Search

Nonwoven fibrous mats of poly(ethylene-co-vinyl alcohol) (EVOH) and thermoplastic starch (TPS) blends were successfully prepared through the electrospinning technique using a mixed solvent system of isopropyl alcohol and water. The influence of TPS on the morphology and structure of the fibrous mats was investigated using scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy. The addition of TPS to EVOH resulted in beaded electrospun fibers. The SEM images revealed decreasing average width of the blend fibers and increasing quantity of beads with an increased TPS content. EVOH/TPS fibers mats irradiated under ultraviolet light using sodium benzoate as a photosensitizer were also prepared. The size and number of beads were diminished in the photocrosslinked EVOH/TPS fiber mats. The as-spun and crosslinked EVOH/TPS fiber mats exhibit a superior fluid uptake ability (with 20 wt% of TPS) and superior barrier properties (with 20 and 40 wt% of TPS) in comparison to those observed in neat electrospun EVOH mats. These properties are of particular interest for use in dressing materials for the medical industry and for use in multilayer plastic fuel tanks for the automotive industry, respectively., INTRODUCTION Ethylene-vinyl alcohol (EVOH) copolymers are a family of semicrystalline random copolymers that are easy to process and present both hydrophilic and hydrophobic characteristics due to the presence of alcohol [...]

The influence of surface modification and some processing parameters on the palygorskite (Pal) dispersion and the mechanical, thermal and rheological properties of the resulting Nylon 6 nanocomposites was investigated. Natural Pal was surface modified with hexadecyl tributyl phosphonium and 3‐aminopropyl trimethoxysilane to produce organoclays with different surface energy values. Nylon 6/Pal nanocomposites were produced by twin screw extrusion and then injection molded, Pal loading was 2 wt. % in all the cases. A screw configuration was designed to impose different level of shear stresses to the nanocomposites during processing, and nanocomposites were extruded at two different screw speeds. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) observations indicated that Pal was dispersed differently depending mainly on the degree of shear stress and surface modification of Pal. The best tensile mechanical properties were achieved with Pal exhibiting the lowest surface energy value dispersed with the screw having high shear configuration. The fatigue life of nylon 6 improved with addition of Pal. The experimental results give some guidelines for producing Nylon 6/Pal nanocomposites with improved properties. [ABSTRACT FROM AUTHOR]

PVC/Poly(ζ-caprolactone) (PCL)/organophilic-montmo-rillonite (OMMT) and PVC/Polylactide (PLA)/OMMT nanocomposites were prepared by a two-step process. PCL/OMMT and PLA/OMMT master batches were prepared by melt blending using a two-roller mill first, and then they were blended with PVC via extrusion. PVC/OMMT nanocomposites were also prepared using a two-roller mill. Morphology, mechanical properties, and thermal stability were investigated. The formation of exfoliated or intercalated nanocomposites was confirmed by X-ray diffraction (XRD) and transmission electron microscopy (TEM). Only the PVC/PCL/OMMT nanocomposite showed both higher tensile strength and stiffness than unfilled PVC. Atomic force microscopy (AFM) indicated dependency of this behavior not only on the clay dispersion, but also on the adhesion between the OMMT and the polymer matrix. Furthermore, scanning electron microscopy (SEM) showed that the large plastic deformation of the PVC/PCL matrix also contributed to the strength increase of the PVC nanocomposites. The effect of PCL/OMMT on the improvement of the thermal stability of PVC was remarkable while the effect of PLA/OMMT was moderate. POLYM. ENG. SCI., 51:641-646, 2011. [C] 2010 Society of Plastics Engineers, INTRODUCTION Rigid poly (vinyl chloride) (PVC), is one of the most economically and technically important thermoplastic polymers. Within recent years, rigid nano-dimensional particles have been used not only to toughen [...]

The effect of different carbon structures on the properties of low density polyethylene film and linear low density polyethylene blends (LDPE/LLDPE) subjected to artificial weathering, was studied. The carbon structures used were carbon black (CB), multi wall carbon nanotubes (MWCNT) and Graphene nanoparticles (GNP), at various loadings: 0.05, 0.1, 0.3, 0.5, 1.0, and 2 wt%. The PE‐Carbon structure composite films were characterized by optical microscopy (MOP), Haze, visible light transmission, UV–visible, thermogravimetric analysis (TGA), melt flow determinations (MFI) and tensile properties. Weathering measurements were evaluated in a QUV panel chamber with UV fluorescent lamps. The films degradation was analyzed following the change in carbonyl index of FTIR spectra, mechanical properties, and molecular weight. A noticeable better dispersion of CB and CNT particles in polyethylene matrix was observed compared with GNP. MWCNTs and CB produced high Haze and low visible light transmission. Thermal stability measured by TGA increased with the presence of GNP and CB. The crystallinity, melting, and crystallinity temperature (Tm and Tc) of the polymers increased with MWCNT and GNP. All the films with carbon structures presented an increase in the modulus of elasticity, with CB giving the highest elastic modulus. Artificial weathering of films with carbon structures showed that CB particles and CNT provided the highest UV protection to polyethylene, with a noticeable increase in low molecular weights and a retention in tensile strength and elongation at break which was reflected in maintaining their flexibility. Films with CNT showed the least significant changes in their properties, being more resistant to photo‐degradation. [ABSTRACT FROM AUTHOR]

