Clay intercalation and influence on flammability and crystallization behaviors of POE‐based nanocomposites

Ethylene‐octene copolymer (POE)‐based nanocomposites were prepared from POE or maleic anhydride grafted POE with organo‐modified montmorillonite (OMT) using melt blending technique. Their morphology, flammability, and crystallization behavior were investigated by X‐ray diffraction (XRD), transmission electron microscopy (TEM), cone calorimeter, and differential scanning calorimetry (DSC). XRD and TEM studies confirmed the intercalation of clay layers within the POE matrix whereas the exfoliation throughout the maleated POE matrix. Cone calorimetry results exhibited that the reduction in heat release rate of exfoliated maleated‐POE/OMT nanocomposite was greater than that of intercalated POE/OMT nanocomposite. The DSC results suggested that the nonisothermal kinetics crystallization of the exfoliated nanocomposite corresponded to tridimensional growth with heterogeneous nucleation. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers     

New Nanocomposites Based on Syndiotactic Polystyrene and Organo-Modified ZnAl Layered Double Hydroxide

New nanocomposites were prepared by mixing syndiotactic polystyrene (sPS) with organo-modified ZnAl layered double hydroxide (O-ZnAl-LDH) in toluene solution. Both wide-angle X-ray diffraction (WXRD) and transmission electron microscopy (TEM) examinations confirmed the nanocomposite formation with exfoliated or intercalated O-ZnAl-LDH distributed in the sPS matrix. Meanwhile, the nonisothermal crystallization behavior of the resulting nanocomposites was studied using differential scanning calorimetry (DSC) technique at various cooling rates. The results indicated that the O-ZnAl-LDH particles in nanometer size might act as nucleating agents and accelerate the overall nonisothermal crystallization process.     

Characterization of latex-based isotactic polypropylene/clay nanocomposites

Polypropylene/clay nanocomposite (PCN) containing 1 wt% organo-modified clay was prepared by latex technology, previously successfully applied for preparation of carbon nanotubes (CNTs)/polymer composites. The level of dispersion of organoclay and the microstructure of the resulting PCNs were characterized by means of X-ray diffraction analysis, transmission electron microscopy (TEM), and scanning electron microscopy (SEM). The obtained results have demonstrated that the latex technique represents a promising method for preparation of PP/clay nanocomposites with good dispersion of exfoliated nanoclay particles. The influence of clay nanoparticles on nonisothermal crystallization of PCN was investigated by DSC. The crystallization onset temperature of the matrix rises for about 5 °C when crystallizing from the quiescent melt. Improved thermal stability of PP/nanoclay was observed as evaluated by TGA. The dynamic mechanical analysis reveals an increase in storage modulus of PP matrix in the nanocomposites for 30% over a temperature range, indicating an increase in the stiffness of the material with the addition of organically modified clay.     

可反应性纳米二氧化硅对聚乳酸结晶行为的影响

通过熔融共混法制备了聚乳酸（PLLA）／可反应性纳米二氧化硅（RNS）复合材料,用透射电子显微镜观察RNS在PLLA基体中的分散情况,用差示扫描量热仪（DSC）和X射线衍射仪（XRD）对复合材料的非等温结晶行为进行了研究,并利用Jeziomy法和Mo法对复合材料的非等温结晶动力学进行分析。结果表明,RNS在PLLA中分散均匀,RNS的加入虽不会改变PLLA的晶型,但RNS与PLLA之间的相互作用及其异相成核能力会对聚乳酸基体的结晶速率和结晶度产生影响,导致材料结晶过程发生变化。     

Effect of organoclay in an immiscible poly(ethylene terephtalate) waste/poly(methyl methacrylate) blend

