What Is Vinyl Siding

What Is Vinyl Home Siding, Really?

What is vinyl siding? Probably every article you've ever read about vinyl siding states that it is a form of polyvinyl chloride, or PVC. The article then goes on to tell you what an excellent value vinyl siding is, and lists all the performance benefits of choosing it for your home. One thing it probably never mentions again, though, is polyvinyl chloride. Well. Polyvinyl chloride, of course. Clears everything right up, doesn't it? However, if you aren't intimately familiar with a chem lab, and can't remember the difference between a covalent bond and a bail bond, then like millions of consumers you probably just nod and smile and move on. But if you're going to slap several hundred square feet of PVC-derived siding on your home, maybe it's a good idea to know the very basics. You know what wood is, after all, and aluminum and steel. Why not demystify PVC?

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What Is Vinyl Siding & What is Polyvinyl Chloride?

Without getting very technical, polyvinyl chloride is a thermoplastic polymer. Thermoplastic just means that when it gets hot it melts to a liquid, and when it gets cold it becomes very hard, and even brittle. (Think of a thermoplastic as chocolate, if that helps.) This is why vinyl siding expands during hot weather, and shrinks during cold weather.

A polymer is simply a very large chain made up of many, many (many!) linked, identical parts. Each polymer chain is essentially 'sticky' and can attach to other polymer chains. This helps to make them stronger. There's strength in numbers, after all!

Polymers can be natural or synthetic. Plastics and proteins are both polymers. Examples of natural polymers are shellac, amber, and the cellulose that you find in wood and paper. Synthetic polymers include neoprene, nylon, and silicone.

Why Polymers are Used to Make Vinyl Siding

Still, what's so great about polymers? Why is vinyl siding made of the synthetic polymer PVC?

The reason polymers are so popular in both nature and the manufacturing industry is that they are strong, light, long-lasting, and hard to break. They are also inexpensive, easy to form into shapes, and recyclable.

PVC is a special, and specific, type of polymer. As noted before, it's thermoplastic, which has obvious advantages, especially when it comes to creating shapes. PVC is an extremely popular and valuable polymer because it is inexpensive, durable, and easy to assemble.

PVC has characteristics that make it make it particularly attractive to the construction industry. In fact, 50% of all PVC is used in construction. It's biologically and chemically resistant, for example, so it won't react or corrode. This makes it an excellent substitute for pipes that might otherwise rust and break down over time, as well as many other uses. For instance, it is used to make sewer pipes, the insulation on wiring, and window and door frames.

Adding extra ingredients, called plasticizers, can make PVC softer and more flexible even stretchy in some cases. This adaptability means that PVC is used in everything from clothing and upholstery to flooring, tubing, IV bags, and kids' inflatable bounce houses, among other things.

How is Vinyl Siding Made?

The same biological and chemical resistance that makes PVC an ideal choice for pipes also makes it an excellent siding material. It is strong and long-lasting, and not affected by factors such as prolonged exposure to sunlight or inclement weather.

Vinyl siding unlike upholstery and bounce houses is made with what is called uPVC, or unplasticized polyvinyl chloride, so that it is firm and sturdy. It is also known as Rigid PVC.

To make the siding, the uPVC plastic resin is heated (there's that thermoplasticity at work again) until it melts. Pigments are added to the molten resin and mixed in. This is what gives vinyl siding its full color depth, and helps it camouflage scratches. The color is mixed and baked through, like adding food coloring to a candy mixture.

Next, the molten PVC is extruded, or forced out, through a die, or mold, into sheets. The sheets are then embossed, usually with a brushed or woodgrain pattern, to give the sheets some texture and visual interest.

Embossing the vinyl sheets also helps dull PVC's natural (and distracting) shine and helps it look less synthetic. Then, while the vinyl sheets are still hot, they are formed into siding panel profiles.

Aside from the plasticizers that can turn PVC into soft, malleable materials, other additives are sometimes added to PVC during manufacture. Each one has a purpose some improve impact resistance, others prevent color fading or ultraviolet damage.

Reduce, Reuse, Recycle

As mentioned before, one of the advantages of polymers is that they're recyclable. And one of the benefits of PVC is its thermoplasticity, which means it can be heated and cooled repeatedly, just like chocolate. Both of these attributes have helped manufacturers find a way to use old PVC while creating new vinyl siding panels. This helps to cut costs as well as to reduce waste.

Some manufacturers have set up something called a 'co-extrusion process,' which fuses layers of vinyl. The bottom extruded layer is a combination of new and scrap vinyl. The top layer is virgin vinyl, which contains all the weathering, flexibility, and other additives. This newly-minted top layer is called cap stock, and it usually represents about 30-35% of the total thickness of the siding panel.

As a result of all this scientific innovation, today's vinyl siding is a better, more reliable product than ever. Its origins as a thermoplastic polymer make it strong and sturdy, as well as inexpensive to produce. Additives help it flex, prevent fading, and enhance its natural ability to resist biological, chemical, and other damages, including impact. Responsible manufacturers can produce an even more cost-effective and environmentally responsible form of vinyl siding by incorporating recycled materials.

Consequently, today's vinyl siding manufacturers usually provide generous warranties that reflect the hardiness and endurance of PVC-based vinyl siding. They can vary from 50-year or even lifetime warranties to the original owner, and some even offer transferable warranties.

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