Morphology evolutions of organically modified montmorillonite/polyamide 12 nanocomposites

Organically modified montmorillonites (OMMTs) by octadecylammonium chloride with two adsorption levels were dispersed in polyamide 12 (PA12) matrices with two molecular weights for different melt mixing times in order to investigate morphology evolutions and factors influencing fabrication of PA12 nanocomposites. Different adsorption levels of the modifier in the OMMTs provide different environments for diffusion of polymer chains and different attractions between MMT layers. Wide-angle X-ray diffraction (WAXD), transmission electron microscope (TEM) and gas permeability were used to characterize morphologies of the nanocomposites. Both OMMTs can be exfoliated in the PA12 matrix with higher molecular weight, but only OMMT with lower adsorption level can be exfoliated in the PA12 matrix with lower molecular weight. It was attributed to the differences in the levels of shear stress and molecular diffusion in the nanocomposites. The exfoliation of OMMT platelets results from a combination of molecular diffusion and shear. After intercalation of PA12 into interlayer of OMMT in the initial period of mixing, further dispersion of OMMTs in PA12 matrices is controlled by a slippage process of MMT layers during fabricating PA12 nanocomposites with exfoliated structure.     

Morphology,mechanical property,and processing thermal stability of PVC/La‐OMMTs nanocomposites prepared via in situ intercalative polymerization

Poly(vinyl chloride) (PVC) nanocomposites were prepared via an in situ intercalative suspension polymerization of vinyl chloride with four organic carboxylic acid salts (montmorillonite [MMT] units) containing thermally stable lanthanum ions. The effects of different lanthanum organic montmorillonites (La‐OMMTs) on the particle features and molecular weight were investigated. The transmission electron microscopy data indicated the formation of partially exfoliated or intercalated PVC/La‐OMMTs nanocomposites. The effect of different functional groups on the mechanical properties and processing thermal stability of PVC/La‐OMMT nanocomposites were investigated. Tensile testing and two‐roll mill processing results showed that La‐OMMTs could enhance the dynamic thermal stability and mechanical properties versus PVC pure resin and PVC/I.30P nanocomposites (composed of PVC and I.30P). This suggested that the double bond and amidogen group in La‐OMMTs could promote the dispersion of La‐OMMTs in the PVC matrix and also improve the adhesion between the La‐OMMTs and PVC matrix. The results have potential value in the industrial development of PVC/La‐OMMTs nanocomposites. J. VINYL ADDIT. TECHNOL., 26:97–108, 2020. © 2019 Society of Plastics Engineers     

有机蒙脱土/热塑性聚氨酯的制备及对性能的影响

以Gemini双阳离子表面活性剂插层钠基蒙脱土制备了具有不同层间距的有机蒙脱土(OMMT)并用于热塑性聚氨酯(TPU)的改性,考察了OMMT的层间距及用量对该纳米复合材料的热性能和力学性能的影响.DSC结果表明,随着OMMT层间距的增大,软段Tg升高,硬段Tg降低.力学性能结果表明,OMMT的层间距越大,力学性能越好,...     

Thermal degradation kinetics of epoxy/organically modified montmorillonite nanocomposites

Nanocomposites based on a commercial epoxy resin and organically modified montmorillonites (OMMTs), containing 5 and 10 phr OMMT, were prepared and characterized. Poly(oxypropylene) diamine (Jeffamine D400) and octadecylamine were used as organic modifiers. Another poly(oxypropylene) diamine (Jeffamine D230) was used as a curing agent. The thermal degradation kinetics of the neat resin system and nanocomposites were investigated by thermogravimetric analysis. The dispersion of silicate layers within the crosslinked epoxy matrix was verified by transmission electron microscopy. The activation energy of degradation for the investigated systems was determined by the isoconversional Kissinger–Akahira–Sunose method. The thermal behavior of the neat resin systems and nanocomposites was modeled with an empirical kinetic model. The influence of organic modifiers and the OMMT loading on the thermal stability of the nanocomposites was discussed. © 2007 Wiley Periodicals, Inc. JAppl Polym Sci, 2008     

