Behavior of urea-formaldehyde wood adhesives during early stages of cure

The cure properties of an adhesive play a crucial role in determining appropriate processing schedules for the manufacture of wood composites. During a recent study of a thermosetting adhesive using a torsional braid analysis technique, several instances of noncontinuous cure behavior were observed. This paper describes results for a urea- formaldehyde adhesive, where rigidity development curves consistently show a two-stage cure taking place under varying heating conditions. During the initial cure stage, a limited rigidity increase is observed in the polymer. This is followed by a rigidity decrease before the rapid development of final, high rigidity in the second cure stage. The adhesive remains thermoplastic until final cure is achieved. This cure behavior appears related to previously reported strength development anomalies found during the pressing of particleboard.

You must be logged in to download any documents. Please login (login accounts are free) or learn how to Become a Member