超细CaCO3的聚合物胶囊化研究

先通过乳液聚合制备了粒径约为100nm带正电荷的聚苯乙烯PS纳球,再利用异相凝集,使正电性的PS吸附在带负电荷的超细碳酸钙（CaCO3）表面,后在高于PS玻璃化温度（Tg)下,进行热处理,形成胶囊化复合粒子,用Zeta电势,扫描电镜和粒径分布对复合前后的粒子进行了表征。     

Rheological behavior of polymer blends

Steady and oscillatory shearing flow properties of compatible and incompatible polymer blend systems were measured, using a cone-and-plate rheometer. The compatible blend systems investigated are blends of two low-density polyethylenes (LDPE) having different values of molecular weight and blends of poly(methyl methacrylate) (PMMA) with poly(vinylidene fluoride) (PVDF). The incompatible blend system investigated is a blend of poly(methyl methacrylate) (PMMA) with polystyrene (PS). It was found that (1) plots of first normal stress difference (τ₁₁ – τ₂₂) vs. shear stress (τ₁₂) and plots of storage modulus (G′) vs. loss modulus (G″) for the LDPE blends become independent of temperature and blend composition; (2) plots of τ₁₁ – τ₂₂ vs. τ₁₂, and G′ vs. G″ for the PMMA/PVDF blends become independent of temperature but dependent upon blend composition. It was found further that, for the incompatible PMMA/PS blends, the dependence of τ₁₁ – τ₂₂ on blend composition, when plotted against τ₁₂, is different from the dependence of G′ on blend composition, when plotted against G″. However, in both compatible and incompatible blend systems, plots of τ₁₁ – τ₂₂ vs. τ₁₂ and plots of G′ versus G″ are independent of temperature. The seemingly complicated composition-dependent rheological behavior of the incompatible blend system is explained with the aid of photomicrographs describing the state of dispersion.     

Viscoelastic behavior of polymer blends

There is a reciprocal relation between flow and structure in multiphase systems such as polymer blends or composites. For this reason characterization of these materials must be carried out under conditions which guarantee minimum modification of structure. Capillary rheometry is particularly ill suited as a test tool, but the small strain dynamic oscillatory method may provide the true material responses, Most frequently these are expressed as frequency, ω, dependent storage and loss shear moduli, G′ and G″, or real and imaginary viscosities, η′ = G″/ω and η″ = G′/ω. However, two other methods of data presentation seem to be more sensitive to melt structure. They are the Cole-Cole plot of η″ vs. η′ and the relaxation spectrum. Frequently, both of them indicate a binomial response. Various mechanisms leading to such behavior will be discussed.     

Preparation of acrylate polymer/silica nanocomposite particles with high silica encapsulation efficiency via miniemulsion polymerization

Acrylate polymer/silica nanocomposite particles were prepared through miniemulsion polymerization by using methyl methacrylate/butyl acrylate mixture containing the well-dispersed nano-sized silica particles coupling treated with 3-(trimethoxysilyl)propyl methacrylate (MPS). The encapsulation efficiency of silica particles was determined through the elution and hydrofluoride acid etching experiments, and the size distribution and the morphology of the composite latex particles were characterized by dynamic light scattering and transmission electron microscopy. The coupling treatment of silica with MPS can improve the encapsulation efficiency of silica and the degree of grafting of polymer onto silica. When 0.10 g MPS/g silica was used to modify silica, the encapsulation efficiency of silica was greater than 95%, and the degree of grafting of acrylate polymer onto silica was about 60%. Although the average size and the size distribution index of the composite latex particles increased as the weight fraction of silica increased, the stable latex containing the ‘guava-like’ composite particles was obtained. The grafting of polymer onto silica particles improved the dispersion of silica particles in the solvents for acrylate polymer and in the polymer matrix.     

Factors influencing the formation of elongated morphologies in immiscible polymer blends during melt processing

The morphology of the dispersed phase in immiscible polymer blends plays an important role in the determination of the final physical properties. This paper considers factors that influence the final state of deformation of the dispersed phase, and in particular, the formation of fibers and lamellae. Blends of polyethylene and nylon-6 were extruded by ribbon extrusion at different draw ratios. Prior to single-screw extrusion the materials were blended in a co-rotating twin-screw extruder, and the size of the dispersed phase was studied as a function of the viscosity ratio. As the blends are extruded into ribbons and drawn through the calender rolls, the morphology of the dispersed phase undergoes drastic transformations. The fiber formation is enhanced by increasing the draw ratio. At high draw ratios, long thin fibers are observed. Some biaxial deformation is obtained for the noncompatibilized systems when the extruded materials enter the calender with the maximum closing pressure applied to the rolls. The same effect is observed for the compatibilized systems with lower values of the viscosity ratio. As a general rule, it has been observed that the final dispersed phase deformation is diminished in interfacially compatibilized systems.     

