Dispersion Of Minor Phase Research Articles

Semi-interpenetrating polymer networks prepared from in situ cationic polymerization of bio-based tung oil with biodegradable polycaprolactone

In situ cationic polymerization of bio-based tung oil in the presence of poly(e-caprolactone), a crystallizable, biodegradable, and biocompatible polymer, was performed to produce novel semi-interpenetrating polymer networks (IPNs). The macromolecular structure and properties of these IPNs were investigated as a function of composition using small amplitude oscillatory shear flow rheology, FT-IR spectroscopy, dynamic mechanical analysis (DMA), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and scanning electron microscopy (SEM). This versatile and low-cost strategy successfully produced bio-polymer blends with various degrees of miscibility, morphology, and crystallization behavior. The carbon–carbon double bonds in tung oil were consumed quickly after adding the cationic initiator to form a three-dimensional (3D) crosslinked network in all measured samples as confirmed by FT-IR. A complete miscible structure with a single glass transition temperature and one-phase morphology was observed for a tung oil/PCL 90/10 blend. On the other hand, a two-phase structure exhibiting a nanoscale morphology of the dispersed minor phase as small as 100 nm was observed for blends with 20 and 30 wt% PCL. For a 50 wt% PCL blend, an interconnected, co-continuous microstructure of the two phases was also detected. DMA and DSC measurements confirmed the miscibility (or partial miscibility) of the blends by following the changes in the glass transitions of phases as a function of the composition. The value of the elastic modulus (E′) in the glassy state as obtained from the DMA measurements was strongly dependent on the composition, reaching a maximum at 20 wt% PCL.

Temperature-dependent compatibilizing effect of graphene oxide as a compatibilizer for immiscible polymer blends

We demonstrated the compatibilizing effect of graphene oxide (GO) in the immiscible poly(methyl methacrylate)/polystyrene (PMMA/PS, 80/20) blend and showed that such a compatibilizing effect was affected by the processing temperature. For the blends prepared at a relatively low temperature (190 °C), the incorporation of 0.5 wt% of GO results in a dramatic reduction in the domain diameter of dispersed minor phase (PS), indicating that GO is an effective compatibilizer. Increasing the processing temperature decreases the dispersed phase size reduction, illustrating that the compatibilizing effect of GO is adverse to processing temperature. The characterization results including the changes in chemical composition of GO and morphologies evolution of blends at different annealing temperatures reveal that this temperature-dependent compatibilizing effect should be attributed to the in situ thermal reduction of GO during the melt processing, which breaks the hydrophilicity-hydrophobicity balance of GO and renders it more hydrophobic. A comparative experiment shows that chemically reduced GO has almost no compatibilizing effect for PMMA/PS blends, which further confirms the proposed mechanism. In addition, the GO-compatibilized blends exhibit great improvement in the mechanical properties than uncompatibilized blends.

Compatibilization of recycled poly(ethylene terephthalate) and polypropylene blends: Effect of compatibilization on blend toughness, dispersion of minor phase, and thermal stability

AbstractBlending of recycled polyethylene terephthalate (RPET) from waste bottles with polypropylene (PP) was performed in an attempt to enhance the processability of RPET. The idea of blending RPET with PP sprouted from the intention of recycling PET bottles together with their PP‐based caps. Therefore, preliminary blending of RPET with neat PP (RPET/PP) was performed at various PP and compatibilizer contents. Morphological analyses on the extruded pellets of uncompatibilized blends indicate that the PP particle size and state of dispersion at skin and core regions were vastly different. The particles at the skin were at least 10 times smaller than that at the core although the size distribution was very wide. With the incorporation of just 5 phr of compatibilizer, the particles at the core region became significantly smaller and appeared to emulate that of the skin region. Furthermore, the overall homogeneity of the blends was vastly improved irrespective of PP content in the blend. The reduction in particle size and improved homogeneity inherently reduced stress concentration points and enhanced the mechanical performance of the blends. More importantly, the incorporation of PP into RPET significantly increased the degradation temperature of the blends, provided the dispersion of PP phase in RPET was excellent. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

