What is uPVC?

September 10, 2019

upvc window sapphire windows

What is uPVC? You may or may not have heard of this compound as a building material, but let me demystify this complex sounding compound. Be warned, not for the faint hearted!

UPVC stands for unplasticised polyvinyl chloride. Oh, polyvinyl chloride? Isn’t that the cheap, soft plastic that is used for iPhone covers and food containers? Not quite….


History of uPVC

Though traditional forms of PVC was accidentally discovered at least twice in the 1800s, the first by Henry Victor Regnault (right insert) in 1838, it was only in 1950s that PVC began to take on commercial use. Today, unplasticised polyvinyl chloride (uPVC) is a modern synthetic material made by the chemical synthesis of chlorine and ethylene (carbon and hydrogen). The components originate from naturally occurring raw materials of petroleum and common salt.  The raw materials are in the powder form before any chemical reactions begins. Unplasticised means that the material has not been softened by the addition of additives called plasticisers. This results in a very rigid and stable form of plastic, suitable for load bearing applications, such as windows and doors. As the material does not contain plasticisers (i.e phthalates) or BPA, it is safe enough even to be used as mouth guards and retainers.

Chart of PVC production process

Let me bring to you some physical properties for you curious minds out there.

Molecular structure of pvc

Tensile strength = 36 – 62 MPa
Bending strength = 69 – 114 MPa
Compressive strength = 55 – 89 MPa
*Note: MPa = Mega Pascal

Chemical resistance:
PVC has excellent chemical resistance due to stabilizing additives included in it’s production stage. It is inert to light, chemicals and corrosion. Together with good mechanical properties, it is used for windows and doors, chemical storage tanks, plastic valves/flanges, drainage/sewage pipes, and plant piping.

Fire retardant properties:
When PVC products are burned, hydrogen chloride gas resulting from thermal cracking slows down the continuous combustion reaction and prevents burning progress by warding off the PVC product surface from oxygen in the air. Since PVC is highly fire resistant, in some cases actually preventing the fire from spreading, it is widely used in exterior construction materials such as window profiles, siding boards, or interior housing materials, such as wall-covering and flooring.

PVC is a plastic and thus weldable by heat welding techniques. When applied to windows, this creates an absolute seal of the window at all four corners which increases the strength and insulation against sound and heat of the window.

Coefficient of thermal expansion:
With a coefficient of thermal expansion (linear) of 5×10-5 mm/(mm °C), PVC will not expand or contract much during temperature change, which means it is less likely to fail due to fatigue.

**Data is from an independent source. Read more at http://www.pvc.org/en/p/pvcs-physical-properties.

[Please do take note that the above is generic test data done on uPVC material. It must be noted that different uPVC production plants their own unique mix of chemicals used to generate profiles that may have varying physical properties from the above.]

Wow! That was a mouthful of technical (another word for boring) stuff, but I hope that this post enlightens you a little on the reason why uPVC is a suitable and popular (in Europe) material for windows and doors.

In our other post, find out how modern day extrusion of uPVC profiles are done to further optimise the physical properties of uPVC so as to make them suitable for use as windows and doors in today’s construction of buildings.