Bristolite Advantage
Our mission at Bristolite is to provide our customers with the highest quality products and supreme service at an exceptional value. We also aim to provide the industry with an abundance of accurate and useful information relative to daylighting and energy conservation. We take our corporate responsibility to our employees, associates, industry colleagues and customers very seriously and we see ourselves as stewards for the efficient use of sustainable carbon free energy.

Glazing Materials used in Plastic Unit Skylights

Acrylic & Prismatic




Super Insulating Silica Aerogel

Solar Heat Blocker Acrylic


Acrylic & Prismatic

Q: What is the most common glazing material used in plastic unit skylights? Back To Top

A: Acrylic or Polymethyl methacrylate. Acrylic (PMMA). Acrylics used for skylight glazing have varying optical, mechanical and thermal properties depending on the manufacturing process by which the sheet is made, chemical composition (additives), surface texture and color. Acrylics are well suited for skylight glazing due to their clarity, impact resistance, durability, weather resistance, low weight to strength ratio and formability A .125" thick general-purpose acrylic sheet is approximately 2 to 3 times more impact resistant than double strength window glass, and about 4 to 5 times more impact resistant than wire glass or other glasses. A .250" general-purpose acrylic sheet is approximately 9 to 10 times more impact resistant than wire glass or other glasses.

When specifying acrylic glazing one should consider the following.

Specify whether the acrylic sheet used to form the skylight dome is manufactured by the extrusion (continuous manufacturing) or cast process. Extrusion is the most popular and has a lower cost than the cast sheet. All other things being equal, cast sheet produces a stronger acrylic with greater chemical resistance than extruded sheet. Consequently cast sheet is about 25% more expensive than extruded sheet.

Specify general purpose (non impact modified) or impact modified. General purpose is by far the most commonly used and is has a lower cost than impact modified. Impact modified is available at numerous levels of impact modification including 10%, 15%, 25%, 35%, 40%, 50%, 75%, or 100% and with volume any percentage desired. For each increment of additional impact modification the impact strength increase and the sheet cost increases.

As a point of reference:

  • 40% impact modified acrylic is:
  • 5 to 6 times stronger than general-purpose acrylic.
  • 10 to 15 times stronger than double strength window glass.
  • 20 to 30 times stronger than polished wire glass or other glasses.

Considering the added cost for impact modification and cast formed sheet the vast majority of acrylic glazed skylights utilize general purpose extruded acrylic.

Specify surface finish. Surface finish may be smooth. Textured finishes have very little effect on the mechanical and thermal properties of the acrylic however surface finish may have a significant impact on optical properties. The most common texture utilized by skylight manufacturers is prismatic. The prismatic texture on a clear acrylic will produce a 95% to 100% haze/diffusion. Whereas a smooth surface on a clear acrylic will have 0% to 3% haze/diffusion. Medium white smooth acrylic and medium white prismatic acrylic are very similar in their haze/diffusion of 95%.

Specify color. Color has no affect on mechanical or thermal properties but it will affect the optical properties of light transmission and haze/diffusion as previously noted.

Many colors are available however white, bronze and gray are the most common with white the most common of the three. White is normally characterized as low, medium or high with the level designation representing the light transmission level of the colored acrylic. Low white will normally produce 100% haze/diffusion and 25% light transmission. Medium 95% to 100% haze/diffusion and 50% light transmission. High white 10% to 20% haze/diffusion and 75% light transmission. Medium white is the most commonly used due to its balance of light and haze/diffusion. Bronze and gray colors, often referred to as tints vary widely in optical performance depending on the amount of tint. A typical medium level of tint will produce 0% to 5% haze/diffusion with light transmission around 30%.

The most common glazing combination for industrial/commercial double glazed skylights is medium white, extruded, general purpose acrylic over clear, extruded, general purpose acrylic. This glazing combination formed with the appropriate acrylic thickness (subject to skylight size and installed climate conditions) and with an effective dome shape is very cost efficient in providing a good balance between light transmission (LT), haze/diffusion, solar heat gain (SHGC) and insulating properties (U Factor).

Acrylics are CC2 fire rated, their typical useful service life is approximately ten years and they are about 40% less expensive than polycarbonate.

