Made an order for 2 pajama sets. Order arrived I took just one shirt and noticed an item "squeaks" in my hands and made statics. Emailed, they ignored questions about fabric composition. Called, they asked for time to double check with another department. I got a response "Even though silk can sometimes generate static electricity when in contact with certain skins, our pyjamas are made from 100% silk."
I think it is silk with polyester or what's called "Armani silk", made of pure polyester. Statics happen because of the composition, statics caused by friction between two different materials. Meaning that it should be used more than one fiber type in that fabric.