Silicon nanocomposites were prepared with unmodified and modified magnetite nanoparticles in order to study the effect of the fatty acid modification on the curing reaction and thereafter on the mechanical and magnetic properties of the filled silicon‐based elastomer. Magnetite nanoparticles were first surface modified with oleic and stearic acid. Silicon nanocomposites with unmodified and modified magnetite nanoparticles were prepared by predispersing the nanoparticles in the silicone with the curing agent using toluene and ultrasound assisted mixing. The effect of the magnetite on the crosslinking reaction was studied in a rubber process analyzer instrument. At first, the addition of 1 wt% of magnetite decreased the induction time and increased the maximum torque, but upon increasing the magnetite content, this time increased and the maximum torque decreased. However, all the nanocomposites showed an induction time much lower than that of the pure silicon and a maximum torque much higher than that of the pure silicon. Unmodified magnetite nanocomposites showed a heterogeneous saturation magnetization when magnetite nanoparticles were modified with oleic and stearic acid. This resulted in homogeneous and replicable properties, attributed to the improvement in nanoparticles dispersion and distribution within the polymer matrix. The high saturation magnetization values of composites with unmodified magnetite compared with those with modified magnetite confirm that modified magnetite presented the best dispersion and more homogeneous magnetic properties. The Fourier‐transform infrared spectroscopy analysis suggests that the magnetite nanoparticles coating could be reacting with the silicon hydrosilane group which in turn decreases the attainable crosslinking level. With respect to the tensile properties, the tensile stress, as well as the elongation at the breakpoint decrease, in general, with increasing the magnetite content. POLYM. COMPOS., 40:3981–3988, 2019. © 2019 Society of Plastics Engineers [ABSTRACT FROM AUTHOR]

Maleic anhydride-grafted polypropylene (PP-g-MA) was reacted with aniline (NH2C6H5) to produce PP-g-NHC6H5 and used as a compatibilizer in polypropylene/carbon nanotube composites. Infrared spectroscopy (FTIR) and nuclear magnetic resonance confirmed the reaction between PP-g-MA and aniline. PP-g-NHC6H5 resulted a better compatibilizer than PP-g-MA, producing good dispersion and homogeneous distribution of the carbon nanotubes with less agglomerates, as observed by SEM analysis. Improved dispersion and distribution is assumed to be due to the π-π interactions between the -C6H5 ring in the prepared compatibilizer and the hexagonal carbon structure in the nanotubes. In addition, a higher degree of crystallinity (12%) was promoted, since it was favored by π-π interactions. This achieved higher crystallinity promoted an increase in tensile modulus, with only slight changes in tensile strength but with an adverse effect on elongation at break. [ABSTRACT FROM AUTHOR]

The mechanical properties of polypropylene-bentonite nanocomposites were studied in this work. In this study, stearic acid was used as both a new surface modifier of the nano bentonite and a new interface modifier during the compounding of the nanocomposites with a twin-screw extruder. Three different weight concentrations (1.5 wt.%, 2.5 wt.%, and 5.0 wt.%.) were chosen for each type of nanobentonite compounds. Fourier transform infrared spectroscopy allowed us the possibility to discard any chemical interaction between the nanobentonite and stearic acid. Nevertheless, the physical interactions between both components favored the mechanical properties, resulting in around 150% improvement in the elongation of the nanocomposites containing stearic acid as surface and interface modifier. This can be due to the good intercalation of the nanobentonite platelets as found by wide angle X-ray diffraction and this was further confirmed by scanning electron microscopy, where the fracture surface analyses of these nanocomposites showed the best dispersion and wetting of the nanoplatelets by the polymer matrix. Crystallization behavior was also modified by stearic acid incorporation and the nanocomposites with better dispersion exhibited crystallization temperatures similar to pure polypropylene. [ABSTRACT FROM AUTHOR]

A study of the improvement of the mechanical and thermal properties of nanocomposites prepared with polypropylene (PP) and different graphene samples [graphene oxide (GO), reduced GO (RGO), and commercial graphene (G)] is presented. X‐ray diffraction (XRD) and X‐ray photoelectron spectroscopy characterization were applied to the graphene samples. The nanocomposites were characterized by thermogravimetric analysis, XRD, differential scanning calorimetry, transmission electron microscopy (TEM), tensile, and impact resistance tests. PP/RGO nanocomposites showed significant improvement in mechanical and thermal properties. Sample PP/RGO‐0.75 resulted in an increment in Young's modulus (51%), tensile strength (24%), and elongation at break (15%). This is attributed to a good dispersion state, a higher crystallinity percentage, and a good interfacial adhesion between PP and RGO. Sample PP/RGO‐0.50 exhibited an increase of 197 °C in the temperature at which a loss in weight of 5% occurred, compared to that for pure PP. The height of stacked layers calculated by XRD measurements was similar to the value observed by TEM. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020, 137, 48258. [ABSTRACT FROM AUTHOR]