ANSI SCTE 251-2018 pdf free download.Test Procedure for Determining the Thermal Oxidative Stability of Foamed Polyethylene
1.1. Executive Summary
When attempting to place standardized performance values on a product, it is necessary to also provide standardized test methods to ensure repeatability of measurements. This document is intended to provide test method details and implementation of ASTM D4565 for testing of foamed cable dielectric materials.
1.2. Scope
This method covers the determination of an Oxidative Induction Time (OIT) value for coaxial cable,
foamed polyethylene, and insulation materials removed from completed cable products. This test
procedure is based on the ASTM D4565. The OIT value is determined by a thermo-analytical
measurement of the onset time for the exothermic oxidation of insulation in pure oxygen, at a specified temperature.
1.3. Benefits
This document is designed to benefit manufacturers and end users of product tested to this procedure by supplying a standardized method for determining an Oxidative Induction Time (OIT) value for coaxial cable, foamed polyethylene, and insulation materials removed from completed cable products.
1.4. Intended Audience
This document is intended for anyone desiring to make industry standard OIT measurements of coaxial cable, or for anyone acquiring product purported to have been tested using this method.
1.5. Areas for Further Investigation or to be Added in Future Versions
None.
2. Normative References
The following documents contain provisions, which, through reference in this text, constitute provisions of this document. At the time of Subcommittee approval, the editions indicated were valid. All documents are subject to revision; and while parties to any agreement based on this document are encouraged to investigate the possibility of applying the most recent editions of the documents listed below, they are reminded that newer editions of those documents might not be compatible with the referenced version.
2.1. SCTE References
• No normative references are applicable.
2.2. Standards from Other Organizations
• No normative references are applicable.
2.3. Published Materials
• No normative references are applicable.
3. Informative References
The following documents might provide valuable information to the reader but are not required when complying with this document.
3.1. SCTE References
• ANSI/SCTE 74 2011 Specification for Braided 75 Ohm Flexible RF Coaxial Drop Cables
3.2. Standards from Other Organizations
• ASTM D4565
3.3. Published Materials
• No informative references are applicable.
4. Compliance Notation
shall This word or the adjective “required” means that the item is an absolute requirement of this document. shall not This phrase means that the item is an absolute prohibition of this document. forbidden This word means the value specified shall never be used. should This word or the adjective “recommended” means that there may exist valid reasons in particular circumstances to ignore this item, but the full implications should be understood and the case carefully weighted before choosing a different course. should not This phrase means that there may exist valid reasons in particular circumstances when the listed behavior is acceptable or even useful, but the full implications should be understood and the case carefully weighed before implementing any behavior described with this label. may This word or the adjective “optional” means that this item is truly optional. One vendor may choose to include the item because a particular marketplace requires it or because it enhances the product, for example; another vendor may omit the same item. deprecated Use is permissible for legacy purposes only. Deprecated features may be removed from future versions of this document. Implementations should avoid use of deprecated features.
Discussion—Other components in the foam material may cause secondary effects. The OIT value for insulation may be significantly altered by contamination or additives such as pigments, fillers, and processing aids as well as catalyst residues from the cable, wire, insulation, or resin manufacture. The OIT value may increase or decrease depending on whether these additives and residues act as oxidation inhibitors or promoters at the test temperature. At typical test temperatures (for example, ANSI/SCTE 74 requires 180 °C), compounds present in the polyolefin material may decompose and change the polyolefin oxidation mechanism and thereby the OIT value. If the oxidation mechanism is so altered, then the OIT value may not correlate to aging at normal use temperatures. Before using the OIT value to predict field performance and lifetimes, additional studies may be required to establish a correlation between the OIT value measured at high temperature and the performance of the polyolefin under typical field conditions.
