The poly(trimethylene terephthalate) (PTT) containing mesoporous silica (SBA-15) prepared by in situ polymerization were used as the master batch in this work and mixed with the commercial PTT to fabricate PTT/mesoporous silica composites. The mechanical properties and viscoelastic behaviors such as creep and creep recovery of as-obtained composite system were then studied in detail. The results reveal an evident reinforcing effect of the mesoporous SBA-15 particles at the lower loading levels. Compared with those of the pure PTT, the tensile strength and impact strength of the composite with 0.5 wt% SBA-15 particles increase by about 26% and 10%, respectively. This is attributed to the physical crosslinking between SBA-15 and PTT chain caused by the mesoporous structure of SBA-15 particle, which is confirmed by the increased glass transition temperature of the composites relative to the pure PTT. At the higher loading levels, however, the presence of mesoporous particle reduces the overall strength of PTT because the concentration of lower molecular weight PTT in the master batch also increases with increasing loading of SBA-15. Therefore, superfluous addition of master batch has negative contribution to the mechanical strength of PTT composites. Besides, the composite system presents the higher creep levels and the lower recovery rates than the pure PTT, indicating that the presence of mesoporous SBA-15 particles restrains the movements of PTT chain segments during creep and creep recovery. This is further confirmed by the viscoelastic model predictions. POLYM. COMPOS., 36:1386–1393, 2015. © 2014 Society of Plastics Engineers

Ethylene-vinyl acetate copolymer (EVA)/poly(ϵ-caprolactone) (PCL) blend (50/50 w/w) with co-continuous morphology was prepared via melt mixing for fabricating microporous EVA membrane materials through selective solvent extraction. Shear flow and quiescent annealing techniques were employed to control co-continuous phase size in the EVA/PCL blend, and the time- and temperature-dependent relations of phase size were then evaluated theoretically. Using these techniques, microporous EVA membrane materials with various pore sizes ranging from 2 µm to more than 200 µm were obtained. In contrast to the porous EVA membrane prepared by the traditional way of solvent casting/particulate leaching, the as-obtained microporous membrane shows a higher level of interconnectivity and much narrower pore size distribution with uniform pore structure. © 2013 Society of Chemical Industry

Carbon black (CB)–filled poly(vinylidene fluoride) composites (PCBp) were prepared by melt compounding. The linear rheology was then studied in detail. The composites show typical solid-like response in the low-frequency region, which is attributed to the percolation of CB particles. However, the transient percolated CB network is temperature dependent during the small amplitude oscillatory shear flow. Therefore, the principle of time–temperature superposition is invalid on the dynamic rheological responses of those percolated PCBp. A two-phase viscoelastic model was then used to further describe the linear responses of PCBp to relate hierarchical structures of CB particles to flow responses of composites. In addition, the electrical and dielectric properties of PCBp were also investigated, aiming at further exploring the percolation behavior of CB. POLYM. ENG. SCI., 53:2541–2548, 2013. © 2013 Society of Plastics Engineers

The crystallization of poly(trimethylene terephthalate) (PTT) composites containing carbon nanotubes (CNTs) were studied in this work. The electrospinning technology was employed successfully to fabricate thin film samples with well-embedded CNTs for spherulite observations using atom force microscopy. The results show that the composites present a higher overall crystallization rate than that of the neat PTT due to the nucleation effect of the CNTs. Banded spherulites can be observed on both the neat PTT and the composites. The presence of CNTs does not change the twisting mode of PTT crystal, but reduces band spacing and twist period. This is attributed to the enhanced fold staggering level of lamellae caused by the narrowed lamellae size and accelerated spherulite growth, which is further confirmed by analysis through secondary nucleation theory. Copyright © 2011 Society of Chemical Industry

Electrospinning of the biodegradable polylactide (PLA) and its composites containing carbon nanotubes (CNTs) was studied in terms of solution concentrations and solvents effects as well as CNT loadings. The results reveal that the PLA fibers obtained from the solutions using the mixed solvents of chloroform/assistant solvent (v/v 3/1) show better morphologies than those from the solutions using chloroform as the single solvent. This is due to the synergistic effect by the improved conductivity and altered viscosity with addition of assistant solvent. Moreover, the surface structure of fibers depends on the volatility of assistant solvents strongly. Using volatile acrylonitrile or acetone as the assistant solvents, the columned fibers with porous surface structure are obtained; while the flat fibers with fluted surface are formed using nonvolatile dimethyl sulfoxide as the assistant solvents. As for electrospinning of the PLA/CNT composites, the morphology of obtained fibers is closely related to the dispersion of CNTs in the fibers. At low loading levels, the CNTs can be well embedded in the PLA matrix and oriented along the fiber axis, forming nanowire structure. At high loading levels, the CNTs are mainly dispersed as entangled bundles along the fiber axis, and as a result, the obtained fibers show tortuous or misshaped morphologies. Compared with that of the neat PLA fibers, the overall morphologies of the composite fibers are more or less degraded because the presence of some small CNT aggregates in the solutions easily leads to the formation of beaded fiber structure during electrospinning. The conductivity of the obtained composite fiber mats was further studied in terms of CNT loadings. POLYM. COMPOS., © 2011 Society of Plastics Engineers.

