Category Archives: Ice Hockey Shielding
When talking to people about the advantages of polycarbonate over acrylic for ice hockey spectator shielding, one topic that often comes up is the higher cost of polycarbonate compared to acrylic and whether the benefits justify the cost.
There multiple sources of evidence that flexible boards lead to a reduction in injures. The following link to the British Medical Journal shows an article where injury rates at the IHF World Championships were studied over a seven year period. It shows that injury rates (including those to the shoulder and head regions) were significantly lower when flexible boards were used compared to glass boards. Increasing this flexibility by using polycarbonate rather than acrylic is likely to lead to further reductions in injury rates.
When looking at the cost of polycarbonate versus acrylic sheet, there is no doubt that a sheet of 0.545″ or 0.472″ sheet of 48″ x 96″ polycarbonate is more expensive than an equivalent sized sheet of acrylic. This increase in cost may not be significant for arenas at the higher levels of hockey but could be an important factor for community level rinks.
However, it is important to remember that with polycarbonate sheet, it is not necessary to use the same thickness sheet as for acrylic sheet because the polycarbonate sheet will not break. In fact it is better to use a thinner sheet as it further increases the flexibility. It is perfectly possible to replace 0.545″ or 0.472″ acrylic sheet with 0.39″ polycarbonate sheet; this reduction leads to 30% weight saving in the case of the 0.545″ sheet and 20% weight saving in the case of the 0.472″ sheet. This reduction in the weight means that the price of the polycarbonate sheet drops and becomes very competitive with the thicker acrylic sheet. Even though switching from polycarbonate to acrylic is unlikely to give an material cost saving, it is also unlikely to contribute to a cost increase.
Although the capital cost is likely to be similar, the labor cost of installing the thinner sheet is likely to be lower as it can be installed quicker and with less personnel. Also shielding breakage will be eliminated by using polycarbonate, reducing replacement cost. There is also the very real cost saving associated with reducing player injuries, which we will not attempt to calculate here.
In conclusion, because thinner sheet can be used when switching from polycarbonate to acrylic, it is likely that installing polycarbonate sheet will not be any more expensive than installing acrylic sheet. Cost is therefore eliminated as a reason for not switching to polycarbonate to improve hockey player safety.
As we discussed in the first two posts of this series, polycarbonate has a number of advantages over acrylic for hockey spectator shielding:
- Polycarbonate is more flexible than acrylic. This increased flexibilty can contribute to reducing the risk of concussion and improving player safety. Tests have shown it can be over 60% more flexible.
- Polycarbonate sheet will not break unlike acrylic. This strength leads to less risks to spectators. Also the sheets can be made thinner, leading to less potential for injuries to arena personnel during installation.
Given these significant benefits, why then did arenas choose acrylic when moving away from tempered glass? The answer lies in the optical properties of the sheet. Even though acrylic is not as flexible or as strong as polycarbonate, it was a significant improvement over tempered glass.
The acrylic sheet used in hockey arena shielding is made using a cast process. This process is a batch process where liquid monomer is poured between two sheets of glass separated by an edge gasket. The whole structure is then heated to polymerize the liquid monomer into the solid acrylic sheet. Once this process is complete, the two pieces of glass are then removed. Although the process is slow and has some limitations (such as the difficulty in controlling thickness), it produces a very clear sheet with very little optical distortion.
Polycarbonate sheet cannot be made in the same way due to the chemistry involved. To make polycarbonate sheet, it is necessary to polymerize polycarbonate in a reactor and then form plastic pellets of polycarbonate resin. These pellets are then melted in an extruder and the molten polymer is then passed between some chrome rolls to make a smooth sheet. The process of extruding sheet is a continuous process that produces a very consistent product. Unfortunately, until recently, the optical properties of polycarbonate sheet were no-where near as good as acrylic sheet and had significant distortion. This distortion would make viewing hockey through the sheet a poor experience. This distortion issue became more severe the thicker the sheet. Most of the polycarbonate sheet on the market still has a distortion issue, particularly on the thicknesses required for hockey spectator shielding.
Believing that polycarbonate offers many advantages over acrylic for the hockey arena market, HighLine has devoted considerable resources to improving the optical distortion of 0.39″ to 0.585″ polycarbonate sheet. We are now able to offer a sheet that has optical properties as good as cast acrylic sheet. We test the optical properties by projecting a line pattern through a sheet that has been inclined. The test equipment set up is shown in the diagram below. This test method is based on a German test standard used to measure distortion on front windshields of automobiles.
With a sheet with optical distortion, this pattern becomes distorted when it passes through the sheet. The projected pattern from a competitor’s polycarbonate sheet is shown below.
Viewing a game through a sheet with this level of distortion would be difficult at best.
