Additives endothermic blowing agents

Endothermal blowing agents require energy for decomposition and gas release therefore stops quickly after the supply of heat is terminated. Shorter cooling periods are needed and moulding cycles are therefore shorter. The base materials are bicarbonate and citric acid - which are also used as food additives, and present no handling problems. 

However, an important consideration with the chemical types is that in addition to an exotherm resulting from the chemical breakdown of the compoimd, unless steps are taken to seal the system there will also bean endotherm due to the hberation of the gas. This loss of heat from the system will cancel out some of the exotherm and interfere with the data. The use of high-pressure, sealed pans is therefore very important in studies involving chemical blowing agents as these ensure that no volatiles can escape during the analysis. 

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