There is clearly an articulated need by the semi-conductor industry, the food and beverage industry, the chemical process industry, the pharmaceutical industry and others for an inert, chemical resistant, high temperature and most importantly cost effective membrane media.
These markets require a membrane and potting system which will not leach contaminants into the process stream, which will stand up to repeated pressure and temperature swings, robust fibers assembled with a potting system with properties as good as the fiber.
Markel porous PTFE hollow fibers open the door to significant opportunities in these markets by offering a membrane filtration system that has previously been unavailable via polymeric membranes.
The advantages offered by Markel porous PTFE hollow fiber membrane system fall into three broad categories: the material properties of the fiber, the inherent advantages of hollow fiber over flat sheet products, and the Markel fluoropolymer potting technology.
Markel has developed a family of modules using our porous PTFE hollow fibers which can be employed in either micro filtration or ultra filtration applications. Speak with a Markel design engineer to develop a fiber system that is suitable for your application.
Porous PTFE hollow fibers have a very low surface energy (are extremely hydrophobic), even when compared to hollow fibers produced from other fluoropolymers such as PFA or PVDF. The low surface energy is a key element for a large segment of membrane filtration applications. This serves as an advantage when working with organic systems or when working with aqueous systems when one wishes to exclude or isolate water from a second phase. Use of a coating to render the surface hydrophilic allows one to take advantage of the properties of PTFE for aqueous or high surface energy liquids.
With PTFE, there is virtually no leaching of contaminants into process stream, making product ideal for food, pharmaceutical, beverage, electronic chemical markets. There are no residuals left over from the polymerization or isolation processes. PTFE is one of the primary polymeric materials employed in the medical device market due to this attribute.
One of the key advantages of PTFE is it is the ideal product for working with acidic, caustic, or corrosive process streams, organic solvent systems, etc. The chemical resistance of PTFE also opens considerably more options for cleaning the membrane than conventional resins or metals. PTFE hollow fibers may be chemically cleaned, autoclaved, etc. Only sintered metal or ceramic membranes offer equivalent options on cleaning.
The high service temperature of PTFE will allow this product to out perform other polymeric filter media and leaves it second only to glass or metal filter systems in range of service temperature.
PTFE’s resistance to bacterial growth and the ability to clean, sterilize (autoclave, chemical, ultraviolet, thermal, etc) offers advantages to the food and pharmaceutical industries.
Markel’s Potting Technology is Designed Specifically for PTFE Membrane Filtration.
If the fiber and the pore structure associated with the fiber represent the core of the membrane device, then the technology for containing and holding the fibers is a key enabling technology.
Generally speaking, polymeric porous hollow fibers are employed in bundled arrays of fibers housed in a shell. The fibers are assembled into bundles wherein all the ends of the fibers are aligned at each end of the device and glued or attached in some way so as to seal the outside of the fiber from the lumen of the fibers. The end arrangements are usually referred to as potted ends, tube sheets, or equivalent. This potting is often the weak link in a module. For other fibers on the market such as polyolefin, polypropylene, or polysulfone, epoxy or urethane compounds are often employed.
At Markel, we recognize the need for a potting system that is as chemically robust as the PTFE fiber itself and toward that end have developed proprietary potting technology that employs fluoropolymer potting compounds.
There are several advantages of Hollow Fiber PTFE Membranes over PTFE Sheet.
While many types of membranes are available in sheet form, the ability to create significantly higher surface area per unit volume with a hollow fiber membrane is of major advantage to the designer and user of a membrane filter or contactor.
A hollow fiber membrane is also typically self-supporting in contrast to flat sheet or thin film branes that usually require a skeletal structure for support.
In addition, typical contactor designs employing hollow fiber membranes, whether constructed as a cross flow element or in a dead-end configuration, offer more uniform flow and fewer regions for the flow to stagnate.