The biodegradable polylactide composites containing carbon nanotubes (CNTs) with high aspect ratio (HAR) and low aspect ratio (LAR) were prepared by melt mixing. The physical properties of those two systems were characterized in terms of rheology, conductivity, and mechanical properties for establishing preliminary structure–property relations. Several viscoelastic models were then used to further describe the relations between aspect ratio and percolation network of CNTs. The results show that these two CNTs present different structural characteristics in the polylactide (PLA) matrix during melt mixing: the LAR CNTs are far stiffer than the HAR CNTs. At low loading levels, the former is dispersed as bent fibers or their small bundles, whereas the latter is dispersed as self-entangled flocs, presenting far larger hydrodynamic radius than the former. At high loading levels, both are dispersed as flocs due to strong tube–tube interactions. However, the two CNTs show approximate average floc size and mesh size because they present same rigid length and effective aspect ratio. At identical loadings, therefore, the HAR CNTs have more total number of flocs than that of the LAR CNTs, forming network with more compact structure and imparting higher contributions to properties of the composites as a result. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 479–489, 2010

Poly(ε-caprolactone)/polylactide blend (PCL/PLA) is an interesting biomaterial because the two component polymers show good complementarity in their physical properties. However, PCL and PLA are incompatible thermodynamically and hence the interfacial properties act as the important roles controlling the final properties of their blends. Thus, in this work, the PCL/PLA blends were prepared by melt mixing using the block copolymers as compatibilizer for the studies of interfacial properties. Several rheological methods and viscoelastic models were used to establish the relations between improved phase morphologies and interfacial properties. The results show that the interfacial behaviors of the PCL/PLA blends highly depend on the interface-located copolymers. The presence of copolymers reduces the interfacial tension and emulsified the phase interface, leading to stabilization of the interface and retarding both the shape relaxation and the elastic interface relaxation. As a result, besides the relaxation of matrices (τ_m) and the shape relaxation of the dispersed PLA phase (τ_F), a new relaxation behavior (τ_β), which is attribute to the relaxation of Marangoni stresses tangential to the interface between dispersed PLA phase and matrix PCL, is observed on the compatibilized blends. In contrast to that of the diblock copolymers, the triblock copolymers show higher emulsifying level. However, both can improve the overall interfacial properties and enhance the mechanical strength of the PCL/PLA blends as a result. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 756–765, 2010

The crystallization behavior of polylactide/carbon nanotube composites was studied using differential scanning calorimeter and polarized optical microscope. The nucleation mechanisms and the crystallization kinetics were explored. The results show that the presence of nanotubes has nucleating effect on both the melt crystallization and the cold crystallization of PLA. However, the nanotubes also play the role of physical barrier, impeding the crystal growth dynamically. In the experimental range of temperatures, the presence of nanotubes accelerates the melt crystallization, while retards the overall kinetics of the cold crystallization. The biodegradability of the samples with various crystallization histories was then further examined. The results show that the presence of nanotubes reduces the biodegradation rate of PLA, and the amorphous sample shows the highest degradation levels. Moreover, a lower degradation level is observed both on the surface and inside the sample with melt crystallization history in contrast to the one with cold crystallization history. POLYM. ENG. SCI., 50:1721–1733, 2010. © 2010 Society of Plastics Engineers

BACKGROUND: The aim of the work presented was to study the nanostructural evolution of clay tactoids during the isothermal cold crystallization of polylactide/clay nanocomposites (PLACNs). An interesting degradation behavior of the polylactide (PLA) matrix, however, was observed simultaneously with nanostructural evolution. The possible mechanisms of degradation and structural evolution are discussed.

RESULTS: The evolution of the nanostructure and the degradation were studied online or offline using parallel plate rheometry, X-ray diffraction, transmission electron microscopy, differential scanning calorimetry, nuclear magnetic resonance spectroscopy, gel permeation chromatography and thermogravimetric analysis. The results showed that the intercalation level of the clay tactoids further increased during cold crystallization, leading to simultaneous degradation of the PLA matrix, which was further confirmed by the marked change of small- and large-amplitude oscillatory shear flow behavior of the PLACNs before and after cold crystallization.

