Method for blow forming a container made of plastic and for coating the inside of said container

The invention relates to a method for blow forming a container (1) from a parison (2) made of plastic. After heating, said container is preformed by a gas injected into the container (1, 2) at a low pressure of 5 bar and by expanding the inner volume of said container. The final shape of the container can then be achieved by igniting an inflammable gas injected into the container, whereby the combustion generates a higher blowing pressure, or by injecting an additional gas with a higher blowing pressure of approximately 40 bar into the container after pre-blowing. The invention aims at improving known blow forming methods in such a way that a barrier layer impervious to gases, aromatic substances or the like is produced on the inner side of the container without having to use big machines. To this end, a precursor gas is added to and mixed with the inflammable gas, the mixture is then ignited and a coating is formed on the inner surface of the container by the combustion. Alternatively, an inflammable precursor gas is injected into the shaped, stress-relieved container that has been formed by means of classical stretch blow forming. Said gas is then ignited and once again the coating is formed on the inner surface of the precursor gas by the combustion.