Phase Structure Of Blends Research Articles

Blends of polydimethylsiloxane-based polyurethane and poly (propylene glycol)-based polyurethane with co-continuous structures: Morphology evolution, synergistic effects and application in strain sensors

Blending is an effective way to improve properties of rubbers and develop new materials, so more than 75 % of the rubber consumption in the world is rubber blend. However, blending of thermoplastic elastomers has not yet been emphasized, and few successful examples have been reported. The main challenge for blend systems is compatibility of two components. Herein, a series of (polydimethylsiloxane-based PU)-g-(poly (propylene glycol)-based PU) ((PDMS-PU)-g-(PPG-PU)) graft copolymers with different graft chain lengths and hard segment contents (HSC) were synthesized and utilized as compatibilizers of PDMS-PU/PPG-PU blends. The influence of the structure of compatibilizers on the morphology of blends was investigated, and the compatibilization mechanism was proposed. With the solubilization, the phase structure of blends transforms from “droplet-in-matrix” morphologies to co-continuous ones, and the average size of PPG-PU dispersed phase decreases from 3.5 ± 0.45 μm to 230 ± 60 nm. This is the first time that thermoplastic PDMS-PU/PPG-PU blends with co-continuous structures have been successfully prepared. The properties of blends exhibit synergistic effects. For example, they show high tensile strength of PPG-PU in mechanical properties and unique properties of PDMS in dynamic mechanical properties, weather resistance, water resistance and biocompatibility. In addition, strain sensors were fabricated by introducing carbon nanotubes (CNTs) into the blends, which demonstrated remarkable sensing capability for diverse human body motions.

Ductile and biodegradable poly (lactic acid) matrix film with layered structure

Polylactide (PLA), as a biodegradable packing material, has attracted plenty of attention. However, some problems still limit the application of PLA in packing industry such as the inherent brittleness and low crack propagation resistance. In order to overcome these challenges, we blended PLA with a reactive toughening agent (Ethylene-Acrylic ester-Glycidyl methacrylate terpolymer) during extrusion and film processing. The glycidyl methacrylate groups in toughening agent offered some sites to react with COOH and OH groups of PLA thus leaded to a great interfacial compatibility. The proper compatibility was the premise of adjusting the phase structure of blend and film based on different processing methods. The blend had a sea-island structure after melting extrusion and heat pressed technologies while film formed annular layer structure after film blowing. The structure determined properties. Both the toughness and melt strength of blends had been improved. Moreover, it was interesting to found that tear strength of film with 10% toughening agent dramatically increased to 197.8 KN/m and 137.7 KN/m in the transverse direction (TD) and in the machine direction (MD), respectively. Besides, the elongation at break of film could reach 242.2% in MD. This work exhibited that phase morphology was significant for mechanical performances.

Investigation of miscibility and phase structure of a novel blend of poly(lactic acid) (PLA)/acrylic rubber (ACM) and its nanocomposite with nanosilica

ABSTRACTIn this work, a novel polymer blend containing poly(lactic acid) (PLA) as a biocompatible and biodegradable thermoplastic and acrylic rubber (ACM) is prepared and the miscibility and phase structure of the blend and its nanocomposite (PLA/ACM/nanosilica) are investigated through theoretical and experimental methods. To predict the phase diagram of the blend, a compressible regular solution model was employed, in which an upper critical solution temperature was observed. The model predicted that PLA/ACM blends are immiscible over the whole composition range at temperatures below 260 °C. Performing scanning force microscopy on the blend showed phase separated structures for the blends containing different amounts of the PLA and ACM. This was in accordance with the results of dynamic mechanical analysis, which revealed two distinct glass transition temperatures for the studied blends. The effect of nanometer sized silica particle on morphology and rheological properties of these blends was also investigated. Scanning force microscopy results showed much reduction of droplet size in the blends containing 2 wt % nanosilica. This was attributed to the suppression effect of nanosilica on the droplets coalescences. Rheological measurements confirmed the interaction of both components with the silica nanofiller. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 45499.

