Heat Stability

Colourants may change shade when exposed to elevated temperatures for a period of time. The heat stability (or heat resistance) of a colourant is the resistance to this change in shade when exposed to higher temperatures for a given time.

It is important to note that temperature AND time should be given.

Two typical test procedures are:

1: Mouldings are made at 20˚C intervals between 200˚C to 300˚C and compared to each other to establish colour consistency. The temperature at which a discernible colour change is noted (IE comparable with ISO Grey scale rating of 4) is therefore classed as the heat resistance.

2: Pigmented PVC foils heated in an oven at 180˚C and 200˚C for specified periods. Any change in shade is directly assessed against a similar sample that has not been exposed to this time in the oven. The ISO grey scale 1-5 is used to assess the colour shift.