Blends of organically modified montmorillonite (OMMT) with poly(ethylene terephtalate) (PET) waste and poly(methyl methacrylate) (PMMA) were prepared by melt mixing. The morphology of PET/PMMA nanocomposites with different OMMT contents was characterized by transmission electron microscopy (TEM) and X‐ray diffraction (XRD). The nonisothermal crystallization temperatures of nanocomposites were also examined by DSC. TEM observations and XRD patterns revealed that silicate layers were intercalated and well dispersed in the blend. Nanocomposites displayed better mechanical properties when compared with the unfilled blend. DMA analyses also showed efficient mixing of the two immiscible polymers and changes in glass transition temperature with the presence of OMMT. DSC analysis showed an enhancement in crystallization rate of nanocomposites and a decrease in cristallinity. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Structure and properties of polypropylene/clay nanocomposites compatibilized by solid‐phase grafted polypropylene

Polypropylene/organic‐montmorillonite (PP/OMMT) nanocomposites were prepared via a solid‐phase PP graft (TMPP) with a higher grafting level as the compatibilizer. The effects of the compatibilizer on the structure and properties of PP/OMMT nanocomposites were investigated. The structure of the nanocomposites were characterized by X‐ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The results showed that when the weight ratio of TMPP and OMMT is greater than 1:1, the OMMT can be dispersed in PP matrix uniformly at the nanoscale. The mechanical properties of the nanocomposites reached a maximum when the weight ratio of TMPP and OMMT is 1:1, although more uniform dispersion was achieved at a higher content of TMPP. The mechanical properties of the nanocomposites decrease with the content of TMPP. The crystallization behavior, dynamic rheological property, and thermal stability of the nanocomposites were investigated by differential scanning calorimetry (DSC), dynamic rheological analysis, and thermal gravimetric analysis (TGA), respectively. Due to the synergistic effects of TMPP and OMMT on the crystallization of PP, the crystallization peak temperature of the nanocomposites increased remarkably compared with that of the neat PP. TMPP shows β‐phase nucleating ability and OMMT promotes the development of β‐phase crystallite. The nanocomposites show restricted melt flow and enhanced temperature sensitivity compared with the neat PP. The thermal stability of the nanocomposites is obviously improved compared with that of the neat PP. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers.     

Effect of the graphite nanoplatelet size on the mechanical,thermal, and electrical properties of polypropylene/exfoliated graphite nanocomposites

Polypropylene (PP)/exfoliated graphite nanoplatelet (xGnP) nanocomposites with various intrinsic aspect ratios of graphite nanoplatelets (GnPs; large and small in diameter) were prepared by a melt‐mixing procedure. Transmission electron microscopy showed that all types of xGnP were well‐dispersed in the polymer matrix. The effects of the dimensions and loading of the xGnPs on the morphology, mechanical reinforcement, and electrical properties of PP/xGnP were studied. A differential scanning calorimetry study of the PP/xGnP morphology indicated that all types of xGnP additives were heterogeneous nucleation sites for PP crystallization. Tensile testing, DMA, and thermogravimetric analysis of PP/xGnPs with different types of GnP additives showed enhancements in their mechanical properties, heat resistance, and thermal stability compared to plain PP. We also found a significant increase in the conductivity of PP/xGnP. The PP/xGnP with a large diameter of GnPs demonstrated the lowest percolation threshold, equal to 4 vol % of the xGnP loading. The mechanical properties were estimated by means of micromechanical modeling. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Polypropylene/montmorillonite composites and their application in hybrid fiber preparation by melt‐spinning

Polypropylene (PP)/organomontmorillonite (OMMT) nanocomposites have been successfully prepared by melt intercalation by using the conventional method of twin‐screw extrusion and subsequently submitted for melt‐spinning. The structure and properties of the PP/clay nanocomposites and hybrid fibers were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X‐ray diffraction (XRD), differential scanning calorimetry (DSC), and crystallization dynamics, etc. The organoclay layers were found to disperse in the PP resin at the nanometer level. The nanoscaled OMMT layers, dispersed in the PP matrix, actually played the role of heterogeneous nuclei species in the process of PP crystallization and increased the nucleation speed of the composites, hereby leading to the increase of crystallization rate of the as‐spun fiber. Meanwhile, it was found that the crystallinity of PP/OMMT hybrid fibers is much higher than that of pure PP fiber at the same draw ratios, whereas the orientation of PP/OMMT hybrid fibers is much lower than that of pure PP fiber at the same draw ratios. Because of the effective intercalation of OMMT into PP matrix, the nanocomposites have good spinnability, and the moisture absorption of the final PP fiber is improved. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 552–558, 2004     

