The History Essays Timeline People Companies
Materials Processes

Processes

ABCDEFGHIJKLMNOPQRSTUVWXYZ

Bag Molding

A method of molding or bonding involving the application of fluid pressure, usually by means of air, steam, water or vacuum, to a flexible cover which, sometimes in conjunction with the rigid die, completely encloses the material to molded or bonded.   A flexible bag or mattress is employed to apply pressure uniformly over one surface of the laminate. A preform comprising a fibrous sheet impregnated an A- or B-stage resin is placed over or in a rigid mold forming one surface of the article.  The bag is applied to the other surface, then pressure is applied by vacuum, an autoclave, press or by inflating the bag.  Heat may be applied by steam in the autoclave, or through the rigid mold portion.  When an autoclave is the used the process is sometimes called autoclave molding.

Source: Whittington, Lloyd R.  Whittington's Dictionary of Plastics (Stamford, CT: Technomic, 1968).

 

Billow Forming

A variation of the thermoforming process, in which the hot plastic sheet is clamped in a frame and billowed upwards against a male plug or die as the plug or die descends into the frame.  The process is suitable for thin-walled containers with a high draw ration.

Source: Whittington, Lloyd R.  Whittington's Dictionary of Plastics (Stamford, CT: Technomic, 1968).

 

Blister Packaging

A methods of packaging articles in thermoformed “blister” or pouches shaped to more-or-less fit the contours of the article.  The preformed blisters, usually slightly oversized to provide ample room, are made of thermoplastics such as vinyls, polystyrene, or cellulosic plastics.  They are placed inverted in fixtures, loaded with the articles, then cards coated with an adhesive are applied and sealed to the flanges of the blisters by means of heat and pressure.

Source: Whittington, Lloyd R.  Whittington's Dictionary of Plastics (Stamford, CT: Technomic, 1968).

 

Blow Molding

A method of producing hollow plastic objects by stretching and hardening softened plastic material against a mold through the application of internal pressure, usually compressed air.  Most commonly, the process involves extruding a tube (parison) downward between the opened halves of a metal mold, closing the mold to pinch off and seal the parison at top and bottom, injecting air through a needle inserted through the parison wall, cooling the mass in contact with mold, opening the mold and removing the formed article. Many variations of the process exist. In the earliest use of the process, two sheets of cellulose nitrate were sued instead of a parison.  The parison is sometimes formed by injection molding, and sometimes is extruded in advance, cut into lengths and reheated when needed. [PE, LW]