Phase Morphology Of Polymer Blends Research Articles

The effects of molecular weight and supercritical CO2 on the phase morphology of organic solvent free porous scaffolds

Porous poly(ε-caprolactone) (PCL) scaffolds were prepared by extracting the poly(ethylene oxide) (PEO) phase from co-continuous PCL/PEO blends, which were annealed in supercritical carbon dioxide (scCO2). It was found that the coarsening temperature of PCL/PEO blend in scCO2 is lower than that in atmosphere, which indicated that the scCO2 could be used as an effective tool for morphology control. The effects of molecular weight of PEO, annealing time, temperature and pressure on the phase morphology of polymer blends have been systematically studied. The average pore size of PCL porous scaffold increases with the increase of annealing time, temperature and pressure. The coarsening effect of the PCL/PEO blends decreases with increasing molecular weight of PEO. The average pore size is in the range of 10–130 μm with high interconnectivity. In addition, the preparation of scaffold is organic solvent free preparation for the reason that PEO and PEG are water-soluble polymers.

Structure and properties of compatibilized recycled polypropylene/recycled polyamide 12 blends with cellulose fibers addition

This research was aimed to develop engineering thermoplastic composites based on recycled plastics and cellulose fibers in order to provide eco‐friendly sustainable parts that meet certain requirements for automotive industry and to use recycled plastics for economic benefits. The composite networks were prepared using recycled PP, recycled PA12, two different maleic anhydride functionalized polypropylenes (PP‐g‐MA) and cellulose fiber. The loading of cellulose fibers was varied between 5 and 20 wt%. Based on the results of mechanical tests a substantial improvement was detected in terms of tensile and flexural modulus which showed that cellulose fibers could be used for reinforcing of stiffness of recycled polymer blends. It was also noticed that using PP‐g‐MA type of compatibilizers played an important role on the mechanical characteristics of polymer blends. The incorporation of cellulose into the compatibilized PP/PA12 blends resulted in higher storage modulus and shear viscosities than those of neat PP, PA12, and PP/PA12 blends at low frequencies and shear rates, respectively. Phase morphology of polymer blends and cellulose fibers‐filled composites became more fine, uniform, and stable with addition of PP‐g‐MA. Fourier transform infra‐red (FTIR) was used to confirm the interaction observed. It is obvious that cellulose reinforced, compatibilized recycled polymer blends can be a good alternative where better mechanical properties under high temperature are required in the automotive industry. This opportunity will help to reduce the cost and the effects of environmental issues. POLYM. COMPOS., 39:3556–3563, 2018. © 2017 Society of Plastics Engineers

Effect of migration of layered nanoparticles during melt blending on the phase morphology of poly (ethylene terephthalate)/polyamide 6/montmorillonite ternary nanocomposites

Migration and selective localization of layered nanoparticles during melt compounding have great influence on phase morphology of polymer blends.

Ultrasonic characterization of phase morphology of high density polyethylene/polyamide 6 blend melts

The high density polyethylene (HDPE) and polyamide 6 (PA6) blend melts with a droplet-matrix microstructure were investigated using ultrasonic diagnosis system. The blend composition, as well as the particle size of the dispersed PA6 phase controlled by adding various amounts of the reactive compatibilizer HDPE grafted with maleic anhydride (HDPE-g-MAH), was, respectively, correlated with the ultrasonic velocity and attenuation. The results showed that ultrasonic velocity was insensitive to the particle size but varied linearly with the blend composition. However, the decrease of ultrasonic attenuation with the increasing content of HDPE-g-MAH suggested that the attenuation depended greatly on the particle size. Further investigations revealed that there was a good linear relationship between the excess attenuation and the size of the dispersed phase. Our results present that ultrasonic technique may be served as a promising technique for exploring phase morphology of polymer blends during processing. POLYM. ENG. SCI., 2012. © 2011 Society of Plastics Engineers

Real‐time ultrasonic monitoring of the injection‐molding process

AbstractIn this study, a noninvasive and nondestructive ultrasonic technique has been used to monitor the polymer injection‐molding process in an attempt to establish a fundamental understanding of the processing/morphology/ultrasonic signal relationships. The ultrasonic technique not only can provide information on solidification affected by various temperatures and pressures but also can reflect the evolution of the crystal morphology and phase morphology of polymer blends. In addition, the periodic vibration of the dynamic‐packing injection‐molding process, in which the melt is forced to move repeatedly in a chamber by two pistons that move reversibly with the same frequency as the solidification progressively occurs from the mold wall to the molding core part, can also be monitored with the ultrasonic velocity and attenuation. Our results indicate that the ultrasonic technique is sensitive and promising for the real‐time monitoring of the injection‐molding process. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

Use of Block Copolymer-Stabilized Cadmium Sulfide Quantum Dots as Novel Tracers for Laser Scanning Confocal Fluorescence Imaging of Blend Morphology in Polystyrene/Poly(methyl methacrylate) Films

This paper describes the first use of polymer-coated quantum dots (QDs) as fluorescent tracers for LSCFM imaging of phase morphology in polymer blends. Cadmium sulfide (CdS) QDs stabilized at the surface with a PS-b-PAA block copolymer are shown to be well dispersed via their polystyrene (PS) brush layer in the PS phase of solvent-cast 40/60 (w/w) PS/PMMA blends. The QDs are excluded from the PMMA phase, providing excellent fluorescence contrast for LSCFM imaging of the phase-separated blends. The presence of PS-b-PAA-stabilized QDs does not appear to affect the blend morphology, since the observed morphologies are the same when the percentage of QDs within the PS phase is varied from 10 to 50 wt %. These QD fluorescent tracers are used to characterize several aspects of blend morphology in solvent-cast 40/60 PS/PMMA blends containing PS homopolymer with either 100 (low molecular weight) or 1250 (high molecular weight) repeat units. In the PS(1250)/PMMA blends, a percolating distribution of PMMA droplets (2-25 mum) in a PS matrix is observed in the bulk, and a distinct inversion in the continuous phase is found near the glass substrate. In the PS(100)/PMMA blends, a "phase-in-phase" morphology is found, consisting of large PS domains (20-100 mum) dispersed in a PMMA continuous phase and small PMMA domains (1-2 mum) scattered throughout the larger PS droplets. The observed change in blend structure is attributed to a lower interfacial tension for the lower molecular weight PS.

