PE-HD: Polyethylene High Density

General Properties


PE-HD has a structure with relatively little branching and therefore high DensityThe mass density is defined as the ratio between mass and volume. density (typically between 0.94 g/cm3 and 0.96 g/cm3).
PE-HD is produced by a low-pressure polmyerization method.

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 Temperature125 to 135°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 Enthalpy293 J/g
Decomposition reactionA decomposition reaction is a thermally induced reaction of a chemical compound forming solid and/or gaseous products. Decomposition Temperature480 to 498°C
Young's Modulus600 to 1400 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 to 250 *10-6/K
Specific Heat Capacity1.8 to 2.7 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 Conductivity0.33 to 0.53 W/(m*K)
DensityThe mass density is defined as the ratio between mass and volume. Density0.94 to 0.96 g/cm3
MorphologySemi-crystalline thermoplastic
General propertiesBetter chemical reistance compared to PE-LD, good electrical insulating properties.
ProcessingExtrusion (foils, profiles), Blow moulding, extrusion (foils, profiles), deep-drawing, injection moulding.
ApplicationsFilms (for different applications), packaging for household and industry (e.g. bottles, plastic bags, beverage bottles caps), gas and water pipes, cable lines.

NETZSCH Measurement

InstrumentDSC 204 F1 Phoenix®
Sample Mass10.49 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

Although PE-HD belongs to the semi-crystalline thermoplastics, the measurement curves reflect only a melting effect with a peak temperature of approx. 133°C and a melting enthalpy of approx. 201 J/g (2nd heating, red). 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 range would have been expected between -130°C and -100°C; however, the specific heat changes are probably too small to be detected in this case. PE-LD and PE-HD differ significantly in their 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 temperature. While the low DensityThe mass density is defined as the ratio between mass and volume. density polyethylene (PE-LD) has a peak temperature of 112°C in the 2nd heating (red), the above example for high-DensityThe mass density is defined as the ratio between mass and volume. density polyethylene (PE-HD) has a peak temperature of 133°C. Linear low-DensityThe mass density is defined as the ratio between mass and volume. density polyethylene (PE-LLD) shows a melting effect with characteristic double peak structure , with a main peak temperature (approx. 124°C) that lies between the two previously mentioned values.