What is the Polyurethane (PUR) thermoplastic elastomere ?

General

Polyurethane has become increasingly important in the cable industry over the past years. This material shows at certain temperatures mechanical characte­ristics similar to rubber. The combination of thermoplastic and elastic characte­ristics has led to the description TPE  thermoplastic elastomere. Here at SAB Bröckskes GmbH & Co KG, we use PUR on a Polyether base as sheath material. In addition to standard Polyurethane, thanks to constant development between SAB Bröckskes and the plastic industry, the following types of PUR are also available:



    PUR semi-mat (low adhesion)
    PUR mat (rough surface, low adhesion)
    PUR flame protected
    PUR halogen-free and flame protected


Mechanical characteristics

The insulation materials of the cables are usually not subject to high mechanical stress. Sheaths, on the other hand are heavily used. This is especially true for flexible control and connection cables which are often pulled over sharp corners and rough surfaces. This can lead to cuts which are accentuated when the cable is stretched during flexible use. Compressive stress caused by squashing and impacting from tools and machines can also occur. The most important mechanical characteristics of PUR are:



    high tensile strength
    high tear resistance
    notch resistance
    abrasion resistance
    alternate bending resistance
    impact resistance
    flexibility at low temperatures


Chemical resistance

The chemical resistance depends upon many factors such as chemical type, reaction time, temperature, volume, concentration and of course the type of Polyurethane used. In comparison with many other materials, such as rubber or PVC, PUR has a better resistance against chemical reaction. The outstanding chemical characteristics are:



    very good resistance against mineral oils
    good resistance against alcohol-free benzine
    good resistance during storage in water
    good resistance against many solvents



The danger of decomposition through microbes exists with Polyurethane on a Polyester base after prolonged exposure to dampness and warmth. The Polyurethane on a Polyether base used by SAB is resistant to microbic decomposition. Etherpolyurethane and Esterpolyurethane can be differentiated by the saponification value (VZ).



    Etherpolyurethane (resistant) - VZ ≤ 200
    Esterpolyurethane (non-resistant) - VZ ≥ 350



After prolonged exposure to warm water or tropical climates, Polyurethane on a Polyester base will undergo a che­mical reaction. The result is a weakening of mechanical strength. SAB Polyurethane on a Polyether base is relatively more resistant to hydrological break-down.

Etherpolyurethane is weather and ozone resistant in all climates. Discolouration by sunlight is possible, but this will not affect performance.

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