PE-UHMW: Polyethylene Ultra High Molecular Weight

General Properties

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PE-UHMW

Polyethylene Ultra High Molecular Weight


Polyethylene of ultra high molecular weight (PE-UHMW) has very long molecular chains. It is a polyethylene with an extremely high molecular weight of more than 1 mio. g/mol; the mean molar mass is approx. 6 mio. g/mol. Wear resistance and impact strength, in particular, improve with increasing length of the polymer chains.

Structural Formula


Properties

Glass Transition TemperatureThe glass transition is one of the most important properties of amorphous and semi-crystalline materials, e.g., inorganic glasses, amorphous metals, polymers, pharmaceuticals and food ingredients, etc., and describes the temperature region where the mechanical properties of the materials change from hard and brittle to more soft, deformable or rubbery.Glass Transition Temperature-130 to - 100°C
Melting Temperatures and EnthalpiesThe enthalpy of fusion of a substance, also known as latent heat, is a measure of the energy input, typically heat, which is necessary to convert a substance from solid to liquid state. The melting point of a substance is the temperature at which it changes state from solid (crystalline) to liquid (isotropic melt).Melting Temperature130 to 145°C
Melting Temperatures and EnthalpiesThe enthalpy of fusion of a substance, also known as latent heat, is a measure of the energy input, typically heat, which is necessary to convert a substance from solid to liquid state. The melting point of a substance is the temperature at which it changes state from solid (crystalline) to liquid (isotropic melt).Melting Enthalpy-
Decomposition Temperature480 to 490°C
Young's Modulus570 to 790 MPa
Coefficient of Linear Thermal Expansion (CLTE/CTE)The coefficient of linear thermal expansion (CLTE) describes the length change of a material as a function of the temperature.Coefficient of Linear Thermal Expansion200 *10-6/K
Specific Heat Capacity1.84 J/(g*K)
Thermal ConductivityThermal conductivity (λ with the unit W/(m•K)) describes the transport of energy – in the form of heat – through a body of mass as the result of a temperature gradient (see fig. 1). According to the second law of thermodynamics, heat always flows in the direction of the lower temperature.Thermal Conductivity0.41 to 0.51 W/(m*K)
DensityThe mass density is defined as the ratio between mass and volume. Density0.93 to 0.94 g/cm³
MorphologySemi-crystalline thermoplastic
General propertiesGood sliding characteristics, high abrasion resistance, very low water absorption, high chemical resistance, very high impact strength.
ProcessingCompression moulding, extrusion.
ApplicationsFibres (light, high-stiff, e.g. reinforcement, sport accessories), medical engineering (implants), cables.

NETZSCH Measurement

InstrumentDSC 204 F1 Phoenix®
Sample Mass12.52 mg
IsothermalTests at controlled and constant temperature are called isothermal.Isothermal Phases20 min/2 min/20 min
Heating/Colling Rates10 K/min
CrucibleAl, pierced lid
AtmosphereN2 (40 ml/min)

Evaluation

Like all polyethylenes, PE-UHMW is a semi-crystalline thermoplastic. The example shown exhibited a Glass Transition TemperatureThe glass transition is one of the most important properties of amorphous and semi-crystalline materials, e.g., inorganic glasses, amorphous metals, polymers, pharmaceuticals and food ingredients, etc., and describes the temperature region where the mechanical properties of the materials change from hard and brittle to more soft, deformable or rubbery.glass transition at -122°C (with a very small change in specific heat of 0.03 J/(g·K)) only in the 2nd heating (red curve). The present sample was not granular. Rather, it was but a fine powder. Due to SinteringSintering is a production process for forming a mechanically strong body out of a ceramic or metallic powder. sintering of the powder during the 1st heating (blue), the melting effect (peak temperature) shifted by about 10 K to lower temperatures (from 146°C to 135°C) in the 2nd heating (red). The melting enthalpy decreased by approx. 19% from 185 J/g to approx. 150 J/g in the 2nd heating.