Effect of OMMTs on flame retardancy and thermal stability of poly(ethylene‐co‐vinyl acetate)/LDPE/magnesium hydroxide composites

The aim of this study was to prepare poly (ethylene‐co‐vinyl acetate) (EVA)/ low density polyethylene (LDPE)/magnesium hydroxide (MH) composites applicable in cable industry with required flame retardancy. For this reason, two types of organo‐modified montmorillonites (OMMT) with different surface polarites (Cloisite 15A and Cloisite 30B) at various concentrations, and also combination of these two OMMTs with overall loadings of 2 wt % and 5 wt % were used. The samples were compounded using a twin screw extruder with total (MH + OMMT) feeding of 55 wt % and 60 wt %. Limiting oxygen index (LOI) of the samples containing 2 wt % of OMMTs increased about 16% and dripping was suppressed according to vertical burning test (UL‐94V). Thermogravimetric results of EVA/LDPE/MH samples containing OMMT showed that the beginning of second step degradation was shifted about 50°C to higher temperatures. The composite tensile strength results showed enhancement by incorporating some amount of nanoclays with EVA/LDPE/MH composites. Scanning electron microscopy images confirmed that MH particles had better wetting by EVA matrix in presence of nanoclays. Oxidative induction time of the EVA/LDPE/MH/OMMT nanocomposites was 140 min, which was more than that of the samples without OMMT (20 min). Employing the equal weight ratios of the two OMMTs demonstrated a synergistic effect on flame retardancy of the samples according to the both tests results (LOI, UL‐94V). X‐ray diffraction analysis of the samples confirmed the intercalation/semiexfoliation structure of nanosilicate layers in the bulk of EVA/LDPE matrix. This led to longer elongation at break and thermal stability of Cloisite 15A based nanocomposites. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40452.     

Mechanical properties,flame retardancy,and smoke suppression of lanthanum organic montmorillonite/poly(vinyl chloride) nanocomposites

A dimethyl dioctadecyl ammonium chloride modified organic montmorillonite (OMMT_‐I.44P)/poly(vinyl chloride) (PVC) nanocomposite and anionic‐surfactant‐modified lanthanum organic montmorillonite (La‐OMMT)/PVC nanocomposites (with three different anionic surfactants for the La‐OMMTs) were prepared via melt‐intercalation technology. The effects of the La‐OMMTs and OMMT_‐I.44P on the mechanical properties, flame retardancy, and smoke suppression of PVC were studied. X‐ray diffraction characterization showed that the La‐OMMTs were exfoliated in the PVC matrix. The mechanical properties of the nanocomposites were enhanced by the incorporation of the La‐OMMTs. Cone calorimetry and gas chromatography–mass spectrometry analyses indicated that the incorporation of the La‐OMMTs enhanced the flame retardancy and smoke suppression of the PVC nanocomposites. Scanning electron microscopy photos further showed that the residual char surfaces of La‐OMMT/PVC were all intact and, thus, provided better barriers to energy and smoke transport. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43951.     

Effect of OMMT on microstructure,crystallisation and rheological behaviour of UHMWPE/PP nanocomposites under elongation flow

Different loadings of organo-montmorillonite (OMMT) were mixed with ultra-high molecular weight polyethylene (UHMWPE)/polypropylene (70/30) composites under elongation flow. Results showed that ideal dispersion of OMMT nanoparticles could be achieved and most OMMTs intercalated and exfoliated effectively. However, the layer spacing of OMMT decreased with the increase in the content of OMMT. UHMWPE was surrounded by the OMMT layers, and its shape evolved from a compatible phase to a sphere. OMMT caused heterogeneous nucleation in the blends, leading to a high crystallisation temperature. Meanwhile, the intercalated and exfoliated OMMTs promoted the motion of polymer chains, and inhibited the crystallisation process of UHMWPE in the composites. The crystallinity of UHMWPE with 5% OMMT markedly decreased from 48.39% to 41.46%. Various rheological analyses confirmed that the complex viscosity of composites and the storage modulus decreased first and then increased with the increase in the content of OMMT. UHMWPE/PP with 5% OMMT exhibited the ideal mobility.     

