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Iplex Millennium® is a high stress crack resistant (HSCR) grade of PE100 pipe that provides up to ten times greater resistance to slow crack growth than conventional PE100 pipe. It has the same pressure burst strength of conventional PE100 pipe, but is specifically formulated for use in critical or high value pipeline assets where the risk of premature failure from slow crack growth is possible.Iplex Millennium® provides designers with the opportunity to increase the pipeline’s service life without increasing the wall thickness, providing a safer option and ‘peace of mind’ for the project engineer/system owner.

Material Properties

Mechanical Properties
Property Value & Unit
Density (Specific Gravity) 955kg/m2
Yield Strain 10%
Yield Stress 25MPa
Compressive Strength 32MPa
Tensile Modulus 900MPa
Hardness Shore D 63
Poisson’s Ratio 0.4
Ring bending modulus (3 mins) 950MPa
Ring bending modulus (50 yrs) 260MPa
Thermal Properties
Property Value & Unit
Coefficient of Thermal Expansion 1.8 x 10-4/°C
Thermal Conductivity 0.38W/m.K

Typical Fire Resistance Properties

Property Value & Unit
Ignitability 13
Smoke Development 3
Spread of Flame 7
Heat Evolved 6
Temperature Effect On Pressure Rating

The co-efficient of thermal linear expansion of polyethylene varies with temperature but at ambient lies in the range 1.2 to 2.4 x 10-4 per degree C. In broad terms, this is about twenty times that of steel. and therefore unrestrained pipe will expand or contract much more than the steel structure that may be supporting it.

Should the pipe be fully restrained, the strain due to thermal change will generate stress in the material. However due to the relatively low tensile deformation modulus of polyethylene and assuming a typical ambient temperature fluctuation of less than 40°C, it can be assumed that the safe allowable stress will not be exceeded. Over the longer term, stress relaxation will increase the ability of polyeth­ylene to accommodate high thermal strains.

The conductivity of polyethylene varies with temperature almost linearly and is typically 0.47 W/m.K at 0°C to 0.37W/m.K at 70°C.

The specific heat of polyethylene varies with temperature from 1800 Joules/kg.K at 0°C to 2200J/kg.K at 60°C.

All temperatures above 25°C it is necessary to rerate polyethylene pressure pipe systems. The table below provides guidance as to the maximum operating pressure of PE100 pipes at temperature. It should be noted that at constant temperatures greater than 40°C. the 50-year design life of POLlplex® pipes may be reduced.

Thermal rerating of PE100 polyethylene POLIplex® pipe

Maximum allowable operating pressure - PE100 Water pipe (m head)

Temp°C PN4 PN6.3 PN8 PN10 PN12.5 PN16 PN20 PN25
20 40 63 80 100 125 160 200 250
25 36 58 73 91 115 145 182 227
30 36 58 73 91 115 145 182 227
35 33 53 67 83 106 133 167 208
40 33 53 67 83 106 133 167 208
45 (35 y)* 31 49 62 77 99 123 154 192
50 (22 y)* 29 46 57 71 91 114 143 179
55 (15 y)* 29 46 57 71 91 114 143 179
60 (7 y)* 27 43 53 67 85 107 133 167
80 (1 y)* 20 32 40 50 63 80 100 125

i. The values tabled are for POLlplex® pipe manufactured to AS/NZS 4130 and fittings made from compounds complying with AS/NZS 4131.

ii. The times given in years as (35y) are allowable extrapolation limits obtained by applying the factors in Table 1 of ISO 9080 to two years of test data at 80°C. Where appropriate. specific advice should be obtained from the manufacturer. and data provided shall be derived from testing to ISO 9080.

Comparison of Conventional PE100 to Millennium®’s Performance

Iplex’s Millennium® performance is identical to conventional PE100 pipe with the exception of Slow Crack Growth (SCG) resistance. In independent testing, Millennium® has demonstrated 10 times greater time to failure due to SCG than that which is required of conventional PE100 pipes.

  Conventional PE100 Pipe Performance Iplex’s Millennium®
50 Year MRS @ 20°C 10MPa 10MPa
Hoop Strength 5.4 MPa @ 80°C 165h 165h
Hoop Strength 5.0 MPa @ 80°C 1,000 h 1,000 h
Strain at Yield 10% 10%
Elongation at Break ≥ 350% ≥ 350%
Slow Crack Growth (NPT/ ISO 13479) ≥ 500 h ≥ 5,000 h
Chemical Resistance

Polyethylene is a polyolefin resin. in chemical terms a non-polar high molecular weight paraffin of the hydrocarbon family. Hence it is very resistant to (non-oxidising) strong acids, strong bases and salts. II is mildly affected by aliphatic solvents although aromatic and chlorinated solvents will cause some swelling. Polyethylene is affected by strongly oxidising substances such as halogens and concentrated inorganic acids. POLlplex® pressure pipes should not be used to convey water disinfected with chlorine dioxide at any temperature which has been found to rapidly deplete the antioxidant additives at elevated temperature. A full Chemical Resistance Library can be viewed on lplex's website

View the Iplex Chemical Resistant Tool