Effects of Montmorillonite on the Nonisothermal Crystallization Behavior of the Poly(trimethylene terephthalate)/Polypropylene/Montmorillonite Nanocomposites

Organic montmorillonite (MMT) reinforced poly(trimethylene terephthalate) (PTT)/ polypropylene (PP) nanocomposites were prepared by melt blending. The effects of MMT on the nonisothermal crystallization of the matrix polymers were investigated using differential scanning colorimetry (DSC) and analyzed by the Avrami equation. The DSC results indicated that the effects of MMT on the crystallization processes of the two polymers exhibited great disparity. The PTT's crystallization was accelerated significantly by MMT no matter whether PTT was the continuous phase or not, but the thermal nucleation mode and three-dimensional growth mechanism remained unchanged. However, in the presence of MMT, the PP's crystallization was slightly retarded with PP as the dispersed phase, and was influenced little with PTT as the dispersed phase. When the MMT content was increased from 2_wt% to 7_wt%, the crystallization of the PTT phase was slightly accelerated, whereas the crystallization of the PP phase was severely retarded, especially at lower temperatures. Moreover, the nucleation mechanism for the PP's crystallization changed from a thermal mode to an athermal one. In the polypropylene-graft-maleic anhydride (PP-g-MAH) compatibilized PTT/PP blends, with the addition of 2_wt% MMT during melt blending, the T _c (PTT) shifted 7.8°C to lower temperature and had a broadened exotherm, whereas the T _c (PP) shifted 17.1°C to higher temperature, with a narrowed exotherm. TEM analysis confirmed that part of the PP-g-MAH was combined with MMT during blending.     

Microstructures and Mechanical Properties of Poly(Trimethylene Terephthalate)/Maleic Anhydride Grafted Poly(Ethylene-octene)/Polypropylene Blends

A range of blends based on 70 wt% of poly(trimethylene terephthalate) PTT with 30 wt% dispersed phase were produced via melt blending. The dispersed phase composition was varied from pure maleic anhydride grafted poly(ethylene-octene) (POE-g-MA) over a range of POE-g-MA:polypropylene (PP) ratios. The micromorphology and mechanical properties of the ternary blends were investigated. The results indicated that the domains of the POE-g-MA are dispersed in the PTT matrix, and at the same time the POE-g-MA encapsulate the PP domains. The interfacial reaction between the hydroxyl-end group of PTT and maleic anhydride (MA) during melt blending changes the formation from “isolated formation” to “capsule formation,” where the PP domains are encapsulated by POE-g-MA. Compared to the PTT/POE-g-MA blends, mechanical properties of ternary blends, such as tensile strength and Young's modulus, were improved significantly.     

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.     

Isothermal Melt Crystallization Kinetics for Poly(Trimethylene Terephthalate)/Poly(Butylene Terephthalate) Blends

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 _∞=T _g – 30), together with experimentally determined values of T _m ⁰ and T _g, the nucleation parameter, K _g, for PTT, PBT, and PTT/PBT blends was estimated based on the Lauritzen–Hoffman theory.     

Fabrication of Polypropylene/Poly (Trimethylene Terephthalate) Blend Fibers with Highly Improved Resiliency and Preserved Mechanical Properties

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.     

Crystallization Behavior of Poly(Trimethylene Terephthalate)/Polycarbonate Blends

The crystallization behavior of poly(trimethylene terephthalate (PTT) in compatibilized and uncompatibilized PTT/polycarbonate (PC) blends are investigated in the research reported in this paper. The differential scanning calorimetry (DSC) results showed that the crystallization behaviors of PTT/PC blends were very sensitive to PC content. The onset (T_ci) and the peak (T_c) crystallization temperatures shifted to lower temperatures whereas the area of the exotherm decreased quickly as the PC content was increased. The Avrami exponent, n, decreased from 4.32 to 3.61 as the PC content was increased from 0 to 20 wt %, and the growth rate constant, Z _c , decreased gradually as well. This suggests that the nucleation mechanism exhibits the tendency of changing gradually from a thermal nucleation to an athermal mode although the growth mechanism still remains three‐dimensional. When epoxy (2.7 phr) was added as a compatibilizer during melt blending, the T_ci and T_c shifted slightly to higher temperature (≤2°C), and the crystallization enthalpy, however, exhibited an increased crystallinity with the exception of the 90/10/2.7 phr PTT/PC/Epoxy. This suggests that the epoxy make a positive contribution to the PTT crystallization. Moreover, the influences of epoxy on the crystallization behaviors of PTT/PC blends are related to the epoxy content. By contrast, the compatibilizer of ethylene‐propylene‐diene copolymer graft glycidyl methacrylate (EPDM‐g‐GMA, ≤6.3 phr) had little effect on the crystallization behavior of PTT/PC blends. For PTT/PC/Epoxy (2.7 phr) blends, the Avrami exponent, n, decreased to near 3, while the growth rate constant, Z _c , increased slightly as PC content was increased from 0 to 20 wt %. It is suggested that epoxy accelerated the process of the nucleation mechanism changing from thermal nucleation to an athermal mode. The EPDM‐g‐GMA had little effect on the nucleation mode and spherical growth mechanism. The PTT spherulite morphologies in PTT/PC blends were very sensitive to blend composition. Completely different morphologies were observed in pure PTT, PTT/PC, PTT/PC/Epoxy, and PTT/PC/EPDM‐g‐GMA blends.     

