Effect of layered silicate on EPDM/EVA blend nanocomposite: Dynamic mechanical,thermal, and swelling properties

Polymer blend nanocomposites have been developed by solution method using ethylene propylene diene terpolymer (EPDM), ethylene vinyl acetate (EVA‐45) copolymer, and organically modified layered silicate. Morphological investigation made by wide‐angle X‐ray diffraction and transmission electron microscopic analysis indicates intercalated structure of EPDM/EVA nanocomposites with partial disorder. Scanning electron microscopic studies exhibit the phase behavior of EPDM/EVA blend nanocomposites. Dynamic mechanical thermal analysis shows a significant increase in storage modulus in the rubbery plateau. The decrease in damping (tan δ) value and enhanced glass‐transition temperature (T_g) demonstrate the reinforcing effect of layered silicate in the EPDM/EVA blend matrix. The tensile modulus of these nanocomposites also showed a significant improvement with the filler content. The main chain scission of EPDM/EVA blend nanocomposites compared with the neat EPDM/EVA blend showed substantial improvement in thermal stability in nitrogen, whereas a sizeable increase is observed in air. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers     

Sorption and permeation of acetic acid–water mixtures by pervaporation using copolymer membrane

Poly (acrylonitrile‐co‐methyl acrylate) copolymer designated as PANMA was used for making pervaporation membrane. This membrane was used for separation of acetic acid–water mixtures over the concentration range of 80–99.5 wt% acetic acid in water. Interaction parameters based on Flory–Huggins lattice model and engaged species induced clustering (ENSIC) model was used to explain swelling of the membranes. Coupling in sorption was explained in terms of activity coefficient of water and acid in feed and membrane using Flory–Huggins model and also by interpolating ENSIC parameters. Flow coupling in pervaporation was also determined from phenomenological deviation coefficients. Intrinsic membrane properties like partial permeability and membrane selectivity of the solvents were also determined. Diffusion coefficient and plasticization coefficient of the solvents were obtained using a modified solution–diffusion model. The copolymer membrane showed high flux and water selectivity for highly concentrated acid. Thus, at 30°C temperature 1–20 wt% water in feed was concentrated to 82–84 wt% water in permeate and for 0.95 wt% water in feed, the membrane showed thickness normalized flux and water selectivity of 1.71 kg m^?2 h^?1 mμ and 409, respectively. OLYM. ENG. SCI., 2013. © 2012 Society of Plastics Engineers     

Poly(3‐dodecyl thiophene)—Organically modified montmorillonite clay nanocomposites: Influence of chain regioregularity and preparation condition on physical,mechanical, optical,and conductivity properties

The properties of regioregular(R) (98.5 mol % H‐T) and regioirregular(I) (80.5 mol % H‐T) poly(3‐dodecyl thiophene)(P3DDT)—organically modified montmorillonite (om‐MMT) clay nanocomposites obtained from solvent‐cast and melt‐cooled procedures are compared. The solvent‐cast P3DDTI nanocomposites showed partially exfoliated clay structure but P3DDTR nanocomposites showed multistack exfoliation. Type 1 crystalline polymorph was produced in solvent‐cast systems whereas melt‐cooled P3DDTI samples showed mesomorphic structure. Storage modulus of P3DDTI nanocomposites increased with clay concentration showing a maximum increase of 255%. The UV‐vis spectra showed blue shift of π–π* transition band and photoluminescence spectra indicated seven times increase of normalized intensity in solvent cast P3DDTI composites. DC conductivity and I–V characteristic curves showed increased insulating properties with om‐clay concentration. The physical, mechanical, and optical properties of P3DDTI nanocomposites are more improved than that of P3DDTR nanocomposites and from their pristine polymers. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Polyacrylic acid (poly-A) as a chelant and dispersant

Polyacrylic acid was synthesized in water by persulfate-initiated polymerization (solution polymerization) of glacial acrylic acid in the absence of a chain-transfer agent. The final product is odorless and colorless. Chelation for calcium ions using a calcium electrode show that our poly(acrylic acid) has a higher chelation capacity than that of existing commercial poly(acrylic acids). A design of experiments was performed to optimize the synthesis conditions to obtain poly(acrylic acid) with a high maximum chelation value. These studies also helped us to gain insight into its high chelation capacity. The chelation capacity for calcium reaches its highest values when polymerization near isothermal conditions is done ∼ 95°C with an acrylic acid concentration of ≤21 wt % and an addition time >1 h. These conditions favor higher molecular weight poly(acrylic acid) with a polydispersity ∼ 4. The dispersion properties of our poly(acrylic acid) are similar to those of the commercial ones. This dual capability of chelation and dispersion is absent in commercial chelants such as ethylenediaminetetraacetic acid (EDTA), diethylenetriaminepentaacetic acid (DTPA), and their analogs. At pH > 7, chelation of calcium by our poly(acrylic acid) is much higher than that observed with EDTA. Characterization by NMR, Raman, FTIR, and molecular modeling are included in an attempt to understand structural features that can explain the higher chelation capacity of our atactic poly(acrylic acid).     

