Flame and Smoke Performance of TempRite® Engineered Materials’ CPVC

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

When making products that require listings for flame and smoke performance, many manufacturers may feel like their only option is to add expensive flame and smoke additives to traditional, low-performance materials.

These manufacturers may be surprised to learn that TempRite® CPVC can offer a cost-effective solution for these applications without the need for additional, costly additives. Because of the unique properties of TempRite® Engineered Materials’ CPVC our products are not only able to resist fire, but they are actually self-extinguishing.

In addition to this, product engineers can expect the following benefits from TempRite CPVC materials:

  • Higher Flash Ignition Softening Temperature
  • Lower Smoke Density
  • Better Flame Retardancy
  • Low Thermal Conductivity

Limiting Oxygen Index

TempRite CPVC’s ability to burn under ordinary atmospheric conditions is very limited. It has a very high Limiting Oxygen Index (LOI) of 60, meaning there would have to be 60% oxygen in the air for CPVC to burn.

Earth’s atmosphere contains 21% oxygen. The only way Lubrizol CPVC can burn at normal atmospheric conditions is if an external flame is constantly applied. Furthermore, burning will cease as soon as the flame is removed.

Many other plastics commonly used in manufacturing have an LOI lower than 21, meaning that they easily ignite and continue to burn under normal atmospheric conditions:. 

Limiting Oxygen Indexes of various materials
Limiting Oxygen Index (LOI) of Polymers. Materials below red line are susceptible to combustion under normal atmospheric conditions (21% Oxygen)

Flash Ignition Temperature

A powerful indicator of a material’s resistance to fire is its Flash Ignition Temperature; the moment enough volatiles are reacting with free radicals to cause a fire (Flash ignition is when things finally catch fire.) This is the moment a material is hot enough to cause the material to break down and release volatiles into the air.

In the case of CPVC, Flash Ignition Temperature is very different from its rivals:

Material °C °F
CPVC 482 900
PVC, Rigid 399 750
Polyethylene 343 650
Paper 232 450
Wite Pine 204 400

What Happens when CPVC is Exposed to Fire

One of the principal dangers of polymers when exposed to flames is the formation of burning drips. These can spread a fire from one area to another.

TempRite CPVC, when exposed to fire forms a charred layer, thanks to the rapid crosslinking process taking place from within the polymer. This barrier does not break away from the material; it spreads to create a layer of protection, maintaining the integrity of the material within.

Flaming drips vs char formed across CPVC

If CPVC is exposed to fire, combustion does happen, however it protects itself during the process without producing burning drips, and it self-extinguishes when the source of the fire is removed.

This adds a new layer of protection to the development of fire protection materials, or the manufacture of products intended for use in hazardous environments.

CPVC and Smoke Toxicity

A common question around plastics and combustion is what dangerous byproducts are produced when they burn.

TempRite CPVC’s smoke propagation is naturally low due to its molecular structure. The irregular chlorine structure limits the zipper dehydrochlorination process, making it slower. It forms a stronger char barrier and produces less volatiles, producing less smoke as a result.

Combustion Cycle of CPVC - Illustration
The slower dehydrochlorination process of CPVC, resulting in lower smoke propagation

Pyrolysis products are released, as in all combustion, but not as dangerously as typical smoke.

All smoke is toxic to a degree; even products that “burn cleaner” (such as a domestic scented candle) release pyrolysis products into the atmosphere. 3rd party laboratory testing has shown that the smoke generated from burning TempRite CPVC is no more toxic than burning wood from a Douglas Fir tree. This combination of very limited smoke production and relatively low smoke toxicity is another advantage for product designers who work in hazardous environments.

Flame and Smoke Ratings

TempRite CPVC has been evaluated to a wide array of flame and smoke tests and we have products that meet the following ratings:

Test Protocol Performance Range
UL 94 V-0, 5Va
ASTM E84 – Flame Spread <15
ASTM E84 – Smoke Developed Index <50*
UL 746A – Hot Wire Ignition plc 1
UL 746A – High Amp Ignition plc 0
EN ISO 13501 B s1 d0 

*Application Dependent

Applying CPVC’s Fire Resistance in Manufacturing

TempRite CPVC can be applied both in neat compounds and in resin blends with PVC or EVA materials to improve the flame and smoke performance of existing technologies. Our natural resistance against the development, spread and toxicity of fire provides exciting new opportunities in product development:

  • Construction products and cladding
  • Electrical profiles
  • Industrial component manufacturing
  • Hot-Melt Adhesives
  • Wire & Cable
  • Other flexible (plasticized) vinyl applications

Let our experts help you find the best way to make the most of TempRite CPVC’s excellent fire and smoke resistant qualities in your next product development.