Some Background History
The PVC fencing industry was started in the early 1980’s by PVC pipe manufacturers. Unfortunately, many of these PVC pipe manufacturers used the same pipe formulation to make PVC fencing with little success, as a result the destructive ultraviolet (UV) light caused the fencing to break down in the sunlight.
Some of the pipe manufacturers responded to these early failures and developed a more advanced technology. PVC extruded for use in the fence industry has a different composition, or recipe to the PVC used in the other industries such as pipe, windows and doors.
The leading extruders of PVC fencing use a new technology whereby two layers of PVC are chemically bonded together. The process is called Co-extrusion. The outer layer (Cap Stock) contains a dense concentration of UV inhibitors called Titanium Dioxide (TiO2) which slows the breakdown of the PVC surface.
The inner layer (Substrate layer) is essentially the same as the cap stock layer, but with a high concentration of impact modifiers and ingredients to produce a strong product.
As a result these co-extruded PVC fencing profiles are designed specifically to withstand the extreme elements and stresses of the outdoors.
How is PVC made?
The major raw materials used to make PVC resin are all natural – crude oil, natural gas and salt. Ethylene gas is made from crude oil and natural gas; Chlorine gas is made from salt. These gasses are then chemically reacted to form ethylene dichloride (EDC). The EDC is heated to produce two gasses: hydrogen chloride (HCl) and vinyl chloride monomer (VCM).
The VCM is then converted to PVC resin by means of a chemical reaction called polymerization.
The PVC resin is then blended with additives such as UV inhibitors, impact modifiers, stabilizers, pigments and plasticizers to produce PVC for fencing.
TiO2 (titanium dioxide) is the most commonly used compound for UV protection. TiO2, a white pigment, needs to react with water and oxygen in the air to be effective. There are 2 grades of TiO2: chalking grade and non-chalking grade. The more expensive, non-chalking grade used in Fendeck’s PVC fencing and outdoor products, provides a lustrous finish over the life of the product.
Did you know:
Titanium dioxide is used to colour baked goods, such as the popular white-powdered doughnuts!