Common problems and solutions in TPE extrusion processing

Jun 28, 2024

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Common problems and solutions in TPE extrusion processing:

1. The surface of the formed product is rough

The surface of the formed product is not smooth and has a rough (pitted surface) state, usually caused by poor plasticization. As a countermeasure, it goes without saying to choose a suitable molding machine, but optimizing the molding conditions such as setting temperature, screw speed, and type of filter screen is also very important. In addition, the use of high temperature and fine mesh (filter) methods can also improve the plasticization efficiency.

In thermoplastic elastomer TPE, some grades already contain a large amount of moisture absorbing components or fillers, so it is necessary to dry them before molding. When forming without drying, problems such as foaming and rough surface may occur.

2. Scaling

Scaling is the sediment that accumulates at the edge of the mouth during extrusion molding, and its components are either from the extruded material or from special additives. As a countermeasure, reducing the amount of lubricant can effectively improve the characteristics of the material, as excessive addition of lubricant itself is one of the factors that cause scaling. The method of applying Teflon to the mouth shape can also reduce the formation of scaling. Additionally, damp materials should be avoided.

3. Unstable extrusion volume

The fluctuation of extrusion volume is an unstable phenomenon. The fluctuation of melting point in the screw feeding or compression part is the main reason for instability, and the magnitude and cycle of extrusion fluctuation are irregular. These phenomena can be attributed to the unsuitable shape and extrusion conditions of the screw for the material, so it is necessary to adjust the extrusion conditions and replace screws with different shapes.

In the case of large temperature fluctuations in the extruder, the instability of material flow in the extruder is also one of the reasons for this problem. In addition, slippage between the screw and the granular material at the feeding position can also lead to unstable extrusion. By using a hopper dryer to preheat the granular material, the temperature of the lower barrel of the hopper can be improved.

4. Deformation

The extrusion molding of TPE is usually done from the mouth shape and cooled through a water tank. If the formed product cannot be uniformly cooled at this time, it is extremely prone to deformation. Especially for molded products with complex shapes and high dimensional accuracy requirements, it is necessary to use cooling calibration or detection devices. In addition, deformation is also prone to occur during the multi-layer extrusion process due to the different shrinkage rates of the composite materials.

5. Stripes

Extruded products sometimes have striped scars or marks in the same area. At this point, it is necessary to check or confirm whether there are any signs of damage, dirt, scaling, etc. on the mouth shape. Secondly, cleaning or eliminating uncleanness during material replacement is also one of the reasons for this problem. In addition, poor material melting at the junction of the mouth shape can also easily lead to the occurrence of stripe phenomenon.

The common problems and solutions related to TPE extrusion processing mentioned above have been shared with everyone here. The production and processing abnormalities that usually occur can be checked, adjusted, and eliminated by adjusting process parameters. Some abnormalities can also be solved from the perspective of TPE raw materials.