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INTRODUCTION

This booklet is a quick reference guide to the capabilities of Dyman Foams range of Industrial Foam Products. It is designed to expand upon the standard specification booklet and provide more information on product production and end uses.

The Technical Department is continually upgrading the performance specifications for all our products. Where details of performance or fire tests are required they can be obtained upon request.

All the products listed in this booklet are standard stock lines readily available for distribution through all our offices Australia wide. Please read the document in conjunction with a foam catalogue. If you require further information on a customer enquiry, in the first instance ask the assistance of Chris Houghton, and if you still need help, the Technical Department or the Market Development Manager will be happy to assist.  

TYPES OF FLEXIBLE POLYURETHANE FOAM

Flexible polyurethane foams are open cell foams expanded mainly by carbon dioxide produced by the reaction of water and isocyanate and arc considered to be the most important class of polyurethanes. They are used as upholstery in furniture, as carpet underlay, in bedding and in vehicle manufacture and as energy absorbing padding for the protection of goods and people.

The main types of flexible foam produced by Dyman Foams may be divided into polyester and polyether based slabstock foam. There are also a number of specialised foam grades manufactured which are utilised in a wide range of applications.

The terms "ester" and "ether" indicate that the foams employ a polyol with a particular combination of atoms which give the product distinct characteristics.

Flexible polyurethane slabstock is made in three main conventional types;

a) foams based on polyester polyols

b) foams based on conventional polyether polyols

c) high resilience foams based on modified polyether polyols.

The properties of the polyester based, polyether based and high resilience types of flexible foams differ widely because of their difference in chemical structures. The stiffer polyester based foams having more polar carbonyl group hydrogen bonded chains than those. of polyether. chains, have a greater resistance to both tensile and compression loads and much lower resilience than polyether based foam. The more random chemical structure of high resilience .. foams, combined with their more irregular physical form, yields the highest resilience together with lower resistance to deformation.

Both types of polyether based foams are more resistant to hydrolysis than the polyester based foams and this property is important in hot, humid conditions or in the presence of acids or alkalies where the service life of polyether foams may be in the order of ten times than those based on polyester.

Polyesters have significantly better resistance to oxidation and to many solvents, the latter being the main reason for their continuing use in textile and clothing applications

Just over 90% of all flexible foam slabstock produced by Dyman Foams Group is based on polyether polyols, with 81% of this figure being conventional flexible foam. The remainder includes polyester, high resilience foams, super soft foams, high load bearing and specialised foams, including sound absorbing and reticulated foams.  

TERMS FOR FOAM PROCESS CONTROL

Flexible foam quality is checked by measuring the physical properties of the foam, using standardised methods of measurement on standard test samples cut from the items to be checked. Our laboratory checks the performance of each and every production run to ensure that the product meets pre-determined standards of quality and grade specifications.

The test results are evaluated against specified limiting values, which experience has shown to yield satisfactory service performance.

Many standard tests for flexible polyurethane foams have been devised by various national standard organisations such as the BSI in the UK, DIN in Germany, ASTM in USA and NF in France.

In Australia most testing is done in accordance with the Standards Association of Australia using Australian Standard 2282 (AS2282) - Method for Testing Flexible Cellular Polyurethane.

The following brief descriptions of the test methods for measuring the physical properties are intended only to outline the principle of the methods.

DENSITY

This is simply a measure of the mass per unit volume and expressed in kg/m3.

Density, (as mentioned elsewhere) is not necessarily related to hardness as it is possible to produce a super soft flexible foam, a semi-rigid foam and a rigid foam, all of the same density.

The density of a flexible foam must be regarded as a guide to its durability (or quality), particularly in regard to the rate and extent of its hardness and height loss in actual service conditions.

High density foams are more expensive as they require more raw material for a given volume of foam.

HARDNESS

In the majority of situations the choice of foam for a given application is primarily decided on hardness, which in turn is related to consumer preference.

All foam runs are tested for load bearing (hardness) and the grading of foam is partly based on this property.

