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what is the function of screw combination?

Jan 24, 2018

1. Delivery of materials

(1) supply shear - the energy required to make the processed material get physical changes and chemical changes to disperse and distribute the components between the components.

(2) pressure build-up

Analysis of the melting process of material particles:

Polymer free transport and preheating -- filled or partially filled with Solid Plugs -- solid friction, dissipation and solid state "island" structure generation -- solid state sparse island structure extrusion molding.

2, the influence of screw speed

The higher the speed is, the larger the shear is, and the dispersed phase is uniformly dispersed in the matrix. The larger the shear, the smaller the size of the dispersed phase is, but the larger the speed is, the greater the friction is, which leads to the thermal degradation. Meanwhile, the residence time becomes shorter and the mixing is uneven.

The lower the rotational speed, the smaller the shear, the inhomogeneous dispersion, and the long stay, which are unfavorable to the easily decomposed polymers.

Both the rotational speed and the screw structure are related to the shear dispersion, so they must be considered as a whole.

3, material factors

The fibre reinforced type,

The influence of the length and diameter of glass fiber affects the dispersion of the resin and glass fiber, thus affecting the enhancement effect.

The type of alloy,

It is necessary to consider the problem of the formation and destruction of the structure between the resin by the rotational speed shear. Such as PC/ABS alloy, belongs to a sponge like "island" structure.

The flame retardant,

It must be considered that the thermal properties of the flame retardants, such as melting heat and heat release, thermal degradation and thermal oxidation are difficult。

From: screw elements -www.kalshine.com