In case of physical foaming, the gas dosing station injects the gas (propellant) into the extruder under high pressure via an injection valve. The gas quantity can be adjusted directly and adapted to the polymer and the foam density to be achieved.
At the tool outlet, a sudden, large pressure drop leads to a supersaturation of the melts with the propellant. The gas is again released from the polymer and thus forms a consistent, microcellular foam structure.
As well as the low raw material consumption, the significant characteristics of this production process are positive product properties, such as low density, exceptional heat and sound insulation, mechanical damping, low levels of water vapor permeability and reduced moisture absorption.
Further advantages are a homogeneous foam structure, very good process stability and low propellant costs.
The MAXIMATOR DSD 500 Gasdosing Station compresses the gas with air driven Maximator gas booster to pressures up to 500 bar and doses very uniformly, also in case of severe back-pressure fluctuation, through an innovative mass-flow regulation concept and the highly-dynamic Maximator 3/3-way proportional pressure control valve.
The gas volume is measured on the pressure side. The mass-flow regulation is insensitive to temperature and adapts optimally to pressure variations with constant dosing quantity.
The measured values are visualized. Because of the precise injection flow regulation, production fluctuations under the same product, material and process conditions can be reduced.
For dosing of combustible gases such as propane / butane Maximator has developed a version of the DSD500, which can be used in conformity with the explosion protection directive 94/9 EC in hazardous areas.
Especially for the dosing of CO2 in drying processes in the food industry the stainless steel version of the DSD500 is designed.