GB2387351A

GB2387351A - Intumescent fire barrier

Info

Publication number: GB2387351A
Application number: GB0207997A
Authority: GB
Inventors: Alan Schofield
Original assignee: NJT ASSOCIATES
Current assignee: NJT ASSOCIATES
Priority date: 2002-04-08
Filing date: 2002-04-08
Publication date: 2003-10-15
Anticipated expiration: 2022-04-08
Also published as: GB2387351B; GB0207997D0

Abstract

A fire barrier comprises two outer layers 20, 30 of a fire resistant material, sandwiching a middle layer 10 of an intumescent material. The outer layers may comprise metal, glass fibre cloth, or cloth incorporating metal fibres. The middle layer may comprise graphite. Fastening means 50 hold the barrier together under normal conditions and may comprise polyethylene, polypropylene, or other material with a predetermined melting point. Stitching 40 also holds the barrier together and is slack under normal conditions. In response to a given temperature rise, fasteners 50 melt, or otherwise rupture, allowing expansion of middle layer 10. As layer 10 expands, stitching 40 becomes taut, restraining the expansion to a controlled thickness. Alternatively fasteners 40 do not rupture but undergo a controlled expansion. Such a fastener may be a shape memory spring which straightens out above a certain temperature. In this second embodiment the additional stitching 40 is not required.

Description

1 2387351

IMPROVEMENTS IN AND RELATING TO FIRE BARRIERS

Field to the Invention

The present invention relates to fire barriers, and in particular to fire barriers incorporating an intumescent material.

Background to the Invention

Fire barriers are typically used for retarding the spread of a fire through spaces where it is not practical or desirable to build dividing walls. For example, the roof space of a building may be sub-divided by such barriers. 15 Such barriers need to resist penetration by fire and provide heat insulation. Fire barriers are also utilised to offer a level of protection from fire and heat for individuals and items.

Intumescence is the swelling of a material upon heating.

Such expansion of the material is often accompanied by the violent escape of moisture, as the material undergoes a change in state. Many intumescent materials are endothermic, and absorb heat upon expansion. 25 It is known to incorporate intumescent materials within fire barriers. For instance, GB2,250,933 describes a fire barrier or curtain comprising a sheet woven glass fibrous cloth, coated on at least one side with an intumescent 30 material. A fire barrier incorporating such material is relatively thin when in the passive (i.e. unheated) state, but becomes thicker when heat is applied due to the expansion of the intumescent material, thus making the barrier less thermally conductive.

US 5,258,216 describes the fragility of intumescent 5 materials. Intumescent materials are typically rigid and crystalline, and thus coatings of such materials easily break and crumble. Further, production of such coatings normally requires the use of a binder, and often also a solvent, which is frequently undesirable. US 5,258,216 proposes a solution to this problem by forming a sandwich type structure. The intumescent material forms a central layer between two textile sheets, with the two sheets being stitched or sewn to one another so as to entrap and support the intumescent material. 15 Preferred embodiments of the present invention aim to obviate or overcome a problem associated with the prior art, whether referred to herein or otherwise.

Statements of the Invention

In a first aspect, the present invention provides a fire barrier comprising a first fire retardant sheet, a second fire retardant sheet and an intermediate layer lying 25 between said sheets, the intermediate layer comprising an expandable intumescent material; wherein the barrier further comprises fastening means arranged in a first configuration to fasten together the sheets and layer to form a barrier of a first predetermined thickness, and 30 arranged in a second configuration to fasten together the sheets and layer to form a barrier of a second, larger predetermined thickness.

Preferably, the fastening means is arranged to transition from said first configuration to said second configuration upon being heated to a predetermined temperature.

Preferably, the predetermined temperature is selected from the following group of temperatures: 50'C, CO0C, 70'C, 80'C, 90'C, 100'C, 120-C, 150-C, 200 C, 250 C, 300 C, 400 C, 500 C, 700C, 1000-C.

Preferably, the second configuration is arranged to permit the expansion, at least in part, of said expandable material.

Preferably, the first configuration of the fastening means 15 comprises a sacrificial fastener.

Preferably, the fastener is arranged to at least one of stretch, break, or melt upon reaching a predetermined temperature.

Preferably, the fastener comprises a polymer.

Preferably, the second configuration of the fastening means comprises stitching formed of a fire retardant 25 material.