Compatibilization of Immiscible Polymer Blends Using Graphene Oxide Sheets

By taking the advantage of the unique amphiphilic structure of graphene oxide sheets (GOSs), we develop here a new and effective strategy for compatibilizing immiscible polymer blends. With the incorporation of only 0.5 wt % GOSs into immiscible polyamide/polyphenylene oxide (PA/PPO, 90/10) blends, the droplet diameter of the dispersed minor phase (PPO) is dramatically reduced by more than 1 order of magnitude, indicating a largely improved compatibility in the GOS-filled polymer blends. As a result, the ductility of GOS-compatibilized polymer blends is notably elevated. The compatibilizing effect of GOSs should be due to the fact that GOSs can exhibit strong interactions with both PA and PPO phases, thus minimizing their interfacial tension. Moreover, unlike traditional copolymer compatibilizers, GOSs can also act as reinforcing fillers in polymer blends, thus remarkably enhancing their mechanical strength and thermal stability. Considering the inexpensive sources (graphite powders) and extraordinary properties of GOSs, this work may open up opportunities to produce new compatibilizers that are of great interest in the industrial field.

Properties and morphology of recycled poly(ethylene terephthalate)/bisphenol a polycarbonate/poly(styrene‐b‐(ethylene‐co‐butylene)‐b‐styrene) blends by low‐temperature solid‐state extrusion

AbstractAmong the various methods available for recycling plastics waste, blending technology is a straightforward and relatively simple method for recycling. In this paper, a new blending technology, low‐temperature solid‐state extrusion, was discussed. Several recycled poly(terephthalate ethylene)/bisphenol a polycarbonate/poly(styrene‐b‐(ethylene‐co‐butylene)‐b‐styrene) blends (R‐PET/PC/SEBS blends) have been prepared by this technology. The results show that thermal and hydrolytic degradation of R‐PET is improved when extruding temperature was between the glass transition temperature (Tg) and cold crystallization temperature (Tcc). Elongation at break and notched impact strength were increased evidently, from 15.9% to 103.6, and from 8.6 kJ/m2 to 20.4 kJ/m2, respectively. The appropriate rotating speed of screws was between 100 and 150 rpm. At the same time, the appropriate rotating speed of the screws brings a suitable shear viscosity ratio of R‐PET and PC, which is of advantage to blending of R‐PET and PC together with SEBS. Dispersion of minor phase, PC and SEBS, became finer and smaller, to about 1 µm. Chain extender, Methylenediphenyl diisocyanate (MDI) can react with the end‐carboxyl group and end‐hydroxyl group of R‐PET. FT‐IR spectra testified that the reactions have been happened in the extruding process. A chain extending reaction not only increased the molecular weight of PET and PC, but also can synthesize PET‐g‐PC copolymer to act as a reactive compatilizer. An SEM micrograph shows that a micro‐fiber structure of PET was formed in the blend sample. Copyright © 2007 John Wiley & Sons, Ltd.

Pore structure and glass transition temperature of nanoporous poly(ether imide)

AbstractThe effect of nanopores on the glass transition temperature (Tg) of poly(ether imide) was studied with differential scanning calorimetry. Nanoporous poly(ether imide) samples were obtained through the phase separation of immiscible blends of poly(ether imide) and polycaprolactone diol and by the removal of the dispersed minor phase domains with a selective solvent. Microscopy and statistical methods were used to characterize the pore structure and obtain the pore structure parameters. The pore size was found to depend on the processing time and the initial blend composition, mainly because of phase‐coarsening kinetics. A decrease in Tg was observed in the nanoporous poly(ether imide) in comparison with the bulk samples. The change in Tg was strongly influenced by the pore structure and was explained by the percolation theory. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 3546–3552, 2006

Morphology and Properties of Novel Blends Prepared from Simultaneous In Situ Polymerization and Compatibilization of Macrocyclic Carbonates and Maleated Poly(propylene)

