ABSTRACT:The isothermal crystallization behavior of poly(trimetylene terephthalate) (PTT) containing silica nanoparticles was investigated. The addition of silica nanoparticles increased the crystallization temperature of PTT by 20 C and notably decreased the size of the crystals. Higher silica nanoparticle content led to greater depression of equilibrium melting temperature. Quiescent isothermal crystallization in DSC capsule showed that silica nanoparticles acted as a nucleating agent for PTT and decreased the half time for crystallization. In the case of PTT containing silica nanoparticles 1 and 2 wt %, however, little difference in the crystallization behavior was noticeable, suggesting that the silica content of 1 wt % is the critical level for nucleating. Isothermal crystallization under dynamic shear showed similar crystallization behavior with quiescent crystallization. In addition, higher shear rate accelerates the crystallization rate of PTT. However, X-Ray diffraction result revealed that the content of silica nanoparticles and application of shear had little effect on the resultant crystal structure. [DOI 10.1295/polymj.36.519] KEY WORDS Poly(trimethylene terephthalate) (PTT) / Nanocomposites / Crystallization / Nucleation / A variety of inorganic materials, such as glass fiber, talc, calcium carbonate, and clay minerals, have been widely used as additives or reinforcements to improve the thermal and mechanical properties of organic polymers. The key factors to enhance such properties include the size, shape, dispersion state, and interfacial adhesion of fillers in the polymer matrix. In recent years, the organic nanocomposites incorporating some nano-sized inorganic particles have attracted much attention as newly emerging materials. When compared with the conventional composites including submicron inorganic particles the nanocomposites are expected to give new and much improved properties even at the same composition.1-3 Some examples include increase of tensile modulus and strength, barrier properties, resistance to solvent, fire and heat, and optical transparency. [4][5][6] Moreover, these improvements are expected to be obtained at much lower loading levels than the submicroparticles. The desired content of 1-10 wt % for nanoparticle is comparable with that of 25-40 wt % for submicronparticles in efficiency. Recently, poly(trimethylene terephthalte) (PTT) attracts much attention among polymer processors and is being intensively investigated as engineering thermoplastics and as a matrix for fiber-reinforced composite due to its good thermal and mechanical properties. 8,9 In addition, PTT is predicted to obtain a large share in synthetic fiber market in the future because of its peculiar properties. Fumed silica nanoparticles manufactured by high-temperature hydrolysis of silicon tetrachloride in a flame has a spherical shape, extremely large surface areas, and a non-porous surface, which could promote physical contact with polymer matrix.10 Sumita et al. 11 early pointed out the benefits of re...