Q: What is PMMA? Back To Top

A: Polymethyl methacrylate) (PMMA or acrylic) is a transparent thermoplastic, often used as a light or shatter-resistant alternative to glass. Chemically, it is the synthetic polymer of methyl methacrylate. The material was developed in 1928 in various laboratories, and was first brought to market in 1933 by Rohm and Haas Company, under the trademark Plexiglas. It has since been sold under many different names including Optix by Plaskolite. PMMA is an economical alternative to polycarbonate (PC) when extreme strength is not necessary. Additionally, PMMA does not contain the potentially harmful bisphenol-A subunits found in polycarbonate. It is often preferred because of its moderate properties, easy handling and processing, and low cost, but behaves in a brittle manner when loaded, especially under an impact force, and is more prone to scratching compared to glass.

Q: What is a polymer? Back To Top

A: A polymer is a large molecule (macromolecule) composed of repeating structural units. These subunits are typically connected by covalent chemical bonds. Although the term polymer is sometimes taken to refer to plastics, it actually encompasses a large class of natural and synthetic materials with a wide variety of properties.

Q: What is impact modified PMMA? Back To Top

A: Impact modified PMMA is general-purpose PMMA (aka acrylic) that has an impact modifier added to it to improve its impact strength. The composition of the impact modifier and the amounts added are proprietary information, but it can be envisioned as a rubber powder.

Q: In what way does impact modified PMMA differ from general-purpose PMMA? Back To Top

A: Plaskolite’s general-purpose PMMA is sold under the OptixÒ brand, while its impact modified PMMA is sold under the DuraplexÒ brand. The addition of an impact modifier to general-purpose PMMA will change the properties of the resultant sheet. At the end of this section you can view Plaskolite’s Product Guide. It is a good summary of the differences in sheet properties between Optix and Duraplex. With reference to this summary, the optical properties are similar for Optix and Duraplex with slightly less clarity at higher impact modifier content (internally defined by Plaskolite as “%I”). Duraplex has higher impact strengths than Optix, which must be balanced by the fact that the impact modifier will make the PMMA less dense and hard, as reflected in the lower tensile, flexural and Rockwell hardness values. On the thermal properties, Duraplex burns at a slightly higher rate with slightly more smoke than Optix, and it has lower deflection temperatures than Optix.

Q: How is clarity defined for a PMMA sheet? Back To Top

A: Clarity or “clearness” of the PMMA sheet can be rather subjective, as it is the human eye’s perception of light passing through the sheet. This perception can be quite different for different persons. Clarity is related to the amount of visible light (400-700 nm wavelengths) that passes through the sheet and the amount of cloudiness of the sheet (also known as “haze”). Light transmittance (LT) and haze can be measured (per ASTM D-1003), and a high % LT with low % haze means that a large amount of the visible light passes through the material, resulting in a clearer sheet. Haze can be surface (e.g., abrasion from sand particles, chemical attacks) or material features (e.g., excessive black specks), either intentionally or accidentally. The color of the sheet does factor into the LT values, which will reduce clarity (e.g., a black colored sheet is not clear); however, this applies primarily to solid colors, and not to the slight variations in shades of a clear PMMA sheet.

Q: Are there color shades in clear PMMA sheets? Back To Top

A: Yes, it is similar to when your mother or grandmother used a product called "bluing" in her laundry to make whites appear brighter. The bluing agents remove or mask yellow light to lessen the yellow tinge, and make the whites seem brighter and whiter than it would otherwise naturally appear to the eye. Every PMMA sheet manufacturer has to make a decision on the slight “blueness” in their sheet to give the best overall perception of a clear sheet to their customers. The Yellowness Index (YI) is a typical measurement of the color balance (i.e., red-green-blue) of a plastic material, which is related back to the yellowness of the material as yellow is the color that most negatively affects the perception of any plastic’s clarity.

