CHEMCAST® Cell cast acrylic sheet
CHEMCAST® GP is a cell cast acrylic sheet made to exacting standards. It offers excellent optical characteristics, thickness tolerances, light stability, and low internal stress levels for consistent performance. Colorless sheet and a wide range of transparent and translucent colors are available.
CHEMCAST GP acrylic sheet is a lightweight, rigid
thermoplastic material that has many times the breakage
resistance of glass. Chemcast® GP is ultraviolet light absorbing and therefore very weather resistant withstanding
exposure for many years without losing its surface gloss or
mechanical properties. Chemcast®GP sheets can be easily
fabricated using wood working tools. It can be sawed, machined,
thermoformed, and cemented using readily available companion
products. SOURCES OF SUPPLY .
For applications requiring protection from fire arms, CHEMCAST BR (bullet
sheet may be used.
AVAILABILITY CHEMCAST® GP acrylic sheet is available
in thickness from .060" to
1.250 in several sizes, in colorless, numerous standard colors, and readily
accessible existing custom colors. Chemcast® can be color matched
by special quotation. Sheets
can be furnished masked with paper, half masked, unmasked,
static cling film masked, or with EVA poly film, a high-tack film
without an adhesive.
CHEMCAST® GP sheet complies with American National
Standard Z 97.1, Safety Glazing For Buildings. CHEMCAST® GP
sheet is more 17 times more impact resistant than glass. If
subjected to impact beyond the limit of its resistance, it does
not shatter into small slivers but breaks into comparatively
WEATHER RESISTANCE Acrylic
plastic offers weather resistance unmatched by any other plastic
material or most man-made materials. CHEMCAST® GP sheet will
withstand exposure to blazing sun, extreme cold, sudden
temperature changes, salt water spray and other harsh conditions.
It will not deteriorate after many years of service. CHEMCAST®
GP sheet has been widely accepted for use in domes and skylights,
fascia panels, school glazing, industrial plant glazing, aircraft
glazing and outdoor signs. Note that the stability against
deterioration from the weather elements pertains to clear
acrylic. Colored acrylics are subject to fading to varying
degrees depending on the colorants used.
DIMENSIONAL STABILITY Although
CHEMCAST® GP acrylic sheet will expand and contract due to
changes in temperature and humidity, it will not shrink with age.
Some shrinkage occurs when CHEMCAST GP sheet is heated to forming
temperature. When used as a glazing material, acrylic will tend
to bow toward the heat and humidity. It will reverse by the
season, for example, it will bow inwardly during winter months
and outwardly in the summer.
LIGHT WEIGHT CHEMCAST® GP
sheet is less than half the weight of glass, and 43% the weight
of aluminum. One square foot of 118" thick CHEMCAST GP sheet
weighs less than 3/4 pound.
STIFFNESS CHEMCAST GP sheet is
not as rigid as glass or metals. However, it is more stiff than
most thermoplastics such as acetate, polycarbonate, or PVC. When
subjected to high winds, a sheet will bow and foreshorten as a
result of deflection, requiring design considerations for rabbet
depth and thickness for use in windows, domes and skylights and
signs or other outside applications. Further data is available
via LET'S NetTALK!
When Chemcast® GP is formed into corrugated or domed shapes,
rigidity is naturally increased and deflection minimized.
COLD FLOW (or creep) can occur
when Chemcast® GP is insufficiently supported. For example, a
flat skylight will deflect with a snow load; or, a shelf will sag
if the proper thickness is not used and supports are infrequent.
STRENGTH AND STRESSES Although
the tensile strength of CHEMCAST GP acrylic sheet is 10,000 psi
at room temperature (ASTM D 638), stress crazing (tiny fissures)
can be caused by continuous loads below this value. Continuously
imposed design loads should not exceed 1500 psi. Localized,
concentrated stresses must be avoided particularly near drilled
holes or edges. For this reason, and because of thermal expansion
and contraction, large sheets should never be fastened with
bolts; installing Chemcast® GP in frames is more desirable. All
thermoplastic materials-including CHEMCAST® GP sheet-gradually
lose tensile strength as temperatures approach the maximum
recommended for continuous service, which, for CHEMCAST® GP
sheet, is 180 °F.
EXPANSION AND CONTRACTION
Plastics are organic materials which naturally expand and
contract more than inorganic materials. CHEMCAST® GP sheet will
expand 3 times as much as metals, and 8 times as much as glass,
and therefore the coefficient of expansion and contraction must
be considered by architects and designers. A 48" panel will
expand and contract approximately .002" for each degree F
change in temperature. Another quick calculation is Chemcast® GP
will expand (or contract) 1/8" per running foot per 100° F.
