PTFE/PVDF

Ultrathin PTFE, PVDF, and FEP Coatings Deposited Using Plasma-Assisted Physical Vapor Deposition... 

PA PCP PCR PFA PGB PHA PID PLC PMACWA PMD POTW ppm PRH PRR psi psig PTFE PVDF PWS picric acid pentachlorophenol propellant collection reactor perfluoroalkoxy product gas burner preliminary hazards analysis proportional integral differential controller programmable logic control Program Manager for Assembled Chemical Weapons Assessment projectile mortar demilitarization (machine) publicly owned treatment works parts per million projectile rotary hydrolyzer propellant removal room pounds per square inch pounds per square inch gauge polytetrafluoroethylene (Teflon) polyvinylidene fluoride projectile washout system... 

Two configurations of liquid membranes are mainly used in analytical applications flat sheet liquid membranes that give acceptable extraction efficiencies and enriched sample volumes down to 10-15 pL, and hollow fiber liquid membranes that allow smaller enriched sample volumes. Flat sheet liquid membrane devices consist of two identical blocks, rectangular or circular in shape, made of chemically inert and mechanically rigid material (PTFE, PVDF, titanium) in which channels are machined so that when... 

ETFE, PFEVE, PTFE, Amorphous PTFE ECTFE, FEP, MFA, PFA, PFPE, PTFE, PVDF Fluorocarbon elastomers (VDF-HFP, VDF-HFP-TFE, VDF-HPFP, VDF-HPFP-TFE)... 

Gaskets in both dry gas and liquid chlorine systems are made of rubberized compressed asbestos. For wet chlorine gas, rubber or synthetic elastomers are acceptable. PTFE is resistant to both wet and dry chlorine gas and to liquid chlorine up to 200 °C. Tantalum, Hastelloy C, PTFE, PVDF, Monel, and nickel are recommended for membranes, rupture disks, and bellows. 

There are also techniques involving the use of nonporous, solid or liquid membranes that separate the donor phase from the receiving phase by an evident phase boundary. Most often used are three-phase systems (donor phase, membrane, and acceptor phase) or two-phase systems, in which one of the surrounding phases is the same as the membrane. Solid membranes are made of chemically resistant, hydrophobic polymers (PTFE, PVDF, PS, PP, silicates), metals (Pd alloys), or ceramic materials. Channels of membrane modules have a volume ranging from 10 to 1000 pL and, according to their geometry, can be classified as planar or fibrous. For setting up a membrane system, two modes can be used the membrane can be immersed in a sample (membrane in sample, MIS) or the sample can be introduced into a membrane (sample in membrane, SIM). In both systems, only a small amount of sample is in direct contact with membrane, because ratio of the membrane surface area to the sample volume is small. 

Unlike conventional PTFE, PVDF can be molded through compression and injection processing and extruded into various shapes and configurations with conventional extruders. As a matter of fact, PVDF has been routinely processed on equipment that are also used for PVC and polyolefins. 

SR etching has been carried out to deposit thin films of many polymers such as PTFE, PVDF, ETFE and so on, demonstrating that it may also be a simple and versatile method for fabrication of thin polymeric films, like laser ablation deposition. 

Lined pipe Isostatic molding, melt extrusion, paste extrusion PTFE, PVDF, PFA, ETFE, ECTFE... 

The choice of the membrane depends on several factors chemical and thermal resistance to the process conditions, sharp separation, wettability of the membrane, tendency to adsorb hydrophobic materials and resistance to cleaning. The most common polymeric materials are PTFE, PVDF, PP, PS, CA/CN, CTA, PE, polycarbonate, polyester, poly ether imide and nylon 6. Of these, only PTFE, PVDF and PP have excellent to good chemical stabiHty. Even though hydrophilic CA/CN and CTA membranes have limited chemical stabiHty, they are best suited for treating high fouling feeds using tubular membranes. 

Figure 6.1 provides one of the set of results obtained for various polymers and ethylene carbonate (EC). EC is chosen as a typical solvent molecule. Each bar shows a calculated redox window. The bottom part of each bar represents the energy level of the HOMO of a certain molecule and its top represents the energy level of the LUMO of the same molecule. The HOMOs of FIFE, PVdF, and polyacrylonitrile (PAN) are lower than those of other polymers. This resirlt means that it is very difficult to remove an electron from PTFE, PVdF, and PAN that is, these polymers can be stable in a cathodic environment... 

Most pumps in HCl service are nonmetallic. Wetted parts may be PVC, CPVC, PP, PTFE, PVDF, FRP, ceramic, or carbon. Self-priming centrifugal pumps are a standard, but diaphragm-type metering pumps also are widely used. 

In many cases, the concentration level obtained by evaporation is relatively high, but the use of the OMD technique avoids any thermal damage or loss of the solutes. The OMD process works in this way a porous hydro-phobic membrane (generally PTFE, PVDF, or PP), is in contact with two different non-wetting aqueous solutions for example a juice solution and a concentrated salt solution (stripping solution or extractant). The different water activity of the two solutions corresponds to two different water vapour pressures. Due to the combination of hydrophobicity and the narrow pore size of the membrane, neither the first solution nor the extractant passes through the membrane pores. Only water vapour is allowed to diffuse, and the water vapour pressure difference between the two sides of the membrane constitutes the driving force of the process. 

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