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In the research described here immiscible polymer blends based on amorphous poly(methyl methacrylate) (PMMA) and semi-crystalline polypropylene (PP) were produced via a melt-mixing method. The effects of the addition of graphene and clay nanoparticles on the compatibility and properties of the blends were investigated. Scanning electron microscopy results showed that the neat blends at all compositions were severely phase separated and a droplet-in-matrix morphology was attained. Introduction of graphene and clay caused the compatibility of the blends to be highly enhanced and, thus, a finer and more uniform morphology was obtained for the nanocomposites. Based on the morphology results, it was found that graphene had more affinity toward the PP phase and clay was more compatible with PMMA. This hypothesis was further proved via mechanical analysis and thermogravimetric analysis (TGA) results. The toughness of the neat blends was increased upon increasing the PP content; however, it was reduced for all the nanocomposites relative to the blend of the same polymer composition. The thermal stability of the blend at a composition of 70/30 PMMA/PP was improved via addition of clay and graphene. The first stage of degradation (PMMA) was shifted to higher temperatures once clay was added to the system while the second stage of degradation (PP) was impeded upon addition of graphene. [ABSTRACT FROM AUTHOR]

The preparation of self-healing polymers for use following mechanical failure using commercial, bio-based polymers without complex synthesis and expensive healing reagents has been very rare. In this study two commercial, bio-based polymers, natural rubber (NR) and polycaprolactone (PCL), were melt-blended to form NR/PCL blends. To increase the healing efficiency via supramolecular hydrogen bonding interactions, various amounts of acrylic acid were grafted onto the PCL. The results showed that the healing efficiency of the blends in the self-healing test at 80°Cwas higher than for blends at 60 °C due to higher molecular mobility/diffusion resulting from the molecular motions above the melting temperature of PCL which was near 55 °C in all cases. The highest healing efficiency, 62.8%, was attained for the NR/PCL-g-4AA (40/60) blend containing 4 phr PCL of AA. In addition, with the application of the shape memory-assisted self-healing (SMASH) mechanism, the healing efficiency increased further, up to 79.9%. The high shape recovery ratio (>90%) helped the crack to close faster when the sample was heated to trigger the shape memory process, leading to the increased healing efficiency in comparison with the sample without the shape memory process triggered by heating. To the best of the authors' knowledge, there have been no similar works in the preparation of self-healing, bio-based polymer blends through the current approach so far. We suggest the synergistic effects of both the physical and chemical processes applied to commercial, bio-based polymers provide the chance of expanding the applications of these green polymers with additional functionality. [ABSTRACT FROM AUTHOR]

A series of polycarbonate (PC)/acrilonitrile butadiene rubber (NBR)/multi-wall carbon nanotube (MWCNT) nanocomposites were prepared via melt compounding in an internal mixer. The effect of the MWCNT content on the morphology and the thermal and mechanical properties of the prepared nanocomposites were studied. The morphologies of the samples were investigated by field-emission scanning electron microscopy (FESEM) and the thermal properties by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The tensile mechanical results of the nanocomposites showed a decrease in elongation at break with an increase of only 2 wt% of MWCNT content in the PC/NBR blends, and an increasing value in elastic modulus and tensile strength of the nanocomposites. The FESEM images showed that the MWCNTs had good affinity with the polymers and no compatibilizer was needed for making the nanocomposites. The DSC and TGA results showed an increase in thermal stability with addition of MWCNTs because of the more thermally stable carbon nanotubes particles which was uniformly dispersed within the nanocomposites. [ABSTRACT FROM AUTHOR]

The completely crosslinked shape memory polymer blends (SMPs) traditionally suffer from recycling problems due to their network structure. In this paper we describe the thermal, mechanical, and shape memory behavior of physical blends of OBC (Olefin block copolymer) and EVA (Ethylene-vinyl acetate copolymer), with and without modification of one or both of the components, prepared using a melt-blending method. These behaviors of the modified blends, based on maleated OBC (OBC-g-MA) and/or vinyltriethoxysilane (VTEOS) modified EVA, included OBC/EVA-g-VTEOS, OBC-g-MA/EVA, and OBC-g-MA/EVA-g-VTEOS blends; they were investigated to compare with the OBC/EVA blend. The SEM (scanning electron microscopy) observations showed that the compatibility of the silane and maleic anhydride modified OBC/EVA blends were better than that of the unmodified OBC/EVA blend. The crystallization temperatures of OBC and EVA in the modified blends were higher than those in the neat blend. The OBC-g-MA/EVA-g-VTEOS blend had the highest modulus and thermal stability of all investigated blend systems due to the numerous interactions between maleic anhydride and silane. The shape memory performance, as defined by the shape fixity ratio (Rf) and shape recovery ratio (Rr), was higher for the modified blends of one or both of the modified components than that for the OBC/EVA blend. These modified blends were readily reprocessible, like thermoplastic vulcanizates, and still retained shape memory behavior, in contrast with the fully crosslinked shape memory polymer blends; thus they were also improved in terms of the environmental aspects of processing. [ABSTRACT FROM AUTHOR]

