Abstract: Poly ether ether ketone(PEEK)-CaCO₃ composites were prepared on a twin screw extruder with different mass ratios of CaCO₃ to PEEK from 0 to 25%. The influence of surface treatment of the particles(with or without SPEEK) on the mechanical and thermal properties of the composites was studied. The experiments included tensile tests, flexural tests, notched Izod impact tests, differential scanning calorimetry(DSC), and scanning electron microscopy. The modulus and tensile strength of the composites increased at the same filler content compared with the system in which CaCO₃ particles were not treated, and with a content up to 10% the tensile strength was higher than that of the neat PEEK. This increase was connected to the bonding between the particles and the PEEK matrix, as can be proved by the SEM picture of the cryogenic fracture surface of the composites. The impact resistance showed large improvement with the increase of particle content up to 15%. This was mainly due to the improved dispersion of the filler particles and the strong interaction between and the fillers and the matrix. DSC experiments showed that the glass transition temperature(T_g) and melting temperature(T_m) were influenced by the content and surface properties of the filler particles. The T_g increased with increasing the content of fillers while T_m decreased. Further, the melting enthalpy of the composites was found to decrease with increasing CaCO₃ loadings, but the melting enthalpy and crystalline degree of the PEEK matrix was not sensitive to the content and the surface properties of the CaCO₃ particles. In this study the fillers treated with SPEEK were found to give better combination properties, which indicated that SPEEK was a good coupling agent in the CaCO₃/PEEK composites.

Key words: PEEK, CaCO₃, Surface modification, Coupling agent