Effects of nanoparticle treatment on the crystallization behavior and mechanical properties of polypropylene/calcium carbonate nanocomposites

Effects of nanoparticle surface treatment on the crystallization behavior and mechanical properties of polypropylene (PP)/CaCO₃ nanocomposites were investigated by using differential scanning calorimetry (DSC), polarized optical microscope (POM), X‐ray diffraction (XRD), transmission electron microscopy (TEM), and scanning electron microscopy (SEM). The results demonstrated that the interfacial interaction formed between PP and nanoparticles significantly influenced the thermal and mechanical properties of nanocomposites. It was found that CaCO₃ nanoparticles modified by a single aluminate coupling agent (CA‐1) could improve the onset crystallization temperature more effectively than that modified by a compound surface‐treating agent (CA‐2) could. However, there is no significant difference in total rate of crystallization for the two PP/CaCO₃ nanocomposites (PPC‐1 and PPC‐2), which contained CA‐1 and CA‐2, respectively. In contrast, CA‐2 modified nanoparticles could cause smaller spherulites and induce much more β‐phase crystal in nanocomposites than that of CA‐1 modified nanoparticles. This may be explained by a synergistic effect of aluminate coupling agent and stearic acid in CA‐2, which also resulted in an improved toughness for PPC‐2. © 2006 Wiley Periodicals, Inc. J Appl PolymSci 102: 3480–3488, 2006     

Polyoxymethylene/polyurethane/alumina ternary composites: Structure,mechanical, thermal and dielectric properties

Ternary composites composed of polyoxymethylene (POM), polyurethane (PU), and boehmite alumina were produced by melt blending with and without latex precompounding. Latex precompounding served for the predispersion of the alumina particles. The related masterbatch (MB) was produced by mixing the PU latex with water‐dispersible boehmite alumina. The dispersion of the alumina was studied by transmission and scanning electron microscopy techniques (TEM and SEM, respectively) and discussed. The crystallization of POM was inspected by means of differential scanning calorimetry (DSC) and polarized optical microscopy (DSC and polarized light microscopy, respectively). The mechanical and thermomechanical properties of the composites were determined in uniaxial tensile, dynamic‐mechanical thermal analysis (DMTA), short‐time creep tests (performed at various temperatures), and thermogravimetric analysis (TGA). The melt flow of the composites was characterized in a plate/plate rheometer. In addition, the dielectric response of the nanocomposites was investigated by means of broadband dielectric spectroscopy at an ambient temperature. The composites produced by the MB technique outperformed the direct melt (DM) compounded composites in respect to the thermal and mechanical characteristics. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Polymer nanocomposites based on needle‐like sepiolite clays: Effect of functionalized polymers on the dispersion of nanofiller,crystallinity, and mechanical properties

Polypropylene (PP)/sepiolite (Sep) nanocomposites are prepared by melt compounding in a mini‐extruder apparatus. The often used maleic anhydride‐modified polypropylene (PP‐g‐MA) is compared with two custom‐made functionalized polymers, PP‐acid and the di‐block copolymer PP‐PEO, with respect to the filler dispersion and filler reinforcement efficiency. For that purpose, morphological and mechanical studies are carried out by means of scanning electron microscopy (SEM), transmission electron microscopy (TEM), and mechanical tensile tests. In addition, the nanocomposites are characterized by wide‐angle X‐ray scattering (WAXS) and differential scanning calorimetric (DSC) techniques, to assess the effect of the nanofiller on the crystalline structure of the PP matrix nano‐filler. The use of PP‐PEO and PP‐acid resulted in a better nanofiller dispersion compared with traditional PP‐g‐MA‐modified systems. Sepiolite acts as nucleating agent for the crystallization of PP and seems to lead to an orientation of the α‐phase crystals. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2008     