Effect of Attapulgite Nanorods and Calcium Sulfate Microwhiskers on the Reaction-Induced Phase Separation of Epoxy/PES Blends

The influence of two kinds of mesoscale inorganic rod fillers, nanoscale attapulgite and micron-sized CaSO4whisker, on the reaction-induced phase separation of epoxy/aromatic amine/poly- (ether sulfone) (PES) blends has been investigated by optical microscopy (OM), scanning electron microscopy (SEM), and time resolved light scattering (TRLS). By varying the PES concentration and curing temperature, we found that the incorporation of attapulgite and CaSO4had dramatic impact on the phase separation process and the final phase morphology of blends. In blends at higher content than critical concentration, the process of phase separation was retarded by the incorporation of nanoscale fillers but accelerated by that of the micron-sized fillers, mainly due to the enhanced viscoelastic effect and the preferential wettable effect, respectively. Meanwhile both mesoscale fillers could change the cocontinuous phase structure of blends with lower PES content than critical concentration into PES-rich dispersed structure due to the surface affinity of fillers to epoxy matrix.

Nanophase-Separated Structures of Hydrogen-Bonded Interpolymer Complexes of AB Block Copolymer/C Homopolymer in Thin Film with Variable Blending Composition upon Solvent Annealing

The self-assembly behavior of hydrogen-bonded interpolymer complexes of poly(styrene)-b-poly(4-vinylpyridine) (PS-b-P4VP)/poly(4,4′-oxydiphenylenepyrome llitamic) acid (POAA) in thin films with variable POAA weight content upon solvent annealing in benzene/N-methy1-2-pyrrolidone (NMP) mixture vapor was investigated. It was found that when the PS-b-P4VP/POAA thin film blends were annealed in a benzene/NMP (0.97/0.03, in volume) mixture vapor, the thin film blends with a high POAA wt%, above 40%, exhibited a mixture of spherical and rod-like microphase-separated structure, while the thin film blends with a POAA wt% lower than 40% were homogenous. For the blends in thin films with a POAA wt% of less than 40%, the benzene/NMP (0.97/0.03, in volume) vapor was highly miscible with both the PS blocks and P4VP/POAA complexes, which led to decrease of segregated repulsion between the two components and no obvious microphase separation could be achieved. When the PS-b-P4VP/POAA blends in thin films with POAA wt% of 20%, 50%, and 70% were annealed in benzene/NMP with a volume ratio of 0.99/0.01, obvious microphase separation was observed for all films due to increasing PS-selectivity of the mixture vapor. However, the phase structure of blends in thin film with POAA wt% of 50% and 70% consisted of PS microdomains dispersed within the P4VP/POAA matrix, while the blends in thin film with POAA wt% of 20% revealed an opposite phase structure with P4VP/POAA microdomains surrounded by the PS matrix. The transition could be attributed to the increasing free volume of PS domains relative to that of P4VP/POAA due to swelling by benzene vapor during annealing.

Study on phase structure and evolution of PP/PEOc blends during heat preservation process under quiescent condition

The phase structure and evolution of polypropylene (PP)/poly(ethylene-1- octene) copolymer (PEOc) blends during heat preservation process under quiescent condition were studied using scanning electron microscopy (SEM). The structure parameters, such as the average area diameter dp, characteristic length L, and average characteristic length Lm, of the dispersed phase in PP/ PEOc blends were calculated by pattern analysis of SEM images. Moreover, the potential fractal behavior of the phase structure and morphology of polymer blends during the process was discussed. The histograms of P(L(t)/Lm) obtained at various time fell on a master curve, demonstrating the self-similar growth of the phase structure of the blends during heat preservation process.

Phase Structure of PVC/MBS Blends by Small Angle X-ray Scattering

The phase structure of blends consisting of polyvinyl chloride (PVC) and methyl methacrylate—butadiene—styrene graft copolymer (MBS) are examined by small-angle-X-ray scattering (SAXS). The interface layer thickness (σ), correlation distance (ac), and interface layer specific surface area (Ssp) are calculated using Debye—Bueche's statistical theory. The results show that the grafted sequence of styrene or methyl methacrylate to butadiene—styrene copolymer have significant influence on the values of σ, ac, and Ssp. The σ-value of PVC/MBS in which styrene is first grafted in MBS is about 5 nm larger than that of methyl methacrylate (MMA) that is first grafted in MBS.

