The available polycarbonate sheets are manufactured under rigid quality control specifications to meet the desired criteria.
Quality control begins from the extrusion process through to the final treatment stages where they are coated with various protective layers to prolong their service lifespan.
These reactions degrade the polymers’ core properties.
The degradation process manifests itself in several ways such as surface discoloration (turning yellow) which affects the aesthetic appeal of the polycarbonate sheet.
It may affect the mechanical properties of the sheet which reduces its performance significantly.
This is the reason why photo stabilizers or polycarbonate sheets UV coating are used in this industry.The most disastrous ultraviolet radiation is the UV-B type.
Naturally,the amount of UV radiation will determine the useful lifetime of any polycarbonate sheets.
Even those products with the most efficacious polycarbonate sheets UV coating will be affected with the variation in the UV intensity in the atmosphere at some point.
A major factor which has contributed to this degradation process,more so with advancement in technology is the global warming which depletes the stratospheric ozone layer.
As the ozone layer depletes partially,the amount of UV-B in the atmosphere also increases and so is the amount of damage on the polycarbonate sheets.
The amount of damage caused on the PC sheets is dependent upon the intensity of UV-B available.In fact,marginal increase in UV-B can translate to a greater decrease in service life of these sheets.
The polycarbonate sheets UV coating protects these sheets from loss of mechanical integrity.
Some of the essential mechanical integrity of polycarbonates include high impact strength and durability.When a polycarbonate sheet is exposed to UV-B radiation,the photo-degradation transforms the polymers’chain scission.
As the molecular strength decreases,the molecular weight decreases significantly.
Furthermore,the presence of certain metal compounds act as a catalyst in this process.This is one of the main reason why the polycarbonate manufacturers do indicate those cleaning agents which should be used during the cleaning process.
The UV-A is responsible for the yellowing wavelengths.
As the ozone layer depletes due to global warming,the amount of UV-A and UV-B increases significantly.
Normally,the UV rays do not “penetrate” these sheets.they mainly attack the outer layer of the polycarbonate sheet.
Since the amount of UV radiation varies from one place to the other,PC sheets may have different degrees of polycarbonate sheets UV coating.
Therefore,you need to specify the exact region where you’re planning to install these sheets.The nature the thin microscopic layer which is used to coat the PC sheets will determine the warranty period.
It is also an important aspect which differentiates various types of PC sheets in the market.The degradation process is determined based on the yellow index (YI) of the sheet.
The YI is calculated from the spectrometric data and it indicates the change which exists between the test sample and the clear color (white).
Anyway,If no UV on the polycarbonate sheet,there will no any quality warranty,when you buy polycarbonate sheet,remember check how thickness your supplier will add the UV layers,this is the key factor to affect your sheet quality.