In the AS2282 - "Method for Determining the Indentation Force on Deflection", a flat circular indentor of 200mm diameter is mounted by a ball joint and driven at a constant specified vertical rate to produce the specified indentation of the sample.

The foam sample used is of a standard thickness (50mm) and is 380mm square.

The sample is reflexed twice to 75% indentation. Then after testing the indentation force is measured at 25%, 40%, 65% and 25% indentation with a 60 second dwell at each point.

The IFD at 40% deflection is used (in conjunction with the density of the foam), to classify the foam because it relates to the level which most foams are normally compressed when used for cushioning.

Hardness loss is a characteristic of all foams and is particularly evident in low density foams. The hardness loss can be around 10% for heavy duty foams to 40-50% for light duty foams.

Also the amount of hardness loss is dependent on the application, for example, a chair back is not subjected to as much compressive stress as the chair cushion and as a result it will not soften to the same extent.

INDENTATION FACTOR

Also known as the Sag factor, comfort factor, is a ratio of the 25% and 65% (65%/25%) readings. The higher ratios indicate a wider difference in the two readings and indicate "surface softness and deep down firmness".

COMPRESSION SET

Compression set is a measure of the permanent deformation resulting from a fixed compression for a given time period.

It is expressed as the percentage loss of the foam. Sample's original thickness and is an attempt to provide a measure of the height loss under service conditions.

TENSILE STRENGTH AND ELONGATION AT BREAK

The test provides a measure of the strength characteristics of a foam at breaking point. The tensile strength and elongation properties of a foam must be adequate to allow safe handling in manufacture and in end-use.

The method utilises a die cut dumb-hell shaped foam specimen which is symmetrically clamped by both ends on a testing machine. The machine stretches the specimen and the load and elongation are recorded on rupture.

TENSILE STRENGTH

Is the maximum force required to break the test piece, divided by its original cross sectional area. It is expressed in kPa.  

ELONGATION

The change in gauge length of the test piece at the time of break, expressed as a PERCENTAGE of its original gauge length.

TEAR RESISTANCE

The resistance to tear is determined as the force required to propagate a tear in a pre-cut test piece. It is measured by the trouser tear method and is expressed in N /m.

RESILIENCE

Resilience is a measure of the springiness of a foam. The more resilient a foam, the more comfortable it is for seating. Resilience is measured by dropping a steel ball onto a foam sample and measuring the rebound.

CELL COUNT

The cell size or cell count is an important property as the physical properties of a flexible foam may vary with changes in cell count. Cell counts are determined on a cut, plain foam surface using a counting glass.

The cell counts of reticulated foam are determined by measuring the pressure drop of an air flow through the foam.

POROSITY

In normal foam, a thin membrane or skin interconnects many of the cells. These restrict the passage of air and change performance characteristics depending on end use. For example, the cell structure can be opened up to reduce closed cells and give better resilience performance. The porosity is normally measured by recording the volume of air which can be passed through the foam.  

AS2281 CLASSIFICATION

The Australian Standard AS2281-1979 11 Flexible Cellular Polyurethane for Seat Cushioning and Bedding 11 sets out the requirements (or recommendations) for the selection of a flexible cellular polyurethane foam for use in seat cushioning, bedding and similar applications on the basis of foam density and hardness.

In this specification:

Conventional foams are designated Type A
High resilience foams are designated Type B
Reconstituted foams are designated Type C

Additionally

Type A foams (conventional resilience foams) are sub classified as Normal (N) or Heavy Duty (H) on the basis of density. Type B and Type C foams are classified as Class H.

The Type A, Type B and Type C foams are then graded into 13 grades ranging from 00 (softest) to 11 (firm) according to their hardness.

