Formaldehyde transition, glass

Strong-Acid Catalysts, Novolak Resins. PhenoHc novolaks are thermoplastic resins having a molecular weight of 500—5000 and a glass-transition temperature, T, of 45—70°C. The phenol—formaldehyde reactions are carried to their energetic completion, allowing isolation of the resin ... 

Novolac resins are produced from an excess of phenol (F/P<1) to form linear polymers, as illustrated in structure 2, with molecular weights of 200-5000 and glass-transition temperatures of 45-70°C. In two-stage novolac systems cross-linking is accomplished by reaction with hexamethylenetetramine (hexa), which is prepared from formaldehyde and ammonia and may he considered a latent source of formaldehyde. 

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