Today, vinyl siding is manufactured by coextrusion. Two layers of PVC are laid down in a continuous extrusion process; the top layer is weatherable capstock, which comprises about a third of the siding thickness. This capstock includes about 10% titanium dioxide, which is a pigment and provides resistance to breakdown from UV light. Vinyl siding, like paint, will inevitably fade over time, but the fade rate is somewhat slower with vinyl, and in any house cladding (vinyl, paint or others) the intensity of the color is in direct correlation to the rate of fade. For example, two currently popular colors are "barn red" and "clay". In reaction to sunlight, the barn red will fade faster than the very neutral clay color whether paint, vinyl siding or other composition. The lower layer, known as substrate, is typically about 15% ground limestone (which is largely calcium carbonate). The limestone reduces cost, and also balances the titanium dioxide, keeping both extrusion streams equally fluid during manufacturing. A small quantity of tin mercaptan or butadiene is added as a stabilizer to chemically tie up any hydrochloric acid that is released into the PVC material as the siding ages. Lubricants are also added to aid in the manufacturing process.[3]
[edit] Specs and product Variables
Vinyl siding can be observed in a wide range of product quality realized in a substantial differences in thickness and lasting durability. Thickness can vary from .35 mil in cheaper grade siding products up to .52 mil in the highest grade products which vary from manufacturer to manufacturer. Today, the thinnest vinyl siding commonly used is of .40 mils, and is known as "builder's grade". Vinyl product can vary in thickness even within one manufacture up to .10 mil of thickness through varying product lines offered that range from basic to premium grade products. Thicker vinyl products, usually realized in higher cost, are more rigid which can add to the aesthetic appeal and look of the installed, inherently flexible product and also add to durability and life expectancy. Thicker grades of vinyl siding also have much more resistance to the most common complaint about vinyl siding - it's tendency to crack in very cold weather when it is struck or bumped by a hard object.
Chemical formulas can also vary somewhat from manufacturer to manufacturer which can impact life expectancy. Most important is a UV coating that most major manufacturers apply to the surface of the product that filters out UV spectral light from the sun which would otherwise degrade the PVC more quickly. As a rough general rule, the higher the grade (and price) of the siding, the more resistant it is to fading (intensity of the color being taken into consideration, as mentioned above).
Vinyl siding is manufactured with its own partial fastening or locking system that is coupled with nails that 'loose' fasten the product to the exterior wall. This locking system can be either a rolled or an extruded lock depending on the manufacturing process, either of which having its own design considerations. This locking system has a bottom lock which locks into either a start piece or onto the top lock of the panel below. The top lock is then 'loose' nailed to hold the panel to the wall. This 'loose' nailing allows for float which is created by expansion and contraction from varying temperature and weather conditions. With well designed siding, and proper 'loose nailing' installation, the siding can easily expand up, down, in and out, and left and right without restriction. Vinyl siding, by it's nature, will tend to expand and contract more with temperature extremes than any other common type of cladding.
(C) Wikepedia http://en.wikipedia.org/wiki/Vinyl_siding
(C) Wikepedia http://en.wikipedia.org/wiki/Vinyl_siding