Hardness Drift: Why Rubber Hardens over Time in Storage.

Hardness Drift: Why Rubber Hardens over Time in Storage

Problem Statement

Rubber components stored for extended periods exhibit increased Shore A hardness, compromising sealing performance and flexibility. This issue is critical in automotive and industrial applications where long-term storage is unavoidable.

Material Science Analysis

Hardness drift occurs due to post-curing reactions and oxidation. EPDM rubber, for example, undergoes chain scission and crosslinking when exposed to oxygen, increasing hardness. FKM resists oxidation better due to its fluorine content, but improper storage conditions can still cause drift. HNBR offers superior stability due to its hydrogenated structure, minimizing post-curing effects.

Technical Specs

• Shore A Hardness: Initial 70 ±5, Post-Storage 75 ±5
• Tensile Strength: 15 MPa (EPDM), 20 MPa (FKM), 25 MPa (HNBR)
• Elongation at Break: 300% (EPDM), 250% (FKM), 350% (HNBR)
• Temperature Range: -40°C to 120°C (EPDM), -20°C to 200°C (FKM), -40°C to 150°C (HNBR)

Material Comparison

Material	Shore A Hardness Drift (%)	Compression Set (%)	Chemical Resistance
EPDM	10	25	Good
FKM	5	15	Excellent
HNBR	3	10	Very Good

Standard Compliance

RubberQ ensures batch-to-batch consistency through IATF 16949-certified processes. Materials comply with ASTM D2000 for material callouts and ISO 3601 for sealing performance. Storage conditions are strictly controlled to minimize hardness drift.

For custom material compound development or IATF 16949 documentation, consult RubberQ's engineering department.