Artificial Turf Field

Constructing an artificial turf field involves a large startup cost. This is because the following components are involved

Pile Fibre - the synthetic grass is made of either the polyamide nylon/nylon 6.6 or polypropylene/polyethylene, which is then custom extruded into a monofilament ribbon form. The pile fibre has to allow for smooth ball roll and bounce, support non-directional foot traction, allow for water permeability, and have the correct balance of strength, elasticity and stiffness to withstand the wear and tear of regular usage.

Backing Fabric - the material to which surface fibres are attached to form the underside of the artificial turf surface. The backing is typically fabricated from polyester tire yarns.

Using flat-bed Raschel knitting machines, the nylon pile fibers are knitted directly into the backing as it is being fabricated, to form a mechanically strong and stable structure. The knitting machines are between 4.5 m to 5 m wide, to minimise the number of seams and offer greater surface uniformity in each installation.

The sewing threads are high-strength, weather resistant and pigmented to exactly match the color of the turf. Permanent lines are knitted in during the manufacturing process, to minimise maintenance. The backing has to permit water to flow through the fabric readily.

Shock-Absorbing Foam - provides cushioning for running or falling athletes. The foam is made of a closed-cell polymer alloy like polyurethane, typically 1/2 inch in height, and perforated for vertical drainage.

Supporting Base - supports the load placed on the entire structure, typically a 2-foot or 3-foot layer of asphalt or concrete. The sub-base should be flat and even, and should be able to lose water easily.

Drainage - an artificial turf field has to be watered prior to play to reduce surface temperature, make the field less abrasive and generate smoother ball roll. Water pooling is prevented on the surface by means of a 0.5% grade slope drainage system.

Ultra-Violet Stabilization - all polymeric materials are subject to damage when exposed to the ultra-violet radiation present in sunlight. This problem gets more acute in areas with high humidity. Hence the pile fibres have to be protected by the inclusion of appropriate organic stabilizers or UV inhibitors. Similarly, coloring pigments have to be selected for their ultra-violet resistant properties, for best retention of their original colours when exposed to sunlight.

Technical Criteria

The International Hockey Federation publishes a handbook of performance requirements for synthetic hockey pitches (last revised March 1999). It lists acceptable ranges of values for the various components of an artificial turf field as detailed above. Some sample values are given below: Component Parameter Value Pile Fibre Ribbon Ends per Needle 12   Pile Height 12 mm - 15 mm   Pile Weight 1850 gm/sqm   Pile Ribbon Denier 415 Texturised   Filaments per Square Inch 1180   Abrasiveness Index 15 to 60   Resistance to Abrasion 4.0   Tensile Strength - Length 1700 N 30% (ISO 5081)   Tensile Strength - Width 1400 N 25% (ISO 5081)   Colour fastness 7 - 8 (DIN 54004) Backing Fabric Grab Tear Strength upto 350 pounds Shock-Absorbing Foam Shock Absorbency 75-105 Gmax (avg of 2nd/3rd drop) Completed Turf System Grade Slope < 0.5%   Water permeability 30 l / min / m   Shoe Traction (Dry) 0.90 to 1.50 Coefficient of Friction   Shoe Traction (Wet) 1.10 to 1.50 Coefficient of Friction   Ball Roll 5.4 - 8.2 metres