In situ polymerization of polyethylene/clay nanocomposites using a novel clay‐supported Ziegler‐Natta catalyst

Polyethylene/clay nanocomposites (PECNC) were synthesized via in situ Ziegler‐Natta catalyst polymerization. Activated catalyst for polymerization of ethylene monomer has been prepared at first by supporting of the cocatalyst on the montmorillonite (MMT) smectite type clay and then active complex for polymerization formed by reaction of TiCl₄ and aluminum oxide compound on the clay. Acid wash treatment has been used for increasing hydroxyl group and porosity of the clay and subsequently activity of the catalyst. The nanostructure of composites was investigated by X‐ray diffraction (XRD) and transmission electron microscopy (TEM). Obtained results show that silica layers of the mineral clay in these polyethylene/nanocomposites were exfoliated, intercalated, and uniformly dispersed in the polyethylene matrix even at very high concentration of the clay. Thermogravimetric analysis (TGA) shows good thermal stability of the PECNCs. Differential scanning calorimeter (DSC) results reveal considerable decrease in the crystalline phase of the PECNC samples. Results of permeability analysis show an increase in barrier properties of PECNC films. POLYM. COMPOS., 2009. © 2009 Society of Plastics Engineers     

Synthesis of polypropylene/clay nanocomposites using bisupported Ziegler‐Natta catalyst

In this article, preparation of polypropylene/clay nanocomposites (PPCNC) via in situ polymerization is investigated. MgCl₂/montmorillonite bisupported Ziegler‐Natta catalyst was used to prepare PPCNC samples. Montmorillonite (MMT) was used as an inert support and reinforcement agent. The nanostructure of the composites was characterized by X‐ray diffraction, scanning electron microscopy, and transmission electron microscopy techniques. Obtained results showed that silica layers of the MMT in these PPCNC were intercalated, partially exfoliated, and uniformly dispersed in the polypropylene matrix. Thermogravimetric analysis showed good thermal stability for the prepared PPCNC. Differential scanning calorimetric was used to investigate both melting and crystallization temperatures, as well as the crystallinity of the PPCNC samples. Results of permeability analysis showed significant increase in barrier properties of PPCNC films. Effective parameters on molecular weight and flow ability of produced samples such as Al/Ti molar ratio and H₂ concentration were also investigated. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Reactive extrusion of polystyrene/polyethylene blends

The feasibility of inducing beneficial changes to polystyrene/polyethylene (PS/PE) blends via reactive extrusion processes is considered. Experiments have been conducted on 50:50 wt.% PS/PE blends that were treated with different levels of dicumyl peroxide and triallyl isocyanurate coupling agent. Both a low molecular weight and a high molecular weight blend series have been investigated. A “more reactive” polystyrene was synthesized by incorporation of a minor amount of ortho-vinylbenzaldehyde. Blends containing this modified polystyrene were subjected to identical processing' conditions on a counter-rotating twin screw extruder. Examination of the tensile properties of the extrusion products suggested that a judicious level of peroxide and coupling agent additives would be beneficial to the ultimate physical properties. The quantity of styrenic phase becoming chemically grafted to the polyethylene matrix was influenced most strongly by the level of the chosen coupling agent. As determined by scanning electron microscopy, the phase morphologies of the tensile test fracture surfaces were strongly dependent upon the reaction extrusion process; those extruded blends that had been exposed to the additive pre-treatment displayed substantially finer microstructure. The enthalpy of fusion of the polyethylene melting endotherm was likewise influenced by both the presence or absence of the additives as well as the molecular weight nature of the blend series.     