Crystallization behavior,morphology, and mechanical properties of poly(lactic acid)/tributyl citrate/treated calcium carbonate composites

In this article, poly(lactic acid) (PLA) composites containing titanate coupling agent treated calcium carbonate (T‐CaCO₃) and tributyl citrate (TBC) were prepared via melt blending. The crystallization, morphology, mechanical properties, and nonisothermal cold crystallization kinetics of PLA composites were studied by means of differential scanning calorimetry (DSC), wide angle X‐ray diffraction (WAXD), polarized light microscopy (PLM), scanning electron microscopy (SEM), and mechanical tests, respectively. The results show that TBC promotes crystallization of PLA. Both T‐CaCO₃ and TBC significantly decrease the spherulitic size, but the crystal structure of PLA is not changed. A synergistic toughening effect is obtained by the combination of T‐CaCO₃ and TBC. The nonisothermal cold crystallization kinetics of PLA composites is well described by Mo's method. The activation energies (ΔE) of nonisothermal cold crystallization were calculated by Kissinger and Takhor methods, respectively. It is found that the addition of T‐CaCO₃ and TBC increases ΔE, but it also increases the cold crystallization rate. POLYM. COMPOS., 35:1570–1582, 2014. © 2013 Society of Plastics Engineers     

Crystallization,properties, and crystal and nanoscale morphology of PET–clay nanocomposites

The crystallization process and crystal morphology of poly(ethylene terephathalate) (PET)–clay nanoscale composites prepared by intercalation, followed by in‐situ polymerization, have been investigated by scanning electronic microscopy (SEM), transmission electronic microscopy (TEM), dynamic scanning calorimetry (DSC), and X‐ray techniques, together with mechanical methods. Results of the nonisothermal crystallization dynamics show that the nanocomposites of PET (Nano‐PET) have 3 times greater crystallization rate than that of pure PET. The thermal properties of Nano‐PET showed heat distortion temperature (HDT) 20–50°C higher than the pure PET, while with a clay content of 5%, the modulus of Nano‐PET is as much as 3 times that of pure PET. Statistical results of particle distribution show that the average nanoscale size ranges from 10 to 100 nm. The particles are homogenously distributed with their size percentages in normal distribution. The agglomerated particles are 4% or so with some particles size in the micrometer scale. The morphology of exfoliated clay particles are in a diordered state, in which the morphology of the PET spherulitics are not easy to detect in most of microdomains compared with the pure PET. The molecular chains intercalated in the interlamellae of clay are confined to some extent, which will explain the narrow distribution of the Nano‐PET molecular weight. The stripe‐belt morphology of the intercalated clay show that polymer PET molecular chains are intercalated into the enlarged interlamellar space. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 1139–1146, 1999     

Effect of Nanoparticle Surface Treatment on Nonisothermal Crystallization Behavior of Polypropylene/Calcium Carbonate Nanocomposites

Polypropylene (PP)/CaCO₃ nanocomposites were prepared by melt-blending method using a Haake-90 mixer. The CaCO₃ nanoparticles were surface modified with a coupling agent before compounding. A fine dispersion of the modified nanoparticles in the nanocomposites was observed by transmission electron microscopy (TEM). Effects of surface treatment of CaCO₃ nanoparticles on the nonisothermal crystallization behavior and kinetics of PP/CaCO₃ nanocomposites were investigated by differential scanning calorimetry (DSC). Jeziorny and Mo methods were used to describe the nonisothermal crystallization process. It was shown that the crystallization temperature of the nanocomposites increased due to the heterogeneous nucleation of the surface-treated nanoparticles. It was found that the nanoparticles modified with a proper content range of coupling agent could facilitate the nonisothermal crystallization of the nanocomposites under certain conditions (the cooling rate and the relative degree of crystallinity). This may be a potential application for the crystallization controlling of composites in manufacturing. In addition, the activation energy of crystallization for the nanocomposites and the nucleation activity of the nanoparticle were estimated by using Kissinger and Dobreva's methods, respectively. It could be concluded that the surface-treated nanoparticles had a strong nucleating activity, which caused the decrease of the activation energy of the nanocomposites.     

