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Migani V.,University of Bergamo | Weiss H.,Lautex S.r.l. | Massafra M.R.,Stazione Sperimentale per la Seta | Merlo A.,University of Bergamo | And 2 more authors.
Applied Surface Science | Year: 2011

Poly-dimethylsiloxane (PDMS) polymers finishing of Polyamide-6,6 (PA66) fabrics involves ionic interactions between reactive groups on the PDMS polymers and the ones of the textile fabric. Such interactions could be strengthened by a pretreatment with a fixing agent to promote either ion-ion and H-bonding and ion-dipole forces. These forces could contribute towards the building of substantial PDMS-PA66 systems and the achieving of better adhesion properties to fabrics. Four different silicone polymers based on PDMS were applied on a synthetic tanning agent (syntan) finished Polyamide-6,6 fabric under acid conditions. Soxhlet extraction method and ATR FT-IR technique were used to investigate the application conditions. The finishing parameters such as pH and temperature together with fastness, mechanical and performance properties of the treated samples were studied and related to PDMS side chains effect on syntan functionalized Polyamide fabric. © 2010 Elsevier B.V. Source

Herrero Acero E.,Austrian Center of Industrial Biotechnology | Ribitsch D.,Austrian Center of Industrial Biotechnology | Steinkellner G.,Austrian Center of Industrial Biotechnology | Gruber K.,Austrian Center of Industrial Biotechnology | And 13 more authors.
Macromolecules | Year: 2011

In this study cutinases from Thermobifida cellulosilytica DSM44535 (Thc-Cut1 and Thc-Cut2) and Thermobifida fusca DSM44342 (Thf42-Cut1) hydrolyzing poly(ethylene terephthalate) (PET) were successfully cloned and expressed in E.coli BL21-Gold(DE3). Their ability to hydrolyze PET was compared with other enzymes hydrolyzing natural polyesters, including the PHA depolymerase (ePhaZmcl) from Pseudomonas fluorescens and two cutinases from T. fusca KW3. The three isolated Thermobifida cutinases are very similar (only a maximum of 18 amino acid differences) but yet had different kinetic parameters on soluble substrates. Their kcat and Km values on pNP-acetate were in the ranges 2.4-211.9 s-1 and 127-200 μM while on pNP-butyrate they showed kcat and Km values between 5.3 and 195.1 s-1 and between 1483 and 2133 μM. Thc-Cut1 released highest amounts of MHET and terephthalic acid from PET and bis(benzoyloxyethyl) terephthalate (3PET) with the highest concomitant increase in PET hydrophilicity as indicated by water contact angle (WCA) decreases. FTIR-ATR analysis revealed an increase in the crystallinity index A1340/A1410 upon enzyme treatment and an increase of the amount of carboxylic and hydroxylic was measured using derivatization with 2-(bromomethyl)naphthalene. Modeling the covalently bound tetrahedral intermediate consisting of cutinase and 3PET indicated that the active site His-209 is in the proximity of the O of the substrate thus allowing hydrolysis. On the other hand, the models indicated that regions of Thc-Cut1 and Thc-Cut2 which differed in electrostatic and in hydrophobic surface properties were able to reach/interact with PET which may explain their different hydrolysis efficiencies. © 2011 American Chemical Society. Source

Marelli B.,Polytechnic of Milan | Alessandrino A.,Polytechnic of Milan | Fare S.,Polytechnic of Milan | Freddi G.,Stazione Sperimentale per la Seta | And 2 more authors.
Acta Biomaterialia | Year: 2010

