PCB-free silicone compounds

Gummiwerk KRAIBURG’s PCB-free silicone compounds

Gummiwerk KRAIBURG offers chlorine-free silicone compounds, which do not release any polychlorinated biphenyl (PCB) during pressureless vulcanization. Thanks to the use of an alternative cross-linking method, the fission products of these compounds do not contain any PCB.  

Peroxide and addition cross-linked compound alternatives

The manufacture of extrusion articles by means of pressureless vulcanization (hot air, salt bath) of silicone rubber using the common peroxide DCLBP, Di(2,4-dichlorobenzoyl) peroxide, results in the release of polychlorinated biphenyl (PCB), which is harmful to both the environment and people’s health.  

The solution for reduced emissions during processing

Gummiwerk KRAIBURG offers peroxide and addition cross-linked compound alternatives containing chlorine-free cross-linking systems for pressureless cross-linking and which therefore do not form any PCBs. While these compounds do vulcanize somewhat slower, this is far from being a decisive factor in high-temperature vulcanization (200 °C or higher) in a hot-air tunnel. The time differences can be reduced so much by raising the temperature that the dwell times in the vulcanization tunnel are hardly that much longer in practice. The odor created during the processing of the peroxidically cross-linked DCLBP alternative can be eliminated using an extraction system integrated into the process.    

High level of mechanical quality of the addition cross-linked silicone compounds

Weiterhin zeigen die additionsvernetzten Alternativmischungen ein höheres mechanisches Niveau als The addition cross-linked alternative compounds also feature a higher level of mechanical quality than those cross-linked with peroxide. For instance, the elongation at break, e.g. of a standard compound 70 ShA, increases significantly, from 370% to 600%. Similarly, the tear strength increases from 25 N/mm to 42 N/mm according to ASTM D624B. This makes it possible to produce cables and hoses with even better tear resistance and extensibility. In addition, the better compression set of these compounds (24 hours at 175 °C from 33% to 10%) also makes increased pressure stresses possible.  

Stricter monitoring and switching to alternative solutions

Polychlorinated biphenyls accumulate in fatty tissue and damage the nerve and immune systems. In some cases, these substances also lead to cancer and malformations and deformities in unborn children. Quite recently, several manufacturers in the German state of North Rhine-Westphalia were forced to restrict their production activities after dangerous concentrations of PCB were detected in the areas around these facilities. This prompted the state government to impose stricter monitoring on companies processing silicone and encourage manufacturers to switch to alternative solutions.  

Amended regulation since April 2021

The state of North Rhine-Westphalia has submitted a recommendation in this matter to Germany’s federal states’ parliament, the Bundesrat to establish a uniform approach to be applied throughout Germany for preventing damage to the environment. The amendment to the Regulation on installations requiring a permit was decreed by the federal government at the beginning of 2021 and came into force uniformly throughout Germany on April 1st, 2021. As a result, plants which vulcanize natural and synthetic rubber using halogenated peroxides are included in annex 1 of the 4th BImSchV [Regulation on the implementation of the Federal Immissions Control Act], and will therefore be subject to approval under the Immissions Control Act in the future.  

About Gummiwerk KRAIBURG

Gummiwerk KRAIBURG GmbH & Co. KG is a company of KRAIBURG Holding GmbH & Co. KG and currently employs about 400 people. Gummiwerk KRAIBURG, a leading manufacturer of rubber and silicone compounds, has been developing and producing highly customized solutions for the demands of customers and markets for more than 70 years. KRAIBURG rubber and silicone compounds are used in the automotive sector, in machine construction, oil and gas production, the roller industry and by numerous other manufacturers of molded rubber components.  

Contact:

Gummiwerk KRAIBURG GmbH & Co. KG

Teplitzer Str. 20,

84478 Waldkraiburg, GERMANY

Mail: info@kraiburg-rubber-compounds.com  

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