Hey Paul,
I have also been looking into the possibilities of suppressing the noise emission, because I recently had to consider whether to set up and test the Onefinity CNC during the remaining time that I still live in this apartment building. For the neighbors, it is not so much the direct sound that is generated in the room by the air (and which can be well shielded with an enclosure with sound insulation panels) that is disturbing, but the structure-borne sound that is spread into the building by the machine base and its feet. Against this, I have considered separating the machine base, to which the Onefinity is bolted, from the substructure, which stands on the floor, with a thick sheet of very dense rigid PU foam between the two. I have some of that around, and it already reliably decouples my speaker cabinets and an air purifier from their base.
By the way you know that polystyrene is highly inflammable.
Fire hazards
Like other organic compounds, polystyrene is flammable. Polystyrene is classified according to DIN4102 as a “B3” product, meaning highly inflammable or “Easily Ignited.” As a consequence, although it is an efficient insulator at low temperatures, its use is prohibited in any exposed installations in building construction if the material is not flame-retardant.[citation needed] It must be concealed behind drywall, sheet metal, or concrete.[117] Foamed polystyrene plastic materials have been accidentally ignited and caused huge fires and losses of life, for example at the Düsseldorf International Airport and in the Channel Tunnel (where polystyrene was inside a railway carriage that caught fire).[118]
Source: Polystyrene #Fire_hazards – Wikipedia
Reaction to fire
Polystyrene burns with a bright yellow, heavily sooting flame. The styrene released in the process has a flowery-sweet odor; in practice, however, the vapors often have a pungent odor due to additives.
The fire behavior of expanded polystyrene is dominated by the fact that it softens at temperatures just above 100 °C and then drips off, whereby the droplets (also due to the low mass and the associated poor heat dissipation) can catch fire and then drip off while burning. Above about 300 °C, the material decomposes into styrene, among other things (flash point of about 31 °C). Residues of the propellant pentane (flash point approx. −50 °C) may also be released. This can lead to the polystyrene burning off and dripping off on its own. [18] Flaming droplets of polystyrene can spread fire by igniting underlying materials.
The flammability of (expanded or extruded) polystyrene can be reduced by using suitable flame retardants . In the past, polybrominated diphenyl ethers or hexabromocyclododecane were often used as additives , the use of which in the raw material is no longer permitted, but can still be introduced into the end products through recyclate. Today, a brominated styrene-butadiene copolymer is mostly used. During combustion, these flame retardants split off gases containing bromine , thereby breaking the radical chain reactions by scavenging the oxygenand thus inhibit combustion; this can result in polybrominated dibenzodioxins and dibenzofurans .
The reaction to fire of flame retardant polystyrene foam for building applications is classified according to EN 13501-1 and classified in the European reaction to fire class E. When installed, the fire behavior depends on the specific structure of the insulation system. For information on the fire behavior of thermal insulation composite systems and controversies following media reports about facade fires, see Thermal insulation composite system#Fire behavior .
– Source: Polystyrol #Brandverhalten – Wikipedia (DE) → autotranslated