appearance quality
The surface shall be flat, free from defects such as cracking, missing adhesive, or sponginess, and the eccentricity of the center hole shall not exceed one-third of the tubular cross-sectional thickness.
Allow no more than 4 defects such as dents, bubbles, and impurities with a depth ≤2mm and area ≤16mm². On the designed working surface, only defects with a depth ≤1mm and area ≤10mm² are permitted, limited to no more than 3.
dimensional tolerance
Thickness limit deviation:+1.3mm (thickness ≤ 6mm),+1.0mm (thickness>6-10mm),+2.0mm (thickness>10-20mm).
Width limit deviation: ± 3%.
Physical and mechanical properties
Hardness: Shore A 60 ± 5 degrees.
Tensile strength: ≥ 12MPa (natural rubber) or ≥ 10MPa (synthetic rubber).
Tensile elongation at break: ≥ 380%.
Compression permanent deformation: ≤ 35% after 24 hours at 70 ℃.
Tear strength: ≥ 30kN/m.
Brittle temperature: ≤ -45 ℃.
Aging resistance performance
Hot air aging: After 70 ℃ × 168h, the tensile strength retention rate is ≥ 80%, and the elongation at break is ≥ 300%.
Ozone aging: After 50pphm, 20%, and 48h, there is no cracking (level 0) or slight cracking (level 2).
Other performance
Adhesive performance: When rubber is bonded to metal, the cross-section should be within the elastic body.
Mold resistance: The mold resistance should be ≥ level 2 (if required).