Effect of DMDEE on PUR (polyurethane thermosol)

Effect of DMDEE on PUR (polyurethane thermosol)
Most PUR (hot melt adhesives) basically use a catalyst, DMDEE, with CAS No. 6425-39-4
Its dosage in the formula is very small, generally between 0.05% and 0.5%, but it plays a key role in promoting the reaction of isocyanate and water vapor, and accelerating the curing rate.
There are many kinds of polyurethane catalysts, so why use DMDEE?
That is because it can not only improve the curing rate of PUR, but also maintain good thermal stability, that is, it has a relatively slow viscosity growth rate at high temperature.
Compared with PUR without catalyst, most catalysts can accelerate the curing rate of PUR, and DMDEE is the most effective. The shear strength can be rapidly increased from 14 psi to 200 psi within 30 minutes, and the adhesive strength has reached the level of two days after curing for 1 hour.

In addition to the fastest curing rate, DMDEE has the best thermal storage stability. Under the heating condition of 120 ℃, the hourly viscosity growth rate of PUR evaluation of DMDEE system is only 3.1%, which is only 0.5% higher than the 2.6% growth rate of PUR of catalyst-free system. Other catalysts have a viscosity growth rate of at least 6.2% per hour.
In addition, although the amount of DMDEE is very small, slight fluctuations will cause great fluctuations in performance. It only needs to increase the content of DMDEE from 0.05% to 0.1%, and the shear strength will change suddenly after curing for 30min, 1hr and 1.5h.
At the same time, if you want to obtain a fast curing PUR, one of the effective and immediate methods is to increase the content of DMDEE. Only by increasing from 0.05% to 0.15%, you can obtain 290psi shear strength in 1.5 hours, which is basically equivalent to the strength of PUR curing.

However, excessive DMDEE content can easily reduce the thermal stability between batches, and may also cause bubbles in the cured adhesive.
In short, do not underestimate the low content of catalyst, which has a crucial impact on the comprehensive performance of PUR hot melt adhesive.