Cologne, Germany — Lanxess hads developed a grade of hot-cast polyurethane based on p-phenylene diisocyanate (pPDI). Low-hysteresis tyres made from the material are finding a home in amusement parks.
‘We have tailor-made Adiprene LF pPDI pre-polymers that meet the requirements of the latest roller coasters,’ said Gerald King, head of application development and technical service at Lanxess’ European business unit.
‘We have also developed a material and design model with our US colleagues,’ he added. ‘This allows us to predict the characteristics of the wheels and treads. It helps to support our customers in their material selection and design.’
Rollercoaster cars have three pairs of wheels per axle which keep the car fixed to the tracks. Running wheels allow the car to move on the track. Side wheels keep the cars on the track in tight curves, and stop centrifugal forces throwing the cars off. The up-stop wheels hug the bottom of the rail to ensure the car does not lift off the track.
Synthetic rubber cannot be used in rollercoaster tyres because it is unable to withstand the high acceleration and braking forces which act on the wheels, according to Lanxess. In contrast, the Adiprene LF pPDI hot-cast elastomers have lower hysteresis.
In use, this means that the treads don’t overheat during continuous operation. As a result, they are better able to withstand loads and roll at design speed.
In addition, King said that polymer morphology can be precisely controlled. This gives highly structured phase separation between crystalline hard and amorphous soft segments. The result is improved physical and mechanical properties compared to previous grades.
Lanxess claims to be the only manufacturer to offer pre-polymer systems based on pPDI with low levels of diisocyanate monomer.