GRADES AND DENSITIES OF FLEXIBLE CELLULAR POLYURETHANE

 

 

Minimum Density, kg/m3

Grade

40%

Type A

Type B

Type C

Indentation Force on Deflection

Class N

Class H

Class H

Class H

00

25 - 45

15

22

22

40

0

45 - 65

16

25

25

40

1

60 - 90

17

28

28

45

2

85 - 115

20

30

30

45

3

105 - 145

23

35

35

50

4

145 - 180

27

35

35

50

5

170 - 220

31

35

35

55

6

210 - 270

31

35

35

55

7

260 - 330

31

35

35

60

8

320 - 400

31

35

35

65

9

380 - 480

31

35

35

70

10

460 - 580

31

35

35

75

11

560 - 720

31

35

35

80



(Other properties such as tensile strength, elongation at break, compression set and other important performance. related characteristics are usually specified at a level which can be met by several grades of foam.)

The AS2281 specification lists recommendations for the selection of the most suitable foam grade and thickness for a nominated cushioning application.

INDUSTRIAL FOAM GRADING SYSTEM

Dyman Foams and their associate companies offer in excess of 50 grades of various foam types, many of which do not comply with the requirements for AS2281 classification. To enable our customers to specify and to select the correct foam type and grade for their particular application, we have, in conjunction with other foam manufacturers, adopted an industrial grading or a standard system of description for various foam types.

Flexible polyether types are graded on the basis of density and hardness.

A coding system is used to denote other foam types and intended applications.  

Key to Coding

Prefixes

L - Conventional polyether foam for light duty applications - below the minimum requirements of AS2281-1979.

N - Conventional polyether foam for normal duty applications.

H - Conventional polyether foam for heavy duty applications.

HR - High resilience foam.

C - Reconstituted foam.

F - Filled foam.

U - Carpet underlay.

SS - Sea sponge.

S - Polyester-urethane foam.

SF - Filled polyester urethane foam.

Suffixes

FL - Flame laminable polyether foam.

CM - Combustion modified foams.

D - Densified foam felts.

R - Reticulated foam.

     

 

 

 FOAM RANGES

CONVENTIONAL FLEXIBLE FOAMS

These arc conventional resilience polyether flexible foams and are made with a density range of 15-40 kg/m3. They are produced in a continuous slab which is cut into smaller manageable blocks and then converted to various shapes required for upholstery and other applications. Furniture components are frequently cut separately and then fabricated together.

Grading

Flexible polyether polyurethane foams are graded by utilising their density (kg/m3), Indentation Force on Deflection (50mm IFD 40% ), value expressed in Newton (N), because these are the characteristics which broadly define their cost and determine whether they are likely to be satisfactory in service conditions.

Conventional flexible foams are graded into three main types:

Light Duty Polyether (L)
Normal Duty Polyether (N)
Heavy Duty Polyether (H)

LIGHT DUTY POLYETHER (L)

Grade

Colour

Core

5Omm

 

 

 

Density

IFD

Indentation

Resilience

Typical Uses

kg/m

40%N

Factor

%

 

L15-100S

White

15.5-16.5

85-115

1.75

50

Utility grade

 

 

 

 

 

 

 

L19-130S

Mid

19-20

115-145

1.75

40

Overlays, bed settees

 

grey

 

 

 

 

 

L24-160S

Pink

24-25

145-175

1.75

40

General upholstery

 

 

 

 

 

 

 

L27-200

Pale

27.5-28.5

170-210

1.75

45

Dining chairs, auto uses

 

green

 

 

 

 

 

 

These foams are made in densities varying from 13-27 kg/m3 - and an indentation factor 1.75, together with a resilience figure of 40-50%. These foams have a fairly light fresh feel. They do not meet the requirements for AS2281-1979 classification and are intended for light duty and specialised applications.

(Please note a low density foam of a specific hardness will allow the foam component to perform a particular function for a relatively short period only. High density foams must be considered when the products long term durability is to be considered.)

