Film blowing case study

FIGURE 1.12 Reaction injection molding (RIM) process. (Reprinted by permission of the publisher from Becker, 1979.) 

The intention in Section 1.1 was more than just to review the technology of polymer processing, but to point out factors that must be considered in the design of polymer processes. However, since most students have little knowledge of the technology of processing of polymers, some general introduction is of value. Furthermore, a physical picture of the various processes is required to facilitate the discussion of the material presented in the next four chapters. 

TABLE 1.1 Die Recommendations for the Blowing of PBl with a Blow Up Ratio of 2.4-2.8 at a Melt Temperature of 

Fihn Thickness (x lOMn.) Die Gap (inches) Land Length (inches) 

FIGURE 1.14 Effect of the annular die land length on the flhn tear strength of polybutylene extruded at the rate of 10 m/min for two different flhn thicknesses. 

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Finally, four case studies will be presented, which correspond to different influences of the processing conditions on the final microstructures. In cast film extrusion, crystallization occurs after cessation of flow, and the thermal conditions are very important. In fiber spinning and film blowing, it takes place during flow in uniaxial or biaxial conditions, respectively. In injection molding, different situations may be encountered as a function of the location in the part. 

To study the influence of the roughness of superhydrophobic surfaces (treated in O2 plasma and then in CF4 plasma) on their dewetting behaviour, other dewetting measurements were carried out. A thin water film was deposited onto the surface. Its dewetting was induced by blowing air in the center of the surface and then the diameter of the dry area was measured in these cases with dry (virgin or plasma-treated) surface or prewetted (virgin or plasma-treated) one by water vapour (Fig. 16). 

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