The "ISO 9924 Rubber and rubber products - Determination of the composition of vulcanized and uncured compounds by thermogravimetry" standard, published by the International Organization for Standardization (ISO), consists of the following sub-sections published under the same title:
This method is suitable for the analysis of rubber compounds and vulcanized rubbers containing the following rubbers, either alone or in mixtures:
The application area of the method can also be extended to the analysis of compounds containing rubbers different from those given here, provided that the applicability of the method has been tested beforehand using known compounds or vulcanizers with similar composition. Other compounds are addressed in the ISO 9924-2 standard.
In principle, a weighed test sample is heated under a stream of nitrogen from 70 degrees to 300 degrees according to a predetermined schedule and held at 300 degrees for 10 minutes. The mass loss indicates, approximately, the total content of non-rubber organic matter that is volatile at 300 degrees. In general, this value is not equivalent to the value of the solvent extract.
The furnace temperature is then raised to 550 degrees under a stream of nitrogen and held at 550 degrees for 15 minutes. Undistilled organic matter and polymers are removed by distillation at 300 degrees, and the mass loss between 70 and 550 degrees represents the total organic matter content.
The furnace temperature is reduced to 300 degrees under a stream of nitrogen, then the gas is changed from nitrogen to air or oxygen, or a mixture of air and oxygen. The furnace temperature is then raised to 650 degrees and held at this temperature for 15 minutes or until no mass loss is observed. Carbon black is burned, and the mass loss in the oxidizing atmosphere at 650 degrees represents the carbon black content. At 850 degrees, if graphite is present, a balanced gas flow is ensured throughout the transition to avoid buoyancy effects.
The mass of residue at 650 degrees represents ash (at 850 degrees if graphite is present).
This method is suitable for the analysis of rubber compounds and vulcanizates containing hydrocarbon polymers and copolymers with polar groups that form carbonaceous residues during pyrolysis, as specified in the ISO 9924-1 standard:
In principle, a weighed test sample is heated under a stream of nitrogen from 40 degrees to 600 degrees Celsius according to a predetermined schedule until all organic matter is pyrolyzed. If nitrile-butadiene copolymers are present, a small portion of the polymer will pyrolyze, forming a carbonaceous residue, and this residue needs to be identified to obtain the correct total organic content.
For this purpose, the furnace temperature is lowered to 400 degrees under a stream of nitrogen and held at 400 degrees for 5 minutes. Then the gas stream is changed from nitrogen to air or oxygen, and the furnace temperature is slowly raised to 800 degrees. During this heating in an oxidizing atmosphere, two different mass losses occur due to combustion. The first is due to the combustion of the carbonaceous residue, the amount of which is determined and added to the loss previously determined at 600 degrees in nitrogen to obtain the correct value of the total organic content. The second is due to the normal combustion of carbon black.
Total rubber content is calculated by subtracting the value of the solvent extract, determined according to ISO 1407 standard, from the total organic content, provided that all components other than rubber are extractable.
At 800 degrees, the mass of the residue represents ash.
This method is applicable to raw or compound rubbers, vulcanized and unvulcanized rubbers, after pre-extraction.
This method applies to hydrocarbon-backed rubbers used alone or in blends. For blends, the polymer content corresponds to the total rubber, and it is generally not possible to identify individual polymers.
This method is applicable to halogenated hydrocarbon-backed rubbers or nitrogen-containing rubbers and their blends. However, these rubbers often form carbonaceous residues that hinder analysis. Applying a proper procedure minimizes these obstacles.
This method is also applicable to rubbers with a polysiloxane backbone and rubbers not listed above.
In principle, a weighed test sample is heated in a known atmosphere according to a predetermined schedule. First, pyrolysis occurs in an inert atmosphere (nitrogen), followed by combustion in an oxidizing atmosphere. Reactions that typically cause mass changes are decompositions, oxidations, or reactions that vaporize a component. The mass loss with respect to temperature provides a quantitatively usable thermogram that indicates the characteristic properties of the material.
In short, ISO 9924 is an international standard that defines a thermogravimetric analysis (TGA) method for determining the composition of vulcanized rubber (vulcanizates) and uncured rubber compounds. It measures the basic components by monitoring controlled heating and mass loss:
Rubber compounds are complex mixtures, and in most cases, especially after vulcanization, their exact formula cannot be reliably known visually or through simple chemical tests.
This standard exists for several critical practical reasons:
Consequently, the rubber industry needs a rapid, repeatable, internationally accepted method for measuring the most important components in cured and uncured rubber, particularly carbon black and polymer content, for quality assurance, failure analysis, and fair trade practices. The ISO 9924 standard is essential in this respect.
For many years, our organization, with its competent and experienced staff, has been understanding the needs of its clients, providing the advanced testing services they require, and assisting them in the establishment, implementation, and improvement of management systems. Within this framework, we also provide testing services compliant with the ISO 9924 standard.
To get an appointment, to get more detailed information or to request an evaluation, you can ask us to fill in our form and reach you.