Influence of Polycarbonate on the Crystallization Behavior of Poly(Trimethylene Terephthalate)/Polycarbonate Blends

To determine the factors influencing the retardation of the crystallization of poly(trimethylene terephthalate) (PTT) when PTT is blended with polycarbonate (PC), different PTT/PC blends were prepared via the melt mixing method. The relationships between the crystallization behavior and blend composition, as well as the phase morphology, were investigated. The results showed that the predominant reason for the retardation in crystallization is due to the PC content and phase morphology. The PC influences the crystallization of PTT via two methods. First, it retards PTT crystallization. Secondly, the PC exhibits a nucleation effect on the PTT crystallization which is, however, much weaker compared to the negative effect PC exerts with regards to PTT crystallization. When the processing temperature and shear rate remains unchanged, the two effects of PC determine the crystallization behavior of the blend. The phase morphology, which is strongly dependent on the mixing temperature and the shear rate, and which is also related to mixing time, had an appreciable impact on PTT crystallization. In the case of similar adhesion with the interface, a finer PC phase domain would show a slightly stronger nucleation effect on PTT crystallization.     

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.     

Isothermal Crystallization and Miscibility of Isotactic Polypropylene/Poly(cis-butadiene) Rubber Blends

Isotactic polypropylene/poly(cis-butadiene) rubber (iPP/PcBR) blends were prepared by melt mixing. Isothermal crystallization and miscibility for neat iPP and blends of iPP/PcBR were investigated by differential scanning calorimetry. The presence of PcBR remarkably affected isothermal crystalline behaviors of iPP. An addition of PcBR caused shorter crystallization time and a faster overall crystallization rate, meaning a heterogeneous nucleation effect of PcBR upon crystallization of iPP. For the same sample, the crystallization peak was broader and the supercooling decreased as the crystallization temperature increased. The Avrami equation was suitable to describe the primary isothermal crystallization process of iPP and blends. The addition of PcBR led to an increase of values of the Avrami exponent n, which we suggest was because the blends had a stronger trend of instantaneous three-dimensional growth than neat iPP. The equilibrium melting point depression of the blends was observed, indicating that the blends were partly miscible in the melt.     

Mechanical Property,Crystal Morphology,and Nonisothermal Crystallization Kinetics of Poly(Trimethylene Terephthalate)/Maleinized Acrylonitrile-Butadiene-Styrene Blends

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.     

Morphology,Rheology, and Mechanical Properties of Polylactide/Poly(Ethylene-co-octene) Blends

Polylactide (PLA)/poly(ethylene-co-octene) (POE) blends containing ethylene-glycidyl methacrylate copolymer (EGMA) as a compatibilizer were prepared by melt blending. An immiscible, two-phase structure with POE dispersed in the PLA matrix was observed by scanning electron microscopy. It was found that the POE particle size was significantly decreased by the addition of EGMA, and the POE particle size and distribution decreased with the increase of the compatibilizer content up to 2% EGMA, beyond which the POE particle size and distribution remained unchanged. The reactions between the epoxy groups of EGMA and carboxylic or hydroxyl groups of PLA were elucidated by the Fourier transform infrared spectroscopy. Rheological results showed that the G′(ω), G″(ω), and complex viscosity of PLA/POE blends significantly increased at low frequencies with the addition of EGMA. The failure mode changed from brittle fracture of the neat PLA to ductile fracture of the PLA/POE blends.     

Manufacture and Characterization of Poly (butylene terephthalate) Nanofibers by Electrospinning

Poly (butylene terephthalate) (PBT) nanofiber mats were prepared by electrospinning, being directly deposited in the form of a random fibers web. The effect of changing processing parameters such as solution concentration and electrospinning voltage on the morphology of the electrospun PBT nanofibers was investigated with scanning electron microscopy (SEM). The electrospun fibers diameter increased with rising concentration and decreased by increasing the electrospinning voltage, thermal and mechanical properties of electrospun fibers were characterized by DSC and tensile testing, respectively.     

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.     

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.     

Toughened Poly(Trimethylene Terephthalate) by Blending with a Functionalized Metallocenic Poly(Ethylene-Octene) Copolymer

New toughened poly(trimethylene terephthalate) (PTT) materials were obtained by melt blending with maleic anhydride grafted poly(ethylene-octene) (POEg). Rheological properties, mechanical properties, and morphological characteristics of PTT/POEg blends at four different compositions—95/5, 90/10, 80/20, and 70/30—were studied. The melt viscosity of the blends shows a linear decrease on increasing the POEg content. The addition of rubbery POEg to the PTT matrix increases the impact strength, while tensile properties decrease. Scanning electron microscopy (SEM) displayed a very good dispersion of POEg particles in the PTT matrix. Differential scanning colorimetry (DSC) experiments showed that for all samples the melting point was almost constant and the crystallinity did not show obvious differences. SEM results showed shear yielding of the PTT matrix was the major toughening mechanism.     

