Enhanced mechanical and thermal properties of graphene nanoplatelets-reinforced polyamide11/poly(lactic acid) nanocomposites

The present paper aims to obtain a sustainable nanocomposite by using bio-based polyamide 11 and biodegradable poly (lactic acid) blend as matrix and graphene nanoplatelets (GNP) as nanofiller. GNP was incorporated in the PA11/PLA blend matrix in the ratio of 0.5-1-3-5-10 wt% through the twin-screw extruder. The crystallinity of PA11 in the blend, which was 12.9%, increased with the inclusion of GNP, and the highest crystallinity value was observed at 20% for the 1GNP sample. The crystallinity of PLA in the blend, which was 2.3%, increased to 4.6% with 5 wt% GNP addition. The inclusion of GNP to PA11/PLA improved the thermal degradation temperatures and increase the char residue. Also, increments were observed for storage modulus, loss modulus, and glass transition temperature of the matrix with the inclusion of GNP. The addition of GNP caused the tensile strength of the matrix to increase first and then decrease at higher amounts due to the agglomerations. 0.5–1 wt% GNP increased tensile strength by 10% and 5%, respectively. Increasing the amount of GNP to 10 wt% led to a sharp decrease in tensile strength by 24%. Overall, GNP is a suitable nanofiller to enhance the thermal and mechanical features of the PA11/PLA blend.     

Development of Degradable,pH‐Sensitive Star Vectors for Enhancing the Cytoplasmic Delivery of Nucleic Acids

The report describes the synthesis of degradable, pH‐sensitive, membrane‐destabilizing, star‐shaped polymers where copolymers of hydrophobic hexyl methacrylate (HMA) and 2‐(dimethylamino)ethyl methacrylate (DMAEMA) monomers are grafted from the secondary face of a beta‐cyclodextrin (β‐CD) core via acid‐labile hydrazone linkages using atom transfer radical polymerization. The effect of the graft's molecular weight, HMA/DMAEMA molar ratio, and the fraction of DMAEMA converted to cationic N,N,N‐trimethylaminoethyl methacrylate (TMAEMA) monomers on polymer's transfection capacity is systematically investigated. Results show that all star‐shaped polymers condense anti‐GAPDH silencing RNA (siRNA) into nanosized particles at +/‐ ratio ≤ 4:1. Star polymers with shorter (25kDa) P(HMA‐co‐DMAEMA‐co‐TMAEMA) grafts are more efficient and less cytotoxic than carriers with longer (40kDa) grafts. The results show that increasing the ratio of hydrophobic HMA monomers in graft's composition higher than 50 mole% dramatically reduces polymer's aqueous solubility and abolishes their transfection capacity. Further, retention of DMAEMA monomers in graft's composition provide a buffering capacity that enhanced the endosomal escape and transfection capacity of the polymers. These systematic studies show that β‐CD‐P(HMA‐co‐DMAEMA‐co‐TMAEMA)_4.8 polymer with a 25 kDa average graft's molecular weight and a 50/25/25 ratio of HMA/DMAEMA/TMAEMA monomers is the most efficient carrier in delivering the siRNA cargo into the cytoplasm of epithelial cancer cells.     

Reduced graphene oxide reinforced PET/PBT nanocomposites: Compatibilization and characterization

This research work focused on the effects of different compatibilizers on the properties of reduced graphene oxide (rGO) reinforced poly(ethylene terephthalate) (PET)/poly(butylene terephthalate) (PBT) nanocomposites. The samples were prepared via melt compounding and injection molding methods. The Joncryl and glycidyl isooctyl polyhedral oligomeric silsesquioxane (GPOSS) were used as compatibilizers at different loading levels (0.5%-4%). The structural, thermal, mechanical, morphological, and electrical properties of the nanocomposites were investigated. The Fourier transform infrared analysis results revealed that no significant interaction was observed when GPOSS was added. On the other hand, there were more obvious changes in the peaks of the nanocomposite containing Joncryl. The thermal results showed that the compatibilizer addition caused small changes while rGO addition did not considerably affect the thermal stability of blend. The glass transition temperature of the nanocomposite significantly decreased with the addition of GPOSS. The tensile test indicated that compatibilizers improved the mechanical performance of PET/PBT/rGO nanocomposite.     

