This International Standard specifies a method for determining the gel time of phenolic resins at a given temperature, using automatic apparatus under specified conditions. The test temperatures are 100 oC, 130 oC and 150 oC.
The method specified employs a plunger driven to carry out a reciprocating vertical motion.
This method applies to the following types of phenolic resin:
- liquid resols
- solid resols with low melting points
Powdered resins with a short gel time, such as mixtures of novolak and hexamethylenetetramine, do not lend themselves to this type of determination. Such resins crosslink as soon as fusion starts and become too viscous in the test tube to give meaningful results. Resins containing large amounts of a solvent with a low boiling point are especially unsuitable for this type of determination. With such resins, a boiling and distillation process takes place as the resin hardens.
It might be of interest to determine the time taken for the resin to gel in the presence of a catalyst. The catalyst shall be added in well defined proportions. The type of catalyst used and its treatment shall be stated in the test report.