7 facts about rubber extrusion process

Rubber Technology is the matter of dealing with the alteration of rubbers or elastomers into useful products, such as automobile tires and rubber mats etc. The materials include latex, natural rubber, synthetic rubber and other polymeric materials, such as thermoplastic elastomers. Rubber treated through such methods are components of a wide range of items.

Extruded rubber products will vary from mould rubber products depending upon the process where extruded parts are enforced through a die of the vital cross section under pressure of an extruder. Often extruded products are un-vulcanized before being extruded, leaving the rubber in a soft and flexible state post extrusion. If this is indeed the case, the complete extruded products will normally need to be vulcanized before they are rendered usable.

Following are the keen facts about the rubber extrusion process:

• The extrusion process begins with the un-vulcanized rubber compound being fed into the extruder.
• Next, the flutes of the revolving screw will begin to carry the rubber forward into the die, with an increase in pressure and temperature occurring as the material gets closer to the die itself.
• Once it reaches the die, the built up pressure forces the material through the openings, where it will consequently swell in various degrees based on the material compound and hardness. Because of this tendency towards swelling, many extruded parts require plus or minus tolerances on their cross sections.
• During the vulcanization, the extruded rubber will well or shrink in both its cross section and its length depending on the type of rubber compound used.
• After vulcanization, a length of rubber extrusion will tend to be reduced in dimension more in the centre of the length than in the ends.
• The extrusion die is a precise and specific tool made by cutting an opening shaped in the form of the finished rubber cross section desired through a blank of steel.
• Once in place, the rubber material will be forced through this die via the pressure that builds up from the revolving screw of the extruder.

Many rubber compounds will tend to swell when passing through the extrusion die, making them to experience an increase in dimensions. Thus, each die is made according to each specific part and material to ensure that all tolerances are met for the finished extruded rubber part.

The closer tolerance classes outlined below should not be specified unless required to do so by the final application and they should be limited to the critical dimensions. The closer tolerances demanded, the tighter the control must be exercised when the material is being extruded and hence the higher the cost sustained.

We, an Iso9001 licensed company in China, Star Seals Co. Ltd is well recognized as a leader in the manufacture of rubber and plastic products. Our products are extensively used in the fields of automotive, electronics, machinery and construction.