Morphological and Rheological Properties of Poly(Trimethylene Terephthalate)/Maleic Anhydride Grafted Poly (Ethylene-Octene)/Organoclay Ternary Nanocomposite

Poly(trimethylene terephthalate) (PTT)/poly(ethylene-octene) POE-g-MA/organoclay ternary nanocomposites were prepared using melt blending in order to simultaneously improve the toughness and stiffness of PTT. The phase morphology and dispersion of organoclay were characterized by scanning electron microscope (SEM), X-ray diffractometer (XRD), and transmission electron microscopy (TEM). The melt rheological behavior of the ternary nanocomposites was determined by plate/plate rheological measurements. XRD and TEM analysis indicated that the ternary nanocomposites contained exfoliated nanoparticle when a small amount of organoclay (1 part per hundred) was added. The high aspect ratio of the organoclay platelets induced the average size of the dispersed domain to become smaller. Melt rheological studies revealed that the ternary nanocomposites exhibited strong shear thinning behavior and showed good processability.     

Effect of Surfactant Concentration on Thermal and Mechanical Properties of Poly(Butylene Succinate)/Organoclay Composites

Composite materials consisting of poly(butylene succinate) (PBS) and montmorillonite (MMT), modified to various extents using trihexyltetradecylphosphonium chloride (THTDP) cations, were prepared using a simple melt intercalation technique. The surfactant contents were varied, i.e. 0.4, 0.6, 0.8, 1.0, and 1.2 times the cation exchange capacity (CEC) of the MMT. The intercalation of the surfactant molecules into MMT layers, confirmed by the increase in interlayer spacing and significant changes in the morphology of the modified MMT, facilitated the dispersion of the clay in the PBS matrix. The properties of the PBS-based composites were changed with increasing surfactant content. The melting and crystallization temperatures increased and the degree of crystallinity (χ_c) decreased. The storage modulus was significantly enhanced below the glass transition temperature (Tg), and Tg shifted to a higher temperature, with a maximum at a surfactant loading of 0.6 CEC. The mechanical properties, including tensile strength, flexural strength, flexural modulus and impact strength, increased and then decreased with surfactant loading, with the maximum observed also at a surfactant loading of 0.6 CEC. In conclusion, an ideal balance between thermal and mechanical properties can be obtained at a surfactant quantity equivalent to 0.6 times the clay CEC. Moreover, all the composites exhibited obvious improvement in thermal and mechanical properties as compared to those of neat PBS.     

Rheological Properties and Microstructures of Hydroxyethyl Cellulose/Poly(Acrylic Acid) Blend Hydrogels

A simple in-situ method was introduced to prepare hydroxyethyl cellulose/poly(acrylic acid) (HEC/PAA) blend hydrogels by forming an interpenetrating network (IPN). Storage modulus (G′) and loss modulus (G″) were improved dramatically compared to HEC. To prove that hydrogen bonds and chemical crosslinking played major roles in improving the hydrogel strength and toughening, and to optimize the components of HEC/PAA blend hydrogels, a series of blend hydrogels with different ratios of HEC to PAA were designed and the corresponding Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), rheological tests, and swelling properties were compared. Crosslinked HEC/PAA blend hydrogel (mol/mol = 1:1) showed the best properties appropriate for opening up biomedical applications of the hydrogel.     

Microstructure,Interfacial Interactions,and Rheological Properties of PC/AES/Montmorillonite Composites

Polycarbonate (PC) and acrylonitrile–EPDM (ethylene/propylene/diene elastomer)–styrene ter‐polymer (AES) blends and PC/AES/organically modified montmorillonite (OMMT) composites were prepared at 20%, 40%, 50% by weight of AES and 3% by weight of OMMT. The microstructure, interfacial interactions, and rheological properties of the PC/AES blends and PC/AES/OMMT composites were studied systematically. X‐ray diffractometer (XRD) results reveal that the AES is easier to intercalate into OMMT than PC, and the content of AES has a little effect on the interlayer distance of OMMT. Wetting coefficient calculation indicates that OMMT distributes primarily at the interface of the polymer blend. Field emission scanning electron microscope (FE‐SEM) observation indicates that the phase morphology of PC/AES blends and PC/AES/OMMT composites is not influenced by the OMMT. However, linear rheological properties suggest that the addition of OMMT has a great effect on the linear rheological property.     

