Sharif Digital Repository

Polyvinylidene fluoride magnetic nanocomposite films were prepared by solution casting using two types of magnetic nanoparticles: (a) magnetic nanoparticles synthesized by co-precipitation method using oleic acid as a coating agent and (b) Fe3O4 nanoparticles prepared by hydrolysis method without using a coating agent. Dynamic light scattering measurements showed mean diameters of 135 and 46 nm in co-precipitation and hydrolysis methods, respectively. Scanning electron microscopy showed that the magnetic nanoparticles were uniformly dispersed inside the polymer matrix. X-ray diffraction confirmed that Fe3O4 nanoparticles induced nucleation of β- crystalline phase in the matrix polymer. The... 

This study intends to replace polyethylene multi-layer films used in food packaging industry with single-layer polyethylene nanocomposites films. Nanocomposites of LDPE/LLDPE/ montmorillonite organoclay were prepared by melt compounding in a twin extruder and then film blown to prepare thin films. LLDPE-g-MA was used as compatibilizer to achieve better interaction between the blend and organoclay. Various compositions of organoclay and compatibilizer were prepared. The structure of nanocomposites was characterized by XRD and TEM. Permeability properties were measured using a permeability measuring set-up and aspect ratio of the particles was evaluated using permeability data. The results... 

The feasibility of using solid acrylonitrile-butadiene rubbers (NBR) with 19 and 33% w/w acrylonitrile to toughen diglycidyl ether of bisphenol A (DGEBA) epoxy resins has been investigated. Thermal analysis experiments revealed a two-phase morphology of these rubber-modified epoxies. However, the higher content of acrylonitrile in the rubber caused better compatibility between NBR and the epoxy resin. The rubber with 33% acrylonitrile was found to be an effective toughening agent for DGEBA epoxy resins. Fracture surface studies and also the high tensile strength of crosslinked high molecular weight NBR suggest that the toughening effect should arise from rubber bridging and tearing... 

PVDF/nanoclay nanocomposites were prepared via melt mixing method. The intercalated dispersion of the nanoclay in PVDF matrix was confirmed by XRD. According to FTIR, DSC and XRD results, the presence of nanoclay facilitated transition from α-to-β crystalline phase. Electron beam irradiation decreased the melting point of the nanocomposites. The decrease in melting point of the nanocomposites was about 11 C at 500 kGy. The crystallinity of nanocomposites increased at an irradiation dose of 100 kGy and decreased at higher irradiation doses. The extent of crosslinking of the nanocomposites increased significantly with irradiation up to 300 kGy. The nanoclay intensified the increase in yield... 

Poly (vinylidene fluoride) (PVDF) nanocomposites were prepared via melt, solution, and co-precipitation mixing methods using Cloisite 30B as organoclay. The results from X-ray diffraction patterns display intercalation or exfoliation of nanoclay depending on the nanocomposite preparation method. The solvent cast and co-precipitated samples showed exfoliation, while intercalation was observed in the nanocomposites prepared by melt mixing. Introducing organoclay induced formation of β-crystals in the PVDF nanocomposites as evidenced by XRD and FT-IR. FT-IR analysis indicated that the samples prepared by the co-precipitation method had a higher tendency for β phase formation, while the sample... 

A drug delivery system based on poly (vinyl alcohol) (PVA) hydrogels containing ibuprofen-loaded poly (lactic acid) (PLA) microspheres was developed to improve the release kinetics of this model drug. Gamma-irradiation and freeze-thawing were applied to prepare poly (vinyl alcohol) hydrogels. Properties and morphology of these composite hydrogels were investigated using FTIR, DSC, and SEM. In vitro release indicated that entrapment of the microspheres into the PVA hydrogels causes a reduction in both the release rate and the initial burst effect. PLA microspheres entrapped into the PVA hydrogels showed more suitable controlled release kinetics for drug delivery  

Compounding electron beam irradiated polytetrafluoroethylene (PTFE or Teflon) powder with silicone rubber produced silicone rubber/PTFE composites with desired physical properties. PTFE powder was exposed to electron beam irradiation at various doses and characterized by FTIR, DSC and contact angle measurements. Irradiation of PTFE with high energy electron beam induced chain scission reactions. Irradiated PTFE showed higher degree of crystallization and lower melting point with increasing absorbed dose. Number average molecular weight of irradiated PTFE was reduced significantly at higher absorbed doses. Formation of polar groups on the surface of irradiated PTFE powder was detected by FTIR... 

