Understanding Fuming / Smoking from High Temperature Fabrics and Cloths
This article addresses a common concern regarding insulation jackets and fabrics that start fuming or smoking when subjected to high temperatures, often below the fabric's stated maximum operating temperature. This phenomenon is observed in both insulation jackets and fabric components close to or in contact with hot surfaces.
Why Fabrics Fume or Smoke?
Most glass, HT Glass and silica fabrics will exhibit fuming or smoking upon initial heating. This includes even the simplest uncoated loom-state fabrics, which fume due to weaving lubricants or 'sizings' applied during the manufacturing process. Fabrics that are treated or coated contain additional compounds, leading to more thermal degradation and subsequent fuming when first heated.
E Glass Fibre Weavelock:
A standard weavelocked glass cloth is suitable for continuous use at 550°C in optimum conditions. However, the weavelock, a fire-retardant acrylic dip used to lock the yarns for easy fabrication, thermally degrades at lower temperatures, producing smoke or fumes. This degradation involves the reaction of organic acrylic compounds with oxygen, resulting in the release of carbon dioxide, carbon monoxide, and other hydrocarbons – smoke/fumes.
High Temperature Aqueous Dispersions:
Fabrics treated with common mineral dispersions like silica wash, vermiculite or graphite can endure higher temperatures up to 750°C or even 1000ºC. Even at 700°C, while the functional compound remains stable, organic binders and softeners within the fabric may still thermally degrade, causing fuming. These binders and softeners, integral to the fabric's workability, will break down.
Factors Influencing Fuming
The extent and duration of fuming depend on:
- Temperature: Higher temperatures cause more significant fuming initially.
- Rate of Heating: Rapid heating leads to quicker but more intense fuming, while slow heating results in prolonged but less intense fuming.
During initial heat cycles, some fabrics may experience charring also, but this will be covered in another article.
Non-Fuming Products
Certain products, specifically our Heat-Cleaned or Heat-Treated ranges, do not smoke or fume. These fabrics undergo pre-firing or heating to eliminate weaving oils and impurities before shipment. These products are ideal where no outgassing or fuming is permissible. However, they are more challenging to handle, prone to fraying, and generally less stable than their standard counterparts. There are also differing degrees of heat treatment, depending on the required outcome and the fabric itself. Heat Treatment tends to have most prominence in aerospace, nuclear or other critical applications where there is limited opportunity or space for ventilation.
Importance of Communication and Ventilation
It is crucial to inform site owners and operators about the expected fuming or smoking during initial heat cycles to avoid any misconceptions about potential fire hazards. Ensuring good ventilation in installation areas during these primary heat cycles is essential.
We hope this article clarifies the common concerns regarding fuming and smoking fabrics. For further technical queries, please feel free to contact the experts at Textile Technologies Europe Ltd.
- Tracy Barker