Reactive Compatibilization of Poly(Butylene Terephthalate)/Acrylonitrile-Styrene-Acrylate Blends by Epoxy Resin: Morphology and Mechanical Properties

The effect on the notched Izod impact strength of poly(butylene terephthalate) (PBT) by blending it with acrylonitrile-styrene-acrylate (ASA) was examined. Epoxy resin (ER) was demonstrated to be an efficient compatibilizer for the partially compatible blends of PBT/ASA. It requires only a very small amount of ER to improve the toughness of the PBT/ASA blends drastically. Furthermore, there exists an optimum proportion of ER added to achieve maximum notched Izod impact strength. Transmission electron microscopy (TEM) observation suggests that the ER in the PBT/ASA/ER blends suppressing the tendency of coalescence of ASA, leading to better dispersion of the ASA particles. Field emission scanning electron microscopy (FESEM) shows that ER enhances the phase dispersion and the interfacial adhesion between the PBT and ASA phases, it improves the compatibility between PBT and ASA. The compositions in the interphase was continuous, which results in multiphase composites with a graded interphase. It is suggested that enhanced interphase adhesion was necessary to obtain improved dispersion, fine phase morphology, and better toughness.     

A Novel Potential Ecomaterial Based on Poly(p-Dioxanone)/Montmorillonite Nanocomposite With Improved Crystalline,Processing, and Mechanical Properties

Poly(p-dioxanone) (PPDO) is a useful biomaterial and potential ecomaterial due to its biodegradability and good mechanical properties. Like other aliphatic polyesters, however, it has a low crystallization rate and low melt strength; it is difficult to produce thin films from it by blown film processing. In this work, poly(p-dioxanone)/montmorillonite (MMT) nanocomposites have been prepared successfully by in situ ring-opening polymerization of p-dioxanone and MMTs. The novel, biodegradable nanocomposites have a remarkably increased crystallization rate and melt strength; moreover, they can be blown into thin films, which have excellent mechanical properties. A typical sample showed a tensile strength of 59.2 MPa and elongation at break 605%.     

Microstructure and Properties of Polypropylene/Clay Nanocomposites

Nanocomposites of polypropylene (PP) containing various contents of Cloisite 15A nanoclay particles were prepared by one-step melt compounding in a twin screw extruder. Tensile and impact properties of the nanocomposite systems were investigated and correlated with their microstructures. The tensile modulus increased with an increase in Cloisite 15A content but the tensile strength, elongation at break, and impact strength were decreased. WAXS and TEM studies showed almost exfoliated structures. There was a decrease in permeability values with an increase in nanoclay content up to 5 wt. %. Exceeding this content of nanoclay had no significant effect on permeation due to the aggregation phenomenon at high concentrations of the nanoparticles. Most of the examined micromechanical models for prediction of the tensile modulus of the nanocomposite were successful despite being based on fiber-shaped fillers. An exfoliated structure of clay within the nanocomposite was assumed for the modeling using a molecular dynamics simulations approach, employing Dreiding, Forcite, and COMPASS force fields, in order to investigate the best one for a successful estimation of elastic modulus. Relative to the experimental modulus values of the nanocomposites, which were around 1100–1200 MPa, the COMPASS force field had the best correlation with the values with a slight departure of about 10%.     

Preparation and Properties of Poly(ethylene terephthalate)/Silica Nanocomposites

A kind of poly(ethylene terephthalate) (PET)/Silica nanocomposite (PETS) was synthesized via in situ polymerization using the compatibility between silica nanoparticles and ethylene glycol (EG). Transmission electron microscopy (TEM) micrographs revealed that the silica nanoparticles were well dispersed in the PET matrix, the particle size was about 10 nm with narrow distribution, and there existed strong interaction between the particles and the polymer chains. Differential scanning calorimetry (DSC) results indicated that the thermal properties of PETS with 2 wt% silica (PETS‐2) are different from those of pure PET (PETS‐0). The properties of the as‐spun fibers show that the tenacity and LASE‐5 (load at a specified elongation of 5%) of PETS‐2 were higher than those of PETS‐0, while the heat shrinkage of PETS‐2 was lower than that of PETS‐0. We suggest that the increasing of crystallinity and the strong interface interaction of the nanocomposite caused the fibers of PETS‐2 to not only have higher tenacity and LASE‐5 but also to have lower heat shrinkage.     

