has anyone ever used this to wrap branches of an artificial twig tree? Thank you

I used it for a jungle themed child's birthday party. I like your idea of wrapping an artificial twig tree though! I believe it would work VERY well! Awesome idea!

Can I use this outdoor for long time?

I would say so, but over a long period of time it might loose color and may be worn out from the outside elements.

I would like to use this in a children's toy product that will be sold on the market. are there added chemicals? What is the ingredient list?

The contents are: Jute and artificial fabric so Jute is a natural fiber and the cord is made out of jute. The leaves are made of artificial fabric like the fabric artificial flowers are made of so most likely something like polyester. If you read the description of the item and the paragraphs below where it says “about this item” you find the vendors description of the materials. Nevertheless it will be inconvenient if a child swallows one of those small leaves besides it is very likely the jute fabric was treated and that I don’t know how the jute industry treats those fibers so if I were you I would do a research about the topic (Google)