Morphological development and rheological changes of phenoxy/SAN blends duringin-situ polymerization

This article reports the results of an investigation into the time-dependent morphological and rheological changes that accompany the in-situ polymerization of blends composed of poly(hydroxyether of bisphenol A) (phenoxy) and poly(styrene-co-acrylonitrile) (SAN). The rheological behavior was monitored continuously during the in-situ polymerization, whereas the miscibility and phase structure of blends formed in situ were examined at discrete stages of polymerization by differential scanning calorimetry and transmission electron microscopy. In the blend with 30 wt % SAN, a co-continuous blend morphology was associated with gradual changes in the dynamic moduli, suggesting that phase separation proceeded by spinodal decomposition (SD). In contrast, phenoxy-rich dispersions were uniformly dispersed in a continuous SAN-rich matrix in the blend with 50 wt % SAN, and the corresponding rheological signature revealed a sharp initial increase in the dynamic moduli, followed by slower growth after long times, indicative of phase separation via nucleation and growth (NG). The rheological property changes are closely related to morphology development and mechanisms of phase separation induced duringin-situ polymerization. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 2614–2619, 2007

High-density polyethylene/cycloolefin copolymer blends, part 2: Nonlinear tensile creep

Viscoelastic behavior of most polymeric materials is nonlinear over a major portion of the interval of their response to external forces. The phenomenological theory of viscoelasticity, based on the assumption that molecular (segmental) motions are controlled by available fractional free volume f, was found adequate for description of the nonlinear tensile creep, implementation of the time–strain superposition and prediction of the nonlinear creep of studied blends. As f of thermoplastics with Poisson's ratio smaller than 0.5 rises proportionally to tensile strain, advancing creep accounts for shortening of retardation times. Consequently, the shift factor along the internal time scale in the time–strain superposition is not constant for a creep curve, but monotonically rises with the elapsed creep time. Compliance curves for various stresses obey fairly well the internal time–strain superposition forming a generalized compliance curve related to an iso-free volume reference state. The predictive format for the blend compliance is based on the parameters characterizing the creep of parent polymers, data on the phase structure of blends obtained from the two-parameter equivalent box model and modified equations of the percolation theory. Applicability of the proposed format is demonstrated on a series of blends of high-density polyethylene with creep-resistant cycloolefin copolymer. POLYM. ENG. SCI. 46:1363–1373, 2006. © 2006 Society of Plastics Engineers

Miscibility and Phase Structure of Blends of Poly(ethylene oxide) with Poly(3-hydroxybutyrate), Poly(3-hydroxypropionate), and Their Copolymers

The miscibility and phase behavior of poly(ethylene oxide) (PEO) blends with poly(3-hydroxybutyrate) (P(3HB)), poly(3-hydroxypropionate) (P(3HP)), and poly(3-hydroxybutyrate-co-3-hydroxypropionate)s (P(3HB-co-3HP)s) have been investigated by differential scanning calorimetry (DSC) and high-resolution solid-state 13C nuclear magnetic resonance (NMR). Four bacterial P(3HB-co-3HP) samples with 3HP contents of 15, 25, 46, and 76 mol % have been used in order to investigate possible influence of the sequence structure of P(3HB-co-3HP)s on the miscibility and phase behavior of blends. These four P(3HB-co-3HP) samples have different thermal properties and crystallizability depending on the 3HP contents. The DSC thermal behavior of the blends revealed that the blends of PEO with P(3HB), P(3HP), and P(3HB-co-3HP)s were miscible over the whole composition range but the crystallization of blend components followed by phase separation exerted much influence on the phase structure of the blends. The results from solid-state NMR spectroscopy showed that the 50/50 binary blends of P(3HB)/PEO, P(3HB-co-15%3HP)/PEO, P(3HB-co-25%3HP)/PEO, and P(3HP)/PEO were phase-separated due to the presence of crystalline phase but miscible to some extent. Two components in these blend were found to be mixed on a range greater than 30−40 nm, with two crystalline phases and an amorphous phase of miscible two components coexisting.

Studies on the miscibility and phase structure in blends of poly(epichlorohydrin) and poly(vinyl acetate)

The miscibility of atactic poly(epichlorohydrin) (aPECH) with poly(vinyl acetate) (PVAc) was examined under two different conditions: (i) in dilute solution, using vicometeric measurements and (ii) as cast films, using differential scanning calorimetric (DSC) and FT-infrared spectroscopy. Phase separation on heating, i.e. lower critical solution temperature (LCST) behavior of the aPECH/PVAc blends was examined by the measurement of transmitted light intensity against temperature. From viscosity measurements, the Krigbaum–Wall polymer–polymer interaction (Δ B) was evaluated. The DSC results show that the aPECH/PVAc blends are miscible as evidenced by the observation of a single composition-dependent glass-transition temperature ( T g) which is well described by the Couchman and Gordon Taylor models. The Flory–Huggins interaction parameter ( χ 12) calculated from the T g-method was negative and equal to −0.01, indicating a relatively low interaction strength. The FT-IR results match very well with those of DSC. The cloud point phenomenon is thermodynamically driven but phase separation, once taken place, is diffusion controlled in normal accessible time.

