Material used is 100% up to the builder. Some considerations for choosing material are:
-Tools needed
-Experience
-Cost
-Weight
Here is the best breakdown I an give you of materials I have used and hopefully it answers any questions you may still have.
Foam core: Is a cheap material available at any art supply store. Easy to cut with an exacto knife and can be glued using epoxy, super glue, hot glue, etc… Very user friendly.
Cons to using foam core is the finish work. Filling and patch work is a must with gaps, and making a smooth surface. Exposed edges (side edge of material) will also need to be filled to accept paint. Foam core is not as durable or strong as other materials.
Styrene: Can be found at many hobby shops in sheets, shapes, and different sizes. Styrene is scored and snapped with an exacto knife giving a nice clean edge (I use .080 thickness on pack builds). Styrene can be joined by using various plastic cements, styrene solvents (I use Plastruct weldene), or super glue. Some minor filling may be needed but, unlike foam core, the overall project can be sanded. Generally styrene gives the “cleanest” looking build when done correctly. Styrene is VERY durable and forms a strong bond when done proper.
Cons can include the cost of material compared to foam core as well as the length of time it may take to glue parts together.
If you have power tools (i.e. saws, etc…) there are other materials to work with. Wood and some denser versions of foam core are a possibility.
From a kitchen table type build point of view I would suggest the foam core or styrene. It is up to you on would fits your price range and building experience.
You can also mix materials. Foam core’s thicnkness can be easier to build the outer housing of the trap if you don’t have the time to stack or hollow build the .25" thick outer walls of the housing. Where as styrene would be a perfect material for making the cartridge, diplay, battery box, etc…
I have done nearly all my trap builds in styrene and I have always been happy with the overall look it gives when finished.