Urethane/acrylic composite polymer emulsions

Blends of waterborne urethane and acrylic polymer systems were studied to obtain a composite emulsion that would have all of the advantages of the two polymers without their associated disadvantages. An approach to achieve extensive polymer-polymer interactions through crosslinking reactions was studied to optimize the positive aspects of each polymer. The crosslink system used an acrylic polymer emulsion containing keto or aldo groups and a polyurethane dispersion incorporating a hydrazine group. The degree of crosslinking was determined by FT-IR Single package, ambient temperature crosslinking emulsions were obtained by using this system. In addition to the excellent properties these two polymers normally possess, the crosslinked blends exhibit synergistic effects in film properties, such as good solvent resistance and low heat sensitivity over a wide range. Composite polymers of this type could be useful in applications where high durability is required: tennis court coatings, floor coatings, laminating adhesives. and paper and textile finishes.     

Phase behavior of semicrystalline polymer blends

The phase behavior of the semicrystalline polymer blend composed of isotactic polypropylene (iPP) and linear low density polyethylene (PE) was studied using small angle X-ray scattering (SAXS) and optical microscopy (OM). Based on the random phase approximation, the iPP/PE interaction parameter, χ, was obtained, and used to construct the iPP/PE phase diagram. The χ values reported in this study are lower than the χ values for deuterium-labeled moieties, measured by small angle neutron scattering (SANS). The predicted phase diagram has upper critical solution temperature (UCST) behavior with a critical temperature of 143 °C for the molecular weights used in this study. OM was used to locate cloud points and the results are consistent with the predicted phase diagram. Since iPP melts above the critical point, care was taken to distinguish phase separation from iPP crystallization by studying the kinetics of iPP crystallization, and the iPP crystallization was discerned from dewetting. In PE-rich blends, the iPP crystallization was suppressed and no dewetting was observed.     

Process behavior of compatible polymer blends

It is a common industrial practice to blend virgin polymer with the same polymer recycled from scrap plastic that, in general, has not undergone relevant degradation. In this article, the influence that incorporating recycled material has on injection processes, especially on the rheological behavior of the material was studied. With this aim in mind, a mixture of two materials with the same nature or composition and similar viscosity was used, which is the system that is most commonly seen in industry. The mixture studied is composed of virgin PP (polypropylene) typically found in injection processes, and recycled copolymer PP from scrap plastic. A complete characterization of the materials and applied existing models was carried out to predict the mechanical behavior of the mixtures. A model to predict the behavior of the mixtures during processing, based on the rheological characteristics of the materials used was developed. This predictive model has been experimentally validated using filling tests in injection molding machines, as well as by specific simulation software. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Phase behavior of ternary polymer blends

The effect of varying interaction parameters on the phase diagrams of ternary polymer blends was explored by simulating spinodals through use of the Flory-Huggins lattice theory. Results indicate that miscibility is favored for the case of ternary mixtures of marginally miscible or marginally immiscible pairs where all pair interactions are nearly athermal. Miscibility is restricted for asymmetric ternary blends when one of the polymer pairs is either strongly miscible or strongly immiscible. For symmetric blends of partially immiscible pairs, both two-phase and three-phase miscibility gaps are predicted.     

Network model for the viscoelastic behavior of polymer nanocomposites

A theoretical network model reproducing some significant features of the viscoelastic behavior of unentangled polymer melts reinforced with well dispersed non-agglomerated nanoparticles is presented. Nanocomposites with low filler volume fraction (∼10%) and strong polymer-filler interactions are considered. The model is calibrated based on results obtained from discrete simulations of the equilibrium molecular structure of the material. This analysis provides the statistics of the network of chains connecting fillers, of dangling strands having one end adsorbed onto fillers, and that of the population of loops surrounding each nanoparticle. The network kinetics depends on the attachment-detachment dynamics of grafted chains of various types and is modeled by using a set of convection equations for the probability distribution functions. The overall viscoelastic response depends strongly on the lifetime of the polymer-filler junctions. The largest reinforcement is observed at low strain rates and low frequency oscillations. A solid like behavior is predicted for systems in which the polymer molecules interact strongly with the nanoparticles, effect which is associated with the behavior of the network of bridging segments.     

