Good question and one I really never thought of so I did some digging, here is what I found. (google)
The same piece of plastic can only be recycled about 2-3 times before its quality decreases to the point where it can no longer be used.
Additionally, each time plastic is recycled, additional virgin material is added to help “upgrade” its quality so that the recycled product has a fighting chance in the market against new, durable and fresh goods. So when you read the label “recycled material,” think twice about what the word “recycled” actually means in that context.