Biaxially oriented blow-molded pressure vessels

A method of manufacturing a pressure vessel comprising:

• heating a preform formed of a thermoplastic polymer to thereby obtain a heated preform;
• inserting a blow pin assembly into an opening of the heated preform, wherein the blow pin assembly includes a bung portion and a plunger portion that extends through the bung portion;
• clamping the heated preform between the bung portion of the blow pin assembly and sections of a blow mold;
• extending the plunger portion of the blow pin assembly into an interior of the heated preform from a first retracted position to a second extended position to stretch the heated preform in the blow mold and thereby obtain a stretched preform;
• and
• blowing air into the stretched preform under pressure to form the pressure vessel such that:
• (a) the pressure vessel comprises a tank having a neck portion, a cylindrical body portion having a diameter of at least about 200 mm, and a bottom portion,
• (b) at least the thermoplastic polymer in the cylindrical body portion of the pressure vessel is biaxially oriented, and
• (c) threads are formed in the neck portion of the pressure vessel,
• wherein:
• the plunger portion includes a hollow extension rod and a hollow distributor head that collectively define a delivery pathway through which the air is blown into the interior of the preform under pressure;
• the distributor head has a diameter larger than a diameter of the extension rod;
• and
• the distributor head includes apertures through which the air exits the delivery pathway and is blown into the interior of the preform under pressure.