Technical Details

EXPANDED POLYSTYRENE

Description

Literally translated, polystyrene is “polymerised styrene”.  The expandable form (known as EPS) is initially produced as small beads containing a blowing agent.  The beads expand when treated with steam, forming a lightweight “prefoam” of the required density.

These prefoamed beads are then processed in a mould to form large blocks that are then cut into sheets or other shapes.  Alternatively, for high volume products, the beads are moulded into their final product form in individual moulds.

Typical Applications

Cold storage insulation: floors, walls, and ceilings.

Lagging: pipes, tanks, vessels, valves and ductwork insulation.

Industrial and domestic insulation: floors, walls, ceilings, and roofs.

Building and construction: concrete fill and for expansion joints

Insulating panels and door manufacture: core-insulating material

Packaging: for maintaining the temperature of perishables or the protection of fragile goods

 

Properties

Chemical Resistance

Resistant to: brine, fresh water, weak mineral acids, strong mineral acids ( except concentrated nitric), weak alkalis, strong alkalis, most vegetable oils.

Non resistant to: mineral oils, chlorinated hydrocarbons, petrol, benzene, esters and ketones

 

Burning Characteristics

EPS is a combustible material.  The amount of heat liberated by EPS undergoing combustion is very small and if this is dissipated then sustained ignition is unlikely.  The “FR” grades are treated with a fire retardant, which causes the material to shrink away from a source of ignition without burning if exposed for a short period, but burns if kept in contact with the flame for a longer period.

 

Flame retardant Grade (FR)

Flame retardant polystyrene (FR Grade) is available in all densities.  Surface fire index results according to SABS 0177 part III yield the following results:

Spread of flame index            4.4

Heat contribution index          0.9

Smoke emission index            9.9

Surface fire index                   4.7  Class 5

 

Characteristic Properties of EPS

Property Unit Test Method XG (RD)* 16DV (SD)* 24DV (HD)* 32DV (EXD)*
Foamed Density Kg/m 12+ 14-18 22-26 30-34
Compression Stress kPa BS 4370 55 70 min 110 min 150 min
Shear strength KPa BS 4370 115 140 min 170 min 210 min
Flexural Strength KPa Din 53423 160 – 230 320 – 400 400 – 500
Tensile Strength KPa Din 53571 170 – 250 270 – 320 320 – 400
Thermal Conductivity W/m.k BS 4370 0.041 0.038 max 0.038 max 0.033 max
Water absorption: 7 days test period Vol. % Din 53428 1.5 max 0.7 max 0.6 max
Thermal coefficient of linear expansion M/k 6.5X10-5 6.5X10-5 6.5X10-5 6.5X10-5
Ignition Temperature C 230 230 230 230

*Characteristics according to BS 3837/1997

RD = Restricted Duty

SD = Standard Duty

HD = High Duty

EXD = Extra High Duty

LAMINATED PANEL SYSTEM

Isopanel Panels

Isopanel stressed skin panels consist of two selected skins permanently bonded, with a heat-polymerising adhesive, to a core of thermally efficient material.  Thickness of the skin varies according to requirements and can be made from various materials such as Chromadek, Textradek, galvanised sheet metal or aluminium.

Standard Panels

The standard panel consists of a 16 kg/m3 fire retardant grade expanded polystyrene core sandwiched between two 0.55mm zinc coated, cold-reduced steel skins with an epoxy ‘no wax’ coat finished with a s silicone polyester paint (Chromadek).

Core Materials

Insulation thickness required in any particular situation depends on the value assigned to what may be called a ‘reasonable allowable heat flow’.  Experience has shown that a figure between 8 and 10 watts/m2 is acceptable

The calculation is thus:

D = lx (delta) t/Q

Where

D         = thickness of insulation (m)

l          = Lambda value of insulation (W/mC)

(Delta) = difference between internal and external face temperatures

Q         = heat flow (8 to 10 W/m2)

 

The Lambda value for our standard 16 kg/m3 density panels = 0.038 W/mC

The following table using our standard panel can serve as a guideline for choosing the correct thickness of insulation

Expanded polystyrene (EPS) is the most common material used in Isopanel panels.  It has a high strength to weight ratio and a good water absorption resistance.

Grades available are standard density (16kg/m3) commonly used for walls and ceilings or roofs, and a high density (20 to 24kg/m3) for floors and ceiling panels where its greater strength and increased span capabilities are required.  The above grades are available with either a fire retardant additive or virgin bead that contains no fire retardant additive.  We use the fire retardant grade polystyrene as a standard in our panels and would strongly advise against the use of virgin grade due to its ignitability on contact with a naked flame.

Surface Finishes

PVC laminate is a 120-micron thick PVC skin bonded to the steel skin, which can be safely used where there is continuous contact with unpacked foodstuffs.

Polyester coating of 25 micron thick – resistant to abrasion, stains and acid.  Is suitable for intermittent contact with unpacked foodstuffs.

Technical Performance

The type, thickness and density of the panel core according to application and temperature range.  Operating constraints must be considered in the selection of panel core material and thickness.

Span data weights of standard Isopanel Panels with a polystyrene (EPS) core:

Core Thickness (mm) Max. Unsupported wall height (mm) Max unsupported ceiling length (mm) Panel Weight (kg/m2)

50

3000

2500

10

75

5000

5500

10.3

100

6000

6000

10.7

125

7500

7000

11.1

150

8500

7600

11.5

200

11000

8500

12.3