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What Is The Role Of The Kneading Block In The Block Screw Combination?

Feb 10, 2018


Filling and modifying other polymers or additives in polymers to change their mechanical properties, processability, performance and cost reduction. Filling modifier in the filling modification can play a variety of roles: increment, enhancement, and function, in which the increment is the main.

(1) increments are added to the polymer by adding cheap filling agents to reduce costs and save raw materials.

Its main role is the increment, so the filling agent at this time also called the increment agent.

(2) the reinforcing filler can improve the mechanical and thermal properties of the polymer, and the effect is very great.

It depends on the physical properties of the packing.

(3) the functional packing can be endowed with some special functions that the polymer does not have, and the chemical composition of the filler often plays an important role.

Most of the mixtures filled with granular filler are similar to those in polymer blends. They have a continuous phase structure, and the filler is dispersed phase (only a smaller particle size), while polymer is a continuous phase. There is an interface layer between the continuous phase and the dispersed phase, and the two phases are combined through the interface layer. The bonding effect of the interface layer is different because of the properties of the resin and the properties of the filler.

The dispersing state of the filler in the polymer has a great influence on the properties of the filled modified polymer, especially the mechanical strength. If the filler is distributed uniformly in the polymer with small and even particle size, it will make the filled polymer have good mechanical properties and product dimensional stability. On the contrary, the mechanical properties of the filled polymer will be poor if the size of the filler is very uneven, it is large and small, and the distribution of the polymer is not uniform. But the filler particles nor too small, because of fine particles to produce self condensation, not easily dispersed, can also cause the uneven dispersion effect, improve the mechanical strength of the. Nanomaterials used for filling and modification will meet this problem and must be solved, otherwise the effect of nanomaterials can not be played.

The dispersing state of the filler in the polymer is related to its surface activity and mixing process. If a good chemical combination between the filling agent and the resin can be realized, the filling effect will be greatly improved and the filling agent will be enhanced. The most effective way to achieve a good chemical combination is to use the coupling agent for the surface treatment of the filling agent and the reinforcing agent. The coupling agent used a silane coupling agent, titanate coupling agent and aluminate coupling agent.

A commonly used filler of calcium carbonate, carbon black, talc, wollastonite, red mud, fly ash, clay, mica and iron metal filler etc..

According to the characteristics of high filling and modification of plastic, the modified equipment must be adapted to its requirements. In the mid and late 1980s, China began to apply the parallel meshing twin screw extruder to the field of high filling and modification, and achieved good results.

The characteristics are as follows:

1. adaptable, one machine and multi use

That is, the same parallel twin screw extruder can produce a variety of products.

2. mixing effect is good

Screw intermeshing parallel twin-screw extruder to produce strong shearing action in meshing, material dispersion and mixing is favorable, due to the screw a screw like a wedge into the grooves of another screw, basically prevents the material from the channel into the adjacent channel with a screw in, most of the material by forcibly screw groove and a screw to screw groove screw to another. The material is repeatedly turned between the two screws, and the material is well mixed. Even if the melt viscosity of the polymer involved in the blend is quite different, it can be compensively mixed into a homogeneous polymer blends.

The working principle of the 3. materials in the barrel of the residence time distribution of narrow intermeshing parallel twin-screw extruder is "positive transfer" so the material in the mean residence time and the ratio of single screw extruder is less than 1/2, the residence time distribution range is only about 1/5 of single screw extruder. As a result, the physical changes of the material in the extruder barrel are generally the same. Therefore, the performance of polymer blends is more uniform.

4. good self-cleaning ability

From: Mixing Conveying Kneading Elements of Screw