Segmentation of Threaded Element Combinations of Extruders and Their Functions

Time:2021-11-15

 

Segmentation of Threaded Element Combinations of Extruders and Their Functions

(1) The combination of screw elements of the extruder is generally divided into 5 sections: conveying section, melting section, mixing section, exhaust section and homogenization section.

1. Conveying section, conveying materials to prevent overflow. Threaded element thread sleeve

2, melting section, this section through heat transfer and friction shear, so that the material fully melted and homogenized.

3, mixing section, so that the material component size further refined and uniform, forming an ideal structure, with distribution and dispersion mixing function. Thread block kneading block

4. Exhaust section, discharge water vapor, low molecular weight substances and other impurities.

5. Homogenization (metering) section, conveying and pressurizing, establishing a certain pressure, so that the material at the die has a certain density, and at the same time further mixing, and finally achieve the purpose of smooth extrusion granulation.

(2) The period of distribution (distribution) and dispersion mixing.

1. The threaded components of the extruder are distributed and mixed to divide and recombine the melt and make the components evenly distributed in space, which is mainly realized by replacing the flow under the action of stresses such as separation, stretching (alternating compression and expansion), distortion, and reorientation of fluid activities.

2. Dispersion and mixing, breaking the components into particles or making the size of the incompatible two-component dispersed phase reach the required range, mainly by the shearing pressure and stretching stress of the kneading block.

Extruder Threaded Element Conveying Element-Threaded Sleeve

Thread sleeve representation: for example, "56/56" conveying block, the former "56" guiding course is 56MM, and the latter "56" refers to the length of 56MM.

Large lead, referring to a pitch of 1.5D ~ 2D

Small lead refers to a pitch of about 0.4D.

The use rule of the thread sleeve of the thread element of the extruder: with the increase of the lead, the extrusion amount of the screw increases, the residence time of the material decreases, and the mixing effect decreases.

A, choose large lead thread occasions, mainly to transport occasions, conducive to improve production; heat sensitive polymer, shorten the residence time, reduce degradation; exhaust, selection (also choose shallow groove), increase the surface area, conducive to exhaust, volatilization, etc.

B, choose the lead thread occasions, mainly mixed occasions, with different working sections gradually reduced combination, used for transportation and pressurization.

C, select the occasion with small lead thread, for the general combination is gradually reduced, thread sleeve for conveying section and homogenization metering section, play a pressurization, improve melting.

 

Keywords: Segmentation of Threaded Element Combinations of Extruders and Their Functions

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