PVC (polyvinyl chloride) is a compound used in the manufacture of vinyl fences.

It uses petroleum and salt (which is sodium chloride.)

Heating Petroleum or natural gas creates ethylene (this process is called “cracking”.)

While the heating is going on, the salt (which is in sea water) has an electric current put through it (called electrolysis) which extracts the chlorine from the salt.

The chlorine and ethylene is then combined to make ethylene dichloride.

This is then put through an additional cracking process which gives vinyl chloride monomer gas (VCM.)

The VCM molecules are then combined with one another which provides vinyl resin which is a fine white, powdery, flour-like, substance. This process is called “polymerization.”

This vinyl resin has modifiers added to it for the different properties needed for fences in processes called mono extrusion or co-extrusion (explained below.)

These are:

• UV Inhibitors (titanium dioxide) which prevent sun damage such as fading and chalking.
• Impact modifiers (acrylic or rubber) for more durability, flexibility and damage resistance. If these modifiers are not used, the vinyl would be easily breakable and brittle.
• Stabilizers (small amount of metal, usually aluminum or organic salt) which keep the composition of the vinyl intact and also helps to resist changes in temperature.
• High-quality dyes and colors for the color of the fence.

Monoextrusion and Co-extrusion.

Monoextrusion is a method which involves pushing the vinyl resin through a barrel (which is heated) and passed through a die (basically a shaped hole) then cooled and cut into the desired lengths for the fence.

Co-extrusion is a more advanced method which takes the monoextrusion process to another level. This process feeds two streams of vinyl into a single die. This allows the manufacturer to selectively feed different additives into the product.

The additives are added to the outer layer and inner layer separately.

The outer layer gets added UV protection from the sun and the inner layer gets impact modifiers mentioned above for added strength and flexibility.

Because the additives are added only to the parts that need it in the co-exclusion process, you get less wastage instead of all additives to both layers.

This also helps with costs as the UV inhibitors are expensive and so only adding them to the outer layer instead of throughout the product, cuts down on costs.

However, the equipment needed for co-exclusion is more expensive than the equipment needed for mono exclusion.

A word of caution is that cheaper produced vinyl will have a thinner outer layer of so scratches can show the inner layer which isn’t colored.

High quality vinyl will have a thicker layer so a dent or scratch will not show the different color below.

Injection Molding

Sometimes, if the fence is a distinctive shape, the fence is produced using injection moulding which takes the heated vinyl and puts it into a hollow, 3D mood, usually for the pickets and post caps of the fence.

These, along with the co-extruded parts are then assembled to make the fence.

The whole process of manufacturing vinyl is tightly controlled and there is virtually no industrial waste at the end of the process.

These days, nearly every manufacturing company uses co-extrusion because it is the most efficient way of producing vinyl fences and so gives the most value to the customer.