 

NORMAL DUTY POLYETHFR (N)

 

 

Class

Core

5Omm

Indentation

Resilience

 

Grade

Colour

AS2281

Density

IFD

Factor

%

Typical Uses

 

 

-1979

kg/m3

40%N

 

 

 

N 15-60S

White

N

15-16

50-70

1.75

40

Soft pillows,

 

 

 

 

 

 

 

quilting

 

 

 

 

 

 

 

 

N20-100S

White

N

20-21

85-115

1.75

40

Back

 

 

 

 

 

 

cushioning,

 

 

 

 

 

 

 

quilting

 

 

 

 

 

 

 

 

N23-l30S

Pale

N

23-24

110-150

1.75

40

General purpose

 

grey

 

 

 

 

 

upholstery

 

 

 

 

 

 

 

 

N29-400S

Dark

N

29-30

350-450

1.85

20

High load bearing,

 

grey

 

 

 

 

 

Carpet underlay

 

 

 

 

 

 

 

 

H31-320S

Cream

N

31-32

280-350

1.75

20

High load bearing,

 

 

 

 

 

 

speciality foam



Comply with the requirements for an AS2281-1979 classification as Type A Class N foams. They are available with a density range of 15-31 kg/m3 and a resilience figure of 40-55%.

PREMIUM RANGE (5 YEAR GUARANTEE)

 

 

Class

Core

5Omm

Indentation

Resilience

 

Grade

Colour

AS2281

Density

IFD

Factor

%

Typical Uses

 

 

-1979

kg/m3

40%N

 

 

 

28-80

Yellow

H

27-28

85-115

1.75

40

Back

 

 

 

 

 

 

 

cushioning

 

 

 

 

 

 

 

 

H30-100S

Yellow

H

30-31

85-115

1.85

50

Seat cushions

 

 

 

 

 

 

 

 

H30-130S

White

H

30-31

110-150

1.75

40

Seat cushions

 

 

 

 

 

 

mattresses

 

PREMIUM RANGF (10 YEAR GUARANTEE)

 

 

Minimum

Hardness

 

Grade

Colour

Density

Range 5Omm

Typical Uses

 

 

kg/m3

IFD 40%N

 

35-l10

Purple

35

100+-15

General purpose seating

 

 

 

 

35-130S

Light

35

130+-20

General purpose upholstery

 

Blue

 

 

 

 

 

 

35-200S

Dark

35

200+-30

Transport seating

 

Blue

 

 

 

   

CM5 (10 YEAR GUARANTEE)

 

 

Minimum

Hardness

 

Grade

Colour

Density

Range 5Omm

Typical Uses

 

 

kg/m3

IFD 40%N

 

HR36-100 CM5

Bright

36

100+-15

Premium mattress and cushioning

 

Green

   

 

 

 

 

HR36-130 CM5

Bright

36

130+-15

Premium cushioning

 

yellow

 

 


The Platinum CM Range is a system using high resilience polyol and a solid melamine fill for combustion modification. There are currently no AS2281-1979 classifications for combustion modified filled HR foams. Under AS2281-1979 HR foams need a resilience performance of over 60% as well as other test criteria to qualify. Most Platinum CM grades still pass this test but melamine filling does reduce the performance in some grades. Here we have called Platinum CM a CMHR foam because it is using a combustion modified HR technology where a new standard will eventually apply.

Conventional Polyester-Urethane Foams

Polyester foam was the first type of polyurethane foam to be used in upholstery and transport seating but it now has been almost replaced in these applications by the cheaper and more resilient polyether foams. Production of polyester foams continues for specialised applications, textile laminating, packaging, sound absorption and various other technical applications. They are also used in the padding and insulating of clothes, eg. shoulder pads.

Polyester foams are characterised by their high hardness and tensile strengths compared to polyether foams and are made in a wide range of cell counts and densities which depend on the application requirements.

Grading

Polyester foams, unlike polyethers, are not graded by the density and hardness but by their density and cell count. This is because the main uses are in acoustics, filtration, or as an absorption medium where performance is dependent upon the cell count.    

FOAM APPLICATIONS

Foam has many applications

General

Air Filters

Absorbs Sound

Anti Surge Mitigator

Carpet Underlay

Cushions, seats, hacks, overlays, head rests etc .

Liquid Filters

Mattresses      Single
                     Double
                     Queen
                     Cot
                     Bassinette

Pillows

Reservoirs

Seals

Sponges

Wicks

Specialty

Numerous applications.  