Blends of aliphatic polyesters. VI. Lipase-catalyzed hydrolysis and visualized phase structure of biodegradable blends from poly(ε-caprolactone) and poly( l-lactide)

Phase-separated biodegradable polymer blends were prepared from poly(ε-caprolactone) (PCL) and poly( l-lactide) (PLLA), and Rhizopus arrhizus lipase-catalyzed hydrolysis and phase structure of the blend films were investigated. Gravimetry revealed that the lipase-catalyzed hydrolysis of PCL in PCL- and PLLA-rich phases is disturbed by the presence of PLLA. Polarimetry confirmed the occurrence of a predominant hydrolysis of PCL and subsequent removal of the hydrolyzed water-soluble PCL oligomers in the blend films. Gravimetry and gel permeation chromatography of the non-blended PLLA film indicated that R. arrhizus lipase has no catalytic effect on the hydrolysis of PLLA. The phase structure of the blend films could be visualized by selective enzymatic removal of one component and subsequent scanning electron microscopic observation.

Phase structure and deformation behavior of polyester blends

The supermolecular structure, deformation behavior and tensile properties were studied for the blends of a high molecular weight (HMW) poly(ethylene 2,6-naphthalate) (PEN) and a commercially available low molecular weight (LMW) PEN. The HMW with an intrinsic viscosity (IV) of 3.30dl/g was obtained by solid-state polymerization of the LMW with IV of 0.65dl/g. The mixture of HMW and LMW prepared by a freeze-dried method from the polymer solutions showed two Tgs, independent of the blend ratio. These Tgs corresponded to those for the HMW and the LMW. After melting or even annealing above the Tg of HMW, these blends showed a single Tg, which was dependent on the blend ratio. The deformation behavior of the blends and the tensile properties of the resultant drawn films were greatly affected by the draw temperature (Td). For the drawing above the Tg of HMW (Td=150°C), the LMW behaved as a plasticizer of the HMW. In that case, the draw efficiency evaluated from the Young's modulus of the samples increased systematically with increasing the fraction of HMW in the blends. For the drawing around the Tg of LMW (Td=120°C), the deformation behavior and tensile properties of the resultant drawn films were primarily governed by those for the component polymer with higher fractions in the blends. The results were discussed in connection with the phase structure of the blends.

Relation of chain constitution with phase structure in blends: compatibility of two phases in blends of polyamide with low-density polyethylene and its ionomers

Pressed films of binary blends (polyamide with low-density polyethylene or Surlyn) and ternary (polyamide with low-density polyethylene and Surlyn or a graft-copolymer of acrylic acid onto low-density polyethylene) were examined by dynamic mechanical analysis, thermally stimulated current, and small-angle X-ray scattering. The variation of the glass transition temperature for two phases in the blends was studied by dynamic mechanical analysis and thermally stimulated current. X-ray scattering from the relation of the phases was analyzed using Porod's law and led to values of the interface layer in the blends. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 488–494, 2000

Percolation phenomenon in SAN toughened by core-shell polymer MBS

The fracture toughness of polymeric materials is a decisive factor in material selection. Many effective toughening methods for polymeric materials have been developed in the last two decades. Rubber toughening is one of the methods successful in toughening brittle or notch sensitive polymers. Craze/shear yielding mechanisms have been thought the main source of toughness [1]. However, it has been found that these mixing mechanisms are only valid for the stress behavior of single particles, but it is difficult to describe the relationship between toughness and phase structure of blends containing impact modifiers. Some evidence has shown that the toughening effect depends on the phase structure of the impact modifier strongly [2]. Recently, there has been a preference for core-shell polymers to toughen the polymer matrix. It was proved that toughening by incorporation of core-shell polymer is much more effective than customary rubber. This is because the structure and size of core-shell particles are controllable in synthesis and virtually unchanged during processing [3]. Furthermore, the soft core cannot deform to form detrimental holes under external stress owing to the the rigid shell at the outer layer. In this paper, the core-shell polymer, poly(methacryco-butylene-styrene) (MBS) is adopted to toughen poly(styrene-co-acrylonitrile) (SAN) to investigate percolation phenomena occurring in SAN/MBS blends. The scanning electron microscope (SEM) photographs of the impact fracture surface of SAN and SAN/MBS blends (70/30 by weight) are shown in Fig. 1. The fracture surface of SAN is smooth, showing the characteristic of brittle failture. On the contrary, the fracture surface of SAN/MBS blends shows extensive matrix yielding, the characteristic of tough failure. Fig. 2 shows the relationship between the mechanical properties and the weight fraction of MBS particles in SAN/MBS blends. It reveals that the impact strength is practically unchanged when MBS content is low and 0.248 by weight (or 0.233 by volume) seems the critical value at which the impact strength remarkably increases and an obvious brittle-tough transition occurs. The tensile strength increases somewhat when MBS content is less than 10 wt%, and decreases promptly with increasing MBS content. When MBS content is up to 40 wt%, the tensile strength is 40 MPa, less than that of pure SAN matrix (65 MPa). It seems easier for us to explain the brittle-tough transition on the basis of the so-called ‘surface-to-surface interparticle distance’ model. Wu [2] described the brittle-tough transition of nylon containing rubber particles with the same size and various volume fraction (φr) using this model.