Preferably, the second configuration of the fastening means comprises a rivet made of fire retardant material.

In a second aspect, the present invention provides a method of manufacturing a fire barrier comprising placing a first fire retardant sheet, a second fire retardant sheet, and an intermediate layer between said sheets, the intermediate layer comprising an expandable intumescent material; wherein the method further comprises applying fastening means arranged in a first configuration to fasten together the sheets and expandable layer to form a 5 barrier of a first predetermined thickness, and suitable in a second configuration to fasten together the sheets and layer to form a barrier of a second, larger predetermined thickness.

Preferably, the method further comprises the step of separating the layers and sheet by a predetermined width when applying the fastening means in said second configuration.

Preferably, the method further comprises the step of holding together and/or compressing together the layers and the sheet when applying the fastening means in said first configuration.

Preferably, the application of the fastening means in a second configuration is performed prior to the application of the fastening means in a first configuration

Brief Description of the Drawings

For a better understanding of the invention, and to show how embodiments of the same may be carried into effect, reference will now be made, by way of example, to the accompanying diagrammatic drawings in which: 30 Figure 1A illustrates a cross sectional view of a fire barrier according to an embodiment of the present invention whilst in a passive, pre- expanded, state; Figure 1B shows the fire barrier of figure 1A whilst undergoing a transition due to the application of heat; Figure 1C shows the fire barrier of figure 1A in the expanded state; Figures 2A-2E illustrates a method of construction of a fire barrier in accordance with another embodiment of the present invention; and Figure 3 illustrates a method of construction of a fire barrier in accordance with a further embodiment. 10

Detailed Description of Preferred Embodiments

As can be seen in figure 1A, the fire barrier comprises three layers of material (10, 20,30), of total thickness 15 x. Preferably, x is within the range 2-10mm.

The outer two layers (20, 30) are formed of sheets of fire retardant material. The fire retardant material is preferably woven glass fabric (e. g. glass fibre cloth), 20 and may be chemically treated to enhance the fire resistant properties. It is preferably capable of maintaining its integrity under the simulated fire conditions of the BS476 part 2 20/22 fire tests for durations of 30, 60, 120, or 240 minutes. In this preferred embodiment, both of the outer layers (20, 30) are formed from the same flexible fire retardant material, of glass fibre cloth within the range 400gm to 600gm.

Sandwiched between the two outer layers (20, 30) is a 30 layer of intumescent material 10. In this preferred embodiment, the intumescent material comprises graphite, and has a thickness of between 1 and 8mm in its unexpanded state.

The layers 10, 20, 30 are secured together by sacrificial fasteners 50. The fasteners 50 are designed to fail in the event of a fire, releasing any compression of the 5 layers. In this embodiment, the fastener is designed to melt at a predetermined temperature, which has been selected in dependence upon the environment in which the fire barrier is designed to be located, and the intended fire retardant properties of the barrier.

In this preferred embodiment, the fasteners are formed of a polymer such as polypropylene or polyethylene. The fasteners are of the type commonly used for clothes labeling, as for instance described within GB2311007. 15 A stitching 40 of fire retardant material passes through each of the three layers (10, 20, 30). In this preferred embodiment, the stitching is also formed of glass fibre having a similar fire resistance to the outer layers (20, 20 30). The stitching is loose whilst the intumescent material is in the unexpanded state, but as explained below is arranged to hold together and limit the movement of the three layers when the intumescent layer has expanded.

Figure 1B shows the fire barrier to which heat has been applied. In the upper portion of the fire barrier, the sacrificial fasteners 50 have melted, allowing the intumescent material to expand to a new width defined by 30 the fire retardant stitching 40, which act as spacers to limit the overall expansion of the thickness of the fire barrier to a predetermined value of x+y. The value of y can be chosen so as to allow the intumescent material to expand to its maximum volume. However, it is preferable that y is chosen so as to allow the intumescent material to expand to less than its maximum volume, so as to maintain structured integrity.

