1 Overview of Artificial Turf Development

             Artificial turf is widely used in official playing fields of team sports such as American football, baseball, softball, hockey and rugby. In 1994, the World Baseball Association began to use artificial turf to undertake major events. In football, which has the largest audience in the world, FIFA and UEFA were the first to recognize that artificial turf can be used as an official competition venue, and encouraged important football clubs such as Real Madrid, Barcelona, etc. , Ajax and other football clubs adapt to the artificial turf playing field. Subsequent European Football Championships in Moscow and Francophnio World Football Championships in Spain also used artificial turf in the competition venues.

            In 1996, PA artificial turf was laid for the first time at the Astrodome Stadium in Houston, USA. In the following years, more than 2,000 artificial turf projects were implemented in North America, and nearly 3,000 pieces of artificial turf were put into use in continental Europe. For the development of artificial turf technology, ensuring the safety of the active crowd is the top priority. According to the applied research results of Canadian Fieldturf Company, compared with the safety performance of natural turf, the probability of muscle strain of athletes engaged in sports or competitions on artificial turf can be reduced by 74%, ligament tear can be reduced by 32%, and brain injury can be reduced by 32%. Reduced by 55%, neck damage can be reduced by 47%.

            In terms of environment and landscaping, artificial turf can be used in airports, apartments, office buildings, retail stores, hotels, gas stations, churches, parking lots, public buildings, swimming pools, commercial areas and entertainment venues, etc. The service life of artificial turf used for environmental landscape purposes is generally 8 to 12 years. According to Fieldturf’s experience in implementing 15,000 artificial turf projects, the use of artificial turf can save more than 70% of water compared with conventional natural turf. The return on investment of artificial turf projects is also very satisfactory. Among them, the return rate of landscaping projects is 100% to 200%, the return rate of kitchen facilities is 75% to 125%, the return rate of bathrooms is 20% to 120%, and the return rate of swimming pools is 100% to 200%. 20% to 50%.

            When people watch live TV programs such as football, tennis, hockey, etc., the color and appearance of artificial turf have also achieved great success in visual effects. At this time, in the European market, polyolefin artificial turf mainly made of PE and PP Yarn has also formed an industrial production scale. Following the fibrous flat filament lawn, special-shaped monofilament lawn yarn, two-component or three-component lawn yarn with diamond shape, flat shape and low-waist triangular cross-section also entered the market one after another. In recent years, the elastic recovery rate, fiber surface properties and biomechanical properties (Biomechanical) of artificial turf yarns have all made significant improvements.

            Artificial turf does not require mowing and trimming, nor does it require irrigation water. Fiber, backing and padding from used turf are 100% recyclable. At present, the research and development, production, quality inspection, installation, maintenance and waste turf recycling of artificial turf have formed a complete industrial chain. Therefore, artificial turf not only has excellent performance, but also has the characteristics of environmental friendliness.

           Good performance and environmental friendliness have promoted the continuous development of the artificial turf market. Fieldturf’s artificial turf projects have reached 15,000. The company’s aviation-grade artificial turf has been used in Hong Kong International Airport, San Francisco International Airport, Houston Airport and the US Naval Air Force Base. The artificial turf of the Dutch company TenCate has been used in the 2000 Sydney Olympic Games, the 2004 Athens Olympic Games and the hockey venues of the 2008 Beijing Olympic Games. In June 2009, the International Football Federation called artificial turf “the future of football” and was very optimistic about the construction of European sports facilities and the use of artificial turf in the world. Football is one of the sports with the largest participation and viewing groups in the world. It is a huge market for synthetic fiber turf products, and it is also a field with high technology content and high environmental friendliness requirements.

2 Production and technical characteristics of artificial turf yarn

2.1 Manufacturing process of artificial turf yarn

           Artificial turf yarn widely uses PE, LLDPE, HDPE, PP and PA as raw materials. Its processing process is mainly divided into four parts, namely, screw extruder and forming system, drafting zone, relaxation setting zone and winding device. Figure 1 shows the production process of artificial turf yarn.

