Vincenzo Arcella

High Performance Perfluoropolymer Films and Membranes

Abstract: Membrane processes are receiving increasing attention in the scientific community and in industry because in many cases they offer a favorable alternative to processes that are not easy to achieve by conventional routes. In this context, membranes made with perfluorinated polymers are of particular interest because of the unique features demonstrated by these materials. Both highly hydrophobic and hydrophilic membranes have been developed from appropriate perfluoropolymers that were, in turn, obtained by copolymerizing TFE with special monomers available on an industrial scale. Highly hydrophobic membranes obtained from the glassy copolymers of TFE and 2,2,4‐trifluoro‐5 trifluoromethoxy‐1,3 dioxole (Hyflon® AD) exhibit properties that make them particularly well suited for use in optical applications, in the field of gas separation, and in gas‐liquid contactors. Conditions for preparing membranes that are adequate for use in various applications are exemplified. Hydrophylic highly conductive proton exchange membranes obtained from the copolymer of TFE and a short‐side‐chain (SSC) perfluorosulfonylfluoridevinylether (Hyflon Ion) find interesting application in the field of fuel cells, especially in view of the current tendency to move to high temperature operation. The advantages offered by these hydrophobic and hydrophylic perfluorinated materials for use in membrane technology are discussed. Comparison of membrane properties and performance is made with other membranes available on the market.

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.

Membrane Electrode Assemblies Based on HYFLON® Ion for an Evolving Fuel Cell Technology

Abstract The work presents an overview of the main properties of Hyflon® Ion perfluorosulfonic acid (PFSA) membranes for fuel cells in comparison with Nafion® PSFA membrane. The fuel cell performance of Hyflon® Ion‐based membrane electrode assemblies (MEAs) is reported at medium (75°C) and high (120°C) temperature, demonstrating extremely good power output. Remarkable durability (5000 h) of the Hyflon® Ion product is also demonstrated in high power output conditions. The conductivity and the hydrogen permeability of Hyflon® Ion extruded membranes is reported in sub‐freezing conditions (down to −40°C). The degradation of the short‐side‐chain ionomer is investigated utilizing both ex‐situ (Fenton) tests and fuel cell open circuit voltage tests. In the latter, the influence of the operating temperature on Hyflon® Ion degradation is not detectable in the range analysed (70°C–90°C). A better resistance to degradation of chemically stable Hyflon® Ion membranes (“S”‐grades) vs. standard membranes results from all tests.

New HYFLON AD composite membranes and AFM characterization

HYFLON AD membranes are very interesting devices in water treatment and for their impermeability to water and gases and vapour transpirability [1]. In these kinds of processes, such in many large-scale processes, some membrane parameters are particularly important, among them: pore distribution, membrane morphology and their fouling tendency. The aim of the present work is to describe an AFM study of three different composite HYFLON AD 60X membranes characterising three key properties affecting performance: pore size distribution, surface morphology and particle adhesion. The membranes have been imaged at high resolution in NaCl solution, allowing quantification of surface roughness and pore size distribution. Further, the adhesion of polystyrene and silica particles to the membranes was measured in NaCl solution at three different concentrations to quantify their likely fouling tendencies.

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.

Advances in fluoropolymer dispersions

SummaryMultimodal high-performance fluoropolymer dispersions have been developed thanks to Solvay Solexis’ proprietary technology which permits bimodal particle-size distributions to be obtained, not only by blending standard fluoropolymer dispersions (diameter 250nm) with nano-latexes (diameter from 10 to 60nm), but also directly from polymerisation, exploiting a competitive homogeneous/coagulative and droplet nucleation mechanism. It has been found that poly(tetra-fluoroethylene) (PTFE) bimodal dispersions have optimal film-forming and particle-packing behaviour at a size ratio of about 0.15, corresponding with the best fit to the random close-packing model, while no significant improvements are observed when the aforesaid size ratio is 0.3.

1.08 – Amorphous Perfluoropolymer Membranes

The low energy consumption and the technological simplicity of the membrane-separation processes has led, in the last two decades, to a significant development of these technologies for industrial separations of mixtures of gases and liquids. Among the different types of membranes available in the market, those based on fluoropolymeric materials are of increasingly greater interest thanks to some unique properties, such as their excellent stability in harsh conditions, that is, in the presence of strong reactive chemicals and high temperatures. Moreover, amorphous perfluoropolymers, having a high solubility in fluorinated solvents, can be advantageously used for the preparation of membranes both by solution and by melt processing. The simplicity of the membrane-separation process and the possibility of production of membranes with different selectivities make them very promising for a wide range of applications. In this chapter, a review of the developments in the field of amorphous perfluoropolymeric membranes, with both hydrophobic and hydrophilic character, is presented and discussed.