AbstractSummary: Nanoscale polymer blend morphologies, with a dispersed minor phase as small as 50 nm, have been prepared via the in situ polymerization of macrocyclic carbonates in the presence of a maleic anhydride poly(propylene) (mPP). This simple, versatile, low cost strategy successfully produced a well‐defined, stable two phase nanoscale morphology with a considerable improvement in the ultimate mechanical properties and strong resistance to hydrocarbon solvents such as methylene chloride. The effect of blend composition on the rate of polymerization of the macrocyclic carbonates was studied by considering the increase in torque during the mixing process in the batch mixer. The polymerization rate decreased considerably with increasing concentration of mPP in the blend due to the formation of graft copolymer of polycarbonate‐g‐poly(propylene) (PC‐g‐PP). The viscoelastic behavior of the pure polymer components was found to play no role in controlling the blend morphology and size of the dispersed nanoscale particles. The blend morphology could be controlled by the compatibilization of the blend components, possibly via in situ formation of a graft copolymer. In addition, the blend morphology was strongly influenced by the value of the rotation speed (rpm) or shear rate encountered during the processing of the blends, i.e., the larger the rpm value, the finer the observed blend morphology. Both DSC and DMA data showed evidence of partial miscibility of the polymer blend components. In addition, the DMA data confirmed a preferential dissolution of mPP in polycarbonate (PC) instead of dissolution of PC in mPP as evidenced by the shift of the α‐relaxation process of the PC‐rich phase to lower temperatures while the α‐relaxation process of the mPP was relatively unaffected regardless of the PC composition. The percentage of mPP dissolved in PC was evaluated from the reduction in the Tg value (obtained from DSC data) of PC in the blend using the Fox equation and was found to be consistent with the DMA data and preferential dissolution of mPP in PC.STEM photograph of mPP/PC = 10/90 blend. The sample was prepared at 225 °C and 200 rpm.magnified imageSTEM photograph of mPP/PC = 10/90 blend. The sample was prepared at 225 °C and 200 rpm.

In‐Situ Fibrillation of Ny6/6 During Processing of PP/Ny6/6 Blends, Slightly Below the Ny6/6 Melting Temperature

The focus of the present research is on in‐situ fibrillation of a dispersed minor phase during processing of binary immiscible polymer blends. This structured morphology is attained by extrusion compounding and injection molding at a temperature slightly below the melting temperature (Tm) of the dispersed phase, yet, well above the melting temperature of the matrix. Binary polypropylene/nylon‐6/6 [PP/Ny] blends were compounded (twin screw extruder) and processed (injection molding) both slightly below and above the Ny Tm under different blending conditions. To study the processing‐structure‐property relationships the blends were characterized using scanning electron microscopy (SEM), high resolution scanning electron microscopy (HRSEM), differential scanning calorimetry (DSC), X‐ray diffraction (XRD), and tensile mechanical behavior. Compounding and processing slightly below the Ny Tm resulted in Ny fibrils formation throughout the specimens' volume, as opposed to spherical/ellipsoidal Ny particles observed in the melt processed blends. The initial extrusion‐compounding stage has an important role in attaining Ny fibril morphology in the subsequent injection molding step, where further fibrillation takes place. The additional stretching of Ny fibrils results in the formation of highly ordered Ny crystals, having a higher melting temperature than the regular Ny crystallized from the melt, and some degree of crystal orientation. The morphology of the binary blends can be explained by the “capillary instability” mechanism and examining the relation between the time required for fibril breakup and the residence time in a die. The Ny fibrils' orientation along the applied load direction contribute to enhanced strength and modulus displayed by the 260°C injection‐molded blend compared with the blends molded at the other temperatures.

Auger spectroscopy study of MgLi melt affected carbon/pyrocarbon fibres

Mg–12wt.% Li matrix composite reinforced with T300 carbon fibres coated with pyrolytic carbon (∼100 nm) was manufactured by the infiltration of the carbon fibre bundle with MgLi melt. The fibre/matrix chemistry was studied by means of in situ Auger electron spectroscopy of the fibre jacket and the fibre cross-fracture in ultra-high vacuum broken composite bars. The fibre bulk attack with lithium is concluded wherein C(KVV) lineshape indicates that lithium carbide is the only reaction product, and its distribution in the fibre bulk is quite uniform. Magnesium penetrates also the fibre bulk but its role in the fibre attack is marginal. It is assumed that lithium carbide is formed as a dispersed minor phase in the fibre bulk via decomposition of intermediate lithium intercalation products.

