Abdellah Ajji

Polytechnique Montréal, Montréal, Quebec, Canada

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Publications (183)370.44 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: In this study, the seal behavior of toughened blends of poly(lactic acid) (PLA) and polycaprolactone (PCL) was investigated in details. The blended samples were prepared using melt blending in a twin-screw extruder and were processed in the form of cast films of about 30 μm in thickness. Scanning electron microscopy (SEM) study of the morphology of the blends shows that laminar morphology develops in blends of 20% and 40% dispersed phase. Analysis of the thermal behavior of the blends using DSC thermograms reveals significant effect of blending on hindering the crystallization of PCL, resulting in lower crystallinity for samples with high PLA content. Latter provide blends with more amorphous phase and chain mobility, which help lowering the Seal and Hot-tack initiation temperatures. Blending is shown to decrease Seal and Hot-tack initiation temperatures up to 30 °C compared to neat PLA. In addition, this technique is proven to be successful to increase the Hot-tack strength of the blends to a comparative level to commercially available seal grade resins at about 1100 g/25.4 mm for PCL content of 40%. The results indicate that elongation at break increases from about 4% for pure PLA to almost 150% for the blend of 40% PCL and over 400% when PCL content reaches 60%. Higher toughness is an important property for a flexible package and prevents defects caused by its handling and storage conditions.
    Industrial Crops and Products 10/2015; 72:206-213. DOI:10.1016/j.indcrop.2014.11.021 · 2.84 Impact Factor
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    ABSTRACT: In this work, the effects of annealing conditions on the microstructure of polypropylene (PP) precursor films and further on the porous structure and permeability of stretched membranes were investigated. Combinations of WAXD, FTIR, DSC and DMA results clearly showed the crystalline orientation and crystallinity of the precursor film increased with annealing temperature, while the molecular chain entanglements in the amorphous phase decreased. Changes in the deformation behavior suggested more lamellar separation occurred for the films annealed at higher temperatures. Surface morphologies of the membranes examined by SEM revealed more pore number and uniform porous structure as the annealing temperature increased. In accordance with the SEM results, the permeability of the membranes increased with annealing temperature. On the other hand, it was found that 10 min was almost enough for the annealing process to obtain the microporous membranes with an optimal permeability.
    Chinese Journal of Polymer Science 07/2015; 33(7). DOI:10.1007/s10118-015-1643-x · 1.42 Impact Factor
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    ABSTRACT: The interfacial self-adhesion strength of polyethylene (PE) binary blends in temperatures higher than the melting point was investigated in relation to their components’ structures and elongational rheological properties. Four binary blends were prepared from the combination of a conventional polyethylene; LDPE or Ziegler-Natta LLDPE, with a metallocene catalyzed ethylene α-olefin copolymer; linear (Linear-m) or long chain branched (LCB-m). Interfacial adhesion was carried out by bringing two films into intimate contact under slight pressure and heat for 0.5 s. Adhesion strength was then measured by peeling immediately after sealing while the adherents were still in the molten state. Blending metallocene in 20, 40, and 60 wt% compositions with conventional PEs enhanced the self-adhesion. However, the adhesion strength of the blends containing 60 wt% metallocene resins was significantly lower than the adhesion strength of neat metallocene resins. This was interpreted to be due to the formation of a segregated layer of highly branched short chains of LDPE or Zn-LLDPE at the surface of films. The increase in adhesion strength of LDPE/Linear-m and Zn-LLDPE/Linear-m blends was more than LDPE/LCB-m and Zn-LLDPE/LCB-m blends. This was attributed to the faster reptation of linear chains, hence superior diffusion across the interface compared to LCB containing resin. The higher increase of adhesion strength for all compositions of LDPE blends was observed compared to their Zn-LLDPE counterparts. The temperature range in which the film showed a plateau of its highest adhesion strength was determined for all blend compositions. The results indicated that the temperature window of plateau adhesion strength for LDPE blends were broader than their Zn-LLDPE counterparts. Therefore, this work suggests that the final plateau temperature (T pf ) can be correlated with the area under stress–strain curve of the extensional rheological measurements, which is called toughness. Then, the higher melt toughness can result in a broader adhesion strength plateau.
