Canning and Fish Packaging Technology

Unit 12 - Additives in plastics

12.1.8.Foaming agents
Expanded polystyrene and polyethylene sheets are manufactured using foaming agents.
Production of cellular PE and PP sheets for example in achieved by adding a foaming agent to the granules and then extruding as usual. The farming agent that breaks down at a temperature of extrusion to give out nitrogen or CO2, which expands the molten mass when extruded. Foaming agents used include mixtures of nitrogen compounds such as azo dicarbamide. In this instance the residues are largely volatile and disappear.