Polyethylene Terephthalate Polyester ( PET, PETP ) - Properties and Applications - Supplier Data by Goodfellow

Background

Polyethylene terephthalate polyester (PETP) is the most common thermoplastic polyester and is often called just “polyester”. This often causes confusion - not only is the chemically similar polybutylene terephthalate (PBT) also a (thermoplastic) polyester, the most common resin system used in GRP is also a polyester system - and also often called just “polyester”. (In this latter case, however, the polyesters are chemically unsaturated and are “free-radical polymerised” into a thermoset).

General Properties

Polyethylene terephthalate polyester (PETP) is a hard, stiff, strong, dimensionally stable material that absorbs very little water. It has good gas barrier properties and good chemical resistance except to alkalis (which hydrolyse it).

Its crystallinity varies from amorphous to fairly high crystalline. Polyethylene terephthalate polyester (PETP) can be highly transparent and colourless but thicker sections are usually opaque and off-white.

Polyethylene Terephthalate Films

Polyethylene terephthalate polyester (PETP) is widely known in the form of biaxially oriented and thermally stabilised films usually referred to by their main brand names Mylar, Melinex or Hostaphan.

Strictly speaking, these names should be used only for this type of film whose properties are different from, and in several respects superior to, those of “ordinary” polyethylene terephthalate (PET) film.

Applications

These “Mylar®-type” films are used for capacitators, graphics, film base and recording tapes etc. Polyethylene terephthalate polyester (PETP) is also used for fibres for a very wide range of textile and industrial uses (Dacron®, Trevira®, Terylene®).

Other applications include bottles and electrical components.

Key Properties

The key properties of Polyethylene Terephthalate Polyester ( PETP ) are tabulated below.

Table 1. Key properties

Chemical Resistance
Acids – concentrated Good
Acids – dilute Good
Alcohols Good
Alkalis Poor
Aromatic hydrocarbons Fair
Greases and Oils Good
Halogens Good
Ketones Good
Electrical Properties
Dielectric constant @ 1 MHz 3.0
Dielectric strength ( kV.mm-1 ) 17
Dissipation factor @ 1 kHz 0.002
Surface resistivity ( Ohm/sq ) 1013
Volume resistivity ( Ohm.cm ) >1014
Mechanical Properties
Coefficient of friction 0.2 - 0.4
Hardness – Rockwell M94-101
Izod impact strength ( J.m-1 ) 13 - 35
Poisson’s ratio 0.37-0.44 (oriented)
Tensile modulus ( GPa ) 2 - 4
Tensile strength ( MPa ) 80, for biax film 190 - 260
Physical Properties
Density ( g.cm-3 ) 1.3 - 1.4
Flammability Self Extinguishing
Limiting oxygen index ( % ) 21
Refractive index 1.58 - 1.64
Resistance to Ultra-violet Good
Water absorption - equilibrium ( % ) <0.7
Water absorption - over 24 hours ( % ) 0.1
Thermal Properties
Coefficient of thermal expansion ( x10-6 K-1 ) 20 - 80
Heat-deflection temperature - 0.45 MPa ( °C ) 115
Heat-deflection temperature - 1.8 MPa ( °C ) 80
Lower working temperature ( °C ) -40 to -60
Specific heat ( J.K-1.kg-1 ) 1200 - 1350
Thermal conductivity ( W.m-1.K-1 ) 0.15 - 0.4 @ 23
Upper working temperature ( °C ) 115 - 170
Properties Polyethylene Terephthalate Film
Property Value
Dielectric Strength @ 25 µm thick KV.mm-1 300
Dissipation Factor @ 1 MHz 0.016
Elongation at Break % 60 - 165
Initial Tear Strength g.µm-1 18 - 54
Permeability to Carbon Dioxide
@ 25 °C
x10-13 cm3.cm.cm-2.s-1.Pa-1 0.07 - 0.11
Permeability to Hydrogen @ 25 °C x10-13 cm3.cm.cm-2.s-1.Pa-1 0.45
Permeability to Nitrogen @ 25 °C x10-13 cm3.cm.cm-2.s-1.Pa-1 0.0034 - 0.0038
Permeability to Oxygen @ 25 °C X10-13 cm3.cm.cm-2.s-1.Pa-1 0.015 - 0.04
Permeability to Water @ 25 °C X10-13 cm3.cm.cm-2.s-1.Pa-1 100 - 115
Specific Heat KJ.kg-1.K-1 1.3
Thermal Conductivity @ 23 °C W.m-1.K-1 0.13 - 0.15
Properties Polyethylene Terephthalate Fibre
Property Value
Material Medium High tenacity
Specific Modulus cN/tex 700 - 800
Specific Tenacity cN/tex 36 70 - 80
Density g.cm-3 1.39 1.39
Extension to break % 36 13 - 16
Modulus GPa 9 - 11
Shrinkage @ 100 °C % 4 1.5 - 6
Tenacity GPa 0.5 0.9 - 1.1

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Comments

  1. rajasundar amirthalingam rajasundar amirthalingam India says:

    UV Resistance - any scale is there?

  2. Klausberg Sampaio Klausberg Sampaio Brazil says:

    What can I use glue to paste PETg

  3. ganga dharan ganga dharan India says:

    Where is the chemical properties

  4. Amadi Juliet Amadi Juliet Nigeria says:

    Hi,
    PETP as same as polyester films and it's uses.

The opinions expressed here are the views of the writer and do not necessarily reflect the views and opinions of AZoM.com.

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