Formation of an interconnected lamellar structure in PVDF membranes with nanoparticles addition via solid‐liquid thermally induced phase separation

Novel microporous membranes were prepared via thermally induced solid‐liquid (S‐L) phase separation of mixtures containing poly(vinylidene fluoride) (PVDF)/diphenyl ketone (DPK)/nanoparticles [such as montmorillonite (MMT) and polytetrafluoroethylene (PTFE)] in diluted systems with a mass ratio of 29.7/70/0.3 wt %. The crystallization and melting characteristics of these diluted systems were investigated by polarizing optical microscopy (POM), scanning electron microscopy (SEM), differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR), and wide angle X‐ray diffraction (WAXD). The nanoparticle structure and the interaction between PVDF chains and nanoparticle surfaces determined the crystallization behavior and morphology of the PVDF membrane. The addition of MMT and PTFE had a significant nucleation enhancement on the crystallization of PVDF accompanied by S‐L phase separation during the thermally induced phase separation (TIPS) process. It was observed that an interconnected lamellar structure was formed in these two membranes, leading to a higher tensile strength compared with that of the reference membrane without nanoparticles addition. Additionally, addition of MMT facilitates the fiber‐like β phase crystal formation, resulting in the highest elongation at break. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Studies on synergistic effect of CNT and CB nanoparticles on PVDF

Poly(vinylidene fluoride) (PVDF) nanocomposites with different loading of carbon nanotubes (CNT) and carbon black (CB) were prepared by melt blending method. The conductivity and mechanical properties of the nanocomposites were investigated. The results showed that percolation threshold of CNT/CB/PVDF nanocomposites appeared at a lower concentration (1.25 vol% CNT) than that of CNT/PVDF (>2.08 vol% CNT). The tensile strength of CNT/CB/PVDF nanocomposites was also improved, with 32.1% increase compared to PVDF and 18.0% increase compared to CNT/PVDF at loading of 1.25 vol% CNT/0.96 vol% CB. To explore the synergistic effect of CNT and CB, nonisothermal crystallization and isothermal crystallization behaviors of PVDF and its nanocomposites were studied by differential scanning calorimetry, and the crystallization morphology of them was observed under the three dimensional digital microscope with the polarized model. The crystallization rate of PVDF was speeded up markedly because of heterogeneous nucleation effect of nanoparticles, and CNT and CB nanoparticles had a synergistic effect on nucleation. Polarized microscope observation confirmed that spherulite size of PVDF became smaller owing to the accelerating of crystallization, which influenced the distribution of nanoparticles. The dispersion of nanofillers in matrix was observed by scanning electron microscope. It was revealed that CB could make CNT disperse more evenly in the PVDF matrix. The synergies network of CNT and CB is suggested to build in matrix, which improved conductivity and mechanical properties of PVDF nanocomposites. POLYM. COMPOS., 36:2248–2254, 2015. © 2014 Society of Plastics Engineers     

PVDF/PMMA/Basalt fiber composites: Morphology,melting and crystallization,structure, mechanical properties,and heat resistance

This paper is to study the effect of basalt fiber on morphology, melting and crystallization, structure, mechanical properties, melting and crystallization of PVDF/PMMA composites using scanning electron microscopy (SEM), X‐ray, differential scanning calorimeter (DSC), dynamical mechanical analysis (DMA), etc. Basalt fiber may disperse well in PVDF/PMMA matrix and form compact fiber network, and this makes tensile and flexural strength of fiber reinforced PVDF/PMMA composites get to the maximum value of 62 and 102 MPa, respectively. However, the mechanical properties begin to decrease when basalt fiber content exceeds 20 wt %. The α and β phase of PVDF can coexist in composites, and basalt fiber and PMMA can induce β phase of PVDF. The melting temperature of PVDF in composites is kept unchanged, but the degree of crystallinity of composites increases as basalt fiber content increase, and then declines when fiber content exceeds 20%. The DSC results confirm that the nucleation ability of PVDF is enhanced by basalt fiber. Also, the heat resistance of PVDF/PMMA composite is improved from 133 to 146.1°C due to basalt fiber. The DMA shows that basalt fiber increases the storage modulus of PVDF/PMMA composite, and the loss peak of PMMA increases from 116.1 to 130°C. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40494.     

