Polycarbonate is a class CC-1 plastic according to the
combustion classification of Building Officials and Code
Administrators International, Inc. (BOCA) and the Southern
Building Code Conference (SBCC). However, it has application for
blast resistant glazing where large support deflections may be
tolerated. For example, polycarbonate glazing can be supported
in a cheaper frame that is either continually bolted or embedded
into the adjoining wall. On the other hand, TTG glazing must be
supported on a structurally stiff frame to prevent premature
Polycarbonate will burn when a flame is held to it.
However, it will tend to extinguish itself when the flame is
removed. Rated as a class CC-1 material, it is much less
combustible than acrylic plastic.
Polycarbonate will often test with a smoke density
rating over 500 according to the ASTM E84-95, Standard Test
Method for Surface Burning Characteristics of Building Materials.
As the Model Building Codes set an upper level on approval of
450, local building codes should be consulted before
polycarbonate is specified. As polycarbonate can be difficult to
break, local fire codes may require a percentage of polycarbonate
glazings to pop out for emergency egress and venting. Again,
local fire codes should be consulted.
Polycarbonate is resistant to most chemicals. However,
it is particularly susceptible to degradation by aromatic
hydrocarbons, gasoline, kerosene, carbon tetrachloride, esters,
ketones, and acetones phenols. Exposure to these chemicals can
result in embrittlement and hazing. Most, if not all, commercial
window cleaning preparations are compatible with polycarbonate.
Polycarbonate has been used as a monolithic cross-
section for protection against forced entry and blast attacks.
In its monolithic form, polycarbonate can be vulnerable to a
forced entry chemical attack because it has no barrier which
prevents or delays an imbuing substance from poisoning the
material. The use of chemicals is a sophisticated attack that
would require a skilled and knowledgeable aggressor. This
handbook will recommend the use of monolithic polycarbonate for
applications where this level of sophistication in forced entry
attack is not applicable.
Acrylic. Acrylic plastic is often used as an
alternative glazing material. It is not recommended for attack
resistant glazing due to its high flammability (class CC-2) and
its brittle failure mode. Its fracture pattern is similar to