    Rheologica Acta 05/2015; 54(5). DOI:10.1007/s00397-015-0843-1 · 1.78 Impact Factor
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    ABSTRACT: The present work deals with two different CdS nanostructures produced via hydrothermal and solvothermal decompositions of aminocaproic acid (ACA)-mixed Cd-thiourea complex precursor at 175 °C. Both nanostructures were extensively characterized for their structural, morphological and optical properties. The powder X-ray diffraction characterization showed that the two CdS nanostructures present a wurtzite morphology. Scanning electron microscopy and energy-dispersive X-ray characterizations revealed that the hydrothermal decomposition produced well-shaped CdS flowers composed of six dendritic petals, and the solvothermal decomposition produced CdS microspheres with close stoichiometric chemical composition. The UV-vis absorption and photoluminescence spectra of CdS dendritic flowers and microsphere nanostructures showed that both nanostructures present a broad absorption between 200 and 700 nm and exhibit strong green emissions at 576 and 520 nm upon excitations at 290 nm and 260 nm, respectively. The transmission electron microscopy (TEM) and Brunauer–Emmett–Teller (BET) characterizations confirmed that CdS microspheres were mesoporous and were composed of small nanocrystals. A possible growth mechanism in the formation of the CdS nanostructures was proposed based on morphology evolution as a function of the reaction time. Furthermore, the as-synthesized CdS nanostructures were found to exhibit highly efficient photocatalytic activities for the degradation of methyl orange (MeO) and rhodamine B (RhB) dyes.
    Journal of Nanoscience and Nanotechnology 04/2015; 15(4):2733-2741. DOI:10.1166/jnn.2015.9211 · 1.34 Impact Factor
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    ABSTRACT: The effect of dry grinding on the morphology and structure of kaolin particles treated with potassium acetate (KAc) and dimethyl sulfoxide (DMSO) has been investigated. After treatment with KAc, the d-spacing of kaolin increased from 0.72 to 1.03, 1.30, and 1.38 nm due to the combined effects of humidity and orientation of KAc molecules. The d-spacing was increased to 1.13 nm in the case of DMSO treatment. A combination of XRD, TGA, and FT-IR showed that the crystalline structure of kaolin–DMSO and kaolin–KAc were significantly altered by grinding. The intensity of XRD diffraction peaks of ground samples was decreased due to the deterioration of the crystalline structure, and for longer grinding times those peaks almost disappeared. After grinding, the dehydroxylation temperature generally shifted to lower values and a smaller weight loss was observed. The variations of particle size and surface characteristics were also investigated.
    Applied Clay Science 03/2015; 105. DOI:10.1016/j.clay.2014.12.026 · 2.70 Impact Factor
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    ABSTRACT: Plasticized chitosan and polyethylene blends were produced through a single-pass extrusion process. Using a twin-screw extruder, chitosan plasticization was achieved in the presence of an acetic acid solution and glycerol, and directly mixed with metallocene polyethylene, mPE, to produce a masterbatch. Different dilutions of the masterbatch (2, 5 and 10 wt% of plasticized chitosan), in the presence of ethylene vinyl acetate, EVA, were subsequently achieved in single screw film extrusion. Very small plasticized chitosan domains (number average diameter <5 μm) were visible in the polymeric matrix. The resulting films presented a brown color and increasing haze with chitosan plasticized content. Mechanical properties of the mPE films were affected by the presence of plasticized chitosan, but improvement was observed as a result of some compatibility between mPE and chitosan in the presence of EVA. Finally the incorporation of plasticized chitosan affected mPE water vapor permeability while oxygen permeability remained constant.