The main aim of this study was to deal with one of the major drawbacks of polypropylene (PP) fibers, i.e. low resiliency, by incorporating poly (trimethylene terephthalate) (PTT) nano-fibrils as a dispersed material into the PP polymer matrix. Thanks to the special helical shape of the PTT polymer backbone, the incorporated nano-fibrils of the PTT polymer strengthened the resiliency of the blend fibers. The presence of 10 and 15 wt% of PTT in the blend fibers led to an approximately 20% increase in the resilience behavior, compared to pure PP fibers, with the mechanical properties of the PP matrix preserved. The development of the fibrillar structures during the different steps of the melt spinning process was confirmed by scanning electron microscopy (SEM), and the lowest mean diameter of the nano-fibrils was 64 nm for the hot drawn blend fiber samples consisting of 10 wt% of PTT. In summary, we suggest the optimized blend fiber samples produced in this research will be a promising candidate for a wide range of engineering applications. [ABSTRACT FROM AUTHOR]

The nonisothermal crystallization kinetics of poly(vinylidene fluoride) (PVDF) in PVDF/polymethyl methacrylate (PMMA)/dipropylene glycol dibenzoate (DPGDB) blends, where DPGDB served as a diluent, via solid–liquid (S-L) phase separation during a thermally induced phase separation process was investigated through differential scanning calorimetry (DSC) measurements. It was found that the Ozawa model could only describe the nonisothermal crystallization behavior of PVDF/PMMA/DPGDB system to some extent. The influence of the cooling rate and PMMA/PVDF weight ratio in the PVDF/PMMA/DPGDB system on the crystallization mechanism was also examined based on the Avrami–Jeziorny method and Mo method. Primary crystallization and secondary crystallization were observed in the Avrami–Jeziorny analysis. The analysis by the Avrami–Jeziorny and Mo models indicated that the increase of PMMA/PVDF weight ratio decreased the crystallization rate during the primary crystallization stage. The results showed that the Mo method could well explain the kinetics of the primary PVDF crystallization. The Avrami–Jeziorny method, however, could not well describe the nonisothermal crystallization process of PVDF in the primary crystallization stage. The activation energy, determined by the Kissinger method, was not suitable to reflect the PVDF crystallization process in the PVDF/PMMA/DPGDB system. [ABSTRACT FROM PUBLISHER]

Shape memory NR/PCL bio-based blends, where NR served as the reversible phase and PCL served as the switching phase, were prepared using a melt blending process. Peroxide, besides its role as a cross-linking agent to NR, was used to enhance the compatibility between NR and PCL, which was confirmed via Fourier transform infrared spectra and scanning electron microscopy analyses. With increasing peroxide content, the tensile strength increased steadily with decreasing PCL contents, up to 12.3 ± 0.8 MPa for the NR/PCL (70/30) blend at 2 phr peroxide. The shape fixing ratio decreased slightly with increasing peroxide content, especially for high NR content. The values of the shape recovery ratio were high, up to 100%, regardless of PCL content. The recovery stress was found to reach its maximum value around 60°C. In order to consider both fixing ratio (Rf) and recovery ratio (Rr) together, an additional denotation of shape memory index, RfRr, coupling both ratios by the product of the fixing ratio and recovery ratio, is proposed. The shape memory index (RfRr) reached values close to 100%, at the NR/PCL composition of 50/50 and 70/30; in particular, the highest value was for the 50/50 case regardless of peroxide concentration. The shape recovery ratio and fixing ratio remained largely unchanged even after 30 cycles of deformation and recovery processes for a typical NR/PCL/DCP (30/70/0.5) blend which, thus, outperformed all known shape memory blends in the literature. [ABSTRACT FROM PUBLISHER]

Toughened poly (butylene terephthalate) (PBT) with triglycidyl isocyanurate (TGIC)-filled poly (ethylene–octene) (POE) was prepared by melt reaction extrusion. For retarding the reaction extent between PBT and the epoxy component, the TGIC was first blended with POE to enwrap its reactive epoxy groups. Then, the TGIC-filled POE was used to melt blend with PBT. The Fourier transform infrared (FTIR) spectra showed that no other peaks appeared in the POE/TGIC specimens except for those originally existing in pure POE and TGIC. The rheological results further confirmed that no reaction occurred between the epoxy and the POE matrix. When the POE/TGIC was blended with PBT, a distinct increase of the viscosity suggested that the migration of the TGIC from POE to PBT during the melt processing induced chain extension reactions of PBT. The results obtained from DSC and DMA revealed that the chain extension of PBT induced by the reaction with TGIC restricted the mobility of PBT chains leading to a limitation of the recrystallization-remelting process and an increase of the glass transition temperature of PBT. The mechanical tests showed that the presence of TGIC in the POE phase distinctly improved the toughness of PBT. Compared to the case of a PBT/POE (80/20, wt%/wt%) blend, the elongation at break and impact strength of the system filled with 5 phr TGIC were increased more than three and six times, respectively. [ABSTRACT FROM PUBLISHER]

