Blowup ratio

Extrusion temperature of the PVDF/PMMA was in the range of 220°C-240°C. The preferred drawdown ratio of the first bubble was in the range of 10 1 to 15 1, and 2 1 to 3.75 1 forthe second bubble. The desirable blowup ratio ranged from 1.5 1 to 1.75 1. A cooling air temperature of 10°C-20°C was required while the hot air temperature, before the second bubble, varied from 120°C-140°C. The film can be dimensionally stabilized by an annealing process at 120°C for 5 minutes. 

After extrusion, blown-film is often slit and wound up as flat film, which is often much wider than anything produced by slot-die extrusion. Thus, blown-films of diameters 7 ft. or more have been produced, giving flat film ofwidths up to 24 ft. One example is reported [16] of a 10-in. extruder with 5-ft diameter and a blowup ratio of 2.5, producing 1,100 Ib/h, or polyethylene film, which when collapsed and slit in 40 ft wide. Films in thicknesses of 0.004-0.008 in. are readily produced by the blown-film process. Polyethylene films of such large widths and small thicknesses find extensive uses in agriculture, horticulture, and building. 

BUR blowup ratio (see also BR) CAPP computer-aided process planning... 

All HIDM and twin screw color concentrate samples were letdown into blown film for evaluation of color, strength and dispersion quality. Standard 1.5 mil (37 pm) films were prepared by blending concentrate samples with 1.0 MI LLDPE resin at a letdown of 5.0 weight percent and extruding through a 37.5 mm laboratory film line at a blowup ratio of 2.4 1 and lay flat width of 20 cm. Standard operating procedures were observed throughout. 

Blowup Ratio In extrusion blowing of film, it is the ratio of the extrusion die diameter and the diameter of the tubular film. In blow-molding, it is the ratio between the diameter of a parison and the maximum diameter of the mold cavity. 

In blow molding, one of the parameters used in the BUR (blowup ratio). The BUR is defined as the ratio of the final radius to the original radius. Would it be possible to obtain a value of unity for BUR for certain temperatures and values of the dimensionless ratio ttR AP/ixappGj where Ro is the original radius, AP the pressure inside the parison, Q the volumetric fiow rate, and Xapp the apparent viscosity of the polymer ... 

Another term is the product of the two ratios known as the blowup ratio (BUR) ... 

The blowup ratio, BUR, is the ratio of the final bubble radius to the initial radius and is an analog of the draw ratio in spinning. Primes denote differentiation with respect to the dimensionless axial length, which is normalized with respect to Ro. The differential equations are more complex for viscoelastic liquids, and the stress equations must be solved in parallel with the momentum equations, r = w = 1 at the exit from the die, and r = 0 at the freezeline. The last boundary condition assumes that the viscosity becomes infinite at the freezehne and that there is no further deformation. (This condition is approximate at best and need not be used when a solidification model in which the sohd phase evolves and locks in structure is employed.) Heat transfer is very important, although it has usually been handled with rather simplistic assumptions about the heat transfer coefficient. 

Here, TUR = (thickness reduction)/BHi andPg = 2B in terms of the nomenclature used in Section 10.4 TUR and BUR are the takeup ratio and blowup ratio, respectively. The region marked U is unstable according to the linear theory. Only results for BUR > 1 are of practical interest. We see that both draw resonance and helical instabilities can occur, with the latter comprising a large part of the parameter space for dimensionless pressure B less than about 0.25 (pg < 0.50). This is consistent with what is seen experimentally, although the comparisons are qualitative. 

The two main parameters of this process are the blow ratio (or blowup ratio), Br (or BUR), and the machine-direction draw (or draw-down) ratio. Dr. The blow ratio is defined as the ratio of the final tube radius, R, to the initial tube outside radius just downstream of the annular die, Ro (see also Figs. 9.20 and 9.21, and Section 1.2) ... 

The thickness of a film is controlled by extruder output rate, die gap, blowup ratio, and take-up rate. The die gap is changed by raising or lowering the conical core of the die. By appropriate manipulation of the blow-up ratio and the take-up rate, it is possible to generate films that have the same thickness but... 

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