    Carbohydrate Polymers 03/2015; 117:177–184. DOI:10.1016/j.carbpol.2014.09.058 · 4.07 Impact Factor
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    ABSTRACT: In many industrial sectors, the surface properties of polymers are of particular importance. This applies, for instance, to painting, printing, and any coating on surface of polymeric objects. Hydrophilicity and wettability characteristics are known to be determined by the chemical makeup of the polymer surface. Blending with an additive or a polymer containing high-energy functional groups is widely recognized as a potential technique to overcome disadvantages of low surface energy of polymers due to its convenient processing. Surface migration of polyethylene glycol (PEG) in Polyethylene Terephthalate (PET) host was investigated using a low-molecular-weight PEG (8 kDa) because of its good hydrophilicity, low toxicity, biocompatibility, and chain mobility. A twin-screw extruder was used to blend the materials and prepare the polymer blend films. The results of surface characterizations showed that PEG renders the PET surface more hydrophilic, but not high enough for many applications. In a second approach, the addition of a third component, polystyrene (PS), to the blend in a small amount resulted in a remarkable surface enrichment of PEG at the polymer/air interface for the ternary polymer blend (PET-PEG-PS). Surface analysis revealed that the surface concentration of PEG in the ternary polymer blend film was significantly larger than that of the binary one. POLYM. ENG. SCI., 2014. © 2014 Society of Plastics Engineers
    Polymer Engineering and Science 02/2015; 55(2). DOI:10.1002/pen.23910 · 1.44 Impact Factor
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    Ali Moayeri · Abdellah Ajji
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    ABSTRACT: Conducting nanofibers of polyaniline (PANi) doped with camphor-10-sulfonic acid (HCSA), blended with poly(ethylene oxide) (PEO), and filled with 1-pyrenebutanoic acid, succinimidyl ester functionalized graphene (G-PBASE) have been fabricated using electrospinning. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), Fourier transforms infrared (FT-IR) and thermal gravimetric analyzer (TGA) was utilized to characterize the PANi/PEO/G-PBASE fibers morphology and properties. The observations show that electrospun fibers are highly interconnected and possess a relatively smooth surface. The average diameter of fibers was 222 ± 60 nm. The electrical conductivity of PANi/PEO and PANi/PEO/G-PBASE at room temperature was also studied. The unique nanostructured composite of PANi/PEO/G-PBASE with small loading of G-PBASE (5 wt.% relative to PANi) showed two order of magnitude enhancement in the electrical conductivity and one order of magnitude enhancement in thermal stability in comparison to PANi/PEO nanofibers.
    Synthetic Metals 02/2015; 200:7-15. DOI:10.1016/j.synthmet.2014.12.020 · 2.22 Impact Factor
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    ABSTRACT: In this work, we present the synthesis details of uniform shape and size-controlled titanium dioxide (TiO
    Green Processing and Synthesis 01/2015; DOI:10.1515/gps-2014-0092 · 4.09 Impact Factor
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    ABSTRACT: In this work, we describe a simple spin-coating deposition technique for lead sulphide (PbS) and cadmium sulphide (CdS) films from a methanolic metal–thiourea complex. The characterization of the films by X-ray diffraction and X-ray photoelectron spectroscopy techniques revealed that pure cubic phase PbS and CdS layers were formed via this method. As shown by atomic force microscopy and scanning electron microscopy results, both films were homogeneous and presented a smooth surface. Optical properties showed that the energy band gap of PbS and CdS films were around 1.65 and 2.5 eV, respectively. The PbS film is p-type in nature with an electrical conductivity of around 0.8 S/cm. The hole concentration and mobility were 2.35 × 1018 cm−3 and 2.16 × 10−3 cm2/V/s, respectively, as determined from Hall measurement. Both films were used to develop a thin film solar cell device of graphite/PbS/CdS/ITO/glass. Device characterization showed the power conversion efficiency of around 0.24 %. The corresponding open circuit voltage, short circuit current and fill factor were 0.570 V, 1.32 mA/cm2 and 0.32, respectively.
    Applied Physics A 12/2014; 117(4):1791-1799. DOI:10.1007/s00339-014-8659-x · 1.69 Impact Factor
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    Ahmad Zohrevand · Abdellah Ajji · Frej Mighri
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    ABSTRACT: Porous Nanocomposites films based on polypropylene (PP) and titanium dioxide (TiO2) nanoparticles were prepared by melt extrusion followed by uniaxial stretching. Effects of drawing temperature, extension rate, stretching ratio, and composition of the base films on final properties and microstructure of the stretched films were studied. Water vapor permeability results showed significant decrease in permeability of the films stretched at temperatures higher than 60 °C. Porosity, pore size, and water vapor transmission rate (WVTR) in the porous nanocomposite films had a direct relation with nanoparticle content, extension rate and stretching ratio. Study on morphology of the stretched films, using SEM, revealed that the pores form due to PP/TiO2 interfacial debonding at low stretching ratio. Higher stretching ratios causes an enlargement of the pores and formation of PP fibril structure parallel to the stretching direction. Quantification of dye adsorption revealed that the quantity of adsorbed dye increased with porosity and surface area of the pores.
