Polyester Acoustic Foam
Polyester foam grades are often used for acoustic applications as the cell structure is very regular making it a good foam to use for acoustic applications, In fact many of the polyester acoustic foam products you see today originally came from foam polyester foam grades made for the automotive industry where sound absorption was a key factor in the foams formulation.
A little more about Polyester Foam
Polyester foam was the very first foam to be produced and manufactured commercially.
It’s younger brother, polyether foam, became the better known of the two main foam types from the polyurethane foam family, a question often asked today is when is the right time to consider using polyester foam rather than polyether foam ?
The main feature of polyester foam it natrually has a very regular cell structure, and with a high proportion of closed cell windows which glisten in the light, it has the better aesthetics of the two foam types. Alongside its more stable resistance to phenolic yellowing. Which is a colour degridation caused by polutants in the atmosphere reacting with the foams anti oxidents. Polyester foam is a natural choice for presentation packaging and case inserts. Most frequently in this application polyester foam will be charcoal grey in colour, and in addition to the many shaping options available, it can be supplied in convoluted or egg-box profile.
That high proportion of closed cell windows also means that polyester foam is more suited to environments where sealing and low air permeability are required, for example as a sealing gasket.
It’s the higher tensile strength of polyester foam in applications where tear strength is important which sets it apart from polyether foam. Where polyether foam has a poorer tear strength and can rip more easily, it can also be flame bonded to fabrics and is often used for the headlinings of cars and on ironing boards etc.
It’s that regular cell structure in polyester foam which lends itself to the reticulation process, which renders the foam block completely open cell. The open cell reticulated polyester foam is available in a range of tightly controlled cell sizes, and makes an ideal air filtration media. Cell sizes are available in a range from 2 to 110 PPI (Pores Per Inch).
Moreover, reticulated polyester foam can be compressed into predetermined sheet thicknesses. This process is known as felting. Felted foam has a highly controlled cell structure and is typically used for reservoiring and metering liquids and fine powders.
Not all Polyester foam is good for acoustics
As you can see polyester foam can have a very closed cell content as used in packaging foam applications and an overly porous reticulated cell structure as used for filtration. so again to ensure the polyether acoustic foam grade you are getting is suited to acoustic applications you must again check for the NRC ( noise reduction coeffecient) properties of the foam to see how it performs for acoustic sound absorption, it would be quite easy to pass off some packaging polyester foam grades as acoustic foam, expecially as many packaging foams are ran through a convoluter ( the machine that splits foam sheets into the eggbox design that many acoustic tiles are made like ).
Also be careful with the fire retardency on polyester foam it is often very low or non existent. be sure to check it is suiotable for the environment in which you are intending to use it.