Effects of corona treatment on surface properties of co-extruded transparent polyethylene film

Current study encompasses that the effect of corona treatment on the outer surface of transparent co-extruded polyethylene films was at various levels by applying different wattages, in tandem with the blown film extrusion process. A maximum treatment of 42 dynes/cm was achieved at 4.5 KW of applied wattage. The heat seal joint strength of the films sealed at different combinations of treated/untreated surfaces was evaluated and an untreated/untreated surface combination was found to exhibit maximum strength (2.8 kgf/25 mm), while a treated/treated surface combination showed the minimum (1.41 kgf/25 mm) under identical conditions of sealing and testing. The peel adhesion to ascertain the treatment level on the treated surfaces was inspected by a standard Scotch tape method, and the results exhibited a linear relationship between the applied wattage and the pulling force of adhesion. The Fourier transform infrared spectroscopy (FTIR) spectra of the treated and untreated film samples in an attenuated total reflection (ATR) mode showed the peaks' characteristics mostly of polyolefin films. The morphologies of the treated surfaces displayed relatively rough surface compared to the untreated one. The barrier properties of the treated films in respect of water vapor and oxygen transmission rate do not undergo any appreciable change.     

Interface engineering for the improvement of mechanical and thermal properties of covalent functionalized graphene/epoxy composites

Functionalized reduced graphene oxide (GO)/epoxy composites are fabricated through solution mixing. GO is functionalized using 3‐amino‐1,2,4‐triazole (TZ) in presence of potassium hydroxide (KOH). KOH is expected to serve dual role as catalyst for nucleophilic addition reaction between GO and TZ, and also as reducing agent. The grafting of TZ moiety on GO is confirmed by Fourier transform infrared spectroscopy, X‐ray diffraction, and thermogravimetric analysis. The prepared composites show remarkable improvement in mechanical and thermal stability. The fracture toughness of the composites (critical stress intensity factor, K_IC) achieved from single edge notched bending testing is improved by ～111% against pure epoxy at 0.1 wt % loading of TZ functionalized GO. Further, the tensile strength and Young's modulus are improved by ～30.5% and 35%, respectively. Thermal stability of the composites as investigated by thermogravimetric analysis showed 29 °C rise in onset degradation temperature for 0.1 wt % TZ functionalized GO incorporated composite. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46124.     

A novel scheduling with multi-criteria for high-performance computing systems: an improved genetic algorithm-based approach

Engineering with Computers - Scheduling in high-performance computing systems is experiencing potential challenges in modern computing applications due to different application sizes, computational...     

Preparation of functionalized graphene/linear low density polyethylene composites by a solution mixing method

The surface modification of graphene as well as the characterization of modified graphene-based polymer composite prepared by solution mixing techniques was examined. X-ray photoelectron spectroscopy was employed to examine the surface modification and formation of graphene. The tensile strength of the composite increased with 3 wt.% of DA-G loading and was 46% higher than that of neat LLDPE. The onset thermal degradation temperature of the composite (3 wt.% of DA-G) was increased by ∼40 °C compared to neat LLDPE. A sharp increase in electrical conductivity of the composite was observed at 3 wt.% of DA-G content.     

Efficient synthesis of graphene sheets using pyrrole as a reducing agent

The efficient synthesis of graphene sheets using pyrrole as a reducing agent was explored. The obtained graphene sheets were dispersible in organic solvents such as ethanol, isopropanol, N,N-dimethylformamide, N-methylpyrrolidone, dimethylsulfoxide, tetrahydrofuran, and acetone. During this reduction reaction, pyrrole was oxidized, forming oxidation product of pyrrole and adsorbed on the graphene sheets surface by π–π interaction. The oxidation product of pyrrole acted as a capping agent for graphene sheets by preventing re-stacking and formed organically dispersible graphene. The formation of graphene and its crystalline nature was indicated by the transmission electron microscopy and the atomic force microscopy analysis. Raman, X-ray photoelectron spectroscopy and X-ray diffraction provided the evidence for graphene formation from graphene oxide precursor. Furthermore, the reduced oxygen content and N 1s peak observed by the X-ray photoelectron spectroscopy analysis of graphene sheets confirmed the reduction reaction and presence of adsorbed oxidation product on the surface of graphene sheets. The resulting graphene sheets were readily dispersible in solvents and easily to process.