Active Standard ASTM D4924 | Developed by Subcommittee: D11.20
Book of Standards Volume: 09.01
Historical (view previous versions of standard)
Significance and Use
Petroleum waxes in rubber compounds are commonly used to provide protection from degradation by ozone under static conditions, that is, when there is little or no flexing of the rubber products. The mode of action for this protection is (1) migration of the wax through the rubber to the surface of the product and (2) the formation of an ozone impervious film on the surface.
This standard classifies the petroleum waxes on the basis of molecular weight. In general, waxes of lower molecular weight (“paraffinic” or “crystalline”) migrate through the rubber more rapidly and form more brittle film than the higher molecular weight waxes (“microcrystalline”). Wax mixtures and blends are commonly used.
No direct inference of suitability for use in a particular rubber compound is made or implied by the classifications herein.
1.1 This classification is intended to establish a classification system and test methods for petroleum waxes used in rubber compounding primarily as a static protective agent or material for unsaturated rubbers such as styrene-butadiene rubber, polyisoprene rubber, natural rubber, chloroprene rubber, acrylonitrile-butadiene rubber, and polybutadiene rubber. These unsaturated rubbers are subject to ozone cracking. Under certain exposure conditions, waxes retard this cracking.
1.2 This classification is applicable to petroleum waxes used as process aids in rubber compounding. It is not applicable to nonpetroleum waxes such as carnuba wax, candelille wax, or ceresin wax, nor to synthetic hydrocarbon waxes such as polyethylene wax. These non-petroleum waxes display a different behavior on gas chromatographic analysis than do petroleum waxes.
1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
2. Referenced Documents (purchase separately) The documents listed below are referenced within the subject standard but are not provided as part of the standard.
D87 Test Method for Melting Point of Petroleum Wax (Cooling Curve)
D445 Test Method for Kinematic Viscosity of Transparent and Opaque Liquids (and Calculation of Dynamic Viscosity)
D721 Test Method for Oil Content of Petroleum Waxes
D938 Test Method for Congealing Point of Petroleum Waxes, Including Petrolatum
D1321 Test Method for Needle Penetration of Petroleum Waxes
D1500 Test Method for ASTM Color of Petroleum Products (ASTM Color Scale)
D1747 Test Method for Refractive Index of Viscous Materials
D1833 Test Method for Odor of Petroleum Wax
D2887 Test Method for Boiling Range Distribution of Petroleum Fractions by Gas Chromatography
D3944 Test Method for Solidification Point of Petroleum Wax
D4419 Test Method for Measurement of Transition Temperatures of Petroleum Waxes by Differential Scanning Calorimetry (DSC)
ICS Number Code 75.140 (Waxes, bituminous materials and other petroleum products)