Sinan Şen

Polymer Nanocomposite Hydrogels with Improved Metal Adsorption Capacity and Swelling Behavior: Influence of Spirulina Immobilization onto Montmorillonite Clay

Polacrylamide nanocomposite hydrogels were prepared by in situ free radical polymerization reaction in presence of Spirulina microalgae, which is immobilized in montmorillonite clay (Sp-MMT). The nanocomposite hydrogel having 1 wt.% Sp-MMT clay was found to have desired exfoliated structure, maximum swelling and improved thermal stability. It also showed maximum metal adsorption capacity, which is about 312% higher than that of neat PAAm hydrogel at the highest metal concentration. The presence of Spirulinas porous network structure where all potential binding sites are under receptive position was found to be responsible for the dramatic increase in the metal adsorption and swelling behavior.

Biosorbent immobilized nanotube reinforced hydrogel carriers for heavy metal removal processes

Abstract A series of natural composite hydrogels containing a “3-in-1” type triple adsorbent system are designed. For this purpose, Spirulina (Sp) biosorbent is immobilized on/in halloysite nanotubes in different loadings and then physically crosslinked chitosan composite hydrogels are prepared. The water absorbency and Cr (VI) adsorption capacity in neutral pH medium and wet mechanical strength as well as their morphologies are all reported as a function of Sp immobilized nanotube loadings. The use of Sp biosorbent results in composite hydrogels with high water absorbency, wet strength and thermal stability. Spirulina enlarges the metal adsorption windows efficiently and the Freundlich isotherm model can fit the fundamental metal adsorption data well. It is believed that with optimized special composite hydrogel morphologies, all positively charged receptors of the Sp and the nanotubes behave as collector domains for chromate anions.

Tuning of heavy metal removal efficiency from water via micro algae/hydrogel composites

Abstract A series of micro algea-based hydrogel composites were prepared from polyacrylamide and Spirulina (PAAm-sp). Free radical polymerization of acrylamide (AAm) in the presence of N,N-methylene bis-acrylamide (BAAm), as a crosslinker, and Spirulina microalgae in different loadings was conducted. Chromium metal adsorption capacity was determined with UV-VIS spectroscopy whereas mechanical performance of the resultant hydrogel composites was followed with uniaxial compression experiments. It has been found that efficiency can be tuned by Spiriluna composition in hydrogel. PAAm hydrogel composite having 0.5 % Spirulina had the maximum compression strength, good swelling in water as well as improved thermal stability due to the special and beneficial ‘fishnet morphology” observed via scanning electron microscopy (SEM). The observed high performance of this composition is proved to be due to this morphology where all potential binding sites are under receptive position for metal adsorption. Spirulina by itself in water can remove only about 2 % of its weight of Cr+3 ion, however in the hydrogel structure this removal increases up to 200 % which makes this biotechnological approach superior in the metal removal from the water.

Swelling, viscosity and static‐mechanical behaviour of polyester composites based on hybrid filler system

Swelling and static-mechanical properties of fly ash/mica hybrid reinforced unsaturated polyester composites in cured state have been discussed with special reference to the effect of loading composition, nature of filler surfaces and surface treatment of fillers. Processing behaviour of the composites in uncured state was determined through the viscosity measurements. In terms of swelling behaviour of the composites, silanization of fly ash and mica surfaces causes a significant decrease in swelling compared to unsilanized counterparts. In cured state, addition of mica into fly ash polyester composition causes increase in tensile properties.

Synthesis and characterization of polyHIPE composites containing halloysite nanotubes

Abstract High internal phase emulsion templated-polymer (polyHIPE) composites were prepared from spirulina modified halloysite (HL) nanotube containing styrene/divinylbenzene based water-in-oil type concentrated emulsions. In order to obtain a stable emulsion for neat polyHIPE’s synthesis, at least 5 vol% Span-80 as a non-ionic surfactant, with respect to organic phase was needed. For syntheses of polyHIPE composite structures, this amount was decreased to 2 vol%, even in presence of 0.25 wt% modified nanotube with respect to the organic phase. All the polyHIPE composites exhibited open pore structures with pore interconnections together with partially or completely closed pores. The composite having 0.25 wt% modified nanotube and 2 vol% surfactant was found to have about 260% higher dye adsorption capacity and the highest onset degradation temperature in comparison with neat polyHIPE.

