PET/SiO2 nanocomposites prepared by cryomilling

The mixed powders of poly(ethylene terephthalate) (PET) and SiO₂ has been subjected to cryomilling. The evolution of microstructure with time was characterized using scanning electron microscope, transmission electron microscope, field emission scanning electron microscope, and laser diffraction particle size analyzer. It was shown that, upon cryomilling for 10 h, SiO₂ nano particles were well deconglomerated into single particles (～30 nm) that get homogeneously dispersed in PET matrix. The resulted PET/SiO₂ primary particles were flake‐shaped with a size of 400 nm. These primary composite particles agglomerated to form secondary composite particles with an average size about 7.6 μm. A three‐stage model was purposed for the formation mechanism of the nanocomposite structures induced by cryomilling. Our evidences suggest that cryomilling is a capable and promising technique for the production of polymer/inorganic nanocomposites. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 1161–1167, 2006     

Structural changes in poly(ethylene terephthalate) induced by cryomilling and ambimilling

Poly(ethylene terephthalate) (PET) has been subjected to high energy ball milling at two different temperatures (cryogenic temperature and ambient temperature). The morphological and crystal structural evolutions of milled powders are characterized by means of scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X‐ray diffraction measurement. The particle size and distribution of milled powders are measured by laser diffraction particle size analyzer (LDPSA). The results indicate that the mechanisms of refining and amorphization are remarkably different between cryomilling (mechanical milling under cryogenic temperature) and ambimilling (mechanical milling under ambient temperature). The cryomilled particles are agglomerated morphology, while the ambimilled particles are cold‐welded morphology. Cryomilling induced crystalline PET translates to general amorphous, however, ambimilling induced crystalline PET transforms to oriented amorphous. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 986–993, 2006     

Polyaniline/iron nanocomposites prepared by cryomilling

The polyaniline/iron nanocomposites with both conducting and magnetic properties have been prepared by cryomilling (high‐energy ball milling under cryogenic temperature), in which the average size of iron grains attains 20 nm. Enhanced coercivity of 206 Oe and decreased conductivity of 0.1 S cm^?1 at room temperature have been obtained for the nanocomposites containing 10% volume fraction of iron in polyaniline after cryomilling for 20 h. The high value of the coercivity could be considered due to the presence of a fraction of single‐domain particles in the nanocomposites. The low value of the conductivity could be considered due to the dedoping of conducting polyaniline with the cryomilling time. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 3157–3164, 2006     

Study on the nonisothermal crystallization behavior of poly(vinyl alcohol)/attapulgite nanocomposites by DSC analysis

Attapulgite (AT)‐reinforced poly(vinyl alcohol) (PVA) nanocomposite films were prepared by solution‐casting technique. The nonisothermal crystallization behaviors of PVA bulk and PVA/AT nanocomposites have been investigated by differential scanning calorimetry (DSC). It has been found that the uniformly dispersed AT nanorods in the matrix have great influence on the glass transition temperature and crystallization behavior of PVA matrix. The Jeziorny method has been employed to analyze the DSC data. The results show that Jeziorny method could describe this system very well. Comparing with the PVA bulk, PVA/AT nanocomposites have higher crystallinity X_t, shorter semicrystallization time t_1/2, and higher crystallization rate constant Z_c. It can be concluded that AT can be used as an effective nucleating agent and has effects on the growth of crystallites in the crystallization process of PVA matrix. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 534–540, 2006     

Confined crystallization behaviors in polyethylene/silica nanocomposites: Synergetic effects of interfacial interactions and filler network

The confinement effects introduced by nanoparticles have been reported to influence the phase behaviors thus the properties of polymer nanocomposites. In this study, molecular dynamics and crystallization behaviors of polyethylene (PE) composited with three types of silica (SiO₂) nanoparticles, namely unmodified SiO₂, hydrophobically modified SiO₂, SiO₂‐APTES (3‐aminopropyltriethoxysilane) and SiO₂‐PTES (n‐propyltriethoxysilane), were systematically investigated via a combination of DSC, XRD and ¹H solid‐state NMR measurements. The suppressions in crystallization and chain mobilities of PE rank in the order of unmodified SiO₂ < SiO₂‐APTES < SiO₂‐PTES due to the increasing interfacial interactions between PE and SiO₂ nanoparticles. Additionally, independent of polymer–nanoparticle interactions, a silica network forms for all three kinds of nanocomposites when SiO₂ content reaches 83 wt %. The mobilities of polymer chains are severely restricted by such a percolated network structure, leading to a turning point in the crystallization ability of nanocomposites and a new crystallization peak at 45 °C lower than that of pure PE. The synergetic effects of interfacial interactions and filler network on polymer crystallization have been thoroughly studied in this work, which will provide guidance on modifying and designing nanocomposites with controlled properties. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017 , 55, 498–505     

