• Mon. Jun 24th, 2024

Non-filled research developments update

linear friction tester

The European Commission has (almost) spoken. Now the race is definitely on: the development of a synthetic turf system that, preferably, doesn’t require any infill to perform. My previous article focused on the development of the product. In this article, I’ll update you on what is happening on the research and legislative side.

As explained in this article, there are several reasons why non-filled synthetic turf has become a major focus. This focus first gained traction in 2018 when health issues that had possibly been caused by crumb rubber (SBR) infill were thrust into the spotlight, followed by fear of microplastic pollution caused by polymeric infill particles outside the field perimeter. While the first claim has yet to be proven convincingly (to ban the use of SBR), the second claim motivated the European authorities to now propose a ban on the selling of any polymeric infill that measures 1nm≤x≤5mm. Details about the proposed ban and timeline you can read here.

(Unnecessary) sudden focus

Once the penny dropped, stress levels for tufting companies, contractors and the various football governing bodies jumped up a few notches when they realised that the future of synthetic turf was hanging in the balance. Things cooled down only once they realised that at solution had, in fact, been around all along. Parallel to the development of so-called third-generation synthetic turf in the early 2000s, one company had also developed a densely tufted carpet that didn’t require any infill to still accommodate a game of football in accordance with the stipulated requirements for the surface. By the time the concept was officially viewed as the solution, it had been installed in close to 200 clubs around the world. Some of these installations had even been issued with a FIFA One-Star or FIFA Two-Star, or the successor of the FIFA ‘Star’ programme, a FIFA Quality or FIFA Quality Pro certificate that recognised its compliance to the quality criteria that had been defined for these standards. The industry went into a frenzy, with many establishing a research programme dedicated to non-filled synthetic turf1&2.

Skin injuries

In December 2018, FIFA3 suddenly ruled these systems to be more abrasive to the skin. All certificates that had been issued to non-filled synthetic turf installations that had been tested in accordance with the 2015 Handbook of Requirements version 2.5 or older, were revoked. An updated version of the handbook is scheduled for release only in early 2024. Whether this version will include an improved skin friction/skin abrasion test remains to be seen for now. FIFA is hoping it can benefit from research done by test institute Sports Labs as part of a World Rugby project2. However, World Rugby has scheduled the release of their details later next year. FIFA will continue to adopt the current test method to assess skin injury risk and are yet to confirm if they will utilise World Rugby’s test method.  Asked for an update for inclusion in this article, Sports Labs project leader Max McFarlane told Sportsfields.info: “Compared to filled samples, non-filled surfaces generate minimal abrasion on skin. This suggests that the infill is what causes the skin damage. However, the non-filled samples produce greater results from the accelerometer data, implying there is still a risk of injury.” Sports Labs managing director, Eric O’Donnell, adds: “We still have to do high temperature testing on these surfaces. So, at this time, we do not have the full picture of the impact of temperature on skin injuries as regards these surfaces.” The heat test has been scheduled for a later time.

linear friction tester


McFarlane points out that “The lack of infill, which acts as ‘ball bearings’, means the simulated player is effectively sliding over a polymer sheet. However, it is hard to say what would happen to a player’s skin as I haven’t found any data on skin injuries on non-filled samples.” Sliding and slipperiness on non-filled synthetic turf is one of the reasons why the Dutch FA (KNVB) has decided to take back control over researching the surface for the Dutch market. At present, some 20 non-filled synthetic turf systems from four different suppliers have been installed in a country with the highest synthetic turf density in Europe. “As owners of the fields were experiencing trouble in collecting feedback from users, we commissioned a study whereby games in wet or damp circumstances were recorded and analysed by a specialist in human movements for the University of Amsterdam. One of the things we noticed was that on a wet or damp non-filled synthetic turf surface and non-filled turf systems with mineral infill, a player slips or falls frequently,” Patrick Balemans of the Dutch FA (KNVB) explains. The incidents recorded were divided over 10 different categories, ranging from slipping while running (with or without the ball), slipping while shooting or passing to slipping while receiving the ball. “This evidently shows that the surfaces that are currently vying for a non-filled classification in the Netherlands, do not provide enough stability to the player and are still to slippery to play on in “wet” conditions.”

