AU2003262477A1

AU2003262477A1 - Composite Material

Info

Publication number: AU2003262477A1
Application number: AU2003262477A
Authority: AU
Inventors: John Peter Randel
Original assignee: A1 RUBBER Pty Ltd
Current assignee: A1 RUBBER Pty Ltd
Priority date: 2002-11-25
Filing date: 2003-11-25
Publication date: 2004-06-10

Description

COMPOSITE MATERIAL The present invention relates to a composite material. In particular, the present invention relates to a composite material suitable for use as a protective or insulating surface.

The composite material of the present invention may, in one embodiment, be used as a playground surface and for the manufacture of playground equipment.

The playing surface used in playgrounds is preferably selected to attenuate injury as a result of children's falls. The surface that is used under and around playground equipment is preferably sufficiently shock-absorbing to minimise the risk of injury. However, the surfaces used must also provide sufficient traction so as to be navigable. As a result of competing requirements such as these a variety of surface materials have been used in playgrounds.

Asphalt and concrete generally provide an unsuitable material as they provide little or no ability to absorb shock and thus are ineffective in attenuating injury. Other surfaces such as soil or compacted materials are similarly unsuitable due to their lack of an ability to absorb shock and attenuate injury. Whilst grass may provide some ability to attenuate injury, wear in high traffic areas substantially reduces its ability to attenuate injury.

Preferred materials for playground surfaces include loose fill materials.

Loose fill materials generally provide good injury attenuating properties. For example shredded wood products, sand and gravel have been used and these materials provide good shock-absorbing properties and often demonstrate good ability to attenuate serious head injury. The ability of loose filled materials to attenuate injury is generally dependant on the depth of the loose fill material and by its nature it tends to be redistributed from high traffic areas where it is required most.

Whilst loose fill material is effective in attenuating injury, loose fill materials are often difficult to navigate. In particular the use of loose fill material can reduce the accessibility of the playground equipment to the disabled or reduce its accessibility for young children that have yet to develop advanced motor skills.

Because of the difficulties in traversing surfaces of loose fill material, particularly by people in wheel chairs, the use of loose fill materials is undesirable.

Unitary materials have also been used that have shock absorbing properties. For example rubberised mats or agglomerated rubber-like materials held in place with a binder have been used to provide surfaces for playgrounds. The use of post consumer rubber that has been crumbed and then bound together using a binder has found many applications as providing surfacing materials for playgrounds.

Whilst playground surfaces formed from rubber particles bound together provide a degree of injury attenuation, falls onto such surfaces have the potential for causing head injury due to the rapid deceleration and acceleration as the head "bounces" on the surface. It would be desirable to provide a surface having many of the properties of a surface formed from rubber particles adhered together with additional injury attenuation properties.

The composite material of the present invention may, in another embodiment, be used as an insulating or noise and vibration attenuation material.

Underlays for carpet provide noise and vibration attenuation. Materials used as underlays include convoluted foam products formed from polyurethanes and other thermosetting polymers. Materials used to float timber and vinyl floors include polymeric foam materials.

We have now found that by incorporating particles of an impact energy absorbing material into a mixture with rubber particles a composite material niay be formed that provides enhanced injury, noise and vibration attenuation properties.

According to the present invention there is provided a composite material comprising a mixture of particles adhered together wherein said mixture comprises rubber particles and particles of an impact energy absorbing material.

The composite material of the present invention is formed from a mixture of particles adhered together. The mixture includes rubber particles, which rubber particles may be formed from natural or synthetic rubbers. Whilst many virgin rubbers and rubber like materials may be used in forming the composite material of the present invention we have found it particularly advantageous to employ postconsumer rubber particles that have, for example, been produced from process for recycling tyres.

The shape of the rubber particles spheroid or elongate. The rubber particles may be derived from tyre recycling granulators where the particles are generally round. Alternatively the rubber particles may be long and thin such as produced as buffings in tyre retreading processes.

