Tensile, Elongation and Hardness: Interpreting a Test Report
Why higher tensile strength is not always better, how hardness is measured correctly, and which properties predict field performance.
Test reports contain more information than most buyers use. Knowing which numbers matter and which are noise makes acceptance decisions much easier.
Tensile strength
Tensile strength is the stress at break. It is useful for detecting gross formulation errors — a badly under-cured or badly dispersed compound shows it immediately — but it is a poor predictor of service life, because almost no rubber part fails in single-pull tension. Do not pay a premium for a higher tensile number alone.
Elongation at break
More sensitive to cure state and to ageing than tensile strength is. A falling elongation value across a production run usually indicates overcuring or thermal ageing.
Modulus at a defined elongation
Often more informative than either of the above. The stress at 100% or 300% elongation reflects crosslink density and filler loading, and it is what a designer actually works with.
Hardness
Shore A hardness is measured on a specified thickness of sample after a specified conditioning time. Common sources of disagreement include testing on too-thin samples, reading the value too quickly, and testing on a curved or textured surface. Specify the sample thickness and conditioning time in your inspection procedure.
What actually predicts field life
Compression set for seals, heat build-up and flex fatigue for dynamic parts, abrasion loss for treads and covers, and resistance to the specific service media. Ask for those tests, not just tensile and hardness. ## Need the documents or today's price? Send us the grade, quantity and destination port — we return a quotation with COA and MSDS attached. Email manager@fipolymer.com or use the inquiry form on this site.
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