Multi-Wall Polycarbonate – Beware Tradeoffs

Posted: September 15, 2014 in Polycarbonate
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When it comes to multi-wall polycarbonate, demand outstrips supply. Meaning demand for sheet sizes and profiles outside of the 4′ x 10′ x 6mm (1/4″ nominal) standard. Multi-wall polycarbonate is an excellent plastic for several home projects. The standard sheets are relatively cheap in comparison to other industrial plastics. Unlike standard polycarbonate, multi-wall comes UV-stabilized for outdoor use and can be easily fabricated using household tools. It does not require special hardware – any screw with a washer affixes it just fine.

The problem we see as a plastic distributor is demand for non-standard thicknesses and sizes, most commonly 16mm or 8mm thick material. What you need to realize is those profiles are much rarer and the increase in cost will not be proportional to the increase in sheet thickness. What you also might not realize is the tradeoff you make in properties, not simply in cost.

For example, while there is slight variance among manufacturers, for the most part the properties are very similar. Take these two as an example:

6mm thick twin-wall polycarbonate:

R-value 1.6
Light transmission: 85%

10mm thick twin-wall polycarbonate:

R-value 1.9
Light transmission: 75%*

*In the often requested 16mm multi-wall, light transmission drops to around 64%

Note that by adding 40% to the thickness of the material you gain only 15% R-value (thermal insulation) yet you lose 10% light transmission. In the case of a greenhouse application that 10% can have an effect on plant growth.

The point of all this is to have a clear picture of the cost and consequences of going with thicker multi-wall polycarbonate. It is still an excellent product, but it comes down to a tradeoff you need to be aware of – increased thermal insulation in exchange for increased price and less light transmission.

Any questions? Contact us.








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