Figure 1C shows the fire barrier in which all of the sacrificial fasteners 50 have been melted, and all of the intumescent material 10 has expanded to its fullest extent. It will be appreciated that there has been an 10 improvement in the insulating qualities of the fire barrier due to the increased separation between the two fire retardant sheets 20, 30. Thus, whilst heat is being applied to one side of the barrier (the left side as shown in the figure) elevating the temperature of the relevant 15 sheet 20 to approximately ARC, the temperature on the other side of the barrier is lower (A-B) C due to the thermal insulation provided by the barrier. As well as providing a barrier to the passage of heat, the fire barrier does of course inhibit the progression of 20 flame/fire.

By providing such a fire barrier that restricts the separation of the fire retardant layers upon heating, the insulation properties of the barrier are controlled. 25 During installation, such barriers are flexible and can be easily manipulated without loss or damage to the intumescent material due to the use of the fasteners 50, which act to hold the intumescent layer between the two 30 fire retardant sheet layers. However, as the fasteners 50 are designed to break upon heat being applied to the barrier, the intumescent material is thus allowed to expand, and so adds to the fire retardant and insulation properties of the barrier. Structural integrity of the barrier is maintained in the expanded state by the provision of the spacers 40 which hold the composite structure together at a predetermined separation of the two outer layers (20, 30).

Figures 2A-2E illustrate how such a fire barrier can be constructed. A first layer of fire resistant material 30 is provided (figure 2A), and overlaid by a layer of 10 intumescent material 10 (figure 2B), which is in turn overlaid by a further layer of fire retardant material 20 (figure 2C).

The three layers are preferably spaced apart during this 15 construction step to provide substantially the same overall thickness as it is envisaged will be the maximum thickness of the fire barrier once the intumescent material has expanded (i.e. a barrier thickness of x+y).

These three layers are then stitched or sewn together using a fire retardant material of a predetermined length, such as treated glass fibre 40 (figure 2D). The sewing technique used may be similar to that used in forming quilts or duvets for beds.

As shown in figure 2E, the layers are then fastened together using sacrificial spacers 50 of predetermined length, arranged to hold the three layers 10, 20, 30 in close proximity so as to form a fire barrier of smaller 30 thickness x.

The above preferred embodiments have been provided by way of example only, and various alternatives will be apparent to the skilled person based upon the teaching of this

specification.

For instance, whilst the fire barrier has been constructed 5 of three layers of material, it will be apparent that the barrier could of course include additional layers.

Whilst the sacrificial fastener has been described as melting at a predetermined temperature, any fastener could 10 be utilised that is suitable for allowing the intumescent material to expand.

For instance, the fasteners could be arranged to break or stretch upon heat being applied to the fire barrier, due 15 to the expansion of the intumescent material stressing the fasteners.

Alternatively, the fasteners could be arranged to be formed of a material coiled like a spring. Whilst the fire barrier is not being heated, the resilience of the coil is sufficient to hold the three layers together.

However, when the fire barrier is heated, due to the expansion forces of the intumescent material and/or the softening effect of the applied heat, the coil is arranged 25 to gradually straighten out so as to allow the two fire retardant layers to separate up to a predetermined distance (i.e. x+y) . Thus, a single fastener can be formed to act as both the sacrificial fastener 50 and the fire retardant spacer 40.

Whilst graphite has been described as being utilised for the intumescent material, any thermal intumescent material could be utilised that is arranged to expand at to a predetermined thickness at a predetermined temperature suitable for the desired application of the fire barrier.

Whilst the layers 20, 30 have been described as being 5 within the range 400gm to 600gm, they can be of any desired weight suitable for the intended application. For instance, they could be as light as 100gm or 50gm, or as heavy as 1000gm or even 200Ogm.

Equally, whilst the fire retardant layers 20, 30 have been described as being formed from glass fibre cloth, any appropriate rigid and/or flexible fire retardent material could be utilised, including sheets of metal, or sheets of cloth incorporating metal fibres. 15 The layers of fire retardant material and intumescent material can be of any predetermined thickness, but each layer is preferably between 0.5 and 5mm thick.

Various manufacturing techniques will be apparent to the skilled person based upon the teaching of the present invention.

For instance, whilst a manufacturing method utilising 25 previously formed layers of material has been described with respect to figures 2A- 2E, it will be appreciated that a fire barrier could be manufactured according to an embodiment of the present invention by weaving one or more of the layers in situ. Such a manufacturing method could 30 utilise techniques that have been developed for forming multiple fabrics in spaced apart layers, and that have been used to manufacture the likes of electric blankets and carpets.

