Why Does Saran Wrap Cling?
Almost everyone has had experience with Saran Wrap. It is widely used to wrap food in order to keep it fresh. However, many users have complained that the cling of the plastic wrap sometimes makes it stick to things it shouldn't and makes it difficult to find the end of the roll. So what exactly gives Saran Wrap that cling? Does this Spark an idea?
-
About Saran Wrap
-
Saran Wrap is a brand of plastic wrap designed to cling to wrap around food items to keep them fresh. It was invented in 1953 by a scientist who originally wanted to create thick plastic covering for his car.
What's In It
-
According to the company's website, Saran Wrap is made of low density polyethylene (LDPE), although plastic wraps were originally made of polyvinylidene chloride (PVC).
-
Difference Between PVC and LDPE
-
According to studies by America's Test Kitchen, the main difference between PVC and LDPE is that PVC clings better but isn't impermeable. LDPE is impermeable but doesn't cling as well as PVC. However, to enhance its quality, polymers such as polyisobutene or polyethylene-vinylacetate (EVA) are usually added to plastic wrap to help it cling better.
PVC was originally favored for its low permeability to oxygen, water vapor and flavor and aroma molecules. It is also better than LDPE in protecting food against freezer burn. However, Saran Wrap eventually switched to LDPE, because it was cheaper and easier to manufacture and reportedly safer for household use and easier to recycle.
How It Works
-
The cling quality of Saran Wrap allows it to be wrapped around an item without an added adhesive. The plastic usually clings to itself or a container.
Why Does It Cling?
-
The clingy quality of plastic wraps such as Saran Wrap depends on elements including the electrical charge of the wrap and the charge of the container it is covering. For example, if a plastic wrap has a negative charge on its surface, it will cling well to surfaces that have a positive charge. This is why plastic wrap sometimes will cling and sometimes won't, depending on the charge of the container.
-
References
- Photo Credit wrapped bread image by Karin Lau from Fotolia.com
