Polyamide 66 and thermal break

Polyamide and thermal break are two concepts that usually go hand in hand in the construction sector. They are related to the filtrations of our house through the windows and other elements. How to avoid leaks by breaking the transmission of heat or cold is the role played by polyamides.

However, the truth is that we are actually much more familiar with polyamides and thermal breaks than we think.

For example, the mechanism of a pan is a clear example of thermal break. And polyamides are a common compound in our wardrobe.

In this post we will learn about the relationship between synthetic polyamide and thermal break in the engineering and construction sectors

Polyamide = polymers + amides

Chemically speaking, a polyamide is a polymer, i.e. a substance composed by the union of monomers with amide-type bonds. We can find polyamides in nature, as in the case of silk or wool, or in synthetic form, as in Kevlar or nylon.

Due to its mechanical and thermal properties, polyamide is widely used in industry, which also uses its volumetric resistivity and insulating capacity to create all types of parts.

Among its advantages we find:

  • High thermal stability
  • Wear and corrosion resistance
  • Mechanical damping
  • Sliding properties
  • Chemical resistance
  • High resistance to deformation with heat
  • Simple mechanization

To these characteristics we must add that this type of polymer can be mixed with other materials, thus obtaining reinforced polyamides with special properties for different types of use such as, for example, thermal break.

Synthetic polyamides origin

For 10 years, research on polymerisation was carried out by the chemical company DuPont Corporation, with the help of the chemist Wallace Hume Carothers, who had left his post as a professor at Harvard to lead the company’s chemistry department from 1927.

After three years of painstaking research, in 1930 the Carothers team introduced its first product after isolating chloroprene, a liquid that, when polymerised, became the synthetic rubber we know as neoprene.

After shifting the focus of his research towards finding compounds for use in industry, the 6-6 polymer, known as nylon, was produced in 1935 and would not be released until 1938.

Further research and development has led to the identification of different types of nylon with numbers, such as polyamide 6, 12, 46 or 66, which is the most commonly used for thermal break.

Wallace Hume Carothers

When the Nylons Bloom Again , and a war history

Synthetic polyamides, led by nylon, came onto the US market with the clear intention of displacing another polyamide, natural silk, and were marketed as stockings.

Its success was such that in a few days more than 4,000,000 pairs were sold. Nylon stockings offered everything that silk stockings could not: they were aesthetic, resistant and more economical.

With the promise of a product as hard as steel and as fine as a spider’s web, nylon stockings promised to save their buyers a great deal of money on silk stockings.

But soon the setback came, and the nylon stockings disappeared. DuPont, in 1940, had to redirect its production to war material for the American troops who had just entered World War II.

Stockings were no longer seen in shops, and nylon was used in the manufacture of ropes, parachutes, tyres etc. To be able to buy them you had to go to the black market and to the street vendors, who multiplied their price.

At the end of the war, demand was at its peak and, in fact, exceeded Dupont’s production capacity. The company could not supply enough units to meet demand until 1946.

For months, thousands of shoppers wiped out stocks of nylon stockings, caused riots and fights, and organized massive queues to try and buy a pair of stockings that never arrived. These were known as “Nylon Riots”.

Women during the nylon riots

Polyamides in the industry

In industry, polyamides are manufactured as semi-finished products in different formats and functionalities, the most common being extruded polyamide 6 and polyamide 66.

Their numerous properties mean that polyamides replace metal in various applications, with the aim of breaking the thermal bridge. In this way, we can find polymers in the automotive industry, heavy industry, etc. For example, in:

  • Sprockets
  • Spacers
  • Nuts and bolts
  • Knobs
  • Sliding blocks
  • Sprockets
  • Buttons

Thermal bridge, heat transmission

But talking of polyamides and not go into detail about one of their main functions, and even more so within the aluminium industry, which is thermal breakage, would be to leave out one of the most interesting aspects of polymers.

What is a thermal bridge?

Within the construction, a thermal bridge is an area of the enclosure through which heat is easily transmitted. For example, an aluminium window, because it is a conductive metal.

Poor thermal insulation can result in heat losses of between 10% and 20%, which is a very high energy efficiency loss for a home that wants to be kept warm or cool.

Today, building regulations, techniques and new materials make it necessary to take care of the insulation and energy use of new buildings, as well as in renovations.

The most common thermal bridges in an enclosure are found in:

  • Windows and doors
  • Openings and roof lights
  • Slab fronts
  • Meetings between materials and parts of the house
  • Enclosures in contact with the ground

Two concepts that we must understand in order to understand thermal bridges are thermal conductivity and thermal transmittance. We talk about both concepts in our post about thermal insulation.

polyamide and thermal break

Thermal conductivity

Thermal conductivity measures the heat conduction capacity, i.e. the transfer of energy in the form of heat by conduction between two bodies. Among the most common materials, the usual conductivity is between 0.03 and 0.05 W/mK

Thermal transmittance

Thermal transmittance, on the other hand, refers to the measurement of heat flowing per unit of time and surface. This means that this value reflects the capacity of a material to transmit heat. The international unit of measurement is W/m2K. A low value will mean better performance from an insulator.

How to break the thermal bridge

To prevent heat leakage through the thermal bridges, non-conductive materials are introduced to break the temperature transmission.

It is the same principle that we can see in everyday objects such as frying pans or cake handles. A badly conductive material is introduced so that the temperature does not continue its advance.

In the case of aluminium windows, although double glazing already acts as insulation, it is advisable to use polyamide profiles to break the thermal bridge and thus prevent leaks and condensation.

Polyamide 66

Polyamide 66, with a 25% glass fibre reinforcement, is the most commonly used for thermal bridge breaking. Its use is included in the European regulation UNE-EN14024, which corroborates its effectiveness.

Polyamide 66 is a semi-crystalline polymer (25% glass fibre) with good mechanical and chemical resistance properties, due to the uniform packing of the molecules in the crystalline region.

This polyamide absorbs the water contained in the humidity of the environment. As the water content within the polymer matrix increases, there is a dimensional increase and changes in the mechanical properties of the polymer.

Its main qualities are:

  • Resistant to corrosion and most chemicals.
  • The residues from its calcination are not toxic and are not harmful to the environment.
  • Recyclable.
  • Physically tested after being used in carpentry systems for the last 3 decades.
  • Low thermal conductivity coefficient.
  • Thermal expansion coefficient close to that of aluminium.
  • Melting point higher than the temperatures of the lacquering oven.
  • Good resistance properties, even up to temperatures of 200° C.
  • Resistant to impact and ageing.
  • Resistant to UV radiation due to its carbon black content and the intrinsic properties of the polymer and processing method.
polyamide and thermal break