Extrusion Foaming of Poly (lactic acid)/Soy Protein Concentrate Blends

Poly(lactic acid) (PLA) and soy protein concentrate (SPC) were compounded using poly(2-ethyl-2-oxazoline) as compatibilizer by twin-screw extrusion, and the resulting blends were foamed by a chemical blowing agent (CBA) using the same extruder. Effects of foaming temperature and CBA content on cell density and foam density were investigated. Polymeric methylene diphenyl diisocyanate (pMDI) as a co-compatibilizer was added prior to foaming extrusion and its effects on foam morphology and properties were also studied. The results showed that cell density and foam density were greatly influenced by foaming temperature and CBA content. Using the strong interfacial modifier pMDI in PLA/SPC blends resulted in high-cell density and low-foam density when CBA concentration was low.