Novel antimicrobial polyethylene composites prepared by metallocenic in situ polymerization with TiO2‐based nanoparticles

Polyethylene (PE) composites with titanium oxide (TiO₂) nanoparticles were produced via in situ polymerization representing a novel route to obtain antimicrobial polymeric materials. The TiO₂ nanoparticles synthesized by the sol–gel method were used either as‐synthesized or modified organically with hexadecyltrimethoxysilane (Mod‐TiO₂). These particles were added, together with the catalytic system (formed by a metallocenic catalyst and methylaluminoxane as cocatalyst), directly to the reactor, yielding in situ PE composites with 2 and 8 wt % content of nanofiller. The catalytic polymerization activity presented a slight decrease with the incorporation of the TiO₂ and Mod‐TiO₂ nanoparticles compared to polymerization without filler. Regarding the properties of the composites, crystallinity increased slightly when the different nanofillers were added, and the elastic modulus increased around 15% compared to neat PE. PE/TiO₂ nanocomposites containing 8 wt % of TiO₂ exposed to UVA irradiations presented antimicrobial activity against Escherichia coli. The PE/Mod‐TiO₂ nanocomposite with 8 wt % filler killed 99.99% of E. coli, regardless of light and time irradiation. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Effect of Surface Treatment of Titanium Dioxide Nanoparticles on Non-Isothermal Crystallization Behavior,Viscoelastic Transitions and Cold Crystallization of Poly(Ethylene Terephthalate) Nanocomposites

The effect of untreated and tri-n-octylphosphine oxide (TOPO) surface-treated TiO₂ nanoparticles when included as filler in poly(ethylene terephthalate) on its compatibility, non-isothermal crystallization behavior, viscoelastic transitions and cold crystallization has been studied. The effectiveness of the surface treatment has been studied using infrared spectrophotometry (FTIR) and thermogravimetric analysis (TGA). The effect of the untreated and surface-treated nanofiller content in the polymer, added by an extrusion process, on the non-isothermal crystallization has been studied by differential scanning calorimetry (DSC). The influence on the viscoelastic transitions and cold crystallization of PET nanocomposites has been studied through thermomechanical analysis (TMA). The surface treatment and the concentration of nanofiller influence the non-isothermal crystallization behavior, the viscoelastic transitions and the cold crystallization of the PET nanocomposites, enables us to evaluate the compatibility and the level of dispersion/aggregation of the nanofiller in the poly(ethylene terephthalate).     

Influence of fillers and additives on the cure kinetics of an epoxy/anhydride resin

The cure kinetics of a cycloaliphatic epoxy resin with and without additives and cured with an anhydride hardener was investigated by isothermal and nonisothermal differential scanning calorimetry (DSC).Dynamic measurements were used to predict the total heat of reaction of the epoxy resin as well as its activation energy based on the methods of Kissinger and Ozawa. With these methods the inhibition and acceleration effects of additives and fillers on the kinetics have been demonstrated. Additives for advanced processing and property upgrade were added in less than 2 wt.%, whereas fillers on base of SiO₂ were incorporated in more than 50 wt.%. The effect of SiO₂ surface treatment was also objective of this study.To describe the dependence of the conversion on time and temperature, isothermal DSC data were fitted to an autocatalytic model developed by Kamal and extended with a diffusion factor. The results show a very good agreement within the whole conversion range. Also the highly-filled system could be described very well by the phenomenological Kamal model.     

Nanofibrous polysulfone/TiO2 nanocomposites: Surface properties and their relation with E. coli adhesion

Solution blow spinning, SBS, was used to prepare fibrous films of thermoplastic nanocomposites with potential antibacterial properties based on polysulfone, PSF, filled with well dispersed TiO₂ nanoparticles. The PSF/TiO₂ nanocomposites were produced with different nanoparticles content up to 10% by weight. A wide characterization was carried out focusing on the morphology at the nanoscale, roughness, contact angles, and surface free energy. Cell adhesion was studied by inspection by scanning electron microscopy (SEM). A uniform dispersion of the nanofiller was achieved, with the nanoparticles evenly embedded in the polymer along the fibers when they were created during the blow spinning process. TiO₂ content influenced the topography of the films, most likely due to a direct effect on the solvent evaporation rate. The results obtained pointed out that an increase of the surface hydrophobicity as a result of the increased roughness induced by the presence of TiO₂ nanoparticles was the main contribution to the reduction of DH5α Escherichia coli cells adhesion. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017 , 55, 1575–1584     