    Polymer International 12/2014; 63(12). DOI:10.1002/pi.4761 · 2.25 Impact Factor
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    Hanan Abdali · Abdellah Ajji
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    ABSTRACT: The use of natural antimicrobial (AM) agents in the food packaging industry has been the focus of providing a safe and effective method in protecting and delivering food to the consumer. This study investigates natural materials such as clove bud powder (Syzygium aromaticum) to determine its AM activity against Gram-negative Escherichia coli (E. coli) (DH5α) and Gram-positive Listeria innocua (L. innocua) (LSPQ3284) and Staphylococcus aureus (S. aureus) (54–73) microorganisms. The lowest concentration of clove bud powder preventing the growth of a microorganism after 24 h incubation was considered as the minimum inhibitory concentration (MIC) and the values of the minimum bactericidal concentration (MBC) was determined as well. The clove bud powder was prepared and coated onto LDPE films to evaluate its AM activity for food packaging applications. It was found that the clove bud powder inhibited the growth of the tested microorganisms. An LDPE film embedded with the clove bud powder by coating twice showed the best AM effects against E. coli bacteria.
    Industrial Crops and Products 11/2014; 48. DOI:10.1016/j.indcrop.2014.09.050 · 2.84 Impact Factor
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    ABSTRACT: Hydrophilic microporous membranes were prepared based on polypropylene (PP) cast films blended with a commercial acrylic acid grafted polypropylene (PP-g-AA) via melt extrusion followed by grafting titanium dioxide (TiO2) nanoparticles on its surface, annealing and stretching. ATR-FTIR, XPS and EDS analyses showed that the hydrophilic segments of an amphiphilic modifier (PP-g-AA) acted as surface functional groups on the film surface. The results indicated that the presence of the modifier was very important for grafting TiO2 nanoparticles on the film surface. Compared to PP and PP/PP-g-AA blend films, the water contact angle decreased by a factor of 2.5 after grafting TiO2 on the surface of the films, meanwhile the water vapor permeability of the microporous membranes prepared from those films increased by a factor of 1.5. All these results indicated that the hydrophilicity of the modified PP membranes was improved.
    Polymer 11/2014; 55(23). DOI:10.1016/j.polymer.2014.09.069 · 3.77 Impact Factor
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    ABSTRACT: Kaolin particles were dispersed in a PET (poly(ethylene terephthalate)) matrix using a displacement procedure in which kaolin was initially treated with potassium acetate and, subsequently, melt-blended with PEO and PET. The disappearance of characteristic peaks in XRD patterns of chemically treated particles revealed that the crystalline form and layered structure of kaolin particles were mainly destroyed. Scanning electron microscopy and transmission electron microscopy showed that the thickness of dispersed particles were generally in the range of 10–100 nm. It was also observed that the dispersion level of the chemically treated kaolin was much better than that of “as received” kaolin particles. Rheological studies showed the formation of a network-like structure in samples containing the chemically treated kaolin as a result of improved dispersion of particles. It was also observed that both the kaolin particles and modifiers could accelerate the degradation process and lower the molecular weight of the PET. The introduction of kaolin particles shifted the crystallization temperatures of PET to higher temperatures. It was observed that the incorporation of a chain extender significantly restricted the crystallization process. The Avrami–Jeziorny analysis confirmed the alteration of the crystalline structure of the filled polymer. Based on TGA thermograms the decomposition temperature of PET–kaolin composites was slightly lower than that of the neat PET. POLYM. COMPOS., 2014. © 2014 Society of Plastics Engineers
    Polymer Composites 11/2014; DOI:10.1002/pc.23313 · 1.46 Impact Factor
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    ABSTRACT: Aligned electrospun poly(ethylene terephthalate) (ePET) nanofiber mats have been fabricated, which mimic the media layer of arteries. We used three different plasma etching techniques to bring their mechanical and surface properties in line with those of natural blood vessels: (i) atmospheric pressure (“HP”) corona discharge in air; (ii) low-pressure radio-frequency plasma (“LP”) and (iii) microwave plasma asher, (ii) and (iii) in pure oxygen (O2), or O2 mixture with Ar or CF4. (iii) gave substantial reduction in Young's modulus after as little as 5 min. treatment in O2, without damage to the fibers. Changes in surface composition and drastic improvement in wettability/wicking were also observed, which resulted in promoting adhesion and growth of smooth muscle cells (SMCs).
