Preparation and characterization of organoclay nanocomposites based on natural rubber

Rubber compounds based on natural rubber (NR) reinforced with octadecylamine‐modified bentonite have been prepared via a vulcanization process and characterized by several techniques. The silicate nanolayers are exfoliated and uniformly dispersed in the polymer chains. Monsanto measurements have shown that the organoclay accelerates the vulcanization reaction and, furthermore, gives rise to a marked increase of the torque, indicating that the elastomer becomes more crosslinked in the presence of the organoclay. These results were corrobated by swelling measurements since a noticeable increase in the curing degree was observed when the organoclay was added to the rubber recipe. Moreover, thermodynamic parameters have shown an increase in the structural order of the nanocomposite. In addition, thermal analysis supports the assumption that the degree of curing of the elastomer increases when the organoclay is added to the elastomer. An appreciable increase of the involved heat during the curing reaction has been observed. Moreover, the T_g of the NR increases in the presence of the organoclay due to the confinement of the elastomer segment into the organoclay nanolayers, which restricts the mobility of the chains. Copyright © 2003 Society of Chemical Industry     

Retracted: Preparation and characterization of nitrile rubber/poly(vinyl chloride)/organoclay nanocomposites

Retracted: A. Shokri. Preparation and characterization of nitrile rubber/poly (vinyl chloride)/organoclay nanocomposites, Polymer International. [DOI: 10.1002/pi.2076]. The above article, published online in EarlyView on 13 June 2006, has been retracted for legal reasons.     

Studies of particle dispersion in plasticized poly(vinyl chloride)/montmorillonite nanocomposites

Poly(vinyl chloride)(PVC) and dioctyl phthalate (DOP) were mixed with 5 and 10 wt % of Cloisite Na⁺, Cloisite 30B or Cloisite 93A. The obtained nanocomposites were characterized by thermal analysis using a thermogravimetric analyzer which showed that addition of 5 wt % of nanoclay to PVC increased its thermal stability in the sequence: Cloisite Na⁺< Cloisite 93A< Cloisite 30B. The electrical conductivity of these composites was studied as a function of temperatures and showed that the conductivity of PVC was enhanced upon using 5 wt % of nanoclay in the sequence: Cloisite Na⁺< Cloisite 30B < Cloisite 93A. The activation energy of interaction of PVC with nanoclay was found to be lowest for the composite containing 5 wt % of nanoclay in the same sequence. The tensile strength, elongation (%), and Young's modulus were considerably enhanced upon increasing the clay content to 5 wt % in the sequence: Cloisite Na⁺< Cloisite 93A < Cloisite 30B. X‐ray diffraction (XRD) and scanning electron microscopy (SEM) were used to study these nanocomposite structures, and it was found that the organoclay layers are homogeneously dispersed in the PVC matrix when 5 wt % of Cloisite 30B or Cloisite 93A was used. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Synthesis and properties of poly(ethylene terephthalate)/clay nanocomposites by in situ polymerization

Poly(ethylene terephthalate) (PET)/clay nanocomposites (PCNs) with N‐methyl diethanol amine (MDEA)‐based organoclays are synthesized by using in situ polymerization. Four kinds of MDEA‐based materials are prepared and used as organifiers of pristine montmorillonite. The clay treated with the organifiers has a d‐spacing range that is about 14–21 Å. The PCNs with these organoclays are characterized by using wide‐angle X‐ray diffraction, scanning and transmission electron microscopy, atomic force microscopy, capillary rheometry, and tensile and barrier testing. The PCNs form an intercalated and delaminated structure. The well‐stacked nanoclays are broken down into small pieces in the PET matrix and the thickness of the clay bundle decreases to 20 nm. The melt viscosity and tensile strength of these PCNs increases with only 0.5 wt % clay. In oxygen barrier testing, the PCN with 1 wt % well‐dispersed organoclay shows a twofold higher barrier property than pure PET. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 1262–1271, 2007     

原位插层聚合制备PVC/蒙脱土纳米复合材料

采用氯乙烯单体直接插层到蒙脱土中进行原位插层聚合，制备纳米复合材料，并用小角X射线衍射（XRD）、扫描电子显微镜（SEM）和电子探针技术对复合材料进行了结构表征。实验结果表明：采用原位插层聚合法制得的PVC／蒙脱土（MMT）复合材料为剥离型纳米复合材料。     