Effect of POSS on morphology and mechanical properties of polyamide 12/montmorillonite nanocomposites

Sodium-montmorillonite (MMT) was modified with two types of AP-POSS and OA-POSS and dual-surfactants (POSS with a ditallow-based second surfactant: 04AP-POSS/08DTDMA and 04OA-POSS/08DTDMA), respectively, via ion-exchange reaction. The interlayer space, interlamellar structure, thermal and surface properties of these organo-montmorillonites were investigated by X-ray diffraction, thermogravimetric analysis, and contact angle measurement. The interlayer space of POSS modified clay was strongly dependent on the arrangement of POSS surfactants, but less on the POSS concentration. The POSS modified montmorillonites have partially exchanged silicate surfaces and good thermal stabilities due to steric hindering and thermal stability of the POSS molecules. Dual-surfactant modified montmorillonites showed higher exchange ratio and possessed better compatibility with PA12 due to the lower interfacial free energy. Polyamide 12-montmorillonite nanocomposites were prepared by conventional melt compounding with the four POSS based organo-montmorillonites. The best dispersion of modified montmorillonite was observed for 3 mass% 04AP-POSS/08DTDMA/MMT filled PA12 nanocomposites, which resulted in the best mechanical performance with an increase of 60% in tensile modulus and 10% in yield strength, respectively, compared to that of pure PA12. Compatibility between montmorillonites and polymer was not the only key factor affecting dispersion, thermal stability and interlayer space were also crucial for good dispersion of montmorillonites in polymer matrix.     

硅橡胶/有机改性蒙脱土纳米复合材料的性能研究

用熔体插层法制备甲基乙烯基硅橡胶(MVQ)/有机改性蒙脱土(OMMT)纳米复合材料并研究其微观结构和性能。结果表明:OMMT改性剂疏水性从优到劣的顺序为I.44P,I.30P,Bengel434,I.44P和I.30P在MVQ中的分散性优于Bengel434;MVQ/OMMT纳米复合材料的物理性能和热稳定性从优到劣的顺序为MVQ/I.44P,MVQ/I.30P,MVQ/Bengel434纳米复合材料;添加40份I.44P的MVQ/I.44P纳米复合材料的100%定伸应力、拉伸强度和撕裂强度比纯胶有较大提高。     

Structural and ordering behavior of lamellar polystyrene‐block‐polybutadiene‐block‐polystyrene triblock copolymer containing layered silicates

Nanocomposites based on organically modified montmorillonites (OMMTs) and sodium montmorillonite (CLO‐Na⁺) with poly(styrene‐b‐butadiene‐b‐styrene) (SBS) diblock copolymer have been investigated. Solution blending of OMMT suspension in toluene with SBS and subsequent static casting and annealing resulted in transparent films. Final samples were processed by compression molding. The intercalation spacing in the nanocomposites, microphase separation of the SBS, and the degree of dispersion of nanocomposites were investigated by X‐ray diffraction (Wide and small‐angle X‐ray scattering), transmission optical microscopy (TOM), atomic force microscopy (AFM), and transmission electron microscopy (TEM). The increase of basal spacing of OMMT in the nanocomposites suggested the intercalation of SBS. The lamellar structure perfection was extensively affected by both OMMT. AFM images and TOM micrographs only showed well dispersed but not exfoliated nanocomposites. On the other hand, TEM showed inserted tactoids into both blocks depending on the surfactant used (stained samples) and the dispersion of those tactoids (unstained samples). Fourier transform infrared spectroscopy indicated only the presence of the OMMT into the SBS. Deviations of the decomposition pathway of pristine SBS with addition of the OMMT were found by thermogravimetric analysis. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

The modification of lanthanum‐exchanged montmorillonite with anionic surfactants to enhance the thermal stability of polyvinyl chloride

