Blow ratio

PS or copolymers are used extensively in injection blow mol ding. Tough and cra2e-resistant PS containers have been made by multiaxiaHy oriented injection-molded parisons (238). This process permits the design of blow-molded objects with a high degree of controlled orientation, independent of blow ratio or shape. 

The blow ratio Is the ratio of the weight of the unfoamed composition to the weight of an equal volume of the foamed composition. The relationship between air content of a foam, the blow ratio and the foam density Is Illustrated for an unfoamed composition having a density of 1 g/cc in Table V. 

Table V. The Relationship of Blow Ratio to Foam Density...

A high blow ratio Is desired since this creates a large volume of foam with respect to the solids. This serves to minimize variation In dry solids add-on due to variances In knife setting or non-uniform pressure between the two horizontal pad rolls. However, the apparent viscosity of the foamed composition Is directly proportional to Its blow ratio (Figure 5) and the fabric weight and construction will dictate the best coating viscosity for that particular fabric. 

Figure 5. Viscosity and density of a foam as a function of the blow ratio (12)...

The volumetric add-on of foam can also be used to control the dry pick-up on the fabric when the application method Is knife coating, But for horizontal pad application, dry pickup Is best controlled by the blow ratio,... 

As shown In Table XIII, the blow ratio of the foamed dye liquor Is dictated by the face fiber weight of the carpet. 

Frothing agent produces high blow ratio microbubble foam with a proper balance of wetting penetration and stability... 

Blow molding grades of PA/PPE blends can be based either on PA-6 Dimension ) or PA-66 Noryl GTX). For PA-6/PPE blends, a melt temperature of 265-295°C (as for extrusion) is recommended. Mold temperature of 60°C and typical blow ratio of 2 to 3 are normally used. The PA-66 blends are compatibilized by addition of a PA-PPE copolymer. In the blends, PA constitutes the matrix phase in which particles of PPE are dispersed, playing a role of low density organic filler. A melt temperature of 278-288°C is recommended, with adapter and accumulator... 

Excessive melt temperature reduces the blow ratio and should be avoided. 

PE films are usually produced by the blown film extmsion method. The alternative method is sheet extrusion followed by passing through chilled rollers. Blown film is more economic biaxial orientation is introduced by the draw-off and blow ratios. Bubble stability is critical to the blown film process. Bubble stabihty is provided by the melt strength and rheological characteristics of the PE. Long... 

BR blow ratio (also see BUR) CAD compact audio disc... 

Various techniques are used to introduce air. It can enter through the extrusion die mandrel (as with most pipe lines. Chapter 3), through a blow pin over which the end of a parison has dropped (Fig. 4-1), or through blowing needles that pierce the parison. The wall distribution and thickness of the blown part are usually controlled by parison programming, the blow ratio, and part configuration. 

With either EBM or IBM, the requirement for a thermally controlled parison at the lowest heat increases the demand on internal pressure/vol-ume to ensure adequate movement or expansion of the parison in the transverse direction. It is possible that vacuum-aided stretch blowing can provide faster expansion rates of the parison and improve performance at the higher stretch-blow ratios. With PVC, PS, and other low shrink alloyed resins, the vacuum assist may need little or no pressure beyond one atmosphere. The function of vacuum (—14.7 psi) has the basic effect of — ( —14.7 psi)... 

Blow molding is a stretching process in that the material, which is first injection molded or extruded into a parison, is expanded to fill out the cavity. The ratio of the surface area of the expanded surface to that of its original surface is referred to as the blow ratio, which can be determined by... 

There are limits to how much the plastic can be stretched. For engineered parts, IV2 to 2 is a comfortable blow ratio with a maximum of 4 to 5 depending on the material. However, much greater blow ratios are used for blown bottles, particularly those stretch blown from injection-molded parisons in thermoplastic polyester. The lowest blow ratios are... 

Minimum draft 1° per side Recommended draft 2° per side (no texture) For each 0.001-in depth of texture 1° per side additional Increase draft as blow ratio increases ... 

Average Most radii will faU into this range. Use with average blow ratios. 0.060-0.200 (1.5-5.08)... 

Large Used on tanks, boxes, and other components where cross-sectional part thickness is large. Also used with aggressive blow ratio geometries to minimize polymer thinning. Over 0.200 (5.08)... 

If the projection is rectangular instead of roimd, a blow ratio of 1.0 is the recommended maximum. Then the relationship between the height (H2) of the projection and the dimension (D2) across the short side of the rectangle is H2 D2. In that case, the outside radius (OR) relationship becomes OR O.LD2 or OR > O.IH2. 

For round depressions, which are created by a male pin in the mold, larger blow ratios can be used. If the pin is to be stationary, the maximum recommended blow ratio is 2. Therefore, the relationship between the diameter (Dz) of the depression and its depth (Hz) is Dz 0.5Hz or Hz 2Dz- For retractable pins, the blow ratio can be increased to 3, resulting in Dz Hz/3 or Hz 3Dz. 

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