Poly(butylene terephthalate)/organoclay nanocomposites prepared by in situ interlayer polymerization and its fiber (II)

Intercalated nanocomposites with poly(butylene terephthalate) (PBT) incorporated between the montmorillonite layers were synthesized from dimethyl terephthalate and 1,4-butane diol by using an in situ interlayer polymerization. The PBT nanocomposites were melt-spun at different organoclay contents to produce monofilaments. The samples were characterized by using wide angle X-ray diffraction, electron microscopy, thermal analysis, and tensile testing. The extent of the clay layer in the PBT was confirmed by using X-ray diffraction and electron microscopy, and the clay layer was found to be highly dispersed on a nanometer scale. The addition of only a small amount of organoclay was enough to improve the thermo-mechanical properties of the PBT hybrid fibers. The hybrids were extruded with various draw ratios (DRs) to examine the tensile mechanical property of the fibers. At DR=1, the ultimate tensile strength of the hybrid fibers increased with the addition of clay up to a critical content and then decreased. However, the initial modulus monotonically increased with increasing amount of organoclay in the PBT matrix. When the DR was increased from 1 to 6, for example, the strength and the initial modulus values of the hybrids containing 3 wt% organoclay decreased linearly.     

Thermal stability of poly(vinyl chloride)/layered double hydroxide nanocomposites

Effects of nanoscale dispersed layered double hydroxides (LDHs) on thermal stability of poly(vinyl chloride) (PVC) in thermal and thermooxidative degradation processes are investigated by dynamic and isothermal thermogravimetric analysis (TGA), discoloration test, fourier transform infrared (FTIR), and ultraviolet‐visible (UV‐vis) spectroscopic techniques. During both stages of thermal degradation, the degradation temperatures, including onset degradation temperature and temperature of the maximum degradation rate, increase, and the final residue yield of the PVC/LDH nanocomposites reaches 14.7 wt %, more than double that for neat PVC. The thermooxidative degradation process is more complex. During the first two stages, the presence of nanoscale dispersed LDH particles enhances the thermal stability, whereas in the last stage accelerates the thermal degradation possibly due to the accumulation of heat released. Additionally, the studies of the isothermal thermooxidative degradation process by FTIR and UV‐vis spectra indicate that both polyene backbone formation and some carbonyl groups are simultaneously developed. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Preparation and characterization of poly(vinyl chloride)/virgin and treated sisal fiber composites

Mechanical property changes, thermal stability, and water absorption capacity of poly(vinyl chloride) (PVC)/sisal fiber composites were assessed with respect to the effect of maleic anhydride chemical treatments of the sisal fiber, for five different sisal fiber contents, varying from 0 to 30% by weight in the composite. The composites prepared with the untreated sisal exhibited higher tensile modulus and hardness than the unloaded resin, while elongation and tensile strength were reduced. The deterioration in the mechanical properties of PVC blended with sisal fiber is attributed to the presence of moisture, interfacial defects at the fiber and polymer interface, and fiber dispersion in the PVC matrix. The amount of absorbed water is a function of the amount of fiber in the composite (F0 = 0 phr, F5 = 0.77 phr, and F20 = 4.83 phr). The comparison of the results of characterization of F5, F20, and F30 formulations prepared with the untreated fibers and the treated ones showed a reduction in absorbed water after the chemical treatment of fiber with maleic anhydride (F0 = 0 phr, F5 = 0.28 phr, and F20 = 2.99 phr), thus improving the mechanical properties of composites prepared with the treated sisal. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 3630–3636, 2007     

Synthesis and characterization of poly(methyl methacrylate)/montmorillonite nanocomposites by in situ bulk polymerization

Poly(methyl methacrylate)/montmorillonite (MMT) nanocomposites were prepared by in situ bulk polymerization. The results showed that the silicone coupling agent affected the structure and properties of hybrid materials. XRD analysis showed that the dispersion of clay in nanocomposites with silicone‐modified organophilic MMT was more ordered than that in nanocomposites with unmodified organophilic MMT. The glass transition temperature (T_g) of the nanocomposites was 6–15°C higher and the thermal decomposition temperature (T_d) was 100–120°C higher than those of pure PMMA. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 2256–2260, 2003     

