The encyclopedia · Engineering & Operations · Technical decision · 1967–1973
Wyeth's stretch-blow PET bottle held soda pressure without bursting.
Nathaniel Wyeth stretched and blew polyethylene terephthalate to make a light bottle that held carbonation and passed FDA purity.
DuPont
the move
Soda came in heavy, breakable glass bottles that were costly to make, ship, and collect. Plastic was light and cheap, but most plastics split under the pressure of carbonated drinks or contaminated their contents.
In 1967 DuPont engineer Nathaniel Convers Wyeth, a member of the famous Wyeth art family, started work on a lightweight plastic bottle that would not crack under the pressure of carbonation.
He settled on polyethylene terephthalate — the same material as DuPont's Mylar film — and invented a process called stretch blow molding. He molded a preform, reheated it, stretched it lengthwise, then blew it into a mold, orienting the polymer in both directions.
That biaxial orientation made the wall strong and uniform, able to withstand more than 100 pounds per square inch while staying light. The bottle received US patent 3,733,309 on May 15, 1973 and became a defining package.
why it works
- Stretching PET in both directions aligns chains and strengthens the wall
- A thin, light bottle still holds more than 100 psi of carbonation pressure
- Polyethylene terephthalate met FDA standards for food-contact purity
- One molded part replaced a heavy, fragile glass container
what transfers
When the incumbent is strong only because it is thick, orient the new material so it is strong while thin and light; matching the job's physics, not the old package, is the breakthrough.
what came after
The PET bottle went from zero in the mid-1970s to roughly 400 billion bottles made a year worldwide. It became both a packaging standard and a plastic-waste issue, and recycling of PET turned into a sizable stream in its own right.
references
- Biaxially oriented polyethylene terephthalate bottle (US 3,733,309)
- Oct. 24, 1911: Birth of an Inventive Wyeth
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