Tough hyperbranched epoxy/poly(amido‐amine) modified bentonite thermosetting nanocomposites

A tough and highly flexible hyperbranched epoxy and poly(amido‐amine) modified bentonite based thermosetting nanocomposite was demonstrated. The FTIR, XRD, and TGA analyses confirmed the modification of bentonite. The formation of partially exfoliated structure of the nanocomposite with good physicochemical interactions among the hyperbranched epoxy, poly(amido‐amine) hardener and modified clay was investigated by the FTIR, XRD, SEM, and TEM analyses. Significant improvements of 750% toughness, 300% elongation at break, 50% tensile strength, 300% modulus, and 250% adhesive strength of the pristine epoxy were achieved by the formation of nanocomposites with 3 wt % of modified clay. The experimental modulus values of the nanocomposites were compared with three theoretical models to account the interactions between filler and matrix. Thus, the studied epoxy nanocomposite has great potential to be used as an advanced epoxy thermoset. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40327.     

An epoxy‐ended hyperbranched polymer as a new modifier for toughening and reinforcing in epoxy resin

A new epoxy‐ended hyperbranched polyether (HBPEE) with aromatic skeletons was synthesized through one‐step proton transfer polymerization. The structure of HBPEE was confirmed by Fourier transform infrared spectroscopy (FTIR), and nuclear magnetic resonance (NMR) measurements. It was proved to be one high efficient modifier in toughening and reinforcing epoxy matrix. In particular, unlike most other hyperbranched modifiers, the glass transition temperature (T_g) was also increased. Compared with the neat DGEBA, the hybrid curing systems showed excellent balanced mechanical properties at 5 wt % HBPEE loading. The great improvements were attributed to the increased cross‐linking density, rigid skeletons, and the molecule‐scale cavities brought by the reactive HBPEE, which were confirmed by dynamical mechanical analysis (DMA) and thermal mechanical analysis (TMA). Furthermore, because of the reactivity of HBPEE, the hybrids inclined to form a homogenous system after the curing. DMA and scanning electron microscopy (SEM) results revealed that no phase separation occurred in the DGEBA/HBPEE hybrids after the introduction of reactive HBPEE. SEM also confirmed that the addition of HBPEE could enhance the toughness of epoxy materials as evident from fibril formation. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 1064‐1073, 2013     

Polyaniline–organoclay nanocomposites as curing agent for epoxy: Preparation and characterization

Polyaniline (PANI)–organoclay/Epoxy (EP) nanocomposites were prepared. PANI–organoclay nanocomposites were used as curing agent for EP. Organoclay was prepared by an ion exchange process between sodium cations in MMT and NH₃⁺ groups in polyoxypropylene (D₂₃₀). PANI–organoclay nanocomposite was synthesized by in situ polymerization of aniline in (14 wt%) organoclay. Infrared spectra and differential scanning calorimetry confirm the curing of EP. The absence of d₀₀₁ diffraction band of organoclay in the nanocomposites was observed by X‐ray diffraction. The structure argument was further supported by scanning electron microscopy and transmission electron microscopy. Electrical conductivity of the nanocomposites within the range 2.1 × 10⁻⁷–3.2 × 10⁻⁷ S/cm depending on the concentration of the PANI/D₂₃₀‐MMT. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers     

New hyperbranched polyether containing cyclic carbonate groups as a toughening agent for epoxy resin

Hyperbranched polyglycerol containing terminal five-membered cyclic carbonate groups has been obtained by anionic polymerization of glycidol and then in the reaction of its terminal vicinal hydroxyl groups with dimethyl carbonate in the presence of potassium carbonate. The remaining OH groups of the polymer were protected in the reaction with acetic anhydride to reduce polymer hydrophilicity and increase miscibility with the epoxy resin. A strong decrease in viscosity was observed after esterification, from 73 to 3.6 Pa s. The product (HBPG 3) was used for modification of the bisphenol A based epoxy resin. The epoxide-cyclic carbonate compositions were cured using a polyamine hardener (TETA) in a one-step procedure. Thermal and mechanical properties of the cured compositions were characterized and compared with the parent epoxy resin. The optimal mechanical properties were obtained for the compositions containing HBPG 3 when phase separation takes place. The mechanical properties are discussed in terms of the morphology observed by SEM.     