Polyester foam is typically used for -

Flame lamination to fabric for apparel and is also used to laminate light fabrics together to give bulk to the final fabric

Gaskets and seals

Toys - soft varieties

Filter material - Reticulated foam

Decorative seat padding in conjunction with either vinyl or synthetic yarn fabrics

Artificial flowers

Acoustic facings for loudspeaker enclosures and industrial noise control

Packaging

Polyether foam is by far the most widely used foam in Australia. Examples of its versatility of application are -

Seat and squab padding for furniture and automotive seating

Mattresses - domestic and recreational use

Overlay for innerspring mattresses

Adhesive laminated to fabric for such applications as soft feel toilet bags, or sewn decorative padding for furniture or automotive seating

Inner soles for footwear

Foam blankets

Pillows and scatter cushions

Carpet underlay

Acoustic applications

Protective padding and packaging

Moulded complete lounge furniture

Profile cut and fabricated lounge furniture

Moulded automotive seating

Fabricated automotive seating

Book cover padding in stationery industry

Bath sponges

Public auditorium seating

Public transport seating

Reconstituted foam is manufactured by crumbing either polyether or polyester foam into particular size particles. The particles are then bonded to form a dense foam. This product finds particular application in :

Seating, where a very firm seat is required

Reinforcement for fabricated seat padding in domestic and automotive applications

Carpet underlay

Packaging

Sporting mats

This product is currently not offered by Dymanfoams.

Lamination

Polyurethane foams can be bonded to a variety of materials either by the use of adhesives or the "flame lamination" technique. The foam is peeled into foils of say 1.5 to 6mm thick for use in clothing, car trim and footwear etc. The density required for a given laminating application is a compromise between durability and price. For textile laminates which are subject to high service stress, foams of density 26 kg/m3. higher are used. Lower densities are used for laminates which undergo less service stress.

The appearance of laminating grade foams is much more important than it is for upholstery foams. The control of cell size, porosity and uniformity and absence of short holes is critical to laminating processes, especially name lamination.

In the flame lamination process, the surface of the foam is heated usually by a gas name until the surface layer fuses and becomes soft and tacky. It is then immediately bonded to the fabric.

Grade S21/70 and Grade S26/80 (formerly EF200 and EF280 respectively) are the recommended polyester laminating grades but the polyether grade N26-140FL is also intended for name laminating. However, polyesters are generally selected because of the resistance to damage whilst being cleaned with solvents and because the laminating parameters are not as critical.

In adhesive bonding the adhesive is applied to the surface of the foam to bond the fabric to the foam.  

Foam linings for textiles helps to dimensionally stabilise the textile and provide a high insulating quality that allows the laminate to breathe. It also provides excellent crease resisting properties.

Various plastics, paper, metallic foils can be bonded to polyurethane foam for application in the footwear, automotive and application fields.

Packaging

Flexible polyurethane foam is ideal for packaging applications because it exhibits the following:

a) An outstanding shock absorbency over a wide stress range

b) Good insulating characteristics

c) Unaffected by heat and cold (-400C to 1200C)

d) Resistant to mildew, rot and vermin

e) It can be easily shaped and fabricated and is available in thin sheets

f) Offers advantages of maximum protection with a minimum of weight and volume

Both polyether and polyester types can be utilised depending on the end use but the advantage of using polyester foams in padding and packaging applications lies in its initial high resistance to compression and its high energy absorption.

Thin sheets of polyester foam (say 1.5mm) can be used as a protective wrapping for packaging fragile items such as glassware and china.

Acoustic

Any structure that is open and which will allow sound to enter and to vibrate internal cells or fibres will absorb acoustical energy. As the sound wave enters the structure the pressure pulse - of the acoustical wave causes the cell to. vibrate. The resultant mechanical movement of the strands dissipate the energy which is released as heat (an infinitesimal increase in temperature).

(The capacity of a material to absorb sound rather than reflect it is expressed as the Sound Absorption Coefficient). For example, if a material absorbs 50% of incident sound energy at a certain frequency, then it has a sound absorption coefficient at 0.50 at that frequency.)

