Sport and transport protective helmets are becoming more sophisticated, as cyclists, motorbike riders and sportsmen become increasingly safety-conscious. At this time, amidst innovations and advancements, helmets still rely heavily on plastic foams to absorb energy.
Masuri, the most widely used helmet manufacturer in professional cricket, boasts innovative designs that are subject to stringent testing. In the new Masuri Vision Series, there are three layers of protection. First, there is the polycarbonate inner shell. The shell is covered by an expanded, rigid and tough polystyrene crush zone. Finally, a very thin polypropylene outer shell completes the helmet.
Until recently, neither the British nor Australian/NZ Standards included projectile testing, nor did they include any provision for helmet/faceguard failure due to contact with the face. Impact energy levels and impact areas for the associated testing protocols did not seem to match impact forces and locations that were likely to occur during cricket batting situations.
In contrast, the North American National Operating Committee on Standards for Athletic Equipment (NOCSAE) testing of baseball catchers’ helmets appeared to utilise similar types of ball, ball speed and replicated the head area requiring protection in cricket. The NOCSAE specification is updated annually and involves both drop and projectile testing (involving a baseball being fired at the helmet/face guard). Accordingly, the specification for head protectors in cricket was updated and published in December 2013.
Unfortunately it took the tragic death of Australian cricketer Phillip Hughes to focus the world’s attention on sporting headwear safety standards. Masuri found themselves at the centre of a media storm, as they were the brand of helmet Phillip Hughes was wearing when he was hit, albeit an older model. Hughes’ brain injury was caused by being hit at the base of the skull where it is very difficult to adequately protect without restricting a batsman’s head movement.
Masuri has since announced their concept-in-development of a protection system for the back of the head that it believes will protect that vulnerable area but still allow movement. The Masuri branded design, StemGuard, combines an impact-modified thermoplastic polyurethane (TPU) honeycomb with military grade crush foam to maximise impact absorption, giving players much more confidence when batting. The StemGuard attaches to the existing Masuri Vision Series helmets with moulded clips.
Polystyene replacement?
Maybe soon we can say goodbye to polystyrene foam altogether? In what looks like an ordinary bicycle helmet, Swedish designers have replaced Styrofoam with a new shock-absorbing renewable and biodegradable wood-based material. The helmet is intended to draw attention to the possibilities of using wood cellulose as a sustainable alternative to Styrofoam and other foams from synthetic polymers.
Researcher Lars Wågberg, a professor in Fibre Technology at Stockholm’s KTH Royal Institute of Technology, says the wood-based foam material offers comparable properties to Styrofoam. “But even better, it is from a totally renewable resource — something that we can produce from the forest,” Wågberg says.
Trademarked under the name, Cellufoam, the helmet is produced by Cellutech, a Stockholm startup that specialises in cutting edge materials made from wood.
Production begins with wood cellulose nanofibres, or fibrils, that are modified and mixed with a foaming agent, water and air. Through the process of Pickering stabilisation, these particles hold the air-bubbles in a way that is much better than by using simple surfactants, he says.
While the Cellufoam is being showcased as a bicycle helmet material, Wågberg says that by using different surface treatments and combining it with other components, it could also be suitable for flame retardant material, water filtration and antibacterial material.
Urethane foams come out top
The latest hockey helmet from Bauer RE-AKT 75 is the best performing helmet on the consumer market, according to the Virginia Tech Helmet Ratings system, called the Hockey Summation of Tests for the Analysis of Risk (STAR) evaluation system. The STAR evaluation system was developed over three years and initially released in April 2015. Virginia Tech researchers rate the Bauer helmet the highest of 38 hockey helmet models that have been tested to date, earning three stars. The RE-AKT 75 helmet uses Poron, a protective foam product manufactured by Rogers Corporation (USA). Made from polyurethane (PU) foam, Poron has the ability to absorb and dissipate a huge amount of energy during impacts.
The helmet also features the so-called Seven Technology Liner System – an impact attenuation system designed to more effectively manage energy transfer from direct high energy impacts. Upon impact, the Seven Technology Liner System compresses to laterally displace energy. Within seconds it completely resets and is ready for the next impact.