    Plasma Processes and Polymers 11/2014; 12(4). DOI:10.1002/ppap.201400147 · 2.96 Impact Factor
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    ABSTRACT: In this study, rheological, crystal structure, barrier, and mechanical properties of polyamide 6 (PA6), poly(m-xylene adipamide) (MXD6) and their in situ polymerized nanocomposites with 4 wt % clay were studied. The extent of intercalation and exfoliation as well as type of crystals, crystallinity, and thermal transitions were investigated using X-ray diffraction (XRD) and differential scanning calorimetry (DSC), respectively. Dynamic rheological measurements revealed that incorporation of nanoclay significantly increases complex viscosity of MXD6 nanocomposites at low frequencies, which was related to the formation of a nanoclay network and exchange reaction between MXD6 chains. The comparative study of dynamic characteristics (G′ (ω) and G″ (ω)) for aliphatic and aromatic polyamide nanocomposites with their neat resins as well as the relaxation spectra for both polymer systems confirmed the possibility of the aforementioned phenomena. Although, the crystallinity of MXD6 films was lower as compared to PA6 films, the permeability to oxygen was more than 5 times better for the former. Incorporating 4 wt% clay enhanced the barrier property, tensile modulus, and yield stress of PA6 and MXD6 nanocomposite films in both machine and transverse directions without sacrificing much puncture and tear resistances. The PA6-based films showed higher tear and puncture strength as compared to MXD6 films. POLYM. ENG. SCI., 2013. © 2013 Society of Plastics Engineers
    Polymer Engineering and Science 11/2014; 54(11). DOI:10.1002/pen.23813 · 1.44 Impact Factor
  • Ali Moayeri · Abdellah Ajji
    AIChE 2014 Annual Meeting, Atlanta, GA, USA; 10/2014
  • Ali Moayeri · Abdellah Ajji
    AIChE 2014 Annual Meeting, Atlanta, GA, USA; 10/2014
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    ABSTRACT: We analyze the pore structure changes during the fabrication of polypropylene-based microporous membranes via the stretching method. The membranes were prepared via melt extrusion followed by annealing and stretching at room temperature and at an elevated temperature (cold and hot stretching steps, respectively). Understanding the pore formation mechanisms is important for effective control of the membrane performance. Hence, the pore structure along the membrane surface and across the thickness, which determined the size, number, and interconnectivity of the pores, was analyzed to quantify the effect of stretching on the membrane performance. The cold stretching step was found to be the important one for promoting interconnection between the pores. Furthermore, it was shown that applying a low strain rate improved the permeability of the membranes. Finally, no maximum was observed in the permeability by increasing the stretch ratio during the hot stretching step.
    Industrial & Engineering Chemistry Research 09/2014; 53(36):14014-14021. DOI:10.1021/ie502300j · 2.59 Impact Factor
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    ABSTRACT: Oleic acid (OA)-capped cadmium selenide (CdSe) nanocrystals (NCs) have been synthesized via a new high-scale route. X-ray diffraction and transmission electron microscopy confirmed that rod-like hexagonal (wurtzite) CdSe NCs with an average size of 10 nm were obtained via this new route. The obtained CdSe NCs were treated individually with pyridine and tert-butylamine (t-BA) for ligand exchange. Fourier transform infrared spectra of the as-synthesized and treated CdSe NCs confirmed the removal of OA ligands from the surface of CdSe NCs after treatments with pyridine and t-BA. Bulk-heterojunction (BHJ) solar cell devices were prepared using untreated and surface treated CdSe NCs blended with poly (3-hexylthiophene-2,5-diyl) (P3HT) polymer. BHJ solar cell devices made from P3HT:(surface treated CdSe NCs) blends showed greater improvement in photovoltaic performances compared to P3HT:(untreated CdSe NCs) blend. The improvement in photovoltaic performances was due to the increase of electron mobility in P3HT:(CdSe NCs) blends after surface treatment of CdSe NCs.
    Journal of Materials Science Materials in Electronics 09/2014; 25(9):4051-4057. DOI:10.1007/s10854-014-2128-3 · 1.97 Impact Factor

Publication Stats

2k Citations
370.44 Total Impact Points

Institutions

  • 2009–2015
    • Polytechnique Montréal
      • Department of Chemical Engineering
      Montréal, Quebec, Canada
  • 2014
    • Université de Montréal
      Montréal, Quebec, Canada
    • Centre for Polymer Research
      Ciudad de México, Mexico City, Mexico
  • 1994–2011
    • National Research Council Canada
      • Industrial Materials Institute (IMI)
      Ottawa, Ontario, Canada
  • 1988–1995
    • Laval University
      • Department of Chemical Engineering
      Quebec City, Quebec, Canada
  • 1991–1994
    • Université du Québec
      Québec, Quebec, Canada