This post, we cover the process called extrusion, which is how uPVC windows and doors are made. At the beginning, the resin is mixed with *additives and **UV inhibitors before being gravity fed from a top mounted hopper into the barrel of the extruder.
The material then encounters a rotating screw which forces the plastic beads forward and into the barrel which is heated to the desired melt temperature of the molten plastic (ranging from 200 to 275 degrees Celsius). This molten material then enters the die. The die gives the profile its shape as it is being pulled through it.
The product is now cooled and this is achieved by pulling it through a water bath. Once sufficiently cooled, packaging labels and protective tape are adhered to the profiles, then cut into standard lengths for shipping and distribution.
For laminated profiles, there is an additional step of lamination, which is the bonding of the laminate film to the base profile. This is done with a special glue that is resistant to heat and expansion, so the laminate will not peel.
Through research and development, the optimum wall thickness and design of the product materialises. If you wonder why there are chambers within the profile, it is because the number of chambers internally are crucial for the windows and doors to have insulation properties.
Big plastic extrusion companies such as Deceuninck, Kommerling, Veka, Rehau etc. spend millions of dollars each year in research and development to improve the properties and design of their profiles.
* It is pertinent to note that these additives are stabilizers for the profiles. Common stabilizers include Lead and Calcium Zinc. Lead is poisonous, but unfortunately, many extrusion companies still use it. Ask your window fabricator if your product is lead-free.
**Titanium dioxide is also added to uPVC profiles which are used in tropical countries, as these countries have a much higher UV exposure which can wear down the uPVC profiles and cause discolouration. Again, not all manufacturers add Titanium dioxide into the resin mix, as many of their profiles are made for temperate regions. Do make informed decisions and know what you are paying for.
Thank you for reading this post, and I hope it has given you a little bit more of an idea about how uPVC windows and doors are made. Remember, just like any other product, what you see on the surface seldom reflects what goes on behind the scenes.
Find out how you can use UPVC too!