Absorption materials include fibrous glass, rockwall carpets, drapes, furnishings even people . and clothing. The one unifying factor is the necessity to a1low the acoustical wave to penetrate to the interior of the material where it can interact with the cellular structure.

All flexible cellular foams arc absorption materials, but the acoustical properties of these will vary due to the physical characteristics of the foam itself. Some of these major variables include cell structure, thickness, permeability and surface treatment.

Permeability is the ability to allow the passage or the air and can be measured as the pressure drop exhibited by a gas moving through the foam. It generally increases with an increase in the cell size. However, permeability is also affected by the surface nature of the cell and is greatly influenced by the number of closed cells. As a result of the way they are manufactured non - reticulated foam normally. have a thin membrane or skin interconnecting many of the cells. These closed cells restrict the passage of the air and decrease the permeability of the foam.

Although this characteristic would seem ideal for blocking sound TOO MANY closed cells will prevent the acoustical energy from entering the foam where it can be dissipated by the ribs that make up the cell structure.

It should be noted that as material thickness increases, reticulated foams have increased absorption characteristics and in thicknesses of 50mm or greater are better than non-reticulated foam.

From a practical or engineering point of view, perhaps the most important attribute of foam is that it can be manufactured consistently with a specific cell size structure and cell size. This allows the material to be selected either to transmit or attenuate sound.

Foam can be cut to conform to specific shapes and is uniform m thickness and surface characteristics which leads to reproducible acoustic properties.

Additionally, foam does not shred or produce fibrous dust into the environment or produce debris that could interfere with the operation of electrical contacts.

The manufacturing techniques used at Dyman Foams are controlled so that the variables such as permeability, cell size and thickness that affect the absorption properties at different frequencies ensure that the acoustic foam range have good predictable acoustic characteristics.

This is demonstrated by comparing the attached statistical absorption coefficient charts.

Figure 1 shows an actual acoustical absorption of Dyman Foams grade S32/70 CM (EF570) - a combustion modified non-reticulated foam. This sample is on the "fine" side of the manufacturing specification.

Figure 11 - same foam type S32/70 CM but on the "coarse" side of the manufacturing specification.

ACOUSTIC FOAMS

Product

Function

Application

S28/70 CM

Sound Absorber

General use - UL94 Classification HF1

 

These base foams are modified to

a) Obtain a desired acoustical property

b) Give the foam protection against a particular environment

c) Give some decorative effect.

Solid Backing

Although foam requires certain acoustical properties for optimum absorption efficiency, the most critical requirement is the need for a solid impermeable backing. Without such a backing, sound passes through with only moderate attenuation. Experience has shown that unbacked foam wrapped around a pipe, or draped over machinery, is not effective in dissipating noise.

However, a solid backing requires .the. sound to enter the foam, reflect off the backing and come out the same way it went in. The attenuation provided by this reflection technique is more than double that of an equal thickness of unbacked foam. Although the attenuation process provided by the backing is not completely understood, it is believed that the incoming and. outgoing . sound signals may he out of phase and thus, may tend to cancel each other.

Equipment housings (if they are heavy enough) can act as solid hacking for foam linings and in such applications for foam, reduces the reverberation build up of noise inside the enclosure.

However, openings in an enclosure tend to minimise the silencing effect of the foam because any sound that "sees" the opening will escape. Such openings or holes in an enclosure are far more harmful than the thinners of the walls in terms of letting sound escape. Thus it does not make sense to specify the walls of an acoustic enclosure to be constructed of heavy tight materials (ic. timber, masonry, steel) if there are a number of openings through which the sound can pass through. In such applications baffles can he used to prevent the sound from having a clean path out of the enclosure.

Protective Facings

Conversely as much as a solid hacking attenuates sound, a protective face or an acoustic foam may effect the absorption efficiency, particularly at medium and high frequencies (eg. vinyl, mylar).

Such facings reduce the permeability of the foam and restrict the passage of acoustical energy into the foam cells

One of the many techniques used to give foam protective properties. that laminated films have, eg. scuff resistance, is to heat emboss the foam surface.. This compacts the surface pores to produce a tough, easily cleaned surface that does not markedly degrade acoustical properties.