TiO2 nanoparticles/poly(butylene adipate‐co‐terephthalate) bionanocomposite films for packaging applications

In this present study, biodegradable PBAT nanocomposites containing different weight percentages (1, 3, 5, 7, and 10% w/w) of TiO₂ nanoparticles were prepared by using solvent casting technique, chloroform as a solvent. The microstructure and morphology of the as‐synthesized poly(butylene adipate‐co‐terephthalate) (PBAT)/TiO₂ nanocomposite films were characterized by Fourier‐transform infrared, X‐ray diffraction, scanning electron microscopy, and transmission electron microscope. The thermal degradation of PBAT composites was studied by using thermogravimetric analysis. The mechanical strength of the films was improved by increasing TiO₂ concentration. Tensile strength increased from 32.60 to 63.26 MPa, respectively. Barrier properties of the PBAT/TiO₂ nanocomposites were investigated by using an oxygen permeability tester. The oxygen permeability (oxygen transmission rate) decreased with increasing the TiO₂ nanoparticle concentrations. The PBAT/TiO₂ nanocomposite films showed profound antimicrobial activity against both Gram‐positive and Gram‐negative foodborne pathogenic bacteria, namely, Escherichia coli and Staphylococcus aureus, to understand to the zone of inhibition. These results indicated that filler–polymer interaction is important and the role of the TiO₂ as a reinforcement in the nanocomposites was evident. Copyright © 2017 John Wiley & Sons, Ltd.     

Nucleation Activation and Spherical Crystals Morphology of LLDPE/LDPE/TiO2 Nanocomposites Prepared by Non-Isothermal Crystallization

The nucleation activation of TiO₂ nanoparticles in the linear low-density polyethylene (LLDPE)/low-density polyethylene (LDPE)/TiO₂ nanocomposites prepared by non-isothermal crystallization, the spherical crystals morphology of the etched LLDPE/LDPE and LLDPE/LDPE/TiO₂ composites were investigated by differential scanning calorimetry (DSC) and field-emission scanning electron microscopy (FE-SEM), respectively. The results showed that the heterogeneous nucleation activation of TiO₂ nanoparticles was accelerated by the fast cooling rate. The spherical crystals in the LLDPE/LDPE and LLDPE/LDPE/TiO₂ composites were ascribed to the same crystal structure. It was worth to note that there was distinct difference between the morphology of the cocrystallization LLDPE/LDPE crystals and that of the independent crystallization LLDPE/LDPE crystals.     

Effect of the Presence of an Ester of Montanic Acids With Multifunctional Alcohols in the Composites of Titanium Dioxide Nanoparticles With Poly (Ethylene Terephthalate) in Their Non-Isothermal Crystallization

The effect of the addition of an ester of montanic acid with multifunctional alcohols in the effectiveness of the dispersion and compatibility of TiO₂ nanoparticles when included as filler in poly(ethyleneterephthalate) for composite production is studied through the study of the non-isothermal crystallization by differential scanning calorimetry (DSC). The application of the Avrami method enables to evaluate the compatibility and the level of dispersion/aggregation of the nanofiller in the poly(ethyleneterephthalate) by the analysis of the temperature and enthalpy of crystallization, the kinetic parameters and the half-crystallization time.     

Cure behavior of diglycidylether of bisphenol A/trimethylolpropane triglycidylether epoxy blends initiated by thermal latent catalyst

Cure behaviors of diglycidylether of bisphenol A (DGEBA)/trimethylolpropane triglycidylether (TMP) epoxy blends initiated by 1 wt % N‐benzylpyrazinium hexafluoroantimonate (BPH) as a cationic latent catalyst were investigated using DSC and rheometer. This system showed more than one type of reaction and BPH could be excellent thermal latent catalyst without any co‐initiator. The cure activation energy (E_a) obtained from Kissinger method using dynamic DSC data was higher in DGEBA/TMP mixtures than in pure DGEBA. Rheological properties of the blend system were investigated under isothermal condition using a rheometer. The gel time was obtained from the analysis of storage modulus (G′), loss modulus (G″) and damping factor (tanδ). The crosslinking activation energy (E_c) was also determined from the Arrhenius equation based on the gel time and curing temperature. As a result, the crosslinking activation energy showed a similar behavior with that obtained from Kissinger method. And the gel time decreased with increasing TMP content, which could be resulted from increasing the activated sites by trifunctional epoxide groups and decreasing the viscosity of DGEBA/TMP epoxy blend in the presence of TMP. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 2114–2123, 2000     

In situ prepared PBSu/SiO2 nanocomposites. Study of thermal degradation mechanism

