Envelopes are made from paper and glue, and often have plastic address panes. Padded envelopes are made with thicker paper and then padded with plastic and/or other filler materials such as shredded paper or plastic.
Plastic windows are not normally a problem for paper mills as the window can usually be easily screened out during the manufacturing process.
It is very rare for padded envelopes (often know through their trade name Jiffy Bags) to be accepted for recycling as they are a “composite material”. In other words they are made up of more than one thing – paper, plastics and other filler materials. In deciding on whether or not the padded envelope can be recycled firstly check to see if it contains any printed recycling symbols. Failing that, take a look inside. Does it contain plastic bubble wrapping? If so, sadly it will probably need to be disposed of in your normal waste collection. Some padded envelopes may be padded with a paper lining and padding. These can be recycled the same way as other paper products.