Shore A0 hardness measurement is a method for determining the hardness of elastomers and thermoplastic elastomers of low hardness and cellular rubber in the scale range < 20 Shore A (range of low hardness and cellular rubber). The measuring time is 1sec., 3sec, or 15sec. depending on the specification and or material. The measurement is performed at room temperature, ideally on a flat, smooth material surface. Shore A0 hardness is an important parameter for comparative measurements of elastomers and TPEs of low hardness and cellular rubber and helps in material selection for various applications.
When determining the indentation hardness by the durometer method (Shore hardness), a spring-loaded indenter with standardized geometry is pressed into the material for a defined measuring time and the indentation depth is measured. The scale for Shore hardness in general ranges from 0 (very soft) to 100 (very hard). The hardness is determined by the reaction of the elastomer to the generated indentation. The reaction is complex and depends on the following factors:
- Young's modulus of the elastomer, TPEs
- Viscoelastic properties of the elastomer or TPEs
- Thickness of the specimen
- Geometry of the indenter
- Spring force
- Speed of the pressure increase
- Time span after which the hardness is distinguished (measuring time)
Due to these influencing variables, a direct comparison of durometer hardnesses (Shore A, Shore D, etc.) with IRHD hardnesses (micro IRHD, IRHD N, etc.) is not meaningful.