PAGE 1 OF 9 Synthetic turf is gaining traction in the global marketplace as an environmentally sound, safe and low-maintenance alternative to natural grass. In 2011, the Synthetic Turf Council estimated that there are more than 6,000 synthetic turf playing fields in the U.S., and turf is used by more than half of all NFL teams. And, in Europe, the International Federation of Association Football (FIFA) has financed more than 150 synthetic turf soccer pitches since 2003. The reasons for the increased popularity are vast, including an expanded global interest in reducing human impact on the environment. Depending on variables, such as temperature and climate patterns, a full-sized synthetic turf playing field can save anywhere from 500,000 to 1,000,000 gallons of water each year. Decreased maintenance is also a factor, saving lawn mower gas and its subsequent emissions, as well as labor. In fact, synthetic turf can be used for around 3,000 hours with rest, which is more than three times that of natural grass. Because of these benefits synthetic turf is w thought of for more than just playing fields. Golf courses, businesses, playgrounds and even homeowners are turning to this low-maintenance, environmentally sound lifestyle. When looking at the quality of a synthetic turf playing field, there are three primary factors evaluated to determine the overall performance: ball/surface interaction, player/surface interaction and durability. For the purpose of this paper, we will focus on weathering and its impact on the durability factor in synthetic turf. The Impact of Geography on Durability Most turf playing fields are warranted by the manufacturer for between eight and 10 years, and this includes a guarantee against color fading. However, climate can have a great influence on the longevity of the turf system. Specific parameters that affect weathering performance include: Radiant energy from sunlight A broad range of fluctuating temperatures Humidity Oxygen (oxidation) Rainfall and condensed moisture in the form of dew Particulate and gaseous contaminants Stress (wear) For example, a playing field in Arizona with annual averages of 34 percent relative humidity, 401 mm of rainfall, 22 C ambient temperature and total solar radiation of 7453 MJ/m 2 will weather at a faster rate than a field in the Netherlands with a significantly higher rainfall and humidity and lower ambient temperatures and total solar radiation.
PAGE 2 OF 9 Global Climate Weathering Sites 2010 Source: Atlas Material Testing Techlogy LLC (Fig. 1) Location Relative Humidity % Rain Fall mm Ave. Ambient Temp. TSR 300-2450 nm Direct Exposure MJ/M 2 Industrial Pollution Arizona, USA 34 401 22 7453 Miami, USA 77 1405 23 6198 Chennai, India 75 1667 28 6559 t monitored Netherlands 80 704 10 3858 Sanary, France 58 575 14 5412 yes Guangzhou, China 79 1492 22 4590 yes Choshi, Japan 78 1682 14 4659 t monitored Singapore 84 2300 27 6030 t monitored Melbourne, Australia 62 650 16 5385 Townsville, Australia 70 937 25 7236 Sochi, Russia 77 1390 14 4980 yes Stress consists of freeze/thaw traffic patterns, and effects from wind. Weatherization Testing for Synthetic Turf There are two ways of testing how synthetic turf will withstand the elements. First, outdoor weatherization, which involves subjecting test samples to prolonged, real-world exposure to light, moisture, and fluctuating temperatures. For the most comprehensive results, two or more test locations should be selected with extreme variances in exposure. Only by using outdoor testing can one get a real sense for how the turf will weather in an actual application. The primary drawback for outdoor testing is the time it takes to achieve actionable data. With the average warranty coverage for fading at eight or more years, outdoor weathering should be at least as long, if t longer. As a result, many companies opt to rely on the second means of testing, accelerated weathering using one of two accepted test methods: ISO 4892-3 using a QUV weathering tester or ISO 4892-2 using a xen arc weatherometer. For the most comprehensive results, turf producers should conduct both indoor and outdoor testing on products to ensure optimal quality and durability. Using this data in product development can help them better predict the product s lifespan under various climate conditions, make necessary adjustments to the product design and, thus, reduce costly warranty claims that often result in the complete replacement of the playing field.
PAGE 3 OF 9 Accelerated Testing Methods The principle behind accelerated testing is simple. Essentially, we are asking the question: how many hours of labsimulated weatherization will it take to expose the turf product to eugh UV light to equate to one year outdoors in a certain global area? Of course, the answer to this question varies depending on regional climate variances (see Figure 1). The ultimate goal remains the same, however: determining how these environmental conditions impact the color, appearance and physical properties of the turf product. There are several accepted test standards for determining the duration and extent of exposure to light, dark, moisture and temperature, among others, necessary to simulate real-life conditions. The standards include those outlined by FIFA, which is commonly used among global synthetic turf producers. The FIFA Procedure for Artificial Weathering (FIFA Test Method 10), outlined in the May 2009 FIFA Quality Concept for Football Turf: Handbook of Test Methods, dictates that the weathering cabinet, or QUV chamber, feature UV-A 340 nm lamps in accordance to ISO 4892-3 with periodic lamp replacement to obtain uniform exposure of all specimens to UV radiation and temperature. The procedure also dictates an exposure of 4896 ±125 MJ/m 2, which according to the Handbook, will take approximately 3,000 hours. However, companies that rely on this test standard alone using ISO 4892-3 (QUV) test methods, will likely come up with flawed results because of a miscalculation. A 300-400 nm lamp calibrated at 0.83 W/m 2 at 340 nm, yields 0.163 MJ/m 2 /hour which calculates to more than 30,000 hours to achieve 4,896 MJ (t 3,000 hours). The key piece of data to calculate this is the integrated irradiance when running at 0.83 W/m 2 at 340 nm. This is 45.2 W/m 2 from 300-400 nm. See FIG.2. From here, you multiply by time. 1 watt = 1 joule/second 45.2 W/m 2 x 3,000 seconds in an hour = 162,720 joules 16,270 joules = 0.163 MJ (mega joules per hour) Note: This information was supplied by technical staff from Q-Lab Corporation Further, QUV test chambers only take into account UV solar radiation. The theory is that only UV will break down the polymer, which simply is t the case. Polymer properties can be affected by both visible light and infrared light, both of which are part of natural sunlight.
