Blowing agent Masterbatches
The ease of foaming…
Blowing agent Masterbatches for foaming of plastic articles and prevention of sink marks in the case of molded parts
Generally one distinguishes between physical and chemical blowing agents.
For the production of Blowing agent-Masterbatches the chemical blowing agents are more interesting, which due to their chemical structure decompose with the formation of gas above a certain temperature. Thereby one distinguishes between endothermic blowing agents (heat is consumed during decomposition) and exothermic blowing agents (heat is released during decomposition).
Endothermic blowing agents are releasing carbon dioxide gas under heat above approx. 140 °C. By this process of decomposition heat is consumed, so that the release of gas stops as soon as the addition of heat has finished. Therefore, there is practically no further blowing after processing and the finished parts e.g. 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. Mold surfaces out of low-alloyed steels can corrode by time.
Exothermic blowing agents decompose on reaching the decomposition temperature of approx. 170 °C 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 mold.
Once started the development of gas cannot be stopped or controlled anymore, the blowing agent reacts autocatalytic to the end, and this could lead to a post-expansion of the finished parts. Therefore, an interim storage of at least 72 hours is recommended before further surface treatment (e.g. lacquering). Compared to endothermic blowing agents, the finished parts show an increased affection of streaks and require longer cooling times
Blowing agent masterbatches and their application:
Endothermic Blowing agent-Masterbatches are available in different active substance concentrations. In addition, special blowing agent masterbatches contain slip agent components, in order to achieve an optimal foam structure in case of long floating ways or to ensure a trouble-free de-molding:
- Prevention of sink and hollow marks
- Production of dimensionally accurate foam structured finished parts
- Production of wood-like surfaces
- Extrusion of foamed ribbons
- Density reduction (decreased weight of finished parts)
- Foam nucleation with physical foaming
Exothermic Blowing agent-Masterbatches generate higher gas pressure and are offered for special applications such as e.g. extrusion of pipes and profiles.
Combi Masterbatches e.g. with additives are available as well.
Food contact: Only with endothermic blowing agent masterbatches – please ask for the appropriate documents (product information/food contact approval/declaration of compliance).