ACRYLITE® Light Transmission and Reflectance Technical Information

TECHNICAL INFORMATION ACRYLITE Light Transmission and Reflectance Extruded Sheet Light and Radiation Light or electromagnetic radiation can be divided into several bands or categories each defined by a specific wavelength range. Visible light is the most common type of electromagnetic radiation. Examples of other types of electromagnetic radiation are ultraviolet light x-rays radio waves and infrared light Graph 1. Solar radiation is the naturally occurring radiation that reaches the earths surface. It includes visible light as well as ultraviolet and infrared light Graph 1. The visible band of the electromagnetic spectrum which is the only range that can be detected by the human eye falls between 400 and 700 nanometers nm. Energy in the visible band is sensed as light due to the sensitivity of the human retina which acts as a detector for energy at this wavelength. On either side of the visible light band are ranges of similar electromagnetic radiation undetectable by the human eye. Graph 1 Electromagnetic Spectrum ACRYLITE-Extruded-Light Transmission and Reflectance 1213I Technical Information 1124 ACRYLITE Light Transmission and Reflectance Extruded Sheet Graph 2 Relative Distribution of Solar Energy The primary wavelengths of interest are those that fall between 200 and 2200 nanometers nm. This section of the electromagnetic spectrum can be divided into three components 1. Ultraviolet UV band 200 400 nm 2. Visible Spectrum 400 700 nm 3. Near Infrared Band 700 2200 nm Nanometers nm are commonly used for measuring wavelengths in the three bands listed above. One nanometer equals one billionth 1 X 10-9 of a meter. The intensity of the solar radiation that penetrates the atmosphere and reaches the earth varies considerably depending on the altitude ozone levels concentration of water vapor carbon monoxide dust and other types of contamination. The approximate relative distribution of solar energy mean noon sea level sunlight from 200 to 2200 nm is rep

resented in Graph 2. The ultraviolet band accounts for approximately 3 of the total solar energy whereas the visible band accounts for 45 and the infrared band accounts for 52. X-ray Transmission X-rays and gamma rays are characterized by wavelengths shorter than those in the ultraviolet spectrum thus they are not included in Graph 2. Colorless ACRYLITE extruded does not shield x-rays or gamma rays very effectively. ACRYLITE-Extruded-Light Transmission and Reflectance 1213I Technical Information 1124 page 28 ACRYLITE Light Transmission and Reflectance Extruded Sheet They shield approximately 1100 to 1400 as much as lead of the same thickness. The transmission characteristics are like those of flesh therefore these materials can be used in medical as well as industrial applications where x-ray transmission is required. Graph 3 UV Light Transmission of Colorless ACRYLITE premium and ACRYLITE Gallery UV filtering OP3 Ultraviolet Radiation Although ultraviolet UV radiation amounts to only 3 of the total radiation that reaches the earth it is energetic enough to cause chemical reactions weathering of polymers fading of certain dyes and even eye damage. The UV spectrum is commonly divided into three ranges 1. UV-C 200 290 nm 2. UV-B 290 315 nm Visible Light 3. UV-A 315 400 nm The visible light band ranges from 400 700 nm. Within this band colors occur in the sequence observed in the rainbow ranging from violet to blue green yellow orange and red. Each wavelength in the visible light band causes a particular sensation of color. As shown in Graph 1 solar radiation is most intense in the visible light band. This band is also the area where the human eye is most sensitive to radiation. However the eye is not equally sensitive to light emitted at all wavelengths it is most sensitive to the light in the yellow and green areas of the spectrum. When a light beam strikes material some light is transmitted some reflected and the rest is absorbed. Light transmission depends

