Urethane‐forming reaction kinetics and catalysis of model palm olein polyols: Quantified impact of primary and secondary hydroxyls

Model palm olein natural oil polyols (NOPs) with varying ratios of primary to secondary hydroxyls were synthesized, characterized, and evaluated in reaction kinetics study with isocyanate in formation of polyurethanes. Reaction rate constants and activation energies associated with primary and secondary hydroxyls of NOPs were quantified. The kinetic study in toluene shows that the NOP containing primary hydroxyls have three times higher reaction rate constants in noncatalyzed reaction with 4,4′‐diphenylmethane diisocyanate (4,4′‐MDI) compared to the model NOP containing only secondary hydroxyls, which is associated with higher activation energy of secondary hydroxyls. However, the difference in reaction rate constants of primary and secondary hydroxyls in NOPs diminished in the reactions catalyzed with dibutyltin dilaurate. Bulk polymerization reaction confirms the kinetics results in toluene, showing that the model NOP containing primary hydroxyls reached gel time at a faster rate. Evaluation of elastomers from bulk polymerization shows low degree of phase separation of hard and soft segments for elastomers based on the model NOPs. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 42955.     

Polyurethane/poly(ethylene‐co‐ethyl acrylate) and functional carbon black‐based hybrids: Physical properties and shape memory behavior

A polyurethane (PU) was developed from poly(dimethylamine‐co‐epichlorohydrin‐co‐ethylenediamine) (PDMAE) and polyethylene glycol (PEG) as soft segment and 2,4‐toluene diisocyanate (TDI) incorporating as hard segment. Later PU was blended with poly(ethylene‐co‐ethyl acrylate) (PEEA). Poly(vinyl alcohol)‐functionalized carbon black (CB‐PVA) nanoparticles was used as filler. The structure, morphology, mechanical, crystallization, and shape memory behavior (heat and voltage) were investigated methodically. Due to physical interaction of the blend components, unique self‐assembled network morphology was observed. The interpenetrating network was responsible for 83% rise in tensile modulus and 46% increase in Young's modulus of PU/PEEA/CB‐PVA 1 hybrid compared with neat PU/PEEA bend. Electrical conductivity was increased to 0.2 Scm^?1 with 1 wt % CB‐PVA nanofiller. The original shape of sample was almost 94% recovered using heat induced shape memory effect while 97% recovery was observed in an electric field of 40 V. Electroactive shape memory results were found better than heat stimulation effect. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43481.     

A Study on the Impact of the Adhesion of Penicillium expansum on the Physicochemical Surface Properties of Cedar Wood

The sessile drop technique was used to investigate the evolution of the physicochemical properties of cedar wood as a function of contact time with the Penicillium expansum spores. The most important finding showed that the impact of different contact periods (2, 4, 6, 8, 10, and 24 hr) on the wood surface were very indicative. In fact, after 2 hr of contact, the results have shown a significant impact of the bioadhesion of spores to the substrate on both the hydrophobic character (θ_W = 108.5°; ΔGiwi = ?28.25 mJ/m²), the electron donor (γ^? = 13.63 mJ/m²), and the electron acceptor (γ⁺ = 4.35 mJ/m²) parameters that were significantly reduced compared to the initial wood (θ_W = 118.5°; ΔGiwi = ?6.29 mJ/m²; γ^? = 32.1 mJ/m²; and γ⁺ = 9.1 mJ/m²). In addition, this decrease of parameters continued over time to stabilize after 10 hr of contact. Indeed, after 24 hr, the acid/base properties were almost zero and the contact angle with water decreased to 30°. Moreover, it was found that the coefficient of correlation (r²) was strong between the contact angle with water, the surface energy, and the electron acceptor character with the contact time parameter with values (r² = 0.65), (r² = 0.79), and (r² = 0.68), respectively.     

Low temperature synthesis of <Emphasis Type="Italic">Manganese tungstate</Emphasis> nanoflowers with antibacterial potential: Future material for water purification

Pure water is the fundamental requisite for human life. The water has been recycled naturally but not in an adequate amount for consumption. Nanotechnology with extraordinary applications provides competent ways for the decontamination of contaminated water. In the present study MnWO₄ nanoflowers endorsed with inherent antibacterial activity were successfully synthesized by facile hydrothermal approach. XRD, SEM, EDX spectroscopy and UVDRS were used to characterize the as-synthesized nanoflowers. Gram negative Escherichia coli ATCC 52922 bacterium was used as model organism to test antibacterial activity of as-synthesized MnWO₄ nanoflowers. This study was conducted to optimize minimum concentration of MnWO₄ nanoflowers and maximum contact time required to achieve complete inactivation of bacteria present in contaminated water. Minimum inhibitory concentration (MIC) of MnWO₄ nanoflowers was found to be 10 μg/ml. The assessment and interpretation of bacterial viability was done using dual fluorescent staining. The synthesized 3D-nanoflowers were found as potent bactericides. Thus, MnWO₄ nanoflowers emerged to be very good future material for disinfection of biological pollutants present in the contaminated water reservoirs and as an anti-biofouling agent.     