A series of nanocomposites consisted of poly(butylene succinate) (PBSu) and fumed silica nanoparticles (SiO₂) were prepared using the in situ polymerization technique. The amount of SiO₂ used directly affected the final molecular weight of the prepared polyesters. At a low SiO₂ content (0.5 wt.%) the molecular weight obtained was higher compared to neat PBSu, however at higher concentrations this was gradually reduced. The melting point of the matrix remained unaffected by the addition of the nanoparticles, in contrast to the crystallinity, which was dramatically reduced at higher SiO₂ contents. This was mainly due to the extended branching and cross-linking reactions that took place between the carboxylic end groups of PBSu and the surface silanols of the nanoparticles. Thermal degradation of the PBSu/SiO₂ nanocomposites was studied by determining theirs mass loss during heating. From the variations of the activation energies, calculated from the thermogravimetric curves, it was clear that nanocomposites containing 1 wt.% SiO₂ content had a higher activation energy compared to pure PBSu, indicating that the addition of the nanoparticles could slightly increase the thermal stability of the matrix. However, in PBSu/SiO₂ nanocomposite containing 5 wt.% SiO₂ the activation energy was smaller. This phenomenon should be attributed to the existence of extended branched and cross-linked macromolecules, which reduce the thermal stability of PBSu, rather than to the addition of fumed silica nanoparticles.     

The catalytic role of oxide in the thermooxidative degradation of poly(methyl methacrylate)-TiO2 nanocomposites

The influence of TiO₂ nanoparticles on the thermal degradation of poly(methyl methacrylate) (PMMA) was investigated by TGA. The studied materials were characterized by Py-GC-MS, TEM, SEM, TGA, DSC and TGA-MS. The PMMA-TiO₂ nanocomposites were prepared by melt blending with different (5, 10, 15 and 20 wt% TiO₂) loadings. According to TGA results and to the activation energy (determined by the model-free isoconversional method of Vyazovkin), the incorporation of 5 wt% of TiO₂ nanoparticles into PMMA stabilizes it by more than 40 °C. However, for higher loading contents, a catalytic effect on the thermal decomposition was observed which increased with the oxide content. The results obtained by Py-GC-MS showed clearly that TiO₂ increases the formation of methanol, methacrylic acid and propanoic acid methyl ester during the degradation of PMMA. This catalytic effect could be explained through the interaction of the methoxy group of the methacrylate function with the hydroxyl groups present at the surface of the oxide particles.     

Enhanced Visible‐Light‐Induced Photoelectrocatalytic Degradation of Methyl Orange by CdS Sensitized TiO2 Nanotube Arrays Electrode

In this work, CdS sensitized TiO₂ nanotube arrays (CdS/TiO₂NTs) electrode was synthesized with the CdS deposition on the highly ordered titanium dioxide nanotube arrays (TiO₂NTs) by sequential chemical bath deposition method (S‐CBD). The as‐prepared CdS/TiO₂NTs was characterized by field‐emission scanning electron microscopy (FE‐SEM) and X‐ray diffraction (XRD). The results indicated that the CdS nanoparticles were effectively deposited on the surface of TiO₂NTs. The amperometric I‐t curve on the CdS/TiO₂NTs electrode was also presented. It was found that the photocurrent density was enhanced significantly from 0.5 to 1.85 mA/cm² upon illumination with applied potential of 0.5 V at the central wavelength of 253.7 nm. The photoelectrocatalytic (PEC) activity of the CdS/TiO₂NTs electrode was investigated by degradation of methyl orange (MO) in aqueous solution. Compared with TiO₂NTs electrode, the degradation efficiencies of CdS/TiO₂NTs electrode increased from 78% to 99.2% under UV light in 2 h, and from 14% to 99.2% under visible light in 3 h, which was caused by effective separation of the electrons and holes due to the effect of CdS, hence inhibiting the recombination of electron/hole pairs of TiO₂NTs.     

TiO<Subscript>2</Subscript>/SiO<Subscript>2</Subscript> hybrid nanomaterials: synthesis and variable UV-blocking properties

Silica and core–shell structured titania/silica (TiO₂/SiO₂) nanoparticles with particles size ranging from tens to hundreds of nanometers were prepared and deposited onto cotton fabric substrates by sol–gel process. The morphologies of the nanoparticles were characterized by field-emission scanning electron microscope (FE-SEM). The photocatalytic decomposition properties as well as UV-blocking properties of the fabrics treated with SiO₂ and TiO₂/SiO₂ nanoparticles were investigated.     