on the reflectance at both surfaces of the material and the absorption of light into the material. Colorless ACRYLITE typically absorbs less than 0.5 of visible light per inch of thickness. However some light is reflected at both surfaces. Wavelengths in the UV-A range are responsible for tanning and pigmentation of the human skin. Wavelengths in the UV-B range cause the most photochemical degradation in plastics as well as sunburn. UV-C radiation is absorbed in the ozone layer and never reaches the earths surface. Colorless ACRYLITE extruded sheet have very small amounts of light transmission below 345 nm. In the range from 345 to 395 nm the light transmission varies with sheet thickness. Between 395 and 1000 nm all thicknesses transmit 92. Smooth colorless ACRYLITE extruded sheet are warranted for thirty 30 years to not undergo a change in light transmission exceeding 2-15. ACRYLITE Gallery UV filtering OP3 acrylic sheet is a continuously manufactured sheet product that absorbs approximately 99.7 200-390nm UV light. It is used in picture frames and shadow boxes to protect photos posters and other valuables from damaging ultraviolet rays. A beam of light striking a smooth ACRYLITE sheet perpendicular to the surface at 0 angle of incidence will lose approximately 4 of its light at each surface due to reflection resulting in a total loss of 8. Therefore the overall light transmission will be approximately 92. If light rays strike the sheet at angles greater than 30 from the vertical the surface reflectance will be greater than 4 and the overall transmission will be smaller. For example when light falls on colorless ACRYLITE extruded sheet from all angles as from a sky of uniform brightness the transmission factor will be approximately 85. ACRYLITE-Extruded-Light Transmission and Reflectance 1213I Technical Information 1124 page 38 ACRYLITE Light Transmission and Reflectance Extruded Sheet Colors Acrylic sheet can be formulated in thousands of different colors and

shades. This is because colorless acrylic sheet transmits visible light uniformly throughout the entire visible light spectrum. Therefore its transmission characteristics can be predictably modified using dyes and pigments to create a variety of colored sheet. thick sheet it will pass through twice as much pigment as when it passes through an 18 thick sheet. Therefore the 14 thick sheet transmits less light than the 18 inch thick sheet. Graph 4 Light Transmission-White Translucent extruded ACRYLITE sheet The addition of fillers and the application of surface textures or patterns are also used to vary the light transmission and reflection properties of the sheet. Ultimately the color of the sheet results from the combination of transmitted and reflected light that the human eye receives from the sheet. Since the ratio of transmitted to reflected light and the nature of the light source can vary based on application parameters the perceived color of a sheet can also vary with these parameters. Therefore it is very important to evaluate colors under the intended end use conditions. To assist in color selection light transmission and reflectance measurements can be used but actual evaluation in the end use is always recommended to ensure the expected results. Light Transmission of White Translucent extruded ACYLITE White translucent extruded ACRYLITE sheet is available in different densities to provide a variety of options for light transmission diffusion lamp hiding power and surface brightness. For lighting applications a formulation offering maximum diffusion combined with high light transmission is usually desirable. The color transmission of each white extruded ACRYLITE sheet will vary with the type and concentration of the pigment in the sheet. In addition the light transmission of almost every translucent white color will decrease with an increase in thickness. See Table A and Graph 4. This is due to the fact that the pigment concentration for most of the transl

ucent white colors is not changed for different thicknesses. Although the pigment concentration remains constant the amount of pigment absorbing the light that passes through the sheet will increase with the sheet thickness For instance when light passes through a 14 Table A Light Transmission of White Translucent ACRYLITE extruded sheet Color Number 3mm .118 4.5mm .177 6mm .236 WT031 GT 54 43 35 WT030 GT 31 23 18 Light Reflectance of White extruded ACRYLITE Light reflectance is also important in sign applications. Reflectance data is shown in Table C. When ACRYLITE extruded sheet is used for a non-backlit sign panel a nearly opaque white such ACRYLITE extruded sheet color WT030 GT having a light reflectance value of 91 will provide good contrast for painted or fabricated letters that may appear on the sign. ACRYLITE-Extruded-Light Transmission and Reflectance 1213I Technical Information 1124 page 48 ACRYLITE Light Transmission and Reflectance Extruded Sheet Table B Light Reflectance of White ACRYLITE extruded sheet Color Number BLACK Back-Up White Back-Up WT031 GT 33 68 WT030 GT 67 89 Above values are based on ASTM Test E-308 using CIE illuminant C. When a backlit sign must be as effective during the day as at night a compromise is in order. Select a white color that not only transmits a high percentage of light but also reflects a sufficient amount of daylight. Otherwise the sign will look gray during the day when it isnt illuminated from behind. Because most white ACRYLITE extruded sheet is translucent the surface brightness reflectance will be influenced by the color of the material behind the sheet or behind the sample when measured. This tech brief lists two kinds of reflectance values that have been obtained using two different test methods. The values shown in the left column in Tables C were obtained by measuring samples supported on black background material. In the right column of Table C the values were obtained by measuring the same sample supported