Q: How does PMMA weather? Back To Top

A: Weathering of any material, including PMMA, results from exposure to the elements (i.e., sun, rain, wind, etc.) with a variety of consequences. This answer discusses PMMA’s exposure to sunlight. The primary concern with sunlight is the ultraviolet (UV) radiation (200 – 400 nm wavelengths) passing through the PMMA sheet. Many PMMA applications also require a high percentage of the UV radiation to be filtered out. All PMMA sheets, including Plaskolite’s, have UV absorbers to filter out the UV radiation. However, over time, the UV absorbers are slowly used up, and the bulk of the UV radiation will then be absorbed by the polymer matrix. As this process increases, the polymer matrix begins to degrade, and the PMMA sheet becomes more yellowed, then crazed and/or hazed and it becomes more brittle. The change in Yellowness Index (YI) is a good measure of the weatherability of the PMMA sheet, and Plaskolite has 10-year warranties on the YI change for both Optix (less than 4.0) and Duraplex (less than 8.0) under normal interior and exterior applications.

Q: How does PMMA absorb UV? Back To Top

A: All PMMA sheets, including Plaskolite’s, have UV absorbers added to the base PMMA resin to absorb UV radiation. The type and amount of UV absorbers in the PMMA sheet is proprietary information, but they are similar to the UV absorbers in sunscreen lotions which absorb the UV radiation and release it as heat. This reduces the absorption of the UV radiation by the polymer matrix and hence reduces the rate of weathering. The UV absorbers are “sacrificed” in the PMMA sheet as they take the “hit” from the UV radiation while sparing the PMMA polymer matrix. However, over time, the UV absorbers are slowly used up, and the bulk of the UV radiation will then be absorbed by the polymer matrix, which speeds up the rate of weathering.

Q: How does Prismatic acrylic differ from general purpose or impact modified acrylic? Back To Top

A: Only by surface texture. Prismatic is PMMA/Acrylic of either the general purpose or impact modified type with a texture imprinted on one side of the sheet. During the acrylic sheet forming process one side of the sheet is imprinted with a prism textured pattern. The prismatic pattern does not have a measurable effect on the light transmission, mechanical or thermal properties of the otherwise smooth surface acrylic. The chief benefit of adding the prismatic pattern to the acrylic is in diffusion/haze. Prismatic imprinting does improve the diffusion/haze characteristics of the acrylic and most demonstratively in the clear sheet. Although, the diffusion/haze characteristics of clear prismatic versus clear smooth acrylic are substantial the diffusion/haze characteristics between clear or white prismatic are negligible in comparison to medium-white smooth acrylic. Thus the most common dual glazing configuration throughout the world to achieve a high level of 100% diffused natural light is medium-white smooth surface acrylic over clear smooth surface acrylic. The second benefit of the prismatic imprint is the aesthetic appeal. For over fifty years you have had prismatic acrylic overhead while in a department store, business office, doctor’s office, school, municipal building, etc. The prismatic imprint was originally developed as a diffuser panel for fluorescent lighting. Due primarily to its aesthetic appeal prismatic imprinted acrylic has become increasingly popular as skylight glazing principally in daylit retail stores.

A Few More Acrylic Basics

Acrylic is a continuously processed sheet made through a fully integrated manufacturing process that converts acrylic monomer into acrylic polymer, then into acrylic sheet. It is crystal clear, glossy, durable, weather resistant and lightweight.

Optix acrylic sheet is 2-3 times stronger than double strength glass and 4-5 times stronger than polished wire glass or other glasses. DURAPLEX 50% medium impact modified acrylic sheet is 10-15 times stronger than double strength glass and 20-30 times stronger than polished wire glass. DURAPLEX 100% high impact modified acrylic sheet is 20-30 times stronger than double strength glass, and 40-50 times stronger than polished wire glass or other glasses.

Plaskolite’s clear acrylic typically has a UV transmittance of 10% to 20%) in the 250 - 400 nm wavelength range) and a visible light transmittance of 92%.

Acrylic is half the weight of glass and is CC2 fire rated.

Q: How is Acrylic Manufactured? Back To Top

A: By one of three processes. These are extrusion, continuous cast or cell cast.

