Mechanism of thermal degradation of urea-formaldehyde polycondensates |
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Authors: | G Camino L Operti L Trossarelli |
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Institution: | Istituto di Chimica Macromolecolare dell''Università, Via G. Bidone, 36-10125 Turin, Italy |
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Abstract: | The thermal degradation to 500°C of urea-formaldehyde polycondensate occurs in four successive steps. In each step, partial volatilisation takes place while the polymer undergoes chemical modification to give progressively more stable structures.Below 200°C methylene ether bridges are transformed into methylene bridges and branching and crosslinking reactions occur with maximum rates at 125°C and 165°C, respectively. Above 200°C radicals formed by chain scission induce the formation of cyclic structures in the polymer which undergoes extensive fragmentation above 300°C. Water, formaldehyde, carbon monoxide and dioxide, methane, ammonia, monomethylamine and trimethylamine are the gaseous products evolved.By combining data on the chemical modifications and gases evolved in each step, reaction mechanisms are proposed. |
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