The Peculiar Temperature Response of Dynamic Rheological Behaviors of Poly (Vinyl Chloride)/trioctyl Trimellitate (100/70) System

The dynamic rheological behavior, application of time-temperature superposition (TTS) and the failure mechanism of TTS are studied for the poly(vinyl chloride) (PVC)/trioctyl trimellitate (TOTM) (100/70) system. The Arrhenius equation, Williams–Landel—Ferry (WLF) equation, mathematical non-linear fitting and manual shift are applied to TTS fitting. For the PVC/TOTM (100/70) system, none of those methods can give well-superimposed master curves with either single horizontal shift or two-dimensional (horizontal and vertical) shift. The failure reason is attributed to the thermorheological complexity of the PVC/TOTM (100/70) system. Curves of the storage modulus versus the frequency can be well fitted with an empirical equation (G′=G′₀+Kω ⁿ ) usually used to describe filled polymer systems, indicating the multilevel flowing unit characteristic in this system. With the increase of test temperature, the structure of the PVC/TOTM (100/70) system changes and an apparent transition appears in the rheological behavior. Differential scanning calorimetry (DSC) results reveal that for the PVC/TOTM (100/70) system there are microcrystallites present below 220°C, but above the rheological transition temperature (190°C) the bulk of the microcrystallites melted, which corresponds to the appearance of viscous flow participating in the rheological behavior. It verifies the fact that the gel networks crosslinked by microcrystallites dominate the rheological behavior below the transition temperature in the PVC/TOTM (100/70) system. The quantity of microcrystallites remaining in the melt determines the perfection of the physical gel networks. With the increase of test temperature, the microcrystallites melted gradually and the gel networks are broken up.     

Crystallization,Flame Retardancy and Mechanical Properties of Poly(Butylene Terephthalate)/Brominated Epoxy/Nano-Sb2O3 Composites Dispersed By High Energy Ball Milling

Nano-Sb2O3 particles and brominated epoxy resin (BEO) powders were dispersed in poly (butylene terephthalate) (PBT) by high energy ball milling (HEBM). Then the nanocomposites were prepared by a twin screw extruder. The influence of the nano-Sb2O3 particles on the crystallization, thermal stability, flame retardancy and mechanical properties of the PBT/BEO/nano-Sb2O3 composites were investigated by X-ray diffraction (XRD), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), limiting oxygen index (LOI), UL-94 tests and scanning electron microscopy (SEM). The results showed that the nano-Sb2O3 particles improved the crystallizability, thermal stability and flame retardancy properties of the PBT/BEO/nano-Sb2O3 composites. When the content of nano-Sb2O3 particles was 2.0?wt%, the LOI of nano-Sb2O3/BEO/PBT composites increased from 22.0 to 27.8 and the tensile strength reached its maximum value (62.44?MPa), which indicated that the optimum value of flame retardancy and mechanical properties of PBT/BEO/nano-Sb2O3 composites were obtained.     

Preparation and Characterization of Composites Based on Poly (Butylene Succinate) and Poly (Lactic Acid) Grafted Tetracalcium Phosphate

Tetracalcium phosphate (TTCP, Ca₄(PO₄)₂O) was functionalized by poly (l-lactic acid) (PLLA) in order to improve the dispersion of TTCP particles in poly (butylene succinate) (PBS) matrices, and then a series of the PLLA grafted TTCP/PBS (g-TTCP/PBS) composites were prepared via melt processing. Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), tensile analysis, differential scanning calorimetry (DSC), thermogravimetric analysis (DTG/TGA) and melt rheological analysis were used to investigate the structure and properties of the g-TTCP/PBS composites. The results revealed that l-lactide could be grafted onto the surface of TTCP, and the g-TTCP/PBS composites showed the best mechanical properties when the content of g-TTCP was 10 wt%. The crystallization temperature of g-TTCP/PBS composites tended to increase with the increase of g-TTCP contents. The functionalized particles played an important role in augmenting the thermal degradation rate and the complex viscosity of the composites due to their unique structure and the reasonable interfacial interaction between the particles and PBS matrix.     

