PE-LD: Polyethylene Low Density

General Properties


Polyethylene low DensityThe mass density is defined as the ratio between mass and volume. density (PE-LD) consists of extensively branched polymer chains and therefore has a low DensityThe mass density is defined as the ratio between mass and volume. density. It is produced from ethylene under high pressure and belongs to the groups of polyolefins. Based on the volume produced, PE-LD is the most important plastic of all.

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/-30 to -10°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 Temperature100 to 115°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 reactionA decomposition reaction is a thermally induced reaction of a chemical compound forming solid and/or gaseous products. Decomposition Temperature487 to 498°C
Young's Modulus200 to 400 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 Expansion400 *10-6/K
Specific Heat Capacity1.8 to 3.4 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 Conductivity0.3 to 0.34 W/(m*K)
DensityThe mass density is defined as the ratio between mass and volume. Density0.91 to 0.93 g/cm³
MorphologySemi-crystalline thermoplastic
General propertiesTough and elastic, good electric insulation, minimal moisture absorption, approved for food contact.
ProcessingExtrusion (films, profiles), injection moulding, blow moulding, extrusion-coating.
ApplicationsFilms(for a variety of applications), packaging (e.g. containers, plastic bags).

NETZSCH Measurement

InstrumentDSC 204 F1 Phoenix®
Sample Mass12.11 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

A characteristic feature of this polymer is that the melting transition – as in the present case – can start very early (here at approx. 40°C). The peak temperatures of the endothermal melting effects are at 112/113°C (1st heating, blue and 2nd heating, red) and are therefore relatively high for PE-LD. The shoulder in the melting eff ect in the 1st heating (blue) is absent in the 2nd heating (red). It can be concluded from this observation that stresses in the material (thermomechanical history) were eliminated during the 1st heating. The 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 of polyethylene is generally small (small Δcp, i.e., changes in the specific heat level prior to and after the effect) and therefore sometimes hard to detect by DSC.