Polyolefin elastomer grafted unsaturated hindered phenol esters: synthesis and antioxidant behavior

Monomeric antioxidants are synthesized from esterification of 3,5-di-tert-butyl-4-hydroxybenzoic acid and 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid with unsaturated fatty alcohols. The antioxidant activity is evaluated both in blending and radical grafting processes. The effect of chain length and phenolic group is investigated on efficiency of antioxidants. It is demonstrated that the esters of 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid exhibit significantly longer induction time. The results of radical grafting reaction shows synthesized antioxidants can be successfully grafted onto polymer chains and the phenolic moiety is functional after extraction process, while pure and commercially stabilized samples are degraded instantaneously. Also, different initiator systems are utilized to enhance the extent of grafting. Among MEK, DCP, and DHBP peroxides, DHBP can be more effective in increasing the antioxidant grafted onto polymer. In addition, possibility of rising in graft content is investigated in presence of redox initiator. Using this approach, polymer-bound antioxidant with prolonged thermal stability can be achieved.     

The effect of substrate surface integrity on the surface properties of TiCrN coating applied via the CAE-PVD method

This study aims to investigate how the predeposition machining processes such as magnetic grinding, turning machining, and wire electrical discharge machining can influence the surface properties including electrochemical and tribological behavior of TiCrN nanostructured coating applied on Mo40 steel substrate. A physical vapor deposition technique using cathodic arc evaporation was used to apply the coating. The crystallographic phases and the microstructure of the coating were studied by X-ray diffraction and scanning electron microscope, respectively. Rockwell-C, electrochemical impedance spectroscopy and potentiodynamic polarization, and pin-on-disk wear tests were employed to evaluate the adhesion strength, corrosion behavior, and tribological property of specimens, respectively. The electrochemical results after 24 h of exposure to 3.5 wt% NaCl solution showed that TiCrN coating pretreated with a turning process with polarization resistance of about 3525.32 Ω.cm² had the best corrosion resistance among all specimens. This was because of the improvement of the smoothness, surface quality, and adhesion after the turning process. On the other, the friction coefficient of the grounded sample is less than that of other ones. This is probably due to its higher adhesion strength and higher surface smoothness.     

Characterization and mechanical properties of exfoliated graphite nanoplatelets reinforced polyethylene terephthalate/polypropylene composites

Recently, graphene and its derivatives have been used to develop polymer composites with improved or multifunctional properties. Exfoliated graphite nanoplatelets (GNP) reinforced composite materials based on blend of polyethylene terephthalate (PET), and polypropylene (PP) compatibilized with styrene–ethylene–butylene–styrene‐g‐maleic anhydride is prepared by melt extrusion followed by injection molding. Characterization of the composites' microstructure and morphology was conducted using field emission scanning electron microscopy, transmission electron microscopy (TEM), X‐ray diffraction analysis (XRD), and Fourier transform infrared spectroscopy (FTIR). Tensile and impact strengths of test specimens were evaluated and the results showed maximum values at 3phr GNP in both the cases. Morphological studies showed that the GNPs were uniformly dispersed within the matrix. Results from XRD analysis showed uniformly dispersed GNPs, which may not have been substantially exfoliated. FTIR spectroscopy did not show any significant change in the peak positions to suggest definitive chemical interaction between GNP and the matrix. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40582.     

Synthesis of biocompatible and degradable microspheres based on 2‐hydroxyethyl methacrylate via microfluidic method

Monodisperse poly(2‐hydroxyethyl methacrylate), p‐HEMA, microspheres in size ranging from 16 to 340 (μm) were synthesized by in situ emulsion photopolymerization of HEMA monomer with polyethylene glycol diacrylate (p‐EGDA) by means of a three‐dimensional microfluidic flow‐focusing device. An aqueous solution of HEMA, p‐EGDA as chain extender and UV‐photoinitiator serving as dispersed phase formed microdroplets in a continuous oil phase mainly consisting of n‐heptane. A downward coaxial orifices design in the device led to confinement of the reaction admixtures thread to central axis of the microchannels. This design strategy could solve the wetting problem of dispersed phase with the microchannels leading to a successful production of monodisperse microspheres with size variation of less than 4%. The effects of concentration of p‐EGDA, surfactant, and flow rate ratios on microsphere size were examined. It was observed that increasing the concentration of p‐EGDA slightly increases the size whereas increasing the flow rate ratios of continuous to dispersed phase effectively decreases the size of microspheres. The rapid continuous synthesis of p‐HEMA based microspheres via the microfluidic route with reliable control over size, size distribution, and composition opens new doors for mass production of biocompatible and degradable polymeric microspheres for enormous biotechnological applications. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40925.