Synthesis and characterization of poly(propylene)/montmorillonite nanocomposites by simultaneous grafting‐intercalation

A novel process for the preparation of poly(propylene)/montmorillonite (PP/MMT) nanocomposites was developed via simultaneous solution grafting‐intercalation in the presence of a reactive ammonium cation that can be grafted onto poly(propylene). Partially introducing this reactive cation into long alkyl ammonium modified MMT interlayers can transfer a conventional microcomposite into intercalated/exfoliated nanocomposites, which was evidenced by X‐ray diffraction (XRD) and transmission electron microscopy (TEM). The PP chains were tethered onto the clay surface through the bridge of the reactive ammonium cations, which can be characterized by FTIR. The bridged chemical bonding also results in a good interface adhesion between PP and MMT, as confirmed by SEM investigation. The enhanced thermal properties of PP/MMT nanocomposites were characterized by thermogravimetric analysis. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 1018–1023, 2004     

Preparation and structural characterization of nanocrystalline poly(vinyl chloride)

This article describes the development of novel nanocrystalline poly(vinyl chloride) (PVC) for potential applications in PVC processes and reports improvements in the mechanical properties and thermal resistance. Before the preparation of nanocrystalline PVC via jet milling, PVC was spray‐treated and heat‐treated to improve its crystallinity. The pulverization and degradation, morphology, crystalline structure, and melting‐point changes of postmodified PVC during jet milling and the relationship between the distributions of the particle size and processing temperature were investigated. X‐ray analysis and density testing indicated increased density and improved crystallinity. The crystalline region of nanocrystalline PVC was less than 80 nm, with a particle size distribution of 5–20 μm and a melting point of less than 128°C. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 563–569, 2004     

Preparation and characterization of poly(hydroxybutyrate‐co‐hydroxyvalerate)–organoclay nanocomposites

This study describes the microstructure and thermal and mechanical properties of poly(hydroxybutyrate‐co‐hydroxyvalerate) (PHB/HV)–organoclay nanocomposites prepared by melt intercalation using Cloisite 30B, a monotallow bis‐hydroxyethyl ammonium‐modified montmorillonite clay. X‐ray diffractometry and transmission electron microscopy analyses clearly confirm that an intercalated microstructure is formed and finely distributed in the PHB/HV copolymer matrix because PHB/HV has a strong hydrogen bond interaction with the hydroxyl group in the organic modifier of Cloisite 30B. The nanodispersed organoclay also acts a nucleating agent, increasing the temperature and rate of crystallization of PHB/HV; therefore, the thermal stability and tensile properties of the organoclay‐based nanocomposites are enhanced. These results confirm that the organoclay nanocomposite greatly improves the material properties of PHB/HV. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 525–529, 2003     

Preparation and characterization of flame‐retardant melamine cyanurate/polyamide 6 nanocomposites by in situ polymerization

This article focuses on an improved method, i.e., improved in situ polymerization of ε‐caprolactam in the presence of melamine derivatives to prepare flame‐retardant melamine cyanurate/polyamide 6 (MCA/PA6) nanocomposites. The chemical structures of these synthetic flame retardant composites are characterized by Fourier‐transform infrared spectroscopy and X‐ray diffraction. Morphologies, mechanical properties, and thermal properties also are investigated by the use of transmission electron microscopy, mechanical testing apparatus, differential scanning calorimetry, and thermogravimetric analysis, respectively. Through transmission electron microscopy photographs, it can be found that the in situ‐formed MCA nanoparticles with diametric size of less than 50 nm are nanoscaled, highly uniformly dispersed in the PA6 matrix. These nanocomposites, which have good mechanical properties, can reach UL‐94 V‐0 rating at 1.6‐mm thickness even at a relatively low MCA loading level. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Preparation and crystallization of poly(ethylene terephthalate)/SiO2 nanocomposites by in‐situ polymerization

