PHYSICAL PROPERTIES

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 resistant) sheet may be used.
CHEMCAST GP sheet may be perceived as "transparent wood" which can be formed making ideal for a wide range of applications.

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.

I.. Safety
II. Weather Resistance
III. Dimensional Stability
IV. Weight
V. Stiffness
VI. Cold Flow
VII. Strength and Stresses
VIII. Expansion and Contraction
IX. Heat Resistance
X. Light Diffusion
XI. Solar Control Series
XII. Formability
XIII. Cutting and Machining
XIV. Cementing
XV. Annealing
XVI. Flammability
XVII. Thermo Conductivity
XVIII. Thermo Shock
XIX Surface Hardness
XX. Electrical Conductivity

SAFETY 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 large pieces.

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 buildup.

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 smoke.

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 conditions.

U­Factors-BTU/hour sq. ft. °F.

CHEMCAST® GP Sheet Thickness

Summer Winter

'American Society of Heating, Refrigerating and Air Conditioning Engineers

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 NetTALK!

ELECTRICAL 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 destatisizing agent.

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