Due to the long chain structure and the flexibility of the molecular chain of Dalian hollow polymer, it is a relaxation process that the polymer is placed at a certain temperature and the macromolecule complex undergoes a series of intermediate state transition to the equilibrium state corresponding to the external force.
Because the relaxation time t* of polymer is very short near the high elastic state or viscous flow temperature, if the deformation time T 1 > t*, it can be obtained by formula (3). When the external force action time t = t 1, the deformation of polymer will be frozen down in a short time when it is cooled below the glass transition temperature or crystallization temperature.
This is the viscoelastic principle of hollow moulding. The compressed air blowing pipe inserted from the hole on the parting surface of the mould is fed into the compressed air to make the parison blow up and close to the wall of the mould. The forming of the injection blow moulding parison is to mould the parison on a metal pipe by injection moulding method, and the compressed air is injected into one end of the pipe.
There are microholes in the other end of the tube wall. Injection moulded parison is usually taken out after cooling. In the second stage of moulding, the mandrel and the parison are sent to the blow moulds rapidly. The opening of the compressed air valve consists of a set of fixed switching dies located at an appropriate distance under the extruder head, and two sets of moulds are also used.