Synthesis of polyethylene‐octene elastomer/SiO2‐TiO2 nanocomposites via in situ polymerization: Properties and characterization of the hybrid

In this study, a silicic acid and tetra isopropyl ortho titanate ceramic precursor and a metallocene polyethylene‐octene elastomer (POE) or acrylic acid grafted metallocene polyethylene‐octene elastomer (POE‐g‐AA) were used in the preparation of hybrids (POE/SiO₂? TiO₂ and POE‐g‐AA/SiO₂? TiO₂) using an in situ sol‐gel process, with a view to identifying a hybrid with improved thermal and mechanical properties. Hybrids were characterized using Fourier transform infrared spectroscopy, ²⁹Si solid‐state nuclear magnetic resonance (NMR), X‐ray diffraction, differential scanning calorimetry, thermogravimetry analysis, dynamic mechanical thermal analysis, and Instron mechanical testing. Properties of the POE‐g‐AA/SiO₂? TiO₂ hybrid were superior to those of the POE/SiO₂? TiO₂ hybrid. This was because the carboxylic acid groups of acrylic acid acted as coordination sites for the silica‐titania phase to allow the formation of stronger chemical bonds. ²⁹Si solid‐state NMR showed that Si atoms coordinated around SiO₄ units were predominantly Q₃ and Q₄. The 10 wt % SiO₂? TiO₂ hybrids gave the maximum values of tensile strength and glass transition temperature in both POE/SiO₂? TiO₂ and POE‐g‐AA/SiO₂? TiO₂. It is proposed that above this wt %, excess SiO₂? TiO₂ particles caused separation between the organic and inorganic phases. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 1690–1701, 2005     

Fabrication and characterization of electrospun silk fibroin/TiO2 nanofibrous mats for wound dressings

Silk fibroin (SF) nanofibrous mats were fabricated via electrospinning process. These fibers were blended with TiO₂ nanoparticles (TiO₂ NPs). The influence of TiO₂ NPs on the nanofibrous matrices was investigated by scanning electron microscopy (SEM), transmission electron microscopy, energy‐dispersive X‐ray, and thermogravimetric analysis. The SEM images revealed that the average diameter of the SF/TiO₂ fibers was 385 ± 63 nm when the concentration of SF was up to 10% (w/v). Infrared spectra showed that the β‐sheet structure of the silk fibroin increased after acetone treatment. These SF/TiO₂ nanofibrous mats exhibited higher equilibrium water content and water vapor transmission rate than hydrocolloid dressing. The hemocompatibility and cytocompatibility of SF/TiO₂ nanofibrous mats were evaluated by complete blood count, cell attachment, and the spreading of L929 fibroblasts. These SF/TiO₂ nanofibrous mats exhibited antibacterial activity against Escherichia coli under UV irradiation. Thus, these novel nanocomposite mats may be used for biomedical applications such as wound dressing. Copyright © 2011 John Wiley & Sons, Ltd.     

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     

Preparation of Ni/TiO2 Nanoparticles and Their Catalytic Performance on the Thermal Decomposition of Ammonium Perchlorate

Metal/oxide nanoparticles are attractive because of their special structure and better properties. The Ni/TiO₂ nanoparticles were prepared by a liquid phase chemical reduction method in this paper. The obtained‐products were characterized by inductively coupled plasma (ICP), X‐ray diffraction (XRD), high‐resolution transmission electron microscopy (HRTEM) and scanning electron microscopy (SEM). The results show that Ni particles in Ni/TiO₂ nanoparticles exhibit better dispersion and the size of most Ni particles is 10 nm or so. The catalytic activity of Ni/TiO₂ nanoparticles on the thermal decomposition of ammonium perchlorate (AP) was investigated by simultaneous thermogravimetry and differential thermal analysis (TG‐DTA). Results show that composite process of Ni and TiO₂ can improve the catalytic activity of Ni nanoparticles on the thermal decomposition of AP, which is mainly attributed to the improvement of Ni dispersion in Ni/TiO₂ nanoparticles. The catalytic activity of Ni/TiO₂ nanoparticles increases with increasing the weight ratio of Ni to AP.     