Poly(ethylene terephthalate) (PET)/SiO₂ nanocomposites were prepared by in situ polymerization. The dispersion and crystallization behaviors of PET/SiO₂ nanocomposites were characterized by means of transmission electron microscope (TEM), differential scanning calorimeter (DSC), and polarizing light microscope (PLM). TEM measurements show that SiO₂ nanoparticles were well dispersed in the PET matrix at a size of 10–20 nm. The results of DSC and PLM, such as melt‐crystalline temperature, half‐time of crystallization and crystallization kinetic constant, suggest that SiO₂ nanoparticles exhibited strong nucleating effects. It was found that SiO₂ nanoparticles could effectively promote the nucleation and crystallization of PET, which may be due to reducing the specific surface free energy for nuclei formation during crystallization and consequently increase the crystallization rate. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 655–662, 2006     

Synthesis and characterization of poly(ethylene tetrasulfide)/graphene oxide nanocomposites by in situ polymerization method

Poly(ethylene tetrasulfide) (PSP) is synthesized via interfacial polycondensation of 1,2 dichloroethane and sodium tetrasulfide, in the presence of graphene oxide (GO). This process resulted in homogeneously dispersed PSP/GO nanocomposites. Nanocomposites of 0.3 and 0.5?wt% of GO are synthesized and their morphology, chemical characteristics behavior are studied employing field emission scanning electron microscopy, Fourier transform infrared spectroscopy and X-ray diffraction techniques. Thermal characterization of composites is performed by differential scanning calorimetry and thermogravimetry analysis. Results indicate that the addition of only small amounts (0.5?wt%) of well-dispersed GO can increase the melting point more than 16°C resulting in better thermal properties for the composite. The solubility of nanocomposite is also studied and results show that the solubility depends on solvent concentration in addition to reinforcement (GO) deals.     

Preparation and characterization of flexible poly(vinyl chloride) foam films

In this study, the effect of activator ZnO and heating time at 190°C on foaming, gelation, and dehydrochlorination of poly(vinyl chloride) (PVC) plastisol was investigated. For this purpose, a PVC plastisol was prepared by mixing PVC, dioctyl phthalate (DOP), azodicarbonamide (ADC), ZnO, and the heat stabilizers calcium stearate (CaSt₂) and zinc stearate(ZnSt₂). PVC plastisol films were heated for 3, 6, 12, and 24 min periods at 190°C to see the effect of heating time on the gelation and foaming processes of the PVC foam. The time of 12 min was determined to be optimum for the completion of gelation and foaming processes without thermal degradation of PVC. No foaming was observed under the same conditions for the samples without ZnO. ZnO had a significant catalytic effect on ADC decomposition, accelerating the foaming of the films. Average porosity measurement showed a consistent increase in porosity with heating time up to 76% and the average density decreased from 1.17 to 0.29 g/cm³ on foaming. Tensile tests showed that the tensile strength and tensile strain both increased considerably up to 0.98 MPa and 207%, respectively, with heating time and the elastic modulus was seen to gradually decrease from 4.7 to 0.7 MPa with heating time. Films without ZnO had higher tensile strength since there were no pores. PVC thermomat tests showed that ZnO lowered the stability time of plastigel film with azodicarbonamide. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Preparation and characterization of poly(vinyl chloride)/layered double hydroxide nanocomposites with enhanced thermal stability

Poly(vinyl chloride)/layered double hydroxide (PVC/LDH) nanocomposite has been prepared via solution intercalation process using dodecyl sulfate (DS⁻) or stearate anion modified LDH. XRD and TEM results give evidence that the inorganic LDH particles were dramatically exfoliated into nanoscale and homogeneously dispersed in PVC matrix. The enhanced thermal stability was confirmed by conventional Congo Red test. The nanocomposite containing Mg₃Al-LDH-stearate had the maximum of increased dehydrochlorination time, 15 times of that of neat PVC, and more than twice of that of PVC/LDH-NO₃ composite and PVC/LDH-DS nanocomposite at 5 wt% loading. Furthermore, its thermal stability time increased with the LDH content. At 10 wt% loading of Mg₃Al-LDH-stearate, it reached 20 times of that of PVC, and obviously larger than that of the previously reported nanocomposite using alkyl phosphonate (AP) grafted LDH. The reason may lie on the absorption of the released HCl during degradation by both nanoscale dispersed LDH particles and stearate anions.     

