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Name: Jackson
Status: student
Grade: 6-8
Location: NY



Question:
How can glue stick things together?


Replies:
Jackson,

There are many variants of glue and there are some slight differences in the details of how they work, so I will just talk about how glues work in general. The first requirement is that glues must be able to creep or flow into the crevices of the two objects that are being attached together. At the microscopic level, even surfaces that appear smooth will, in general, be very rough - full of mountains and valleys and crevices. The glue has to be able to seep into these crevices. The second requirement is that the glue must be able to change its molecular structure so that it changes from a fluid to a solid - it must harden. There are many ways this can be achieved. Reaction with atmospheric oxygen, addition of a cross-linker, thermosetting (hardening due to an application of heat), etc. All of these processes have the result of making the glue harden or cure.

So, what we can imagine then, is that the glue, as a fluid will seep into the microscopic cracks and crevices of the two objects that are being attached together. Then, through some predetermined mechanism, the glue hardens or cures. The result is that the parts of the glue that have seeped into the objects at the microscopic level are like anchors and hold onto the objects. The hardening prevents those anchors from getting dislodged and also makes the glue a hard object to break.

Greg (Roberto Gregorius)



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