Thermal fuses

Electrostatic painting is the application of electrostatically charged paint particles to an oppositely charged workpiece followed by thermal fusing of the paint particles to form a cohesive paint film. Both waterborne and solvent-borne coatings can be sprayed electrostatically. 

Figure 12.17 Photomicrograph of tricot knitfabric, made from core/sheath (C/S) bico filament yarn and thermally fused after knitting. Photograph reproduced by permission of KoSa Corporation...

THERMAL-FUSED AUTO BOMB (SECTIONED SIDE VIEW)... 

For the fuse problems with various other criteria of failure, for example breakdown due to local Joule heating in a random thermal fuse model, see Sornette (1987) and Sornette and Vanneste (1992) and also Section 2.2.6. 

Samples of varying pulp composition, varying filler content, and those with and without both bulk and surface sizing are discussed. The performance differential of the various paper surfaces in the adhesion of thermally fused, xerographically toned images is addressed. 

The BA5590 consists of 10 lithium sulfur dioxide (Li/SOa) D cells wired in a cardboard container which also contains diodes, electrical and thermal fuses, a connector, and a resistor with a manual switch to fully discharge the battery prior to disposal. When flesh, each battery contains the following materials ... 

In the case of calcined kaoUn, individual kaolin plates are thermally fused into a clustered shape. With scalenohedral and aragonitic PCC, either a rosette or repetitive needle structure is formed through carefully controlled reactions of milk of lime and carbon dioxide. Amorphous silica products are chemically aggregated into repeating silica rings. 

An abnormal increase in cell temperatnre can occur from internal heating caused by either electrical abuse - overcharge or short circuit - or mechanical abuse - nail penetration or crush. Higher cell temperature also could be a result of external heating. For this reason, battery packs containing Li-Ion cells are designed with safety control circuits that have redundant safety features (PTC, CID, vent, thermal fuse, etc.). Shutdown separators are one of the safety devices inside the cell and act as a last line of defense. The separator shut down is irreversible, which is fine for poly-ethylene-based separators, which melt around 130°C. 

The benefit of using small cells is that many of them have built-in safety features such as temperature-driven resettable thermal fuses and pressure-driven current interrupt devices and vents. The small cells may also reduce the impact of a single-cell failure... 

One of the benefits of the prismatic cell is that it has the higher capacity typical of laminate cell, but it also may integrate some of the safety features of the small cells such as vents and, occasionally, thermal fuses. The prismatic cell may also use a mechanical connection to the cell which reduces the need to weld the bus bars to make the cell to cell connections in a pack. The issues of this cell format include the risk of cascading failure (much more energy is released in a large cell failure). In addition, as these cell formats are still produced in relatively low volumes, ramping up the manufacturing to volumes and quality that match those of the 18650 format will take time. 

FIGURE 16.2 Monitoring and controlling functions using the Dexerials Corp. selfactivated with an electronic control [4], Graphic courtesy of Dexerials Corp., used with permission. 

Thermal Fuse This device is wired in series with the cell stack and will open the circuit when a predetermined temperature is reached. Thermal fuses are included as a protection against thermal runaway and are normally set to open at approximately 30-50°C above the maximum battery operating temperature. They do not reset. 

The low melting point of polyethylene (PE) materials enables their use as a thermal fuse. As the temperature approaehes the melting point of the polymer, 135°C for polyethylene and 165°C for polypropylene (PPE), porosity is lost. Tri-layer materials (PPE/PE/PPE) have been develop where a polypropylene layer is designed to maintain the integrity of the film, while the low melting point of polyethylene layers is intended to shutdown the cell if an over-temperature condition is reached. 

Many new materials have been developed for transporting water effectively and separately [6-9], including crosslinked cellulose called curly fibers, thermally fused PE/PP fibers, and a special nonwoven rayon cloth. These new materials absorb a liquid quickly and distribute it to the superabsorbent polymer. In addition, these new materials show good integrity to moisture. In particular, there is no corruption of the structure even after wetting, allowing the maintenance of chaimels through which the liquid ean be transferred. 

Finally, with regard to revolutionary design, many systems adopt an acquisition layer or a combination of an acquisition layer and transport layers between the absorption core (Fig. 2) and the top sheet [9]. For the acquisition layer or the transport layer, either a crosslinked cellulose with a density of 0.04-0.1 g/cm, thermally fused PE/PP fibers, or a nonwoven cloth is used. The absorption core consists of surface-crosslinked superabsorbent polymer and pulp. In general, the concentration of the superabsorbent polymer is 40 to 60 wt %, and the weight of the polymer used per diaper is approximately 10 to 12 g [9,10]. 

A trilayer stmcture of PP/PE/PP Celgard microporous membranes provides exceptional puncture strength [19]. In addition, the low-melting PE layer (135 °C) can act as a thermal fuse, while the higher-melting PP (165 °C) layers provide... 

Thermal fuse limits the current under fault conditions external to the cell. 

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