           The artificial turf yarn used in official competition venues has strict quality requirements. Usually, the production equipment uses a Φ100 mm screw extruder, which adopts the form of double spinning components. The diameter of the spinning head is Φ425 mm, and the production capacity of the equipment is between 250 and 350 kg/h. The processing speed of the production line is 250-450 m/min.

           At present, the artificial turf twisted yarn can use the DD2000GT twisting machine of Oerlikon Barmag (Oerlikon Barmag), which can process PA, polyolefin turf yarn, etc. 70-250 m/min, the yarn twist can be controlled at 20-40 twist/m. In the production of twisted yarn, the DT660 twisting machine of Swiss Rieter company can also be used, the processing speed is 70-250 m/min, and the package weight of twisted yarn is 6 kg.

            Deformation processing generally uses lawn yarns of 8×550 dtex and 6×200 dtex. Raw yarns of 8×550 dtex and 6×2 000 dtex are mostly used when processing spiral-shaped covering yarns. The yarns used for spiral-shaped covering are mostly polyester DTY, and the number of spiral-shaped coverings of finished yarns can reach 30 to 55 pieces/ m.

             The weaving of artificial turf usually adopts tufting or woven process, while the turf “Elite” developed by Berkshire Company in the United States for hockey venues uses a knitting process.

             The American Polyturf XTP series tufted artificial turf used in official competitions uses 11 000 dtex PE monofilament turf yarn with a yarn thickness of 150 μm. The tufting process is as follows: the gauge is 0.5 inches, the number of turns per yard is 108 ± 10, the number of turns per square yard is 7776, the pile height is 60 mm, and the product weight is 147 kg/m2. The basic performance requirements of the artificial turf are: color fastness ≥ 7 (blue card), gray card ≥ 4, UV stability > 6 000 h, water permeability within ±15 gallon/(m2 • min).

2.2 Varieties and technical characteristics of artificial turf yarn

            The varieties of artificial turf yarn are in a diversified development trend, such as two-color turf yarn, single-color covered yarn, single-color textured yarn, double-color covered yarn, twisted yarn and textured covered yarn.

           The fineness range of LLDPE, HDPE and PP artificial turf yarns is between 1 000 and 2 000 dtex, and that of PA turf yarn is mostly between 500 and 900 dtex, usually 6 to 8 strands of single yarn are combined to form 6 600 to 12 000 dtex The finished yarn is used for the next step of weaving.

           Monofilament lawn yarn for environment and landscape, using PP or PE as raw material, single yarn denier of 1 100 to 2 000 dtex, yarn thickness of 110 to 150 μm, fiber cross-section is flat, lawn yarn specifications include 8 800, 11 000, 16 000 dtex etc. 3 types. This product is a two-color yarn with UV resistance.

           Monofilament lawn yarns in the sports field mostly use PP or PE as raw materials. The single yarn denier is between 1 100 and 2 000 dtex, the yarn thickness is 110 to 270 μm, the fiber cross section is diamond-shaped, and the lawn yarn specifications are 8 800/11 000/ 16 000 dtex. This product is also a two-color yarn with UV resistance.

          The flat yarns or split-film flat filament lawn yarns used in sports field lawns are mostly made of PP or PE, with a single yarn fineness of 5 500 to 20 000 dtex, a thickness of 60 to 110 μm, a rectangular fiber cross section, and a lawn yarn specification of 6 600 ~ 11 000 dtex. The product comes in pastoral or olive green and is UV resistant.

          The flat yarn or split film type flat filament lawn yarn using PP or PE as raw material is generally used for laying lawns on land. The single yarn denier is 5 500-11 000 dtex, the thickness is 60-110 μm, the fiber cross-section is rectangular, and the lawn yarn specification is 6 600-11 000 dtex. This product is also available in pastoral or olive green and is UV resistant. Table 1 is the quality index of artificial turf yarn for the competition field.