Poly(ethyleneterephthalate) glycolysates as effective toughening agents for epoxy resin

The potential of poly(ethyleneterephthalate) glycolysates toward improving the energy absorption characteristics of cycloaliphatic epoxy resins has been explored. Microwave‐assisted glycolytic depolymerization of PET was performed in the presence of polyether diols of different molecular weights. The obtained glycolysates were blended with epoxy, and their mechanical properties were studied under both quasi‐static and dynamic conditions. Significant improvements were observed, which were found to depend both on the amount as well as nature of glycolysate. Amine functionalities were introduced at the terminal positions of glycolysates to improve the compatibility between the two phases. The amine derivatives exhibited superior performance and the Mode I fracture toughness (K_IC) of epoxy increased by ～18% in optimized compositions, which is indicative of its improved notch sensitivity. Neat epoxy specimens fractured in a brittle fashion, but all the blends exhibited ductile failure, as evidenced by surface morphological investigations. The mechanical properties of epoxy blends prepared with analogous aliphatic polyols, both before and after amine functionalization, were also studied which clearly reveal the beneficial role of aromatic groups toward improving the toughness of the base cycloaliphatic epoxy resin without compromising on the material stiffness. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39941.     

Preparation and characterization of poly(styrene‐co‐butadiene) and polybutadiene rubber/clay nanocomposites

Poly(styrene‐co‐butadiene) rubber (SBR) and polybutadiene rubber (BR)/clay nanocomposites have been prepared. The effects of the incorporation of inorganically and organically modified clays on the vulcanization reactions of SBR and BR were analysed by rheometry and differential scanning calorimetry. A reduction in scorch time (t_s1) and optimum time (t₉₅) was observed for both the rubbers when organoclay was added and this was attributed to the amine groups of the organic modifier. However, t_s1 and t₉₅ were further increased as the clay content was increased. A reduction in torque value was obtained for the organoclay nanocomposites, indicating a lower number of crosslinks formed. The organoclays favoured the vulcanization process although the vulcanizing effect was reduced with increasing clay content. The tensile strength and elongation of SBR were improved significantly with organoclay. The improvement of the tensile properties of BR with organoclay was less noticeable than inorganic‐modified clay. Nevertheless, these mechanical properties were enhanced with addition of clay. The mechanical properties of the nanocomposites were dependent on filler size and dispersion, and also compatibility between fillers and the rubber matrix. Copyright © 2004 Society of Chemical Industry     

酚醛改性脂肪胺环氧树脂固化剂的性能研究

用酚醛改性脂肪胺(乙二胺、二乙烯三胺)与聚醚胺作为混合固化剂固化环氧树脂,研究了聚醚胺的用量对环氧树脂凝胶时间、冲击韧性以及粘接性能的影响;并通过测试钢-钢拉剪强度研究了此结构胶粘剂的耐湿热老化性能。实验结果表明,随着聚醚胺用量的增加,环氧树脂固化体系的凝胶时间增长,树脂浇铸体的冲击韧性明显提高,粘接强度先提高再降低,最高值达到16.2 MPa;随着湿热老化时间的增加,环氧树脂固化体系的粘接性能逐渐降低。     

Microcellular poly(hydroxybutyrate‐co‐hydroxyvalerate)‐hyperbranched polymer–nanoclay nanocomposites