Fabrication of superhydrophobic silica‐based surfaces with high transmittance by using polypropylene and tetraeyhoxysilane precursors

Preparation of superhydrophobic silica‐based surfaces via sol–gel process by adding polyethylene glycol (PEG) polymer into the precursor solution has been developed. Surface roughness of the films was obtained by removing the organic polymer at 500°C and then the hydrophobic groups bonded onto the films were obtained by self‐assembly modification with a monolayer. Characteristic properties of the as‐prepared films were analyzed by contact angle measurements, scanning electron microscopy, atomic force microscopy, UV–vis scanning spectrophotometer, and X‐ray photoelectron spectrophotometer. The experimental parameters were varied by the type of silane species, the R ratio, the hydrolysis time of the precursor solution, the molecular weight of PEG, the pH value of mixing solution, and the different reagents for modification. The results showed that optimum ratio of TEOS/H₂O/ethanol in the sol–gel process for precursor solution was set to 1/10/4. The better contact angles of the films can be obtained by the acid catalyst reaction, especially the pH value of mixing solution was adjusted to 0. When the as‐prepared rough films were modified with (tridecafluoro‐1,1,2,2‐tetrahydrooctyl) dimethylchlorosilane (TFCS), the contact angle of the film can be promoted to 150.4°, and the transmittance of the films in the visible light region was greater than 94.5%. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Improving the hydrophobic,water barrier and crystallization properties of poly(ethylene terephthalate) by incorporating monodisperse SiO2 particles

This paper details an improvement in the properties of poly(ethylene terephthalate) (PET) with respect to its use in petroleum engineering by incorporating uniform (monodisperse; 35 to 380 nm) silica (SiO₂) particles and polystyrene? SiO₂ core–shell particles by melt mixing. The resulting high‐performance nanocomposite (SNPET) films are presented. The results of contact angle and water absorption tests showed that the contact angle of the amorphous SNPET films increased from 72° to 118.5° as the core–shell particle load increased from 0 to 6.0 wt%. The contact angle reached 128.0° when the films were annealed. Decreasing the SiO₂ particle size demonstrably improved the SNPET film hydrophobicity and lowered the water diffusion coefficient, i.e. SiO₂ particles of 35 nm in size gave the greatest enhancement of water barrier properties. Results of transmission electron microscopy, scanning electron microscopy, atomic force microscopy and optical measurements showed the homogeneous particle dispersion and nanostructure in the SNPET films. Their transparency and haziness increased as the particle size decreased. Use of such core–shell structures meant that the uniform (monodisperse) SiO₂ particles could be dispersed homogeneously in PET, and effectively improved the surface, thermal and crystallization behavior of SNPET films to produce materials with high barrier stability against water. Copyright © 2010 Society of Chemical Industry     

Bi-supported Ziegler–Natta TiCl4/MCM-41/MgCl2 (ethoxide type) catalyst preparation and comprehensive investigations of produced polyethylene characteristics

Bi-supported Ziegler–Natta catalysts (TiCl₄/MCM-41/MgCl₂ (ethoxide type)) were synthesized to improve the morphology and the properties of polyethylene. The morphology control is a crucial issue in polymerization process, while tailoring the properties of polymers is needed for specific applications. The catalysts were synthesized in different ratios of two supports with impregnation method. The polymerization process was carried out in atmospheric slurry reactor. The catalysts were characterized with scanning electron microscopy - energy dispersive X-ray spectroscopy (SEM–EDX), inductively coupled plasma, Fourier transform infrared spectrometry (FTIR), and Brunauer-Emmett-Teller (BET) methods. The polymers were analyzed with scanning electron microscopy (SEM), thermogravimetric analysis (TGA), differential scanning calorimetry, FTIR, and tensile-strength analyses. Ubbelohde viscometer and frequency sweep measurements showed that the synthesized polymers are ultra-high-molecular-weight polyethylene. Mechanical properties of polymers showed higher Young's modulus in samples containing MCM-41, having higher thermal stability supported by TGA analysis. SEM images of bi-supported catalyst showed a controlled spherical morphology with uniform size distribution. SEM analysis support that the polymers replicate their morphology from catalyst, improving their morphology comparing to MgCl₂-supported catalyst. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48553.     