A series of thermally stable lanthanum organic montmorillonites (La‐OMMTs) were successfully prepared by modifying Na‐MMT with anionic surfactants and lanthanum chloride. Fourier transform infrared spectroscopy and X‐ray diffraction indicated that the anionic surfactants resided in the interlayer spaces and expanded the MMT basal spacing from 1.23 nm to 3.3 nm. Thermogravimetric and differential thermal analysis (TG/DTA) results showed that the intercalation of sodium dodecyl sulfonate into the lanthanum organic MMT resulted in its excellent thermal stability. The use of the La‐OMMT samples in polyvinyl chloride (PVC) resins was tested, and the TG/DTG results revealed that the three La‐OMMTs could significantly enhance the thermal stability of PVC. The modified La‐OMMT with the highest thermal stability is expected to be useful in polymer/layered silicate nanocomposites. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41535.     

Biodegradable poly(l-lactide)/poly(?-caprolactone)-modified montmorillonite nanocomposites: Preparation and characterization

New nanocomposites were prepared by melt blending poly(l-lactide) (PLLA), poly(?-caprolactone) (PCL), and organically modified montmorillonite (OMMT). The obtained nanocomposites showed enhanced tensile strength, modulus and elongation at break than that of PLLA/PCL blends. The dynamic mechanical analysis showed the increasing mechanical properties with temperature dependence of nanocomposites. Wide-angle X-ray diffraction analysis and transmission electron microscopy indicated that the material formed the nanostructure. Adding OMMT improved the thermal stability and crystalline abilities of nanocomposites. The morphology was investigated by environmental scanning electron microscopy, which showed that increasing content of OMMT reduces the domain size of phase-separated particles. The specific interaction between each polymer and OMMT was characterized by the Flory-Huggins interaction parameter, B, which was determined by the equilibrium melting point depression of nanocomposites. The final values of B showed that PLLA was more compatible with OMMT than PCL.     

Influence of the type of quaternary ammonium salt used in the organic treatment of montmorillonite on the properties of poly(styrene‐co‐butyl acrylate)/layered silicate nanocomposites prepared by in situ miniemulsion polymerization

Hybrid latices of poly(styrene‐co‐butyl acrylate) were synthesized via in situ miniemulsion polymerization in the presence of 3 and 6 wt % organically modified montmorillonite (OMMT). Three different ammonium salts: cetyl trimethyl ammonium chloride (CTAC), alkyl dimethyl benzyl ammonium chloride (Dodigen), and distearyl dimethyl ammonium chloride (Praepagen), were investigated as organic modifiers. Increased affinity for organic liquids was observed after organic modification of the MMT. Stable hybrid latices were obtained even though miniemulsion stability was disturbed to some extent by the presence of the OMMTs during the synthesis. Highly intercalated and exfoliated polymer‐MMT nanocomposites films were produced with good MMT dispersion throughout the polymeric matrix. Materials containing MMT modified with the 16 carbons alkyl chain salt (CTAC) resulted in the largest increments of storage modulus, indicating that single chain quaternary salts provide higher increments on mechanical properties. Films presenting exfoliated structure resulted in the largest increments in the onset temperature of decomposition. For the range of OMMT loading studied, the nanocomposite structure influenced more significantly the thermal stability properties of the hybrid material than did the OMMT loading. The film containing 3 wt % MMT modified with the two 18 carbons alkyl chains salt (Praepagen) provided the highest increment of onset temperature of decomposition. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Effect of Organo-Modified Montmorillonite on the Morphology and Properties of SEBS/TPU Nanocomposites

