Draw force

The bubble will grow to a maximum —or final— radius, Rf, when it freezes at a position z = Z, which is called the freeze-line. Since the bubble is pulled by a force Fz, which is usually referred to as the draw force, we can perform a force balance between a position z and Z to give,... 

Film blowing. A tubular 50 pm thick low density polyethylene film is blown with a draw ratio of 5 at a flow rate of 50 g/s. The annular die has a diameter of 15 mm and a die gap of 1 mm. Calculate the required pressure inside the bubble and draw force to pull the bubble. Assume a Newtonian viscosity of 800 Pa-s, a density of 920 kg/m3 and a freeze line at 300 mm. 

The mechanical draw force which has to be applied must at least overcome the above acting forces to ensure safe web run. 

Bonding temperature has a minimal effect on the final erystallinity of the webs, but it has a noticeable influenee on their thermomeehanieal behavior. Localization of crystallization during spunbonding of PP sets in along the spin line. In contrast to conventional melt blowing, the drawing force on the extruded... 

Figure 9.10. (a) Extrusion of billet with plunger providing pressure (p) and (b) rod drawing with drawing force P) transmitted through product. 

Glass fibre production tools are very different when considering optical fibres, rovings or glass wool. Processes differ in the way drawing force is applied and three drawing modes are distinguished ... 

We then consider the analysis of the film blowing process, which should be based on the maximum die swell dimensions as the initial dimensions and isothermal conditions are assumed. Calculate the pressure of the blowing air, the drawing force, and the velocity at the nip rolls if the dimensionless frost line height is confined to 5 and the distance of the nip-roll system from the position where the maximum die swell level occurs is 1.5 m. 

---