PS: Polystyrene

CTP

Commodity Thermoplastics

General Properties

Short Name:

Name: 

Chemical Formula:

PS

Polystyrene

(C8H8)n


Polystyrene (PS) can be amorphous or semi-crystalline. In its amorphous form, this thermoplastic is widely used in many areas of daily life. In its expanded (expanded polystyrene – EPS or PS-E) form, it serves as an insulating material. There is atactic, syndiotactic and isotactic polystyrene (more on the tacticity on page 64). Commercial amorphous PS is atactic. The isotactic and syndiotactic types are semi-crystalline and melt at 240°C and 270°C, respectively*. Isotactic polystyrene, however, crystallizes very slowly and therefore does not play a role in industrial processing. Syndiotactic PS crystallizes quickly enough and can be processed in injection molding.

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 Temperature80 to 105°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-
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 Temperature415 to 425°C
Young's Modulus3100 to 3300 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 Expansion50 to 70 *10-6/K
Specific Heat Capacity1.3 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 Conductivity0.14 to 0.18 W/(m*K)
DensityThe mass density is defined as the ratio between mass and volume. Density1.05 g/cm³
MorphologyAmorphous or semi-cristalline thermoplastic
Identificationtransparent
General propertiesCrystal clear and hard, Well resistant to aqueous bases and mineral acids
ProcessingInjection and blow molding, Extrusion
ApplicationsElectrical engineering, Building industry (e.g. expanded polystyrene), Food industry (e.g., packaging), Consumer products for everyday use (e.g., CD covers, cloth hangers)
ModificationsCo-Po with PE, colored, Polymerfoam (EPS)
ManufacturerStyrolution, Styron, Sabic, Nova Chemicals

NETZSCH Measurement

InstrumentDSC 204 F1 Phoenix®
Sample Mass12.36 mg
IsothermalTests at controlled and constant temperature are called isothermal.Isothermal Phases5 min
Heating/Colling Rates10 K/min
CrucibleAl, pierced lid
AtmosphereN2 (40 ml/min)

Evaluation

This example shows amorphous PS. Glass transition temperatures at 84°C (1st heating, blue, midpoint) and 88°C (2nd heating, red, also midpoint) were observed, each overlapped by 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 peaks. The 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 peaks are more distinctive in the 1st heating than in the 2nd heating. The 1st heating shows another small wave after the 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, indicating the elimination of additional StressStress is defined as a level of force applied on a sample with a well-defined cross section. (Stress = force/area). Samples having a circular or rectangular cross section can be compressed or stretched. Elastic materials like rubber can be stretched up to 5 to 10 times their original length.stress. The step heights (Δcp) were at 0.32 J/(g·K) (1st heating) and 0.29 J/(g·K) (2nd heating).

Literature

  1. [1]

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