Kinetics studies on the accelerated curing of liquid crystalline epoxy resin/multiwalled carbon nanotube nanocomposites

A new class of nanocomposite has been fabricated from liquid crystalline (LC) epoxy resin of 4,4′‐bis(2,3‐epoxypropoxy) biphenyl (BP), 4,4′‐diamino‐diphenyl sulfone (DDS), and multiwalled carbon nanotubes (CNTs). The surface of the CNTs was functionalized by LC epoxy resin (ef‐CNT). The ef‐CNT can be blended well with the BP that is further cured with an equivalent of DDS to form nanocomposite. We have studied the curing kinetics of this nanocomposite using isothermal and nonisothermal differential scanning calorimetry (DSC). The dependence of the conversion on time can fit into the autocatalytic model before the vitrification, and then it becomes diffusion control process. The reaction rate increases and the activation energy decreases with increasing concentration of the ef‐CNT. At 10 wt % of ef‐CNT, the activation energy of nanocomposite curing is lowered by about 20% when compared with the neat BP/DDS resin. If the ef‐CNT was replaced by thermal‐insulating TiO₂ nanorods on the same weight basis, the decrease of activation energy was not observed. The result indicates the accelerating effect on the nanocomposite was raised from the high‐thermal conductivity of CNT and aligned LC epoxy resin. However, at ef‐CNT concentration higher than 2 wt %, the accelerating effect of ef‐CNTs also antedates the vitrification and turns the reaction to diffusion control driven. As the molecular motions are limited, the degree of cure is lowered. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2011     

Effect of TiO2 nanoparticles on structure and properties of high density polyethylene membranes prepared by thermally induced phase separation method

Polyethylene/TiO₂ membranes were fabricated via thermally induced phase separation (TIPS) method. A set of characterization tests including FE‐SEM, EDX, XRD, DSC, TGA, DMA, mechanical test and relative pure water flux for characterization of membranes were carried out to investigate the effect of TiO₂ nanoparticles on membrane properties. The results of EDX, XRD and TGA analyses confirmed the presence of TiO₂ nanoparticles in the polymer matrix. The results of DSC analysis revealed that the melting point as well as the crystallinity of the membranes increased slightly with increasing TiO₂ content. However, the glass transition temperature of the membranes was not affected by the presence of particles. Addition of nanoparticles also increased storage modulus, loss modulus and tensile strength at break of the membranes due to the stiffness improvement effect of inorganic TiO₂. Finally, it was observed that incorporation of the nanoparticles improved pure water flux of the membranes. Copyright © 2015 John Wiley & Sons, Ltd.     

Effect of Pickering emulsion on the mechanical performances and fracture toughness of epoxy composites

The improvement of mechanical properties and toughness of nanoparticles for epoxy composites was mostly dependent on the disperse state of nanoparticles in epoxy matrices. When the content of nanoparticles was higher than a threshold value, it was easy to aggregate and then affect the improvement effect. Pickering emulsion was prepared using SiO₂ nanoparticles as emulsifier and functional monomer as oil phase. The influence of Pickering emulsion on the curing process was investigated. The effect of Pickering emulsion on the mechanical properties, toughness, and glass transition temperature (Tg) was studied. Impact and tensile fracture surface were observed by scanning electron microscopy (SEM). Results from differential scanning calorimeter (DSC), tensile, impact, and fracture toughness tests are provided. The results indicated that the introduction of Pickering emulsion can eliminate the residual stress and accelerate curing reaction. Epoxy composites were capable of increasing tensile strength by up to 29.9%, impact strength of three‐fold, fracture toughness of 35%, and Tg of 20.7°C in comparison with the reference sample. SEM images showed that SiO₂ nanoparticles exhibit a good dispersion in epoxy matrix. The increases in mechanical properties, toughness, and Tg of epoxy composites were attributed to the “Second Phase Toughness” mechanism.     

A 2D Graphitic-Polytriaminopyrimidine (g-PTAP)/Poly(ether-block-amide) Mixed Matrix Membrane for CO2 Separation

Poly(ether-block-amide)/g-PTAP mixed matrix membranes (MMMs) were developed by incorporating different wt.% (1–10%) of a novel 2D g-PTAP nanofiller and its effects on membrane structure and gas permeability were studied. The novel 2D material g-PTAP was synthesized and characterized by various analytical techniques including field-emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and Raman spectroscopy. The fabricated MMMs were investigated to study the interaction and compatibility between Pebax and g-PTAP. The MMMs showed an effective integration of g-PTAP nanofiller into the Pebax matrix without affecting its thermal stability. Gas permeation experiments with MMMs showed improved CO₂ permeability and selectivity (CO₂/N₂) upon incorporation of g-PTAP in the Pebax polymer matrix. The maximum CO₂ permeability enhancement from 82.3 to 154.6 Barrer with highest CO₂/N₂ selectivity from 49.5 to 83.5 were found with 2.5 wt.% of nanofiller compared to neat Pebax membranes.