Poly (vinyl alcohol)/graphene oxide (PVA/GO) gamma irradiated nanocomposite films and hydrogels were prepared. In composite films, GO was initially irradiated by gamma ray in order to improve interactions between GO and PVA. The film containing 1 wt-% GO was very strong where tensile modulus and tensile yield strength were 45 and 115% higher than those of pure PVA. In the second set of experiments PVA/GO hydrogels were made by irradiating PVA/GO suspensions by gamma ray at various doses. It was an interesting finding that GO increased the gel portion of hydrogels through contribution of H-bonds between PVA and GO. The hydrogels prepared at 20 kGy had remarkable water swelling ratio that... 

Linear silicone rubber and polyethylene alloy produced from extrusion-injecting process will be present in separate phases. While samples are mixed with 1% dicumylperoxide, DCP, and injected in extruder, an alloy is almost formed. In addition, when the samples containing silicon rubber with vinyl group are mixed with polyethylene and passed in the vicinity of electron beam, a similar reaction occurs, as confirmed from FTIR spectrum. The water contact angles for the samples has been listed in the article. Furthermore, the crystallinity of samples produced via electron beam method is more than that obtained from peroxide method. On the other hand, the tensile strengths of produced samples via... 

Poly(lactic acid) (PLA)/poly(vinyl acetate-. co-vinyl alcohol) [P(VAc-. co-VA)] blends as new transparent film packaging materials were prepared at various blend compositions and different vinyl alcohol contents. The blends and pure PLA were irradiated by gamma rays to investigate the extent of changes in the packaging material during gamma ray sterilization process. The miscibility of the blends was dependent on the blend composition and vinyl alcohol content; gamma irradiation had little effect on the extent of miscibility. The glass transition temperature of pure PLA and PLA/P(VAc-. co-VA) miscible blends reduced after irradiation. On the other hand in PLA/P(VAc-. co-VA) immiscible... 

The oxygen-barrier properties of poly(lactic acid) (PLA)/poly(vinyl acetate-co-vinyl alcohol) [P(VAc-co-VA)] were investigated. P(VAc-co-VA)s with vinyl alcohol (VA) contents of 5, 10, and 15 mol % were prepared with the acid-catalyzed hydrolysis of poly(vinyl acetate). The obtained copolymers with various contents of VA were blended with PLA at 5/95, 10/90, and 15/85 compositions. Films of the blends were prepared by a solution-casting method with chloroform as the cosolvent. Although the blend with 5% VA in the copolymer appeared to be miscible, the blends with 10 and 15% VA content in the copolymer were immiscible, as verified by dynamic mechanical analysis. The oxygen-barrier properties... 

Phase morphology, state of compatibility and various properties of blends of polycarbonate (PC) with bottle-grade and fibre-grade polyethylene terephthalate (BPET and FPET, respectively) were investigated. It was found that these blends have two-phase separated morphology with partial miscibility. Scanning electron micrographs revealed separated domains of PC-rich and PET-rich zones. PC domains appear spherical increasing in size from 2 μm for PC20/FPET80 up to about 5 μm for PC60/FPET40 blend. Further increase in PC content up to 80% caused phase inversion in which FPET appears as finely dispersed domains in continuous PC matrix. Tg of PC-rich phase decreased from 153 deg;C for pure PC down... 

Blends of the thermoset poly(allyl diglycol carbonate) (PADC) with thermoplastic polymethacrylates have been prepared by dissolving polymethacrylates in allyl diglycol carbonate (ADC) monomer and subsequent polymerization of ADC. The polymethacrylates formed separate phases in the blends as shown by scanning electron micrographs. The dynamic mechanical data showed two distinct high-temperature peaks corresponding to the glass transition temperatures of the PADC and polymethacrylates. Fracture toughness tests showed a significant increase in the critical intensity factor kc of PADC by addition of only 10% (w/w) a ductile thermoplastic poly(ethyl methacrylate). Young's modulus at room... 