A series of crystalline semiconducting poly(3-butylthiophene) (P3BT)/crystalline insulating polyethylene (PE) blends were prepared and the miscibility, crystallization, and structure/morphology were investigated. Even though phase separation was observed by transmission electron microscopy (TEM) and small-angle X-ray scattering (SAXS), several pieces of evidence indicated that limited miscibility should be present in PE/P3BT blends: small changes in both Tmand crystallinity of PE phase and a small portion of PE being dissolved in P3BT. The study of PE isothermal crystallization kinetics revealed that the introduction of P3BT significantly influenced the nucleation mechanism and growth geometry, i.e., PE was transformed from three-dimensional (3D) spherulitic to two-dimensional (2D) disc crystals. A striking reduction of nucleation density and an obvious ringed morphology of PE spherulites (2D) in PE/P3BT blends were also observed by polarized optical microscopy; it is proposed that the limited miscibility between PE and crystalline P3BT favors the formation of ringed PE spherulite in the blends. Additionally, preferred orientation of PE lamellae, with their b-axis largely constrained to the thin film plane, was observed by X-ray diffraction in PE/P3BT blend films. It is evidenced that the PE orientation was due to the b-axis being the crystal growth direction, which can only be in film plane. [ABSTRACT FROM AUTHOR]

Melt blended polyamide (PA)/liquid crystal polymer (LCP) blends were prepared and their structures and properties were studied. The tensile strength and impact strength of the PA/LCP blends increased with increasing small amount of LCP content. Compared with a pure PA sample, there was a 17.7% increase in the tensile strength and a 45.5% increase in the impact strength when the LCP content was less than 10%. On the other hand, the Vicat softening temperature decreased with increasing the LCP content. Differential scanning calorimetry (DSC) showed that small addition of LCP was beneficial to increase the crystallinity of PA component for PA/LCP blends and the melting peak for the PA component of PA/LCP blends shifted to lower temperature with increasing LCP content. Scanning electron microscopy (SEM) displayed a layered structure existing in the injection moldings of PA/LCP blends with the LCP crystals having a preferred orientation along the melt flow direction in the sub-skin, shearing layer, and core region. The increased crystallinity of PA component and preferred orientation structure of LCP phase were beneficial to increase the mechanical properties of the PA/LCP blends. [ABSTRACT FROM AUTHOR]

Poly(lactic acid) (PLA)/poly(ethylene-co-vinyl alcohol) (EVOH) blends were prepared via melt blending to improve the barrier properties of PLA. The phase morphologies and final properties (rheological behavior, thermal and dynamical-mechanical features, barrier properties, and mechanical behaviors) of the blends were investigated as a function of the EVOH content. The results indicated that hydroxyl groups of EVOH promoted the degradation of PLA, and thus affected the viscosities and morphologies of the resulting blends. The intrinsic viscosities of PLA in the blends decreased with the content of EVOH. The PLA and EVOH presented typical phase-separated morphologies, with a relatively small domain size of the EVOH phase. The EVOH enhanced the cold-crystallization behavior of PLA. The barrier properties to water vapor and oxygen increased linearly with increasing EVOH content. [ABSTRACT FROM AUTHOR]

The mechanical properties, morphology, crystallization, and melting behaviors and nonisothermal crystallization kinetics of poly (trimethylene terephthalate)(PTT)/maleinized acrylonitrile-butadiene-styrene (ABS-g-MAH) blends were investigated by an impact tester, polarized optical microscopy, and differential scanning calorimetry (DSC). The results suggested that the ABS-g-MAH component served as both a nucleating agent for increasing the crystallization rate and as a toughening agent for improving the impact strength of PTT. When the ABS-g-MAH content was 5wt.%, the blend had the best toughness and a high crystallization rate. The blends showed different crystallization rates and subsequent melting behaviors due to their different ABS-g-MAH contents. The Ozawa theory and the method developed by Mo and coworkers were used to study the nonisothermal crystallization kinetics of the blends. The kinetic crystallization rate parameters suggested that the proper contents of ABS-g-MAH can highly accelerate the crystallization rate of PTT, but this effect nearly reaches saturation for ABS-g-MAH contents over 5%. The Ozawa exponents calculated from the DSC data suggested that the PTT crystals in the blends have similar growth dimensions as those in neat PTT, although they are smaller and/or imperfect. The effective activation energy calculated by the method developed by Kissinger also indicates that the blends with higher ABS-g-MAH content were easier to crystallize. [ABSTRACT FROM AUTHOR]

