PBT: Polybutylene Terephthalate

General Properties

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PBT

Polybutylene Terephthalate

Polybutylene terephthalate (PBT) is a polyester and has properties similar to that of polyethylene terephthalate (PET, see page 112). It is, however, better suited for injection molding due to its cooling and processing behavior.

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	40 to 60°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	220 to 230°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	142 J/g
Decomposition reactionA decomposition reaction is a thermally induced reaction of a chemical compound forming solid and/or gaseous products. Decomposition Temperature	400 to 420°C
Young's Modulus	2500 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	80 to 100 *10^-6/K
Specific Heat Capacity	1.3 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 Conductivity	0.25 to 0.29 W/(m*K)
DensityThe mass density is defined as the ratio between mass and volume. Density	1.30 to 1.32 g/cm³
Morphology	Semi-crystalline thermoplastic
General properties	High stability and stiffness. Good chemical resistance to many solvents. High dimensional stability. Good friction and wear properties
Processing	Injection molding, extrusion
Applications	Electrical engineering/electronics. Vehicle manufacturing. Household goods

NETZSCH Measurement

Instrument	DSC 204 `F1` `Phoenix^®`
Sample Mass	12.06 mg
IsothermalTests at controlled and constant temperature are called isothermal.Isothermal Phase	3 min/ / 3 min / 5 min
Heating/Colling Rates	10 K/min
Crucible	Al, pierced lid
Atmosphere	N₂ (50 ml/min)

Evaluation

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 (here at 42°C, midpoint) and a clearly structured endothermal melting effect for the α (peak temperature 226°C) and β phase (peak temperature 217°C) in the 2^nd heating (red) are characteristic of PBT. In the 1^st heating (blue), 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 midpoint temperature of 44°C was comparable to that in the 2^nd heating, but is overlapped with 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. Prior to the melting transition, a Post Crystallization (Cold Crystallization)The post crystallization of semi-crystalline plastics occurs primarily at elevated temperatures and increased molecular mobility above the glass transition.post crystallization (small ExothermicA sample transition or a reaction is exothermic if heat is generated.exothermal peak at 207°C) occurred in the 1^st heating.