The Structure And Properties Of Polyphenylene Sulfide Composites

Poly(phenylene sulfide) composites, such as poly(phenylene sulfide)/ferrosoferric oxide magnetic composite (PPS/Fe₃O₄), poly(phenylene sulfide)/low-melting-point metal composite (PPS/LMPM), poly(phenylene sulfide)/carbon nanotubes composite (PPS/CNTs) and clay reinforced poly(phenylene sulfide)/poly (butylene terephthalate) blend (PPS/PBT/clay) were prepared directly via melt mixing. The micro- and mesco- structure, viscoelastic behavior, crystallization, electrical and magnetic as well as mechanical properties of those PPS composites were studied by transmission electron microscope (TEM), scanning electron microscope (SEM), X-ray diffractometer (XRD), polarized optical microscope (POM), dynamic mechanic thermal analyzer (DTMA), differential scanning calorimeter (DSC), rheometer, high-resistance meter and so on. The effect of dispersion state and mesoscopic structure of those micro- and nano-particles on the macroscopic performance of the PPS composites was described using nonlinear percolation theory, crystallization kinetic models, coll-shell theory and emulsion model, aiming at exploring the relations between hierarchical structure and properties of PPS composites.(1) PPS/Fe₃O₄ magnetic compositeThe Fe₃O₄ particles are well dispersed in the PPS matrix due to their nice affinity, which is further confirmed by the dynamic rheological characterization. The strong particle-particle interactions highly influence the viscoelastic behavior of composites. As the loadings level achieving up to 40wt%, the Fe₃O₄ particles form transient rheological network. It is interesting that the electrical percolation threshold is higher than that of rheological percolation, which is due to the difference structure of these two percolation network. In the dynamic shear field, as the Fe₃O₄ particles get to the levels of"close but no contact", the particle-particle interaction is strong enough to form the transient percolation network. To form an electrical network, however, the Fe₃O₄ particles have to contact with each other. Thus the electrical percolation threshold is higher than that of rheological percolation. This physical percolation behavior can not be observed in the magnetic properties of the composites, which only shows linear relation between magnetic properties and the loading levels of Fe₃O₄. Although there are strong interactions between the Fe₃O₄ particles and PPS matrix, the Fe₃O₄ particles have no heterogeneous nucleation effect on crystallization of the PPS. On the contrary, the presence of Fe₃O₄ particles inhibits crystallization process of PPS, decreasing crystallization kinetics. However, the nice interfacial interactions between two phases improve mechanical properties of the composites remarkably.(2) PPS/LMPM compositesThe LMPM particles present well dispersion in the PPS matrix especially at the loading levels lower than 30wt%, while mainly show the morphology of aggregation at high loading levels. The composites present dual viscoelastic characteristics: the stress overshoot is similar to that of polymer blend systems, while the nonzero residual stress behavior is similar to that of filled polymer systems. More or less like Fe₃O₄ particles, the LMPM droplets don't act as a role of additional active substrate and, only act as the inert filler, disturbing the growth of the crystal and reducing the melting point of the composites. However, the flow-promoting effect of the LMPM droplets promotes crystallization of the PPS matrix, increasing crystallization rate.(3) PPS/CNT nanocompositesThe CNTs are well dispersed in the PPS matrix due to their nice affinity. The one-dimensional nano-structure of CNTs results in high volume filled efficiency even in very low weight fraction, which highly restricts relaxation behavior of the PPS chain and as a result, the composites present very low percolation percolation both in rheological and electrical behaviors. In contrast to that of Fe₃O₄ particles and LMPM droplets, the CNTs have remarkable heterogeneous nucleation effect on crystallization of the PPS, promoting crystallization of PPS matrix. The one-dimensional nano-structure of CNTs and the nice affinity between two phases together with the improvement of crystallization enhance the mechanical properties of the composites even at very low loading levels of CNTs. The further addition of CNTs, however, nearly has no positive contribution to the improvement of mechanical properties, which is confirmed by the DMA characterization.(4) PPS/PBT/clay ternary nanocompositesThe intercalated clay tactoids localized selectively in the continuous PBT phase, which shows higher polarity than that of discrete PPS phase. Thus the immiscible morphology of the blend matrices is strongly dependent on the clay loadings. A novel morphology evolution of the immiscible blend matrices is observed with increase of clay loadings. Small addition of clay increases the discrete PPS spherulite domain size. With increasing loading levels, the PPS phase transform to the fibrous structure and finally, to the partial laminar structure at the high loading levels, in which shows a characteristic of large-scaled phase separation. Moreover, the laminar structure of PPS phase is very sensitive to the steady shear flow and is easy to be broken down to spherulite droplet at the low shear rate. However, high shear level is likely to facilitate the coalescence of those PPS phase and finally to phase inversion, both contributing to increases of the dynamic modulus after steady shear flow.