The steady shear properties and morphology of high-density polyethylene (HDPE)/high impact polystyrene (HIPS)/nanoclay (Cloisite 20A) nanocomposites with and without compatibilizer (ethylene vinyl acetate, EVA) was investigated. The rheological studies were performed by a capillary rheometer at three different temperatures; and the morphological properties of the nanocomposites were evaluated using X-ray diffractometery (XRD). The XRD analysis showed that the nanoclay was intercalated in the polymeric phases. Rheological tests showed that the prepared nanocomposites had shear thinning behavior, obeying the power law equation. At low shear rates and lower temperatures (180°C and 200°C), the addition of nanoclay decreased the shear viscosity and stress, but at higher temperature (220°C), the addition of nanoclay caused an increase in shear viscosity and stress. Viscosity was less sensitive to addition of nanoclay at higher shear rates. Flow activation energy of the nanocomposites was calculated using an Arrhenius type equation. It was concluded that the temperature sensitivity of the nanocomposites was increased by increasing of nanoclay content. [ABSTRACT FROM AUTHOR]

A new type of thermotropic liquid crystalline aromatic poly(ether ester) (PEE) was prepared from 1,3-bis(4′-carboxyphenoxy)benzene, 1,4-diacetoxybenzene, and p-acetoxybenzoic acid through a melt transesterification process. The rheological behavior of blends of poly(phenylene sulfide) (PPS) with PEE was studied using a high-pressure capillary rheometer with the shear rate range of 50 s−1 to 3000 s−1. The results show that according to the range of shear rate, the flow curves of PEE/PPS blends can be divided into three zones: a first shear-thinning zone (n < 1, “n” represents non-Newtonian indexes), a shear-thickening zone (n > 1), and a second shear-thinning zone (n < 1), and the former two zones are more obvious with the increase of PEE content or elevated temperature. In the second shear-thinning zone, the PPS melt is close to a Newtonian fluid at high temperature and high shear rate; meanwhile the non-Newtonian behavior of the PPS melt at high temperature is enhanced with the addition of PEE. The apparent viscosity of PPS melts sharply dropped after adding PEE, especially at relatively low temperature and low shear rate. The curve of apparent viscosity vs. shear rate starts to flatten out after adding PEE, suggesting that the addition of PEE lowers the sensitivity of PPS to shear rate. As the content of PEE increases, the activation energy of the viscous flow, ΔEη, of PPS decreases, which means that adding PEE weakens the temperature sensitivity of the apparent viscosity of the PPS melt. It can clearly be seen that the addition of PEE is beneficial to the processing of PPS. [ABSTRACT FROM AUTHOR]

This paper focuses on the mechanical properties and crystal morphology of a self-reinforced high-density polyethylene 5000S (HDPE 5000S) by simultaneously blending with 9 wt% high-molecular-weight polyethylene (HMWPE) and 9 wt% low-molecular-weight polyethylene (LMWPE) (A9) under the shear stress field which was engendered by a self-made dynamic packing injection molding (DPIM) machine. The results of mechanical properties, differential scanning calorimetry, and scanning electron microscopy characterization were as follows: (1) The tensile strength of the dynamic samples increased to 112.1 MPa, 4.85 times as much as that of static packing injection molding (SPIM) samples (23.1 MPa), as a result of realizing polyethylene's self-enhancement; (2) Shish-kebab structure was found in the dynamic samples; (3) The crystallinity of the DPIM A9 sample reached 68.6%, on increase by 18.7% compared with that of the SPIM sample. The formation of the shish-kebab structure and enhancement of mechanical properties are explained. [ABSTRACT FROM AUTHOR]

In order to improve the compatibility of polycarbonate (PC) and acrylonitrile– butadiene–styrene (ABS), a new type of reactive compatibilizer, methyl methacrylate graft acrylonitrile–butadiene–styrene (MABS) tetramer, was synthesized. The structure and properties of PC/ABS (70/30) blend with various MABS ratios were studied in terms of their mechanical and morphological properties. The results indicated that with the addition of MABS, the glass transition temperature (Tg) of the PC and ABS phases were closer to each other. Addition of MABS decreased the domain size of the ABS dispersed phase, making the dispersed phase well distributed, and the interfacial cohesiveness was enhanced. Notched impact strength and elongation at break of the PC/ABS (70/30) blend increased remarkably with the addition of MABS, with a small drop in the tensile strength. [ABSTRACT FROM AUTHOR]

A multiblock copolymer of polyethersulfone (PES) and polycarbonate (PC) was used as a compatibilizer for a blend of PES/PC. The morphology, thermal properties, mechanical properties, etc. of the resulting ternary blend systems were investigated. The addition of the compatibizer improved the compatibility between PES and PC. It was found that the interfacial adhesion was enhanced; the size of the dispersed phase was reduced and this resulted in an improvement of elongation at break and tenacity of PES/PC blends and tensile strength and tensile modulus were almost constant. [ABSTRACT FROM AUTHOR]

