Abstract: Polypropylene carbonate (PPC) was chemically modified by use of diphenylmethane diisocyanate (MDI) as a chain extender in an internal mixer, and then the thermal performance, mechanical behavior and barrier behavior of the modified PPC were investigated by means of elemental analysis, differential scanning calorimetry, universal material testing machine, gas permeability tester, water vapor permeability tester and other instruments. The results indicated that the glass transition temperature (Tg), mechanical properties, and O2, CO2 and H2O barrier properties of PPC were enhanced due to the chemical modification. Tg of PPC was increased from 30.37 ℃ to 33.48 ℃ in the presence of 5 % MDI, and meanwhile, the tensile strength was improved from 20.9 MPa to 49.0 MPa. Moreover O2 permeability of PPC decreased from 15.8×10^-5 cm3/m2d·Pa to 5.8×10^-5 cm3/m2d·Pa, CO2 permeability decreased from 38.6×10^-5 cm3/m2d·Pa to 15.0×10^-5 cm3/m2d·Pa, and water vapor transmission rate decreased from 23.7 g/m2·d to 10.3 g/m2·d.

Key words: propylene carbonate, diphenylmethane diisocyanate, chain extension, modification, barrier