Area draw ratio

A third measure is the area draw ratio (ADR). This is the cross-sectional area between the tip and die divided by the tubing cross-sectional area. 

It should be noted that sometimes the area draw ratio is represented by the letters DDR as an acronym for drawdown ratio. Obviously, this can cause confusion with the diameter draw ratio. Often the area draw ratio is called simply the draw ratio. It is important therefore to check what exactly is meant when the term draw ratio is used. The ADR can be calculated from the WDR and the DDR as follows ... 

Thus, the wall and diameter draw ratios determine the area draw ratio in the extrusion process. A high ADR increases orientation and the chance of pinholes and breakaways. A low ADR reduces orientation and increases the chance of melt fracture. 

As explained in Chapter 17 die configurations meet certain melt flow requirements such a drawdown ratio and draw ratio balance. Draw-down ratio (DDR) in a circular die, such as a wire die, is the ratio of the cross sectional area of the die orifice/opening to the final extruded shape. Another guide for setting uniformity and best repeatable references is the draw ratio balance (DRB) that aids in determining the minimum and maximum values that can be used for different plastics. 

The full potential of the hydrostatic extrusion technique became apparent in 1974, when the production of ultra high mudulus polyethy lenes with stiffnesses up to 60 GPa were reported The main process parameter in hydrostatic extrusion is the nominal extrusion ratio Rj, the ratio of the billet cross-sectional area to that of the die exit (assuming deformation occurs at constant volume, which is a very good approximation). Because polymers can exhibit die swell in extrusion, it is convenient also to define an actual extrusion ratio R, based on the ratio of the initial and final billet cross-sections. R is, of course, direcUy comparable to the draw ratio in tensile drawing (assuming plug-flow) and in practice R R for all but the lowest reduction ratios. 

The nominal extrusion ratio or nominal draw ratio (Rn) is determined by the ratio of the billet cross-sectional area to that of the die bore. As it will be discussed below, die swell is often observed in solid-state extrusion experiments Therefore, the actual draw ratio (Ra) is often smaller than the nominal value. 

In Table 1 data on the extrusion behavior of some polymers and copolymers are summarized. Many of these data refer to the paper by Aharoni and Sibilia Some of the polymers listed in Table 1, namely the nylons and the copoly(ether ester)s, do not fulfill the requirements defined by Aharoni and Sibilia. Especially, the maximum achievable draw ratio seems to be less than ten for these systems. However, together with other workers in this area, we think that the term solid-state extrusion covers a wider field of interest than indicated by Aharoni and Sibilia. 

Typical X-ray diffraction patterns of the equatorial scattering areas for spin-drawn fibers spun at draw ratios of 4 and 7 are shown in Fig. 6a and b. 

From the debonding angle and the local draw ratio, it was possible to calculate a void content in the drawn blend. Subsequently, a density could be calculated for comparison with the measured density. Assuming that the void is conical in shape with a base area (Acone) given by... 

The forces are proportional to the lateral surface area of fibrils and microfibrils. Since they increase with better, more perfect contact of adjacent elements, one would expect a higher resistance to the displacemnt of microfibrils than to that of fibrils. Microfibrils do not vary much in their draw ratio they are packed more closely, and to some extent they are connected by inter-fibrillar tie molecules. Fibrils vary much more in their draw ratio and in their outer boundary there are a great many structural defects caused by the irregular ends of microfibrils. 

The ribbon was placed between two split billet halves of the same polyethylene, and the assembly coextruded through conical brass dies which had an included entrance angle of 20 and nominal extrusion draw ratios, EDR, of 12, 25, and 30. No lubricant was used. The EDR calculated from the displacement of the line mark was in good agreement with the nominal EDR defined as the ratio of entrance to exit cross-sectional area of a die. The extruded films were used only for the evaluation of the effect of deformation components on the resultant morphology and properties. The semiperipheral coextrudates obtained simultaneously from the extruded assembly were used for the x-ray study of the deformation mechanism for extrusion drawing. 

Also a slight reduction in the area ratio is observed. Apparently the boiling water causes some contraction and perhaps even fusion of the fibrils. As the draw ratio is increased to 5x, the structure becomes finer with the fibril diameter decreasing and the number of microvoids... 

Fig. 9. Surface replica eiectron micrograph and small-angte electron dffraction pattern of polyethylene film drawn at 60°C to a draw ratio 16 and subsequently annealed for 2 h at 120°C. Etched for 6 h in fuming nitric acid at 80° C. The transformed areas belong to fibrils of lower draw ratio than the rest (Peterlin and...

In the HYSYS.Plant simulator, this is accomplished by the Adjust operation, in CHEM-CAD by the CONT subroutine, and in PRO/II by the CONTROLLER subroutine. In ASPEN PLUS, the equivalent is accomplished with so-called design specifications. The latter terminology is intended to draw a distinction between simulation calculations, where the equipment parameters and feed stream variables are specified, and design calculations, where the desired properties of the product stream (e.g., temperature, composition, flow rate) are specified and the equipment parameters (area, reflux ratio, etc.) and feed stream variables are calculated. In HYSYS.Plant, the Adjust operation is used to adjust the equipment parameters and some feed stream variables to meet the specifications of the stream variables. Furthermore, the Set object is used to adjust the value of an attribute of a stream in proportion to that of another stream. 

The alchite fibres showed much increased water and saline solution retention capabilities. There was however, no linear relationship between absorbency and increasing draw ratio. The increased absorbency can be attribtded to greater surtoce area i.e. huger diameter and the presence of the chitosan component... 

Draw ratio n. (1) A measure of the degree of stretching during the orientation of a fiber or filament, expressed as the ratio of the cross-sectional area of the undrawn material to that of the drawn material. (2) In monofilament manufacture, the filament is wrapped several times around a vertical, driven roll, passed through a warming oven, then wrapped again around a second roll running faster than the first one. In this way the filament is stretched and... 

Application area Quality requirement Draw ratio Dimensions mechanical properties mm. (dtex)... 

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