Flexible PVC has to perform while it is being extruded and after it becomes a finished profile, tube, hose or gasket. Formulation affects how the material responds to heat, shear and flow, while also shaping the physical properties required in use. Understanding that relationship helps manufacturers assess flexible PVC extrusion as a material-engineering process.
The formulation of a flexible PVC compound affects its behaviour during extrusion and the properties of the finished product. The composition of the pellets affects how the material responds when heated and forced through a die, as well as the properties it retains after cooling.
At Innovative PVC, we manufacture flexible compounds for extrusion applications, so the material has to suit both stages of that journey.
Material Behaviour During Extrusion
PVC does not behave like a simple liquid once heat and shear are applied. Flexible PVC is viscoelastic and its resistance to flow changes under processing conditions. Research into plasticised PVC has demonstrated shear-thinning behaviour: as shear rate increases, apparent viscosity decreases. The same research found that increasing plasticiser content reduced viscosity.
That is an important manufacturing consideration because plasticisers influence flexibility as well as processing behaviour. A flexible extrusion compound therefore needs a formulation suited to the physical properties required from the finished product and the extrusion process used to manufacture it.
How Flexible PVC Flows Through the Die
The material continues responding to processing forces as it passes through and leaves the die. PVC research has shown that molecular weight, temperature and shear rate can influence die swell, where material expands after leaving the die. This occurs because polymer melts have an elastic response rather than behaving as purely viscous liquids.
The practical point is that PVC extrusion materials bring their own rheological behaviour into the manufacturing process. Formulation and processing conditions interact, which is why two flexible compounds should not be assumed to behave identically simply because they have similar hardness.
PVC Extrusion Applications
The demands placed on the compound also change with the product being extruded. Our flexible PVC compounds can be formulated for characteristics including chemical resistance, UV stability, colour and physical performance. Different PVC extrusion applications can therefore emphasise different requirements:
- Garden hoses may require flexibility, UV stability and durability for outdoor exposure.
- Industrial hoses and tubing may require chemical resistance for their intended environment.
- Gaskets and seals need physical properties appropriate to their function.
- Furniture or automotive profiles may require particular surface finishes, colours and resistance to their service conditions.
From Pellets to Finished Performance
Cooling does not make the material requirements disappear. The properties engineered into the compound still have to support the hose, gasket, tube or profile throughout its intended use.
This is where extrusion performance and finished-product performance meet. Selecting the right PVC compound for the manufacturing process means considering what happens to the material under heat, pressure and shear, alongside what it must do once extrusion is complete. Surface quality can also depend on that balance. Flexible PVC extrusion is therefore a material-engineering question across the manufacturing process, not simply a choice of how soft the PVC needs to be.
Flexible PVC extrusion performance starts with a compound suited to both the manufacturing process and the finished product. Discuss your flexible PVC extrusion requirements with Innovative PVC to find the right formulation for your application.
FAQs
What is flexible PVC extrusion?
Flexible PVC extrusion is a manufacturing process in which a flexible PVC compound is heated and forced through a die to create a continuous product such as tubing, hose, seals or profiles.
What affects the behaviour of flexible PVC during extrusion?
Compound formulation and processing conditions both affect extrusion behaviour. Factors such as plasticiser content, temperature and shear can influence how the material flows during processing.
What products can flexible PVC extrusion be used for?
PVC extrusion applications can include hoses, tubing, gaskets, seals and flexible profiles. The compound formulation needs to suit the manufacturing process and the performance requirements of the finished product.
How do I choose a flexible extrusion compound?
Consider both the extrusion process and the conditions the finished product will face. Required flexibility, exposure conditions, chemical resistance, colour and other physical properties can all influence compound selection.
