Which one you have
Four resins, six
different markets
They look alike on a dock and sort into entirely different outlets. EPS and XPS share a polymer and almost nothing else commercially; so do the two polyurethanes. Identifying which is which is the first thing done, because it decides everything after it.
EPS
Expanded polystyrene
The white molded block in electronics cartons, appliance corners, coolers and insulation sheet. Beaded, light, and the most widely recycled of the foams: densified into blocks or ingots and sold back into picture frame molding, rigid sheet and new insulation. Heavy food residue or dirt is the usual reason a load is turned away.
XPS
Extruded polystyrene
The colored insulation board on construction sites — denser and smoother than EPS, same resin underneath. It densifies the same way, but it arrives cut, laminated or glued to something else, which makes the sorting rather than the processing the work. Board from older buildings may carry a brominated flame retardant that some processors will not accept, so acceptance is settled before the load moves.
EPE
Expanded polyethylene
Soft, flexible, slightly rubbery — the protective sheet, pouches and corner padding wrapped around finished goods. Densified and pelletized back into film and molded goods. Tape, labels and mixed resins are the problem here, because they survive into the melt.
EPP
Expanded polypropylene
Tough and springy, used for automotive components, returnable dunnage and protective packaging that has to survive a few trips. Worth checking for reuse before recycling for exactly that reason. Recycled by densification and reprocessing where the feedstock is consistent enough.
PU — flexible
Flexible polyurethane
Cushioning, seating, mattress and furniture foam, and the trim scrap from making any of it. This one has a genuine, established market: ground and bonded into carpet cushion. Roughly 85 percent of carpet cushion sold in the United States is rebond made from recycled foam, and virtually all post-industrial trim scrap goes into it.
PU — rigid
Rigid polyurethane
Insulation panels, sandwich board and spray foam offcuts. The hardest of the group, because it is a thermoset and cannot be remelted. Realistic routes are size reduction into filler and oil absorbents, briquetting to make transport viable, and energy recovery where a facility takes it. Older material may contain legacy blowing agents, which is an acceptance question rather than a disposal one.