C18 Unsaturated Fatty Acid Selectivity of Lipases During the Acidolysis Reaction Between Tripalmitin and Oleic,Linoleic, and Linolenic Acids

The C18 unsaturated fatty acid (UFA) selectivity of three immobilized lipases, namely, Lipozyme TL IM from Thermomyces lanuginosa, Lipozyme RM IM from Rhizomucor miehei, and Novozym 435 from Candida antarctica, was determined in acidolysis conducted in hexane. Tripalmitin with a mixture of equimolar quantities of C18 UFAs was used as the substrate. Significantly different incorporation rates were observed for C18 UFAs used (p < 0.05). The highest incorporation was obtained for all three C18 UFAs with Novozym 435 followed by Lipozyme RM IM and Lipozyme TL IM catalyzed acidolysis under default conditions (substrate mole ratio 1:1; temperature 50 °C; reaction time 6 h; enzyme dosage 10%). Incorporation of the equimolar quantities of C18 UFAs was in the order C18:3 > C18:2 > C18:1 which also reflects C18 UFAs preferences of the lipases. The effects of operating variables on incorporation or UFA selectivity of lipases were also investigated. Among the experimental parameters including the mole ratio of fatty acid to triolein, temperature, enzyme dosage, and time on incorporation, the effect of the substrate mole ratio on UFA selectivity was greater than those of the others.     

Operational Conditions of Activated Sludge: Influence on Flocculation and Dewaterability

Selected operational conditions of activated sludge are investigated in relation to their effect on flocculation and dewatering. Semi-continuous reactors with 2 -L volume were operated at different mean cell residence times, C/N ratios, and three different influent cations. Results show that MCRT, C/N ratio, and the cation type affect the bioflocculation capacity of activated sludge measured by the quantity of extracellular polymeric substances. As the MCRT value operated in the reactors and the C/N ratio of the influent wastewater increase, total amount of polymers produced increases. High MCRT values and low C/N values cause good dewatering of the sludge. All cations are shown to stimulate the EPS production in a way that the highest total EPS concentrations are observed at the highest cation dosages. The dewaterability of the sludges improves only with increasing calcium and magnesium concentrations and deteriorates with increasing potassium concentration.     

Synthesis of block copolymers by combination of ATRP and photoiniferter processes

BACKGROUND: Block copolymers of monomers polymerizing by different mechanisms can be prepared by the transformation approach. A wide range of combinations of different polymerization modes has been reported in the literature. In this work, the transformation approach was further extended to the preparation of block copolymers by combining atom transfer radical polymerization (ATRP) and photoiniferter processes. RESULTS: Photoactive morpholine‐4‐dithiocarbamate‐terminated polystyrene (MDC‐PS‐MDC) was prepared by the reaction of dibrominated polystyrene, obtained by ATRP, with morpholine‐4‐dithiocarbamate sodium salt in dimethylformamide. The structure of MDC‐PS‐MDC was confirmed by ¹H NMR and UV‐visible spectral analysis. The ability of MDC‐PS‐MDC to act as a photoiniferter for the block copolymerization of methyl acrylate was examined. The polymerization shows a ‘living’ character at up to 25% conversion and produces well‐defined polymers with molecular weights close to those predicted from theory and relatively narrow polydispersities (M_w/M_n ≈ 1.40). CONCLUSION: It is demonstrated that the end groups of polymers obtained by ATRP can be converted into morpholino‐4‐dithiocarbamate groups which act as photoiniferters. In this way, the desired mechanistic transformation between two controlled free radical polymerization methods can be achieved. Copyright © 2008 Society of Chemical Industry     

Determination of 5-hydroxymethyl-2-furfural and 2-furfural in oils as indicators of heat pre-treatment

This study describes a method for the determination of 5-hydroxymethyl-2-furfural (HMF) and 2-furfural (F) in oils. The method entails liquid–liquid extraction and reversed-phase liquid chromatography. Spiked hazelnut oil was used to test the accuracy and reliability of the method. Furan compounds were extracted from oil using 70% methanol. Mean recoveries were 97 ± 2% and 99 ± 1% for HMF and F, respectively. To investigate the presence of HMF and F in oils, seven oily nuts and seeds were roasted at 180 °C for 30 min. Different oils were found to contain HMF and F ranging from 0.8 to 13.8 and 1.4 to 8.7 mg/kg, respectively. Increasing solvent polarity also increased the rate of HMF transferred to the oil. Spectral analyses of the 70% methanol extracts indicated that absorbance at 285 nm may be used to monitor the accumulation of furan compounds in oil phase during the roasting process of nuts.     

Determination of changes occurred in the microflora of cig kofte (raw meat balls) at different storage temperatures

The aim of this study was to investigate the effect of different storage temperatures on the microbiological characteristics and pH values of cig kofte during storage. Storage temperature affected significantly total aerobic mesophilic bacteria (TAMB), coliforms, yeasts and moulds, lactic acid bacteria (LAB) and Staphylococcus aureus counts of cig kofte which had lower counts in refrigerator storage than in room storage following sixth hour for TAMB (P < 0.001), coliform (P < 0.01, P < 0.001), S. aureus (P < 0.01, P < 0.001) and LAB (P < 0.001) and at the end of storage for yeasts and moulds (P < 0.001). Listeria and Salmonella spp. could not be detected at both refrigerator temperature and room temperature storage. In order to minimise the contamination level of cig kofte, use of best microbial quality minced meat and ingredients as well as good personnel hygiene is required and preserved. In addition, Cig kofte should be kept in refrigerator when leftovers remain for additional meals.