tyr003 04 21 aug 07 final version

8/3/2019 Tyr003 04 21 Aug 07 Final Version

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Wrap Tyres Programme

Composite construction products

from waste tyres

Turning waste tyres into new products for the construction industry.

Project code: TYR0003 ISBN: 1-84405-351-2

Research date: Nov 2006Mar 2007 Date: March 2007


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Front cover photograph: Plasterboard sandwich panel with a rubber core derived from waste tyres.

IMPORTANT NOTE & DISCLAIMER

WRAP and BRE believe the content of this report to be correct as at the date of writing. However, factors such as prices, levels of recycled content and regulatory

requirements are subject to change and users of the report should check with their suppliers to confirm the current situation. In addition, care should be taken in using

any of the cost information provided as it is based upon numerous project-specific assumptions (such as scale, location, tender context, etc.).

The report does not claim to be exhaustive, nor does it claim to cover all relevant products and specifications available on the market. While steps have been taken to

ensure accuracy, WRAP cannot accept responsibility or be held liable to any person for any loss or damage arising out of or in connection with this information being

inaccurate, incomplete or misleading. It is the responsibility of the potential user of a material or product to consult with the supplier or manufacturer and ascertain

whether a particular product will satisfy their specific requirements.

The listing or featuring of a particular product or company does not constitute an endorsement by WRAP and WRAP cannot guarantee the performance of individual

products or materials. For more detail, please refer to WRAPs Terms & Conditions on its web site: www.wrap.org.uk

Published by

Waste & R esources The Old Academy Tel: 01295 819 900 Helpline freephone

Action P rogramme 21 Horse Fair Fax: 01295 819 911 0808 100 2040

Banbury, Oxon E-mail: [email protected]

OX16 0AH


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Executive summary

The construction industry consumes approximately 420 million tonnes of products per year, and therefore utilises

large quantities of raw materials. Alternatives to primary materials in construction products are already widely

used; examples include the use of construction and demolition wastes as aggregates, timber wastes in composite

board products and by-products from steel-making in the manufacture of mineral wool. Examples such as these

contribute to continued improvement of the green credentials of the construction industry.

By 2005, there were over 480,000 tonnes of used tyres arisings per year in the UK (Environment Waste Strategy,

2007). Since July 2006, both whole and shredded tyres have been banned from landfill, following implementation

of the UK Landfill Regulations. There is therefore an urgent need to find new applications and markets for tyre

arisings.

In November 2005, BRE was commissioned by WRAP to identify applications for waste tyres in construction

products. The principal objective of the project was to use tyre waste to develop and provide industry with a

number of new sustainable, viable, low-cost composite construction products that are easy to manufacture. The

aim of the project was to contribute to the remit of WRAP to reduce the volume of waste tyres going to landfill,

and to research new market opportunities for waste tyre-derived materials. The project was completed in March

2007.

The objectives of the project were:

to understand and characterise waste-tyre raw materials; to establish the properties, reactivity and functionality of these raw materials for the development of

construction composites;

to develop a matrix-used tyre-performance-demand model for used tyre-based composites; to investigate the modification of a new generation of reprocessed used tyre constituents, if necessary; to develop new processes for manufacturing these composites.

The main tasks undertaken under the project were as follows:

property testing of the tyre-derived raw materials, including recommendations on raw material modifustry consultative group;

ication;

laboratory manufacture of prototype products identified by BRE and an indassessment of the properties of the developed prototypes;development of a matrix of used tyre vs. property demand for the plasterboard/tyre buffings-derived panel;

ings product;

assessment of economic and market factors.

t and

dix A.

aken further at this stage, some of them because they appear to be uneconomical given

urrent cost models.

redential

te Services, CostDOWN Consultancy, Lafarge

Plasterboard, Hyperlast, Apollo Adhesives and Kingpin.

industrial assessment of the plasterboard/buff

During the project, a series of prototypes based on a range of waste tyre-derived raw materials (shreds, dus

buffings) with plasterboard, oriented strand board (OSB) and laminate floor were produced. A plasterboard

sandwich panel with a rubber layer in the middle was successfully developed and a variety of this subsequently

tested by Lafarge Gypsum, who were interested in its acoustic insulation properties. Further work is still needed

to bring this product to market, but results so far are promising. The results of the tests are given in AppenA range of other potential products were prototyped in the laboratory, including underlay for use beneath

laminate floors, and sandwich panel for door or wall partition with OSB. However (with industry agreement),

these have not been t

c

Members of an industry consultative group contributed to the project through the provision of testing facilities,

materials and advice. Key contributors were: Murfitts Industries, Charles Lawrence International Ltd, C

Environmental Ltd, Tyre Recovery Association, Biffa Was

Composite construction products from w aste tyres 1


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Contents

1.0 Int roduct ion ............................................................................................................................. 32.0 Descript ion of the proj ec t ........................................................................................................ 6

2.1 Assessing tyre-derived raw materials ......................................................................................6 2.2 Used tyre-performance-demand model ...................................................................................6

