Criteria for rheological compatibility of polymer blends are suggested. The criteria suggested make use of plots of first normal stress difference (N1) against shear stress (σ12), and of storage modulus (G′) against loss modulus (G″). Compatible blend systems considered are (1) blends of two different grades of low-density polyethylene, (2) blends of poly(vinylidene fluoride) and poly(methyl methacrylate), (3) blends of poly(2,6-dimethyl-1,4-phenylene oxide) and polystyrene, and (4) blends of poly(styrene-co-acrylonitrile) and poly(styrene-co-maleic anhyride). And incompatible blend systems considered are (1) blends of nylon 6 and poly(ethylene-co-vinyl acetate) and (2) blends of nylon 6 and an ethylene-based multifunctional polymer. It has been found that plots of N1 vs. σ12 and G′ vs. G″ give (a) temperature-independent correlations for both compatible and incompatible blend systems; (b) composition-independent correlations for compatible blends; (c) composition-dependent correlations for incompatible blends. 相似文献
Plastics in solid wastes is a problem of growing concern. Recycling of wastes is currently believed to be the most acceptable form of disposal in the long run; however, this route is known to be especially difficult for plastics. Recycling would be easier if the various generic types present in solid wastes, mainly polyethylene, polystyrene and poly (vinyl chloride), could be isolated; however, this would be very difficult and expensive. This is a first report on research aimed at evaluating the potential of recycling plastics as a polymer blend of the various generic types. This approach suffers from the difficulty that the different plastics are incompatible and the blend has poor mechanical properties. The extent of this problem is documented with data on many ternary blends employing virgin polyethylene, polystyrene and poly (vinyl chloride) of numerous grades likely to be found in solid wastes. Property degradation was found to be more severe as the complexity of the blend increased, indicating that general municipal wastes could be reused only in very low grade applications, whereas certain commercial wastes might have brighter prospects. Strategies for improving blend properties are outlined. 相似文献
The gas permeability of O2 and CO2 was sutidied for various polymer blend membranes of polystyrene (PSt) and poly[1,1,1-tris(trimethylsiloxy)methacrylate propylsilane (PTMPS). In order to improve the compatibility of these polymer blends, the effect of addition of the graft copolymer was also investigated. The gas permeability of various composition polymer-blend membranes increases rapidly with an increasing content of PTMPS in the polymer blend. In the polymer blend membranes containing the graft copolymer, the gas permeability decreases with an increase in the graft copolymer content and then reaches a nearly constant value, when the PTMPS content remains constant. This result is attributed to a decrease in interstices at phase boundaries, owing to improvement in compatibility of the component polymers. This method of membrane preparation is very useful for making membranes with required properties. 相似文献
The effects uncompatibilized immiscible polymer blend compositions on the Tg of the amorphous polymer were studied in the systems polystyrene/polypropylene (PS/PP), polystyrene/high density polyethylene (PS/PE) and polycarbonate/high density polyethylene (PC/PE). In the two similar systems of PS/PP and PS/PE, the Tg of PS increased with decreasing PS percentage in the blends. This variation in glass transition is attributed to the polymer domain interactions resulting from the different morphologies of various blend compositions. Experiments were conducted to study these effects by preparing blends with various polymers that varied the relationship between the Tg of the amorphous polymer and the crystallization behavior of the semicrystalline polymer. Results show that the variation in amorphous component Tg with composition depends strongly on the physical state of the semicrystalline domains. Whereas the Tg of PS in PS/PE blends changed with composition, the Tg of PC in the PC/PE blend did not change with composition. 相似文献
The interfacial tension, phase morphology, and phase growth was determined for four polymer blend systems: polyethylene/polystyrene, polyethylene/polyamide-6, polystyrene/polyamide-6, and polystyrene/poly(ethylene terephthalate). Generally, high interfacial tension correlates with coarse phase morphology and rapid phase coalescence. The addition of various potential compatibilizing agents to these binary blend systems results in lowered interfacial tension, finer and stabilized phase morphologies. The characteristics of different compatibilizing agents were compared for several of the blend systems. We also look at the influences of compatibilizing agents on mechanical properties of the blend systems. Some compatibilizing agents are able to produce substantial improvements in ultimate properties. 相似文献
Previous publications have shown that the stress-strain behavior, especially ductility, of some incompatible polymer blends are greatly improved by the addition of slurry produced chlorinated polyethylenes (CPE). This improvement is greatest for blends containing polyethylene and PVC. The most effective CPE's have some residual polyethylene crystallinity and may be described as block-like polymers with ethylene sequences and chlorine containing sequences. It is postulated that CPE addition improves the blend properties by increasing the adhesion between domains in the blend via interactions with the blend components. This hypothesis was explored by thermal analysis, dynamic mechanical testing, adhesion studies, and microscopy. It is concluded that the interaction of CPE with polyethylene derives from compatibility of rather long methylene sequences in CPE with the polyethylene which results in good adhesive bonding. The interaction of CPE with PVC may not be owing to segmental compatibility but simply good mutual adhesion between similar polar materials. There is no interaction or adhesion between CPE and polystyrene as would be expected. CPE addition to blends is accompanied by a decrease in component domain size. The relationship between CPE structure and its effectiveness as a blend modifier is discussed. 相似文献