Electromagnetic nanocomposites prepared by cryomilling of polyaniline and Fe nanoparticles

The polyaniline (PANI)/iron nanocomposites have been prepared by high‐energy ball milling under cryogenic temperatures, namely cryomilling, of PANI with Fe nanoparticles. It takes 5 h to refine the Fe into an average grain size of 20 nm and to get homogeneously dispersed in PANI matrix. The obtained PANI/Fe nanocomposites have a maximum conductivity of 0.78 S cm^?1 after 2‐h cryomilling, whereas its coercivity increases monotonously with time in the range of experiment up to 10 h. It is found that the sizes of Fe particles have obvious effects on both electrical and magnetic properties. When compared with micrometer Fe particles as raw materials, Fe nanoparticles result in somewhat lower conductivity but a much higher coercivity exceeding 400 Oe. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 1571–1576, 2008     

Morphology and physical properties of polyethylene/silicate nanocomposite prepared by melt intercalation

Maleated polyethylene (PEMA)/silicate nanocomposites with a different aspect ratio of silicate and maleated PEMA/SiO₂ composite were prepared by melt intercalation. The nanocomposites with a high aspect ratio silicate (montmorillonite) showed a faster decrease in the terminal slope of the storage modulus and a steeper increase in complex viscosity than those with a low aspect ratio silicate (laponite) and SiO₂. The addition of montmorillonite increases the crystallization and the melting temperature of PEMA but decreases above 3 vol % of the silicate content because of the increased viscosity. The nanocomposite with montmorillonite showed the highest yield strength and secant modulus among the composites because of the highest aspect ratio of the filler. It also revealed strong interfacial adhesion with the matrix and orientation during tensile deformation. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 1454–1463, 2002     

Compatibilization effect of TiO2 nanoparticles on the phase structure of PET/PP/TiO2 nanocomposites

Polyethylene terephthalate (PET)/Polypropylene (PP)/TiO₂ nanocomposites were prepared by compounding a PP/TiO₂ nanocomposite premix with PET in absence and presence (up to 6 vol %) of maleic anhydride grafted polypropylene (PP‐g‐MA). In absence of PP‐g‐MA, the TiO₂ nanoparticles were mainly located at the PET/PP interface and to a lesser extent in the dispersed PET droplets. As the TiO₂ nanoparticles were coated by polyalcohol their surface could react with PP‐g‐MA and thus improving the compatibilization with PP. Therefore in presence of PP‐g‐MA the TiO₂ nanoparticles were preferentially located in the PP. The incorporated TiO₂ nanoparticles exerted a compatibilization effect on the PET/PP blend. Depending on the location of TiO₂ three different compatibilization mechanisms were proposed to be at work: (1) Locating at the interface, the TiO₂ nanoparticles decrease the free energy of mixing, and thus increase the thermodynamic stability of the nanocomposites; (2) The TiO₂ nanoparticles at the interface also prevent the coalescence of PET droplets; (3) Preferentially located in the PP matrix, the TiO₂ nanoparticles decreased the viscosity ratio which facilitated the droplet breakup of PET. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 1616–1624, 2009     

Thermomechanical properties and crystallization behavior of layered double hydroxide/poly(ethylene terephthalate) nanocomposites prepared by in‐situ polymerization

Thermomechanical properties and crystallization behavior of poly(ethylene terephthalate) (PET) nanocomposites containing layered double hydroxide (LDH) were investigated. To enhance the compatibility between PET matrix and LDH, dimethyl 5‐sulfoisophthalate (DMSI) anion intercalated LDH (LDH‐DMSI) was synthesized by coprecipitation method, and its structure was confirmed by Fourier transform infrared (FTIR) spectrometer and X‐ray diffraction (XRD) measurements. Then, PET nanocomposites with LDH‐DMSI content of 0, 0.5, 1.0, and 2.0 wt% were prepared by in‐situ polymerization. The dispersion morphologies were observed by transmission electron microscopy (TEM) and XRD, showing that LDH‐DMSI was exfoliated in PET matrix. Thermal and mechanical properties, such as thermal stability, tensile modulus, and tensile yield strength of nanocomposites, were enhanced by exfoliated LDH‐DMSI nanolayers. However, elongation at break was drastically decreased with LDH loading owing to the increased stiffness and microvoids. The effect of exfoliated nanolayers, which acted as a nucleating agent confirmed by differential scanning calorimeter (DSC), on the microstructural parameters during isothermal crystallization, was analyzed by synchrotron small‐angle X‐ray scattering (SAXS). It is believed that nanocomposites could be crystallized more easily owing to the increased nucleation sites, which lead to the decrease of average amorphous region size and the long period with the increase of LDH‐DMSI content. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 28–40, 2007     

