Property Characteristics
Polycarbonates are characterized by an excellent combination of toughness, transparency, heat and flame resistance and dimensional stability. In unnotched izod impact tests and falling-dart tests, the unreinforced material resists breakage at very low temperatures and in thick sections. Humidity changes have little effect on dimensions or properties of molded polycarbonate parts. Even boiling water exposuse does not change dimensions more than 0.001 in/in after parts are returned to room temperature. Creep resistance is excellent throughout a broad temperature range and is improved by a factor of two to three in glass-reinforced compounds.

The insulating and other electrical characteristics of polycarbonate are excellent and almost unchanged by temperature and humidity conditions. One exception is arc resistance, which is lower than that of many other plastics.

Considerations
Polycarbonates are generally unaffected by greases, oils and acids. Nevertheless, compatibility with specific substances in a service environment should be checked with the supplier. Water at room temperature has no effect, but continuous exposure in hot water causes gradual embrittlement. While the resins are soluble in chlorinated hydrocarbons, they are attacked by most aromatic solvents, esters and ketones which cause crazing and cracking in stressed parts. Grades with improved chemical resistance are available and special coating systems can be applied to provide additional chemical protection.

Versatility in plastics
The extensive range of premium quality plastic materials available today provides the opportunity to create exciting and diverse projects for recreation. From polycarbonate sheet in a range of solid, profiled and multi-wall products, to a variety of matt, gloss, composite and anti-static foam PVC sheet, to solid acrylic sheet and opaque, flat polycarbonate sheet, the possibilities are limitless!

Polycarbonate in particular is an extremely versatile product. Solid, flat polycarbonate is easy to mold, which made it the ideal material for reproductions of an American classic, the world-famous Wurlitzer juke box. Created using solid polycarbonate sheet in 3 and 4 mm thickness, the polycarbonate was used to form the transparent casings of the juke-boxes. Using polycarbonate ensured that the casings retained their optical clarity of over 80 percent even after processing, with the added benefit of excellent fire rating ensuring the judeboxes were safe for use indoors. Polycarbonate can withstand a continuous service temperature of up to 100 degrees C (212 degrees F), can easily be thermoformed and fabricated, and can be worked with standard workshop equipment, ensuring a successful result for the Wurlitzer reproductions.

Polycarbonate's ease of fabrication also proved successful at a project on a slightly larger scale. The design for a football training academy for Glasgow Rangers Football Club was developed to ensure maximum natural daylight within and to enhance the internal environment and playing conditions. Conical roof structures at each of the two entrances, with an 8.4 m radius and 5.8 m radius respectively were double glazed using solid polycarbonate, allowing a flood of natural daylight into the entrance areas, transforming them into dramatic and bright spaces. Polycarbonate's ability to be cold-bent on site or pre-formed beforehand made it ideal for use in the domes, combined with its impressive impact resistance up to 200 times that of glass with only half the weight.

Another feature of the training academy is a large, 5.8 m wide x 47.8 m long glazed vault rooflight, again produced using solid polycarbonate sheet. It was created over the indoor pitch, to give a high volume of evenly spread direct natural light and provide a good playing environment. Polycarbonate is available in a wide variety of tinted options and this also proved useful, as care was needed to achieve the right combination of natural light into the building without glaring brightness. The designers also wanted the rooflight to tone in with the exterior envelope, so they used a combination of a 6 mm thick clear outer skin and 3 mm thick bronze inner skin to achieve the perfect result.

Similarly, Manchester City Football Club utilized two forms of polycarbonate to create the perfect stadium. The club started the 2003-2004 football season in a new L135 million state-of-the-art stadium, after moving into the City of Manchester Statium from Maine Road. Built originally for the 2002 Commonwealth Games, some major re-working of the stadium was completed before it was ready for the football club. This included finishing the unique "bowl" design of the stadium and fully completing the curving canopy over the seating. The front third of the canopy, approximately 1,500 linear meters, is produced from profiled polycarbonate, profiled to match the metal sheet that forms the remaining two-thirds of the roof. The 1.5 mm thick transparent sheets were specially manufactured to accommodate the curvature of the canopy through three planes, whilst still allowing easy on-site installation into the roof support system.

Profiled polycarbonate can be supplied with co-extruded UV protection which not only cuts out 98 percent of harmful UV but also offers a guarantee of continued performance in prolonged outdoor exposure, making it the perfect option for recreational stadiums. As with all forms of polycarbonate, it provides superb optical clarity, high impact resistance and can withstand temperature extremes without any significant deterioration of its mechanical or physical properties. Clear and tinted forms will also allow either maximization or control of light transmission. Good workability combined with impressive durability and excellent fire performance creates a highly versatile sheet.

Below the roof, solid polycarbonate with double sided co-extruded UV protection was used as a clear vertical glazing material to produce a visual separation between the stadium walls and the canopy, giving the effect of the canopy being suspended and floating. The polycarbonate creates a wind break and supplies weather protection to the spectators while still allowing air to circulate.