Microporous membranes were prepared via thermally induced phase separation of a poly(vinylidene fluoride) (PVDF)/poly(methyl methacrylate) (PMMA) blend (with mass ratio = 70/30)/methyl salicylate system. The differential scanning calorimetry results revealed that the observation of double melting phenomenon in quenched samples was a result of a variation in the morphology (different crystal size or perfection of crystals), which formed during the sample preparation. When the samples were quenched at 118°C, 110°C, and 100°C, a spherulitic structure was present in the membranes due to the crystallization of PVDF. As the holding time period increased, the crystallization of PVDF was enhanced owing to the aggregation of a polymer-rich phase (PVDF/PMMA blend) during the phase separation. The structure of the resulting PVDF blend membranes, detected by scanning electron microscopy, was greatly affected by liquid-liquid phase separation and the crystallization of PVDF in the mixture. [ABSTRACT FROM AUTHOR]

Ethylene-propylene-diene-methyl methacrylate/acrylonitrile terpolymers (EPDM-g-MAN) were synthesized by comonomers methyl methacrylate and acrylonitrile (MMA-AN) grafted on EPDM macromolecules with solution graft copolymerization. The engineering plastics of the blend of EPDM-g-MAN with SAN (AEMS) were prepared by blending EPDM-g-MAN with SAN resin. The effect of AN/MMA-AN weight percentage (fAN) on monomer conversion ratio, grafting ratio, and grafting efficiency of the graft copolymerization and the notched Izod impact strength of AEMS were investigated. The notched Izod impact strength of AEMS, prepared by blending SAN with EPDM-g-MAN, was synthesized under our optimum S2 reaction conditions, with EPDM/MMA-AN weight proportion of 50/50 and fAN of 10 wt%, presenting a peak with the maximum value of 61.0 kJ/m2. The microstructure of AEMS prepared with S2 reaction conditions showed that when the polarity of EPDM-g-MAN was appropriate, the EPDM phase formed a pseudocontinuous phase in the SAN matrix and the interfacial adhesion was strong, which could induce shear yielding of the SAN matrix. Differential scanning calorimetry analysis showed that there was good compatibility between SAN resin and EPDM-g-MAN synthesized with fAN of 10 wt% and a EPDM/MMA-AN weight ratio of 50/50. [ABSTRACT FROM AUTHOR]

Electrospinning of polystyrene (PS) and styrene-isoprene-styrene block copolymer (SIS) blends with different composition weight ratios was carried out with a mixed solvent, tetrahydrofuran (THF) and N,N-dimethylformamide (DMF) (80/20, v/v). Electrospun PS/SIS blend fibers were characterized using scanning electron microscopy. The results indicated that the presence of DMF resulted in a beneficial effect on fiber formation and greater electrospinnability of as-spun fibers. Furthermore, the morphological structure and diameters of as-spun fibers from PS and SIS blends were affected by the composition weight ratio and the solution properties. The fibers from 10 wt% solution exhibited the best mechanical properties compared to the fibers from other concentrations for the same composition, and increasing the SIS content one observes a vanishing of PS-related properties, while SIS-related properties emerges. [ABSTRACT FROM AUTHOR]

Carbon nanofibers (CNFs) with diameters ranging from 50 nm to 150 nm were prepared from polymer blends of polyacrylonitrile (PAN)/polymethyl methacrylate (PMMA) via a wet-spinning method and subsequent thermal treatment. The main factors that influence the diameter of the CNFs, including molecular weight of PAN, mass ratio of PAN/PMMA, and spinning draw ratio, are discussed. The formation of graphitization structures of the blend fibers during the carbonization process was investigated by Fourier transform infrared spectroscopy, Raman spectroscopy, and X-ray diffraction spectroscopy. The complex permittivity ε (ε' - jε''), complex permeability μ (μ' - jμ''), and microwave absorption properties of CNF/epoxy composites were studied in the X-band frequency range (8.2-12.4 GHz). ε', ε'', μ', and μ''' were found to increase with increased CNF content. Measured values of these parameters were used to determine the reflection loss at various sample thicknesses, based on a model of a single-layered plane wave absorber backed by a perfect conductor. The calculated results showed that the composite with a CNF content of 8 wt% and a thickness of 2.1 mm would give a maximum reflection loss of -34 dB at 10.5 GHz with the -10 dB bandwidth over the extended frequency range of 8.8-12.4 GHz. [ABSTRACT FROM AUTHOR]

