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Question:

what is it that makes plastic bags stretch?

what has been added to the polymer structure of plastic bags that allows them to stretch?

Answer:

well all mater has a certal elasticicity and pvc (poly vinel cloride) has a higher one than most other matirilas
There are many types of plastic and they are all made of very long molecules. Nothing is added to make them stretch. One way to grasp the microscopic structure is a thought experiment. Imagine millions of garden hoses lying on the ground to a depth of a foot. The hoses are unrolled and laying in all different directions. They are not connected to each other so if you push or pull a group of them they will bend and flex. In the same way a sheet of polyethylene will flex and stretch. Some plastic molecules like those that make up Plexiglass? have large molecules branching off the central strand. In our thought experiment that would be like each garden hose having grappling hooks attached to it all along its length. In this case, you would not be able to pull bundles of hoses around very well because the hooks latch the hoses together and make the layer more solid. That is why Plexiglass? is a hard and mostly inflexible plastic. The same for PVC and also for the polystyrene that your computer monitor is made of. They do add slip agents to plastic film such as that used in trash bags to keep it from clinging to itself. Saran Wrap? clings to itself because it has no added slip agent. Many other additives are used to give plastic the qualities the customer desires. .

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