Effects of SiO2 and Al2O3 nanofillers on polyethylene properties

Polymers filled with inorganic nanoparticles have become interesting materials as dielectrics because of their improved mechanical and electrical properties compared with the unfilled polymers and with polymer microcomposites. These improvements are mainly due to the large surface area of nanoparticles and new polymer–nanofiller interface characteristics. In the present work, polyethylene nanocomposites with SiO₂ and Al₂O₃ nanoparticles were prepared by melt mixing. Mechanical and electrical properties of these composites were determined and morphological aspects were revealed by scanning electron microscopy, wide‐angle X‐ray diffraction, and atomic force microscopy. The effect of nanostructure and the importance of nanofiller dispersion were analyzed in connection with mechanical and electrical properties. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Preparation of metal‐containing protein fibers and their antimicrobial properties

Bombyx mori silk, Antheraea pernyi silk, and wool fibers were chemically modified by treatment with tannic acid (TA) or by acylation with ethylenediaminetetraacetic (EDTA) dianhydride. Kinetics of TA loading or acylation with EDTA‐dianhydride varied from fiber to fiber. B. mori silk and wool displayed the highest weight gains with TA and EDTA‐dianhydride, respectively. The uptake of different metal ions (Ag⁺, Cu²⁺, Co²⁺) by protein fibers, either untreated or chemically modified, was studied as a function of weight gain and pH of the aqueous metal solution. Below pH 7, absorption of metal ions by untreated and TA‐treated fibers was negligible. Acylation with EDTA‐dianhydride enabled protein fibers to absorb and bind significant amounts of metal ions in the acidic and neutral pH range. The levels of metal desorption at acidic pH depended on the fiber‐metal combination. Untreated protein fibers usually displayed the lowest stability of the metal complex. Metal complexes with protein fibers exhibited prominent antimicrobial activity against the plant pathogen Cornebacterium. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 638–644, 2003     

Chemical Modification of Terephthalate Polyesters by Reaction with Bis(hydroxyethyl ether) of Bisphenol A

Summary: Copolyesters of terephthalic acid with bis(hydroxyethyl ether) of bisphenol A (BHEEB) in different molar ratios have been synthesized by reactive blending from terephthalate polyesters and by melt polycondensation from the monomers. By this way, bisphenol A groups were inserted in the polyester chains with the aim to obtain polyesters with improved mechanical properties. The insertion of the BHEEB into the polyester backbone is quantitative and does not give rise to side reactions. These copolyesters can be obtained by the chemical recycling of commercial polymers; indeed BHEEB can be synthesized by chemical recycling of bisphenol A polycarbonate and may be incorporated in the polyester by reactive blending with recycled terephthalate polyesters. A new method for BHEEB synthesis by chemical recycling of PC is also presented.

Glass transition temperature (T_g) as function of BHEEB content for copolyesters prepared by reactive blending BHEEB with terephthalate polyesters.     

Synthesis and Evaluation of N‐Phenylpyrrolamides as DNA Gyrase B Inhibitors

ATP‐competitive inhibitors of DNA gyrase and topoisomerase IV are among the most interesting classes of antibacterial drugs that are unrepresented in the antibacterial pipeline. We developed 32 new N‐phenylpyrrolamides and evaluated them against DNA gyrase and topoisomerase IV from E. coli and Staphylococcus aureus. Antibacterial activities were studied against Gram‐positive and Gram‐negative bacterial strains. The most potent compound displayed an IC₅₀ of 47 nm against E. coli DNA gyrase, and a minimum inhibitory concentration (MIC) of 12.5 μm against the Gram‐positive Enterococcus faecalis. Some compounds displayed good antibacterial activities against an efflux‐pump‐deficient E. coli strain (MIC=6.25 μm ) and against wild‐type E. coli in the presence of efflux pump inhibitor PAβN (MIC=3.13 μm ). Here we describe new findings regarding the structure–activity relationships of N‐phenylpyrrolamide DNA gyrase B inhibitors and investigate the factors that are important for the antibacterial activity of this class of compounds.     

