The underside of your carpet separating from the top is a common occurrence in fairly new, as well as older carpets, and especially those exposed to heavy wear or chemical action.
Your carpet is actually like a triple-decker sandwich. The topmost layer is the face yarn, which is held firmly in place because it is tufted or sewn into the middle layer or "primary" backing. The third layer of fabric, which rests against the floor, is called the "secondary" backing. The two backings are "glued" together by a thin layer of latex, which is a type of rubber cement...
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