3 New progress of artificial turf and its fiber technology

         At present, the research and development of artificial turf fiber technology is entering an innovative period with polymer materials, artificial turf manufacturing process and fiber material biomechanics as the breakthrough point. The development of high-performance turf yarn with softness, high strength and long service life is the key to the survival of enterprises. and development needs. For example, Fieldturf regards research on new polymer materials, processing technology and fiber structure as the three basic points for enterprise development and market expansion. The new variety known as “innovative artificial turf yarn” developed by the company has the following characteristics: ① The raw material polymer has good tear resistance and degradation resistance, and at the same time, it has developed a resin product with super anti-ultraviolet function; ②Fieldturf cooperates with German Motor, a synthetic material processing enterprise, and adopts the latest precision extrusion forming system to ensure that the lawn yarn has good quality, that is, it gives the lawn yarn excellent strength and perfect fiber surface reflection characteristics; ③The new lawn yarn has The intricate and alternating concave and ridge surface structure improves the breaking point of the fiber and gives the fiber a natural grass-like style. It is expected that in the next few years, the market share of monofilament artificial turf yarn will grow rapidly.

3.1 Research on high-performance three-component monofilament lawn yarn

            Bicomponent spinning process is one of the most practical methods to improve the quality of artificial turf yarn. But in the drafting process of the composite yarn, the defect that the two polymer components are easy to peel off limits its wide application. For this reason, German Reimotec company has developed a three-component composite lawn yarn monofilament, which uses LLDPE as the cortex to make the surface of the monofilament have a lower coefficient of friction, and PA as the core layer, which can give the fiber the best bending recovery performance. The third component between the two basic components, that is, the adhesive layer, can significantly improve the peeling and delamination of the skin-core component, so that the elastic recovery and surface friction coefficient of the artificial turf monofilament can be balanced.

          With the development of nanotechnology, nanometer-sized powders can be added, aiming to realize the functionalization of lawn monofilaments and improve the anti-mold and flame retardancy of lawn yarns. The LLDPE with nano-silver active material is used as the skin layer, the core layer is supported by PA raw material, and the middle adhesive layer is added with nano-sized alumina active material. The fiber core part has two cavities. This functionalized nano-three-component monofilament is a new structural product for artificial turf yarn.

3.2 New artificial turf yarn

         Textured yarns and monofilaments with a special soft hand have become a new generation of lawn yarns. In recent years, one-step two-color yarns, monofilament lawn yarns with different cross-sections and various thicknesses have entered the market. The Czech Lanex company has developed a monofilament with a geometric cross-section for use as artificial turf yarn. For example, if LLDPE is used as raw material and diamond-shaped monofilament yarn with a single yarn specification of 200/1 100/1 375 dtex, usually 6 to 8 strands of single yarn are combined into 8 800 to 12 000 dtex lawn yarn for weaving. Rhombus lawn yarn has excellent vibration energy release function, and also has very good bending recovery performance.

         Tencate company in the Netherlands can provide special-shaped lawn yarn with PE as raw material, low-waisted triangle and flat middle bulge. The company’s product name is “Thiolon”, and the dynamic curl treatment (Dynacurl) PE series lawn yarn has the characteristics of water retention, UV resistance, excellent resilience and extremely low heavy metal content. It has been widely used in hockey venues. Table 2 is the performance characteristics of Thiolon artificial turf yarn.

         For artificial turf yarn, the anti-mold performance is a very strict indicator. Astro Company of the United States has developed a series of anti-mold turf yarn called “alphasan”. Harmless, but has broad-spectrum antibacterial function against microorganisms. The amount of “alphasan” antifungal agent can be adjusted according to the specifications and uses of the product.

          Astro has also developed artificial turf mold shielding technology called “Bio-shield”. This technology uses the mechanism that microorganisms cannot survive on the surface of crab shells, and makes chitosan from chitin in shrimp and crab shells, and then puts chitosan in weak organic acids to form a biological shielding agent “Bio- shield”. Applying the screening agent to the turf yarn can strengthen the artificial turf’s ability to inhibit the growth of bacteria, mold and odor. At present, this technology has been used in Astro’s three artificial turf yarn series.