In this study, novel polystyrene-b-poly(ethylene-butylene)-b-polystyrene (SEBS)/thermoplastic polyurethane (TPU)/organo-modified montmorillonites (OMMT) nanocomposites were prepared by melt mixing. Three different organo-modified montmorillonites, DK2, DK3, and DK4 (listed in descending order of hydrophilicity) were selected. The compatibilizing and reinforcing effects of OMMT on the structure, morphology, thermal stability, mechanical and rheological properties of the SEBS/TPU blends were studied. It was found that the hydrophilic DK2 nanoparticles were largely located in the continuous TPU phase and partially dispersed at the phase interphase, whereas DK3 and DK4 nanoparticles were preferentially located at the phase interface with an intercalated/exfoliated and intercalated structure, respectively. Scanning electron microscopy (SEM) results showed that SEBS/TPU/OMMT nanocomposites exhibited a more densely organized and interconnected structure compared with SEBS/TPU blends. Better thermal property was achieved after adding DK3, with the tensile properties of the SEBS/TPU increased considerably. Rheological analysis revealed that hydrophilic DK2 nanoparticles were more effective in improving rheology properties and showed a more pronounced nonlinear effect. The prepared SEBS/TPU/OMMT nanocomposites displayed desired thermal, mechanical and rheological properties, which are important for many applications. POLYM. ENG. SCI., 60:850–859, 2020. © 2020 Society of Plastics Engineers     

氢化丁腈橡胶/有机蒙脱土纳米复合材料的性能

采用熔体插层法制备了氢化丁腈橡胶/有机蒙脱土纳米复合材料,采用透射电镜和X射线衍射仪对复合材料的结构进行了表征,并研究了复合材料的应力应变行为、耐老化性能、耐溶剂性能和动态力学性能。实验结果表明:制备了一种插层型纳米复合材料,复合材料的耐老化性能和耐溶剂性能良好,并且随蒙脱土含量的增大而增加;动态黏弹谱(DMA)测试显示,纳米复合材料的玻璃化转变温度升高,且具有较低的滚动阻力,复合材料的动态力学性能优良。     

Influence of the clay modification and compatibilizer on the structure and mechanical properties of ethylene–propylene–diene rubber/montmorillonite composites

Ethylene–propylene–diene rubber (EPDM)/montmorillonite (MMT) composites were prepared through a melt process, and three kinds of surfactants with different ammonium cations were used to modify MMT and affect the morphology of the composites. The morphology of the composites depended on the alkyl ammonium salt length, that is, the hydrophobicity of the organic surfactants. Organophilic montmorillonite (OMMT), modified by octadecyltrimethyl ammonium salt and distearyldimethyl ammonium salt, was intercalated and partially exfoliated in the EPDM matrix, whereas OMMT modified by hexadecyltrimethyl ammonium chloride exhibited a morphology in which OMMT existed as a common filler. Ethylene–propylene–diene rubber grafted with maleic anhydride (MAH‐g‐EPDM) was used as a compatibilizer and greatly affected the dispersion of OMMT. When OMMTs were modified by octadecyltrimethyl ammonium chloride and distearydimethyl ammonium chloride, the EPDM/OMMT/MAH‐g‐EPDM composites (100/15/5) had an exfoliated structure, and they showed good mechanical properties and high dynamic moduli. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 638–646, 2004     

UHMWPE/organoclay nanocomposites fabricated by melt intercalation under continuous elongational flow: Dispersion,thermal behaviors and mechanical properties

The preparation of ultra‐high‐molecular weight polyethylene (UHMWPE)/organoclay nanocomposites by continuous elongational flow technique was investigated in a novel eccentric rotor extruder (ERE). The distribution and dispersion morphologies of organo‐modified montmorillonite (OMMT) layers were revealed and observed by ash determination, wide angle X‐ray diffraction and transmission electron microscopy. The thermal and thermal‐mechanical behaviors were characterized by differential scanning calorimeter, thermal gravimetric analysis and dynamic mechanical thermal analysis. The mechanical performances was measured by tensile and impact test. The morphologies of the nanocomposites evidenced that the OMMT layers can be well intercalated or/and exfoliated by UHMWPE matrix, then the fabrication mechanism of intercalated and exfoliated OMMT structures under continuous elongational flow was discussed. The ideal dispersion of OMMT in UHMWPE matrix obviously improved the crystallinity and the mechanical properties at a certain concentration of OMMT loading, indicating that the lower OMMT addition can lead an effective strengthening and toughening for UHMWPE. POLYM. ENG. SCI., 59:547–554, 2019. © 2018 Society of Plastics Engineers     