In outdoor use, where summer and winter temperatures differ as
much 100°F, a 48" sheet will expand and contract
approximately 1/4". Sash rabbets must be of sufficient depth
to allow for expansion as well as for contraction. For additional
more specific information LET'S NetTALK!
CHEMCAST® GP sheet also absorbs water when exposed to high
relative humidity, resulting in expansion of the sheet. At
relative humidity of 100%, 80%, and 60%, the dimensional
changes are 0.3%, 0.2% and 0.1%, respectively.
HEAT RESISTANCE CHEMCAST® GP
sheets can be used at temperatures from 40°F up to + 200 °F,
depending on the application. It is recommended that temperatures
not exceed 180°F to 200°F for continuous service. Components
made of CHEMCAST® GP sheet should not be exposed to high heat
sources such as high wattage incandescent lamps, unless the
finished product is ventilated to permit the dissipation of heat.
LIGHT TRANSMITTANCE Clear (colorless) CHEMCAST GP acrylic sheet has a light transmittance of 92%.
Transparent, colored CHEMCAST GP sheets can be used to reduce
glare and solar energy transmittance. The sheets are available in
a wide range of color densities with light transmittance values
from 6% to 79% , enabling designers to choose a density which
provides adequate daylight while controlling glare and solar heat
LIGHT DIFFUSION Translucent
white and colored CHEMCAST® GP sheets diffuse light and are
excellent for use as lighting lenses or to create special effects
in signs. Available in 4 standard densities Translucent white CHEMCAST® GP
acrylic sheet is available in several thickness varying in
light transmittance from 11 % to 67%. Note that transparent
colors have the same light transmittance in all thickness;
whereas, white translucence vary in light
transmittance becoming more opaque with thickness. For
example, 7328 white is more dense in .177" than .118".
SOLAR CONTROL SERIES Transparent,
colored Chemcast® GP sheets can be used to reduce glare and
solar energy transmittance. The
sheets are available in a wide range of color densities with
light transmittance values from 6% to 79% enabling designers to
choose densities which provide adequate daylight along with glare
control and solar heat buildup.
CHEMICAL RESISTANCE CHEMCAST® GP acrylic sheet has excellent resistance to many chemicals including:
CHEMCAST® GP sheet (Clear) is FDA approved for direct contact with food. It neither affects food nor is affected by food and is excellent for food containers such as commercial food bins or consumer designer bowls or cups.
It is attacked, in varying degrees, by:
FORMABILITY CHEMCAST® GP
sheet will soften gradually as temperature increases above
210°F. When heated to temperatures ranging from 340 °F to
380°F, Chemcast® GP becomes soft and pliable enabling it to be
formed into any desired shapes using inexpensive wood molds. The
optimum forming temperature within this range depends on
thickness and desired depth of draw. CHEMCAST® GP sheet will
typically shrink 1.5% when heated without a frame. As the sheet
cools, stiffness or rigidity will be restored and it will retain
the formed shape. Unlike extruded acrylic sheet, in the event of
mistakes, products formed of Chemcast® GP can be reheated back
to its flat shape and reformed to the desired shape.
CUTTING AND MACHINING CHEMCAST® GP sheet may cut by sawing or routing with power equipment saws or by scribing and breaking. Scribing is limited to straight cuts in thin sheets of Chemcast® GP acrylic, 1/4" or less and is practical for use by the craftsman who has no power tools when cutting small quantities of sheet. It can be drilled, routed, filed and machined much like wood or brass. Keeping cutting tools cool is recommended to minimize the buildup of localized stresses due to heat which can lead to stress crazing (fissure cracks). Well sharpened and "true" tools are essential to prevent heat build up and subsequent crazing and possible edge chipping.
Go to SOURCES OF SUPPLY for
information on cutting tools.
CEMENTING CHEMCAST® GP sheet can be cemented to itself using common solvent cements or polymerizable cements (SOURCES OF SUPPLY). The most critical factor is the condition of the edge to be cemented. The edge must be properly machined to have a square flat surface and no stresses (a network of fine cracks). Note: Always polish after cementing. Do not cement flame polished parts as crazing is almost certain to occur. Annealing parts prior to cementing is recommended. For additional information on cementing Chemcast® GP to itself or dissimilar materials Let's NetTALK!
ANNEALING is recommended to
eliminate stresses caused by machining and/or polishing.
CHEMCAST® GP sheet may be annealed at 180°F with the heating
and cooling times determined by sheet thickness. An approximate
guideline is: annealing time in hours equals the sheet thickness
in millimeters and the cool down period equals the sheet
thickness in millimeters. For example, 3mm (1/8") CHEMCAST®
GP sheet would be heated for 3 hours at 180°F and slowly cooled
for 3 hours.