3.3 Development of environmentally friendly artificial turf technology

3.3.1 Recycling technology of lawn yarn

          The development and use of artificial turf increasingly pay attention to its environmental friendliness. At present, artificial turf can be 100% recycled and reused. For example, Fieldturf has developed a technology specially used for the removal, collection and recycling of waste turf, and more than 4,000 artificial turf users in North America have been included in the use/repair/recycling Recycling system for reuse. The company also has a special factory engaged in the removal, collection, grinding and granulation of waste artificial turf, and finally processed into products, such as mats for storage, lining of highway storage barrels, handbags, etc., and put them on the market again.

3.3.2 Harmless lawn padding materials

          Lawn padding materials mostly use rubber pellets, sand or a mixture of the two. In view of the possible environmental hazards caused by the use of rubber materials, since 2005, research on pollution-free lawns has been carried out one after another. Using textured yarn or high soft turf yarn to make turf can reduce the amount of padding used. The new generation of “Xtreme” turf developed by Polyturf is a no-fill turf.

3.3.3 Complete recycling of artificial turf base fabric

          The American Envylown company has specially established the “Duraflo EEBS” system to carry out orderly recycling of the first layer of polyolefin base fabric and the second layer of PP spunbond nonwoven fabric, PU and other related thermoplastic materials in the artificial turf beyond the service life.

3.4 Artificial turf fibers produced from recycled bottle flakes

         The British Hitech Turf company uses lawn yarn made from recycled slices, namely the “HT” series of artificial turf. The lawn pile is 30 mm high. It is mainly used for children’s entertainment and pet activity venues, and its service life is about 5 years.

3.5 Serialization and quality certification of artificial turf products

          In order to meet and adapt to the user’s requirements to the greatest extent, both sports lawns and lawns for landscape decoration must require specialization of product specifications and performance.

           For example, the stability, sliding properties, friction performance with the skin, impact absorption and other indicators of the artificial turf products of the American Astroturf company all meet the requirements of ISO9001, and are recommended by FIFA as turf for official competition venues. Astroplay 3D/Z65X is a PA series artificial turf specially used for football; AstroturfNSF48/90 is a PA series artificial turf specially used for hockey; and Astroplay55N is a PA artificial turf approved by FIFA for amateur football schools and training grounds.

          Eagle’s Aqua Satia LSR series of artificial turf made of Tencate’s fibers has a pile height of 12 mm, which is specially used for hockey venues and has been approved by the World Hockey Federation (FIH). The XP Pro16 model product in the company’s Asi Court series of artificial turf has a pile height of 16 mm and is dedicated to tennis courts and has been approved by the World Tennis Federation (ITF).

           Eagle’s Eaglelawn series products are artificial turf specially used for landscape and environmental modification. The LXR polyolefin monofilament series of American Fake Company is specially used for artificial turf in residential quarters.

4 Cost-Efficiency Analysis of Artificial Turf

4.1 Benefit Analysis of Artificial Turf

           The daily use time of artificial turf is 40% longer than that of natural turf. It can be clearly seen from Table 3 that the annual rate of return of artificial turf is relatively high, which is about 2.5 times that of natural turf.

4.2 Comparison of maintenance amount between natural and artificial turf

            Relatively speaking, the maintenance workload of artificial turf is less, and there are only expenses such as labor costs, equipment depreciation and refinishing. Calculated on the basis of 8,000 m2, the annual maintenance cost is around USD 5,000. However, there are many maintenance items for natural lawn, and the workload is heavy, mainly including machinery and equipment (accounting for 13.5% of maintenance costs), manpower expenditure (11.4%), pruning costs (5.0%), fertilizers (9.2%), seed reserves ( 0.9%), remediation costs (5.5%), lawn grooming (18.2%), turf removal (0.4%), irrigation (1.6%), equipment depreciation and fuel (6.7%), water (10.3%), Peeling repair expenses (16.9%), the total annual maintenance cost is about 52,500 US dollars, which is more than 10 times that of artificial turf.

4.3 Cost Analysis of Artificial Turf

           Taking the 8000 m2 sports turf field as an example, the service period is 10 years, and the cost composition of artificial turf and natural turf is shown in Table 4.