PAGE 4 OF 9 Test Standards for Synthetic Turf Irradiance/Wavelength Chart from Q-Lab (Fig. 2) 1.2 1.1 1.0 SUNLIGHT.9.8.7.6.5.4 UVA-340.3.2.1.0 250 280 310 340 370 400 Wavelength (nm) Relying on the FIFA standard and ISO 4892-3 (QUV) test methods alone can result in a gross miscalculation of how the turf product will weather over time and consequently can mean a higher number of warranty claims due to the product t performing up to expectations. Alternatively, test standards, such as the German DIN 18035-7, using the ISO 4892-2 (xen arc) test method, takes a more comprehensive approach with the inclusion of total solar radiance (TSR), which encompasses near IR, UV light and visible light, as well as 18 minutes of water spray every two hours to simulate rainfall and the subsequent dry-off period. This simulated rainfall is an important element of the test because it is more akin to real-life rain than the condensation method used in most ISO 4892-3 (QUV), which can cause low-molecular weight components of the polymer, such as UV stabilizers and antioxidants, to migrate and wash away causing flawed results. Using the xen arc weatherometer, technicians are also able to more tightly control relative humidity.
PAGE 5 OF 9 Comparison of Accelerated Tests (Fig. 3) IRRADIANCE ISO 4892-3 QUV 0.83 W/m 2 at 340 nm IRRADIANCE ISO 4892-2 xen 0.50 W/m 2 at 340 nm LAMPS UVA 340 (295-385nm) FILTER COMBINATION Borosilicate in /out (290-800 nm) BLACK PANEL TEMPERATURE 65 C CHAMBER TEMPERATURE 50 C on light & dk. cycle CHAMBER TEMPERATURE 45 C LIGHT/DARK CYCLE 8 hrs. UV / 4 hrs. dark RELATIVE HUMIDITY 50% LIGHT/DARK CYCLE Continuous UV SPRAY Condensation on dk. cycle SPRAY 18 min. front spray every 2 hrs. While the benefits are great when using the ISO 4892-2 (xen arc) test method, many companies opt to use ISO 4892-3 (QUV) instead due to costs. However, as outlined above, the most accurate and actionable data on the durability performance of synthetic turf is achieved by using a combination of xen arc accelerated testing and real-life outdoor weathering. Using Kilo-Langleys to Design Synthetic Turf Products Kilo-Langley (kl) is a unit of measure for penetrating radiation, or irradiation energy. The earth is exposed to a minimum of 60 kl (arctic regions) to a maximum of 220 kl (Sahara Desert) of solar irradiation each year. Rainfall and elevation affect the amount of solar irradiation in a given area. For example, the higher the elevation, the greater the total solar irradiation will be.
