Plastic cell test

A very important but often neglected aspect of in vitro toxicology is pharmacokinetics or toxicokinetics. Kinetics deals with how a test compound is altered by the system it is applied to. For an in vitro system, the available concentration of the compound can be decreased by binding to cell culture-ware such as a plastic cell culture dish, by binding to proteins in the cell culture medium, by evaporation and due to cellular uptake or cellular metabolism. The latter two points are critical in both in vitro and in vivo systems and are discussed in detail in Chap. 22. Knowing the actual concentration that cells can interact with, either by measurement as a free concentration in the cell medium or as a tissue concentration in the cell lysate, is crucial not only for experimental interpretation but also to extrapolate to the in vivo situation. Indeed, we must eventually extrapolate from in vitro to in vivo in order to establish safe exposure limits, which is after all the end goal of the exercise. These issues are dealt with in Chaps. 23 and 24. 

The obtaining of good mechanical properties is obviously an important issue because the end of a fuel cell test is directly related to a general or local membrane breaking. To our knowledge, the study of SPI mechanical properties is limited in the literature to the measurement of stress-strain curves in the dry and water-swollen states [39,110,112,126]. These curves present an elastic behavior limited to few percent of deformation followed by a plastic linear behavior (Fig. 44). Despite the polymer being in a glassy state, the water sorption induces plasticization. The maximum tensile stress at break is of the order of 70 MPa for SPI compared to less than 20 MPa for Nafion and the elon-... 

Tlie indi ddual cells are assembled into batteries after a leakage test to check for faulty welding joints in steel containers or cracks and improper seals in the plastic encased cells. Cells that are to be delivered without electroltye are emptied after the fomiation cycles. Tlie steel-cased cells hav e to be separated by mechanical means to prevent intercell shorts and are often assembled into wooden crates. Tlie cells in plastic cases can be cemented together or strapped with tape. 

This is the most common test method employed to qualify the leak characteristics of a new seal material. The test method involves applying the seal between two ceramic discs or between a ceramic and a metal disc, pressurizing the cavity formed by the seal and monitoring the pressure decay as a function of time.22 Alternatively, a metal tube and a ceramic disc can also be used [34], Typically, the cavity is pressurized to about 2 psi and the leak rate is determined by the pressure decay as a function of time. These tests can be done at room temperature or elevated temperatures. Similar test arrangement has also been used to test a plastically deformable brazed metal seal between fuel cell anode material and Haynes 214 washer [35], The cavity is pressurized to measure the rupture strength of the seal material. 

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