Testing devices

At the recent AMI Conference in Madrid in March this year, Loughborough University presented improved versions of the Artificial Athletic Athlete (AAA) test device as well as the Rotational Resistance Tester (RRT). It has been proposed to, in the future, call the latter the Rotational Traction Athlete (RTA). The proposed RTA considers the peak torque, rotational shear stiffness and rotational velocity experienced in the test. For the AAA, new algorithms for deformation and energy calculations will be proposed that will include the shock absorption (in percentages), the peak deformation (in mm) as well as the energy return (in joules). Instead of taking the average of three drops, measurements will now be taken from a single drop. It is likely that these devices will be included in the upcoming FIFA Handbook of Requirements3. Meanwhile, Dutch test institute Kiwa ISA Sport has developed a device to establish the linear grip on a synthetic turf surface. “A motor pulls a studded trolley over the surface and the force this requires is measured to determine the linear friction experienced,” explains Gert-Jan Kieft of Kiwa ISA Sport. Both the trolley and speed can be adjusted to represent different types of players or age categories. “We used video analyses to replicate player movements. The device is now being reviewed by the Technical University Delft to improve its ergonomics.” 


While FIFA has revoked all certificates issued to non-filled systems pending the introduction of, and verification by a new test procedure, the Dutch FA has granted the 20 ‘non-filled’ fields that have been installed the Pilot-status. This allows the market to use such fields under strict conditions. Of the systems currently being trialled, only one has managed to meet the set requirements. This happens to be a system that uses mineral infill and, as such, does not comply with what both the Dutch FA as well as FIFA, regard as a non-filled system1. The Dutch FA has now decided to review its Pilot-conditions and the technical specs it accepts for products. “Together with the association that represents the municipalities (VSG), we have come to the conclusion that the pilot-requirements will have to be adjusted in order to meet the requirements set by the owners and users for such field,” Patrick Balemans says. VSG and KNVB will now focus on defining technical specs like the free-pile, maximum quantity mineral infill allowed, pile-density, etc. “This is to ensure that non-filled synthetic turf remains a system without any infill instead of becoming, what has historically been called, a sand-dressed system.”

Improve perception

The requirements Balemans is alluding to, were partly established with the input of a perception study for non-filled synthetic turf systems. “In 2021 we were approached by the Dutch FA with the request to establish why many people were complaining about non-filled synthetic turf systems, despite these fields complying with the requirements that were set at the time,” says Julie de Vaan of Changing Ways, the company that conducted the study. In addition to a literature study, de Vaan and her colleagues also interviewed various stakeholders and distributed questionnaires to members and officials of eight clubs where a non-filled synthetic turf pitch had been installed. “Altogether we received 145 responses, a number we deemed as being too small to draw real conclusions.” However, the one firm statement she dares to make is that top players tend to be better able to play on the surface. “The response we received indicates that the ability to ‘control’ (the ball and/or the body) is very important to the player. Players playing in top teams are usually better at controlling the ball or their movement.” Ironically, the Dutch FA currently doesn’t allow the use of non-filled surfaces for games in the top leagues pending a review that is scheduled for February 2024. “The comments or complaints voiced by top-players can be detrimental to the development of the product,” Balemans explains. Past experiences in the English Football League First Division, the predecessor of the current Premier League, serve as a perfect reminder. The outcry caused by the bad experiences on the sand-dressed synthetic turf surface some of the stadiums had installed in the 1980s is blamed for the reason why professional players (worldwide) to date still object to playing on these products.

Use all buttons

One of the recommendations de Vaan made in her study is to use all buttons to improve the perception of (non-filled) synthetic turf. “The industry is doing a lot to improve the product but it is also important to consider the attitude, expectations and related experiences of the club, the target group as well as other stake holders.” A well known example is that teams that have won tend to be more positive about the surface. “Virtually all respondents to our survey mentioned the slipperiness of the surface and the uncomfortable feeling they got from performing movements that experienced a higher body-surface contact than usual. Most of them feared abrasions or injuries. However, less than 50% knew the difference between a filled and non-filled synthetic turf surface, which shows that there is still plenty of space to educate the user.”

While much has been done ever since the international football fraternity realised that synthetic turf for football had hit a roadblock, things haven’t really progressed much in the outside world.

As discussed in this article, FIFA has sent its Innovation Partner Vivaturf back to the drawing board to come up with a revised non-filled synthetic turf concept. The Dutch FA has opted to review the criteria that define non-filled synthetic turf, while the industry has been leaning on both FIFA and the Dutch FA to also include long-pile synthetic turf surfaces with only mineral infill in its definition of ‘non-filled synthetic turf’. The future will tell which approach will yield the best result. Meanwhile, the need for an alternative for synthetic turf surfaces with (polymeric) infill that requires less maintenance and will produce less pollution, is fast approaching.

1 Read more in the Non-filled section of our library

2 Read more in the Testing & Quality section of our library

3 Read more in the Governing bodies section of our website

Guy Oldenkotte

Guy Oldenkotte is senior editor of sportsfields.info and has been covering the outdoor sportssurfaces market and industry since 2003

Leave a Reply