Facile encapsulation of nanoparticles in nanoorganized bio-polyelectrolyte microshells

We present a facile method for the encapsulation of nanoparticles' (NPs) systems within the interior space of bio-polyelectrolyte microshells. The microshells, constructed by alternate adsorption of alginate sodium (ALG) and chitosan (CHI) onto the surface of colloidal templates and subsequent removal of cores, allow the polystyrene (PS) or SiO₂ nanoparticles (NPs) adsorbed into the internal shells through a simple mix process, as confirmed by confocal laser scanning microscopy (CLSM), and scanning electron microscopy (SEM) analysis. The NPs-filled microshells form the rigid spherical shape in contrast to the flat and folded structure of microshells at the dry state prior to filling. The interior of NPs-encapsulated microshells was directly visualized by transmission electron microscopy (TEM) image of microtomed slices and cross-section SEM image. The loading amount of NPs in a shell composed of (ALG/CHI)₅ was determined in two media i.e. H₂O and 0.1 M NaCl, and the results showed that the loading amount of the former is greater than that of the latter. The possible encapsulation mechanism is also discussed. The hybrid materials with NPs core and bio-polyelectrolyte shells have potential application for controlled-release drug delivery and catalysis.     

Fractal behavior of spinodal decomposition in polymer blends

Summary Fractal behaviour of ramified domains in the late stage of spinodal phase separation in a binary polymer blend of poly(vinyl acetate) with poly(methyl methacrylate) was investigated by optical microscopic method. In the late stage of the spinodal decomposition, the fractal dimension D is about 1.64. It implies that some anomalous properties of irregular structure probably may be explained by fractal concepts.     

The rheological behavior of immiscible polymer blends

The complex shear modulus of immiscible polymer blends was measured by a frequency sweep experiment for polystyrene (PS)/low density polyethylene (LDPE) and poly(methylmethacrylate) (PMMA)/LDPE blends at constant composition (13.5/86.5 vol %) and compared with the prediction model of Palierne. Different morphologies of each blend were also prepared using a rheometer with a constant shear rate and different strain. There was morphological dependency on the complex shear modulus at constant temperature. However, this dependency disappeared at specific temperatures in the frequency sweep experiment. There seemed to be a specific temperature like critical flow temperature (T_cf) of amorphous polymer. The difference in morphology affected the complex shear modulus of blends below the specific temperature, T_cf, but did play a major role in determining the complex shear modulus of blends at over specific temperature. A new method may be needed to determine the critical flow temperature of an amorphous polymer via the measurement of a complex shear modulus for immiscible polymer blends. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 917–924, 2002     

Porous composite structures derived from multiphase polymer blends

Porous biopolymer structures have attracted a lot of attention in the recent years because of their potential applications in tissue engineering. In this work, porous structures of poly(lactic‐co‐glycolic acid) (PLGA) reinforced with organically modified montmorillonite (Cl15A) were fabricated. A ternary, co‐continuous blend consisting of PLGA/PS/Cl15A (PS: Polystyrene) was prepared by melt extrusion. Then, a porous PLGA composite was created by the sacrificial extraction of the PS phase. The morphological characterization revealed the creation of a well‐formed 3D porous network consisting of Cl15A‐reinforced PLGA. Quantitative results obtained from the scanning electron microscopy (SEM) micrographs of the fabricated porous structures show that small variations in the clay loading affect the geometrical characteristics (% porosity and pores average diameter) of these porous structures. The results suggest that these porous PLGA/clay structures may be promising candidates for mechanically strong scaffolds in tissue engineering applications, but this remains upon testing. POLYM. ENG. SCI., 55:1856–1863, 2015. © 2014 Society of Plastics Engineers     

LCST and UCST behavior in polymer solutions and blends

We introduce a model for polymer solutions and blends that display both an upper and a lower critical solution temperature (UCST, LCST). Using our simple analytic lattice theory along with a fixed parameter set independent of both composition and temperature, we study solutions and blends exhibiting complicated miscibility patterns, including cases in which a UCST is below an LCST, or above. With respect to the former, we examine the conditions under which a so-called hourglass phase diagram may evolve. Where possible we compare directly with experiment, however, we also explore the behaviour of a number of hypothetical solutions and blends. One experimental solution of particular interest comprises star polystyrene (PS) and cyclohexane; in this case we supply what we believe are the only measured pressure-volume-temperature data for a high molecular weight (5.2 × 10⁵ g/mol) star PS.     