CONCLUSION: The increase of the intercalation level of the tactoids is due to the diffuse in movement of the PLA chain segments during cold crystallization. In this case, chain-end scission occurs more easily, especially for those PLA chains around the loose edge and defect site of the tactoids during crystallization, which results in a simultaneous degradation of the PLA matrix. Hence, both the linear and nonlinear dynamic viscoelastic properties show a remarkable change after cold crystallization. Copyright © 2009 Society of Chemical Industry

The multiwalled carbon nanotubes were directly compounded with poly(phenylene sulfide) (PPS) via melt mixing. The morphology and physical properties, including viscoelasticity, electrical conductivity, and thermal and mechanical properties, of the obtained composites were investigated. The results show that the purified nanotubes can be fully dispersed in the PPS matrix especially at low loading levels because of their good affinity. The composites hence present relative low rheological and electrical percolation thresholds. The presence of nanotubes, on the one hand, shows good reinforcement effect because of the strong interfacial interactions with the PPS matrix, which is confirmed by the strain overshoot flow behavior, and, on the other hand, acts as a nucleation agent, promoting crystallization of the PPS matrix. Both contribute to evident improvement of tensile strength and dynamic mechanical properties of the composites. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers

The biodegradable polymer blend containing 70/30 weight ratio of poly(ε-caprolactone) (PCL) and polylactide (PLA) was prepared by means of melt mixing. The evolution of the “sea-island” phase structure in the steady shear flow was studied using scanning electron microscope (SEM) and parallel-plate rheometer. The results show that the morphological evolution induced by steady shear follows different mechanisms at various flow rates. The lower shear rates (Newtonian flow) promote coalescence of the discrete PLA droplets, whereas higher shear rates (non-Newtonian flow) promote break-up of the droplets. The dynamic rheological responses of PCL/PLA blend before and after steady preshear were then analyzed using emulsion model and Taylor equation. The results show that the evolution approaches of the morphology highly depend on changed level of the critical effective interfacial tension in the steady shear flow, which are further confirmed by the transient rheological measurements. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers

The multiwalled carbon nanotubes/polypropylene nanocomposites (PP/CNTs) were prepared by melt mixing using maleic anhydride grafted polypropylene (mPP) as the compatibilizer. The effect of mPP on dispersion of CNTs was then studied using the tool of rheology, aiming at relating the viscoelastic behaviors to the mesoscopic structure of CNTs. To further explore the kinetics of hybrid formation, a multilayered sample with alternatively superposed neat mPP and binary PP/CNTs microcomposites (without addition of mPP) sheets was prepared and experienced dynamic annealing in the small amplitude oscillatory shear flow. The results show that melt blending CNTs with PP can only yield the composites with microscale dispersion of CNTs, while adding mPP promotes nanoscale dispersion of CNTs as smaller bundles or even as individual nanotubes, reducing percolation threshold as a result. However, the values of apparent diffusivities of the composites are in same order with that of self-diffusion coefficients of the neat PP, indicating that the presence of detached CNTs nearly does not inhibit PP chain motion. Hence, the activation energy of hybrid formation is close to the self-diffusion of PP. This also indicates that although addition of mPP can improve the compatibility between CNTs and PP thermodynamically, those dynamic factors, such as shear flow, however, may be the dominant role on hybrid formation. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 608–618, 2009

Polyarylene ether nitriles (PEN)/thermotropic liquid crystalline polymer (TLCP) blend was prepared via melt mixing. The immiscible phase morphologies, linear and nonlinear, as well as transient viscoelastic properties of the blend were studied using SEM, rheometer, and DMA. The linear dynamic viscoelastic behavior of the blend shows temperature dependence due to further evolution of the immiscible morphology and, as a result, the principle of time-temperature superposition (TTS) is invalid. In the steady shear flow, the discrete TLCP phase is difficult to be broken up because of the high viscosity ratio of the blend systems, while is easy to be coarsened and followed by elongation, and finally, to form fibrous morphology at high TLCP content and high shear level. During this morphological evolution process, the transient stress response presents step increase and nonzero residual relaxation behavior, leading to increase of the dynamic viscoelastic responses after steady preshear. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

Multi-walled carbon nanotube/polypropylene composites (PPCNs) were prepared by melt compounding. The linear viscoelastic properties, nonisothermal crystallization behavior, and kinetics of PPCNs were, respectively, investigated by the parallel plate rheometer, differential scanning calorimeter (DSC), X-ray diffractometer (XRD), and polarized optical microscope (POM). PPCNs show the typical nonterminal viscoelastic response because of the percolation of nanotubes. The rheological percolation threshold of about 2 wt % is determined using Cole-Cole method. Small addition of nanotube can highly promote crystallization of PP matrix because of the heterogeneous nucleating effect. With increasing nanotube loadings, however, the crystallization rate decreases gradually because the mobility of PP chain is restrained by the presence of nanotube, especially at high loading levels. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci 2008