2.3 Manufacture and characterisation of prototype products ..........................................................63.0 Resu lt s and di scussion ............................................................................................................. 83.1 Assessing tyre-derived materials.............................................................................................8

3.1.1 Products available from tyre recyclers ........................................................................83.1.2 Physical properties of the tyre shreds .......................................................................10

3.2 Tyre granules bound with resin ............................................................................................103.2.1 Initial trial mixes .....................................................................................................103.2.2 Initial product development.....................................................................................113.2.3 Further prototypes: laminate floor underlay and plasterboard sandwich panels...........143.2.4 Tests on the tyre/resin mixes...................................................................................153.2.5 Used tyre-performance-demand model.....................................................................183.2.6 Summary of the prototype development...................................................................19

3.3 Market survey .....................................................................................................................193.3.1 Market drivers for the use of tyres in composites ......................................................203.3.2 Overview of the market for recycled tyre materials and resins ...................................203.3.3 Market survey of acoustic plasterboard products.......................................................213.3.4 Market survey of acoustic underlay for laminate flooring ...........................................22

4.0 Envi ronm enta l aspects ........................................................................................................... 22 5.0 Conc lusions ............................................................................................................................ 236.0 Nex t steps .............................................................................................................................. 237.0 Commercial isat ion ................................................................................................................. 238.0 Sources of informa tion consulted .......................................................................................... 25

8.1 References..........................................................................................................................258.2 Websites investigated during market survey..........................................................................25

8.2.1 Tyres .....................................................................................................................25

8.2.2 Products with tyre-derived rubber content................................................................258.2.3 Acoustic underlays ..................................................................................................25 8.2.4 Acoustic boards ......................................................................................................25 8.2.5 Dry lining/partition/ceilings/floors.............................................................................258.2.6 Tyre-derived materials: ...........................................................................................26

Appendix A: Used tyre appl icat ion vs propert y requ irem ent s............................................................ 27 Appendix B: Lafa rge Pl ast erboard test r esu lts................................................................................... 29 Appendix C: Resins considered i n t he project .................................................................................... 31



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1.0 Introduction

The construction industry consumes approximately 420 million tonnes of products per year, and therefore utilises

large quantities of raw materials. Alternatives to primary materials in construction products are already widely

used. Examples include the use of construction and demolition wastes as aggregates, timber wastes in composite

board products and by-products from steel-making in the manufacture of mineral wool. Examples such as these

contribute to the continued improvement of the green credentials of the construction industry.

By 2005, there were over 480,000 tonnes of waste tyre arisings in the UK per year. Since July 2006, both wholeand shredded tyres have been banned from landfill, following implementation of the UK Landfill Regulations.

There is therefore an urgent need to find new applications and markets for waste tyre arisings.

The current uses for waste tyres are listed in Figure 1.

Figure 1 Current uses for waste tyres

Uses and disposal routes Comment Tonnes

Export (used casings) The tyre casing comprises the entire main structural body

of a tyre, often called the carcass.

35,039

Retread (UK and export) The preferred method for re-using worn tyres as it

effectively doubles the life of the tyre. Buffings are

generated in the process.

57,427a

Energy recovery Used as a fuel (primarily in cement kilns). 85,750b

Landfill engineering Whole or shredded tyres can be used in landfill

engineering, for example as part of leachate collections

systems.

59,000c

162,500dMaterial recovery (shred/crumb) Recycled material from end-of-life tyres processed into

different grades of shred and crumb.

a BRMA, RMA & industry figures.b Returns from industry cement kilnsc Based on DTI Landfill Operator survey 2005d Returns from industry.

Used Tyres 2005 - End Uses

(486 578 tonnes)

Material recovery

(shred/crumb)

33%

Energy recovery

17%

Export of used

casings

7%

Re-used as part

worn tyres

7%

Retread UK &

export

12%

Other re-use

0%

Landfill loss

12%

Landfill

engineering

12%

Figure 2 Waste tyre end uses in the UK (source: DTI tyre statistics: 2005)



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It can be seen from Figure 2 that approximately half of all waste tyres undergo material or energy recovery.

A Publicly Available Specification, PAS107, has recently been prepared by the British Standards Institution (BSI) in

collaboration with WRAP to provide a specification for producing grades of size-reduced rubber of consistent and

verifiable quality. A summary sheet for the specification (PAS107: 2007, WRAP/BSI) has been produced by

WRAP). The grades and characteristics of material specified, and their PAS codes, are given in Figure 3.

Figure 3 Characteristics of size-reduced tyre materials (source: PAS107: 2007, WRAP/BSI)

Size range (maxim um dimension)

mmMaterial

CategoryMinimum Maximum

Other characteristics

Rough Cuts 300 None Exposed wire and textiles 1)

Clean Cuts 300 None Less than 5% exposed wire and textiles2)

Rough CutShred

50 300 Exposed wire and textiles

Clean Cut Shred 50 300 Less than 5% exposed wire and textiles2)

Rough Cut Chips 10 50 Exposed wire and textiles

Clean Cut Chips 10 50 No exposed wire. Less than 5% exposed

textiles 2)

Granulate 1.0 10 Free from exposed wire and textiles

Powder 0 1.0 Free from exposed wire and textiles

Fine Pow der 0 0.5 Free from exposed wire and textiles

1) All exposed wire and textiles shall be firmly attached to the body of the rubber fragments

2) Upon Visual Inspection

This project researches the potential uses of tyre shred, crumb or buffed materials that are categorised under

material recovery in Figure 2. The materials assessed fall within the categories RS, CC, G and P (Rough cut

shred, Clean cut chips, Granulate and Powder respectively) according to PAS107. However, this project was

undertaken before the issue of PAS107 and hence the terminology used will differ slightly from the PAS107

terminology.

In November 2005, WRAP commissioned the BRE consultancy to identify applications for waste tyres inconstruction products. The principal objective of the project was to use tyre waste to develop and provide

industry with a number of new sustainable, viable, low-cost composite construction products, which are readily

attainable. The aim of the project was to contribute to WRAPs remit of reducing the volume of waste tyres going

to landfill and to research new market opportunities for waste tyre-derived materials The project was completed

in March 2007.

This report describes the methodology used to identify potential products for the construction industry using

waste tyres, from the classification of the various tyre shreds available to the technical development and testing

of prototypes, and assessment of the market potential for the prototypes developed.

During the project, a series of prototypes based on a range of used tyre-derived raw materials (shreds, dust and

buffings) with plasterboard, oriented strand board (OSB) and laminate floor were produced. A plasterboardsandwich panel with a rubber layer in the middle was successfully developed and a variety of this subsequently

tested by Lafarge Gypsum, who were interested in its acoustic insulation properties. Further work is still needed



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to bring this product to market, but results so far are promising. The results of the tests are given in Appendix A.

A range of other potential products were prototyped in the laboratory, including underlay for use beneath

laminate floors, and sandwich panel for door or wall partition with OSB. However (with industry agreement),

these have not been taken further at this stage, in some cases because they appear to be uneconomic given

current cost models.



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2.0 Description of the projectThe aim of the project was to utilise tyre waste to develop and provide industry with a number of sustainable,

viable, low-cost composite construction products. The overall objectives of the project were achieved through a

number of secondary objectives:

understanding and assessing the primary reprocessed raw materials arising from waste tyres when existing

recycling and recovery processes are adopted;

establishing the property profile of the waste tyre raw materials relevant to the development of composites;

examining the reactivity and functionality of the reprocessed waste tyre raw materials;developing new processes (on a pilot or laboratory scale) for the manufacture of composites based on

recycled tyres;

assessing the market potential for the product(s) developed.

2.1 Assessing tyre-derived raw materials

The main tyre-derived raw materials (shreds, granules, buffings) were assessed for specific gravity and particle

size, shape/appearance/composition. It was not considered necessary, as originally set out in the project

proposal, to formally assess the wettability or detailed microstructure of the rubber since observations of the

workability of the wet mixes was adequate to optimise the blend of rubber and resin.

2.2 Used tyre-performance-demand model

A range of tyre-derived raw materials and potential products were initially considered under the project and

evaluated on the basis of the cost of competitor products. Following an evaluation on that basis, the most

successful prototype (technically and commercially) proved to be a panel based on resin-bound rubber buffings

bonded to plasterboard. A matrix was subsequently developed for plasterboard/buffings composite sandwich

panel products to identify the functional requirements required of the product in the envisaged end-use. In

developing this model, the following questions/issues were considered:

What does the envisaged application demand in terms of product function?

Mechanical performance (stiffness, strength, etc)

Other physical performance (fire resistance, noise attenuation, durability, appearance, etc)

Cost (effectively dictated by the costs of competitive products)

What are the key aspects of the composition of the envisaged product that will enable it to be fit-for-purpose?

How much (indicative) energy will be required to break down the source tyres?

What are the current competitive products?

Price. In some cases identification of direct competitors is not straightforward. Indicative prices givetarget range.

Strengths and weaknesses.

The results of the assessment are given in Section 3.2.5 and Appendix A. Here, the performance and cost of the

successful composite is compared in relation to service classes for plasterboard and competitor acoustic boards.

2.3 Manufacture and characterisation of prototype products

A series of prototypes (comprising a rubber layer and one or more stiffer layers) were developed in BREs

laboratories. These comprised: a wall sandwich panel, plasterboard/rubber stud wall panels, and laminate floor

underlay. The materials utilised in the composites with a tyre-derived rubber layer were plasterboard, laminate

flooring or oriented strand board. Mixes (rubber buffings or shreds) bound with resin were also produced and

cast into sheets for assessment.



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The tyre shreds/resin were assessed (in terms of curing time, workability and quality of binding) in relation to

temperature, resin type and percentage resin content. The rubber buffings/resin were assessed for water vapour

permeability, water absorption and moisture swelling.

The prototypes were assessed for the following properties:

Stiffness (all-visual assessment)

Bonding of rubber layer to substrate (all-visual assessment)

Fire resistance (OSB/rubber sandwich panel only)

Stiffness (plasterboard/buffings only)

Impact resistance (plasterboard/buffings only).

Assessment of the thermal conductivity was not considered worthwhile as it was not relevant to the expected end

uses of the composites.



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3.0 Results and discussion3.1 Assessing tyre-derived materials3.1.1 Products available from tyre recyclersThe raw material composition of car tyres is different from lorry tyres. Lorry tyres have a higher proportion of

natural rubber, a lower proportion of fibre and a greater wall thickness. By contrast, car tyres are made of

synthetic rubber, have a higher proportion of steel and fabric and are therefore less profitable to re-process. This

means that markets for processed truck tyres are better developed than those for car tyres.

This project initially examined products derived from truck tyres with a low degree of processing. However, a

decision was made to concentrate mainly on finding new applications for materials derived from processing car

tyres, for which there is an excess of supply over demand.

The recycling process for tyres consists of various stages. Depending on which level of processing is used,

different materials outputs are available. Rubber shreds can be produced in different sizes depending on the

requirements for the end-use applications. Product prices for shredded tyres generally increase dramatically with

the degree of processing (and reduction in particle size). The most common way to recycle tyres is to use a

mechanical shredder. However, other techniques are now available, such as water jetting and cryogenic

processing (liquid nitrogen) (Waste Management News, 3/10/06; Slater 2006). These may produce feedstocks at

an equivalent or lower cost to other recycling methods.

The main processed tyre raw materials currently available can be summarised as follows:

Shreds/crumb

Tyre shreds and crumb are processed materials that are available in various particle sizes. In general, the finer

the material, the higher the end value (as there are more valuable end uses). However, finer materials do require

greater processing, which also incurs additional cost.

Dust

An unavoidable waste (not deliberately produced) from the production of shreds. The amount of dust produced

depends on the nature of the end product (finer shred leads to more dust). It has relatively low value and no

current uses. Following the ban on tyre material to landfill, dust is currently stockpiled.

Buffings

Buffings are an unavoidable fibrous residue derived from the tyre retreading process, in which the existing tread

is removed and replaced with new tread. Buffings have a relatively low value but are of particular interest to

composite manufacturing companies, due to their fibrous shape, potential interlock properties and small particle

size. Available amounts are expected to increase as a result of initiatives to promote the advantages of retreaded

tyres.

Figure 4 details the shreds and powders derived from tyre recycling that were collected and assessed for the

project.



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Figure 4 Description of the tyre shreds collected for the project

Step of recycling

process

Description of product {includes category code as defined in PAS107}

1. Initial

shredding

Coarse shred: 3050mm, contains steel and fibre

(picture shows example of truck tyre). 30 pieces of

coarse shreds were examined (60% contained only

steel, 20% steel and fabric, 20% fabric only){Rough cut shred, RS}

Size (in mm)

Length Width Thickness

Min. 30 11 6

Max. 144 74 17

Mean 76.6 41 11.2 1 cm

2. Removal of

steel

According to one industry source, car tyres contain

approximately 30% steel. The tyres are shredded

to 1525mm size and the steel is removed

magnetically from the shreds. Approximately 8%

of the rubber remains adhered to the steel.3. Shredding of

rubber

Shreds: 2550 mm, contain rubber and fibres

(picture shows example of car tyre) {Clean cut

chips, CC}

4. Removal of

fibres

Granules: 25mm, rubber only (picture shows

example of car tyre) {granulate, G}

1 cm

1 cm

5. Shredding

by-product

Powder:


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3.1.2 Physical properties of the tyre shredsThe density of various types of tyre shreds d ove was characterised. Results are shown in Figure 5.

igure 5 Density measurement of various tyre shreds from truck tyres

uffings

escribed ab

F

Coarse shreds Shreds Granules B

ensity (kg/m3) 1,460* 1,150* 1,060* 1,150*D*data checked and agreed by industry partne densit typi 500kg/m3 depending on particle

.2 Tyre granules bound with resin1

A series of experiments was carried out at BRE in order to find out the reactivity of car tyre granules with binders

curing time

perature on setting time and binding quality

g quality of tyre granules.

he resins used were all isocyanates, specially designed pre-polymers that can also be used for the manufacture

*

The resins are all manufactured from petroleum sources. The environmental impact of these resins (in terms of

he aim was to produce a well-bonded product with the minimum quantity of resin and at a moderatet of water

the

he results of the trial mixes (using the car tyre granulates) are summarised in Figure 6. The following

have any effect on the quality of the curing: curing at 60 C binds the

quality of the product. The curing time can be as short as

C needed was at least 5% for rubber granules to bind effectively (mixes 11 to

penetrate the strand sufficiently

rs. Bulk ies are cally 400

size

33.2. Initial trial mixes

and to optimise the binding systems both for manufacture and performance of the composites produced. The

following mix parameters were used to establish the quality of the mix:

effect of tem

effect of resin content on binding quality of tyre granules

comparison of resin types in terms of their effect on bindin

Tof reactive hot melts. The isocyanate resins solidify to form a bond and cure under the action of atmospheric andsubstrate moisture to form a product which will not re-melt. Three different types were used (all supplied by theproject partners):

Resin A: Different supplier, but with similar properties to B and C

Resin B: Same supplier as Resin C (viscosity of 775mPa.s at 25 C)

Resin C: Same supplier as Resin B (viscosity of 1,800mPa.s at 25 C).

manufacture and product life cycle) has not been assessed. However, health and safety precautions do have tobe followed. Appendix A gives further details.

Ttemperature (60 C or less). As moisture is an essential ingredient in the curing process, a small amounwas added either during mixing or after compaction. The resin was mixed with the rubber in a bowl mixer. Themixed material was tamped by hand into wooden moulds which were sealed in aluminium foil. Pressure wasapplied through a top board and G-cramps. Heat was applied to the sealed packages in an oven to acceleraterate of curing. With one mix (mix 8), an attempt was made to line the mould surfaces with strand (the woodmaterial used in OSB).

Tobservations were made of mixes 114:

It appeared that temperature did notrubber granules as well as at 160 C (mixes 35).

Temperature only affected the curing time, not the

5 minutes with heat applied.

The minimum amount of Resin

14). However, 4.5% of Resin A was sufficient to bind the granules (mix 9).

It was possible to bond the resin/granule mix with strand as the resin did not

(mix 8).

*This is the SI unit for dynamic viscosity. One Pa.s is equivalent to one newton-second per square metre (Ns m2). The unit is

the viscosity of a fluid in which a tangential force of 1 Newton per square metre maintains a difference in velocity of 1

centimetre per second between two parallel planes 1 centimetre apart.



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It is important to note that the amount of resin required varies with the surface area of the rubber, i.e. the

coarser the rubber shred, the less resin is required. Also, fabric fibres present in the rubber shred increase the

resin absorption of the product, therefore requiring greater volumes.

Figure 6 Initial trial mixes (car tyre-derived rubber granulates/resin)

Mix

no.

Curing

timeaTemperature R esin type Resin (%

wt)

Water (%

wt)

Result/

comments

1 Overnight 60 C Resin C 1.6% None Not cured

2 7 hrs 60 C Resin C 1.6% 2cm3 sprayedonto surface

Cureda

Effect of temperature

3 30 min 160 C Resin C 4.5% 4.5% Cured



Reduced resin content

6 5 min 160 C Resin C 2% 2% Cured but

not boundb

7 5 min 160 C Resin C 1% 1% Cured but

not bound

Trial using wood strand and tyre granules (with pressing)

8 5 min 140 C Resin C 4.5% 4.5% Partialadhesion to

strand

Effect of resin (samples were pressed)

9 10 min 160 C Resin A 4.5% 4.5% Cured

10 10 min 160 C Resin B 4.5% 4.5% Not cured

11 5 min 160 C Resin C 3% 3% Cured, not

well bound

12 5 min 160 C Resin C 8% 8% Cured, well

bound

13 10 min 130 C Resin C 6% 6% Cured, well

bound

14 5 min 140 C Resin C 5% 5% Cured, wellbound

a Cured means that the resin had setb Bound means the tyre granulates were bound to each other to form a solid

3.2.2 Initial product developmentResin C had been found to be effective with relatively low proportions of resin. It was therefore used to make the

further mixes to develop composite products. The scope of the project was to consider two application/product

areas:

Laminate floor underlay

Sandwich construction panels, using oriented strand board (OSB) and plasterboard.

Several samples were made using Resin C, and various rubber materials; see Figure 7 for details.



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Figure 7 Description of the initial prototypes developed

Prototype Application Rubber

used

Other

material

used

Comment

Prototype 1: Sandwich

panel for door

or partition

Truck tyre

shred

(50mm

thick)

OSB High density,

difficult to cut panel

due to presence of

steel. Coarse

shreds did not bondtogether well,

therefore the panel

edges had to be

closed with wooden

edge pieces.


panel for wall

partition

Truck tyre

powder

(12mm

thick)

Plasterboard Good bonding of

tyre with

plasterboard

good potential

Prototype 3: (side, top and bottom view) Laminate floor

underlay

Truck tyre

powder

(6mm

thick)

Laminate

floor board

Good bonding of

tyre with laminate

floor good

potential



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panel for door

or partition

Truck

tyres.

Shreds

(12mm

thick)

OSB Good bonding of

tyres with the OSB

Prototype 5: No picture available; the sample

was used for fire testing see schematic

below

Sandwich

panel for door

or partition

Truck tyre

granules

25mm.

(100mm

thick)

OSB Good bonding of

tyres with OSB.

Figure 8 Schematic of Prototype 5

The prototypes developed were discussed with the project partners. It was decided that the subsequent activities

should concentrate on the use of car tyre-derived material (for which there is a need to develop new markets),

rather than truck tyre-derived material for which high-value markets, such as safety surfacings, are already well

developed.

The industrial partners also highlighted the point that, to be of interest, new construction products containing

tyre-derived material would have to be able to compete on price with existing products. The product type that

was chosen for further investigation was theplasterboard sandwich panel for wall partitions(prototype 6) as this

was thought to be a higher-value application than sandwich panels. These were selected for the following

reasons:

There is an active market for acoustic partitions, floor underlay and acoustic board products based onplasterboard.

Good acoustic damping properties can be anticipated from products made with recycled rubber due to its

damping properties.

The raw materials price for tyre-derived rubber makes it attractive for consideration as an ingredient in wall

partitions. This was confirmed in the market survey (Section 3.3).



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3.2.3 Further prototypes: laminate floor underlay and plasterboard sandwich panelsPrototypes 2 and 3 were shown to industry partners to gauge the level of interest from a technical viewpoint. In

parallel, an economic assessment of each of these applications was carried out (see Section 3.3). Further mixes

were also developed using waste car tyre-derived rubber.

One of the concerns with the prototype samples shown in Figure 7 was the stiffness of the rubber layer, as this is

important in determining the acoustic insulation properties. In general terms, the stiffer the layer, the less soundattenuating and the more thermally insulating the layer is. For this particular project, sound attenuation was the

main interest and the prototype samples were deemed too stiff for the best attenuation in both applications. The

type of resin used in the mix is the main parameter affecting the stiffness of the prototype. Another resin (a

polyurethane resin known as Resin D) was therefore used to develop further prototype samples (see Figure 9).

The work also focused on small particle-sized materials (such as buffings) which were considered likely to be

suitable for the fabrication of thin components. These materials also have the advantage of low market price

(10 times the diameter of

the largest particle. Hence, a layer thickness of 10mm was the starting position for the prototypes.

The new prototype samples were made using a polyurethane resin (Resin D) which is activated by atmospheric

moisture. It therefore requires no heat or water addition to the mix. It is also judged to be less stiff than the

isocyanate resins. The manufacturers recommended that, for small particle sizes, 1520% (by weight) of resinshould be used. This is a higher resin content than that used for the first phase and as a result, the cost of the

resin makes up the bulk (approx. 8090%) of the raw materials cost of the resin/rubber layer. (See market

survey, Section 3.3. and Appendix A.)

The sample mixing and compaction procedure was the same as that used to manufacture the previous

prototypes. However, the samples were cured at room temperature and without the addition of water. A longer

curing period was also used compared with the previous laboratory prototype samples. The rubber used for these

samples was buffings (derived from tyre retreading). Buffings are relatively low in cost (see Section 3.3), small in

particle size and do not contain any fibre (which absorbs a large amount of resin). In addition, the small particle

size allows fairly thin components to be made. Two types of prototype were produced (Figure 9).

Both prototype samples that were developed from the buffings during the second phase of the project appeared

less stiff when handled than the samples previously developed. They were therefore considered more promising

for technical investigation as potential acoustic insulation products. The materials mixed easily and the products

were easy to mix and compact. The finished products were well bonded together when cured and appeared to

have a good level of stiffness. The fibrous structure of the buffings also provided a good particle interlock, which

is expected to provide better tensile strength. However, an economic assessment of the floor underlay recipe

showed that the use of buffings in this application was uneconomical compared with alternatives already on the

market (see Section 3.3.4). No further tests were therefore carried out on the floor underlay.

In summary, the sandwich wall panel (Prototype 6) was considered successful. A sandwich panel prototype with

17.5% resin content was successfully manufactured. An initial assessment of the cost of raw materials also

indicated that it could be economically viable and compete on price with competitor partition products. However,

the economic assessment of the materials indicated that the resin represents a major component (around 90%)

of the materials cost. It is expected that, with the development of bioresins that are not based on petrochemicals,the price of the resin component will fall to perhaps half that of the current price of petrochemical resins.



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Figure 9 Description of the second phase of prototypes developed using buffings

Picture Application Resin %

(by

weight)

Rubber

used

Other material

used

Comment


panel for

wall partition

Resin D:

17.5%

Buffings

(10mm

thick)

Plasterboard Good bonding of

tyre with

plasterboard.

Prototype appears

less stiff thanPrototype 2 good

potential

Prototype 7: Bottom and top view Laminate

floor

underlay

Resin D:

17.5%

Buffings Laminate floor Good bonding of

tyre with laminate

floor. Prototype

appears less stiff

than Prototype 3

good potential

Lafarge Plasterboard showed an interest in the plasterboard sandwich panel and the economic assessment of this

product showed that it was potentially economically viable. The plasterboard samples were therefore tested

further under this project. The results of testing conducted by Lafarge Gypsum, on prototypes similar to

Prototype 6, are given in Appendix A.

3.2.4 Tests on the tyre/resin mixesFire tests

Small-scale fire tests were carried out on two prototype samples:

Prototype 2 (tyre layer: 100mm thick)

Prototype 5 (tyre layer: 100mm thick): granulates were high-value tyre products as they contained no fibre or

steel. Tests on this prototype were carried out mainly to gain information about the behaviour of rubber underfire conditions.

The test regime was adopted from the ISO5660 Cone Calorimeter test (WCTE, 2004). A radiation level of

50kW/m2 was chosen. The test exposes one side of the sample to the irradiation (Figure 10) and monitors the

temperature build-up through the depth of the test specimen with exposure time (for samples of 100mm

thickness). In these tests the temperature build-up was monitored in two locations:1 At the interface between unexposed board and core material2 At the centre of the core material.

This test regime is currently under development at BRE and is being used to assess product performance in

preparation for full-scale fire resistance tests to EN1363. The regime does not replace full-scale fire testing but

has been shown to provide a good indication of key performance characteristics of materials and their use in

structural wall units. It also enables comparison of performance levels of different material types and



18/35

combinations. The test set-up has several advantages, including the possibility to closely observe failure

characteristics of the specimen, especially after the test has been completed.

Figure 10 Stages of small scale-fire test to the modified EN1363

The fire tests showed that whilst the outer layer (in the case of OSB) was burned (Figure 11) or degraded (in the

case of plasterboard, Figure 12), the rubber core merely charred very slowly, rather than igniting or melting (asshown on the right hand sides of both Figures 11 and 12). The temperature probe placed just at the interface

between unexposed board and core material showed that after 30 minutes of exposure to the heat source, the

temperature remained at room temperature.

Figure 11 Hole burned through OSB

4 cm

4 cm

Figure 12 Hole burned through the plasterboard, sheathing, and charred rubber core

Many applications or products have more specific test requirements than can be addressed by a simple test such

as the calorimeter test. Nevertheless, the work done so far does give an early indication that combustibility may

not be a major problem with these products containing tyre rubber. It is also recognised, however, that issues

such as the amount and nature of smoke generated are important. Further testing of prototype products would

be necessary to address these issues fully. Such tests would need to be specific to the intended application to

determine the fire resistance period of, for example, a stud partition with rubber-backed sheathing boards.Polyurethanes such as Resin D are combustible and can regenerate isocyanate fumes. However, phosphate-type

flame retardants can be added which can be very effective barriers to the propagation of flame.



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Further tests on the plasterboard wall partition samples (Prototype 6)

Further samples of Prototype 6 were prepared, using a different Resin D. The tyre layer as prepared for Prototype

6 samples was tested for:

water vapour permeability

permeability

water absorption swelling of the tyre layer with water over time.

Prototype 6 was also tested for:

stiffness (3 point bending). The test method utilises a constant span (100cm) between supports and gives the

amount of maximum deflection from the horizontal (at mid span at the time of failure) and the load required

to cause that failure.

density

impact resistance: The impact test allows materials to be categorised into duty categories of light, medium,

heavy or severe. Appendix A gives further details.

Tensile and compressive strength were not assessed as resistance to bending/deflection of the prototype was

considered more relevant to the performance of partition boards. The results of the tests are summarised in

Figures 13 and 14.

Rubber layers (10mm thickness) were manufactured at BRE with three different resins. These were sent to

Lafarge Gypsum for the manufacture of prototype panels and assessment for potential acoustic benefits. The

results from the tests conducted and the methods adopted are described in Appendix A. An overview of the

results is given in Figure 15.

Figure 13 Results of tests performed on the tyre layer of Prototype 6Test Result Comment

Water Vapour Permeability (BS EN

ISO12572:2001)

650 g/m2 /day The tyre layer is permeable, so cannot be used at a

vapour barrier.

Water Absorption 21.43%

Swelling (tested in water at 20 C

measured after 7 days) (BS EN317:1993)

1.08%

Virtually no swelling, although the water absorption

is high (probably due the presence of voids

between tyre buffings).

1 cm

Figure 14 Results of tests performed on Prototype 6



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Test Results and comments

Stiffness (adapted from EN310:2003)

Sample size: 600mm length x 50mm width x

32mm thickness

Average results (for 3 samples) for Prototype 6: Mean

deflection 12mm under a load of 258.62N

The average result (for 3 samples) for a single layer of

plasterboard: Mean deflection 17mm under a load of 68N.

1 cm

1.73mm indent on board for impact of 10Nm

Suitable for Severe duty

Impact (up to 10Nm) based on BS5234-2 1992

Part 2 and BS8200: 1985 [8, 9]

An indent caused by a

10Nm impact Average

diameter of indents =

23.3mm; depth = 1.73mm

Figure 15 Results of tests performed on prototypes manufactured by Lafarge Gypsum

Test Results and comments

Manufacture

Prototypes with three resin types, identical

thickness were developed and tested using a

method based on ISO16940*

type A : 12.5mm standard + type A resin/rubber

10mm

type B : 12.5mm standard + type B rubber/resin

10mm

type C : 12.5mm standard + type C rubber/resin

10mm

plasterboard layer

rubber/resin layer

Acoustic (damping of vibration of the board)

Acoustic performance: dynamic stiffness anddamping (tested by Lafarge Plasterboard)

All the results were encouraging and showed good results in

terms of dampingof the vibration of the board compared to

conventional products. Damping results were 4% for all

three prototypes.