“The Bauer RE-AKT 75 did the best job of managing impact energy and lowering head acceleration of all the hockey helmets we’ve tested to date,” said Steve Rowson, director of the Virginia Tech Helmet Laboratory and an assistant professor in the Department of Biomedical Engineering and Mechanics in Virginia Tech’s College of Engineering. “While there is still room for improvement, this places the new Bauer hockey helmet at the very top of our hockey helmet ratings.”
A paper published in the Annals of Biomedical Engineering, “Hockey STAR: A Methodology for Assessing the Biomechanical Performance of Hockey Helmets,” details the approach that Rowson and his colleagues take to test the protective capabilities of the helmets.
Searching for plastic materials?
Prospector lists materials from global suppliers and offers the ability to view technical data and more.
Click Here
The views, opinions and technical analyses presented here are those of the author or advertiser, and are not necessarily those of ULProspector.com or UL Solutions. The appearance of this content in the UL Prospector Knowledge Center does not constitute an endorsement by UL Solutions or its affiliates.
All content is subject to copyright and may not be reproduced without prior authorization from UL Solutions or the content author.
The content has been made available for informational and educational purposes only. While the editors of this site may verify the accuracy of its content from time to time, we assume no responsibility for errors made by the author, editorial staff or any other contributor.
UL Solutions does not make any representations or warranties with respect to the accuracy, applicability, fitness or completeness of the content. UL Solutions does not warrant the performance, effectiveness or applicability of sites listed or linked to in any content.
Hi Andy,
Can you tell me the most absorbent foam known to man (to protect from falls/impacts)?
The answer to this question would depend on the nature of the application – the environment and the nature of the impact forces. There is no single, specific answer and stringent testing of the material chosen under service conditions would be recommended prior to use.
To understand what types of materials are best for shock absorption, one must understand how shock energy is absorbed. Shock is the effect on an object caused by the energy delivered to it by a force, usually an impact force, over a short time period. The effect of shock occurs when the energy of the impact is transferred from one individual or object to another. This wave of energy can cause injury or damage to the affected individuals or objects.
Shock Energy is absorbed via a process called damping — the dispersion or disruption of the energy caused by shock’s impact forces — absorbs the energy from shock by decreasing the amplitude (strength) of the shock energy’s wave or by changing the wave’s frequency. Absorption reduces or eliminates the adverse effects, injury, or damage to an object or individual caused by shock.
To be effective, a shock absorption material must eliminate or reduce oscillations across a wide range of frequencies. To be effective in an industrial environment, a shock absorption material must perform well in a wide range of temperatures, even changing temperatures, regardless of the source of the shock, over an extended period of time.
Most shock absorbing materials are plastic foams. This is a good review of options used i sporting applications:
https://e-space.mmu.ac.uk/597115/1/ATNT%202011%20A%20critical%20review%20of%20impact%20resistant%20materials.pdf
Sorbothane is a proprietary, thermoset, polyether-based polyurethane material with visco-elastic properties — that is, it acts as a liquid to absorb shock and as an elastic solid when at rest. It performs by converting the impact of the shock energy to a small amount of heat.
As an industrial material, Sorbothane is resistant to fire and chemical solvents found in an industrial environment. It also performs through a wide range of temperatures and millions of cycles without degrading in performance.
Sorbothane was specifically designed for shock absorption and is manufactured to outperform every other material on the market. What makes Sorbothane the best material for shock absorption?
It absorbs more than 90% of shock energy and more than 50% of vibration energy;
It performs in temperatures ranging from –20° to 160° Fahrenheit (–29° to 72° Celsius)];
It performs at frequencies ranging from 10 to 30,000Hz;
Its damping ratio is 0.344 at 2.34Hz;
It does not support bacterial or fungal growth and is relatively unaffected by industrial solvents such as diesel fuel, kerosene, and hydraulic fluid;
It has an extremely long shelf life; and
It has a very high damping coefficient.