Functionalized graphene nanoplatelets as a barrier enhancing filler in organic photovoltaic encapsulant

This research work has concerned the development of polymer films, reinforced with graphene nanoplatelets (GNP) for use as encapsulating films for organic photovoltaic (OPV) cells. The aim of this work was to investigate the effects of concentrations and orientations of GNP on mechanical, optical, and barrier properties of polymer composite films. In this regard, the neat GNP was modified with Fe₃O₄ prior to mixing with acrylate-based monomers. The mixture was then cured by photo-polymerization with and without the application of magnetic fields. Changes in orientation of the functionalized GNP with the direction of applied magnetic fields were analyzed by optical microscopy, scanning electron microscopy, and transmission electron microscopy. From the results, it was found that by inducing the orientation of functionalized GNP to the horizontal direction (with respect to the OPV cell), the great enhancement in tensile and barrier properties of the polymer composite films was achieved. This led to the longer performance of the OPV cell encapsulated with the nanocomposite film with 0.1 phr of the horizontally oriented GNP in comparison with the OPV cell encapsulated with the film reinforced with randomly oriented GNP at the same content.     

Pyrolysis-gasification of plastics, mixed plastics and real-world plastic waste with and without Ni-Mg-Al catalyst

Polypropylene, polystyrene, high density polyethylene and their mixtures and real-world plastic waste were investigated for the production of hydrogen in a two-stage pyrolysis-gasification reactor. The experiments were carried out at gasification temperatures of 800 or 850 °C with or without a Ni-Mg-Al catalyst. The influence of plastic type on the product distribution and hydrogen production in relation to process conditions were investigated. The reacted Ni-Mg-Al catalysts were analyzed by temperature-programmed oxidation and scanning electron microscopy. The results showed that lower gas yield (11.2 wt.% related to the mass of plastic) was obtained for the non-catalytic non-steam pyrolysis-gasification of polystyrene at the gasification temperature of 800 °C, compared with the polypropylene (59.6 wt.%) and high density polyethylene (53.5 wt.%) and waste plastic (45.5 wt.%). In addition, the largest oil product was observed for the non-catalytic pyrolysis-gasification of polystyrene. The presence of the Ni-Mg-Al catalyst greatly improved the steam pyrolysis-gasification of plastics for hydrogen production. The steam catalytic pyrolysis-gasification of polystyrene presented the lowest hydrogen production of 0.155 and 0.196 (g H₂/g polystyrene) at the gasification temperatures of 800 and 850 °C, respectively. More coke was deposited on the catalyst for the pyrolysis-gasification of polypropylene and waste plastic compared with steam catalytic pyrolysis-gasification of polystyrene and high density polyethylene. Filamentous carbons were observed for the used Ni-Mg-Al catalysts from the pyrolysis-gasification of polypropylene, high density polyethylene, waste plastic and mixed plastics. However, the formation of filamentous carbons on the coked catalyst from the pyrolysis-gasification of polystyrene was low.     

Polypyrrole film architectures influence on platinum nanoparticles efficiency in ethanol electrooxidation

The electrodeposition of polypyrrole films from aqueous surfactant solution through a two‐dimensional polystyrene template onto indium‐tin oxide substrate has been investigated. The polymer grows in the interstitial spaces of the self‐assembled polystyrene spheres, which were subsequently removed by dissolution in toluene. The new obtained surface was characterized by scanning electron microscopy and atomic force microscopy. Platinum nanoparticles were deposited onto the nanostructured polypyrrole electrode and used as a catalyst for the oxidation of ethanol for direct ethanol fuel cells. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41375.     

