The regular white glue most people know so well is made up of a variety of chemicals called polymers. These polymers are long strands that are either sticky or stretchy.
大多数人都非常了解的普通白胶是由多种称为聚合物的化学物质组成的。 这些聚合物是粘的或有弹性的长链。
Glue manufacturers have to find just the right combination of sticky and stretchy polymers to make the best glue.
胶水制造商必须找到粘性和弹性聚合物的正确组合方式，才能制成最好的胶水。
White glue also contains water. Water acts as a solvent that keeps the glue liquid until you want it to stick.
白胶还含有水。 水起溶剂的作用，使胶水保持液态直到粘住为止。
When you put glue on a piece of paper, the solvent — water — is exposed to air. The water eventually evaporates (changes from a liquid to a gas). As the water evaporates, the glue dries and hardens.
将胶水粘在一张纸上时，溶剂（水）会暴露在空气中。 水最终会蒸发（从液体变为气体）。 随着水的蒸发，胶水会变得干燥，然后硬化。
All that's left are the sticky polymers that hold things together. This process is called mechanical adhesion.
剩下的就是将东西粘合在一起的粘性聚合物。 该过程称为机械粘附力。
So why doesn't white glue stick to the inside of the bottle?
那么为什么白胶不粘在装胶水的瓶子内部呢？
When white glue is inside a bottle, there's not enough air inside the bottle to cause the water to evaporate to make the glue sticky.
当瓶子内有胶水时，瓶子内的空气不足以导致水蒸发，胶水不粘。
Basically, the bottle protects the glue from the air and keeps the glue runny.
基本上，瓶子可以保护空气接触胶水并保持胶水流动，成液体状态。
If you've ever left the top off a glue bottle for a while, you may have noticed that, unfortunately, the glue dried up!
如果你曾经忘了将瓶子盖住，放上一段时间，可能你会发现，胶水干了！
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