SILICONE PRIMARY JACKET EXTRUSION
Outstanding temperature resistance.
We take pride in offering all Silicone Rubber thermoset manufacturing processes and technologies. With in-house compound formulation, combined with a broad equipment spectrum, we provide our customers with a “one-stop shop” solution when it comes to thermoset materials for critical applications.
LOROM offers technologies in Thermoset material science and processes:
- Microwave Curing/ Vulcanization
- Salt Bath Curing/ Vulcanization
- High Pressure Steam Curing/ Vulcanization
- Hot Air Curing/ Vulcanization
Each technology platform has its own advantages and features to match the properties required by critical applications.
Our silicone cables are suitable for demanding applications, ranging from ignition cables to jacketed cables with optional steel wire armoring protection.
In high end applications such as:
- Oven, coal plants, foundries, heating appliances, smelters
- Steelworks, hot-rolling mills
- Lighting fixtures and illumination
- Marine and offshore
- Aerospace and military
- Cement fabrication equipment, glass and ceramic factories
- Bakeries, oil burners, solariums, saunas, coolers
- Air-conditioning, electronic motors, medical applications and power generation plants
Our performance criteria that all applications have in common is:
- Outstanding heat and cold resistance
In some cases we are using additives (polar material) with the virgin rubber compound, such as nitrile or chloroprene polymers. Polyethylene glycol, for example, can also be added to obtain this effect. This curing method is primarily used for thick walled products, which take a long time to cure when using other methods.
Clean handling processes eliminating contamination is crucial. If there are pollutants present in the rubber compound, such as metal filings or poorly distributed carbon black, so-called hot spots may occur. These could get so hot that they ignite the rubber profile while it is being produced. The modern microwave curing method is a great alternative to compared salt bath curing, as microwave curing represents less environmental hazards.
Salt Bath Curing
In the salt bath curing method, the insulated product is directly transported via a conveyor belt down into a series of containers with a bath of liquid salts. At LOROM we vary the width and depth of the tank depending on the size of the products to be manufactured. In our modern production facility we can optimize the process for lower cost by changing the processing speeds and changing the in-house curing equipment dimensions.
We use a salt mixture, which comprises of a blend of sodium nitrite and potassium nitrate with modifications of the other necessary additives to enhance production speed or final product performance.
During extrusion the salt bath is heated by tightly controlled heating elements to a temperature between 180°C and 240°C and the product is submerged in the salt solution for curing.
After the curing by the salt bath method, the salt must be washed off and the products must be cooled. Finally the finished product is wound up.
Advantages of using salt bath curing:
- Very fast heat transmission
- Increased line speed
- Lower Cost
LOROM is at the forefront of environmental protection and we are cleaning and disposing of potential toxic substances such as sodium nitrite to protect the environment.
Our internal stringent requirements exceed all national and international standards and we are recycling on site by purification methods. In many cases we are using a salt where the sodium nitrite is replaced by lithium nitrate.
The basic principle of Microwave Curing of Silicone is the same as that used in an ordinary household microwave oven.
After the product leaves the extrusion head, magnetrons transmit radio waves with a frequency of 2450 MHz, which cause an oscillation and polarization of the molecular structures in the material, creating movements of the molecules resulting in a production of heat.
The magnetrons in the curing equipment are located in a tunnel, which the silicone rubber profile passes through on a conveyor belt. The heat build-up, which takes place here, must then be maintained in a long hot-air tunnel where the actual curing process takes place. The air temperature in the tunnel is over 200°C. While travelling through the tunnel the microwaves are precisely controlled by various process parameters controlling the depth of penetration from millimeters to a few centimeters, depending on product and application.
Cooling and wind-up then take place in the same way as for other curing methods. In order to make heating with microwaves possible, the rubber material must be electrically conductive and have polar molecular structures.