The Chemistry of Mylar

Introduction

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Mylar is a polyester made into a skinny film that is used in most plastics as well as many other appliances around the home.  Mylar interested me after I discovered that most drumheads, as I am an avid drummer, are made from mylar because of its ability to stretch, resist weather, and take a pounding without breaking.

Composition of ...

There are only 2 compounds in mylar


  • dimethyl terephthalate (C10H10O4)

  • ethylene glycol (C2H6O2)

Main Chemicals, Compounds, Components

Dimethyl terephthalate is one of the two organic compounds used to make polyethylene terephthalate (or, if rolled out into a thin sheet, Mylar).  Dimethyl terephthalate is produced from para-xylene and methanol.  First, para-xylene and para-Toluic ester is oxidized with air and a heavy metal catalyst like cobalt.  This results in an acid mixture that is then esterified with methanol to make a mixture of esters.  These esters are then distilled to remove impurities and then crystallized to remove even more impurities and extra chemicals, thus, resulting in dimethyl terephthalate.  


Ethylene glycol is the second of the two organic compounds used to make polyethylene terephthalate.  Ethylene glycol  is created from a reaction between water and ethylene at a slightly high temperature.  This simple reaction results in ethylene glycol.


Chemistry's Role

It takes 1 process to produce polyethylene terephthalate and 1 extra step to create biaxially-oriented polyethylene terephthalate (A.K.A Mylar).


Step 1:  dimethyl terephthalate and ethylene glycol are reacted with a basic catalyst at 150-200 degrees C (302-392 degrees F).  Excess products are distilled off to keep the process moving constantly forward.  The reaction is then bumped up to 270-280 degrees C (518-536 degrees F) while continuing to distill unwanted and hindering products.  The product results in polyethylene terephthalate.

Step 2:  The molten polyethylene terephthalate is then taken and rolled into a thin sheet using heated metal rollers.  This is basically what biaxially-oriented means; it just got rolled into a sheet.


Background Research

Mylar was founded in the mid 1950s by DuPont, ICI, and Hoechst.  After finding out about the resistant, flexible, and insulative properties of mylar, NASA launched Echo II which was a 40 m diameter balloon made from mylar and aluminum.

Resources

http://www.moderndrummer.com/site/2011/10/what-you-need-to-know-about-drumheads/

Gives an brief intro on what modern drum set heads are made of and lists the different types of drum heads

https://en.wikipedia.org/wiki/Polyethylene_terephthalate

In depth description of of polyethylene terephthalate (Mylar).  From how it’s created, to it’s chemical composition, it’s got almost everything you may need to know about mylar.

http://chemistry.about.com/od/polymers/f/What-Is-Mylar.htm

Basic properties about Mylar and a good diagram on the process of creating it

http://www.britannica.com/science/polyethylene-terephthalate

Process of the creation of PET and its uses.

http://pubchem.ncbi.nlm.nih.gov/compound/dimethyl_terephthalate#section=Top

Rundown of dimethyl terephthalate and basic knowledge about it.

https://en.wikipedia.org/wiki/Dimethyl_terephthalate

Pretty much everything you need to know about the compound dimethyl terephthalate

https://en.wikipedia.org/wiki/Ethylene_glycol

Pretty much everything you need to know about the compound ethylene glycol



About the Author
Riley Kriskovich is a Junior at Billings Senior High School.  He enjoys drumming, gaming, doing science projects 2 days before they’re due, and joking about enjoying doing science projects 2 days before they’re due.
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