Effect of unsaturated hydroxyl-fatty acid modified nano-CaCO3 on the morphology and rheology of PP

A modified nano-calcium carbonate (R-CCR) was prepared by coating a layer of unsaturated hydroxyl-fatty acid on the surface of CCR powders using a solid state method, the latter were commercial nano-CaCO, modified with stearic acid. FTIR studies indicate that the modifier is combined on the surface of CaCO3. PP/EPDM/nanoCaCO(3) ternary composites are prepared by a melt-mixing method. SEM and TEM are utilized to examine the morphology of the composites. The tensile fractured surface of PP/EPDM/R-CCR shows a fibroid morphology and large-scale yield deformation. The impact fractured surface shows that the amount of cavities in PP/EPDM/R-CCR systems is increased and their size diminishes obviously. R-CCR particles were dispersed uniformly in PP matrix, and their compatibility was distinctly improved as compared with CCR as the amount of R-CCR was 15 phr. The tensile strength remains nearly constant (reduces from 27.6 MPa. to 27.5 MPa) while the impact strength increases from 9.6 kj/m(2) to 15.6 kj/m(2) as CCR is replaced by R-CCR. Meanwhile the flexural strength and flexural modulus are also increased correspondingly. Furthermore, the impact strength of PP/EPDM/R-CCR keeps on a high level (15.6 kJ/m(2)) which is more than the sum of that of PP/EPDM and PP/R-CCR (6.63 kJ/m(2) and 6.04 kJ/m(2) respectively). It indicates the R-CCR and EPDM has significant synergistic toughening effect on PP, keeping the strength, modulus of virgin PP as well. Both the storage modulus G' and loss modulus G" of PP/EPDM and PP/EPDM/R-CCR composites increase with increasing frequency,but the values of G' and Go of the tertiary composite are relatively in a higher level than that of the binary system. The loss factor and viscosity decrease with increasing frequency but there has little difference between tertiary and binary composites. The apparent viscosity eta of the tertiary system containing R-CCR is lower than that of tertiary system containing CCR and virgin PP. The viscosity of composite significantly decreases with increasing shear rate. The measured mechanical properties of the composites indicate that replacing of CCR by R-CCR for binary composites could simultaneously enhance the toughness and strength of PP.