Plastic's brand new spin.

Chrysler rolls out a new car--made of the same plastic as your soda bottles! Smart science or car-azy idea?

Has the whole world gone plastic? Plastic jackets, trash bags, stereos, football helmets. What's next? How about a car! Chrysler--one of the big-three U.S. auto-makers--has come up with the very first plastic car. About 15 percent of its plastic comes from (gulp!) recycled soda bottles.

This is no putt-putt to spin up and down the aisles of Toys `R' Us. Chrysler has produced about 10 prototypes--or full-scale models--of what they call a Composite Concept Vehicle (CCV). The CCV's body is made almost entirely of polyethylene terephthalate, or PET, the same tough, flexible plastic used to make soda bottles.

"About three years ago, we set out to develop a car that weighs and costs half of what a Dodge Neon does," says Scott Fosgard, a Chrysler spokesperson. "Along the way we came across PET." PET plastic is cheap, sturdy, and recyclable. That's good news in a world flooded with plastic. Americans dump about 20 million tons of plastic every year and recycle only 5 percent, according to the Environmental Protection Agency.

No one knows how much plastic ends up in landfills (huge trash heaps), where it sits for centuries. Why is plastic such an environmental nightmare? Because of most plastics' chemical makeup, sunlight, water, and other decomposing agents simply can't break them down. But once the CCV sputters to the end of its 10-year or 100,000-mile lifespan, its plastic parts won't head for the dump.

They can be "rerecycled"--in other words from soda bottle to car, back to soda bottle again, Fosgard says.

PLASTIC DOUGH

The shaping and re-shaping of plastics makes them seem as versatile as flour dough. Whip up a batch of dough and you can bake anything from pretzels to pizza crust. Chemists whip up plastics to fashion everything from clothes and razors to phones and TVs (see "Future Fashion," SW 10/20/97). What makes PET tough but versatile? The answer lies in its chemistry, says Steve Leyrer, program director at Ticona, the company in Summit, New Jersey, that makes the PET-based compound for Chrysler.

To make PET, Ticona uses a chemical reaction called polymerization. Chemists combine thousands of small carbon-based molecules called monomers to produce long chain molecules called polymers. Plastics are polymers that mainly come from substances derived from natural gas and petroleum. In their recipe for PET, Ticona engineers combine monomers of an alcohol (ethylene glycol) and an acid (terephthalic acid). The end products: water and polyester polymers.

Linked together in a long chain, the polyester molecules form the polymer PET. Because the chemical bonds--or links--between the molecules are strong, the plastic is durable. Still, is crunchable pop-bottle plastic really tough enough for a car? Unlikely. Engineers mix in additives like glass fibers to make PET tougher. They also add an ultraviolet inhibitor to block the harmful effects of sunlight that weaken plastic. Finally, they stir in a rainbow of pigments that permanently dye the plastic. That means no paint job, ever!

One of the most useful properties of PET is that it's thermoplastic. That is, it softens when heated, and hardens when cooled. This property enables manufacturers to mold PET over and over again.

But don't worry about the CCV having a meltdown on a sweltering summer day. The plastic only softens at temperatures of 250 [degrees] C (482 [degrees] F) or higher.

TOY MAKER'S DREAM

Instead of using machines to cut steel doors and hoods, Chrysler injects molten PET into a giant mold. But first, Ticona melts PET together with other materials and forms a strand of compounded plastic. These strands are cooled, then cut into pellets. Manufacturers feed the pellets into an injection molding machine, which injects the plastic into molds producing the large body sections. Four large plastic sections, bonded together with glue and bolts, shape the entire body. The only part not made of plastic is the steel frame. "It's as easy to assemble as a toy," says Bernard Robertson, vice president of engineering technologies at Chrysler.

But what a toy! The CCV weighs 545 kg (1,200 pounds) and costs about $6,000. (A Neon weighs 2,400 pounds and costs about $12,000.) To keep the CCV lightweight, engineers installed an engine only as powerful as a lawn mower. The car only travels up to speeds of 80 kph (50 mph), and Chrysler foresees a market for the CCV in rugged regions of Africa, Asia, and South America. The company hopes its plastic cars will roll off the assembly line by 2000. Anyone for a spin?

RELATED ARTICLE: VANISHING PLASTIC?

Plastic has a nasty environmental rap. A plastic bag can sit in a landfill for centuries and remain intact. But that may soon change.

Sheila Browne, a chemistry professor at Mount Holyoke College in South Hadley, Massachusetts, has developed a biodegradable plastic. It decomposes--with a little help from bacteria.

Strangely enough, her plastic comes from bacteria, too. More than 600 types of natural bacteria produce polymers (long strings of molecules used to make plastics) in their microscopic bodies. The polymers are like bacteria fact, used for energy.

Browne grows these bacteria in vats filled with water, feeding them sugar, starch, and plant oils like a nurturing parent. The bacteria digest these foods to make the polymers. Then Browne drains the water and extracts the polymers using solvents, chemicals that kill and dissolve bacteria. Voila! The result is plastic that can be molded into an array of disposable products--like bottles, diapers, or razors.

Browne claims that products made from biodegradable plastic will decompose in any moist environment that harbors bacteria, like in compost or a landfill. "You can stick a bottle made of biodegradable plastic in a pile of leaves or mulch, and it will become water and carbon dioxide within six months," Browne says. (Bacteria release water and carbon dioxide as waste products when they break down food.) Because the plastic decomposes into natural substances, it won't pollute.

If they're so environmentally friendly, why aren't biodegradable plastic products used more often? Price for one. Browne's biodegradable able polymers cost $4 a pound to manufacture, compared to 50 cents per pound for polypropylene, a common non-biodegradable plastic. Still, several companies are already making and selling biodegradable plastics. Now that's environmental-friendly.

RELATED ARTICLE: hands on science

Elastic Plastic

How can you make plastic? Experiment with chemical reactions between substances to find out.

WHAT YOU NEED

Borax * distilled water * white glue * 4 plastic cups * measuring spoons * stirring stick * marker

WHAT TO DO

1. In one cup, mix 1.25 ml (1/4 tsp) of Borax into 120 ml (1/2 cup) of water. Stir the mixture until the Borax dissolves.

2. Spoon 15 ml (1 tbsp) of glue in another plastic cup.

3. To make Elastic Plastic: Add 5 ml (1 tsp) of Borax solution to the cup with glue. Stir the mixture for 5 minutes. Label this cup A.

4. Repeat steps 1 to 3. This time, use 2.5 ml (1/2 tsp) of Borax and 120 ml water to make the Borax solution. Label the second cup of Elastic Plastic B.

5. Take Elastic Plastic A and knead it--stretch and squeeze it--inside the cup for two minutes. Repeat with Elastic Plastic B.

6. Tilt each cup on its side. How does each Elastic Plastic move?

7. Tilt each sample of Elastic Plastic: Which one holds more weight? Stretches farther? Bounces higher? What other tests can you do?

CONCLUSIONS

How does Elastic Plastic differ from the Borax solution? How does it differ from the glue?