The effects of incorporating hyperbranched polymers (HBPs) and different nanoclays [Cloisite® 30B and halloysite nanotubes (HNT)] on the mechanical, morphological, and thermal properties of solid and microcellular poly(hydroxybutyrate‐co‐hydroxyvalerate) (PHBV) were investigated. According to the X‐ray diffraction (XRD) and transmission electron microscopy (TEM) analyses, Cloisite 30B exhibited a combination of exfoliation and heterogeneous intercalation structure for both solid and microcellular PHBV–12% HBP–2% Cloisite 30B nanocomposites. TEM images indicated that HNTs were uniformly dispersed throughout the PHBV matrix. The addition of 2% nanoclays improved the thermal stability of the resulting nanocomposites. The addition of HBP+poly(maleic anhydride‐alt‐1‐octadecene) (PA), Cloisite 30B, and HNT reduced the average cell size and increased the cell density of the microcellular components. The addition of (HBP+PA), Cloisite 30B, and HNT also increased the degree of crystallinity for both solid and microcellular components in comparison with neat PHBV. Also, with the addition of 12% (HBP+PA), the area under the tan‐δ curve, specific toughness, and strain‐at‐break of the PHBV–HBP nanocomposite increased significantly for both solid and microcellular specimens, whereas the storage modulus, specific Young's modulus, and specific tensile strength decreased. The addition of 2% nanoclays into the PHBV–HBP nanocomposites improved the storage modulus, specific Young's modulus, and specific tensile strength of the PHBV–HBP–nanoclay‐based nanocomposites, but they were still lower than those of the neat PHBV. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers     

Poly(urethane‐co‐vinyl imidazole)/graphene nanocomposites

Poly(urethane‐co‐vinyl imidazole) (PUVI)/graphene nanocomposites were facilely prepared by a kind of noncovalent way. Herein, the 1‐vinylimidazole acted as dispersion agent as well as monomer, graphene was uniformly dispersed in the copolymer matrix without obviously agglomeration. A significant enhancement of mechanical and thermal properties of the PUVI/graphene nanocomposites were obtained at low graphene loading; specifically, a 147% improvement of tensile strength, a nearly 10 times increase of elastic modulus and a 12°C enhancement of thermal decomposition temperature were achieved at a graphene loading of 1.5 wt%. Moreover, the volume resistivity of the PUVI/graphene nanocomposites decreased by an order of magnitude after adding 0.5 wt% graphene, demonstrating an obvious change in the electrical property of the nanocomposites prepared. POLYM. COMPOS. 2012. © 2012 Society of Plastics Engineers     

Spray‐dried microspheres as a route to clay/polymer nanocomposites

A new strategy for the preparation of well‐dispersed clays in a polymer matrix by a spray‐drying method is presented. Scanning electron microscopy and transmission electron microscopy measurements show that the spray‐drying process produces clay/polymer microspheres in which the clay is trapped in a well‐dispersed state throughout the polymer matrix. The microspheres have been successfully extruded into clay/poly(methyl methacrylate) nanocomposite bulk structures without any perturbation of the well‐dispersed clay nanostructure in the original microspheres. Transmission electron microscopy and small‐angle X‐ray scattering show that the clay particles in the extruded materials range from single platelets to simple tactoids composed of a few stacked clay platelets, indicating an excellent degree of dispersion. The results show that sprayed microspheres are very good precursors for further processing such as extrusion or melt blending with other polymers for bulk nanocomposite fabrication. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Poly(ethylene‐vinyl co‐vinyl acetate)/clay nanocomposites: Mechanical,morphology, and thermal behavior

Nanocomposites of ethylene‐vinyl acetate copolymer (EVAL) with Dellite organoclay were prepared in a laboratory extruder. The extent of intercalation of the nanocomposites was studied by field emission scanning electron microscopy and X‐ray diffraction. It was established that the organoclay is well dispersed and preferentially embedded in the EVAL phase. Further, the intercalation degree of the organoclay decreased with increasing organoclay content. The mechanical properties of the nanocomposites were studied as a function of clay loading and EVAL type. The nanocomposites exhibited enhanced thermal stability as seen in thermogravimetric studies. POLYM. COMPOS., 2011. © 2010 Society of Plastics Engineers     

Reactive core/shell type hyperbranched blockcopolyethers as new liquid rubbers for epoxy toughening