Extruded Acrylic Sheet

Extrusion is a continuous production method of manufacturing acrylic sheet. In the extrusion process, pellets of resins are fed into an extruder, which heats them until they are a molten mass. This mass is then forced through a die as a molten sheet, the spacing of which determines the thickness of the sheet and in some cases the surface finish. The continuous band of sheet may then be cut or trimmed into its final size. The final product offers much closer thickness tolerances than cast sheet and due to the volume at which extruded sheet is produced, it is the most economical form. It's available in a wide selection of colors, finishes and sizes. Extruded sheet is by far the most uniform, economical, and is offered in a variety of colors, finishes and thicknesses.

Continuous Cast Acrylic Sheet

Continuous Casting is also a mass production form for manufacturing acrylic sheet. The process involves pouring partially polymerized acrylic between two stainless steel belts, which are separated by a space equal to the thickness of the sheet. The belts move through a series of cooling and heating units to regulate the curing and the sheet is cut at the end of the production line.

Cell Cast Acrylic Sheet

Cell Casting uses any of three processes. The first is the water bath technique. Acrylic syrup is poured into a mold constructed from two, tempered glass sheets, which are separated to produce the desired thickness, then sealed with a gasket. The mold is submerged in a bath, which maintains the curing temperature and efficiently removes the heat generated in the process. The second casting technique includes the original process which involved placing the "molds" containing a syrup" in a circulating air oven in which air passes, at a moderately high velocity, over the surface of the mold. The third method involves the use of a piece of equipment similar to a plate and frame filter press. Sections, which serve as the mold for the sheet, are alternately configured with sections through which water is circulated to promote the polymerization and cure of the sheet. All Cell Cast sheet products should go through a "post-cure" or "annealing" process.

Quasar Prismatic installed on manufacturing plant - white prismatic over clear prismatic

Inside view of above Quasar Prismatic - 70% light transmission 100% diffused

Bristol Acrylic skylight - clear acrylic over white prismatic


Q: What is fiberglass? Back To Top

A: The common name of fiberglass is generally considered to mean a polymer (unsaturated polyester resin) reinforced with fiberglass – much the way the steel is used to reinforce concrete. Chemically, it is a hybrid polymer of polyester (material used to make 2 liter soda bottles and polystyrene (material used as foam in coffee cups). It is an enormously versatile composite allowing one to tailor physical properties, flammability and weathering to meet many demands.

Q: How does fiberglass weather? Back To Top

A: Fiberglass weathering varies quite a bit depending on the formulation. A strength of fiberglass is that when formulated for both translucency and fire retardant properties, the weathering does not suffer as much as other polymeric materials. Non fire retardant formulations of fiberglass can approach the weathering performance of acrylic.

Q: How does fiberglass absorb UV? Back To Top

A: Fiberglass absorbs UV B radiation quite efficiently, while allowing UV A radiation and visible light to pass through. The reduction in light transmission in the warm part of the light spectrum provides visible lighting with reduced transmission of heat energy, thereby reducing the air conditioning demand on interior spaces when used as a light source in building products such as curtain walls and skylights.

Q: What is fiberglass’s track record and how does it compare to other glazing materials? Back To Top

A: Fiberglass has been used as a glazing material in skylights for nearly forty years and has demonstrated several superior performance qualities in comparison to other common glazing materials. Fiberglass glazing generally has comparable light transmission with 100% diffusion, lower solar heat gain coefficient, greater UV blocking and comparable insulating (U-Factor) properties in comparison to acrylics, copolyesters and polycarbonates.

The most impressive attribute of fiberglass glazing is its strength and longevity. Thousands of 25 year old plus fiberglass glazed skylights and smoke vents can still be found in service today predominately in the high-UV southwestern US. Recent load test were performed on numerous 5’ x 6’ fiberglass domes in service for a range of 13 years to 20 years in the southwestern US. All of the tested domes held 5,000 lb loads without catastrophic failure (only small tears developed which a person could not fall through). Fiberglass has proven to be one, if not the, strongest and longest lasting glazing material in the industry.

Fiberglass glazing has a significantly different appearance than acrylic, copolyesters and polycarbonates. Initially fiberglass glazing commonly has a soft brown color, much like a farm fresh hen egg in color. As the fiberglass begins to age it tends to transition through various stages of yellow. Light yellow at first and later darker yellow until the color begins to become brownish again. The color changes with age are most noticeable from the outside of the skylight (on the roof). From below, in the building interior, the view is much more consistent over the life of the skylight and it is a view of diffused natural light. Color in skylight glazing is more a matter of perception than reality in terms of light transmission. Color does not affect light transmission as significantly as it does the perception of light transmission. Of all colors, yellow is the color that most negatively affects the perception of any plastic’s clarity or light transmission.

