Testing Item

Index

Test Method

Superior Grade

First Grade

Qualified

Volatile matter(%)≤

0.60

0.75

0.90

GB/T6737

Ash content

≤0.50

GB/T4498A

Organic acid(%)

4.50~6.75

GB/T8657A

Soap content(%)

≤0.5

Combinated Styrene content(%)

22.5~24.5

GB/T8658

Raw rubber mooney viscosity

ML(1+4)100°C

45~55

44~56

GB/T1232.1

Compounded rubber mooney viscosity

ML(1+4)100°C≤

93

300% Stretching Stress

(145°C)/MPa

25min

16.2±2.0

16.2±2.5

GB/T8656A

35min

20.6±2.0

20.6±2.5

50min

21.5±2.0

21.5±2.5

Tensile strength

(145°C, 35min)/MPa

≥25.5

≥25.5

≥24.5

Elongationg at break

(145°C, 35min)/%

≥340

≥330