The thermally induced phase separation (TIPS) process was employed to prepare poly(vinylidene fluoride)/poly(methyl methacrylate) (PVDF/PMMA) blend microporous membranes. The effect of PMMA content on the dynamic crystallization temperature of the PVDF/PMMA/sulfolane system was analyzed. The effects of PMMA weight fraction and cooling rate on the cross-sectional morphology, crystallinity, crystal structure, thermal stability, and porous structure of the resulting membranes were investigated using scanning electron microscopy (SEM), differential scanning calorimetry (DSC), X-ray diffraction (XRD), thermogravimetric analysis (TGA), and a mercury porosimeter, respectively. The mechanical properties of the membranes were evaluated by tensile tests. It was found that solid-liquid phase separation occurred in the PVDF/PMMA/sulfolane system. Scanning electron microscopy revealed that either increasing PMMA weight fraction or decreasing cooling rate will lead to a macroscopical phase separation between PVDF and PMMA. PMMA weight fraction and cooling rate had some influence on the crystallinity, porous structure, and mechanical properties, but no influence on the polymer crystal structure of the membranes. PMMA weight fraction influenced thermal stability of the final membranes but cooling rate did not. [ABSTRACT FROM AUTHOR]

Miscibility of poly(ε-caprolactone), (PCL), containing 1, 5, and 10 wt.% poly(vinyl formal) (PVF) blends was investigated by polarized optical microscopy (POM), atomic force microscopy (AFM), and differential scanning calorimetry (DSC) for spherulitic morphology and equilibrium melting temperature (T°m, via Hoffman-Weeks plot). The T°m of PCL in the blends was similar to that of pure PCL, indicating immiscibility. Isothermally, melt crystallized virgin PCL between 30°C and 50°C showed spherulitic morphology with negative birefringence, Maltese cross, and without extinction rings. The nucleation and growth rates of PCL spherulites were found to be dramatically reduced with the addition of PVF. Extinction rings and a change in the sign of the birefringence of the PCL spherulites were observed and were found to be dependent on blend composition and crystallization temperature. The presence of a ring pattern in spherulites was an indication of miscibility between the two polymers that had failed to be detected by thermal methods. The formation of a ring pattern is discussed in terms of lamella twisting originating from a change in the crystallization mechanism. [ABSTRACT FROM AUTHOR]

Blends of PLA and linear low-density polyethylene (LLDPE) were compatibilized with glycidyl methacrylate (GMA)-grafted poly(ethylene-octene) copolymer (mPOE). Effects of compatilizer on phase structure of compatibilized PLA/LLDPE were studied by spreading coefficient calculation prediction, scanning electron microscopy (SEM), differential scanning calorimetry (DSC), and wide-angle X-ray diffraction (WAXD) analysis. The spreading coefficient calculations, based on experimental and calculated surface tension data, show that mPOE spreads on LLDPE extensively to encapsulate LLDPE completely, which is in good agreement with the results of DSC, SEM, and WAXD analysis. The chemical reaction between the end carboxyl groups or end hydroxyl groups of PLA and epoxy groups of mPOE, which is suggested as the driving force leading to an ideal interfacial adhesion between PLA and the dispersed phase, was confirmed by Fourier transform infrared ray (FT-IR) spectroscopy analysis. [ABSTRACT FROM AUTHOR]

Super-tough nylon 6/ABS blends were prepared by using styrene/acrylonitrile/maleic anhydride co-polymer (SAM) as a compatibilizer. The variations in morphology, mechanical behavior, and crystallinity associated with the reaction of the SAM with the nylon were characterized. The results showed that the addition of SAM to nylon 6/ABS blends enhanced the interfacial adhesion between nylon 6 and ABS, and this led to the decrease of ABS domain size and the improvement of mechanical properties of their blends. Moreover, it could be found that the crystallinity and phase morphology changed with the variation of SAM. [ABSTRACT FROM AUTHOR]

Interactions between polymer molecules in dilute solution changes the effective dynamic volume of the molecules, which influences the viscosity. In a plot of reduced viscosity against concentration, the slope of the curve may decrease or increase according to the miscibility of the polymers. This change of slope in a ternary system can be used as a criterion to determine the compatibility of a polymer-polymer blend in dilute solution. In the present study the compatibility of PEO and HPMC was investigated in water by the viscosity technique; the blend was found to be semicompatible in nature. The semicompatible nature of the blend was confirmed by ultrasonic, refractive index, and density measurements. [ABSTRACT FROM AUTHOR]

Polymer blends of chitosan (CHI) with poly(vinyl pyrrolidone) (PVP) have been prepared by solution blending, and their miscibility studies were carried out by using physical techniques over an extended range of concentration and composition in buffer solution. The viscosity, ultrasonic velocity, density, and refractive index were measured at 30, 40, and 50°C, respectively. Using viscosity data, the interaction parameter μ and α were computed to probe the miscibility. These values revealed that the blend is miscible when the chitosan content is more than 60% in the blend at all temperatures. The obtained results were further confirmed by the ultrasonic velocity, density, and refractive index measurements. [ABSTRACT FROM AUTHOR]