The most prevalent fiberglass skylight glazing in the industry is Bristolite’s proprietary Energy Star Fiberlite. Fiberlite glazing cost is about twice that of acrylic and coployester and approximately 2% more than polycarbonates.

Fiberglass is CC1 fire rated and its typical useful service life is approximately twenty five years.


Q: What is Copolyester? Back To Top

A: Copolyesters are Polyester based polymers created and enhanced through a chemical reaction. A polymer is a large molecule (macromolecule) composed of repeating structural units. These subunits are typically connected by covalent chemical bonds. With Copolyester, the types of additives provide for significant changes in the ultimate properties of the product. Copolyester plastics are similar in composition to PET plastic used in water and soda bottles. Copolyester is sold under various trade names including Spectar CopolyesterTM and TiGlaze STtm. Available in smooth, matte and textured surface finishes in both transparent and translucent forms, copolyester plastics provide durability and flexibility in design. Copolyesters are designed to provide a unique balance of toughness and stiffness to provide impact resistance performance. Copolyesters may also be chemical resistant, depending on the chemicals used. Scratches are easily repaired with a hot air gun or the sheet may be top coated with an abrasion resistant layer to prevent scratches. Copolyester has excellent clarity and high haze/diffusion (for medium white) and it is easy to thermoform requiring less energy and lower temperatures than other plastic glazing materials Copolyester does not need to be pre-dried before thermoforming.

Q: How is clarity defined for Copolyester? Back To Top

A: Clarity or “clearness” of the Copolyester sheet can be rather subjective, as it is the human eye’s perception of light passing through the sheet. This perception can be quite different for different persons. Clarity is related to the amount of visible light (400-700 nm wavelengths) that passes through the sheet and the amount of cloudiness of the sheet (also known as “haze”). Light transmittance (LT) and haze can be measured (per ASTM D-1003), and a high % LT with low % haze means that a large amount of the visible light passes through the material, resulting in a clearer sheet. Haze can be surface (e.g., abrasion from sand particles, chemical attacks) or material features (e.g., excessive black specks), either intentionally or accidentally. The color of the sheet does factor into the LT values, which will reduce clarity (e.g., a black colored sheet is not clear); however, this applies primarily to solid colors, and not to the slight variations in shades of a clear Copolyester sheet.

Q: Are there color shades in clear Copolyester sheets? Back To Top

A: Clear Copolyester tends to have a slight shade towards the bluer side of clear versus some plastics that have a brownish tint. Copolyester sheet is tinted when it is manufactured using pigments to ensure a consistent color and is controlled using Hunter Lab’s CIELAB L*a*b* system of measurement. Copolyester sheet is typically supplied for glazing applications in clear sheet and translucent white.

Q: How does Copolyester weather? Back To Top

A: Almost all materials will change over time when exposed to the environment. Weathering of any material generally results from exposure to the elements (i.e., sun, rain, wind, etc.) with a variety of consequences. The effect of rain, wind, dust and dirt will cause the surface of many materials to change and depending on the severity of the change; the physical properties of the material may be detrimentally altered.

Sunlight and more importantly, the UV radiation portion of the light spectrum will also alter the physical properties. Copolyesters do not have any internal filtering agents to guard against the degradation of the sheet when it is outdoors. In order to avoid the degradation issue, a UV absorption layer is extruded on top (and bottom, if needed) of the sheet. This UV layer absorbs the UV while protecting the rest of the sheet. All organic materials, Including Copolyester, will suffer the effects of weathering from heat, light, and UV exposure over long periods of time. Organic materials include synthetic materials like paints, coatings, and plastics and natural materials such as wood and fabrics. Typically, UV radiation weathers organic materials the most rapidly of all the weathering mechanisms.

The speed at which plastic materials degrade under UV exposure varies significantly based on their individual chemistry. The most common response to weathering is discoloration, loss of light transmission, and a change in mechanical properties. Fortunately, Copolyester plastics can easily be protected from UV radiation through the incorporation of UV absorbers and stabilizers. These additives extend the useful life of the Copolyester by preferentially absorbing the UV radiation and harmlessly re-emitting it as heat.

Q: How does Copolyester absorb UV? Back To Top

A: Copolyesters are protected against UV degradation by adding ultraviolet absorbers that absorb UV radiation and dissipate the energy harmlessly. Copolyester can be damaged by UV radiation and must be UV stabilized to reduce damage caused by exposure to the Sun. Copolyester can be bulk loaded with UV absorbers, but more commonly, a UV cap layer that concentrates the UV absorber in a 3 to 5 mil thick layer on the surface of the sheet is used. Concentrating ultraviolet absorbers in a thin cap layer provides better cost effectiveness and performance.

Copolyester is CC1 fire rated, it is approximately 7 to 8 times stronger than general purpose acrylic, it has typical service life of twenty years and cost about 20% more than general purpose acrylic.


Q: What is Polycarbonate? Back To Top

A: Polycarbonates are widely used plastics from a specific group of thermoplastic polymers. One of the key characteristics of these thermoplastic polymers is that they have extremely strong molecular bonds which make polycarbonates tough and durable. Polycarbonates have high impact resistance, clarity, fire resistance and with UV coatings are extremely versatile in their application. The characteristics of their chemical compound allow for co-extrusion in the manufacturing process which provides opportunity for layering of additional materials which most often provide color and/or UV protection. Polycarbonates are well suited to LEED projects as they are 100% recyclable material and most manufacturers use up to 25% recycled material in the manufacture of polycarbonates. Low U-Factors and highly diffused light transmission make polycarbonates a good daylighting material.

Polycarbonate is CC1 fire rated and its typical useful service life is approximately fifteen years.

Super Insulating Silica Aerogel

Q: What is Silica Aerogel? Back To Top

A: An Aerogel is a low-density solid-state material derived from a gel in which the liquid component of the gel has been replaced with gas. The result is an extremely low-density, highly porous solid with several remarkable properties, most notably its effectiveness as an insulator. It is nicknamed frozen smoke, solid smoke, or blue smoke, due to its semi-transparent nature and the way light scatters in the material. It feels like expanded polystyrene (Styrofoam) to the touch. Aerogels are useful for a variety of applications. Some are good for thermal insulation and for cleaning up chemical spills. Others, when appropriately prepared, offer a useful drug delivery system for medical treatments. Carbon aerogels are used in the manufacture of small electrochemical double-layer super capacitors. Some aerogels have been incorporated into tennis and squash racquets, ski jackets and water bottles. In space exploration, aerogel materials have been used to trap space dust and to insulate the Mars Rover. By the addition of dopants, reinforcing structures, and hybridizing compounds to Aerogels, the range of applications has been considerably broadened.

Q: How is Silica Aerogel Produced? Back To Top

A: The general method of producing an Aerogel involves extracting the liquid component of a gel by a technique known as supercritical drying. In this technique, the liquid is brought to a "supercritical" state and then drawn out of the solid matrix of the gel. (When a substance is in its supercritical state, the distinction between its liquid and gas phases ceases to apply.) This method prevents the solid matrix from collapsing, as would happen with conventional evaporation. An Aerogel was first created by Samuel Stephens Kistler in 1931. Kistler produced the first Aerogel from a colloidal form of silica gel. His later work involved the production of Aerogels from alumina, Chromium (III) oxide, and Tin oxide. Carbon Aerogels were first developed in the early 1990s. Silica Aerogel can be made by drying (in an extreme environment) a hydrogel composed of colloidal silica, with water as the dispersion medium. Alternatively, the process may be started by mixing a liquid alcohol (like Ethanol) with a silicon alkoxide precursor to form an "Alcogel." Then the alcohol may be exchanged for liquid acetone (allowing for a better miscibility gradient), followed by liquid carbon dioxide, which is then brought above its critical point. A variant of this process involves the direct injection of supercritical carbon dioxide into the pressure vessel containing the Aerogel. The end result removes all liquid from the gel and replaces it with gas, without allowing the gel structure to collapse or lose volume. Aerogel composites have been made using a variety of continuous and discontinuous reinforcements. The high aspect ratios of fibers such as fiberglass have been used to reinforce Aerogel composites with significantly improved mechanical properties. Resorcinol-formaldehyde Aerogel (RF Aerogel) is a polymer chemically similar to a phenol formaldehyde resin. It is made in a way similar to the production of silica Aerogel. Carbon Aerogel is made by the pyrolysis of a resorcinol-formaldehyde Aerogel in an inert gas atmosphere, leaving a matrix of carbon. It is commercially available as solid shapes, powders, or composite paper.

