The shear rate range of polymer depend on many factors.Can we improve the quality of product by changing this range.
I think the shear range does not affect the product quality so much
There may be a high shear rate in polymers. However, whenever this rate is low, many problems can be avoided during the manufacturing process, which in turn affects the final product
For example operation such as extrusion and injection molding typically involve high shear rates.This may show many problems in the final product such as swelling and Shrinkage..
finished part quality is often controlled by the low shear rate behavior
Shear rate effect on the final product when the shear rate is high these causes many defects on product also if it very low so he effect on products. We can controll on his quality by using property quality and it preferred using low shear rate
the extrusion is conducted under different flow rates and temperatures to evaluate the extrusion parameters impact on the final texture of the confectionary product . when shear rate is high or law these causes many problems on product.
high shear rate causes high flow rate and this causes swelling in products .with alonger die and slower polyumer flow rate ,less pronounced die swell will be observed.
polymer shear rate is effect on the final product , and must choose shear rate proportion to the viscosity of polymer ,so when it is very high or very low wil be the product contains the defect (for example ;swelling and shrinkage)
In extrusion process, die system cause a problem which is that the polymer moves very freely so it gets swelling. The hight shear rate reduces viscosity and increases the movement of chains. Therefore, we try to make the sheer rate suitable with the viscosity of material so as not to cause swelling and facilitate flow
If we increase the rate of shearing (i.e., extrude faster through a die), the viscosity becomes smaller, This reduction of viscosity is due to molecular alignments and disentanglements of the long polymer chains. The higher the shear rate, the easier it is to force polymers to flow through dies and process equipment. During single-screw extrusion, shear rates may reach 200 s–1 in the screw channel near the barrel wall, and much higher between the flight tips and the barrel. At the lip of the die the shear rate can be as high as 1000 s–1. Low shear rate on a die wall implies slow movement of the polymer melt over the metal surface. Some die designers try to design dies for cast film or blown film operations not having wall shear rates less than, say 10 s–1, to prevent potential hang-ups of the molten material.
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