4.4 Safety of artificial turf

         In order to obtain safe and high-performance artificial turf, the biomechanical properties (Bio Mechanical) of lawn yarn have been widely valued. From the perspective of sports medicine, the friction performance of artificial turf is the most suitable, and artificial turf also has a good release function for the torsional impact it bears. Therefore, as a competition turf, the probability of accidents for athletes, such as knee , ankle and other parts of the non-contact trauma can be minimized. The study also found that compared with natural turf, artificial turf has better shock absorption performance, which is one of the reasons why artificial turf has fewer sports injuries.

         Chose a special football field and carried out a three-year experiment on the use of artificial turf and natural turf. Judging from the results, the injuries of athletes have been significantly reduced: muscle injuries are reduced by 74%, trauma is reduced by 42%, ligament injuries are reduced by 32%, injuries caused by violent actions are reduced by 22%, impact injuries are reduced by 19%, contact injuries on the surface of football shoes 10% reduction.

         Coincidentally, a 5-year similar trial conducted by the company on another college’s football field also showed that using artificial turf, the chances of athletes’ brain and neck trauma were reduced by 47%, and the third-degree external injuries were reduced by 38%. Certain damage reduced by 55%.

          According to the NCAA Trauma Surveillance System of the United States, the injury probability of male and female athletes in colleges and universities was tested, and the results showed that: for female athletes, the probability of facial injury on artificial turf is 11.2%, while that of natural turf is 15.5%; for male athletes For example, the chance of facial injury on artificial turf was 6.6%, compared with 7.8% on natural turf.

5. Market development of foreign artificial turf

          It is estimated that the United States accounts for nearly half of the world artificial turf market, Europe accounts for 23%, China accounts for 10%, the rest of Asia accounts for 8.5%, the Middle East and India account for 10%, and Latin America accounts for 3%.

           The composition of the artificial turf raw material market is roughly as follows: PE accounts for 68%, PP accounts for 24%, and PA accounts for 7%.

           According to the application field, football fields account for about 51%, hockey fields account for 5%, tennis courts account for 2%, other sports fields account for about 4%, leisure lawns account for 33%, and lawns for landscape or environmental decoration account for 5%.

           In the 1970s, artificial turf made of polyolefins had formed an industrialized production scale in Europe. Some companies used the tufting process to make artificial turf with low pile height and used it in hockey venues, which is the second generation of artificial turf. . Due to the sliding properties of the surface of the flat grass yarn and the possibility of injury to the players in the quartz sand bedding layer, it is not used in football fields.

          In 1990, the third-generation artificial turf using PE as raw material appeared. The safety and usability of the lawn yarn have been fundamentally improved. The pile height exceeds 40 mm, and the padding material is expanded to rubber grains and sand grains. The improvement of the comfort and uniformity of artificial turf makes it have the conditions to enter the field of football.

          Since entering the 21st century, the progress of artificial turf production technology is mainly reflected in the following aspects: the softness of lawn yarn; the performance research of high-performance fibers; the development of new padding materials and non-filling turf; the establishment of 100% recyclable artificial Significant progress has been made in the sustainable production system of turf; the performance specifications and guidelines of turf products, and a new research method presents the basic characteristics of the fourth generation of artificial turf.

6 Conclusion

            Artificial turf and its fiber materials are products with high technical content and strict requirements on product quality, because it is directly related to the safety and health of athletes and other people engaged in sports activities.

            In recent years, the world’s artificial turf has made revolutionary progress in research on raw materials, processing technology and biomechanical properties of fiber materials, and has also shown certain market potential. This is undoubtedly an opportunity for the development of domestic artificial turf and fiber technology.

            Although the development of domestic artificial turf is not late, the current product quality and technical level are still low, and the operating conditions and technological development concepts are not very coordinated with the development trend of the fourth-generation artificial turf in the world today. Faced with the dual pressure of survival and market expansion, domestic enterprises must work hard on the research and development of high-performance monofilaments and strict quality management.