Preferably the particulate rubber is produced from used tyres. Used tyres provide a particularly advantageous source of rubber for such applications as the rubber used to form the tyre is formulated to provide high wear resistance and is thus particularly suited for applications such as playground surfaces.

Preferably the rubber particles have an average size in the range of from 0.6 to 20mm. More preferably the average size of the rubber particles is in the range of from 3 to The particles of an impact energy absorbing material may be selected from a range of materials including expanded polymeric material, pilled fibres, and other shock absorbing or dampening materials.

The particles of impact absorbing material may be of any convenient shape. It is preferred that the impact absorbing particles be spherical or substantially spherical although elongate particles may also be suitable.

Typically the particles of impact absorbing material have an average particle size similar to that of the rubber particles. Preferably the average particle size of the impact absorbing material is in the range of from 0.6 to 20mm, more preferably in the range of from 3 to The mixture of particles preferably includes rubber particles and particles of impact absorbing material in a volume ratio in the range of from 1:9 to 9:1. It is preferred that the volume ratio of rubber particles to particles of impact absorbing material be in the range of from 1:1 to 4:1, more preferably the volume ratio of rubber particles to particles of impact absorbing material is in the range of from 3:2 to 4:1, most preferably the volume ratio of rubber particles to particles of impact absorbing material is 7:3.

The mixture of particles may also include particles of other, preferably inert materials such as fillers, colouring materials.

The addition of further particulate materials may be up to 10% by volume. With the addition of further particulate materials to the mixture the volume ratio of rubber particles to particles of impact absorbing materials should remain within the ranges specified above.

Preferably the mixture of particles is homogeneous with particles of different materials being evenly distributed throughout the mix. The mixture may be formed by blending in any convenient mixing apparatus such as a mixer of the type

I

used for producing cement or any other convenient type of mixing apparatus, preferably of the type used for high shear mixing.

The mixed particles are adhered together to form the composite material. It is preferred that the particles are adhered together using a binding agent.

Preferably the binding agent is a polyurethane based adhesive. Alternatively the binding agent may be a latex adhesive or an acrylic adhesive. The binding agent may be cured using heat, such as in the form of steam.

In one embodiment of the present invention the composite material is particularly suited to form a playground surface where the impact attenuation properties such that the rebound of a falling child's head may be minimised as is its deceleration. It is known that the maximum tolerable deceleration of a human head is 300g applied for a few milliseconds only.

The selection of particles of expanded polymeric materials for use as the impact absorbing material allows the production of a playground surface with enhanced injury protection properties.

The particles of expanded polymeric material may be of any convenient shape. It is preferred that the expanded polymeric particles be spherical or substantially spherical although elongate particles may also be suitable.

Particles of expanded polymeric materials include expanded polystyrene and expanded polyurethane particles. It will be apparent to those skilled in the art that other expanded polymeric materials may be used where such expanded polymeric materials provide a high degree of deformation and a slow or delayed elastic response (low rebound). In this way the particles of expanded polymeric material provide a shock absorbing capacity that is integrated with the resilience of the rubber particles.

The shape of the particles of expanded polymeric material may be spheroid or elongate. The particles of expanded polymeric material may be derived granulated recycled plastics. Alternatively the particles of expanded polymeric material generally round granulated polyurethane foams. The particles of expanded polymeric material may be long and thin such as produced as chopped, extruded polymeric foam.

Typically the particles of expanded polymeric material have an average particle size similar to that of the rubber particles. Preferably the average particle size of the expanded polymeric material is in the range of from 0.6 to 20mm, more preferably in the range of from 3 to The composite material may be formed in situ and, in the case of forming a playground surface, may be laid by depositing a mixture of particles and adhesive on a substrate and subsequently curing the adhesive. Alternatively tiles of composite material may be formed and then laid on a substrate to form a surface for a playground. Tiles may be formed by forming a thin layer of composite material and subsequently cutting the material into tiles. Alternatively, a block of composite material may be formed and the tiles cut from the block of cured composite material.