Blends of two grades of acrylonitrile-butadiene-styrene (ABS) with three different compounds of poly (vinyl chloride) (PVC) were prepared via melt processing and their morphology, flammability, and physical and mechanical properties were investigated. SEM results showed that the ABS/PVC blend is a compatible system. Also, it can be inferred from fracture surface images that ABS/PVC blends are tough, even at low temperatures. It was found that properties of these blends significantly depend on blend composition and PVC compound type; however, the ABS types have only a small effect on blend properties. On blending of ABS with a soft PVC compound, impact strength, and melt flow index (MFI) increased, but tensile and flexural strength decreased. In contrast, blending of ABS with a rigid PVC compound improved fire retardancy and some mechanical properties and decreased MFI and impact strength. [ABSTRACT FROM AUTHOR]

The kinetics of isothermal melt crystallization of poly(trimethylene terephthalate) (PTT)/poly(butylene terephthalate) (PBT) blends were investigated using differential scanning calorimetry (DSC) over the crystallization temperature range of 184-192°C. Analysis of the data was carried out based on the Avrami equation. The values of the exponent found for all samples were between 2.0 and 3.0. The results indicated that the crystallization process tends to be two-dimensional growth, which was consistent with the result of polarizing light microscopy (PLM). The activation energies were also determined by the Arrhenius equation for isothermal crystallization. The values of ΔE of PTT/PBT blends were greater than those for PTT and PBT. Lastly, using values of transport parameters common to many polymers (U*=6280 J/mol, T∞=Tg - 30), together with experimentally determined values of Tm0 and Tg, the nucleation parameter, Kg, for PTT, PBT, and PTT/PBT blends was estimated based on the Lauritzen-Hoffman theory. [ABSTRACT FROM AUTHOR]

Blends of polycarbonate (PC) and acrylonitrile–EPDM (ethylene/propylene/diene elastomer)–styrene terpolymer (AES) were prepared at 20%, 30%, 40%, 50%, and 80% by weight of AES. The rheological properties and morphology of the PC, AES, and their blends were studied systematically. The strain sweep results show that the linear viscoelastic region of the AES is far less than that of PC. With the addition of AES, the linear viscoelastic regions become shorter gradually. The dynamic frequency sweep measurements indicate that the dependences of the complex viscosity on frequency for PC and AES are very different. With the increase of AES content, the complex viscosities of blends exhibit a more significant shear thinning behavior. All the samples, except PC, display a distinct nonterminal behavior at low frequencies. The level of the plateau depends on the volume fraction of the rubber phase. PC, AES, and PC/AES blends obey the Cox–Merz rule generally. The blends, which have similar morphology, show similar rheological properties. [ABSTRACT FROM AUTHOR]

Measurements of viscosity, ultrasonic velocity, refractive index, and density of chitosan (CS)/polyethylene glycol (PEG) blends in buffer solution (0.1 M acetic acid+0.2 M sodium acetate) were carried out for different blend compositions at 30, 40, and 50°C. Using the viscosity data, interaction parameters μ and α were computed to determine miscibility. These values revealed that the blend was miscible when the chitosan content was more than 60% of the blend. The results were further confirmed by ultrasonic velocity, density, and refractive index measurements. Further, the results revealed that the change in temperature has no significant effect on the miscibility of CS/PEG polymer blends. [ABSTRACT FROM AUTHOR]

Phase behavior of the binary polymer system consisting of thermoplastic polyurethane (TPU) and styrene acrylonitrile (SAN) copolymers of various compositions (100/0, 90/10, 70/30, 50/50, 30/70, 0/100) has been investigated by differential scanning calorimeter (DSC). The phase separation on heating, i.e., lower critical solution temperature (LCST) behavior, was found to occur when these blends were heated to elevated temperatures. The cloud-point temperature or phase separation was found to vary with TPU/SAN blend compositions. The interaction parameters were calculated from the measurements based on glass transition temperature of the blends. The results suggest that the extent of partial miscibility of the two components is very limited. [ABSTRACT FROM AUTHOR]

