Aldo Sanguineti

A study on a perfluoropolymer purification and its application to membrane formation

Abstract In this work, a study on a perfluoropolymer purification with crossflow MF and UF, using commercial membranes, has been carried out. Copolymers of tetrafluoroethylene (TFE) and 2,2,4trifluoro, 5trifluorometoxy 1,3 dioxide (TTD), known commercially as HYFLON® AD, are highly transparent to light from deep UV to near infrared, so they find applications in optic and electronic industries, such as plastic optical fibers (POF), anti-reflective coating and protective pellicles in manufacturing semi-conductor. For the above application, it is often crucial to avoid the presence of both suspended and dissolved contaminants in the polymer and polymeric solutions. Membranes made from this amorphous perfluoropolymer were prepared in flat sheet, tubular and hollow fiber forms. Tests of membrane hydrophobic character and of pure gas permeability were carried out. Experimental gas separation data obtained with membranes prepared with TTD–TFE co-polymers and data from the literature on membranes made with co-polymers of perfluoro2,2dimethyldioxide (PDD) and TFE, commercially known as TEFLON® AF, revealed an interesting linear relationship between permeation and glass transition temperature Tg. The voids volume fraction (Φv) of the above amorphous perfluoropolymers was also estimated from the difference between the experimental polymer density and a theoretical density obtained by simple calculations using the group contribution method.

Hydrophobic carbonaceous materials obtained by covalent bonding of perfluorocarbon and perfluoropolyether chains

Perfluorocarbon residues, i.e. perfluoroethyl (PFE), CF3CF2–, perfluoro-n-propyl (PFnP), CF3CF2CF2–, perfluoro-isopropyl (PFiP), (CF3)2CF–, and perfluoropolyether (PFPE) chains, e.g. (CF2CF2O)m(CF2O)n, were covalently bonded on the surface of carbon black (CB) and diamond-like carbon (DLC) using PFPE and perfluorodiacyl (PFDA) peroxides. The thermal decomposition of the peroxidic moieties of these perfluorinated peroxides generated reactive perfluorinated radicals. The perfluorinated free radicals could directly bond to the sp2 sites avoiding any spacer, which usually decreases both thermal and chemical stabilities of the resulting materials. The effects of chemical treatment on the carbonaceous materials were studied using X-ray Photoelectron Spectroscopy (XPS), Scanning Electron Microscopy (SEM) and Contact Angle (CA) measurements. The surface areas of CB powders were determined by the BET technique; the morphology of the DLC coatings was evaluated by Atomic Force Microscopy (AFM) and the friction forces were measured by means of Lateral Force Microscopy (LFM).

PTFE nanoemulsions as ultralow-k dielectric materials

Modern integrated circuits require insulating materials with a dielectric constant as low as possible in order to obtain device speed improvements through lower RC delay. We have investigated the electrical and structural properties of PTFE thin films obtained from Algoflon®-PTFE nanoemulsions, via spin coating deposition, followed by sintering. Films as thin as 160 nm with dielectric strength better than 4 MV/cm have been obtained.

Preparation and properties of poly(urethane-urea) crosslinked coatings from perfluorocopolyethers and polyfunctional isocyanurates

Two model isocyanate terminated resins were synthesized by addition of perfluorocopolyether oligomer (M n ca. 1000) with cyclic polyiosocyanurates of hexamethylene diisocyanate (HDI) and isophorone diiso-cyanate (IPDI). The resins were characterized by chemical titration, gel permeation chromatography, FT-IR spectroscopy, and viscosity. The two resins, and some blends of them, were crosslinked through urea bond formation by exposure to atmospheric moisture. The resulting coatings were characterized by dynamic mechanical spectroscopy (DMS), tensile properties, abrasion resistance, adhesion, atomic force microscopy (AFM) and contact angle measurements. Phase separation phenoma and mechanical properties were related to composition and thermal transitions of both hard and soft phase. Adhesion (pull-off) was poor on inorganic surfaces like glass and aluminium ( 5 MPa). The use of organosilane adhesion promoters was successfully investigated. Surface analysis by AFM showed the formation of a chemically heterogeneous very smooth (on a nanoscale) surface. Contact angle determinations with water, diiodo-methane and hexadecane were carried out. The total surface energy of coatings was calculated by the harmonic mean approximation and resulted typically low (16.0-17.5 mN/m) and unaffected by the coating bulk composition.

A Measurement System For Investigating The Dielectric Properties Of Low-Loss Polymers

Abstract Polymers with low dielectric losses are largely used in several electromagnetic applications, for example in telecommunications cables, antennas, and microwave devices and components. The interest in studying their dielectric properties has a twofold motivation: (1) a scientific motivation, because the study of polymers is one of the main fields of material science; and (2) an industrial one, because a material with better dielectric characteristics—i.e. lower dielectric losses—is commercially more suitable for the market. The measurement of both dielectric constant and losses is not a straightforward task when dealing with low-loss materials. In this paper we describe a measurement system, based on a revisitation of the well known method of re-entrant cavity, which by a thorough electrical modeling of the sample holder allows absolute measurements to be performed on dielectrics with loss tangent as low as 10−4. The technique is validated on low-loss substrate materials of known characteristics. Measurement examples are reported concerning two fluorinated polymers based on TFE and ECTFE.