GB2292326A

GB2292326A - Improved lightweight fire-blanket fabric

Info

Publication number: GB2292326A
Application number: GB9515310A
Authority: GB
Inventors: Malcolm Bridge
Original assignee: TBA Industrial Products Ltd
Current assignee: TBA Industrial Products Ltd
Priority date: 1994-08-18
Filing date: 1995-07-26
Publication date: 1996-02-21
Also published as: GB9515310D0

Abstract

Fire blankets are constructed from glass fibre fabric having a significantly looser structure than a plain weave fabric of the same areal density, both sides of the fabric being coated with a silicone rubber polymer to render the fabric essentially impermeable.

Description

Improved lightweight fire-blanket fabric Backaround Before the use of asbestos became unacceptable it was usual for fire-blankets to be made from asbestos fabrics weighing lOOOg/m' or more. These were considerably over-specified but, given their low cost, this was of little import and broadly similar products were used for all applications.

The higher cost of alternative materials, caused by the need to coat fabrics to reduce permeability in order to achieve acceptable performance, led to a split into two markets. A higher price, essentially industrial one was largely met by 400g/m2 glass fabrics coated on both sides with silicone rubber while a much cheaper, primarily domestic one was met by uncoated glass fabrics of ca, 350g/m2. Although sold in huge numbers, these latter blankets were largely ineffective and their sale has now been banned. Fire blankets must now comply with BS 6575, which includes construction and packaging tests as well as fire extinguishing ones.

This change led to a large demand for a cheap textile-based product capable of conversion to fire blankets complying with BS 6575. One such product comprises a pvc membrane loosely stitched between two light glass fabrics. However, the possibility that, in a fire toxic fumes might be generated by the pvc militates against it and solutions which do not involve such risks have been widely sought.

One obvious alternative, variants of which have been produced by several manufacturers, is to make lighter versions of the industrial product. These have mostly been based on the glassweaving industry standard 200g/m2 plain weave fabric, though one company has used a half-matt fabric. In all cases silicone rubber polymer coating weights of 35-40g/m2/side have been used.

Although all have passed BS 6575 and are resistant to attempts to induce cracking by severe, short-term folding, a commonly observed problem is occasional random cracking on storage in a more gently folded form. Neither the coating weight nor type of silicone material appear to have much influence on this behaviour, which may arise from small batch-to-batch variations in the polymer and/or glass dressing. Either way, the products are insufficiently consistent for safety-critical applications such as fire blankets, which may remain folded and unused for extremely long, indeed indefinite periods.

Surprisingly, it has now been discovered that the structure of the base fabric exerts a significant, possibly controlling, influence on the cracking behaviour of the coated product, the looser the fabric structure the lower the tendency to crack.

According to the present invention, a fire blanket material comprises a woven glass fibre fabric having an areal density less than 300g/m2 and less than half the number of yarn intersections of a plain weave fabric of the same areal density, coated on both sides with a silicone rubber polymer rendering the fabric essentially impermeable.

The reason for the superior resistance to cracking exhibited by the materials of this invention is not entirely clear but is thought to derive from the ability of looser fabrics to distort more readily than plain weave fabrics and thus to allow applied stresses to be spread more widely and prevent localised failure.

Preferred woven fabric constructions are twills, including variants thereof such as herringbones, stepped and broken twills (satins). Particularly preferred constructions are 2/2 and 3/1 twills, the latter in straight or broken form. Higher twills, such as 6- or 8-shaft satins, although resistant to cracking, can present problems in handling and especially coating, due to their lack of dimensional stability. Knitted fabrics appear to be very resistant to cracking though many lack dimensional stability.

Fabric areal densities of less than 300g/m' are preferred, particularly ones less than 250g/m2.

On test, it proved impossible to induce cracking in test samples of a 200g/m2, 2/2 twill fabric coated with 35-40g/m'/sides of silicone rubber after 4 weeks in the folded state while similarly coated plain weave fabric samples of the same weight and with the same coating have cracked after 2-5 days.

A useful bonus is that, because of their looser structures, fabrics according to the invention drape better than currentlyused ones and thus may seal better round a fire source and permit the use of smaller blankets in some circumstances.

The silicone rubber polymer is preferably applied in an amount in the range from 30g/m2 upwards, on each side of the fabric.

Application levels in the range 35-50g/mi on each side of the fabric give acceptable results, a particularly preferred level being 35-40g/ml.

In this context, BS 6575 requires that the products must be symmetrical, so that a single heaving coating on one side is not acceptable, although it would confer the desired impermeability.

Claims

1. A fire blanket material comprising a woven glass fibre base fabric having an areal density less than 300g/m2 and less than half the number of yarn intersections of a plain weave of the same areal density, coated on both sides with a silicone rubber polymer rendering the fabric essentially impermeable.

2. A fire blanket material according to claim 1 wherein the areal density of the base fabric is less than 250g/m3.

3. A fire blanket material according to claim 1 wherein the areal density of the base fabric is 200g/m2 + 10%.

4.. A fire blanket material according to any preceding claim wherein the fabric construction is a twill weave.

5. A fire blanket material according to any preceding claim wherein the fabric construction is a 2/2 or 3/1 twill weave.

6. A fire blanket material according to any preceding claim wherein the silicone rubber polymer coating is applied at a level of at least 30g/ml on each side of the fabric.

7. A fire blanket material according to any preceding claim wherein the silicone rubber polymer coating is applied at a level of from 35 to 50g/m2 on each side of the fabric.

8. A fire blanket material according to any preceding claim wherein the silicone rubber polymer coating is applied at a level of from 35-40g/m2 on each side of the fabric.

9. A fire blanket material according to any of claims 1-8 having an at least reduced tendency to crack when stored in a folded state.