Metallized polyester film has a wide range of uses


The concept of linking certain small molecules together […]

The concept of linking certain small molecules together Aluminum mylar to produce long chains of polyester was developed in the  by DuPont chemist Wallace Carothers. But polyester research took a back seat when Carothers came up with nylon, a commercially more viable polymer. However, British chemists John Whinfield and James Dickson pursued Carothers’s work and in 1941 developed a polyester fabric eventually marketed as Terylene. Then in 1946 DuPont bought the legal rights to polyester manufacture and began to market polyester as the magical fabric that needed no ironing. This was soon followed by Mylar, a polyester film that that could produced to be 13 times thinner than a human hair and still absorb the impact of a baseball thrown at up to 80 miles per hour. Since it was unlikely that any of our volunteers could muster such a speed, the only thing we had to worry about was being hit by the ball. Luckily, that never happened.

Polyester films can also be coated with a thin layer of metal, usually aluminum. This reduces the permeability of the film and gives it a reflective surface, just the properties needed for construction of the world’s first “satelloon.” In 1960, Project Echo placed a 30.5-meter diameter metallized Mylar balloon into Earth orbit to reflect telephone, radio and television signals between continents. Mylar films were also used in NASA’s spacesuits for radiation resistance and for keeping astronauts warm. Later, the technology was applied to produce emergency blankets to conserve body heat for shock victims, premature babies and marathon runners.Mylar found application in food packaging and decorative items such as Christmas tinsel. And the helium balloon industry took to aluminized polyester because it kept the gas from diffusing out as readily as from a rubber balloon. Mylar balloons became popular at celebrations of all sorts without people giving much thought to where they eventually end up.

But it is time to give the issue some thought.A good number of these balloons escape and can cause two types of mischief. They can float into power lines and because of the conductivity of the aluminum can cause outages and even explosions. The problem is not trivial, with San Diego Gas and Electric recording 312 outages in the last five years caused by balloons. As a consequence, a California bill now proposes to ban Mylar balloons. Florists, decorators and party supply stores are up in arms, claiming that millions of dollars in business would be lost. California actually has a current law requiring Mylar balloons to be weighted down so they can’t fly away and the balloon industry claims that a ban is overkill and the problem of rogue balloons could be eliminated if the law were properly enforced.Some municipalities in England are also considering a ban, but there the concern is more that whatever goes up must eventually come down.

And the balloons can come down in the ocean, where the metallized polyester breaks down into small pieces that can be mistaken for food by fish.Runaway Mylar balloons are a legitimate problem, but other allegations made about polyester don’t hold water — like the claim that drinking from a polyester water bottle that has been left in a hot car is a risk factor for breast cancer. That warning has been circulating ever since singer Sheryl Crow appeared on the Ellen DeGeneres TV show to discuss her breast cancer diagnosis. When such a calamity occurs people commonly look for possible causes of their affliction and the discussion turned to water bottles left in a hot car. The lay press is full of articles demonizing plastics, mostly in an unjustified fashion, and Crow likely heard about chemicals like bisphenol A and the phthalates that have been accused of causing cancer. Neither of these is present in the kind of water bottles Crow was concerned about. Bisphenol A is used to make polycarbonate plastics, which are used in the large carboys that sit on top of water coolers but not in the commonly used water bottles that are made of polyester. And here some confusion about phthalates enters the picture.