Influence of Reactive Compatibilizer on the Morphology,Rheological, and Mechanical Properties of Recycled Poly(Ethylene Terephthalate)/Polyamide 6 Blends

Recycled poly(ethylene terephthalate) (R-PET) and virgin polyamide 6 (PA6) blends compatibilized with glycidyl methacrylate grafted poly(ethylene-octene) (POE-g-GMA) were melt blended. The morphological, rheological and mechanical properties of the prepared blends were investigated by scanning electron microscopy, rheology, and an electromechanical testing instrument, respectively. All of the blends showed a droplet dispersion type morphology, and the PA6 particle size decreased with increase in the POE-g-GMA concentration. The storage modulus (G′), loss modulus (G′′), and complex viscosity (η*) of the blends significantly increased at low frequency with the addition of POE-g-GMA. In addition, ‘‘Cole-Cole’’ plots showed that the elasticity of the blends was also increased by raising the compatibilizer dosage. It was also found that 10 wt% of POE-g-GMA caused 88.46 and 171.05% increments in Charpy impact strength and elongation at break with only a 21.66% decrement in tensile strength.     

Thermal,Mechanical, and Rheological Characterization of Polylactic Acid/Halloysite Nanotube Nanocomposites

Halloysite nanotube (HNT) clay and biodegradable polylactic acid (PLA) nanocomposites were fabricated by a melt-blending method with five different clay levels (1, 3, 5, 7, and 9 wt%). The effect of HNT loading on the thermal and mechanical properties of the PLA/HNT nanocomposites was examined by thermogravimetric analysis and universal tensile testing, respectively. Morphological characteristics were investigated by transmission electron microscopy. The composites' melt rheological characteristic analyses were conducted using a rotational rheometer in both steady-shear and oscillatory dynamic testing modes. The data were found to be well-analyzed using the Carreau model, Cox–Merz rule, modified Cole–Cole plot, and van Gurp–Palmen plot.     

Tearing and Rheological Properties of Fully Biodegradable Poly(Lactic Acid)/Poly(Ethylene Glutaric-Co-Terephthalate) Copolyester Blends

The tearing and rheological properties of poly(lactic acid) (PLA)/poly(ethylene glutaric-co-terephthalate) copolyester (FP) blends were investigated using a wide range of blending ratios. The tearing strength values of PLA/FP were always significantly higher than that of the PLA specimen. The melt flow indexer and capillary rheometer analyses indicated that the viscous flow became difficult and the melt strength of PLA was improved after the addition of FP. The interactions between the molecular chains of PLA and FP adds FP branching and lengthens the macromolecular chains and the degree of macromolecular entanglement increases. The blends with 5 wt% FP reached the maximum melt strength and minimum flow index n, while the tearing strength approached the maximum level. At higher FP contents, the melt flow properties PLA/FP blends increased and the melt strength decreased, the tearing strength of PLA/FP blends also decreased.     

Steady Shear Rheological Behavior,Mechanical Properties,and Morphology of the Polypropylene/Carbon Nanotube Nanocomposites

Nanocomposites based on polypropylene (PP) and multiwall carbon nanotubes (MWNT) have been prepared through melt blending. Scanning electron microscopy (SEM) observations indicate that nanotubes were dispersed almost homogeneously throughout the matrix; however, some aggregates were also observed at high nanotubes loading. Rheological studies showed that at low shear rates, there is an increase in steady shear viscosity and shear stress of samples with increasing of nanotubes concentration. However, at high shear rates nanocomposites behave like pure PP. The activation energy of flow showed an increasing trend and has a maximum at 1wt% MWNT content. It was found that incorporation of nanotubes causes a remarkable decrease in surface and volume resistivity values of the polymeric matrix. The presence of CNTs improved the tensile and flexural properties of the polymeric matrix.     

Preparation and Properties of Antimicrobial Poly(butylene adipate-co-terephthalate)/TiO2 Nanocomposites Films

Abstract

Poly(butylene adipate-co-terephthalate) (PBAT) nanocomposite films with various contents of nano-titanium dioxide (TiO₂) and titanium dioxide doped silver (Ag-TiO₂) were prepared by a solvent casting method. The TiO₂ and Ag-TiO₂ nanoparticles were surface-modified with silane coupling agents to improve their compatibility and dispersibility in the PBAT matrix. They were denoted as mTiO₂ and mAg-TiO₂, and were characrterized by Fourier transform infrared (FTIR) spectroscopy and transmission electron microscopy (TEM). The morphology of the PBAT nanocomposite films was studied by field emission scanning electron microscopy (FE-SEM). The crystallinity of the PBAT film increased upon the introduction of the nano-TiO₂/Ag-TiO₂. Its mechanical properties and gas barrier properties were also significantly improved. In addition, the PBAT/mTiO₂ and PBAT/mAg-TiO₂ nanocomposite films showed a strong antibacterial activity against Gram-negative (Escherichia coli) and Gram-positive (Staphylococcus aureus) food-borne pathogenic bacteria.     

