Prefabricated unitary package which when sealed and irradiated conforms closely to contents and becomes impact-absorbing

A prefabricated unitary protective package for articles, comprising:

• an inner wall adapted to conform to the shapes of such articles and comprising the following layers:
• a first layer of polyethylene film, a layer of aluminum foil, a second layer of polyethylene film, a layer of flexible material suitable for packaging, and a third layer of polyethylene film;
• an outer wall permanently presealed to the inner wall about the mutual peripheries of the two walls, at manufacture, defining a permanently presealed chamber between the outer and inner walls, said outer wall comprising a layer of polyethylene film and a flexible covering layer of material suitable for packaging;
• and
• presealed in the chamber between the inner and outer walls a quantity of expandable polystyrene beads with incorporated blowing agent, and a quantity of water and surfactant.

A method of packaging an article, comprising the steps of:

• placing such article in a prefabricated doublewalled container having a quantity of expandable polymer permanently presealed within the double wall;
• sealing the mouth of the container;
• and
• placing the container with such article sealed therein in a radio-frequency electric field to expand the polymer.