PVC is a fascinating material with many uses across various industries, whether you’re looking at semi-rigid injection compounds or rigid extrusion compounds. However, the way it reacts to temperature is fairly consistent across different formulations.
In this blog, we highlight what happens to PVC at different temperatures so that you can better understand how it should be used for maximum effectiveness.
Below Freezing
When temperatures are below 0 °C, PVC becomes more rigid and brittle because the molecular motion within the polymer chains slows down, making the material less flexible.
If frequently exposed to these cold temperatures, PVC has the potential to become brittle and crack under stress. The thermal contraction that takes place under such sub-zero temperatures can also cause PVC to undergo subtle dimensional changes.
These contractions need to be taken into account where applications involving tight fittings or structural components are concerned.
Room Temperature
When PVC is subjected to room temperature, generally between about 0 °C and 25 °C, it exhibits a more stable mechanical state. This means it maintains a good balance between flexibility, durability, and strength.
At room temperature, PVC tends to perform optimally, making it suitable for a wide range of applications. Thermal expansion or contraction at these temperatures is virtually nothing, thereby ensuring dimensional stability for industrial or manufacturing uses.
Moderate Heat
When the temperature rises above 25 °C, up to about 60 °C, PVC becomes more flexible. The polymer chain gains mobility, which enhances the material’s flexibility. This is useful when developing products such as hoses or flexible tubing.
Although PVC will remain solid at these temperatures, prolonged exposure, particularly towards the upper limit of this temperature range, can cause the material to soften slightly.
In some cases, this can affect the material’s load-bearing capacity and shape retention capabilities when put under stress.
High Temperatures
When subjected to temperatures between 60 °C and 100 °C, PVC softens more significantly. In many cases, it might even deform under its own weight or external loads. This is owing to the increased molecular motion within the polymer chain, which reduces the intermolecular forces that hold the polymer chains together.
Certain formulations of PVC compounds allow them to withstand these temperatures better. However, for most common PVC compounds, these high temperatures cause the plasticisers and other additives to start migrating to the surface or volatilising, thus compromising the material’s integrity.
Extreme Heat
When subjected to temperatures above 100 °C, PVC starts to decompose and degrade through a process that includes dehydrochlorination, where hydrogen chloride gas is released, leading to the formation of a polyene structure. This can cause discolouration, loss of mechanical properties, release of toxic fumes, and more.
Above 150 °C, PVC is also prone to igniting and burning, so it is generally not suited to these types of temperatures.
However, under highly controlled circumstances, usually at temperatures of around 200 °C, PVC can become fully plasticised and ready for remoulding. Within this range, the polymer chains can be given enough mobility to allow the material to flow and be reshaped, making it ideal for recycling.
If you are looking for a company that can provide you with everything from a semi-rigid injection compound to a blow-moulding compound or a flexible extrusion compound, contact us at IPC.