Nylon-6 (Ny-6) and ethylene-vinyl alcohol copolymer (EVOH) binary blends were prepared in various compositions via dynamic melt blending. In addition, 50/50 blends of EVOH with nylon-6/6.9 (Ny6/6.9) and nylon-11 (Ny-11) were prepared to study the effect of nylon type on the structuring process under melt mixing. The phase morphology and the crystallization behavior of the blends were investigated using differential scanning calorimetry (DSC), dynamic mechanical thermal analysis (DMTA), Raman spectroscopy, scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). The insoluble content was studied by solvent extraction. The mixing torque was found to increase with mixing time for intermediate Ny-6 contents, indicating chemical reactions and hydrogen bonds formation between the polymers. Based on FT-Raman spectroscopy chain extension is suggested to be the main chemical reaction between EVOH and Ny-6. The different interaction levels obtained for the Ny-6/EVOH blends affect their properties. The melting temperature of one component decreases as the content of the other component is increased. EVOH has lower crystallization degree when its content is lower; conversely, Ny-6 crystallinity increases for some compositions compared to the neat polymer. Storage modulus and glass transition temperature values of the blends are between those of the neat polymers according to composition. However, positive deviation was obtained for the 50/50 Ny-6/EVOH blend owing to the chemical reaction between the polymers. SEM micrographs of fractured surfaces exhibit quite uniform, almost as a single-phase morphology, indicating high interaction level between the polymers. SEM/EDS of etched samples revealed that the dispersed particles in the blends are on a submicron scale. [ABSTRACT FROM AUTHOR]

The partially deacetylated chitin with degree of deacetylation of ∼28%, fully soluble in dilute acetic acid, was prepared by alkaline treatment under homogeneous conditions and then blended with poly(vinyl alcohol) (PVA) using aqueous acetic acid solution as a cosolvent. The miscibility and intermolecular interaction between chitin and PVA were investigated using differential calorimetry. When chitin was blended with PVA up to 50%, the melting temperature (Tm) and heat of fusion (ΔHf) of PVA were depressed gradually. The interaction energy density (B) and the interaction parameter (χ12) estimated from the depression of melting temperature were -10.13 J/cm3 and -0.33 (at 502 K), respectively. The negative value of χ12 indicates that chitin and PVA are miscible. With increasing weight fraction of chitin in blends, there were large and systematic decreases in the crystallization temperature (Tc) and the heat of crystallization (ΔHc) of PVA. The glass transition temperature (Tg) of PVA tended to shift to higher temperatures, with increasing weight fraction of chitin up to 40% in the blends. There was a broadening of the width of the transition. [ABSTRACT FROM AUTHOR]

In several acrylonitrile-butadiene-styrene (ABS) copolymers, some amounts of polybutadiene (PB) laTeX grafted with styrene-acrylonitrile (SAN) copolymer were replaced by acrylonitrile-butadiene rubber (NBR) copolymer, and the variations of morphology, mechanical properties, and rheological properties were examined. The impact strength of ABS, with a bimodal distribution of rubber size, was improved by the presence of the NBR, which distributes coarsely in the SAN matrix. Yield behavior in the rheological response due to the presence of rubber particles in the SAN matrix was enhanced by the coarser NBR particles, especially at high temperature. [ABSTRACT FROM AUTHOR]

Dynamic mechanical properties of sulfonated butyl rubber ionomers neutralized with different amine or metallic ion (zinc or barium) and their blends with polypropylene (PP), high-density polyethylene (HDPE), or styrene-butadiene-styrene (SBS) triblock copolymer were studied using viscoelastometry. The results showed that glass transition temperatures of ion pair–containing matrix and ionic domains (Tg1 and Tg2, respectively) of amine-neutralized ionomers were lower than those of ionomers neutralized with metallic ions, and the temperature range of the rubbery plateau on the storage modulus plot for amine-neutralized ionomers was narrower. The modulus of the rubbery plateau for amine-neutralized ionomers was lower than that of ionomers neutralized with zinc or barium ion. With increasing size of the amine, the temperature range for the rubbery plateau decreased, and the height of the loss peak at higher temperature increased. Dynamic mechanical properties of blends of the zinc ionomer with PP or HDPE showed that, with decreasing ionomer content, the Tm of PP or HDPE increased and Tg1 decreased, whereas Tg2 or the upper loss peak temperature changed only slightly. The Tg1 for the blend with SBS also decreased with decreasing ionomer content. The decrease of Tg1 is attributed to the enhanced compatibilization of the matrix of the ionomer-containing ion pairs with amorphous regions of PP or HDPE or the continuous phase of SBS due to the formation of thermoplastic interpenetrating polymer networks by ionic domains and crystalline or glassy domains. [ABSTRACT FROM AUTHOR]

In this paper, the effect of the inclusion of ethylene/vinyl alcohol (EvOH) copolymer in nylon 6 is analyzed with particular attention to the transport properties. Water vapor and dichloromethane transport measurements were performed to provide useful information about polymer-polymer interaction and segmental mobility. Sorption and diffusion tests were carried out at 25°C at several activities to determine both sorption isotherm and diffusivities. Moreover, permeability tests to gases (CO2, O2) were carried out at 30°C. The obtained results indicate the existence of strong hydrogen-bonded interactions of the two polar groups (amidic of nylon 6 and hydroxyl of EvOH) within the amorphous phase. This interaction strongly influences the transport properties of the nylon 6 amorphous component. [ABSTRACT FROM AUTHOR]