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PU type crystal adhesive

PU type crystal adhesive
It is also composed of two components, one of which is a polyol (including additives) and the other is an isocyanate. Polyurethane type crystal glue is more than epoxy type crystal glue used in products, from the appearance may be difficult to distinguish at the moment, but with the passage of time, the essence of the two differences will appear. According to the test of PU adhesive, the results are as follows.
(1) UV resistance, aging test
Under ultraviolet irradiation, the ambient temperature is /,0, and the longitude is +12, the sample does not turn yellow.
(2) temperature test
In the low temperature environment of minus 30 degrees, after thawing, it can quickly return to the original performance; Soften slightly at + 50 ° C.
(3) salt water test
Soak in salt water! +2, increase in mass, +43, increase in length,13.
(4) gasoline test
Put in (unleaded gasoline! +2, mass increase!! 3, the length increases (3).

The performance of PU adhesive is superior to that of epoxy adhesive, but it also has some shortcomings.
PU adhesive is very sensitive to moisture and has strong hygroscopicity. Therefore, it has strict requirements on the operating environment, including temperature!! 0, the relative humidity is not greater than /,3 in a dust-free environment.
The gel time of PU glue is short, so it is generally suitable to adopt the glue drip machine with automatic mixing, vacuum defoaming and automatic drip. The operation performance of PU glue can meet the requirements of manual drip, but the requirements of the environment cannot be changed.
Polyols in PU adhesive not only have hygroscopicity, but also can be dissolved in large amount of carbon dioxide. Isocyanate has very high reactivity and is easily spoiled by the invasion of moisture in the air, so the storage process of PU adhesive must be sealed with nitrogen.