Mechanical properties of polyurethane foams prepared from liquefied corn stover with PAPI.

Corn stover was liquefied by using ethylene carbonate (EC) as liquefying solvent and 97% sulfur acid as catalyst at 170 degrees C for 90 min. Polyurethane (PU) foams were prepared from liquefied corn stover (LCS) with variable amount of polymethylene polyphenylisocyanate (PAPI) by one-shot method, with water as blowing agent, silicone as surfactant and triethylamine and dibutyltine dilaurate as co-catalyst. The mechanical properties of LCS-PU foam with different [NCO]/[OH] ratio were studied on a universal tensile tester. With the increase of [NCO]/[OH] ratio from 0.4 to 1.0, the tensile strength and Young's modulus of the LCS-PU foam first raised, reached their maximum values at [NCO]/[OH] ratio of 0.8, and then declined; while the elongation at break decreased from 117% to 3.6%. The results indicated that by changing the [NCO]/[OH] ratio, mechanical properties of LCS-PU foams could be adjusted for various end uses.