Crystallization of UV-irradiated β-nucleated polypropylene

International audienceThe work deals with crystallization of photodegraded polypropylene containing various amounts of β-nucleating agent. Samples were irradiated by UV-light, melted and subsequently non-isothermally crystallized. The results showed that the crystallization temperature decreased with increasing irradiation time. The irradiation caused the splitting of crystallization exotherms into two peaks indicating two crystallization mechanisms. The presence of β-nucleating agent in the material suppressed the peak splitting

TiO2 deposition on the surface of activated fluoropolymer substrate

Anatase-structured TiO2 films were deposited on a commercial fluorinated polymer (FEP) with a treated surface, by means of a sol-gel dip-coating technique. Two different curing temperatures were investigated and the film microstructures were characterized by X-ray diffraction, atomic force microscopy and scanning electron microscopy analyses. The prepared samples presented very high performances in terms of photocatalytic activities, analyzed by the degradation of an organic dye in a liquid medium, and of bactericidal activities, tested on Staphylococcus aureus (S. aureus, a Gram positive bacterium) and Escherichia coli (E. coli, a Gram negative bacterium)

Synthese de methane et d'hydrocarbures legers a partir de gaz de synthese par catalyse en phase liquide

CNRS-CDST / INIST-CNRS - Institut de l'Information Scientifique et TechniqueSIGLEFRFranc

Photostability and photobactericidal properties of porphyrin-layered double hydroxide-polyurethane composite films

International audienceThe photostability and photobactericidal properties of PdTPPC (Pd(ii)-5,10,15,20-tetrakis(4-carboxyphenyl)porphyrin)-Zn2Al/PU (polyurethane) composite films have been studied in order to investigate their applicability as new photodynamic surfaces. These films comprise a PdTPPC porphyrin photosensitizer intercalated between the lamella of Zn2Al layered double hydroxide and dispersed (1 wt%) into a polyurethane matrix. The study of the photophysical behaviour shows that the Zn2Al LDH host enhances the chemical stability of the PdTPPC guest by minimizing photobleaching and quenching aggregation effects. The singlet oxygen production under irradiation of PdTPPC-Zn2Al/PU composite films is confirmed by the observation of an O2(1Δg) emission band centered at 1274 nm. Furthermore, the value of the rate constant kq for the PdTPPC phosphorescence quenching by oxygen kq = (8.2 ± 0.3) 10-2 s-1 Pa-1 indicates a slow diffusion of oxygen into and out of the PU polymer. In a second step, accelerating light ageing tests are conducted to determine the effect of singlet oxygen production on the chemical and mechanical stability of the PU matrix. Oxygen uptake experiments coupled with ATR-IR measurements indicate the probable formation of hydroxylated photoproducts but with no detrimental effects on the microstructure and the viscoelastic properties of the PU matrix as evidenced by dynamical mechanical analysis. Finally, in vitro preliminary antimicrobial tests show that PdTPPC-Zn2Al/PU composite films are able to inhibit S. aureus growth with no release of PdTPPC biocide from the PdTPPC-Zn2Al/PU composite film. We also observe a total inhibition of P. aeruginosa growth suggesting an efficacy against biofilm formation