Profiled and multi-wall polycarbonate are used extensively in parts of the world where skin cancer is a problem. As strong, lightweight materials, they are ideal for glazing a huge variety of canopies, from simple lean-to structures to much more complex pitched roofs. Cutting out 98 percent of harmful ultraviolet radiation, they allow people to enjoy the sun while minimizing the associated risks.

Multi-wall polycarbonate is also ideal for a range of leisure applications, including swimming pool covers, conservatories, outdoor shelters and walkways. This remarkable insulating material provides a range of insulation options and is a highly efficient means of preventing heat loss, while tinted options also offer solar control and can reduce heat build-up in hot climates.

Polycarbonaate is an outstandingly versatile material, being used in applications as diverse as international stadiums and jukeboxes. It holps people make the most of thieir leisure time in a huge variety of ways.

For more information, contact Mike at Ultra Acrylics, Inc.

Introduction to Polycarbonate
Polycarbonates (PC) are high-molecular weight, amorphous engineering thermoplastics that have exceptionally high impact strength over a wide temperature range. Polycarbonate resins are produced in the U.S. principally by General Electric Co (Lexan) and by Bayer Corp. The Dow Chemical Co. has recently become the third producer of polycarbonate resins.

The resins are available in general-purpose molding and extrusion grades and in several special grades that provide specific properties or processing characteristics. These include flame-retardant formulations, grades that meet FDA regulations for parts used in food-contact and medical applications, blow-molding grades, glass-reinforced grades for applicatons requiring maximum strength and stiffness, and structural-foam grades. Polycarbonate is also available in extruded sheet. The natural resin is water-clear and transparent.

For more information, contact Mike at Ultra Acrylics, Inc.

Steps to choosing the right masking
There are generally five steps purchasing managers should use to choose the right masking for their fabrication operations. Nearly every acrylic fabrication job will require some sort of cutting or shaping. Purchasing managers need to know what these cutting operations are and how they affect the masking buying decision. They need to know if the acrylic sheet will be thermoformed. What type of finishing operation will be required to complete the part is an important consideration. Other aspects to consider when buying acrylic sheet is its expected shelf life and product availability, and finally the actual cost of the masking product should be used to balance the purchasing equation.

Cutting acrylic sheet
Gang cutting square and rectangular shapes is very common and can determine the efficiency of a job. Mono films don't generally perform well in this area, often times welding together or delaminating. Paper masking can result in gumming and premature tool wear, while multi-layer corona treated and PMR masking work very well. CNC routers will cut any of these products, but paper masking may shred, and mono films may delaminate and wrap the tool.

Thermoforming
Paper masking and mono films must be removed before thermoforming. This may actually result in increased damage and expensive post-cleaning operations. PMR works very well in shallow draw and line bending applications while multi-layer poly masking shines, allowing deeper draws and intricate shaping.

Finishing
Finishing methods can be an important consideration when choosing the right masking for a fabrication job using acrylic sheet. Operations such as flame polishing, gluing, sanding and joining all have different affects on masking. For instance, flame polishing will create problems for processors who use poly masking. The masking has a tendency to melt and char along the edge. PMR, however, may be used for these type of operations with proper preparation. Mono films may feather when used on joiners, or melt when sanded mechanically, thus fabricators can expect better results with PMR and multi-layer poly.

Shelf life
Purchasing must decide whether to consider shelf life as part of their decision making process. Many masking products are adversely affected by time and ambient conditions such as humidity and temperature. Paper masking is the most vulnerable product to these ever-changing conditions becoming more and more difficult to remove as shelf life and exposure increases. Corona treated poly masking on the other hand may actually disipate over time, becoming looser. PMR and multi-layer poly masking are not affected by these conditions and do not experience degradation, providing managers with flexibility and security.

Price
Paper masking has historically carried a premium due to its high cost. In some cases, paper masking cost to serve is 10 times that of poly masking limiting the use of the product. Acrylic sheet manufacturers have long recognized this disparity and have worked closely with masking vendors to engineer products which are not only more affordable, but are also designed to provide better performance to fabricators and distributors. Multi-layer poly and PMR are examples of this effort to deliver higher value to the customer. So while price is important, purchasing managers should also consider the additional value masking may play in the overall operation.

Conclusion
Fabricators no longer view masking as simply a protective cover, necessary but annoying, but now understand that the special characteristics and attributes of today's engineered products can add value to their operation by reducing labor costs, improving yields, and providing flexibility which was not available to them a few short years ago. PMR has emerged as the leader in this quest to improve the value to end users.

The technology used to develop MPR is the forerunner of new and exciting masking products which promises to one day simplify the selection process and actually consolidate these characteristics into a single package. Get ready for the next generation of masking!

For more information, contact Mike at Ultra Acrylics, Inc.