Relation between the molecular structure and the efficiency of superabsorbent polymers (SAP) as concrete admixture to mitigate autogenous shrinkage

Superabsorbent polymers (SAP) were studied as admixtures for mitigating the autogenous shrinkage of a high-strength concrete. The presence of Ca²⁺ ions in the alkaline solution modified the kinetics of the liquid uptake and release when compared to that in other saline solutions and distilled water. SAP with high density of anionic functional groups took up the cement pore solution quickly, but greatly released it subsequently. The cross-linking density had no pronounced influence on the behaviour of such SAP. SAP with lower density of anionic groups did not release the liquid over the time of experiment. All SAP counteracted autogenous shrinkage during the acceleration period of cement hydration. For the materials which released the absorbed pore solution no effect on autogenous shrinkage was found beyond the initial period. SAP materials which did not release the absorbed solution in the experiments with liquids continued the mitigation of autogenous shrinkage during the deceleration period. The internal curing had no negative effect on the compressive strength of the mortar.     

Binding of metal cations to chemically modified wool and antimicrobial properties of the wool–metal complexes

Wool was modified by treatment with tannic acid (TA) or by acylation with ethylenediaminetetraacetic (EDTA) dianhydride. Kinetics of modification with TA and acylation with EDTA–dianhydride was investigated as a function of the reaction time. Wool displayed a higher breaking load and lower elongation at break as the degree of acylation increased. The absorption of metal cations (Ag⁺, Cu²⁺) by untreated and chemically modified wool was studied as a function of the kind of modifying agent, weight gain, and pH of the metal solution. Absorption of Ag⁺ and Cu²⁺ at alkaline pH increased with increasing weight gain of both TA and EDTA–dianhydride. The absorption of metal cations by untreated and TA‐treated wool below pH 7 was negligible. Acylation with EDTA–dianhydride enabled wool to absorb and bind significant amounts of metal cations at acidic and neutral pHs. The wool–Ag complexes exhibited low levels of metal desorption at acidic pH, irrespective of chemical modification. Higher levels of metal desorption were shown by wool–Cu and wool–EDTA–Cu complexes. Wool–Ag complexes exhibited prominent antimicrobial activity against Cornebacterium and E. coli. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 3513–3519, 2001     

Synthesis and characterization of new oligomeric/polymeric antistatic additives for sheet molding composites

For various applications it is necessary to lower the specific surface resistivity of polymers in an electrostatically conductive area. To improve the antistatic properties of sheet molding composites (SMC) usually conductive inorganic additives, like carbon black, inorganic salts, metal powder, or CNTs, are mixed physically into the matrix. A newly developed concept for antistatic treatment is using oligomeric/polymeric additives, which are synthesized on the base of ingredients of the used polymeric matrix itself. The received additives are compatible with the matrix. Furthermore, the migration of the additives to the surface is prevented and in the case they exhibit double bonds they are able to be linked in the polymeric network permanently by covalent bonds. So unsaturated, polymer‐based antistatic additives with ionic units were developed for unsaturated polyester resin based SMC. The synthesis was realized by polymer analogous reactions and polycondensation reactions from monomer building blocks with ionic units. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44741.     

Optimization of Arabinoxylan Isolation from Rye Bran by Adapting Extraction Solvent and Use of Enzymes

Physicochemical and functional properties of arabinoxylans (AXs) can be significantly influenced by their isolation method. Finding balanced process conditions that allow optimal extraction yields while preserving AXs functionality is a challenge. The aim of this study was to determine the effect of different chemical solvents with neutral and alkaline pH on the intrinsic properties and extraction yield of AXs isolated from rye bran. Additionally, the application of xylanases and other cell wall degrading enzymes (Pentopan Mono BG, Deltazym XL‐VR, Viscoflow BG) to solubilize bound AXs was investigated. Results show that the use of Ca(OH)₂ for isolation was superior to water and Na₂CO₃, as it selectively solubilized AXs and delivered isolates with a purity of up to 43.92% AX and a moderate ferulic acid (FA) content (209.35 ± 16.79 mg FA/100 g AX). Application of xylanases was further able to duplicate these achieved AX yields (7.50 to 9.85g AX/100 g bran). Additionally, isolates displayed highest ferulic acid contents (445.18 to 616.71 mg FA/100 g AX) and lowest impurities in comparison to chemical extracted AXs. Rheological characterization of the isolates showed a pronounced shear thinning behavior which fitted well to the power‐law model (R² > 0.989). Differences in pseudoplasticity of the isolates suggested that structural and chemical properties might have been responsible for this behavior.