Novel reactive core/shell-type hyperbranched blockcopolyethers were tailored as new class of liquid rubbers useful as flexibilizers and toughening agents of anhydride-cured epoxy resins. Anionic ring-opening polymerization of glycidol onto a six-arm star poly(propylene oxide-block-ethylene oxide) afforded hyperbranched polyether cores as macroinitiators for propylene oxide graft copolymerization. The hydroxy end groups of the resulting polyether-polyols have been modified in order to prepare stearate, hydroxy benzoate and epoxy derivatives. The modification afforded reactivity and polarity design which has been the key to improved blend performance with epoxy resins. In comparison to conventional hyperbranched epoxy-terminated polyesters, the influence of molecular architectures on thermal, mechanical and morphological properties of hexahydrophthalic acid anhydride-cured bisphenol-A diglycidylether was examined. As a function of polarity and reactivity design, it was possible to control phase separation and to vary mechanical properties from highly flexible to stiff and tough.     

Effect of clay on the properties of poly(styrene‐co‐acrylonitrile)–clay nanocomposites

Clay‐dispersed poly(styrene‐co‐acrylonitrile) nanocomposites (PSAN) were synthesized by a free radical polymerization process. The montmorillonite (MMT) was modified by a cationic surfactant hexadecyltrimethylammonium chloride. The structures of PSAN were determined by wide‐angle X‐ray diffraction and FTIR spectroscopy. The dispersion of silicate layers in the polymer matrix was also revealed by transmission electron microscopy (TEM). It was confirmed that the clay was intercalated and exfoliated in the PSAN matrix. The increased thermal stability of PSAN with the addition of clay was observed by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The dielectric properties of PSAN were measured in the frequency range 100 Hz to 1 MHz at 35–70°C. It was found that the dielectric constant from the dipole orientation had been suppressed due to the intercalation of clay. The dielectric loss is strongly related to the residual sodium content of clay, which increases as the sodium content increases by the addition of clay. Copyright © 2004 Society of Chemical Industry     

Poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate)/clay nanocomposites for replacement of mineral oil based materials

Due to the short‐running of mineral oil and the increasing waste problem, biopolymers become more and more important. However, they still suffer from disadvantages, and in many cases, their properties are still insufficient to replace mineral oil based plastics. In this study, the biobased and biodegradable polymer poly (3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) (PHBV) is reinforced by different clay types and their effect on the properties profile is investigated. Natural as well as organomodified montmorillonite and bentonite are dispersed by melt mixing within the PHBV matrix. Thermal stability, crystallization behavior, and dynamic mechanical properties as well as the materials morphology is analyzed. Dispersion state of the nanoclay is found to be crucial for the improvement of the material performance and well dispersed organomodified clays reveal to simultaneously improve different properties of PHBV matrix. POLYM. COMPOS., 34:1033–1040, 2013. © 2013 Society of Plastics Engineers     

Poly(ethylene oxide)/clay nanocomposites for solid polymer electrolyte applications

Poly(ethylene oxide) (PEO)/clay nanocomposites were prepared using a solution intercalation method. The organoclay (Nanocore I30E) used for nanocomposite synthesis was basically an octadecylammonium salt of montmorillonite clay prepared using an ion exchange method. Nanocomposite‐based solid polymer electrolytes were prepared using LiBF₄. The nanocomposite structures were characterised using wide‐angle X‐ray diffraction. The crystallisation behaviour and thermal properties were studied using differential scanning calorimetry. It was found that the crystallinity of the composite electrolytes decreases with increasing clay concentration up to 7.5 wt% and then increases with a further increase in clay concentration. The trend is different from that observed in PEO/clay nanocomposites without lithium salt where the crystallinity gradually decreases with increasing clay concentration. The solid polymer electrolyte samples were evaluated using an alternating current impedance analyser. A considerable increase in room temperature conductivity was observed at the optimum clay concentration. The conductivity decreases beyond the optimum clay concentration. Copyright © 2007 Society of Chemical Industry     