FLAMMABILITY CHEMCAST® GP
sheet is a combustible thermoplastic and is classified by UL as a
slow burning plastic. Precautions should be taken to protect the
material from flames and high heat sources. Access panels may be
required for evacuation and venting of rooms glazed with
CHEMCAST® GP sheet. Generally speaking, the same fire
precautions that are observed in connection with the use of any
ordinary combustible material should be observed when handling,
storing or using Chemcast® GP.
Other properties related to flammability:
Burning rate is 4.6 cm per minute per 2 mm thickness) according to ASTM D 635.
Flame spread is 140 per 3mm thickness) according to ASTM E 84, or 110140 (or 3mm6mm thickness) according to CAN4S102.2.
Smoke density: Measured by ASTM D 2843 is 10.3%.
Self ignition temperature is 910°F (for 1.5mm thickness) when measured in
accordance with ASTM D 1929.
While these test data are based on small scale laboratory
tests frequently referenced in various building codes, these
tests do not duplicate actual fire conditions.
The products of combustion, if sufficient air is present, are
carbon dioxide and water and is therefore non-toxic. However, in
many fires, sufficient air will not be available and toxic carbon
monoxide will be formed as it will from other common combustible
materials. Burning Chemcast® GP acrylic does not produce either
excessive quantities of smoke or gases more toxic than those
produced by burning wood or paper. The concentration of carbon
monoxide and/or carbon dioxide released by burning Chemcast®GP
acrylic is a factor of the quantity of Chemcast®GP acrylic
involved and the conditions of burning. Consequently, it is
accepted for interior finish including lighting panels in
contrast to Styrene based products which produce a black noxious
THERMAL CONDUCTIVITY The
thermal conductivity of a material-its ability to conduct heat is
called kFactor. The kFactor is an inherent property of the
material, and is independent of its thickness and of the
surroundings to which it is exposed.
The kFactor of CHEMCAST® GP sheet is: 1.3 BTU
(hour) (sq. ft.) (°F./inch)
Whereas the kFactor is a physical property of the material, the UFactor- or overall coefficient of heat transmission-is the value used to calculate the total heat loss or gain through a window.
The UFactor is the amount of heat, expressed in BTU's, which will pass through one square foot of a material of a specific thickness, per hour, for each degree F. difference between inside and outside air temperatures.
This value takes into account the thickness of the sheet, whether the sheet is in a horizontal or vertical position, as well as the wind velocity.
UFactors are based on specific conditions (e.g., single glazed or double glazed installations) and are different for summer and winter.
Listed below are UFactors for several thickness of
CHEMCAST® GP sheet for single glazed, vertical installations,
based on the standard ASHRAE* summer and winter design
UFactors-BTU/hour sq. ft. °F.
CHEMCAST® GP Sheet Thickness
'American Society of Heating, Refrigerating and Air
The total heat loss or gain through a window (due to
temperature difference only) can be calculated by multiplying the
area of the window in square feet, times the difference between
indoor and outdoor temperatures in degrees Fahrenheit, times the
appropriate UFactor grom Table above). The answer will be
expressed in BTU's per hour. Heat intake through solar radiation
must be added to arrive at the total heat gain.
The heat savings in BTUs per hour can be determined with the
same formula used for UFactor.
CHEMCAST® GP sheet is a better insulator than glass. Its
UFactor or heat transfer value is approximately 10% lower than
that of glass of the same thickness. Conversely, its RTFactor
is about 10% greater.
THERMAL SHOCK CHEMCAST® GP
sheet is more resistant than glass to thermal shock and to
stresses caused by substantial temperature differences between a
sunlit and a shaded area of a window or between opposite surfaces
of a window.
SURFACE HARDNESS The surface
of plastics is softer than glass. Therefore, reasonable care
should be exercised in handling and cleaning CHEMCAST® GP sheet
similar to the care given to acrylic finishes on automobiles,
appliances or fine furniture. Use dampened soft cotton cloths
such as discarded undershirts or chamois to clean Chemcast®GP
and allow to air dry. Simonize wax can be used to polish
scratches. For additional information on the maintenance of
Chemcast®GP contact PlasticsOnLine's LET'S
CONDUCTIVITY CHEMCAST® GP sheet has many desirable
electrical properties and continuous outdoor exposure has little
effect on these properties. It is a good insulator with surface resistively higher than that of most plastics. This property also
causes it to build a static charge which makes dust particles and
lint somewhat difficult to remove. Anti-Static compounds are
available for use where static build up and high dust
concentration create a cleaning problem. Cleaning dirty static
charged parts can be best achieved using Joy dish washing liquid
in the same concentration as washing dishes. It is an excellent
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