Percolation behavior in morphology and modulus of polymer blends

The tensile property of a plastic/rubber blend depends critically on the morphology and connectivity of the two phases. At low plastic volume fractions, the plastic phase forms isolated domains in the matrix of rubber phase, and the tensile property of the blend is largely controlled by the continuous rubber phase. As the plastic volume fraction increases, the plastic phase gradually connects into a pervasive network that eventually dominates the tensile and shear properties of the blend. The transition of the blend from a rubber-dominated to a plasticdominated behavior is a manifestation of percolation transition. The plastic volume concentration at which the transition takes place is the percolation threshold. Its dependence on morphology is discussed by contrasting the behaviors of anisotropic injection-molded specimens vs. isotropic compression-molded specimens of the two-phase blends of an amorphous thermoplastic polyester, PETG, and an ethylene-propylene-diene rubber, EPDM. It is found that the tensile modulus just above the percolation threshold obeys a power law as a function of the plastic volume concentration in excess of the percolation threshold. By analyzing the longitudinal tensile modulus of injection-molded PETG/EPDM specimens just above the threshold, it is shown that the scalar elastic percolation theory of de Gennes is at work here. For compression-molded PETG/EPDM specimens, it is found that the isotropic tensile modulus over the entire composition range obeys the symmetric effective medium theory.     

Crystallization behavior of PBT/ABS polymer blends

Poly(butylene terephthalate) (PBT) crystallization behavior is modified by blending it with acrylonitrile‐butadiene‐styrene copolymers (ABS). The effects of ABS on melting and crystallization of PBT/ABS blends have been examined. Most ABS copolymers of different rubber content and styrene/acrylonitrile ratios studied showed little effect on the melting behavior of PBT crystalline phase. However, ABS copolymer with high acrylonitrile content had a significant effect on the crystallization behavior of the PBT/ABS blends. The nucleation rate of the PBT crystalline phase decreased due to the presence of the high acrylonitrile content ABS, whereas the spherulitic growth rate increased significantly. These phenomena are attributed to changes in nucleation and growth mechanisms of PBT crystalline phase promoted by ABS. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 423–430, 1999     

The viscoelastic behavior of polymer/oligomer blends

The viscoelastic properties of poly(α-methyl styrene), its hexamer, and their athermal blends at various concentrations are studied. Master curves for the dynamic shear responses, G′ and G″, are successfully constructed for both the pure materials and the blends, indicating the validity of the time-temperature superposition principle for these systems. The temperature dependence of the shift factor follows the Vogel-Fulcher behavior over the temperature range studied, and the temperature dependence is slightly weaker for the blends. The rubbery plateau modulus scales with the polymer concentration as ; the terminal relaxation time scales with the polymer concentration as . The shape of the segmental dispersion appears unchanged by concentration, which differs from our calorimetric studies where mixtures show obviously temperature-broadened glass transitions and depressed enthalpy overshoots. The TNM (Tool-Narayanaswamy-Moynihan) model indicates that the change in the temperature dependence is not sufficient to account for the observed calorimetric broadening. We conclude that the temperature broadening of the glass transition for our blends is not due to a broadening of the dynamic spectrum or to changes in its temperature dependence. The possibility that the broadening is due to changes in the non-linearity parameter x in the TNM model is also considered. While the broadening could be due to a decreasing value of x, we found that this same decrease would lead to increasing enthalpy overshoots on heating, contrary to the experimental observations. The combination of the calorimetric results with the rheological measurements further indicates that the fundamental basis of the TNM-type of model of structural kinetics in glasses is potentially wrong.     

Mechanical and morphological behavior in polystyrene based compatible polymer blends

Mechanical and morphological behavior of polystyrene (PS) based compatible polymer blend systems were studied using a tensile tester and scanning electron and optical microscopes. Four different binary compatible blend systems were employed and characterized: PS and poly (2,6-dimethyl 1,4-phenylene oxide) (PPO), PS and poly(vinylmethylether)(PVME), PS and poly(α-methyl styrene)(PαMS), and PPO and PαMS. The compositional dependence of the mechanical properties showed a synergistic effect with respect to modulus, but a negative deviation from the rule of mixtures relationship for strain at break. From the scanning electron microscope (SEM) observations, a deformation mode transition from crazing to crazing and shear banding occurs at ˜25 wt% PPO in the PS/PPO blends, as indicated by the patch and river patterns above this composition. In the PS/PVME blends, a similar transition was observed at >10 wt% PVME. The PS/PαMS blends showed brittle fracture regardless of composition. The PPO/PαMS blends showed a brittle fracture for a PαMS content >25 wt%. Optical microscope (OM) observations showed that blending of PS/PPO and PS/PVME resulted in a decrease of craze density and length as the PPO and PVME content was increased. PS/PαMS and PPO/PαMS blends showed few crazes, all of which were localized near the fracture surface. The mechanical and morphological behavior can be explained using models of intermolecular interactions and entanglement density in compatible blends, respectively. Overall the mechanical property and the consequent morphological behavior were similar to the effect of antiplasticization.