Length-diameter Ratio And Compression Ratio Affecting Plasticizing Quality Of Bimetal Screw Barrel

Length-diameter Ratio and Compression Ratio Affecting Plasticizing Quality of Bimetal Screw Barrel

 

In the production of bimetal screw barrel, the main factors affecting the plasticizing quality are: length-diameter ratio, compression ratio, back pressure, screw speed, barrel heating temperature, etc. Today we introduce the aspect ratio and compression ratio.

 

1. Length-diameter ratio: the ratio of the effective working length of screw to the diameter of screw.

A. Eating is easy to be even if the ratio of length to diameter is large.

B. Plastics with better thermal stability can use longer screw to improve mixability without burning. Plastics with worse thermal stability can use shorter screw or screw end without screw thread. Considering the characteristics of plastics, the general flow length is as follows: thermosetting 14 16, rigid PVC, high viscosity PU and other thermal sensitivity 17 18, plastics 18 22, PC, POM and other high temperature stability plastics 22 24.

 

2. Compression ratio: the ratio of the last groove depth in the feeding section to the first groove depth in the metering section.

A. Considering the effects of compressibility, filling degree and reflux, the products should be compact, heat transfer and exhaust.

B. Proper compression ratio can increase the density of plastics, make the bonding between molecules more closely, help to reduce the absorption of air, reduce the temperature rise caused by pressure, and affect the difference of output, inappropriate compression ratio will destroy the physical properties of plastics;

C. The higher the compression ratio, the higher the temperature rise of plastics in the process of plasticizing in the feeding tube, the better the mixing uniformity of plastics in plasticizing, and the relative amount of material discharged is greatly reduced.

D. High compression ratio is suitable for non-fusible plastics, especially for plastics with low melting viscosity and thermal stability; Low compression ratio is suitable for fusible plastics, especially for plastics with high melting viscosity and thermal sensitivity. Bimetal screw barrel