| A distinction is made between isotactic, syndiotactic, and atactic polypropylene. Isotactic PP is primarily used for technical applications, since an increase in isotacticity is associated with an increase in the level of crystallinity, melting point, tensile strength, rigidity, and hardness. The rigidity of polypropylene in conjunction with good mechanical strength values and a high surface hardness enables the manufacturing of machined parts and welded construction with relatively thin wall thicknesses. An increase in tensile strength is made possible by controlled stretching (can be seen in the diagram though the drop in tensile stress after the yield point with a subsequent elongation phase at low force). Following the stretching process and subsequent constriction of the test specimen, a higher tensile strength with lower ultimate elongation is achieved. This effect can be used for film hinge applications. Semi-finished products made from PP are also used in chemical apparatus construction at temperatures of between 0 °C and +100 °C. The maximum service temperature is between +100 to +110 °C.Information provided by Angst + Pfister |