Rice bran‐filled biodegradable low‐density polyethylene films: Development and characterization for packaging applications

Rice bran was incorporated into low‐density polyethylene (LDPE) at different concentrations by compounding in a twin‐screw extruder and blown into films of uniform thickness. The rice bran incorporation influenced physical, mechanical, barrier, optical, thermal properties, and biodegradation of LDPE. The mechanical and optical properties decreased as the percentage of rice bran increased. The effect of rice bran on the morphology of LDPE blends was examined using scanning electron microscopy. Oxygen transmission rate and water vapor transmission rate increased with the increased content of rice bran. Addition of rice bran did not alter the melting temperature (T_m) of the blends; however the thermal stability decreased, while glass transition temperature (T_g) increased. Kinetics of thermal degradation was also investigated and the activation energy for thermal degradation indicated that for up to 10% filler addition, the dispersion and interfacial adhesion of rice bran particles in LDPE was good. Aerobic biodegradation tests using municipal sewage sludge and biodegradation studies using specific microorganism (Streptomyces species) revealed that the films are biodegradable. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 4514–4522, 2006     

Preparation of Starch/PVA/CaCO3 Nanobiocomposite Films: Study of Fire Retardant,Thermal Resistant,Gas Barrier and Biodegradable Properties

Starch/PVA/CaCO₃ nanobiocomposite films were prepared by the solution casting method. The prepared nanobiocomposite films were characterized by Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM) and selected area electron diffraction (SAED) methods. The fire retardant, tensile strength and thermal properties of nanobiocomposite films were enhanced with increasing percentage of CaCO₃. When the concentration of nano-CaCO3 was increased, the oxygen permeability of starch/PVA/CaCO₃ was reduced. The increase in fire retardant and oxygen barrier properties along with improvement in thermal and tensile properties of nanobiocomposite may enable the material suitable for packaging application.     

Effect of org-titanium phosphonate on the properties of chitosan films

A new type of titanium glycine-N,N-dimethylphosphonate Ti[(O₃PCH₂)₂NCH₂COOH] (TGDMP), with the functional groups –COOH, has been prepared first and then characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and transmission electron microscopy (TEM). Subsequently, chitosan/titanium glycine-N,N-dimethylphosphonate (CS/TGDMP-n) nanocomposite films of various compositions were prepared by solution casting method. The structure, morphology, and properties of nanocomposite films were investigated by FTIR, XRD, scanning electron microscopy (SEM), thermal gravimetric analysis (TGA), and tensile tests. The results showed that the mechanical properties of chitosan films were improved by the incorporation of TGDMP, and the samples kept at moisture environment showed the larger elongation and lower tensile strength than the dried counterparts. In addition, the CS/TGDMP-n films exhibited higher thermal stability and better moisture barrier property than neat CS films.     

High density polyethylene/polystyrene blends: Phase distribution morphology,rheological measurements,extrusion, and melt spinning behavior

An experimental study of the development of phase morphology, rheological properties, and processing behavior of mechanical blends of a polystyrene (PS) and a high density polyethylene (PE) is presented. Phase morphologies were determined by scanning electron microscopy for (i) products prepared in a screw extruder/static mixer system, (ii) samples removed from a cone-plate viscometer, (iii) extrudates, and (iv) melt spun fibers. Disperse phase dimensions were measured. The values varied from 1–5 μm in the products from static mixers. The dimensions of the dispersed phase in the blend products from the cone plate and capillary die were of the same order. The melt-spun fibers exhibited disperse phase dimensions as low as 0.35 μm. Polystyrene was extracted from the blend fibers producing small diameter, PE fibrils, or minifibers. Both the initial melts and the blends were rheologically characterized. The shear viscosity and principal normal stress difference N₁ exhibit maxima and minima when plotted as a function of composition. The characteristics of extrudates and melt spinning behavior of the blends were investigated. The shrinkage of extrudates of PE is much greater than PS. Additional small amounts of PE to PS greatly increase its shrinkage. Addition of PE to PS initially increases extrudate swell, though the swell shows maxima and minima when considered as a function of composition. The positions of the maxima and minima correspond to those of N₁. The onset of draw resonance has been investigated in isothermal melt spinning. Wide angle X-ray diffraction studies have been carried out on blend fibers and the orientation of the crystalline polyethylene regions has been determined as a function of process conditions. This orientation decreases rapidly with the addition of polystyrene when the melt-spun filaments are compared at the same spinline stress or drawdown ratio.     