In comparison below is the projected pattern from a HighLine Polycarbonate sheet that we used for testing for the hockey arena shielding:
It can be seen that virtually no distortion is detectable.
Sheet from HighLine Polycarbonate can now be used to improve the safety of players, spectators and arena staff without compromising the viewing experience at the hockey game.
In the first part of this blog series we showed that 0.47″ Polycarbonate is 20-25% more flexible than the same thickness Acrylic under simulated hockey player impact conditions. This increased flexibility could potentially lead to a reduced number of player concussions and reduce concussion severity.
In this article we will discuss how the thickness of the shielding affects the flexibility. Acrylic is traditionally used at a thickness of 0.47″. As Acrylic can break, it is not advisable to go thinner than this for spectator shielding. Indeed, some hockey arenas even increase the thickness to 0.545″ to prevent breakage, unfortunately increasing the rigidity in the process.
Polycarbonate does not suffer from the same breakage problems as Acrylic, therefore it is possible to reduce the thickness without having the risk of material breaking. To see how reducing the thickness of the Polycarbonate affected the flexibility, we tested 0.47″, 0.39″ and 0.31″ Polycarbonate under simulated hockey impact conditions (a 180lb weight hitting the shielding at a speed of 14mph). We found that 0.39″ Polycarbonate was 40% more flexible than 0.47″ Polycarbonate. We also found that 0.31″ Polycarbonate was 45% more flexible than 0.47″ Polycarbonate. We concluded that the largest benefit in flexibility was in reducing the Polycarbonate from 0.47″ to 0.39″ and that further reductions to 0.31″ only had marginal benefits.
Overall changing from 0.47″ Acrylic to 0.39″ Polycarbonate increased the flexibility by over 60%; a significant change from a player safety perspective. Even with this increased flexibility and reduced thickness, the Polycarbonate would virtually eliminate the current breakage issue.
Another factor to consider for arena safety is that changing from 0.545″ x 50″ x 80″ Acrylic to 0.39″ x 50″ x 80″ Polycarbonate would reduce the weight of each sheet from over 90 lbs per sheet to 65 lbs per sheet. This decrease is very significant when considering the safety of arena personnel lifting the panels into place and when considering the consequences of a panel falling into the crowd following an impact by the players.
One consequence of the increased flexibility of the panel is there is slightly increased movement of the panel in the frame. A 0.47″ Acrylic sheet moved 0.34″ in the frame whereas the 0.39″ Polycarbonate moved 0.71″ in the frame. This increased movement needs to be considered when designing the frame and HighLine can provide assistance if required.
Acrylic has replaced tempered glass at many hockey rinks for player and spectator safety reasons. Acrylic is much more flexible than the rigid tempered glass and therefore reduces the potential for injuries such as player concussion. Acrylic also has good optical properties which allow spectators to get a good view of the action.
For many years other polymers were not considered as they were unable to match the optical properties of the Acrylic. However, with recent advances in the production process, the polycarbonate produced by HighLine has changed the equation.
For the same thickness of material, polycarbonate is between 20-25% more flexible than acrylic. This increase in flexibility significantly reduces the risk of concussions by players – a key focus of player safety advocates. However, due to the unbreakable nature of the polycarbonate, it is possible to reduce the thickness from 0.545″ in the case of acrylic to 0.39″ or even 0.32″ in the case of polycarbonate. This reduction in thickness further increases the flexibility and reduces the possibility of concussions. These flexibility results have been confirmed by simulating the impact on the shields by a hockey player using a weighted bag, moving at speeds representative of NHL player speeds. The test set up is shown in the attached photograph. Full test data can be provided by contacting HighLine.
Also, as polycarbonate is unbreakable, shattering acrylic shields around the rink can be a thing of the past; increasing both player and spectator safety. It also eliminates downtime to replace shattered shields during games or practices.
With the reduction in thickness, comes the reduction in weight. The much lighter weight reduces the change over time for rink operations management and makes the shields easier and safer to install.
The key area of improvement that allows polycarbonate to displace acrylic as the material of choice for ice hockey spectator shields is the improvement in optical quality of material produced by HighLine Polycarbonate LLC for hockey rinks. The optical appearance of polycarbonate is virtually identical to that of acrylic in an equivalent thickness. However, because polycarbonate can offer greater protection at thinner thicknesses than acrylic, the optical properties of the thinner material can actually exceed those of the acrylic.
Due to the improved player and spectator safety of polycarbonate, it is starting to displace acrylic at European rinks. With the current interest in reducing player concussions to amateurs and NHL professionals alike, HighLine is at the forefront of bringing polycarbonate rink guards to the North American market.
HighLine Polycarbonate representatives will be walking the NARCE 2016 show in Columbus. If you would like to meet with us at the show for a coffee and chat, please give us a call or send us an email.