Miscibility and phase structure of at-polypropylene/ethylene- block-(ethylene- co-butylene)- block-ethylene-copolymer blend

Miscibility and phase structure in blends of atactic-polypropylene (aPP) with poly[ethylene- b-(ethylene- co-butylene)- b-ethylene] (E-b-EB-b-E) containing different butylene content in the mid-block were investigated by differential scanning calorimetry (DSC), transmission electron microscopy (TEM) and field emission type scanning electron microscopy (FE-SEM). In DSC measurement, blends showed single glass transition temperature in no relation to the blend composition and the butylene contents of mid-block in the block copolymers. On the other hand, the melting point of PE block in the block copolymers was not varied systematically with variation of the blend composition with no relation to the butylene content. From these results, it is assumed that aPP dissolves in the EB block in the copolymers. In morphological observation, it was revealed that all blends have the islands–sea structures containing PE domain. In the blends using the high butylene content copolymer, it was observed that PE domain became smaller than that of neat block copolymer. On the other hand, in the lower butylene content copolymer, the microphase structure was not observed but fine dispersed phase separated structures were observed in the blends of aPP and the copolymer.

Coarsening of the phase structure in immiscible polymer blends. Coalescence or ostwald ripening?

The results of theories of the Ostwald ripening and coalescence applied to molten quiescent polymer blends with dispersed phase structure were analyzed. From a comparison of predictions of the theories with available experimental results follows that coarsening of the phase structure in quiescent polymer blends with medium or high interfacial tension is induced by the coalescence. Both the mechanisms play a role in coarsening of the phase structure in blends with low interfacial tensions. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 181–187, 1999

Electrically induced phase inversion in urethane-modified polypropylene glycol/dimethylsiloxane blend

Electric-field-induced phase inversion in immiscible liquid blends of urethane-modified polypropylene glycol (UPPG)/dimethylsiloxane (DMS) was discovered. When the fraction of DMS is in the range of 23–26 wt. %, UPPG forms the particulate domains and DMS forms the continuous phase under no field. However, the application of an electric field induces connection among UPPG domains, and results in phase inversion; UPPG forms the continuous phase and DMS forms the particulate domains. This finding gives great possibilities of controlling the phase structure of blends using an electric field, and thus controlling their physical properties.

Studies on polymer blends with moderate specific interactions. 2. phase structure of blends SAN/TPU and SAN/TPU/EVA

This paper deals with morphological studies of binary and ternary blends composed of poly(styrene-co-acrylonitrile) (SAN), polyurethane elastomer (TPU) and poly(ethylene-co-vinyl acetate) (EVA). Selective etching was found necessary to expose the morphologies of the blends. Chloroform or hot acetone, hexane/toluene (2/1v/v) and NaOH/CH3OH (1wt%) were found to be selective etching agents for SAN, EVA and TPU, respectively. SAN and TPU form blends with fine dispersion structure, while SAN and EVA lead to rough phase structure with poor phase adhesion. These results are in accordance with the difference in the mechanical properties of SAN/TPU and SAN/EVA. In addition, for SAN/TPU/EVA blends, if TPU is only a minor component, it is preferentially located at the interphase, playing the role of a compatibilizer. As the amount of TPU increases, the compatibility is gradually improved. ©1997 SCI

Studies on polymer blends with moderate specific interactions. 2. phase structure of blends SAN/TPU and SAN/TPU/EVA

Studies on polymer blends with moderate specific interactions. 2. phase structure of blends SAN/TPU and SAN/TPU/EVA