Do you know why your polycarbonate panel become yellow?

And how long it will keep their color?

Check details below:

The Polycarbonate (PC) manufacturers equip their products for outdoor use with an ultraviolet protective coating.

This ensures that the polycarbonate panel has a long lifetime without losing any of its essential chemical and mechanical properties.

The yellowing of a PC panel is an important issue that both the consumer and the manufacturer must be worried about.

Polycarbonate Yellowing Index

The slightest mistakes which may occur during the manufacturing and the installation process may affect the overall lifespan of the polycarbonate panel.

A polycarbonate panel yellowing warranty vary among manufacturers.This is because there are different grades of polycarbonate UV coating.


This implies that,the high performance coating may have a warranty period of more than ten years while other may have just a three year warranty.

uv_protection for polycarbonate sheet

During the manufacturing process,there could be chances of different flaws which may disadvantage the end user.

A warranty has been designed to take care of such unexpected situations.

When a polycarbonate begins to turn yellow, these panels tend to lose their integrity.

In case this happens before the agreed time,the PC manufacturer should replace the panel either for free or at a subsidized price depending on the circumstances involved such as improper installation procedures.

polycarbonate hollow sheet


Although a substantial amount of UV radiation is blocked by the protective coating,a very small amount may reach the polycarbonate surface.

This causes polycarbonate panel degradation after a predetermined period of time.In case it takes place in an abnormal way then,the polycarbonate yellowing warranty will protect the end user from incurring loses.

Since these tests can only be carried in a lab and the equipment is also expensive,the best way to evade any unforeseen trouble is to buy products with a warranty.

The longer the warranty period the better.Ideally,a warranty reflects the effectiveness of the polycarbonate panels’ UV coating.


Heat stop


The PC’s color (yellow) reflects the amount of strength the polycarbonate molecules have lost when they were exposed to the ultraviolet radiation.

It is a visual symptom with the invisible symptoms being the loss in mechanical strength.


Yellow Index (YI)

This forms the basis from which warranties are calculated.The YI is used to determine the change which has occurred as compared to the original color of the polycarbonate panel.

This change is denoted by delta YI i.e. ΔYI.  The final outcome of the yellow index directly relates to the ability of the polycarbonate sheet to transmit light.

The ΔYI is calculated from a spectrophotometric data.

It is one property which is really essential in most industrial process such as determining the purity of a substance.Thus,it forms a fundamental measurement criteria.

Yellow Index


In most industrial setup,the common type of test which is used to determine YI include the Standard Test Method for Indexes of Whiteness and Yellowness (ASTM).

Research has indicated that the spectral transmission of polycarbonate panels range between 385nm and 500nm.This implies that they are opaque to infra-red radiation.

Polycarbonate panel manufacturers use these to determine the polycarbonate panel yellowing warranty among other factors.


Related article: 

How to Determine Polycarbonate Yellowing Index