Properties of biodegradable poly(butylene carbonate) (PBC) composites with fumed silica nanoparticles

Biodegradable poly(butylene carbonate)/fumed silica (PBC/SiO₂) nanocomposites were prepared by melt compounding. The PBC/SiO₂ nanocomposites exhibited a good dispersion of aggregates of SiO₂ in the PBC matrix, and an improvement in mechanical properties. Nanoparticles affect, also, the thermal properties of PBC and especially the crystallization rate, which in all nanocomposites is faster than that of pure PBC. Due to ongoing crystallization and the crystal perfection during heating process, the melting peak of PBC shifted to higher temperature when heating from amorphous state with decreasing heating rate. With increasing cooling rate, the non-isothermal crystallization exotherms became wider and shifted to lower temperature. At a given cooling rate, the crystallization peak temperature of neat PBC was lower than that of its nanocomposite. Non-isothermal crystallization kinetic procedure, the method of Ozawa, was applied to the first deconvoluted DSC peak only by processing the data related to DSC peak. The average value of Ozawa exponent m of pure PBC is 3.04, while the one of its nanocomposite is about 2.98. Moreover, the thermal stability of the nanocomposites was increased. The T _d enhancement of the nanocomposite was remarkable.     

Investigation of thermally stimulated charge relaxation mechanism in SiO<Subscript>2</Subscript> filled polycarbonate nanocomposites

The thermally stimulated charge relaxation properties of polycarbonate (PC) filled with SiO₂ nanofiller were studied by means of thermally stimulated discharge current (TSDC). The nanocomposite samples were further characterized by UV–vis spectroscopy, scanning electron microscopy, energy dispersive X-ray spectra, and differential scanning calorimetry (DSC) techniques to investigate the dispersion of nanofillers in polymer matrix and glass transition temperature. All pristine and nanocomposites samples of thickness about 25 μm were prepared using solution mixing method. The suitable weight percentage of SiO₂ nanofillers has been chosen to prevent the nonuniform dispersion. TSDC measurement of PC (Pristine) and PC+ (7% SiO₂) shows the single peak, while TSDC characteristic of other nanocomposites are showing two peaks. The higher temperature TSDC peak of pristine and nanocomposites samples is originated due to the charge relaxation from shallower and deeper trapping sites, however, low temperature peak is caused by dipolar relaxation of charge carriers. Since the position of higher temperature TSDC peak is generally an analysis of glass transition temperature of polymer/polymer nanocomposites. The authors have observed that the temperature of this peak is almost same as the T _g measured by DSC with 0 to ±5% variation. This article presents the deeper understanding of charge relaxation mechanism caused by SiO₂ nanofillers in polycarbonate.     

Synthesis and properties of bismaleimide‐modified novolak resin/silsesquioxane nanocomposites

Bismaleimide‐modified novolak resin/silsesquioxane (BMI‐PN/SiO_3/2) nanocomposites were prepared by the sol–gel process. The reactions in the sol–gel synthesis were characterized by Fourier transform infrared spectroscopy. It was found by field emission scanning electron microscopy and atomic force microscopy studies that the particle size of the dispersed phase was about 100 nm, and there existed particle aggregates. The proportion of bismaleimide in the BMI‐PN/SiO_3/2 nanocomposites showed an important effect on the thermal properties of the composites, as demonstrated by thermogravimetric analysis and dynamical mechanical analysis. Major improvements in the glass‐transition temperature and the heat resistance of the material were achieved by the introduction of the nanosized SiO_3/2 inorganic phase, and the modulus at high temperatures was improved too. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 2599–2606, 2003     

Isothermal crystallization kinetics and melting behavior of poly(ethylene terephthalate)/barite nanocomposites