Q: What are the Properties of Silica Aerogel? Back To Top

A: Kistler gave the name Aerogel because he derived it from silica gel. However, an Aerogel is a dry material and does not resemble a gel in its physical properties. To the touch, an Aerogel feels like a light but rigid foam, something between Styrofoam and the green floral foam used for arranging flowers. Pressing softly on an Aerogel typically does not leave a mark, but pressing more firmly leaves a permanent dimple. Pressing firmly enough will cause a catastrophic breakdown in the sparse structure, causing it to shatter like glass—a property known as friability. Although prone to shattering, an Aerogel is very strong structurally. Its impressive load-bearing abilities are due to the dendritic microstructure, in which spherical particles of average size 2-5 nanometers (nm) are fused together into clusters. These clusters form a three-dimensional, highly porous structure of almost fractal chains, with pores smaller than 100 nm. The average size and density of the pores can be controlled during the manufacturing process. Aerogels are remarkable thermal insulators because they almost nullify three methods of heat transfer: convection, conduction, and radiation. They are good convective inhibitors because air cannot circulate throughout the lattice. Silica Aerogel is an especially good conductive insulator because silica is a poor conductor of heat—a metallic Aerogel, on the other hand, would be a less effective insulator. Carbon Aerogel is a good radiative insulator because carbon absorbs the infrared radiation that transfers heat. The most insulative Aerogel is silica Aerogel with carbon added to it.

Due to its hygroscopic nature, an Aerogel feels dry and acts as a strong desiccant. People who handle aerogels for extended periods of time should wear gloves to prevent the appearance of dry brittle spots on their hands. Given that it is 99 percent air, an Aerogel appears semi-transparent. Its color is due to Rayleigh scattering of the shorter wavelengths of visible light by the nano-sized dendritic structure. This causes it to appear bluish against dark backgrounds and whitish against bright backgrounds. Aerogels by themselves are hydrophilic, but chemical treatment can make them hydrophobic. If they absorb moisture, they usually suffer a structural change (such as contraction) and deteriorate, but degradation can be prevented by making them hydrophobic. Aerogels with hydrophobic interiors are less susceptible to degradation than aerogels with only an outer hydrophobic layer, even if a crack penetrates the surface. Hydrophobic treatment facilitates processing because it allows the use of a water jet cutter.

Fig 1. A 2.5 kg brick is supported
by a piece of Aerogel weighing
only two grams.

Fig 2. Peter Tsou of NASA's Jet
Propulsion Laboratory holds
a sample of a Silica Aerogel.

Fig 3. A demonstration of
Silica Aerogels heat
insulating propertie

Q: Where is Silica Aerogel Used? Back To Top

A: Aerogels can be used for a variety of tasks, a number of which are noted below.

