The resin will be heterogeneous: some molecules that make up it will be much more than others. This will negatively affect the quality of gluing, since large molecules give adhesive seam less durable than small. There are several ways to align the reaction rate.
one. In the first phase of condensation, acid is introduced into two doses.
2. Depending on the reactionary capacity of phenols, temperature conditions of condensation and time vary.
3. The amount of formaldehyde varies [introduced on the first and second condensation phase.
Delicular input of acid in the first phase of condensation leads to the fact that the most active isomers are less actively associated with formaldehyde. After the condensation of such an active isomer with one formaldehyde molecule occurs, its reactionary ability decreases sharply, approaching the reactionary ability of phenol.
The need to vary the temperature and time in the first and second phase of condensation is caused by the fact that the total phenols of various origin differ from each other in composition, and therefore in reactionary activity. Thus, the reactionary ability of the brown -angle phenols below the reactionary ability of the shale, therefore, the temperature regime for cooking resins from these phenols differs from the temperature regime of the cooking of resin from shale phenols.
The same difference in the composition, and therefore in reactionary ability, leads to the need to change the dosage of phenols. The ratio of formalin and phenol (two prayers per one) remains unchanged for all cases, but the amount of formalin, introduced on the first and second phases of condensation, changes depending on the activity of the initial total phenols.
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