on a standard white background. The right column of data simulates the performance of white sheet when used in a sign box painted white on the inside. The percentages listed apply to 3 mm thick sheets. Other thicknesses will reflect different percentages of incident light. It is not practical to give a factor for all these sheet thicknesses but any necessary information can be obtained from POLYVANTIS Sanford LLC by calling 207 490-4230. As you can see from the comparison of the transmission and reflectance values of various 3 mm white colors as listed in Tables A B and C light reflectance increases as light transmission decreases. For applications requiring high light transmission color WT031 may be used. For maximum light reflectance color WT030 may be used. Because light transmission and light reflectance vary with thickness dont use a 3 mm thick white sample for selecting other thicknesses of the same color. Always evaluate the translucent white colors using samples that are the same thickness as the sheet that will be used in the final application. Light Transmission of Translucent and Transparent Colors Each white extruded ACRYLITE sheet colors light transmission decreases with an increase in thickness. The percentage of light transmission for all thicknesses of a given translucent or transparent color other than white is the same. This is accomplished by adjusting the colorant concentration according to sheet thickness. See Table D on the next page for a sampling of standard colors. When any of these colors are selected for a sign application samples should be checked under reflected light as well as with transmitted light. Some colors are quite similar in appearance under reflected light but transmit light at different rates. ACRYLITE-Extruded-Light Transmission and Reflectance 1213I Technical Information 1124 page 58 ACRYLITE Light Transmission and Reflectance Extruded Sheet Table C Light Transmission of Translucent Colored ACRYLITE impact modified ext

ruded Color Number Color Transmission 0RA65 Clear 92 WRT30 White 32 WRT31 White 55 1RK31 Ivory 30 3RK31 Red 3 3RK32 Red 10 3RK30 Red 2 2K002 Orange 7 1RK30 Yellow 23 5RK30 Blue 3 5RK31 Blue 1 Above values are based on ASTM Test E-308 using CIE illuminant C ACRYLITE LED color changing back lit blackwhite 9K004. ACRYLITE LED color changing back lit sheet also referred to as daynight sheet is intended for applications in sign channel letters and faces. This product offers sign manufacturers and designers an appearance which is black in daylight with no backlighting and translucent white or the color of the LED used at night when backlit. A special combination of additives provides this versatility without any change to the physical chemical and thermal properties which are characteristic of ACRYLITE extruded sheet. Infrared Radiation Infrared radiation is the long wavelength radiation beyond the sensitivity of the eye ranging from 700 to 1000000 nm. Its source may be the sun infrared heating elements or any hot object. Each type of infrared radiation is characterized by a specific range of wavelengths. We are primarily interested in the near infrared range NIR from 700 to approximately 10000 nm. Incandescent lamps and infrared heat lamps emit radiation in both the visible and infrared spectra. A major portion of energy especially in the case of infrared heat lamps is radiated at wavelengths above 700 nm. As the temperature of the energy source decreases radiation is emitted at longer wavelengths. All solar radiation as well as artificially created radiant energy will be converted into heat when absorbed and reradiated by any material. In the penetrating infrared band from 700 to 1400 nm clear 3 mm ACRYLITE extruded sheet transmits approximately 90 of infrared radiation see Graph 5. The transmission rate decreases slightly with increasing thickness. In the 1400 2200 nm range ACRYLITE extruded sheet transmit radiation at a gradually decreasing rate at 2200 nm transmiss

ion approaches zero. Graph 5 Light Transmission of colorless ACRYLITE approximation only not a specification ACRYLITE-Extruded-Light Transmission and Reflectance 1213I Technical Information 1124 page 68 ACRYLITE Light Transmission and Reflectance Extruded Sheet ACRYLITE IRT transmitting black Light Piping ACRYLITE extruded color 9M020 is designed to transmit infrared light but to absorb visible light. This color is ideal for use in applications where it is desirable to conceal infrared security cameras or infrared transmitters and receivers. Graph 6 shows the light transmission of color IRT transmitting 9M020 compared to standard extruded 9M001 black. The very low light absorption characteristic of ACRYLITE extruded sheet makes it perfect for light piping applications such as engraved signs inspection lights instrument dials and other similar items. To prevent excessive light loss at curves the radius of curvature should not be less than three times the sheets thickness. Its important that the sheets surfaces be highly polished and free of scratches to assure optimum reflection and prevent light scattering. Graph 6 Light Transmission of ACRYLITE premium 9M020 IRT Black The amount of light that enters a sheet from the edge depends on the sheets thickness and the edge transparency. Edges should be highly polished to maximize light transmission. Edges through which light will not enter should be polished and covered or coated with a highly reflective material to increase internal reflection. Large sheets may need to be illuminated from two or all four edges. Back-Lighting For back-lighting applications such as signs or light boxes white sheet or ACRYLITE Satinice optimim light diffusion sheets are often used between the light source and the sign face to improve light diffusion. This helps to eliminate bright spots caused by the light source. Greenhouse Glazing Transmission characteristics of colorless ACRYLITE extruded sheet are equal or superior to those of ordina