The composite material of the present invention may also be advantageously used in the manufacture of sculptures, such as for playgrounds and the like. The shock absorbing properties of the composite material of the present invention permit such sculptures to be robust in construction and able to attenuate any injury that may result from a child impacting with the sculpture: These properties also make the composite material of the present invention useful in producing sculptures in other applications. The use of expanded polymeric material reduces substantially the weight of any article formed therefrom, thus allowing it to be more readily handled than a corresponding article formed simply from particulate rubber bound together.

The composite material of the present invention when used to form a playground surface or any other article advantageously includes a surface coating.

Suitable surface coatings include synthetic grass, paint such as an acrylic waterproofing membrane or a surface layer of rubber particles adhered together. In a preferred aspect of this embodiment of the present invention the composite material described above forms a substrate layer over which a layer of particulate rubber adhered together is formed and a surface coating layer of an acrylic waterproofing membrane is formed over the layer of adhered rubber particles.

In a preferred form of this embodiment of the present invention provides a ground surface comprising a base layer of a composite material comprising a mixture of particles adhered together wherein said mixture comprises rubber particles and particles of an expanded polymeric material, overlaid with top layer of rubber particles adhered together.

In a second embodiment of the present invention there is provided a composite material for use in noise and vibration attenuation. In the second embodiment the impact attenuation material are particles of pilled fibres.

Pilled fibres for use in the second embodiment of the present invention may be formed from a wide range of fibre types. The pilled fibres are believed to act to damp the rubber particles in the composite material. It will be understood by those skilled in the art that by the term "pilled fibres" it is meant a ball or agglomeration of fibres loosely associated to form a highly compressible particle such as may be formed by rubbing a multiplicity of fibres together.

Whilst a wide range of fibres may be pilled to form pills for use in the present invention we have found that the chopped nylon fibre derived from processes such as tyre recycling may be advantageously employed. The chopped nylon may be fluffed to separate the fibres from the cord form in which they are incorporated in the tyres and then the fibres may be entangled to form loosely agglomerated bunches or pills for incorporation in the composite material.

The pilled fibres may be formed into pills of any convenient shape. It is preferred that the pills be spherical or substantially spherical although elongate particles may also be suitable.

Typically the pills of fibre have an average particle size similar to that of the rubber particles. Preferably the average particle size of the pills of fibre is in the range of from 0.6 to 20mm, more preferably in the range of from 3 to The mixture preferably includes rubber particles and pilled fibres in a volume ratio in the range of from 1:9 to 9:1. It is preferred that the volume ratio of rubber particles to pilled fibres be in the range of from 1:1 to 4:1, more preferably the volume ratio of rubber particles to pilled fibres is in the range of from 3:2 to 4:1, most preferably the volume ratio of rubber particles to pilled fibres is 7:3.

Tiles of composite material may be formed and then laid on a substrate to form a surface for a playground. Tiles may be formed by forming a thin layer of composite material and subsequently cutting the material into tiles. Alternatively, a block of composite material may be formed and the tiles cut from the block of cured composite material.

Advantageously, the composite material of the second embodiment of the present invention is also suited for applications other than playground surfaces. In one preferred application the composite material is suited for use in noise and vibration isolation products. The composite material is also particularly suited for use as a flooring (eg. timber or ceramic) or carpet underlay. Suitably the underlay may be in the form of a convoluted sheet.

The present invention will now be described with reference to the following examples and accompanying drawings that serve to illustrate, but not limit, the scope of the present invention.

EXAMPLES

In the examples the same test procedures were performed on two thick test specimens. Both shock pad specimens had a 15mm thick, 700kg/m 3 density recycled rubber tile placed on top to replicate an actual on-site application.

