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Name: Brittany
Status: Student
Grade: 9-12
Location: NY
Country: USA
Date: November 2005

What is the hardest plastic made?

Hi Brittany

This is a good question, but one that may not be easily answered because a particular type of plastic may be formulated with different additives and still be called the same thing. For example, glass fibers are often put into polymers to make the material harder, more durable and dimensionally more stable. In general, polymer hardness is measured on the Rockwell or Shore scale, and the higher the number, the harder the material. I checked polyetherimide (known as PEI) with 30% glass fiber and found a Rockwell M hardness of 95-125 and a Shore D harness of 95-99. These values are about as high as polymers get. Polybenzimidazole and polyamide-imide are in the same neighborhood. The designation M or D specifies the way the test is performed.

Robert Froehlich

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