The compatibility of the hydroxypropyl cellulose (HPC) with maleic acid-vinyl acetate copolymer in the solid state was studied by thermogravimetry, thermo-optical analysis, differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR), and optical microscopy. It was established that physical interactions are prevalent in blends with a high content of HPC, whereas chemical interactions predominate in blends with a medium and low content of HPC. By increasing the temperature, the thermochemical reactions are favored. Thermal properties are dependent on the mixing ratio of the components. (C) 2003 Wiley Periodicals, Inc.