Poly(ethylene terephthalate)/poly(ethylene glycol‐co‐1,3/1,4‐cyclohexanedimethanol terephthalate)/clay nanocomposites: Effects of biaxial stretching

In this study, we fabricated poly(ethylene terephthalate) (PET)/clay, PET/poly(ethylene glycol‐co‐1,3/1,4‐cyclohexanedimethanol terephthalate) (PETG), and PET/PETG/clay nanocomposite plates and biaxially stretched them into films by using a biaxial film stretching machine. The tensile properties, cold crystallization behavior, optical properties, and gas and water vapor barrier properties of the resulting films were estimated. The biaxial stretching process improved the dispersion of clay platelets in both the PETG and PET/PETG matrices, increased the aspect ratio of the platelets, and made the platelets more oriented. Thus, the tensile, optical, and gas‐barrier properties of the composite films were greatly enhanced. Moreover, strain‐induced crystallization occurred in the PET/PETG blend and in the amorphous PETG matrix. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42207.     

Nonisothermal crystallization of poly(ethylene‐co‐glycidyl methacrylate)/clay nanocomposites

The nonisothermal crystallization of poly(ethylene‐co‐glycidyl methacrylate) (PEGMA) and PEGMA/clay were studied by differential scanning calorimeter, at various cooling rates. Avrami model modified by Jeziorny, Ozawa mode and Liu model could successfully describe the nonisothermal crystallization process. Augis–Bennett model, Kissinger model, Takhor model, and Ziabicki model were used to evaluate the activation energy of both samples. It was found that the activation energy of PEGMA/clay nanocomposite was higher than that of neat PEGMA. Experimental results also indicated that the addition of modified clay might retard the overall nonisothermal crystallization process of PEGMA. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 1335–1343, 2006     

Isothermal crystallization of poly(ethylene‐co‐glycidyl methacrylate)/clay nanocomposites

Poly(ethylene‐co‐glycidyl methacrylate) (PEGMA)/clay nanocomposites with clay concentrations of 1, 3, or 5 wt % were prepared via y melt blending in a twin‐screw extruder. Wide‐angle X‐ray diffraction showed that the clay layers were intercalated by PEGMA. Differential scanning calorimetry was used to analyze the isothermal crystallization, and the equilibrium melting temperature was determined with the Hoffman–Weeks method. The Avrami, Tobin, Malkin, and Urbanovici–Segal models were applied to describe the kinetics of crystallization from the melt state under isothermal conditions. The crystallization kinetics showed that the addition of clay facilitated the crystallization of PEGMA, with the clay functioning as a heterophase nucleating agent; at higher concentrations, however, the physical hindrance of the clay layers to the motion of PEGMA chains retarded the crystallization process. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 1051–1064, 2005     

Morphology and thermal behavior of organo‐bentonite clay/poly(styrene‐co‐methacrylic acid)/poly(isobutyl methacrylate‐co‐4‐vinylpyridine) nanocomposites

Poly(styrene‐co‐methacrylic acid) containing 29 mol % of methacrylic acid (SMA‐29) and poly(isobutyl methacrylate‐co‐4‐vinylpyridine) containing 20 mol % of 4‐vinylpyridine (IBM4VP‐20) were synthesized, characterized, and used to elaborate binary and ternary nanocomposites of different ratios with a 3% by weight hexadecylammonium‐modified bentonite from Maghnia (Algeria) by casting method from tetrahydrofuran (THF) solutions. The morphology and the thermal behavior of these binary and ternary elaborated nanocomposites were investigated by X‐ray diffraction, scanning electron microscopy, FTIR spectroscopy, differential scanning calorimetry, and thermogravimetry. Polymer nanocomposites and nanoblends of different morphologies were obtained. The effect of the organoclay and its dispersion within the blend matrix on the phase behavior of the miscible SMA29/IBM4VP20 blends is discussed. The obtained results showed that increasing the amount of SMA29 in the IBM4VP20/SMA29 blend leads to near exfoliated nanostructure with significantly improved thermal stability. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009