ISO 249:2016 pdf download

ISO 249:2016 pdf download.Rubber, raw natural — Determination of dirt content
1 Scope
This International Standard specifies a method for the determination of the dirt content of raw natural rubber.
It is not applicable to dirt present as surface contamination.
2 Normative references
The following documents, in whole or in part, are normatively referenced in this document and are indispensable for its application. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.
ISO 565, Test sieves — Metal wire cloth, perforated metal plate and electroformed sheet — Nominal sizes of openings
ISO 1795, Rubber, raw natural and raw synthetic — Sampling and further preparative procedures
3 Reagents
WARNING — All recognized health and safety precautions shall be exercised during the operations of this analysis, with particular emphasis on safe handling of the flammable solvents required. All solvents shall be free from water and dirt.
During the analysis, wherever possible, use only reagents of recognized analytical grade.
3.1 Mixed xylenes, boiling range 139 °C to 141 °C.
3.2 High-aromatic hydrocarbon solvent known as white spirit, boiling range 155 °C to 198 °C, or other hydrocarbon solvents of similar boiling range.
3.3 Light petroleum, boiling range 60 °C to 80 °C or other hydrocarbon solvents of similar boiling range.
3.4 Toluene.
3.5 Rubber peptizing agents.
3.5.1 Xylyl mercaptan solution, a mass fraction of 36 % in mineral oil.
3.5.2 2-mercaptobenzothiazole.
3.5.3 Di-(2-benzamidophenyl) disulfide.
3.5.4 Tolyl mercaptan solution, a mass fraction of 20 % to a mass fraction of 40 % in mineral oil.
3.5.5 Other fully soluble rubber peptizing agent.
4 Apparatus
Ordinary laboratory equipment, and the following.
4.1 Conical flask, of capacity 250 cm 3 or 500 cm 3 fitted with a suitable stopper; or beaker, of capacity 250 cm 3 or 500 cm 3 , and a clock glass of appropriate diameter as cover.
4.2 Short air condenser, (optional).
4.3 Thermometer, reading to at least 200 °C.
4.4 Heater, for heating the conical flask or beaker (4.1) and its contents (see 5.3.4).
Hotplates which provide uniform heating surfaces, or infrared lamps, are recommended. Infrared lamps (250 W) can be placed in rows, with the base of the conical flask about 20 cm from the top of the lamp. Individual control of each lamp is recommended to prevent localized overheating. Alternatively, a sand bath may be used.
4.5 Sieve, of nominal size of openings 44 µm to 45 µm (325 mesh) of corrosion-resistant wire gauze,preferably stainless steel, complying with ISO 565.
4.5.1 The wire gauze shall be mounted across the end of a metal tube about 25 mm in diameter and greater than 20 mm long.
4.5.2 The sieve shall be constructed in such a way that the gauze is free from distortion and is protected from accidental damage. A suitable construction is shown in Figure 1.
4.5.3 Sieves and holders may also be constructed by removing the bottom of a metal crucible having the appropriate dimensions, and soldering the screen to the crucible. This results in an ample container for the rubber solution during filtering.
4.5.4 A coarse screen may also be soldered under the 44 µm to 45 µm (325 mesh) gauze to protect it from accidental damage. This “guard” screen shall not hinder the filtration in any way but only provide a support for the gauze.
4.5.5 Commercially available filtration apparatus having 44 µm to 45 µm (325 mesh) gauze is acceptable, provided it can be used as specified in this International Standard.