Heat Resistance of CPVC

Heat Resistance in CPVC Compounds and Resins

Posted by TempRite® Engineered Materials North America Team on 12/20/2020

TempRite® Engineered Materials’ CPVC compounds offer higher heat resistance than traditional PVC materials that allows product engineers to push the limits of what their products can do. Compounds produced from TempRite CPVC can be applied in indoor and outdoor environments where other plastics become susceptible to degradation.

Heat-related strengths

These are just some of CPVC’s inherent heat-related strengths:

  • Higher softening temperature
  • Flame and smoke performance
  • Chemical resistance to strong acids and bases
  • Thermoformability
  • Impact resistance
  • Versatility

How TempRite® CPVC achieves Heat Resistance

The CPVC polymer is produced through post-chlorination of PVC. The additional chlorine atoms occupy a much larger area of the materials’ carbon backbone, stiffening the molecule and giving it a much higher softening temperature.

The bulky chlorine atoms also serve to protect the carbon chain of the polymer from oxidative attack and stabilize it against chain cleavage reaction.

Thermal properties of thermoplastics
The molecular structure of PVC vs CPVC. Grey atoms represent the carbon chain, blue atoms represent hydrogen and the red atoms represent chlorine, acting as a layer of armour to the carbon chain.

Due to this inherent strength and stability in the polymer itself, any resulting compound starts off strong, with many heat-related advantages at the outset.

Versatility of Heat Resistance

Because CPVC is made with a post-chlorination reaction, TempRite Engineered Materials can produce CPVC compounds with various levels of chlorine content and molecular weight. This allows for significant versatility in terms of heat resistance. The inherent heat resistance in CPVC can therefore be scaled up or scaled-down. However, the higher the molecular weight and chlorine content, the harder CPVC is to process.

CPVC compounds are rarely processed without additives. Typically, a CPVC compound consists of 85% resin and 15% additives - this 15% can either boost or limit CPVC’s inherent strengths depending on the needs of the application.

Typical CPVC additives include:

  • Stabilizers
  • Antioxidants
  • Impact modifiers
  • Processing aids
  • Lubricants
  • Pigments

For product designers, the scalability of CPVC’s heat resistant qualities offers a new level of versatility in manufacturing. This gives engineers the technical and financial advantage in the creation of new products.

Applying CPVC Outdoors

It is often assumed that thermoplastics cannot withstand harsh outdoor environments, where temperatures can soar to exceptionally high levels in the summer and UV rays generate destructive free radicals. However, TempRite CPVC’s UV resistance is inherent. You would not be able to produce CPVC polymers without it.

In the same way CPVC’s molecular structure is built to withstand heat-related incidents such as oxidation, CPVC’s UV resistance also protects against free radicals. Typically, UV splits molecules to make free radicals which can cause adverse reactions such as chain cleavage. CPVC has exceptional resistance to this well known form of plastic degradation. CPVC is actually produced in an environment of intense UV light and free radicals without any significant reduction in its molecular weight.

This enables manufacturers to rethink where plastic can be applied cost-effectively, where end users typically rely on wood, stone, metal or composite materials. For example, outdoor fencing and cladding can be produced in CPVC, with the aesthetic of natural wood or metal.

Temperature Limits for CPVC Applications

Amorphous polymers, such as PVC and CPVC have a high glass transition temperature (the temperature range in which a polymer changes from rigid to flexible). However as temperature decreases, CPVC retains its strength.

Semicrystalline polymers such as PPR and PVDF can only be used above their glass transition temperature, providing less versatility. As a result, CPVC is being used in outdoor applications where temperatures reach far below freezing.

Thermal properties of thermoplastics
Thermal properties of thermoplastics. (Tg = Glass Transition Temperature,Tm = melt temperature)

Compared to these other materials, TempRite CPVC compounds provide mid-range thermal performance. With higher heat resistance than PVC and a lower maximum temperature than PVDF can extend high temperature performance without adding excessive cost.

Compared to polypropylene, TempRite CPVC offers dimensional stability at higher temperatures while remaining viable as temperatures drop below freezing.

Heat Resistance in Product Development

TempRite CPVC compounds can perform effectively in a wide array of products:

Exterior Profile Extrusion - CPVC panels, railings, siding, gutters and other profiles with an embossed or gloss finish on the outside provides designers with flexibility whilst losing none of the polymer’s core benefits.

Molded Fenestration Components – CPVC molded spacers, brackets and other components for windows and doors ensure dimensional stability in both dark color applications and for internal components subjected to elevated temperatures due to the greenhouse effect.

Other Custom Products – High heat applications can arise in a wide array of markets and products including electrical products, credit cards, ventilation systems, pool & spa, water heaters and many others. In any application where thermal dimensional stability prevents the use of PVC, TempRite CPVC solutions could provide a viable, cost-effective solution.

Whatever your application, designers can fully develop a finished product with heat resistant qualities from the outset, without losing any aesthetic benefits. TempRite CPVC can create ordinary products that perform to an extraordinary level.

Contact us to speak with a TempRite Engineered Materials expert for further information about how TempRite CPVC compounds can be a fit for your products.

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