Poly(ethylene terephthalate) (PET)/Barite nanocomposites were prepared by direct melt compounding. The effects of PET‐Barite interfacial interaction on the dynamic mechanical properties and crystallization were investigated by DMA and DSC. The results showed that Barite can act as a nucleating agent and the nucleation activity can be increased when the Barite was surface‐modified (SABarite). SABarite nanoparticles induced preferential lamellae orientation because of the strong interfacial interaction between PET chains and SABarite nanoparticles, which was not the case in Barite filled PET as determined by WAXD. For PET/Barite nanocomposites, the Avrami exponent n increased with increasing crystallization temperature. Although at the same crystallization temperature, the n value will decrease with increasing SABarite content, indicating of the enhancement of the nucleation activity. Avrami analyses suggest that the nucleation mechanism is different. The activation energy determined from Arrhenius equation reduced dramatically for PET/SABarite nanocomposite, confirming the strong interfacial interaction between PET chains and SABarite nanoparticles can reduce the crystallization free energy barrier for nucleus formation. In the DSC scan after isothermal crystallization process, double melting behavior was found. And the double endotherms could be attributed to the melting of recrystallized less perfect crystallites or the secondary lamellae produced during different crystallization processes. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 655–668, 2009     

Structure and properties of poly(ethylene terephthalate)/Na+‐montmorillonite nanocomposites prepared by solid state shear milling (S3M) method

This article reported a novel technology, solid state shear milling (S³M), to prepare poly(ethylene terephthalate)/Na⁺‐montmorillonite nanocomposites using the pristine Na⁺‐MMT without organic modification so as to avoid the problem that the organic modifiers, used for MMT treatment will decompose at high processing temperature of PET, and the structure and properties of the obtained samples were investigated. XRD and TEM analyses showed that Na⁺‐MMT layers were partially delaminated and intercalated, and uniformly dispersed in the PET matrix when suffering from the strong three dimensional shearing forces of pan‐milling. DSC analysis showed that Na⁺‐MMT serves as a nucleating agent, increasing the crystallization rate as well as the crystallization temperature of PET. The properties such as thermal stability and tensile strength of the PET/Na⁺‐MMT nanocomposites prepared by S³M got remarkably improved. Solid state shear milling (S³M) method was a simple and efficient method to get polymer/Na⁺‐MMT nanocomposites with pretty good performances without organic modification of pristine Na⁺‐MMT. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 807–817, 2008     

A novel method for preparing poly(ethylene terephthalate)/BaSO4 nanocomposites

We developed a novel method for preparing poly(ethylene terephthalate)/BaSO₄ nanocomposites, which were synthesized by in situ polymerization of terephthalic acid (TPA), ethylene glycol (EG) and BaSO₄ nanoparticles prepared by reacting H₂SO₄ with Ba(OH)₂ in ethylene glycol (EG). It was shown that the addition of BaSO₄ would not influence the synthesis of PET. The structure of the nanocomposites was characterized by transmission electron microscopy (TEM), and the nanoscale dispersion of BaSO₄ particles in the PET matrix was observed when the BaSO₄ content is below 4 wt%. Moreover, the thermal properties of the nanocomposites were investigated by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The results suggest that the degree of dispersion of BaSO₄ particles in the PET matrix has important effect on the thermal properties of the nanocomposites. The existence of BaSO₄ nanoparticles enhances the crystallization rate of PET. Besides, it was found that the thermal stability of PET was improved by the addition of the BaSO₄ nanoparticles.     

Hydrolytic degradation behavior of poly(l-lactide)/SiO2 composites

In this work, different contents of nano-silica (SiO₂) particles were introduced into poly(l-lactide) (PLLA) to prepare PLLA/SiO₂ composites though a two-step compounding method, i.e. solution compounding (preparing master batch) and subsequent melt compounding (master batch dilution). The dispersion of SiO₂ was characterized using scanning electron microscope (SEM). The hydrophilicity of the material was evaluated by measuring the contact angle of water on the sample surface. The hydrolytic degradation measurements of the nanocomposites were carried out in alkaline solution at two different temperatures, i.e. 37 and 55 °C. Subsequently, microstructure evolution of PLLA matrix during the hydrolytic degradation process was systematically investigated using wide angle X-ray diffraction (WAXD), differential scanning calorimetry (DSC), and Fourier transform infrared spectroscopy (FTIR). The results showed that SiO₂ had good dispersion in the PLLA matrix. Largely enhanced hydrolytic degradation ability was achieved for PLLA/SiO₂ composites. Increasing the content of SiO₂ or enhancing the hydrolytic degradation temperature accelerated the hydrolytic degradation of PLLA matrix. Further results showed that SiO₂ promoted the reorganization of microstructure of PLLLA matrix during the hydrolytic degradation process.     

