Construction / Aluminium Sandwich Panels

Aluminium Sandwich Panels

Mineral fillers are being used in cladding panels, specifically in  Alumimium Sandwich Panels to make these more flame-retardant and to make sure the building can meet certain Safety-codes.

ACP is an Aluminium composite Panel also known as ACM Aluminium Composite Material. This is a sandwich panel of two aluminium skins bonded to an extruded core of mineral filled Polyethylene or Polypropylene core.

For the ACP’s that meet fire resistance requirements (Class B1 or A2), the polymer core typically is filled with inorganic flame retardant fillers like ATH (= Aluminium-Tri-Hydroxide) when polymer core processing temperatures are < 200 dC or MDH (= Magnesium-Di-hydroxide) when polymer core(processing temperatures > 200 dC).

For Class B1 typically a mineral FR-loading level of 50 to 60% is sufficient to reach the desired fire performance. These ATH-based Portaflame SG grades are suitable for this application because of:

  • Good FR performance: consist of 99.5% ATH; endothermic H2O release at 200 dC
  • Easy of processing: low moisture; high bulk density; flow- / dosing characteristics; non-abrasive
  • Neutral white colour
  • Economic
  • Non Toxic 

To reach Class A2 is quite a challenge within the industry, especially related to the desired calorific value of the composite material (max. 3 MJ/kg). Considering for example that the calorific value of pure PE is approx. 46 MJ/kg indicates that polymer/binder-level of the composite should be less than  10%. It is clear that extrudability of such a material will be problematic.

Considerations:

  • Choosing a polymer with lower calorific value
  • ATH and MDH offer a negative contribution to the calorific value of approx. -1.3 MJ/kg
  • Optimisation of the packing properties of the filler will help increasing the loading level.The formulator can choose, for example, bimodal or trimodal mixtures combining ATH and/or other minerals (quartz, dolomite, calcium cabronate, feldspar,…).