high impact resistance pc sheet
time2018/09/11
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Polycarbonate
Polycarbonate (PC) is an amorphous polymer with high impact strength, transparency,
high temperature resistance and good dimensional stability 1 . PC is formed via step-
growth polymerization of Bisphenol A (BPA) and carbonyl chloride.
PC is non-crystalline, yet is nearly as strong as highly crystalline polyamide (nylon) and
polyacetal (Delrin®) plastics 2 . This mechanical performance is due to the large aromatic
content in the backbone (the benzene rings) that gives high polymer stiffness. Observing
the structure of PC reveals the moderately large pendant groups (the Oxygen and
Carbon). These pendant groups promote entanglement with adjacent polymer chains.
Also, the hydrogen and oxygen molecules will allow for hydrogen bonding to occur. All
these factors increase resistance to intermolecular movement, which is needed for high
strength. The resistance to intermolecular movement also gives PC good creep
resistance 3 .
PC does have some limitations: low abrasion resistance, susceptibility to stress cracking,
low CO 2 permeability, decreased impact strength at lower temperatures and some UV
(ultraviolet light) sensitivity. However, polymers blended with other resins can
compensate for these limitations 4 . For example; PC reinforced with MoS 2 , graphite or
PTFE help improve slip and wear properties. The addition of short-strand glass fibers at
10-40% reduces stress cracking tendencies. Providing a boundary layer of a more
crystalline polymer, such as PET (polyethylene terephthalate) or PBT (polybutylene
terephthalate), reduces CO 2 permeability. A combination of PC+ABS (acrylonitrile-
butadiene-styrene) will improve low temperature impact strength and decrease the notch
sensitivity of PC. PC blends with PMMA (polymethylmethacrylate) increase UV
resistance.