Other techniques include flame bonding a protective facing to the foam. This technique involves the melting of the foam surface which then acts as its own adhesive to hold the facing. Unlike adhesive boding (when an excess of adhesive is used) the flame bonding does not form a barrier between the foam and protective facing which if it has a sufficient number of perforations, will allow the acoustical energy to enter the foam and be absorbed.

Passing Sound

The permeability of foam also makes it a good transmission medium for sound. Basically, if foam is used as an acoustically "clear" material, all that the sound should see are holes and cell ribs of the foam structure. The more holes, the more early the sound passes through. Therefore the requirement for sound transparency is for large cells.

The most suitable foams for such applications arc the open cell reticulated types which produce little off-axis deflections of the sound waves.

These deflections which produce major distortions of the sound and attenuate highs (above 500 HZ), are most prominent in open cell non-reticulated foams because the membranes between the cells cause the sound waves to bounce and scatter away from the main transmission axis.

Speaker and microphone cores arc major applications for acoustically transparent foams - the foam not only provides acoustic transparency, but additionally protects the components from physical damage, keeps out dust and with microphones acts as a wind sock. Common foam thickness for acoustically transparent foams range from 6mm to 50mm. The thicker foams are to provide distinctive sculptural effects and also to hide components such as speaker cores etc.

For such uses the foam normally has 30 cells per 25mm.

Larger cell sizes would not be effective in hiding the speaker shadow.

Thermal Insulation

Flexible polyurethane foam has good thermal insulating characteristics. The thermal conductivity factor "K" is of the order of 0.033 W/mK at densities around 30 kg/m3. This value is dependent on the permeability of the foam. (The lower the value of the K factor, the better the insulation properties.) The 11exible foam (both polyester and polyether) should be scaled to prevent moisture penetration as moisture will reduce the thermal insulation properties.

Applications include gap filling, vibration protection and window sealings.

Medical

Flexible polyurethane foam does not absorb x-rays and is an ideal support material for body parts during x-ray procedures.

Urethane foams arc also used as elastic bandages which utilise the self-ventilating property of the product, although contact with open wounds should be avoided.  

INDUSTRY BACKGROUND

The history of polyurethane foam goes back to 1848 when the basic urethane reaction was reported.

It involved a reaction between an isocyanate and a hydroxy compound. The significance of this discovery was confined to laboratory reactions for the next ninety years.

The next historical landmark occurred in 1937, when Dr Otto Bayer and co-workers in Germany discovered the polymerisation reaction for a family of organic chemical compounds known today as polyurethanes. The objective at that time, was to develop a polyester based urethane to compete with nylon.

The advent of World War II, and the .subsequent shortages of rubber in Germany, hastened the development of urethane materials in such applications of fibres, adhesives, surface coatings, elastomers and rigid foams. This technology became generally known at the end of the war and stimulated development in the United States, Britain and elsewhere.

In 1952, Bayer laboratories developed flexible polyurethane, based on the principle of the 1937 discovery.

In 1953 the preparation of polyurethane foam in USA was announced.

The unique reaction of polyurethane materials required the development of previously unavailable equipment and techniques. Several companies entered this new field and the commercial production of this new product began.

Initially, all of the work in flexible and rigid foam was based on the reaction of a polyester compound and an diisocyanate. Thus the first urethane foams were of polyester type.

Several shortcomings quickly came to light. These foams did not have the most desirable comfort characteristics and also tended to deteriorate in a humid environment. Furthermore, they were relatively expensive to produce.

It was not until 1957, with the introduction of urethane grade polyether polyols, that the true potential of the 11exible polyurethane industry was realised. Not only had the polyether urethane a cost advantage over the polyester type, but they offered far superior physical properties along with better cushioning characteristics.  

WHAT IS SO DIFFERENT ABOUT POLYURETHANE FOAM?