Some mechanical properties of blends of polystyrene and low density polyethylene have been derived from stress-strain and impact measurements. The strength and impact properties are improved by adding a graft copolymer of polystyrene and low density polyethylene to the blends. It is assumed that the copolymer acts as an adhesive at the interface of the homopolymers thus decreasing the stress concentrations around the dispersed polymer particles at yield. The impact strength and modulus of polystyrene-graft copolymer blends could be made comparable to those of commercial rubber-modified impact polystyrenes by adjusting the fraction of copolymer in the blend. 相似文献
The present work studies the morphology in poly(ethylene-terephthalate)/polyethylene (PET/HDPE) polymer blends and its impact on blend properties. Mixing process in blend preparation is the important parameter for the type of obtained blend morphology and final blend properties, so two different mixing processes were used. In the first one, all components are mixed together while another one includes two step mixing procedure using two different types of masterbatch as compatibilizers for PET/HDPE system. Such blends can be considered in terms of PET polymer recycling in the presence of HDPE impurities in order to find suitable compatibilizers, which will enhance the interactions between these two polymers and represents the possible solution in recycling of heterogeneous polymer waste. The morphology of the studied PET/HDPE blends was inspected by scanning electron microscopy to examine the influence of the mixing process and various compositions on blends morphology, and interactions between PET and HDPE. The surface properties were characterized by contact angle measurements. The effect of the extrusion on the samples thermal behaviour was followed by DSC measurements. FTIR spectroscopy was used for the determination of interactions between blend constituents. It can be concluded that the type of mixing process and the carefully chosen compatibilizer are the important factors for obtaining the improved compatibility in PET/HDPE blends. 相似文献
Blends of polycarbonate/polystyrene (PC/PS), polycarbonate/polypropylene (PC/PP) and ternary blends of the three components (PC/PS/PP) were studied. Extrudate swell of the molten blends increased with increasing concentrations of the minor components and leveled off at characteristic blend compositions. These compositions corresponded to the limits of compatibility as judged by the onset of brittleness in tensile tests. Both PS and PP appear to have some limited practical compatibility with PC. The change in extrudate swell behavior with concentration may be a rapid and convenient test for the effective concentration limits of partially miscible polymers. 相似文献
Several pervaporation membranes, cellulose acetate (CA), polyvinylbutyral (PVB), poly(MMA-co-AA),MMA-AA-BA, CA/PVB blend and CA/poly(MMA-co-AA) blend, were prepared, and their pervaporation properties were evaluated by separation of methanol/C5 or methanol/MTBE (methyl tert-butyl ether). The results shows that the CA composite membrane has a high separation performance (flux Jmethanol = 350 g.m-2.h-1 and separation factor α>400) for methanol/C5 mixtures, and the pervaporation characteristics of MMA-AA-BA copolymer membranes changes with the ratio of copolymer. For CA/poly(MMA-co-AA) blend membrane, the pervaporation performance is improved in comparison with CA or poly(MMA-co-AA) membrane. From the experiment of CA/PVB blend membranes for methanol/MTBE mixture, it is found that the compatibility of blends may affect the separation features of blend membrane. 相似文献
Summary: Electrospinning of polymer blends offers the potential to prepare functional nanofibers for use in a variety of applications. This work focused on control of the internal morphology of nanofibers prepared by electrospinning polymer blends to obtain core‐sheath structures. Polybutadiene/polystyrene, poly(methylmethacrylate)/polystyrene, polybutadiene/poly(methylmethacrylate), polybutadiene/polycarbonate, polyaniline/polycarbonate, and poly(methylmethacrylate)/polycarbonate blends were electrospun from polymer solutions. It was found that the formation of core‐sheath structures depends on both thermodynamic and kinetic factors. Incompatibility and large solubility parameter difference of the two polymers is helpful for good phase separation, but not sufficient for the formation of core‐sheath structures. Kinetic factors, however, play a much more important role in the development of the nanofiber morphology. During the electrospinning process, the rapid solvent evaporation requires systems with high molecular mobility for the formation of core‐sheath structures. It was found that polymer blends with lower molecular weight tend to form core‐sheath structures rather than co‐continuous structures, as a result of their higher molecular mobility. Rheological factors also affect the internal phase morphology of nanofibers. It was observed the composition with higher viscosity was always located at the center and the composition with lower viscosity located outside.
TEM image of electrospun polybutadiene/polycarbonate nanofibers at 25/75 wt.‐% ratio after staining by osmium tetroxide. The dark regions are polybutadiene and the light region is polycarbonate. 相似文献
We measured the thermal conductivity of a polyethylene/polystyrene blend containing SEBS block copolymer, which has two components of polystyrene block and hydrogenated polybutadiene block, and discussed the effect of phase inversion on the thermal conductivity by observing the morphorogy of the blend. Further, we examined the applicability of the thermal conduction model for composites, which was proposed in our previous reports, to this blend system. By plotting the logarithm of the thermal conductivities of the blends vs. the weight content of polyethylene, it was found that the experimental data lie approximately on a straight line with an increase in polyethylene until the range of dual–phase continuity (phase inversion), and then the data move on another straight line beyond the range of dual–phase continuity. Thus, our model to explain the thermal conductivity of the polymer blend was proved. Further, both coefficients A and B in our model took linear relations with the weight content of the block copolymer, and the model was, thus, more strongly confirmed to be applicable to thermal conductivity of polymer blends. 相似文献