Indicator devices and articles comprising the indicator device

1. A method of measuring UV degradation of a plastic article,

the method comprising the steps of:

providing a plastic article;

providing a UV indicator comprising a carrier material having a thickness and a pigment degradable by exposure to UV radiation, the pigment being disposed in the carrier material; and

employing the UV indicator to provide a visible indication related to a useful life of the plastic article, the employing step comprising exposing the plastic article together with the UV indicator to substantially the same cumulative amounts of UV radiation for the useful life of the plastic article, wherein UV degradation of the pigment corresponds to UV degradation of the plastic article, and using UV degradation of the pigment to provide the visible indication related to a remaining useful life of the plastic article.

2. The method of claim 1 , wherein the plastic article comprises a helmet.

3. The method of claim 1 , wherein the visible indication comprises a color change.

4. The method of claim 1 , wherein the carrier material has a varying thickness.

5. The method of claim 4 , wherein the visible indication comprises color disappearing first in a thinner part of the carrier while areas of greater material thickness maintain color.

6. The method of claim 4 , wherein the visible indication comprises a stepwise visible change from a thinner part of the carrier material to a thicker part of the carrier material connected by a stepwise transition.

7. The method of claim 4 , wherein the visible indication comprises a plurality of stepwise visible changes, each from a thinner part of the carrier material to a thicker part of the carrier material connected by a stepwise transition, the change at each step indicating a remaining fraction of useful life of the plastic article remaining or a fraction of useful life of the plastic article depleted.

8. The method of claim 4 , wherein the visible indication comprises a gradual visible change along a surface of the carrier material having a gradually increasing thickness.

9. The method of claim 1 , wherein the visible indication relates to a maximum permitted UV exposure of the plastic article.

10. The method of claim 1 , wherein the visible indication comprises exposing a marking initially concealed by the pigment upon degradation of the pigment.

11. The method of claim 1 , further comprising the step of attaching the UV indicator to the plastic article.

12. A system for determining ageing of a plastic article, the

system comprising:

a plastic article;

a UV indicator comprising a first carrier material having a varying thickness and a first pigment degradable by exposure to UV radiation, the first pigment being disposed in the first carrier material;

wherein the UV indicator is configured to be affixed to the plastic article such that the indicator device and the plastic article would receive substantially the same cumulative amounts of UV radiation;

wherein the first carrier material, the thickness of the first carrier material, and the first pigment are selected and configured such that, upon exposure to UV radiation, UV degradation of the first pigment corresponds to UV degradation of the plastic article, and UV degradation of the first pigment provides a visible indication related to a remaining useful life of the plastic article.

13. A system for determining ageing of a plastic article, the

system comprising:

a plastic article;

a UV indicator comprising a first carrier material having a thickness and a first pigment degradable by exposure to UV radiation, the first pigment being disposed in the first carrier material;

wherein the first carrier material, the thickness of the first carrier material, and the first pigment are selected and configured such that, upon exposure to UV radiation, UV degradation of the first pigment corresponds to UV degradation of the plastic article, and UV degradation of the first pigment provides a visible indication related to a remaining useful life of the article; and

wherein the first carrier material comprises a material having a useful life greater than or equal to the useful life of the plastic article.

14. The system of claim 12 , wherein the UV indicator further comprises a second pigment disposed in the first carrier material, the first pigment having a different fastness to light than the second pigment, wherein the first carrier material, the thickness of the first carrier material, and the first and second pigments are selected and configured such that, upon exposure to UV radiation, UV degradation of the first and second pigments provide a visible indication related to a useful life of the article.

15. The system of claim 14 , wherein the carrier material comprises a first layer and a second layer, the first layer comprising the first pigment and the second layer comprising the second pigment.

16. The UV indicator as recited in claim 12 , further comprising a second carrier material having a thickness and a second pigment disposed in the second carrier material, the second pigment capable of degradation by exposure to UV radiation, and the second pigment having a different fastness to light than the first pigment, wherein the second carrier material, the thickness of the second carrier material, and the second pigment are selected and configured such that, upon exposure to UV radiation, UV degradation of the second pigment provides a visible indication related to a useful life of the article.

17. The UV indicator as recited in claim 12 , further comprising a marking concealed by the first pigment, the marking capable of being revealed upon degradation of the first pigment to provide the visible indication.