- Endothermic blowing agent (heat is consumed during decomposition)
- Exothermic blowing agent (heat is set free during decomposition)
Effect
Endothermic blowing agents decompose into ammonia-free gas on heating. The pressure of gas reaches 8 - 10 bar maximum. With this process of decomposition heat is consumed so that the separation of gas is prohibited as soon as the addition of heat is finished. Therefore, there is practically no further blowing after processing and the finished parts can be lacquered without any intermediate storage.
In contrast to exothermic blowing agents the surfaces of finished parts show a lesser formation of streaks and they can be produced with shorter cooling times. Mould surfaces of low- alloyed steels can corrode in the long run.
With reaching the decomposition temperature exothermic blowing agents decompose spontaneously to partly corrosive gases like e. g. ammonia under strong development of heat. This additional amount of heat must be led off via the mould.
Once started the development of gas cannot be stopped or controlled any more; the blowing agent reacts autocatalytically. The gas pressure reaches about 12 - 15 bar.
This often leads to a post-expansion of the finished parts.
Therefore, before a further surface treatment (lacquer) can be effected it is recommended to store the material intermediately. In comparison to the endothermic blowing agents, the finished parts show an increased affection of streaks and require longer cooling times.
Compatibility
Our Masterbatches contain combinations of inter-balanced active substances and are based on semi-universal polymer carriers. Due to this fact, they are optimal for subsequent applications and suitable for almost all thermoplastics (except for PVC).
CORDUCELL blowing agent-Masterbatches and their application
Endothermic blowing agent-Masterbatches are available in different active substances concentrations. In addition, special blowing agents contain slip components in order to achieve an optimal foam structure in case of long floating ways or to ensure and a failure-free foaming:
- Prevention of shrinkage and sink marks
- Production of structural accurate measured foamed finished parts
- Production of wood-like surfaces
- Extrusion of foamed ribbons
- Density reduction (decrease of weight of finished parts)
Exothermic blowing agent-Masterbatches are offered for special applications such as extrusion of pipes and profiles.
Food contact approval
According to BfR, Directive 2002/72/EC, only endothermic CORDUCELL blowing agent-Masterbatches are admitted for food contact applications.
Detailed information are available on request.
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