Example 1 Test Specimen No. 1, Formula ratio per cubic metre Rubber Crumb Granules (1-4mm) Polystyrene Beads (1-5mm) Polyurethane Binder (Liquid) TOTAL 100% Total Weight per m 3 500kg Test Procedure and Result An average rebound height was calculated from 10 repetitive drops from 1.5 metres onto the test specimen at various points using a 100mm diameter 3kg steel ball. All measurements were recorded from the bottom centre of the ball.

The average rebound height recorded was 410mm.

Comparative Example 1 Test Specimen No. 2, Formula ratio per cubic metre Rubber Crumb Buffings (8 mm) 96% Polyurethane Binder (Liquid) 4% TOTAL 100% Total Weight Per m 3 570kg Test Procedure and Result An average rebound height was calculated from 10 repetitive drops from 1.5 metres onto the test specimen at various points using a 100mm diameter 3kg steel ball. All measurements were recorded from the bottom centre of the ball.

The average rebound height recorded was 540mm.

Example 2 In example 2 the same test procedures were performed on two thick test specimens. Both shock pad specimens had a 15mm thick, 700kg/m 3 density recycled rubber tile placed on top to replicate an actual on-site application.

Test Specimen No. 1, Formula ratio per cubic metre Rubber Crumb Granules (1-4mm) 54% Fluffed Nylon Pills (1-5mm) 36% Polyurethane Binder (Liquid) TOTAL 100% Total Weight per m 3 500kg j

Claims

1. A composite material comprising a mixture of particles adhered together wherein said mixture comprises rubber particles and particles of an impact energy absorbing material.

2. A composite material according to claim 1 wherein the particulate rubber is produced from used tyres.

3. A composite material according to either claim I or claim 2 wherein the rubber particles have an average size in the range of from 0.6 to

4. A composite material according to claim 4 wherein the average size of the rubber particles is in the range of from 3 to A composite material according to any one of claims 1 to 4 wherein the average particle size of the impact absorbing material is in the range of from 0.6 to

6. A composite material according to claim 5 wherein the average particle size of the impact absorbing material is in the range of from 3 to

7. A composite material according to any one of claims 1 to 6 wherein the mixture of particles includes rubber particles and particles of impact absorbing material in a volume ratio in the range of from 1:9 to 9:1.

8. A composite material according to claim 7 wherein the volume ratio of rubber particles to particles of impact absorbing material be in the range of from 1:1 to 4:1.

9. A composite material according to claim 8 wherein the volume ratio of rubber particles to particles of impact absorbing material is in the range of from 3:2 to 4:1.

10. A composite material according to claim 9 wherein the volume ratio of rubber particles to particles of impact absorbing material is 7:3.

11. A composite material according to any one of claims 1 to 10 wherein the particles are adhered together using a binding agent.

12. A composite material according to claim 11 wherein the binding agent is a polyurethane based adhesive.

13. A composite material according to claim 11 wherein the binding agent is a latex adhesive or an acrylic adhesive.

14. A composite material according to any one of claims I to 13 wherien the impact absorbing material is an expanded polymeric material. A composite material according to claim 14 wherein the expanded polymeric material is selected from the group consisting of expanded polystyrene and expanded polyurethane particles.

16. A sculpture formed from a composite material according to any one of claims I to

17. A playground surface formed from a composite material according to any one of claims 1 to

18. A playground surface according to claim 17 further including a surface coating.

19. A playground surface according to claim 18 wherein the surface coating is selected from the group consisting of synthetic grass, paiht, waterproofing membrane, a surface layer of rubber particles adhered together and combination thereof.

20. A composite material according to any one of claims 1 to 13 wherein the impact absorbing particles are pilled fibres.

21. A composite material according to claim 20 wherein the pilled fibres include fibres of chopped nylon fluffed to separate the fibres from the cord form in which they are incorporated in the tyres and then the fibres may be entangled to form loosely agglomerated bunches or pills for incorporation in the composite material.

22. A noise and vibration attenuation material formed from a composite material according to either claim 20 or claim 21.