Cross-Linkable Epoxidized Maleinated Castor Oil: A Renewable Resin Alternative to Unsaturated Polyesters

As an alternative resin to conventional synthetic unsaturated polyesters (UPEs), epoxidized maleinated castor oil (EMACO) was synthesized in two steps. For this purpose, castor oil was reacted with maleic anhydride at 70°C to obtain maleinated castor oil (MACO). Then, epoxidation of MACO was carried out by using a mixture of formic acid and hydrogen peroxide at 0–5°C. Then, the free carboxyl groups of the synthesized EMACO were further reacted with free epoxide groups of EMACO at 90°C. At the end of the reaction, an unsaturated polyester precursor-prepolymer was obtained (P-EMACO). FTIR and 1H NMR spectroscopic techniques were used to characterize the monomers synthesized. The P-EMACO was then mixed with styrene and cross-linked in the presence of AIBN at 50°C. Thermal and mechanical properties of the final cross-linked product were investigated by thermogravimetric analysis (TGA) and dynamic mechanical analysis (DMA) techniques. The degradation onset temperature of the material at which cross-linked X-EMACO loses 5% of its weight was found to be 209°C. Its dynamic and storage modulus at 25°C were determined as 72°C and 1.08 GPa, respectively. These results are higher than some of the different oil based polymers reported in the literature.

Tuning of nanotube/elastomer ratio for high damping/tough and creep resistant polypropylene/SEBS-g-MA/HNT blend nanocomposites

Polypropylene (PP)/maleic anhydride grafted polystyrene-b-poly (ethylene/butylene)-b-polystyrene (SEBS-g-MA)/organophilic halloysite nanotube clay ternary nanocomposites were produced by using HNT/SEBS-g-MA masterbatches at different nanotube loadings (1 wt%, 3 wt%, and 5 wt%). The masterbatches with different ratios of HNT/SEBS-g-MA (1/1, 1/2, and 1/3) were prepared via a revolution/rotation type mixing-assisted masterbatch process. All nanocomposites showed higher storage moduli and damping at low temperatures as compared to neat polypropylene. The nanocomposites having HNT/SEBS-g-MA ratio of 1/3 were found to act as effective dampers with their relatively higher damping values. In terms of short-term creep performance, 1 wt% and 3 wt% organophilic halloysite nanotube loaded systems with low amount of SEBS-g-MA (<9 wt%) enhanced dimensional stability of polypropylene with their lower creep strain and permanent deformation values. More specifically, among the nanocomposites, 3 wt% organophilic halloysite nanotube loaded nanocomposite with HNT/SEBS-g-MA ratio of 1/3 and co-continuous like morphology not only exhibited an effective damping over a wide range of temperature (from −70℃ to 50℃) but also showed relatively higher storage moduli at low temperature region together with lower permanent creep deformation as compared to neat polypropylene. As a result, the HNT/SEBS-g-MA masterbatch in 1/3 ratio was found to be the most suitable in polypropylene blend nanocomposites. It may be advantageous for polypropylene nanocomposite based applications where high damping/toughness at low temperature conditions and high dimensional stability under load are desired.

Weld line behaviour of exfoliated and toughened polypropylene layered silica nanocomposites

Abstract Exfoliated and toughened polypropylene nanocomposites prepared by an introduction of a rubber in the form of compatibilizer toughener: ethylene propylene diene based rubber grafted with maleic anhydride (EPDM-g-MAH) were studied in terms of weld line properties and morphology. Effects of addition of rubber and nanolayer on weld line strength under tensile loading condition of polypropylene matrix were investigated. Data showed that in the absence of either EPDM or nanolayers, a sharp decrease in weld line strength cannot be avoided whereas in the presence of each in optimum ratio, the drastic increase in both toughness and weld line strength values can be easily reached. The beneficial effect is believed to come from the selective placing of nanolayers around the rubber droplets and making them smaller in size which contributes to diffused weld line regions with high mechanical strength.