A-A-52518
3.1.1 Material variety. This CID does not include all varieties of materials which may be used by the retreading industry, and shall not prohibited the use of such materials if the quality of the end product is not compromised.
3.2 Material definitions. Materials referenced in this CID are defined as follows:
3.2.1 Rubber. Rubber used to prepare rubber compounds described in this CID and also listed in ASTM D1418 are natural rubber (NR), isoprene rubber (IR), butadiene rubber (BR), styrene butadiene robber (SBR), and rubber hydrocarbon content (RHC).
3.2.2 Carbon black. Carbon black used to prepare tread rubber compounds described in this CID shall be tread type carbon black High Abrasion Furnace (HAF) quality to better (N300 Series ASTM D1765).
3.3 Tire repair materials type I. All tire repair materials shall meet the requirements of table I and be furnished as specified in table III.
3.3.1 Gum materials (class A, B, C). Gum materials shall meet the applicable requirements of table I for class C, and table II for classes A and B, and shall be suitable for their intended purpose (see 6.1).
3.4 Tire retreading Materials, type II. The rubber compounds used for retreading tires shall conform to the applicable physical properties specified in tables I and II, and be furnished as specified in table III.
3.4.1 Physical properties variation. Tread rubber compounds shall have a variance in tensile stress of ± 1380 kiloPascal (kPa) at 300% elongation, specific gravity + 0.015 and Shore A hardness ± 3 points. The properties shall be verified ASTM D746.
3.4.2 Cushion gum facing. Bevel and wing die size tread rubber shall be faced with rubber compound not less than .432 mm thickness for truck and 3.3 mm thickness for passenger car.
3.4.3 Curing methods. Unvulcanized tread rubber shall be capable of curing (vulcanization) at a matrix surface temperature of not less than 145°C.
3.4.4 Storage stability of strip tread rubber. Uncured tread rubber shall be subjected to oven aging at 70 ± 1°C for 70 hours. During oven aging, the material shall be enclosed in cellophane and suspended in the oven. After cooling to room temperature, the change in properties shall not exceed the limits in table IV when the strip stock is compression molded thereafter in a platen press.
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