In the last post we discussed UV light and how it can cause Polycarbonate sheet to weather. This weathering damages the Polycarbonate causing it to loose impact strength, yellow and have a lower light transmission. Manufacturers can protect Polycarbonate sheet from the effects of weathering by blocking some or all of the UV light; this protection can be achieved in a number of ways and we will discuss some of them in a future blog post.
How successfully sheet manufacturers protect their sheet against the effects of UV can often be determined from the limited warranties that the manufacturers provide to their customers. As with all legal documents it pays to read the small print in these warranties before deciding which product to purchase. Often the marketing claims in the brochures are not directly related to the details in the limited warranties. In this blog we shall examine in detail the warranties of two manufacturers of weather resistant Polycarbonate sheet; by looking at these examples, hopefully it will give you an idea of the items to look for when deciding on which Polycarbonate sheet to buy for applications requiring weather resistance.
It is also worth noting, that for most of the warranties to be honored by the manufacturers, a warranty agreement must be signed at the time of purchase and proof of purchase must be retained. Manufacturers often rely on the fact that only a small percentage of customers complete a warranty form or even know that they exist. When buying a product with a warranty, make sure that you complete the paperwork at the time of purchase and store the necessary documentation in a safe place.
Our first example is a Polycarbonate sheet with marketing documents claiming that the product “offers long-term weatherability and is backed by a 15 year performance warranty.” From this statement a customer might infer that the product will be replaced if it weathers within 15 years. When we inspect the standard warranty we find:
- If the sheet breaks within 15 years it will be replaced.
- If the yellow index of the material increases by more than 5 in a five-year period it will be replaced.
- If the yellow index of the material increases by more than 10 in a ten-year period it will be replaced.
- If the yellow index of the material increases by more than 15 in a ten to fifteen year period the material will be replaced in accordance with the table below.
- If the light transmission of the material reduces by more than 5% in a five-year period it will be replaced.
- If the light transmission is reduced by more than 7% in a ten-year period it will be replaced.
- If the light transmission is reduced by more than 10% in a ten to fifteen year period the material will be replaced in accordance with the table below.
Month 121 Customer must pay 67% of original purchase price
Month 150 Customer must pay 83% of original purchase price
Month 170 Customer must pay 94% of original purchase price
A sheet would normally be considered as badly weathered if the yellow index increase by 15 and if the light transmission is reduce by 10%. If this type of damage occurs after only 10 years and one day and the sheet would only be replaced if the customer paid 67% of the original purchase price, any customer that inferred that the sheet would be replaced free of charge for fifteen years if it weathers would not be correct.
Our second example is a Polycarbonate sheet that has marketing documents claiming: “A ten-year limited warranty backs the material against excessive yellowing, loss of light transmission and breakage.” When we read the standard warranty we find:
- The material will be replaced if it breaks from impact with only hand thrown objects within seven years.
- If the yellow index of the material increases by more than 6 in a seven-year period it will be replaced.
- If the yellow index of the material increases by more than 10 in a seven to ten-year period it will be replaced in accordance with the table below.
- If the light transmission is reduced by more than 6% in a seven-year period it will be replaced.
- If the light transmission is reduced by more than 6% in a seven to ten-year period the material will be replaced in accordance with the table below.
Year 7 Customer must pay 0% of original purchase price
Year 8 Customer must pay 55% of original purchase price
Year 9 Customer must pay 70% of original purchase price
Year 10 Customer must pay 85% of original purchase price
Again, these conditions are very different than an assumption that the material will be replaced free of charge for any weathering damage for a ten year period. The sheet will only be replaced for free for seven years and then only if it weathers more than the amount quoted in the warranty.
Reading these warranties can be very useful in deciding which material to use. If for example, preventing loss in light transmission of more than 6% for ten years is an important parameter then the second material may be the better option. However, it would still be best to talk to the manufacturer about the application and see if they could extend the full replacement cost warranty out to the ten years.
Another example is breakage; if 15 years against breakage is required, the warranty covering the first material is a much better option.
Warranties are a much better method of evaluating how well a manufacturer believes their material performs than marketing brochures. Time taken understanding the warranty and filling in the paperwork can ensure that material is correctly specified and that you are protected if the material does not perform to the expected level.
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