introduction
ISO (International Organization for Standardization) is a global alliance of national standards bodies (ISO member bodies). The development of international standards is usually carried out through ISO technical committees. Each member institution interested in a subject on which a technical committee has been established has the right to be represented on that committee. International governmental and non-governmental organizations liaising with ISO are also involved in this work. ISO works closely with the International Electrotechnical Commission (IEC) on all matters of electrical standardization.

The procedures used to develop this document and those used for further maintenance are described in Part 1 of the ISO/IEC Directive. In particular, attention should be paid to the different approval criteria required for different types of ISO documents. This document has been drafted in accordance with the editing rules of ISO/IEC Directive Part 2 (see iso.org/directives).

Please note that certain elements of this document may be subject to patent rights. ISO is not responsible for identifying any or all such patents. Details of any patent rights identified during the preparation of the document will be found in the introduction and/or in the list of patent claims received by ISO (see iso.org/patents).

ISO 18473-3-2018 “Functional pigments and fillers for special purposes – Part 3: fumed silica for silicone rubber applications”

Any trade names used in this document are provided for the convenience of the user and do not constitute an endorsement.

Voluntary, related standards and conformity assessment related ISO specific and express the meaning of terminology as well as in relevant ISO technical barriers to trade (TBT) adhere to the principle of the world trade organization (WTO) information, please refer to the following URL:iso.org/iso/foreword.html.

This document was prepared by the ISO/TC 256 Technical Committee on Pigments, Dyes and Fillers.

A list of all parts in the ISO ISO 18473 series can be found on the ISO website.

ISO 18473-3-2018 “Functional pigments and fillers for special purposes – Part 3: fumed silica for silicone rubber applications”

introduce
Fumed silica (fumed silica) is a pure amorphous white inorganic powder with a high specific surface area, a nanoscale primary particle size resulting in a “stable/non-destructive” aggregate structure, and a relatively high (in silica products) surface silanol group concentration. The properties of fumed silica can be chemically modified by reacting with these silanol groups. Commercially available fumed silica can be divided into two categories: hydrophilic fumed silica and hydrophobic fumed silica. Due to the above characteristics, it is widely used as an important ingredient in many industries such as rubber, paint and plastics industries. The main application of fumed silica is in the silicone rubber industry.

Silicone rubber has excellent properties, such as low temperature flexibility, good weather resistance, electrical insulation, dielectric resistance, physiological inertia, low surface tension and surface energy, to meet the important needs of the market. However, due to the low strength of cured polydimethylsiloxanes (PDMS) (< 0.4MPa), these unique properties cannot be effectively demonstrated, because cured polydimethylsiloxane (PDMS) is the main component of silicone; Therefore, in addition to additives and curing agents, silicone rubber usually contains reinforcing fillers. As one of the functional fillers, fumed silica is widely used in room temperature vulcanized silicone rubber (RTV), high temperature vulcanized silicone rubber (HTV) or high consistency vulcanized silicone rubber (HCR) and liquid silicone rubber (LSR), which plays an important role in the strength, rheology and transparency properties of silicone polymers. The test methods for dispersed fumed silica aggregate size and silanol density are still under development, both of which have significant effects on the above properties of silicone rubber.

ISO 18473-3-2018 “Functional pigments and fillers for special purposes – Part 3: fumed silica for silicone rubber applications”

1 Range
This document specifies the requirements and corresponding test methods for fumed silica in powder form for silicone rubber applications. This document is intended for both untreated and surface treated fumed silica.

2 Normative references
The following files are referenced in text in a manner that constitutes part or all of the requirements of this document. For dated references, only the cited version applies. For undated references, a new version of the reference (including any revisions) applies.

ISO 787-2, General test methods for pigments and fillers – Part 2: Determination of volatiles at 105°C

ISO 787-9, Common test methods for pigments and fillers – Part 9: Determination of the pH value of water suspensions

ISO 787-11, General test methods for pigments and fillers – Part 11: Determination of compaction volume and apparent density after compaction

ISO 787-18, General test methods for pigments and fillers – Part 18: Determination of residues on screens – mechanical flushing procedure

ISO 18473-3-2018 “Functional pigments and fillers for special purposes – Part 3: fumed silica for silicone rubber applications”

ISO 3262-1, paint extenders – Specifications and test methods – Part 1: Introduction and general test methods

ISO 3262-20:2000, fillers for paints. Specifications and test methods. Part 20: fumed silica

ISO 9277, Determination of specific surface area of solids by gas adsorption – BET method

ISO 15528, Paints, varnishes and raw materials for paints and varnishes – Sampling

ISO 18451-1, pigments, dyes and fillers – terminology – Part 1: General terminology

3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 18451-1 and the following articles apply.

ISO 18473-3-2018 “Functional pigments and fillers for special purposes – Part 3: fumed silica for silicone rubber applications”

3.1 Fumed silica

Amorphous silica produced by high temperature flame hydrolysis of silicon halide

Note 1: It can also undergo further surface treatment.

Only the standard information section is public. To see the full content, you need to purchase the standard through the official channels.