PLA: Polylactide (Polylactic Acid)

General Properties

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PLA

Polylactide (Polylactic Acid)

Polylactides are polyesters and are biodegradable. The lactic acid that is formed in the hydrolysis serves as nourishment for microorganisms. Ease of degradation is influenced by factors such as the degree of Crystallinity / Degree of CrystallinityCrystallinity refers to the degree of structural order of a solid. In a crystal, the arrangement of atoms or molecules is consistent and repetitive. Many materials such as glass ceramics and some polymers can be prepared in such a way as to produce a mixture of crystalline and amorphous regions.crystallinity and the molecular weight of the polymer. A higher molecular mass results in a higher 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, a higher 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, an increase in tensile strength, and a decrease in breaking elongation.

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	45 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 Temperature	150 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 Enthalpy	93 to 140 J/g
Decomposition reactionA decomposition reaction is a thermally induced reaction of a chemical compound forming solid and/or gaseous products. Decomposition Temperature	350 to 375°C
Young's Modulus	350 to 2800 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 Expansion	-
Specific Heat Capacity	-
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 Conductivity	-
DensityThe mass density is defined as the ratio between mass and volume. Density	1.21 to 1.43 g/cm³
Morphology	Semi-crystalline thermoplastic
General properties	Good mechanical properties, low humidity absorption, high UV-resistance, low flammability.
Processing	Extrusion, injection molding, melt spinning
Applications	Fibres (yarns, textiles), packaging, agriculture and horticulture, medical engineering (e.g. suture material).

NETZSCH Measurement

Instrument	DSC 204 `F1` `Phoenix^®`
Sample Mass	14.32 mg
IsothermalTests at controlled and constant temperature are called isothermal.Isothermal Phase	5 min
Heating/Colling Rates	10 K/min
Crucible	Al, pierced lid
Atmosphere	N₂ (50 ml/min)

Evaluation

Polylactic acid showed 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 63°C in the 1^st 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 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 step (with a higher Δc_p of 0.57 J/(g·K) compared to 0.22 J/(g·K) in the 1^st heating) occurred in the 2^nd heating due to the higher percentage of amorphous material.