Biodegradable and biocompatible nanocomposites of poly(ϵ‐caprolactone) with hydroxyapatite nanocrystals: Thermal and mechanical properties

Nanocomposites of poly(?‐caprolactone) (PCL) with hydroxyapatite nanocrystals (HAP) prepared through the solvent‐cast technique were characterized by means of transmission electron microscopy (TEM), differential scanning calorimetry (DSC), scanning electron microscopy (SEM), and tensile tests. Such composites are of great importance to make bone‐like substitutes as HAP nanocrystals have similar composition, morphology, and crystal structure as natural apatite crystals. The TEM micrograph reveals the nanocrystals dispersed homogeneously in the matrix at a microscale level. The solvent‐cast samples commonly show much higher melting points and crystallinity than the melt‐quenched samples, due to a lower undercooling as well as more sufficient time to crystallize. For both cases of samples, the melting point decreases slightly with HAP content while the level of crystallinity attained by the PCL component is not hindered by the nanocrystals. Both the glass transition temperatures and the nonisothermal crystallization temperatures are composition dependent. The tensile modulus increases with increasing HAP content while the yield stress is almost invariant with composition. Theoretical prediction of the modulus based on Halpin–Tsai equations shows excellent agreement with the experimental result. By analysis of the variation in fracture stress and strain with composition, a ductile‐to‐quasi‐brittle transition is revealed to be operative for the nanocomposites, as also can be seen by SEM. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 676–683, 2002     

Nonisothermal crystallization kinetics of poly(butylene terephthalate)/montmorillonite nanocomposites

The melt intercalation method was employed to prepare poly(butylene terephthalate) (PBT)/montmorillonite (MMT) nanocomposites, and the microstructures were characterized with X‐ray diffraction and transmission electron microscopy. Then, the nonisothermal crystallization behavior of the nanocomposites was studied with differential scanning calorimetry (DSC). The DSC results showed that the exothermic peaks for the nanocomposites distinctly shifted to lower temperatures at various cooling rates in comparison with that for pure PBT, and with increasing MMT content, the peak crystallization temperature of the PBT/MMT hybrids declined gradually. The nonisothermal crystallization kinetics were analyzed by the Avrami, Jeziorny, Ozawa, and Mo methods on the basis of the DSC data. The results revealed that very small amounts of clay (1 wt %) could accelerate the crystallization process, whereas higher clay loadings reduced the rate of crystallization. In addition, the activation energy for the transport of the macromolecular segments to the growing surface was determined by the Kissinger method. The results clearly indicated that the hybrids with small amounts of clay presented lower activation energy than PBT, whereas those with higher clay loadings showed higher activation energy. The MMT content and the crystallization conditions as well as the nature of the matrix itself affected the crystallization behavior of the hybrids. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 99: 3257–3265, 2006     

Nucleation effect of polyamide on polyoxymethylene

The crystallization behavior and morphology of polyoxymethylene (POM) and POM with polyamide (PA) were studied by polarized light microscopy (PLM), isothermal and nonisothermal differential scanning calorimetry (DSC), and scanning electron microscopy (SEM). The isothermal crystallization kinetics were analyzed with the Avrami equation. Compared with the virgin POM, the addition of PA can reduce the spherulites size and improve the crystallization growth rate and crystallinity (X_c) of POM, which demonstrates that the nucleation effect of PA as the high‐molecular nucleus is favorable to the mechanical properties and dimension stability of POLYM. ENG. SCI., 45:1174–1179, 2005. © 2005 Society of Plastics Engineers