The outstanding characteristic of polyurethane foam is its versatility. The devised end-use properties can he built into the urethane foam. This means that it is possible to produce a high resilience foam for comfort cushioning and a low resiliency foam that is dead enough to absorb impact without bouncing the shock back to an object. Rigid urethane foams as hard as wood, can also he made for construction and insulation applications. Thin walled refrigerators and freezers are insulated with urethane foam.

HOW IS URETHANE FOAM MADE?

Making polyurethane foam can be compared to making a cake without an oven. The ingredients - polyol, diisocyanate, catalysts and other components are mixed as they are poured from a mixing head under precise' automatic control, into a baking pan. which consists of a paper lined conveyor system (continuous mould).

The reaction begin immediately, generating its own heat and releasing carbon dioxide which bubble up and causes the "cake" (urethane foam) to rise. By changing the chemical ingredients and processing conditions, foams of different cell structures, density, hardness and other devised properties can be obtained.

The chemicals include a polyol (polyether or polyester) and TDI (Toluene. Diisocyanate) which interact to form the urethane polymer; water which mixes with the TDI to generate the gas that inflates the foam; catalysts which control the reaction rate; a stabiliser which helps the foam set in the desired shape. Other additions which can be added include pigments, fire retardants, sanitising agents etc.

These chemicals are stored in tanks and pumped to the foam machines through pipewort, hoses, exchangers and control devices.

There are two types of foaming machines in use by Dyman/Joyce Group. In the machines sited at Sydney, Brisbane and Adelaide, the blended chemicals are dispensed from a mixing head onto a moving paper-lined conveyor set-up on which it expands and sets. These machines originally produced conventional crown topped continuous blocks of foam that were shaped like loaves of bread up to two metres wide and almost one metre high.

However, several years ago, the machines were fitted with the Planiblock Square Block System which allows for the production of foam blocks with flat tops which do not require the wasteful trimming of the rounded top block. The Planiblock system uses an additional top paper which is applied just beyond the point of mix lay down. An arrangement of platens (skis) with adjustable counter balances, applies just sufficient pressure on the rising foam to prevent the formation of the crown top with the minimum effect on foam density.  

The Maxfoam machine, sited at Melbourne and a smaller type machine in Perth, make a rectangular foam block of very uniform density. The Maxfoam machine and the Perth machine are different to the other machine types in the Group, in that the foam mixture feeds into the bottom of a trough. The foam mixture begins foaming up ..... covered inclined conveyor. Then as the rising foam moves out, the bottom paper drops and the foam expands downwards instead of rising. This accounts for the flat top on the bun and its uniform density.

Polyester polyurethane flexible foams are produced at Liverpool only and are made in the round top configuration.

Both machine types require about one and a half hours or more to set-up before even one block of foam can be produced. When the machine is operating, it dispenses hundreds of dollars worth of chemicals per minute, so mistakes are costly. Additionally, the starting and finishing block of each run are usually discarded because they are not homogeneous, the correct shape etc.

Because we make foam in a variety of grades, cell sizes and colours to meet our customer requirements, orders and foam machine times must be scheduled with an emphasis approaching maximum efficiency. Obviously the most efficient set-up would be one in which the foam machines would foam all day on one set-up, producing only one grade of foam.  

   

The Maxfoam/Varimax System for Flat-topped Blocks

   

 

The Planiblock/Hennecke System for Flat-topped Blocks

 FOAM BLOCK HANDLING

Two separate areas are used for foam block storage.


a) Fresh Block Curing Area

This area usually has reasonable separation from other buildings and is used to store freshly made blocks. The heat of reaction reaches its maximum about two hours after manufacture. The blocks are usually left in this area for 24 hours-.

b) Long Term Storage

This area is used for long term storage of blocks until needed for further conversion or delivery.  

FOAM BLOCK CONVERSION

The foam blocks are converted into intermediates and finished products such as smaller blocks, sheets, for fabrication components, rolls etc. by utilising one or more of the following:

Peeling

Splitting

Profile Cutting

Fabricating

Reticulating

Impregnating

Crumbing

Rebonding

Dyman Foams Pty Ltd 105 Robinson Road

GEEBUNG Q 4034

Phone: (07) 3865 1400 Fax: (07) 3865 1757