POM (homo): Polyoxymethylene (Homopolymer)

General Properties

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POM (homo)

Polyoxymethylene (Homopolymer)


Polyoxymethylene, also designated POM-H, belongs to the classical engineering plastics. It has a large linear structure and is mostly produced from formaldehyde by means of polmyerization. POM as a homopolymer is mostly highly crystalline; 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 is typically between approx. 64% and 77%.

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-85 to -75°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 Temperature175 to 190°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 Enthalpy316 to 335 J/g
Decomposition Temperature365 to 390°C
Young's Modulus2600 to 3200 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 Expansion160 to 180 *10-6/K
Specific Heat Capacity1.48 to 1.50 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 Conductivity0.30 to 0.37 W/(m*K)
DensityThe mass density is defined as the ratio between mass and volume. Density1.39 to 1.43 g/cm³
MorphologySemi-crystalline polymer
General propertiesGood stiffness, toughness and strength. Low humidity absorption. Good resistance to creeping and fatigue. High recovery capability. Good sliding properties. Food-compatible
ProcessingInjection molding, extrusion, blow molding
ApplicationsAutomobile industry. Instrument and apparatus engineering. Electrical/electronics industry. Food industry. Household goods

NETZSCH Measurement

InstrumentDSC 204 F1 Phoenix®
Sample Mass10.88 mg
IsothermalTests at controlled and constant temperature are called isothermal.Isothermal Phase7 min
Heating/Colling Rates10 K/min
CrucibleAl, pierced lid
AtmosphereN2 (40 ml/min)

Evaluation

The high 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 of POM-H is reflected in the above DSC curve. It is dominated by a distinctive melting effect at 183°C (1st heating, blue, peak temperature) and 181°C (2nd heating, red, also peak temperature) as well as a quite small 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 at -77°C (midpoint). The height of 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 step Δcp is a measure for the amorphous content in the material while the melting enthalpy (here 195 J/g in the 2nd heating) is related to the crystalline content (in this case 62% – based on a theoretical enthalpy of a 100% crystalline material of 316 J/g); the larger the melting enthalpy, the larger the crystalline content. For semi-crystalline polymers, the magnitude of 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 and the height of the melting enthalpy are inversely proportional (i.e., if the heat of fusion increases, 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 step gets smaller and vice versa).