ry window glass. Colorless ACRYLITE extruded sheet can be used for greenhouse glazing since plants will grow as well under these materials as they would under glass. ACRYLITE extruded sheet are opaque to long wave radiation above 2200 nm. Long wave radiation is emitted by the mass such as soil or concrete inside a greenhouse. This opacity creates the greenhouse or heattrapping effect. For more efficient back lighting use an edge mounted light source together with ACRYLITE LED light guiding edge lit acrylic sheet for edge lighting. This sheet contains an additive that bounces light to its surface. By using additives of a specific refractive index and size and by selecting the right concentration of beads the efficiency of this back-lighting sheet has been optimized for edge lighting applications. Alternately back lighting using an edge mounted light source can also be accomplished by employing a sheet printed or painted with a white light diffusing pattern on one surface. The pattern density can be varied across the sheet surface as the distance from the light source changes to adjust the amount of light being reflected to the sheet surface. ACRYLITE-Extruded-Light Transmission and Reflectance 1213I Technical Information 1124 page 78 ACRYLITE Light Transmission and Reflectance Extruded Sheet Artificial Light Ultraviolet visible and infrared light can also be produced by artificial sources. Artificial light sources produce radiation with characteristics varying from source to source. Fluorescent lamps mercury vapor lamps germicidal lamps and welding arcs produce significant ultraviolet radiation. The typical emission curve for an incandescent bulb shows that its output increases from a low level at 400 nm to a high level at 700 nm and then rises steeply into the infrared range. As a result heat as well as light is emitted. Also colors appear warmer or redder than in daylight. In the case of fluorescent tubes the wavelengths of light emitted by the tube depends on

the type of phosphor coating used on the inside. Fluorescent lamps are available in a number of different types. Manufacturers publish the spectrophotometric distribution curves of each type. POLYVANTIS Sanford LLC 1796 Main Street Sanford ME 04073 USA www.polyvantis.com www.acrylite.co Semi-finished polymethyl methacrylate PMMA products from POLYVANTIS are sold on the European Asian African and Australian continents under the registered trademark PLEXIGLAS in the Americas under the registered trademark ACRYLITE both owned by Rhm GmbH Darmstadt or its affiliates. Fire Precautions ACRYLITE sheet is a combustible thermoplastic. Precautions should be taken to protect this material from flames and high heat sources. ACRYLITE sheet usually burns rapidly to completion if not extinguished. The products of combustion if sufficient air is present are carbon dioxide and water. However in many fires sufficient air will not be available and toxic carbon monoxide will be formed as it will when other common combustible materials are burned. We urge good judgement in the use of this versatile material and recommend that building codes be followed carefully to assure it is used properly. Compatibility Like other plastic materials ACRYLITE sheet is subject to crazing cracking or discoloration if brought into contact with incompatible materials. These materials may include cleaners polishes adhesives sealants gasketing or packaging materials cutting emulsions etc. See the Tech Briefs in this series for more information or contact your ACRYLITE sheet Distributor for information on a specific product. This information and all further technical advice is based on our present knowledge and experience. Such information or advice whether given at Buyers request or not implies no liability or other legal responsibility on our part including with regard to existing third-party intellectual property rights. In particular no warranty whether expressed or implied or guarantee of product propert

ies in the legal sense is intended or implied. We reserve the right to make any changes according to technical progress or further developments. The customer is not released from the obligation to conduct careful inspection and testing of incoming goods. Performance of the product described herein should be verified by testing which should be carried out only by qualified experts in the sole responsibility of a customer. Reference to trade names used by other companies is neither a recommendation nor does it imply that similar products should be used. ACRYLITE-Extruded-Light Transmission and Reflectance 1213I Technical Information 1124 page 88