* ISO16940 Glass in building Glazing and airborne sound insulation Measurement of the mechanical impedance of

laminated glass

3.2.5 Used tyre-performance-demand model



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The most successful prototype (technically and commercially) was a panel based on resin-bound rubber buffings

bonded to plasterboard. A matrix was therefore developed for the plasterboard/buffings composite sandwich

panel material. Function-demand inputs to the model (developed by the BRE team) were as shown in Figure 16.

The results of the assessment of the prototype against the matrix are given in Appendix A. Here, the performance

and cost of the composite is compared in relation to service classes for plasterboard and competitor acoustic

boards.

Figure 16 Function-demand inputs

Resin bindero Resin type

o Resin content (%)

o Resin cost

Tyre/resin layero Stiffness

o Durability (moisture resistance)

o Shear resistance

Tyre-derived rubber

o Tyre-derived material (particle

grading and shape)

o Relative density

Tyre/plasterboard composite performance

o Impact resistance

o Bending strength

o Deflection

o Interlayer bond strength

o Stiffness of rubber/resin layer

o Stiffness of plasterboard layer

o

thickness of rubber/resin layero Thickness of plasterboard layer

Possibil ities for modification of key properties of the overall composite

o Resin type

o Resin content (%)

o Tyre-derived material (particle grading and shape) as received

o Possibility to modify the tyre-derived material

o thickness of rubber/resin layer

o Thickness of plasterboard layer

o Number of layers (2 or 3)

o Options for onsite mixing versus delivery to manufacturer as a roll

3.2.6 Summary of the prototype developmentThe plasterboard sandwich panel with a buffing/ resin layer in the centre (10mm thick), using Resin D was

successfully developed and showed:

Good acoustic properties (vibration damping)

Improved stiffness properties compared to a single plasterboard layer

Impact resistance equivalent to that of a panel suitable for severe duty

The rubber layer had a similar density (kg/m2) to that of a sheet of plasterboard (12mm thickness).

The technical properties of the panel were, therefore, so far very promising. A comparison of the prototype

properties with those of other boards (where available), is given in Appendix A.

With the prototypes manufactured at BRE and tested at Lafarge Gypsum, all the results were encouraging and

showed good results in terms of dampingof the vibration of the board compared to conventional products.Results obtained in the project are compared with data for other plasterboard and acoustic board products in

Appendix A.

3.3 Market survey

One issue raised by the project partners was the need to ensure that the products developed during the projectwere economically competitive with comparable products. A detailed market review was therefore conducted on

the two products identified (acoustic wall board and acoustic underlay).



22/35

3.3.1 Market drivers for the use of tyres in compositesThe main general market drivers for processed tyre materials are summarised below (Figure 17). (+) indicates

drivers that are likely to increase the supply of materials and lead to lower raw materials prices; (-) indicates

drivers that are likely to compete with construction applications for low-cost waste tyre material, reducing supply

and increasing cost. Several manufacturers were contacted and an internet search was carried out to find out the

value of materials derived from waste tyres. Results are given in Figure 18.

Figure 17 Effects of the drivers influencing the market for recycled tyresDriver influencing market for processed tyre materials Effect of driver

+Whole and chopped tyres banned from Landfill (July 2006)

-Competition for restricted supplies of raw materials could act against new entrants tomarkets (Materials Recycling World, Issue 17)

-Competition for coarse shredded rubber with other high-value end uses (e.g. equestriansurfaces), and with cement kiln fuels (Materials Recycling World, issue 17)

+Economies of scale as processing capacity increases

+Current markets are seasonal (equestrian surfaces, lawn treatment). There may therefore bescope for less seasonal products such as construction products

+WRAP drive to stimulate remould tyre market is likely to increase the supply of buffings

Figure 18Value of size-reduced materials derived from waste tyres (approx. figures from manufacturers, 2006)

Material Approx

price

per

tonne

Corresponds

to PAS107

category

code

Description Application

a) Coarse shreds

(3050 mm)

5 ex

works

RS Large tyre shreds with steel and

fibre present

Civil engineering

b) Shreds (5 mm

to 25 mm)

60 CC Flat thin particles; textile fibre

present

Equestrian

surfaces/paths

Coarse

(

>5mm)

c) Small

shreds/granuleswith fibre

(10 mm single

size)

100 CC Flat thin particles; textile fibre

present

Equestrian

surfaces/paths

d) Rubber

granules

(25 mm)

100

120

G Virtually single size shred

material. Minimal textile fibres

Playground

surfacings/turf

reinforcement

e) Tyre fibre 5 - (Rayon/nylon with some rubber) None currently

f) Buffings 4050 - Fibre-like rubber particles up to

3mm long, minimal textile fibre

content, some finer material

None currentlyFine

(

tyr003 04 21 aug 07 final version

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