Preparation of poly(lactic acid)/poly(ethylene glycol)/organoclay nanocomposites by melt compounding

Poly(lactic acid) (PLA)/organoclay nanocomposites were prepared by melt compounding in a co‐rotating twin screw extruder. Two types of commercialized organoclay (dimethyl benzyl stearyl ammonium ion and dimethyl distearyl ammonium ion intercalated between clay platelets named as Clay A and Clay B, respectively) and two grades of poly(ethylene glycol) (PEG) with different molecular weight (M_w = 2,000 and 300,000–500,000 named as PEG2k and PEG500k, respectively) were used in this study. The Young's modulus improved by the addition of organoclay to PLA matrix. The Young's modulus decreased with the addition of PEG to PLA/organoclay nanocomposites. The tensile strength and elongation of PLA/Clay B nanocomposites increased with the addition of PEG2k. The effect of the addition of PEG on d‐spacing of PLA/organoclay nanocomposites is dependent upon the kind of organoclay. The sizes of clay agglomerations in PLA/PEG/organoclay nanocomposites are larger than those of PLA/organoclay ones in the same organoclay. Addition of PEG to PLA/organoclay nanocomposites during melt compounding will not be useful for the preparation of PLA/organoclay having fully exfoliated clay platelets. The shear thinning properties of the nanocomposites are independent of the addition of PEG. On the whole, PEG2k is good plasticizer for PLA/organoclay nanocomposites. POLYM. COMPOS. 27:256–263, 2006. © 2006 Society of Plastics Engineers     

Preparation,characterization, and properties of poly(vinyl chloride)/organophilic‐montmorillonite nanocomposites

Poly(vinyl chloride) (PVC)/organophilic‐montmorillonite (OMMT) nanocomposites were prepared by direct melt intercalation. PVC/compatibilizer ((vinyl acetate) copolymer (VAc))/OMMT nanocomposites were also prepared by melt intercalation by a masterbatch process. The effect of OMMT content on the nanostructures and properties of nanocomposites was studied. The nanostructures were studied by wide angle X‐ray diffraction (WAXD) and transmission electron microscopy (TEM). The linear viscoelastic properties and dynamic mechanical properties of PVC/OMMT nanocomposites were also investigated by an advanced rheometric expansion system (ARES) rheometer. The results showed that partially exfoliated and partially intercalated structures coexisted in the PVC/OMMT and PVC/VAc/OMMT nanocomposites. The mechanical properties test results indicated that the notched Charpy impact strengths of nanocomposites were improved compared to that of pristine PVC and had a maximum value at 1 phr OMMT loadings. The compatibilizer could further improve the impact strengths. But the existence of OMMT decreased the thermal stability of PVC/OMMT and PVC/VAc/OMMT nanocomposites. The linear viscoelastic properties test results indicated the dependence of G′ and G″ on ω shows nonterminal behaviors, and they had better processibility compared with pristine PVC. However, the glass transition temperatures of PVC/OMMT nanocomposites almost had little change compared to that of pristine PVC. POLYM. COMPOS., 27:55–64, 2006. © 2005 Society of Plastics Engineers     

Morphology and properties of polymer/organoclay nanocomposites based on poly(ethylene terephthalate) and sulfopolyester blends

Poly(ethylene terephthalate) (PET) nanocomposite films containing two different organoclays, Cloisite 30B^® (C30B) and Nanomer I.28E^® (N28E), were prepared by melt blending. In order to increase the gallery spacing of the clay particles, a sulfopolyester (PET ionomer or PETi) was added to the nanocomposites via a master‐batch approach. The morphological, thermal and gas barrier characteristics of the nanocomposite films were studied using several characterization techniques such as scanning electron microscopy, transmission electron microscopy, X‐ray diffraction, differential scanning calorimetry, dynamic mechanical analysis, rheometry and oxygen permeability. PET and PETi were found to form immiscible polymer blends and the nanoparticles were preferentially located in the PETi dispersed phase. A better dispersion of clay was obtained for nanocomposites containing N28E with PETi. On the contrary, for nanocomposites containing C30B and PETi, the number of tactoids increased and the clay distribution and dispersion became worse than for C30B alone. Overall, the best properties were obtained for the PET/C30B nanocomposite without PETi. Higher crystallinity was found for all nanocomposite films in comparison to that of neat PET. © 2012 Society of Chemical Industry