The mechanical properties and tribological behavior of epoxy resin composites modified by different shape nanofillers

Mechanical properties and tribological behavior of epoxy resin (EP) and EP nanocomposites containing different shape nanofillers, such as spherical silica (SiO₂), layered organo‐modified montmorillonite (oMMT) and oMMT‐SiO₂ composites, were investigated. The SiO₂‐oMMT composites were prepared by in situ deposition method and coupling agent modification, and transmission electron microscopy (TEM) analysis shows that spherical SiO₂ is self‐assembled on the surface of oMMT, which forms a novel layered‐spherical nanostructure. The mechanical properties test results show that oMMT obviously improves the strength of EP and SiO₂ enhances its toughness, but oMMT‐SiO₂ exhibits a synergistic effect on toughening and reinforcing EP simultaneously. A pin‐on‐disc rig was used to test friction and wear loss of pure EP and EP nanocomposites. The tribological test results prove that these nanofillers with different shapes play different roles for improving the wear resistance of EP nanocomposites. Morphologies of the worn surfaces were studied further by scanning electron microscopy (SEM) observations, and it was clarified that the EP and EP nanocomposites undergo similar wear mechanisms. Copyright © 2006 John Wiley & Sons, Ltd.     

Electrical conductivity of poly(ethylene terephthalate)/expanded graphite nanocomposites prepared by in situ polymerization

Nanocomposites based on poly(ethylene terephthalate) (PET) and expanded graphite (EG) have been prepared by in situ polymerization. Morphology of the nanocomposites has been examined by electronic microscopy. The relationship between the preparation method, morphology, and electrical conductivity was studied. Electronic microscopy images reveal that the nanocomposites exhibit well dispersed graphene platelets. The incorporation of EG to the PET results in a sharp insulator‐to‐conductor transition with a percolation threshold (?_c) as low as 0.05 wt %. An electrical conductivity of 10^?3 S/cm was achieved for 0.4 wt % of EG. The low percolation threshold and relatively high electrical conductivity are attributed to the high aspect ratio, large surface area, and uniform dispersion of the EG sheets in PET matrix. © 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2012     

New insight into the crystallization behavior of poly(ethylene terephthalate)/clay nanocomposites

Crystallization behavior of poly(ethylene terephthalate) (PET)/clay nanocomposites has been investigated in terms of differential scanning calorimeter (DSC) analysis, polarizing optical microscopy (POM), and scanning electron microscopy (SEM) observation. The nanocomposites for investigation were prepared via in situ polycondensation. Crystalline morphologies were observed through POM and SEM. The nonisothermal and isothermal crystallization rates of different samples were determined for comparison based on DSC data. Secondary nucleation analysis was also performed based on bulk crystallization data derived from DSC analysis. The results revealed that nucleating abilities of montmorillonites (MMT) depended on the dispersion state of clay in matrix, the surface modification status, and the metallic derivatives released from MMT during in situ synthesis. The quantities of metallic elements released were measured by inductively coupled plasma (ICP) analysis. The results showed that the release of these metallic derivatives was also affected by surfactant molecules anchored on the surface of MMT. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 2380–2394, 2008     

Interfacial effect on confined crystallization of poly(ethylene oxide)/silica composites

The impact of nanoconfinement introduced by nanoparticles on polymer crystallization has attracted extensive attention because it plays an important role in the ultimate properties of polymer nanocomposites. In this study, interfacial and spatial confinement effects of silica (SiO₂) nanoparticles on the crystallization behaviors of poly(ethylene oxide) (PEO)/SiO₂ composites were systematically investigated by changing the size and concentration of SiO₂ in PEO matrix. The composites with high silica loadings exhibit two crystallization peaks of PEO as determined by differential scanning calorimetry. The first peak at 7–43 °C is related to the bulk PEO, while the second peak at ?20 to ?30 °C is attributed to the restricted PEO segments. Three‐layer (amorphous, interfacial, and bulk) model is proposed to interpret the confined crystallization of PEO/SiO₂ composites, which is supported by the results of thermogravimetric analysis and solid‐state ¹H nuclear magnetic resonance. In amorphous layer, most PEO segments are directly adsorbed on SiO₂ surface via hydrogen bonding. The interfacial PEO layer, which is nonuniform, is composed of crystallizable loops and tails extending from amorphous layer. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016 , 54, 414–423