PAGE 6 OF 9 NASA Global Solar Irradiation for 1 Yr. (In Kilo-Langleys) (Fig. 4) Geographic areas in which most sports fields are built (U.S., Europe and Asia) will fall between 100 and 160 kl. By kwing the kl exposure of the geographic area, the lamp being used (340 nm or 420 nm in Figure 5), filter and the lamp calibration, which is dictated by the chosen standard procedure, one can easily calculate the total number of hours the sample should be tested using a xen arc weatherometer to simulate one year of solar irradiation. This indicates that for 120 kl s, using ISO 4892-2 conditions, we need to weather samples for 1,403 hours. Kilo-Langleys Source: Conversion Table - Q-Lab (Fig. 5) Enter exposure in kilolangleys here: 120 Conversion to joules (300-3000 nm) 5,020,800,000 joules 5,020,800.00 kj 5,020.80 Mj Conversion to joules (300-800 nm) 2,701,190,400 joules 2,701,190.40 kj 2,701.19 Mj Enter Q-Sun Set Point Here: Can be a 340 or 420 nm set point check appropriate column for correct time of exposure 0.50 W/m 2 Filter Extended UV Quartz 340 nm Conversion Factor 340 nm control point: Time in hours 420 nm Conversion Factor 420 nm control point: Time in hours 1,752.7 1,591 883.3 3,158 Extended UV Q/B 2,100.0 1,328 863.0 3,232 Daylight B/B 1,988.6 1,403 877.0 3,181 Daylight Q 2,132.9 1,308 884.3 3,154 Window Glass B/SL 2,349.8 1,187 875.5 3,186 Window Glass Q 2,255.4 1,237 840.2 3,320
PAGE 7 OF 9 ISO 4892-2 Tests Hours 60-180 kl Range (Fig. 6) Kilo- Langleys per yr. Hrs. with daylight B/B filter Kilo- Langleys 10 yr. Hrs. for 10 yr. 60 701 600 7010 80 935 800 9350 100 1169 1000 11690 120 1403 1200 14030 140 1636 1400 16360 180 2104 1800 21040 Based on these calculations and their subsequent testing, some companies are so confident in the weatherability and fade resistance of their products that they are providing a written UV-guarantee on filament yarn spun with the custom-color masterbatches made specifically for the demands of synthetic turf applications. Warranty Based on Kilo-Langleys (Fig. 7) Some companies are giving a written UV-guarantee on filament yarn, spun with their stabilized custom-color MB s for turf. This translates to 14,030 hours under ISO - 4892-2 for PE and 11,452 hours for PA. Up to 10 years lifetime for PE - 10 years for areas < 120 kl/y - 9 years for areas < 140 kl/y - 8 years for areas < 160 kl/y - 7 years for areas > 180 kl/y Up to 8 years lifetime for PA - 8 years for areas < 110 kl/y - 7 years for areas < 140 kl/y - 6 years for areas < 160 kl/y - 5 years for areas > 160 kl/y
PAGE 8 OF 9 The Nature of Polymers Now that we ve explored best practices in weatherization testing, we will shift the focus toward how processing and the polymer s makeup affect the long-term performance of synthetic turf products. According to the Grotthus-Draper Principle of Photophysics and Photochemistry, adsorption of radiation by any component in the turf system can cause that component to degrade over time. It s a case of cause and effect. Preventing the cause (adsorption of radiation by the polymer) will prevent the effect (degradation of the system). By nature, all polymers absorb radiation, and can be divided into two groups: 1) Polymers that absorb radiation through impurities. By definition, an impurity is anything that impairs the purity of something. In the case of polymers, impurities can occur when the colorant and the polymer are melted together during the extrusion process. For example, processing temperatures that are too high will degrade components and open the door for radiation adsorption through impurities when exposed to sunlight. Consequently, temperatures must be closely monitored lot-to-lot to ensure the consistency and performance/weatherability of the product. 2) Polymers that are built from momers having chromophoric properties. Chromophores, such as aromatic rings, are chemical structures that absorb light to produce an effect, such as a color. The presence of chromophores in polymers will cause intensive absorption of UV light, and will have negative effects on the performance of the product. In either case, extruders should t only look at their own processes, but also the processes of their suppliers. How colors are corrected and compounded and at what temperatures can have an effect on performance. Material and process quality should be monitored the entire way through the supply chain to achieve the best results. Americhem A Partner in Superior Synthetic Turf Products If all polymers inherently absorb radiation, then it stands to reason that all polymers will need to be modified to withstand weathering including polypropylene and linear low-density polyethylene (LLDPE), which are most commonly used in synthetic turf applications. You have to do something with the energy caused by solar radiation.
PAGE 9 OF 9 Fortunately, great strides are being made by suppliers, such as Americhem, to create solutions that help synthetic turf products last longer, while reducing fading caused by sunlight. In 2012, the company introduced a comprehensive turf package called nfinity, which includes these necessary elements for ensuring the long-term durability of synthetic turf products: Color Masterbatches Americhem provides a full range of custom and standard colors that offer superior colorfastness with the assurance of lot-to-lot consistency. The company has embarked on extensive color testing projects in both indoor and outdoor applications to continue to develop new color techlogies specifically for synthetic turf. The company is also in the process of compiling a weatherization book that shows how standard colors weather differently over time based on a multi-year R&D study. UV Stabilizers Americhem includes its leading UV stabilizing masterbatches in every turf package. Its UV stabilizers provide enhanced performance for synthetic turf applications through outstanding resistance to sunlight and product consistency that meet rigorous quality control standards to extend the life of turf products. Antioxidants Oxidation caused by the process through which turf is made, can degrade components of the system and compromise the long-term performance of the end product. Americhem s antioxidant additives effectively limit oxidation for superior results and can be combined with color or used as stand-alone products. Americhem s Product Development Services Americhem is more than a supplier to the turf industry we re a partner that can help enhance your existing products and bring new products to market faster. We become fully integrated in your processes to help improve efficiencies and overall product quality. Americhem s Analytical Capabilities There is a strong need for analytical testing in growing industries such as synthetic turf. Much of this testing, from quality assessment to product analysis, is done in-house by Americhem s central analytical department. Many times, we provide solutions using decades of technical expertise and equipment in our own lab. We are connected to many outside testing facilities that offer an even broader range of very fine analyses. For more information on best practices in the manufacture of synthetic turf, or to learn more about Americhem s products and services, visit www.americhem.com.