The Microstructure and Swelling Properties of Poly Acrylic Acid-Acrylamide Grafted Starch Hydrogels

Starch grafted acrylic acid-acrylamide hydrogel was synthesized using an aqueous solution polymerization method. The microstructures of the vacuum-dried hydrogel (VDH) and vacuum-freeze-dried hydrogel (VFDH) were studied by means of scanning electron microscopy and biomicroscopy. The water-absorption rate of the hydrogel was tested. The results showed that the microstructure of the two kinds of dried hydrogels exhibited significant differences. Before absorbing water, VDH had a relatively dense surface whereas the surface of VFDH had a clear macroporous structure. After absorbing water, a three-dimensional network structure was clearly visible in VDH. Many interlaced and free filaments occupied the space between the main skeleton and channels. The holes formed by vacuum-freeze-drying had the effect of squeezing the surrounding network structure, which had an impact on the water-absorption rate and water absorbency of the hydrogel.     

Preparation,Morphology and Properties of Poly(Trimethylene Terephthalate)/Thermoplastic Polyester Elastomer Blends

Poly(trimethylene terephthalate)(PTT)/thermoplastic polyester elastomer (TPEE) blends were prepared and their miscibility, crystallization and melting behaviors, phase morphology, dynamic mechanical behavior, rheology behavior, spherulites morphology, and mechanical properties were investigated by differential scanning calorimetry (DSC), scanning electron microscopy (SEM), dynamic mechanical analysis (DMA), parallel-plate rotational rheometry, polarized optical microscopy (POM), wide angle X-ray diffraction (WAXD), universal tensile tester and impact tester, respectively. The results suggested that PTT and TPEE were partially miscible in the amorphous state, the TPEE rich phase was dispersed uniformly in the solid matrix with a size smaller than 2 μm, and the glass transition temperatures of the blends decreased with increasing TPEE content. The TPEE component had a good effect on toughening the PTT without depressing the tensile strength. The blends had improved melt viscosities for processing. When the blends crystallized from the melt state, the onset crystallization temperature decreased, but they had a faster crystallization rate at low temperatures. All the blends’ melts exhibited a predominantly viscous behavior rather than an elastic behavior, but the melt elasticity increased with increasing TPEE content. When the blends crystallized from the melt, the PTT component could form spherulites but their morphology was imperfect with a small size. The blends had larger storage moduli at low temperatures than that of pure PTT.     

Rheological Properties and Morphology of PC/AES Blends

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.     

Influence of Mixing Technique on Microstructure and Impact Properties of Isotactic Polypropylene/ Poly(Cis-Butadiene) Rubber Blends

Isotactic polypropylene/poly(cis-butadiene) rubber (iPP/PcBR vol%: 80/20) blends were prepared by melt mixing with various mixing rotation speeds. The effect of mixing technique on microstructure and impact property of blends was studied. Phase structure of the blends was analyzed by scanning electron microscopy (SEM). All of the blends had a heterogeneous morphology. The spherical particles attributed to the PcBR-rich phase were uniformly dispersed in the continuous iPP matrix. With increase of the mixing rotation speed, the dispersed phase particle's diameter distribution became broader and the average diameter of the separated particles increased. The spherulitic morphology of the blends was observed by small angle light scattering (SALS). Higher mixing rotation speed led to a more imperfect spherulitic morphology and smaller spherulites. Crystalline structure of the blends was measured by wide angle X-ray diffraction (WAXD) and small angle X-ray scattering (SAXS). The introduction of 20 vol% PcBR induced the formation of iPPβ crystals. Higher rotation speed led to a decrease in microcrystal dimensions. However, the addition of PcBR and the increase of mixing rotation speed did not affect the interplanar distance. The long period values were the same within experimental error as PcBR was added or the mixing rotation speed quickened. The normalized relative degree of crystallinity of the blends slightly increased under lower rotation speeds (30 and 45 rpm) and decreased under higher rotation speeds. The notched Izod impact strength of the blends was enhanced as a result of the increase of mixing rotation speed.