The Effect of Temperature on the Material Stiffness of Field Hockey Balls for Material Selection

Abstract

It is well known that temperature affects the material properties of polyvinyl chloride (PVC). In particular, field hockey players report balls made of PVC breaking in half when hit in cold weather. Hockey ball manufacturers are interested in the effect of temperature on balls breaking to inform ball design and material selection. To test whether hockey balls are easier to break in cold temperatures, this study measured the material stiffness [N/mm] of hockey balls at temperatures between -4°C and 23°C using an Instron Universal Testing Machine (UTM). For white PVC hockey balls, this study finds for every 1 degree increase in temperature, there is a 3.44 ± 0.64 N/mm decrease in material stiffness. For yellow and orange PVC hockey balls, there is a 4.91 ± 1.00 N/mm decrease in material stiffness for every 1 degree increase in temperature. A higher material stiffness results in a lower force threshold for brittle fracture. The results indicate that hockey balls are more likely to break at lower temperatures regardless of color. White PVC hockey balls are less likely to break at lower temperatures than orange or yellow PVC hockey balls. This study additionally compares this effect to a white prototype ball made of a different material (polyurethane) and finds there is an 11.32 ± 4.10 N/mm decrease in material stiffness for every 1 degree increase in temperature for the prototype ball.