Ash forming elements in plastics and rubbers

Metals, alkali metals and halogens found in solid fuels cause various operational problems in boilers and furnaces: emissions, ash melting, ash deposition and corrosion. The role of ash-forming elements found in plastics have received little attention in the literature. All commercial plastics and rubbers, particularly polyvinyl chloride (PVC), polyethylene (PE), polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS) and polyurethane (PU) contain additives serving various functions. These additives may be utilized as catalysts, curing agents for rubbers, stabilizers, fillers, pigments and flame retardants. In many cases these compounds contain metal, halogen, sulfur and alkaline earth metal (i.e. magnesium, calcium and barium) atoms bonded to the structures of additive compounds. The usage levels of the additive compounds may be several percent of the weight of the polymer, leading to high elemental concentrations of metal, halogen, sulfur and alkaline earth metal. In this review paper, metals, halogens, sulfur and earth alkaline metal containing polymer additives and polymers most widely used are introduced separately. Starting from the evaluation of the chemical formula of the additive compound, going through its typical targets of use, and also estimating the concentration range of the elemental sulfur/metal/halogen present in the final polymer. The element concentrations of metal, halogen, sulfur and alkaline earth metal compounds vary significantly, ranging from several hundreds of mg/kg units up to several thousands of mg/kg in the polymer, depending on the application.