Cord dipping
Several synthetic fibres have a very smooth and slippery surface, and the adherence of rubber on it is poor. Therefore they require special treatment.
The first phase of cord treatment is cord dipping in a special impregnating liquid that pushes around every wire and enables rubber adherence at a later stage. On this phase the fibre is carefully dried, because moisture prevents rubber adherence. After the dipping phase the fibre is protected from moisture by putting it inside plastic sheeting, if processing does not continue immediately.
Cord calendering
Preferably immediately after dipping is done cord calendering: it is coated with a thin layer of rubber on the both sides of the fibre.
In calender it is possible to regulate the thickness of rubber layer, speed etc. The machine is automated, because calendering needs to be made with great accuracy. Automatic measuring is based on nuclear radiation. It controls the thickness of the rubber and regulates the distance of the rolls according to this. One important factor in this phase is temperature. Rubber calendering in the textile causes temperature rise, which needs to be eliminated with an appropriate cooling system to prevent vulcanization of the rubber.
Process control is centralized and functions automatically. Dipped cord is winded between a fabric. Otherwise the cords would stick to each other.
Steel cord calendering
The wire coils are appropriate into use as such. Wire coils are set on racks in a separate wire room. Temperature and humidity in this room are kept constant. From the racks the wires are collected as a fan and then directed through a reed blade that spreads the wires as a steel mat. Steel cord mat is directed through the cylinders of a calender and it gets rubber on both sides. Finished steel cord is reeled between plastics and taken to intermediate depot to wait for further handling.
In this phase the speed of the calender and the temperature of the rubber has to be kept within certain limits. Otherwise the finished steel cord may turn grey and its adherence deteriorates.
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