Processing silk fibroin (SF) by electrospinning offers a very attractive opportunity for producing three-dimensional nanofibrillar matrices in tubular form, which may be useful for a biomimetic approach to small calibre vessel regeneration. Bypass grafting of small calibre vessels, with a diameter less than 6 mm, is performed mainly using autografts, like the saphenous vein or internal mammary artery. At present no polymeric grafts made of SF are commercially available, mainly due to inadequate properties (low compliance and lack of endothelium cells). The aim of this work was to electrospin SF into tubular structures (Ø = 6 mm) for small calibre vessel grafting, characterize the morphological, chemico-physical and mechanical properties of the electrospun SF structures and to validate their potential to interact with cells. The morphological properties of electrospun SF nanofibres were investigated by scanning electron microscopy. Chemico-physical analyses revealed an increase in the crystallinity of the structure of SF nanofibres on methanol treatment. Mechanical tests, i.e. compliance and burst pressure measurements, of the electrospun SF tubes showed that the inner pressure to radial deformation ratio was linear for elongation up to 15% and pressure up to 400 mm Hg. The mean compliance value between 80 and 120 mm Hg was higher than the values reported for both Goretex® and Dacron® grafts and for bovine heterografts, but still slightly lower than those of saphenous and umbilical vein, which nowadays represent the gold standard for the replacement of small calibre arteries. The electrospun tubes resisted up to 575 ± 17 mm Hg, which is more than four times the upper physiological pressure of 120 mm Hg and more than twice the pathological upper pressures (range 180-220 mm Hg). The in vitro tests showed a good cytocompatibility of the electrospun SF tubes. Therefore, the electrospun SF tubes developed within this work represent a suitable candidate for small calibre blood vessel replacement. © 2010 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved. Source

Brancatelli G.,University of Bergamo | Colleoni C.,University of Bergamo | Massafra M.R.,Stazione Sperimentale per la Seta | Rosace G.,University of Bergamo
Polymer Degradation and Stability | Year: 2011

The aim of this work was to prepare hybrid organic-inorganic silica thin films to provide cotton fabrics with flame retardant properties and to investigate the films' influence on the thermal and burning behavior of the treated samples. The fabrics were modified with three different sols in order to study the effect of pure silica sol-gel precursor, γ- aminopropyltriethoxysilane (APTES), and that of the hybrid sols consisting of the APTES and the phosphorus compound diethylphosphite. Furthermore, in order to improve the cross-linking degree and the phosphorus-nitrogen synergistic effect on flame retardancy of the P-doped silica thin film the melamine-based resin was added in the third sol. To evaluate the chemical structure of the coating material, pure xerogels of the treatment solutions were applied to glass slides and tested by ATR FT-IR spectroscopy. The cotton fabrics were impregnated with the sols by a padding-squeezing process and then dried. Thermal behavior of the treated cotton samples was investigated by thermogravimetric/differential scanning calorimetry analysis (TGA-DTG/DSC) and compared to the untreated one. The flame retardancy was tested according to the ASTM D 1230 standard method. The results showed a substantial enhancement of char-forming properties and flame retardancy for the fabrics modified with the thin films. © 2011 Elsevier Ltd. All rights reserved. Source

Khan M.M.R.,University of Manitoba | Tsukada M.,Shinshu University | Gotoh Y.,Shinshu University | Morikawa H.,Shinshu University | And 2 more authors.
Bioresource Technology | Year: 2010

Silk fibers from Bombyx mori silkworm was degummed with different concentration of citric acid, and the physical properties and fine structure were investigated to elucidate the effects of citric acid treatment. The silk sericin removal percentage was almost 100% after degumming with 30% citric acid which resulted in a total weight loss of 25.4% in the silk fibers. The surface morphology of silk fiber degummed with citric acid was very smooth and fine, showed perfect degumming like traditional soap-alkali method. The tensile strength of silk fiber was increased after degumming with citric acid (507. MPa), where as the traditional soap-alkali method causes to decrease the strength about half of the control silk fiber (250. MPa). The molecular conformation estimated by Fourier transform infrared spectroscopy and the crystalline structure evaluated from X-ray diffraction curve stayed unchanged regardless of the degumming with citric acid and soap. The dye uptake percentage of silk fiber degummed with citric acid decreased slightly, about 4.2%. On the other hand, the dye uptake percentage of silk degummed with soap was higher which indicates the disordering of the molecular orientation of the laterally ordered structure, accompanied with the partial hydrolysis of silk fibroin molecules by the alkali action of soap. The thermal properties were greatly enhanced by soap and citric acid degumming agents. Dynamic mechanical thermal analysis showed silk degummed with citric acid is more stable in higher temperature than that of soap. With heating at above 300°C, the silk degummed with citric acid shows an increase in storage modulus and an onset of tan δ peaks at 325°C and the melt flow of the sample was inhibited. The degumming of silk fibers with citric acid is safe and the results obtained are quite promising as a basis for possible future industrial application. © 2010 Elsevier Ltd. Source

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