The effect of incorporation of calcium carbonate (CaCO3) on degradation of mechanical properties of a cured unsaturated polyester resin (UP)-CaCO3 system in boiling water has been studied. The results showed that the incorporation of CaCO3 increased remarkably the retention of flexural strength but decreased the retention of flexural modulus of the above system under the soaking condition in boiling water, while the incorporation of CaCO3 decreased the initial flexural strength but increased

more »

... arkably the initial flexural modulus of the system. A mechanism of the degradation in boiling water was proposed that the decrease of flexural strength was mainly due to the degradation of UP component and that of flexural modulus was due to absorption of water into the interface between UP and CaCO3. Accordingly, the increase of CaCO3 content which caused dilution of UP content increased the retention of flexural strength but decreased the retention of flexural modulus due to the increase of the interface between CaCO3 and UP.