Recycled Sails Honor Engineer's Genius

Wyeth pictured with a forest of products he helped to develop or for which he developed production machinery. Picture courtesy of DuPont.

An inspired chemical engineer creates soda bottles that can withstand carbonation...and be spun into sails.

On Earth Day, April 22, 1996, the world’s largest wooden Tall Ship set sail from Pier 5 in Boston Harbor on its first transatlantic voyage. The HMS Rose, a fullscale replica of a 1757 British frigate, was powered only by the wind in her 17 sails and was a model of the efficient use of energy. But on this day devoted to environmental awareness and maritime history, it was the sails themselves that represented the most efficient use of resources.

Three years earlier, in 1993, the Rose became the first ship rigged with sails made entirely from recycled material. More than 125,000 recycled-plastic soft drink bottles were combined with molded-plastic car fenders, broken down to resin, and spun into durable filament for the 17 sails. Eight tons of plastic bottles woven into windcatching beauty was also a tribute to the inventor of the first plastic soft drink container — Nathaniel “Nat” C. Wyeth.

Engineer as artist
Young Nat Wyeth grew up in a remarkable household; his father (the famed illustrator N.C. Wyeth) and mother worked hard to identify and nurture each of their children’s talents. Although he came from a family of painters, Nat became an engineer. This was fine with his famous father, who said, “An engineer is just as much an artist as a painter.”

In 1960, Wyeth was almost 50 years old and had been on the DuPont Engineering staff for almost 25 years. Plastics were rapidly replacing metal and glass in packages, bottles and containers of many kinds. Wyeth wondered why plastic wasn’t used for soda bottles. A colleague answered that plastic wasn’t strong enough. The carbonation would make the bottles expand and explode.

Intrigued, Wyeth filled an empty bottle of dishwashing detergent with soda, and put it in the refrigerator for the night. Just as his colleague had predicted, the bottle ballooned, and Wyeth’s search for the perfect plastic pop-bottle material began. He spent more than a decade of his 40-yr career in DuPont on what became known as “the pop bottle problem.” He started with nylon, which gets stronger when threads are stretched tightly. To make them even stronger, he developed a pre-formed mold that would force those threads to criss-cross when plastic is extruded into it. After experimenting with nylon and polypropylene, he settled on polyethylene- terephthalate (PET) for its superior elasticity. He used a puff of air to weave the molecules into the criss-cross net and to create his masterwork.

10,000 attempts
In a mold shaped like a bottle, Wyeth lowered a tube of molten plastic. He shot air through the plastic to splatter it all over the mold making a tic-tac-toe pattern weaving, on a tiny scale. This net of strong plastic would give birth to the graceful contours of the plastic soda bottle.

But the work was slow, and even after nearly 10,000 tries, the result was not yet a foregone conclusion. Wyeth said, “I remember the mixture of expectation and depression I felt when we opened our molding machine. It was late in the evening, and there was little crosslight hitting the mold. After months of frustration, we had grown used to seeing blobs of resin caked on the mold, or crude shapes that looked nothing like a bottle. This time, at first glance, it looked as if the mold was empty. A closer look revealed something else — a crystal clear bottle. Since then, I have seen countless truly beautiful PET bottles. But none of them will ever be as memorable as the first.”

The final product was light, clear, resilient and, most importantly, deemed safe for food and beverage handling by the FDA.

Billions of bottles
Wyeth filed for a patent on his creation in 1973, one of 25 patents with his name on it during his 40-year career at DuPont. The PET pop bottle proved itself quickly. The fizz stayed in, and the bottle was tough enough for shipping and rough handling. It survived the important two-meter drop test with no problem. In 1975, just a year before he retired, Wyeth was promoted to senior engineering fellow. In 1963, he was named the first DuPont engineering fellow.

The soft drink industry quickly adopted Wyeth’s creation. By 1999, industry estimates put production at 10 billion bottles/yr. What comes into the house must go out of the house, and so plastic pop bottles have now become one of the most recycled household products. When recycled, the polyester from the bottles goes into carpets, insulation and, in 1993, into 13,000 ft2 of sails unfurled to the wind on the masts of the HMS Rose.

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This article was originally published under the title "We're History" in the June 2003 edition of Chemical Engineering Progress magazine. This article was prepared by Neil Gussman, communications manager for the Chemical Heritage Foundation.