Poly(phenylene sulfide) (PPS)/poly(butylene terephthalate) (PBT) (60/40 w/w) blend nanocomposites (PPS/PBTs) were prepared by direct melt compounding of PPS, PBT, and organoclay. The morphology and rheology of PPS/PBTs were investigated using scanning electron microscope and transmission electron microscope as well as parallel plate rheometer. The intercalated clay tactoids are selectively located in the continuous PBT phase due to their nice affinity. 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. The presence of clay, however, does not impede the coalescence of the PPS phase because the phase size increases with increasing clay loadings. The elasticity and blend ratio of two matrices are proposed as the important roles on the morphological evolution. 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. In conclusion, the morphology of the immiscible polymer blend nanocomposites depends strongly on both the clay loadings and shear history. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 1265–1279, 2008

Poly(phenylene sulfide)/ferrosoferric oxide composites (PPS/Fe₃O₄) with various loading levels were prepared by melt compounding. The microstructure of composites was investigated using SEM and XRD. The rheological, electrical and magnetic properties were characterized respectively by the parallel plate rheometer, high resistance meter, and magnetometer. The results reveal that the Fe₃O₄ particles are well dispersed in the PPS matrix due to their nice affinity, which results in a weak strain overshoot at large amplitude oscillatory level. Both the rheological and the electrical responses of the composites show a typical percolation behavior. But the rheological percolation presents lower threshold (< 40 wt %) than that of electrical percolation (∼ 50 wt %), which is attributed to the difference structure of the percolation network. The magnetic response, however, shows good linear relation with Fe₃O₄ loadings, indicating that the physical percolation has little influence on the magnetic properties. This is mainly due to the yielded long-range magnetic interactions among Fe₃O₄ particles in the applied field, which are far stronger than those nonmagnetic physical interactions accounting for percolation. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 233–243, 2008

Poly(phenylene sulfide)/low-melting-point metal composites (PPSMs) with various loading levels were prepared by melt compounding. The nonisothermal crystallization behavior and transient viscoelastic properties were characterized by the DSC, POM, DMA, and parallel-plate rheometer. The results reveal that the low-melting-point metal (LMPM) particles show nice dispersion at relative low content levels (< 30 wt %). The PPSMs composites present dual characteristics of both the filled polymer composite and polymer blend system in their transient viscoelastic behaviors, which results in occurrence of the stress overshoots with long relaxation time and nonzero residual stress especially at high shear levels. During the crystallization process, the presence of those deformable LMPM droplets facilitates the crystallization kinetics of PPS because of their flow-promoting action. On the other hand, the LMPM has no heterogeneous nucleating effect and, only plays the role of inert filler, which results in the degradation of the crystal structure of PPS. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 677–690, 2008

Poly(phenylene sulfide)/ferrosoferric oxide composites (PPS/Fe₃O₄) with various loading levels were prepared by melt compounding. The crystallization, thermal, and viscoelastic properties were characterized respectively by the DSC, DMA, TGA and parallel plate rheometer. The results reveal that the well-dispersed Fe₃O₄ particle restricts the segmental motion of polymer chain, leading to a remarkable increase of the glass transition temperature and thermal stability of the PPS due to the strong physical association and interactions between particles and matrix. The presence of the Fe₃O₄ particles, however, can not facilitate crystallization of PPS, because the particles only play the role of inert filler and have no heterogeneous nucleating effect. The crystallization kinetics, as a result, decreases with increasing particles loadings due to the increasing restriction of the chain mobility and high viscosity. In addition, the rheological percolated network of the Fe₃O₄ particles is very sensitive to the steady shear deformation, and also to the temperature. The network structure is easily broken by the steady shear flow due to the sharply reduced particle–particle interactions. However, the percolation threshold reduces with increase of temperature, because those interactions are temperature-dependent. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers

Multiwalled carbon nanotube/poly(butylene terephthalate) composites (PCTs) were prepared by melt mixing. The nonisothermal crystallization and thermal behavior of PCTs were respectively investigated by X-ray diffractometer, polarized optical microscope, differential scanning calorimeter, dynamic mechanical thermal analyzer, and thermogravimetric analyzer. The presence of nanotubes has two disparate effects on the crystallization of PBT: the nucleation effect promotes kinetics, while the impeding effect reduces the chain mobility and retards crystallization. The kinetics was then analyzed using Ozawa, Mo, Kissinger, Lauritzen-Hoffman, and Ziabicki model, and the results reveal that the nucleation effect is always the dominant role on the crystallization of PBT matrix. Thus the crystallizability increases with increase of nanotube loadings. In addition, the presence of nanotubes nearly has no remarkable contribution to thermal stability because nanotubes also play two disparate roles on the degradation of PBT matrix: the Lewis acid sites to facilitate decomposition and the physical hindrance to retard decomposition. Hence the nanotubes act merely as inert-like filler to thermal stability. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers