In p>1845, Cybertron, a chemist who lived in Basel, a city in the northwest of Switzerland, accidentally came across concentrated sulfuric acid and concentrated nitric acid on the table. He quickly picked up his wife's cloth apron to wipe the mixed acid on the table. After a hurry, he hung his apron by the stove to dry, but it burst into flames and turned to ashes in an instant. Cybertron returned to the laboratory with this "great discovery" and repeated "accidents". After many experiments, Cybertron finally found the reason: the main component of the original cloth apron was cellulose, which contacted with the mixed solution of concentrated nitric acid and concentrated sulfuric acid to produce nitrocellulose ester, which was later widely used as nitrocellulose. That is, nitrocellulose, is used to stick photosensitive chemicals to glass to make equivalents similar to today's photographic film.
in the 185s, Parks looked at different ways to deal with collodion. One day, he tried to mix collodion with camphor. To his surprise, a flexible hard material was produced after mixing. Parks called the substance "Paxsin", which was the earliest plastic.
So, the inventor of plastic should be Pax, and the inventor of plastic bag has no definite person. It was developed by people in daily life in the 192s.