Porous scaffolds composed of gelatin/poly (vinyl alcohol), (Gel/PVA), were prepared using combination of freeze gelation and freeze drying methods. The effect of polymer concentration, gelatin/PVA ratio, and glutaraldehyde/gelatin ratio (GA/Gel) was investigated on morphology of pores, swelling ratio, biodegradation, and skin cell culture. At optimum preparation conditions the scaffolds had uniform pore size distributions showing high swelling ratio of 23.6. The scaffolds were of biodegradable nature and almost degraded in 28 days. Human dermal fibroblast cells (HDF) were cultured on the scaffolds and MTS assay was conducted to evaluate the influence of PVA on growth and proliferation of the... 

Porous scaffolds composed of gelatin/poly (vinyl alcohol), (Gel/PVA), were prepared using combination of freeze gelation and freeze drying methods. The effect of polymer concentration, gelatin/PVA ratio, and glutaraldehyde/gelatin ratio (GA/Gel) was investigated on morphology of pores, swelling ratio, biodegradation, and skin cell culture. At optimum preparation conditions the scaffolds had uniform pore size distributions showing high swelling ratio of 23.6. The scaffolds were of biodegradable nature and almost degraded in 28 days. Human dermal fibroblast cells (HDF) were cultured on the scaffolds and MTS assay was conducted to evaluate the influence of PVA on growth and proliferation of the... 

Nanocomposites of polypropylene (PP)/ethylene-propylene-diene rubber (EPDM) blend with montmorillonite-based organoclay were prepared in a solvent blending method. Solvent blending of PP and EPDM in a composition of 50:50 formed a two phase morphology in which EPDM appeared as dispersed phase with irregular shape. The size of dispersed phase reduced significantly to almost spherical domains by addition of the nanoclay. For better dispersion of nanoclay in the PP/EPDM blend, an antioxidant was used as compatibilizer. State of nanoclay dispersion was evaluated by X-ray diffraction (XRD), and also, by a novel method using permeability measurements data in a permeability model. The measured... 

The impact strength of poly(methyl methacrylate)/caibon (long) fibre composites for denture prosthesis applications was improved by fibre surface treatment. The carbon fibre surfaces were modified by Nd:YAG laser irradiation at 1064 nm wavelength. Laser light intensity was adjusted at 100 mj per pulse that only changed the fibre surface roughness and did not lead to fibre rupture, as verified by scanning electron microscopy. Increased surface roughness of the fibres improved the adhesion of poly(methyl methacrylate) to the fibre surface. Adhesion between the fibres and poly(methyl methacrylate) was evaluated by a tear-off method and by scanning electron microscopy. The results also suggest... 

The application of agricultural fibers for making particleboards has been studied in two types of composites: (i) type I particleboards were composites of wheat straw and rice husk fibers with polymeric methylene di-phenyl diisocyanate resin (pMDI) as a binder made by compression moulding; (ii) type II particleboards were composites of rice husk and polypropylene made by extrusion and injection moulding. In type I particleboards, the effects of varying the resin content and various combinations of wheat straw/rice husk fibers were investigated and characterised in terms of physical and mechanical properties of particle boards such as modulus of rupture, modulus of elasticity, compression... 

Surface-modified magnetite (Fe3O4) nanoparticles with an average size of 22 nm were prepared. The nanoparticles had a saturation magnetization of 50.7 emu g-1. Then magnetite and drug-loaded microspheres of poly (lactic acid)/poly (ethylene glycol) were prepared at various compositions. The microspheres were spherical in shape and had smooth surface. The diameter size of the microspheres ranged between about 0.2 and 4 μm. Doxorubicin hydrochloride for cancer treatment was the drug that loaded into the microspheres. The prepared microspheres were characterized by FTIR, XRD, VSM, SEM and drug-release measurements. It was found that the drug cumulative release percentage was proportional to... 

Nanocomposites of poly(ethylene terephthalate) and two different montmorillonite-based organoclays were prepared by a co-rotating twin screw extruder. Dispersion of nanoclays in the polymer matrix was examined by TEM and XRD. Nanocomposites with lower content of organoclay showed exfoliated morphology while by increasing the amount of organoclay the intercalated morphology was more prevalent. Both organoclays had a good intercalation with PET and were uniformly dispersed within the polymer. Oxygen permeability of thin films of nanocomposites showed that the nanocompo-sites had better oxygen barrier properties than the neat PET. Tensile and impact properties of the nanocomposites also were...