Figure 3 illustrates such a manufacturing method. In this embodiment, the two outer layers 20, 30 are formed of the same fire retardant material. Figure 3 illustrates a cross section through the structure, with the weft threads 121, 122, 123, 124 of the fire retardant material being seen to run across the page, and the warp threads 120 being shown protruding into and out of the page. The threads of the fire retardant material are spaced apart a 10 distance x+y, to allow for the future expansion of the intumescent material. Rods or threads of the intumescent material 110 are inserted between the threads of the outer layers. One or more threads of fire retardant stitching 40 are woven between the three layers as the layers are 15 formed. By simultaneously forming the three layers, the same structure illustrated in figure 2D can be directly realised from the raw components (i.e. threads or rods of the relevant materials), thus simplifying the manufacturing process. It is envisaged that the additional sacrificial fasteners 50 would then be inserted into the resulting three layers, as depicted in figure 2E.

Equally, it will be appreciated that other assembly techniques could be utilised to form the desired structure 25 of the fire blanket, such as knitting.

The reader's attention is directed to all papers and documents which are filed concurrently with or previous to this specification in connection with this application and 30 which are open to public inspection with this specification, and the contents of all such papers and documents are incorporated herein by reference.

All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, 5 except combinations where at least some of such features and/or steps are mutually exclusive.

Each feature disclosed in this specification (including any accompanying claims, abstract and drawings), may be 10 replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features. 15 The invention is not restricted to the details of the foregoing embodiment(s). The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.

Claims

CLAIMS:

1. A fire barrier comprising a first fire retardant sheet, a second fire retardant sheet and an intermediate 5 layer lying between said sheets, the intermediate layer comprising an expandable intumescent material; wherein the barrier further comprises fastening means arranged in a first configuration to fasten together the sheets and layer to form a barrier of a first 10 predetermined thickness, and arranged in a second configuration to fasten together the sheets and layer to form a barrier of a second, larger predetermined thickness.

2. A barrier as claimed in claim 1, wherein said fastening means is arranged to transition from said first configuration to said second configuration upon being heated to a predetermined temperature.

3. A barrier as claimed in claim 2, wherein said predetermined temperature is selected from the following group of temperatures: 50'C, 60 C, 70 C, 80 C, 90'C, 100lC, 120-C, 150'C, 200'C, 250'C, 300'C, 400'C, 500'C, 700'C, 1000'C.

4. A barrier as claimed in any one of the above claims, wherein said second configuration is arranged to permit the expansion, at least in part, of said expandable material.

5. A barrier as claimed in any one of the above claims, wherein a first configuration of the fastening means comprises a sacrificial fastener.

6. A barrier as claimed in claim 5, wherein said fastener is arranged to at least one of stretch, break, or melt upon reaching a predetermined temperature.

7. A barrier as claimed in claim 5 or claim 6, wherein said fastener comprises a polymer.

8. A barrier as claimed in any one of the above claims, 10 wherein said second configuration of the fastening means comprises stitching formed of a fire retardant material.

9. A barrier as claimed in any one of the above claims, wherein said second configuration of the fastening means 15 comprises a rivet made of fire retardant material.

10. A method of manufacturing a fire barrier comprising placing a first fire retardant sheet, a second fire retardant sheet, and an intermediate layer between said 20 sheets, the intermediate layer comprising an expandable intumescent material; wherein the method further comprises applying fastening means arranged in a first configuration to fasten together the sheets and expandable layer to form a barrier of a 25 first predetermined thickness, and suitable in a second configuration to fasten together the sheets and layer to form a barrier of a second, larger predetermined thickness.

11. A method as claimed in claim 10, further comprising the step of separating the layers and sheet by a predetermined width when applying the fastening means in said second configuration.

12. A method as claimed in claim 10 or claim 11, further comprising the step of holding together and/or compressing together the layers and the sheet when applying the fastening means in said first configuration.

13. A method as claimed in any one of claims 10, 11 or 12, wherein the application of the fastening means in a second configuration is performed prior to the application of the fastening means in a first configuration.

14. A fire barrier substantially as described herein with reference to the accompanying drawings.

15. A building structure comprising a fire barrier as claimed in claim 1 or claim 14.

16. A method of manufacturing a fire barrier substantially as described herein with reference to the accompanying drawings.