Improved Electret Properties of Poly(Vinylidene Fluoride)/Lithium Niobate Nanocomposites for Applications in Air Filters

In this work, the electret properties of poly(vinylidene fluoride) (PVDF)/lithium niobate (LiNbO₃, LN) nanocomposites are systematically studied. The LN nanoparticles are fabricated by hydrothermal synthesis followed by melt‐reaction. Their morphology and crystalline structures are characterized by scanning electron microscopy (SEM) and X‐ray diffraction (XRD). The PVDF/LN nanocomposite films are prepared by solution casting with N,N‐dimethylformamide (DMF) as the solvent or melt molding. The crystalline phases of PVDF in both pure samples and nanocomposites are checked by XRD and Fourier transform infrared spectroscopy (FTIR). The measurements of the dielectric and electret properties show that the LN nanoparticles significantly increase the dielectric permittivity (ε) and the thermally stimulated discharge current (TSDC) of the samples. Such materials have potential applications including for air filters and power generators. A demonstration shows that after the same charging process, the PVDF/LN nanocomposites can absorb larger amount of polystyrene (PS) foam microparticles or micrometer size test dusts than the pure PVDF.     

Development of blown film linear low-density polyethylene–clay nanocomposites: Part A: Manufacturing process and morphology

In this study, linear low-density polyethylene (LLDPE)/clay nanocomposites with different clay contents were prepared by melt intercalation using two different compatibilizers: maleic anhydride grafted styrene–ethylene–butylene–styrene and maleic anhydride grafted polyethylene (PE-g-MA). Melt intercalation was achieved by twin extrusion and nanocomposite films were produced by blown film extrusion. Effects of clay and compatibilizer fractions and type of compatibilizer on the structure, permeability, and the barrier properties of the nanocomposite films were investigated. PE-g-MA was shown to notably improve the dispersion of clay layers in the polyethylene matrix, and this was examined by atomic force microscopy and X-ray diffraction. The latter tests have also highlighted the importance of the screw configuration: the presence of mixing elements favors the dispersion and distribution of nanoclay. Moreover, differential scanning calorimetry results have shown no significant effect of the clay on the crystallinity of the composite while thermogravimetric analysis tests have demonstrated a decrease of onset and peak of decomposition temperatures. Finally, barrier properties toward water vapor transmission were measured. It was proven that not also clay, but the compatibilizer participated in decreasing the permeability of the film. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48589.     

Nature of activating effect of two‐step polymerization of propylene

The prepolymerization effect on propylene polymerization in the presence of a TiCl₃‐based catalyst, modified by di‐n‐buthyl ether, was studied. The influence of prepolymerization on the electron spin resonance spectra and morphology of the catalyst, as well as the properties and the morphology of both prepolymer and regular polymerization products, was investigated. The polymer morphology was evaluated through scanning electron microscopy, polymer bulk density, and particle size distribution. Some evidence of the enhancement effect of prepolymerization on the catalyst activity and stereospecificity was obtained. No influence from prepolymerization was observed on molecular weight and its distribution, melting point, and crystallinity of polypropylene. These findings, when discussed in connection with the morphology results of the catalyst and prepolymer, showed that the prepolymerization performed at mild reaction conditions prevents fast and extensive “fragmentation” of the original catalyst agglomerates. The more controlled breakup of the catalyst particles in the course of slowed growth of prepolymer exposes the occluded catalyst fragments with uniform size and prevents their reagglomeration. Resulting from the above, catalyst homogeneity, catalyst activity, and polymer morphology are improved. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 353–359, 1999     

