Effect of calcium carbonate particle size and surface pretreatment on polyurethane composite Part 2 - phase behaviour

摘要

The investigation of ultimate phase structure and morphology of the PU/CaCO_3 composites indicates higher influence of nanofillers than microfillers on the crystallisation processes in the PU matrix. The Lorentz corrected SAXS curves clearly show the decrease of intensity of the first intensive peak (S_1 = 0.057 nm~(-1)) with the addition of microfiller. At the same time the first peak could be only slight recognised after the incorporation of all grades of nanofiller even with the smallest amounts of filler. Obviously, the CaCO_3 nanofiller affects domain/grain restructurisation of the PU matrix much stronger than the CaCO_3 microfiller. These results are in good accordance with lower tensile strength and weaker interactions in the composites with microfiller than in the composites with nanofiller. The increased interactions at the interphases in nanocomposites lead to stronger structural change in the PU nanocomposites and to increased tensile strength regardless of the noticed problem of the nanofiller's agglomeration. The WAXD investigations proved that the presence of nanofiller in the PU composites affects the nucleation and crystal growth of polyester segment domains. The conclusion is that the nanoparticles of CaCO_3 filler are situated preferably in soft segment domains of PU and decrease the crystallite size of polyester domains. This could be the consequence of preferable/stronger interactions of the nanoparticles with polyesters segments than with polyether segments in the PU matrix.