Mario Pegoraro

Degradation of outdoor exposed poly (1-trimethylsilyl)-1-propyne

Abstract The outdoor ageing of poly(1-trimethylsilyl)-1-propyne (PTMSP) membranes has been studied mainly by means of differential scanning calorimetry (DSC), thermogravimetry, viscosimetry and infra-red spectroscopy. Membranes lose their integrity within 288 h of exposure. After exposure for 192 h the oxidation time at 523 K decreases from 25 to 0.5 min, while the starting temperature of degradation, as measured by DSC, changes from 543 K to 393 K and the viscosimetric molecular weight decreases five times. The high speed of the photodegradation process can be accounted for by the high oxygen solubility of this polymer.

MODIFICATION OF POLYMERS FOR THE PREPARATION OF SEMIPERMEABLE MEMBRANES

ABSTRACT A short survey is made of the principles to be followed in order to prepare membranes fit for the fractionation of a solute from a solvent. First it is essential to use substances with convenient chemical properties and then to prepare different membrane structures depending on the fractionation to be done. The reaction of grafting is recognized as a very important means for the preparation of convenient materials. As an example, we report the results obtained in the desalination process using membranes consisting of polyacrylic acid grafted on polypropylene. Membranes may be obtained from solutions or by grafting in the heterogeneous phase on films bi- or mono-oriented through a radical mechanism by peroxidation or γ-irradiation. Membrane structures observed with the electron microscope are described and the various results obtained in the desalination process are interpreted on the basis of the membrane structure. An interpretation is also given of the several transmission rates of water vapour, detected in the different types of membranes.

A 1H NMR Study of the Kinetics of the Reaction of Diisocyanates with Ethlene Oxide-Dimethylsiloxane-Ethylene Oxide Block Copolymer

Abstract The reaction of pure 2–4 and 2–6 tolylene diisocyanate with an OH terminated ethylene oxide-dimethylsiloxane-ethylene oxide ABA block copolymer was carried out directly in a n.m.r. tube. The kinetic of the reaction was studied by 1H nmr spectroscopy.