mechanical properties of nanocomposites. In addition, FESEM and TEM images showed that the presence of a compatibilizer could influence the dispersion and localization of the nanoparticles. According to the tensile test results, the presence of the compatibilizer increased the mechanical properties of the nanocomposites, specifically elongation at break. Considering the nanocomposite containing compatibilizer and graphene oxide, the elongation at break increased about 570% compared with the nanocomposite without compatibilizer. Better dispersion of graphene oxide and the creation of chemical interaction among components in the presence of the XNBR-g-GMA compatibilizer could be the reasons for these improvements, as confirmed by TEM. The usage of the Bergstrom–Boyce model for analyzing the nonlinear elastoplastic behavior of the nanocomposites illustrated proper conformity with the experimental data in the elastic region. However, there are some deviations in the viscoplastic region, particularly close to the breaking elongation region.     

Compatibilizer/graphene/carboxylated acrylonitrile butadiene rubber (XNBR)/ethylenepropylenediene monomer (EPDM) nanocomposites: Morphology,compatibility, rheology and mechanical properties

In this study, nanocomposites based on different blends of XNBR/EPDM with 0, 0.1, 0.3, 0.5, 0.7, and 1 phr graphene were prepared on a two-roll mill. The role of EPDM-grafted maleic anhydride compatibilizer (EPDM-g-MAH) and the effect of graphene on morphology, curing characteristics, and mechanical properties were investigated. The curing behavior of the nanocomposites was studied using a rubber curing rheometer. Also, microstructure of the nanocomposites was observed by transmission electron microscopy and scanning electron microscopy. With increasing the graphene content in the composite, in addition to the torque, the curing time and scorch time were increased. Fracture surface morphological studies indicated that the presence of EPDM-g-MAH improved the graphene dispersion within the XNBR/EPDM matrix and a uniform dispersion with a small amount of aggregation was observed. On the other hand, the presence of graphene in the matrix created a rough fracture surface. In addition, with adding EPDM-g-MAH compatibilizer and increasing the graphene, the dispersed phase size of EPDM in the XNBR matrix became smaller and a uniform dispersion was obtained. Also, hardness, tensile strength, fatigue, modulus, and elongation-at-break of XNBR/EPDM nanocomposite showed a significant increase by the addition of compatibilizer and increasing the graphene content.     

Enhancement of thermal,morphological, and mechanical properties of compatibilized based on PA6-enriched graphene oxide/EPDM-g-MA/CR: Graphene oxide and EPDM-g-MA compatibilizer role

In this study, a series of elastomeric nanocomposites based on specific amounts of polyamide6 (PA6)/chloroprene rubber (CR) blends which are compatibilized with ethylene propylene diene monomer-grafted-maleic anhydride (EPDM-g-MA) and different amounts of graphene oxide (GO) were prepared with melt mixing method. The effect of compatibilizer and reinforcement concentration in the PA6/CR blend matrix was investigated using theoretical and experimental analysis. Dispersion of nanoplatelets within rubber blend matrix was proven with transmission electron microscopy and field emission-scanning electron microscopy. The modified microstructure of samples showed the significant effect of EPDM-g-MA and GO on the size reduction of CR droplets in the PA6 continuous phase. The results from differential scanning calorimetry and dynamic mechanical thermal analysis revealed the effect of EPDM-g-MA and GO as an effective nucleating agent in PA6-enriched GO/CR (PA6EGO/CR). The findings obtained from thermogravimetric analysis displayed that the GO in the presence of an EPDM-g-MA as a compatibilizer can cause a higher thermal stability in PA6EGO/CR. From mechanical properties, by adding a compatibilizer to the PA6/CR blend, the tensile strength changed from 39.0 to 45.1, the Young's modulus altered from 522.2 to 716.0 and the elongation at break changed from 246.8 to 222.2. While incorporation of 5 phr of GO to the compatibilized blend, the tensile strength increased by 25.2%, the Young's modulus increased by 36.6% and the elongation at break decreased by 20%. The Christensen–Lo model used for analyzing the stiffness of PA6EGO/EPDM-g-MA/CR with emphasis on the influence of the interphase region to predict the effect of various loadings of GO and EPDM-g-MA of Young's modulus. The rheology and creep tests showed a significant effect of EPDM-g-MA and GO content on the rheology behavior of nanocomposites.     

Localization of different types of organoclay montmorillonite in the compatibilized polyamide 6/carboxylated acrylonitrile butadiene rubber nanocomposites: Morphology and rheological properties

In this study, nanocomposites based on polyamide 6/carboxylated acrylonitrile butadiene rubber (PA6/XNBR) reinforced by the clay montmorillonite (OMMT) (Cloisite 20A and Cloisite 30B) were prepared by melt mixing. Glycidyl methacrylate-grafted XNBR (XNBR-g-GMA) compatibilizer was used for immiscible blends of PA6/XNBR. The results illustrated that OMMT wanted to be selectively present in the more hydrophilic PA6 phase. Also, by adding the XNBR-g-GMA compatibilizer and increasing OMMT content, tensile strength, rheological and dynamic mechanical properties of the nanocomposites improved. According to transmission electron microscopy (TEM) images, a few layers of OMMT (Cloisite 20A) in the XNBR-g-GMA compatibilizer phase was observed. The results of X-ray diffractometry and TEM analyses demonstrated that the formation of intercalated or exfoliated structures for both types of OMMT nanocomposites. In end of all analysis was found PA6/XNBR reinforced by the Cloisite 30B could be substantially improved by adding XNBR-g-GMA as a compatibilizer when compared to those reinforced by Cloisite 20A.     

Preparation and Characterization of Polyvinylpyrrolidone/ Magnetite Decorated Carboxylic Acid Functionalized Multi-walled Carbon Nanotube (PVP/MWCNT-Fe<Subscript>3</Subscript>O<Subscript>4</Subscript>) Nanocomposite

Magnetite decorated carboxylic acid functionalized multi-walled carbon nanotube (MWCNT-Fe₃O₄) was successfully inserted in polyvinylpyrrolidone (PVP) matrix in the aqueous media, as a result of which magnetic polymer nanocomposite (PVP/MWCNT-Fe₃O₄) was formed. With application of SEM, the surface morphology of the produced PVP/MWCNT-Fe₃O₄ nanocomposite was compared with that of pure PVP. The diameter distribution of Fe₃O₄ decorated carboxylic acid functionalized multi-walled carbon nanotube was determined by image analysis of the SEM micrographs. In addition, the structural and thermal characterizations of PVP/MWCNT-Fe₃O₄ nanocomposite were performed by FT-IR, XRD, TGA, and DSC techniques. Moreover, magnetic characterization of the prepared nanocomposite was determined by VSM. The obtained results indicated that addition of MWCNT-Fe₃O₄ (5% w/w) to PVP improved the thermal properties of pure polyvinylpyrrolidone. According to the results of DSC analysis, the glass transition temperature of 160?°C was observed for the PVP/MWCNT-Fe₃O₄ (5% w/w) nanocomposite. The FT-IR spectra showed that an interaction was taking place between MWCNT-Fe₃O₄ and PVP. The strong interaction with ~31 cm^?1 red shift along with good complexation of carbonyl functional group of PVP with MWCNT-Fe₃O₄ was observed for PVP/MWCNT-Fe₃O₄ (5% w/w) nanocomposite as a result of a better distribution of carbon nanotubes in the PVP matrix.