  • Commercially, Aerogels have been used in granular form to add insulation to skylights.
  • After several trips on the Vomit Comet, one research team has shown that the production of silica Aerogel in a weightless environment generates particles with a more uniform size and reduced Rayleigh scattering, so that the Aerogel is less blue and more transparent. Transparent silica Aerogel would be very suitable as a thermal insulation material for windows and Skylights, significantly limiting thermal losses of buildings.
  • The high surface area of various Aerogels has led to many applications, including as chemical absorbents for cleaning up spills. This property also offers the potential for some Aerogels to be used as catalysts or catalyst carriers.
  • Some types of Aerogel particles may be used as thickening agents in some paints and cosmetics.
  • The performance of an Aerogel may be augmented for a specific application by the addition of dopants, reinforcing structures, and hybridizing compounds. Using this approach, the breadth of applications for aerogels may be greatly increased.
  • The commercial manufacture of Aerogel 'blankets' began around the year 2000. An Aerogel blanket is a composite of silica Aerogel and fibrous reinforcement that turns the brittle Aerogel into a durable, flexible material. The mechanical and thermal properties of the product may be varied based upon the choice of reinforcing fibers, the Aerogel matrix, and opacification additives included in the composite.
  • NASA has used certain Aerogel (Fig 4) materials to trap space dust particles aboard the Stardust spacecraft. The particles vaporize on impact with solids and pass through gases, but they can be trapped in Aerogels. NASA has also used Aerogels for thermal insulation (Fig 3) of the Mars Rover and space suits. The low mass of Aerogels is also advantageous for space missions.
  • In particle physics, some Aerogels are used as radiators in Cherenkov effect detectors. The ACC system of the Belle detector, used in the Belle Experiment at KEKB, is a recent example of such use. The suitability of Aerogels is determined by their low index of refraction, filling the gap between gases and liquids, and their transparency and solid state, making them easier to use than cryogenic liquids or compressed gases.
  • Resorcinol- formaldehyde Aerogels are used mostly as precursors for the manufacture of carbon Aerogels, or when an organic insulator with a large surface area is needed. Their surface area can be as high as 600 m² per gram of material.
  • Metal-Aerogel nanocomposites can be prepared by impregnating the hydrogel with a solution containing ions of a suitable noble metal or transition metal. The impregnated hydrogel is then irradiated with gamma rays, leading to precipitation of nano particles of the metal. Such composites can be used, for example, as catalysts, sensors, or electromagnetic shielding, as well as in waste disposal. A prospective use of platinum-on-carbon catalysts is in fuel cells.
  • Some Aerogels may be used as drug delivery systems, based on their biocompatibility. Due to the high surface area and porous structure of the Aerogel, drugs can be adsorbed if introduced with supercritical carbon dioxide. The release rate of the drugs can be tailored based on the properties of Aerogel. Carbon aerogels are used in the construction of small electrochemical double layer super capacitors. Due to the high surface area of the Aerogel, these capacitors can be 2,000 to 5,000 times smaller than similarly rated electrolytic capacitors. Aerogel super capacitors can have a very low impedance compared to normal super capacitors and can absorb/produce very high peak currents.
  • Dunlop has recently incorporated Aerogel technology into a series of its tennis racquets, having used it earlier in squash racquets.
  • Chalcogels have shown promise in absorbing heavy metal pollutants such as mercury, lead, and cadmium from water.
  • An Aerogel material may be used to introduce disorder into the superfluid state of helium-three.

The Stardust dust collector with Aerogel blocks. (NASA)

Nano Insulgel/Lumira multi-wall polycarbonate skylight panel filled with translucent silica aerogel. (.17 U Factor)

For more detailed Silica Aerogel and skylight information see:
  • Green Building Technologies – Nano Insulgel/Lumira

Solar Heat Blocker Acrylic

Q: What is Solar Heat Blocker? Back To Top

A: Solar heat blockers are proprietary spectrally selective LowE coatings that can be applied to nearly all smooth surface plastic substrates. They allow high levels of visible light transmission while concurrently reducing solar heat transmission. The thickness of the applied coating is the determining factor in the final color of the plastic substrate and the level of light transmission and infra red and ultraviolet light reflecting. Solar heat blocker coatings can transmit visible light from 70% to 20%; block 50% to 95% of infra red light and up to 99.9% of UV light.

These special and proprietary coating are designed to reflect the outer ranges of the full light spectrum without significantly reflecting the portion of the light spectrum that can be seen by the human eye, 400 nano-meters to 700 nano-meters.

Coollite solar heat blocker acrylic outer dome

Coollite white prismatic acrylic inner dome appearance under solar heat blocker outer dome. This dome combination transmits cool, highly diffused, white light to the interior building space.

Coollites .26 SHGC installed on a Texas school. (next two photos)

Inside view of the Coollites above – solar heat blocker acrylic over white prismatic. (next two photos)