PLA: Polylactide (Polylactic Acid)

General Properties

Structural Formula


Properties

Glass Transition Temperature45 to 65°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 Temperature150 to 160°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 Enthalpy93 to 140 J/g
Decomposition Temperature350 to 375°C
Young's Modulus350 to 2800 MPa
Coefficient of Linear Thermal Expansion-
Specific Heat Capacity-
Thermal Conductivity-
Density1.21 to 1.43 g/cm³
MorphologySemi-crystalline thermoplastic
General propertiesGood mechanical properties, low humidity absorption, high UV-resistance, low flammability.
ProcessingExtrusion, injection molding, melt spinning
ApplicationsFibres (yarns, textiles), packaging, agriculture and horticulture, medical engineering (e.g. suture material).

NETZSCH Measurement

InstrumentDSC 204 F1 Phoenix®
Sample Mass14.32 mg
Isothermal Phase5 min
Heating/Colling Rates10 K/min
CrucibleAl, pierced lid
AtmosphereN2 (50 ml/min)

Evaluation

Polylactic acid showed a glass transition at 63°C in the 1st heating (midpoint, blue) which was overlapped by a RelaxationWhen a constant strain is applied to a rubber compound, the force necessary to maintain that strain is not constant but decreases with time; this behavior is known as stress relaxation. The process responsible for stress relaxation can be physical or chemical, and under normal conditions, both will occur at the same time. relaxation peak as well as a melting peak between approx. 130°C and 180°C (peak temperature 158°C with a preceding shoulder). The following controlled cooling at 10 K/min was too quick for the material to crystallize. Therefore, only a very small melting eff ect at 153°C and a larger glass transition step (with a higher Δcp of 0.57 J/(g·K) compared to 0.22 J/(g·K) in the 1st heating) occurred in the 2nd heating due to the higher percentage of amorphous material.