Preparation of manganese oxide–polyethylene oxide hybrid nanofibers through in situ electrospinning

Manganese oxide nanoparticles–polyethylene oxide nanofibers as organic–inorganic hybrid were prepared via in situ electrospinning. Thus, electrospinning of polyethylene oxide solution with different manganese chloride concentration was carried out in gaseous ammonia atmosphere containing oxygen. The reaction of manganese chloride with ammonia produces manganese hydroxide, and then oxygen in the reaction media reacts with manganese hydroxide to yield manganese oxide. These two reactions occur during fiber formation. Transmission electron microscopy and scanning electron microscopy showed that manganese oxide (MnO₂) nanoparticles were formed on the produced nanofibers of 100–600 nm in diameter. The existence of the formed MnO₂ was also proved by X‐ray diffraction analysis, and it showed that the λ‐MnO₂ nanoparticles were produced. Differential scanning calorimetry (DSC) analysis was used to determine the melting point and to calculate the crystallinity of the produced hybrid nanofibers. The DSC and thermogravimetric analysis results of the obtained nanofibers were compared with those of the nanofibers produced in electrospinning of pure polyethylene oxide solution. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Performance of multilayer films using maleated linear low-density polyethylene blends

Blends of linear low-density polyethylene (LLDPE) and linear low-density polyethylene grafted maleic anhydride (LLDPE-gMA) were prepared by melt mixing and then coextruded as external layers, with a central layer of polyamide (PA) on three-layer coextruded flat films. Blends with contents of 0% to 55 wt% of maleated LLDPE, on the external layers, were analyzed. The T-peel strength and oxygen and water vapor transmission rate of the films were measured. The surfaces of the peeled films were characterized using attenuated total reflection infrared spectroscopy (FTIR-ATR) and scanning electron microscopy (SEM). The observed increase in T-peel strength of the films with 10% and higher levels of maleated LLDPE in the blend suggests good interfacial adhesion between layers. This sharp increase in peel strength appears to be associated, besides interdiffusion, with specific interactions between polymers, as the bond formation between maleic anhydride and the polyamide end groups by in situ block copolymer formation across the interface. No significant modifications in oxygen barrier properties of the films were observed; however, the use of higher contents of LLDPEgMA, even though it increases the adhesion performance, also increases the water vapor transmission rate by a reduction in the degree of crystallinity.     

Compatibilization of a polystyrene-polyethylene blend through reactive processing in a twin screw extruder

Direct grafting of polystyrene onto polyethylene has been carried out in a twin screw extruder with an organic peroxide and a crosslinking co-agent. The reaction extruded blends exhibited enhancement in impact properties at an optimum level of peroxide and co-agent. Further improvement was achieved by introducing styrene monomer into the system during reactive extrusion. The structure and morphology of the blends were studied using differential scanning calorimetry, scanning electron microscopy, infrared spectroscopy, and size exclusion chromatography.     

Characterization of PEO-PAN hybrid solid polymer electrolytes

Hybrid solid polymer electrolytes (HSPE) of high ionic conductivity were prepared using polyethylene oxide (PEO), polyacrylonitrile (PAN), propylene carbonate (PrC), ethylene carbonate (EC), and LiClO₄. These electrolyte films were dry, free standing, and dimensionally stable. The HSPE films were characterized by constructing symmetrical cells containing nonblocking lithium electrodes as well as blocking stainless steel electrodes. Studies were made on ionic conductivity, electrochemical reaction, interfacial stability, and morphology of the films using alternating current impedance spectroscopy, infrared spectroscopy, and scanning electron microscopy. The properties of HSPE were compared with the films prepared using (i) PEO, PrC, and LiClO₄; and (ii) PAN, PrC, EC, and LiClO₄. The specific conductivity of the HSPE films was marginally less. Nevertheless, the dimensional stability was much superior. The interfacial stability of lithium was similar in the three electrolyte films. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 65: 2191–2199, 1997