Date: November 2005
What is the hardest plastic made?
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.
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Update: June 2012