Polystyrene‐graft‐acrylic acid as compatibilizer of polystyrene/nylon 6,6 blends

AbstractPreliminary investigations to study the feasibility of using polystyrene grafted with acrylic acid to blend polystyrene (PS) and nylon 6,6 (N66) have been done. The graft copolymer (PS‐g‐AA) was synthesized by reacting polystyrene with acrylic acid in the presence of a free radical initiator using the solid phase graft copolymerization technique. Binary blends of N66/PS and N66/PS‐g‐AA were synthesized by melt mixing. The formation of a (PS‐g‐AA)‐co‐N66 copolymer during the blend preparation has been desired. The blend morphologies were observed by scanning electron microscopy (SEM). Significant reductions in the domain sizes of the dispersed minor phase were observed when PS‐g‐AA instead of PS was incorporated into the blend. The tensile properties of the blends were investigated. The belnds containing PS‐g‐AA were found to be stiffer (higher modulus) and stronger (higher tensile strength) as compared to the blends containing PS. These results are due to the better miscibility and adhesion between nylon 6,6 and the graft copolymer. The results of the rheological measurement of these blends further supports the above result and also indicates an increase in the molecular weight distribution (MWD) of the blend when polystyrene was replaced by the graft copolymer. This increase in the MWD of the compatibilized blend can be attributed to above assumed copolymer formation between the graft copolymer and nylon 6,6 due to the reaction between the carbonyl group of the acrylic acid and the amide and the terminal amine groups of nylon 6,6.

Structure formation during polymer blend flows

AbstractThe structure formation processes that occur during the flow of dilute blends of high density polyethylene (HDPE) or polypropylene (PP) In a linear low density polyethylene (LLDPE) carrier phase have been studied. Due to low surface tensions, high deformations of the dispersed minor phase can be induced under slow flow conditions leading to the formation of slender filaments. Measurements on a slit die, having a large, converging flow entrance region, demonstrate that the mechanism for filament formation is droplet bursting, yielding growing tails during shear flow, or, unsteady drop elongation during extensional flow. Tail growth can be modeled as the flow of a slightly tapering cylinder in a fluid of different viscosity, For dispersed to carrier phase viscosity ratios greater than unity, extensional flow occurs in the tail phase, which can induce oriented crystallization. For ratios less than unity, the flow is compressive, which. Inhibits crystallization. Drop deformation and crystallization in the converging flow entrance region is greatly enhanced by the extensional flow, and droplet growth can be described by a model assuming a time‐dependent, planar, extensional flow field. Data for birefringence and melting points of as‐crystallized fibers are also presented and discussed.

An experimental study of oxygen transport in dry rocks and related kinetic phenomena

Several series of experiments were carried out at 1 GPa and 900°–1100° in which grain boundary chemical diffusion of oxygen in dry quartzite and dunite was characterized by use of “indicator mineral” techniques. Most experiments involved mixing a small amount of Fe2O3 with coarse quartz or olivine powder, placing the mixture in an iron container, pressurizing in a piston‐cylinder apparatus, and heating rapidly to the desired run temperature. In response to the large gradient in oxygen fugacity resulting from the juxtaposition of iron metal (i.e., the container) with Fe2O3 disseminated through the sample, oxygen transport along quartz or olivine grain boundaries took place, causing reduction of ferric iron in regions of the sample nearest the container (producing wüstite in the dunite experiments and fayalite in those on quartz). The flux of oxygen, and hence the diffusivity, could be calculated from the width of the observed reduction zone. Variations on the method just described included use of CuO rather than Fe2O3 as the “indicator mineral,” use of graphite rather than iron as the container, and placement of the Fe2O3 as a single pellet at the center of the dunite or quartzite sample rather than as a dispersed minor phase. For the dispersed‐Fe2O3 experiments on dunite at 1000° and 1100°C, the width of the reduced (wüstite‐bearing) zone was found to be generally proportional to the square root of run duration, in accordance with a diffusion‐controlled transport/reduction process. At 900°, however, this relation does not hold, and the data suggest vapor phase transport of oxygen prior to closure of sample porosity. All experiments on quartzite (900°–1100°) were plagued by the same problem, but in this case, sufficiently long experiment durations eventually resulted in no further measurable oxygen transport, demonstrating that well‐annealed quartzite is impermeable to oxygen at the run conditions. The net outcome of the experiments is a bulk grain boundary diffusivity for oxygen in dunite given approximately by D = 106exp (−355,500/RT) (D in cm2/s; R in J/deg mol). Values for quartzite are too low to measure by the techniques attempted. The information can be used to argue that heterogeneities in oxygen fugacity on the scale of centimeters to meters can be maintained indefinitely in fluid‐absent, high‐grade rocks of the continental crust, but similar features in a fluid‐absent mantle would be quickly erased.