Study on Fractal Character of High Impact Polystyrene with Poly(cis‐butadiene) Rubber Partly Miscible Blends by Fractal Measure Relations and Box‐Counting Methods

Phase formation and evolution of high‐impact polystyrene/poly(cis‐butadiene) rubber (HIPS/PcBR) blends during melting and mixing processes were investigated by scanning electron micrographs analysis. The diameter, d p , was used to describe the evolution of the phase morphology of HIPS/PcBR blends during mixing. Scale functions, S N (r) and S M (r), were defined to confirm the self‐similarity of the phase morphology. The plots of S N (r)/S N (r) m [the maximum of S N (r)] vs. r/r m (the maximum of r) and S M (r)/S M (r) m [the maximum of S M (r)] vs. r/r m showed the phase morphology had self‐similarity. Furthermore, the fractal dimension, D, of different HIPS/PcBR blends was calculated by two different methods (fractal measure relations and box‐counting methods). The results showed that the fractal dimension was an effective parameter for study of the phase morphology of polymer blends.

Comparative AFM and TEM investigation of the morphology of nylon6-rubber blends

In the present paper, blends of nylon6 with rubber were cut by means of microtoming for the AFM investigation of bulk morphology using phase contrast imaging. This investigation was compared to the results of a TEM analysis. The cutting procedure used in the preparation of the samples did not affect the morphology of the rubber particles, since the topography of the area analyzed did not affect the contrast between hard and soft phases in AFM phase contrast imaging. The values of particle average diameter and particle aspect ratio of rubber particles in the nylon6 matrix are similar in AFM and TEM analyses, showing that both techniques can be used to distinguish phase morphology of polymer blends. It was also possible to detect an elongation of the rubber particles in the nylon6/SEBS-g-MA sample, caused by flow direction of the blend injection process.

Effect of Interfacial Tension on the Formation of the Gradient Morphology in Polymer Blends

In order to investigate the effect of interfacial tension on the formation of gradient phase morphology in polymer blends, a saponification reaction was carried out in this study to obtain several kinds of EVA with different contents of -OH groups. These EVAs with different -OH contents, namely with different polarities, were then blended with PP, and thus a series of PP/EVA blends with different interfacial tensions was obtained. The same initial droplet size could be obtained for PP/EVA blends with different interfacial tensions during compounding through adjusting the degree of saponification of EVA. It was found that all these PP/EVA blends could form a gradient morphology in the vertical section of the samples as PP/EVAc blends. Using a computer image analyzer, the vertical distributions of the dispersed droplet size and the EVAc component in each blend were determined. The results showed that the EVA droplet size and the EVA component increased in the vicinity of the sample surface with increasing interfacial tension of the blends; i.e., the greater the interfacial tension between PP and EVA, the larger the gradient tendency in the blend.

Phase morphology of polymer blends: 2. SEM observation by secondary and backscattered electrons from microtomed and stained surface

A recently developed scanning electron microscopy (SEM) technique, which consists of the preparation of a microtomed flat surface, staining with OsO 4 or RuO 4, and compositional contrast observation using backscattered electrons, was applied for high impact polystyrene and propylene-ethylene block copolymer. A clear contrast was obtained for both polymers. By minor revision, i.e. by employing the secondary electron image under a low accelerating voltage, a much better contrast was observed.

Morphology development in polymer blends

AbstractThe major morphological changes during polymer blending occur during the initial softening stage. This work explains the evolution of phase morphology of polymer blends from pellets to submicron particles in a co‐rotating twin‐screw extruder. The extruder was opened and blend samples were taken along its length. The major phase component was extracted by means of a selective solvent so that the dispersed phase morphology could be viewed directly by using scanning electron microscopy. The two systems studied were 80:20 polystyrene/amorphous polyamide and 80:20 polystyrene/polypropylene. In both systems, the initial morphology consisted of sheets of dispersed phase. Holes form in the sheets, and these holes grow as a result of interfacial tension forces until they coalesce with each other, forming thin ligaments. These fluid ligaments are unstable and break up via mixer shear forces. Very large changes in dispersed phase size are observed during the softening stage. The particle size changes less after the polymers are completely melted. The extruder results are compared to results from a batch mixer. The same dispersed phase sheeting mechanism is seen in the initial morphology in the batch mixer and the breakup of the dispersed phase domains parallels the breakup seen in the extruder.

Phase morphology of polymer blends: scanning electron microscope observation by backscattering from a microtomed and stained surface

A new electron microscopy technique was used to observe two-phase morphology in polymer blends. It consisted of preparing a flat specimen surface by microtoming, staining the unsaturated domains with OsO 4, and scanning electron microscope observation of the composition images using backscattered electrons. The new technique was applied to the melt blends of polypropylene (PP)/polybutadiene and PP/ethylene-propylene-diene rubber systems. Compared with conventional scanning electron microscope observation using secondary electron imaging for fractured surfaces, the new technique yielded a much clearer phase contrast.