“They(the new plastics)are light，but very strong—30 percent lighter and three to four times stronger than old plastics，”research leader Alcides Leao from Sao Paulo State University in Brazil told the American Chemical Society.Some of the fibers can be as strong

　　as Kevlar，a super­strong material used to make bulletproof vests.Besides，the plastics are also more resistant to damage from heat，water，oxygen and even spilled gasoline.

　　Cellulose(纤维素)is the main component(成分)of wood and has been used for centuries to make paper.Recently scientists have discovered that intensive(密集的)processing of wood releases tiny or nano­cellulose fibers，so tiny that 50,000 could fit across the width of a single human hair.When mixed with other raw materials，these nano­cellulose fibers can make plastics stronger.

　　According to Leao，pineapple leaves and stems(茎)，and a plant related to the pineapple in South America，called curaua，rather than wood may be the most promising source for nano­cellulose.To create the plastics，researchers put the leaves and stems of pineapples and other plants into a device similar to a pressure cooker.Then they added certain chemicals and heated the mixture over several cycles，producing a powder that was then added to the plastics.

　　The process is costly，but it takes just 1 pound of nano­cellulose to produce 100 pounds of super­strong，lightweight plastics，Leao pointed out.

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