Effect of Nanoclay on the Mechanical,Thermal, and Water Absorption Properties of an UP-toughened Epoxy Network

Unsaturated polyester (UP)-toughened epoxy nanocomposites were prepared, and their effective mechanical and thermal properties were studied. Two types of organo-modified montmorillonite (OMMT) clays were used to prepare the nanocomposites. X-ray diffraction (XRD) and transmission electron microscopy (TEM) analysis showed the formation of exfoliated silicate layers in the UP-toughened epoxy matrix. Mechanical tests revealed that nanocomposites (containing 1 wt% OMMT clay) showed an increase in tensile strength to 13.8%, flexural strength to 10%, and impact strength to 4% compared with an UP-toughened epoxy blend. The effect of different heating rates on the curing behavior of UP-toughened epoxy nanocomposites was investigated using non-isothermal differential scanning calorimetry. The data were interpreted using the Kissinger and Flynn–Wall–Ozawa models to find the curing reaction parameter. The water uptake behavior for nanocomposites increased with the addition of OMMTs. Scanning electron microscopy micrographs indicated morphological changes in the impact fractured samples of UP-toughened epoxy nanocomposites.     

Reinforcing effect and isothermal crystallization kinetics of poly(3‐hydroxybutyrate) nanocomposites blended with organically modified montmorillonite

Organically modified montmorillonite (OMMT) has been incorporated up to 7 wt% in poly(3‐hydroxybutyrate) (PHB) by melt compounding in a twin screw extruder. PHB nanocomposites reinforced with C93A showed significant increase in tensile and flexural modulus and impact strength comparatively. Wide angle X‐ray diffraction showed an increase in overall d‐spacing indicating intercalated structure. The intercalation morphology was further supported by transmission electron microscope images indicating formation of intercalated structure in case of PHB/OMMT and a mixture of Intercalated/exfoliated structure in case of PHB/TMI‐MMT nanocomposites. Thermogravimetric analyses indicate that the thermal stability of PHB/TMI‐MMT nanocomposites is higher among all other nanocomposites under investigation and virgin PHB. Differential scanning calorimetry (DSC) analysis of PHB nanocomposites shows marginal increase in glass transition temperature and decrease in crystallization temperature compared to virgin PHB. The isothermal crystallization kinetics of PHB/C93A nanocomposites was investigated by DSC in the temperature range of 100–120°C and the development of relative crystallinity with the crystallization time was analyzed by Avrami equation. POLYM. COMPOS., 35:999–1012, 2014. © 2013 Society of Plastics Engineers     

Studies on crystallization behaviors and crystal morphology of polyamide 66/clay nanocomposites

X‐ray diffraction methods, DSC thermal analysis, and polarized light microscopy (PLM) were used to investigate the structural changes of nylon 66/clay nanocomposites. PA 66/clay nanocomposites were prepared by the method of melt intercalation. The results indicate that the addition of the intercalated organo‐montmorillonite (OMMT) can induce generation of the β‐form crystal of PA 66 and substantially affect the arrangement of molecules in the α‐form crystal, although the crystallinity scarcely changes. Also, the DSC results indicate that the addition of OMMT in the PA 66 matrix leads to increases of crystallization temperatures and the full width at half maximum (FWHM) of the exothermic peaks. Moreover, the viscosity factor is the main influence on FWHM of the exothermic peaks of PA 66/clay nanocomposites. The results of nonisothermal crystallization kinetics show that OMMT has the effect of heterogeneous nucleation and leads to the decrease of the size of the spherocrystal. The heterogeneous nucleation effects of OMMTs influence the mechanism of crystallization and the growth mode of PA 66 crystals. PLM photographs verify that the size of spherocrystal is decreased and visually confirm the theory of crystallization kinetics. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 95: 756–763, 2005