Urea-linked degradation

Thus, for glucose, the acid seems to slow down the more severe urea-linked degradation in the long early stage, whereas, for xylitol, urea stops the severe acid-catalyzed degradation in this period. 

Thermosets are heavily cross-linked polymers which are normally rigid and intractable. They consist of a dense three-dimensional molecular network and, like rubbers, degrade rather than melt on the application of heat. Common thermosetting polymers include phenol-formaldehyde or urea-formaldehyde resins and high-performance adhesives such as epoxy resins. 

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