Compatibilization of Poly(Trimethylene Terephthalate)/Polycarbonate Blends by Epoxy. Part 2. Melting Behavior and Spherulite Morphology

The melting behaviors of poly(trimethylene terephthalate)/polycarbonate (PTT/PC) blends, compatibilized by epoxy, and PTT spherulite morphology in the blends were investigated. When epoxy was present during blending, the melting behaviors of PTT/PC blends changed substantially; glass transition temperatures (T_g's) and cold crystallization temperature (T_cc's) of the PTT‐rich phase shifted to higher temperatures, while T_m's shifted slightly to lower temperatures, indicating that epoxy suppressed considerably all processes of dynamic movements pertinent to molecular (or segmental) movements. The cold crystallization process responded sensitively to thermal history. Changes of T_cc's with composition suggested that the epoxy's compatibilization effect was pronounced when PTT and PC were in near equal content.

Recrystallization or reorganization exotherms appeared before melting for isothermally crystallized PTT/PC and PTT/PC epoxy (E) blends. A wide angle X‐ray diffraction (WAXD) analysis showed that, although the perfection of PTT crystallites was influenced either by PC content and the presence of compatibilizer or by the crystallization temperature and crystallization time, PTT's crystal structure was independent of these variables.

The polarized light microscopy (PLM) observations showed that PTT spherulite morphology was very sensitive to blend composition. Epoxy addition interfered severely with the growth of PTT spherulites, causing them to be much less developed. When the spherulites grew under a condition of varied composition, they would exhibit diversified spherulite morphology, though in one spherulite.     

Rheological Behaviors of Polypropylene/Poly(1-butene) Blends

The rheological behaviors of polypropylene (PP)/poly(1-butene) (PB) blends with homo-polypropylene (PP₁) or impact polypropylene (PP₂), a poly(propylene-co-ethylene) as the PP component were studied. With increasing of PB resin content for both PP/PB blends, the blends showed higher G'(ω), G''(ω) and η*(ω) at low frequencies but lower values at high frequencies which implied that the processability was improved. A two-phase morphology was observed through the various rheological responses, including G'(ω)-ω terminal region curves, Cole-Cole plots and the weighted relaxation spectra with the PB contents up to 40?wt%. With the same PB content, the rheological parameters of the PP₂/PB blends were quite different from those of the PP₁/PB, which can be attributed to the stronger interaction between PB chains and the ethylene-co-propylene copolymer in PP₂. The impact strength of the PP₂/PB blends was improved dramatically over that of the PP₁/PB. The more significant toughening effect for the PP₂/PB blends can be attributed to the special responses of its rheological behaviors.     

Phase Structure,Thermal, and Mechanical Properties of Polypropylene/Hollow Glass Microsphere Composites Modified with Maleated Poly(ethylene-octene)

Maleated poly(ethylene-octene) (POE-g-MAH), as a compatilizer and toughener, was incorporated in polypropylene/hollow glass microspheres (PP/HGM) binary composites, and the phase structure and thermal and mechanical properties of these composites were investigated. Scanning electron microscopy analysis indicated that the phase structure of ternary composites could be controlled by POE-g-MAH and the surface treatment of HGM. Fourier transform infrared spectroscopy revealed that there was an amidation reaction between the treated HGM and POE-g-MAH during melt compounding. Differential scanning calorimetry suggested that the crystallization and melting behaviors of ternary composites were influenced by phase structure. Evaluation of mechanical properties showed that the amide linkage between the treated HGM and POE-g-MAH was favorable for improving the properties of ternary composites.     

The Effect of Poly(Ethylene Succinate) on Mechanical Properties of PLLA/PES Blend Prepared by Melt-Blending

Fully biodegradable poly(L-lactide) and poly(ethylene succinate) (PLLA/PES) blends were prepared via melt-blending using PLLA and PES as reactants in a stainless steel chamber. The prepared PLLA/PES blend, as well as neat PLLA and PES, was characterized by Fourier transform infrared spectra (FTIR) and X-ray diffraction (XRD) to confirm the structure and the crystallization of PLLA in the blend. The mechanical properties of PLLA/PES blends were determined by bending and tensile tests and the effects of PES content on the mechanical properties of PLLA/PES blends were investigated. It was found that blending some amount of PES could significantly improve the elongation at break while still keeping considerably high strength and modulus. With increasing PES content, both strength and modulus gradually decreased; however the elongation at break significantly increased. SEM was used to examine the morphology of fracture surfaces of PLLA/PES blends.     

On Localization of Clay Nanoparticles in Polypropylene/poly(Lactic Acid) Blend Nanocomposites: Correlation with Mechanical Properties

Two polypropylene (PP)/polylactide (PLA)/clay ternary nanocomposite systems, i.e. PP-rich and PLA-rich ones, each containing various amounts of one of two types of clay, were prepared by one step melt compounding in a twin screw extruder. The microstructures of the developed systems were correlated with tensile and impact properties. A theoretical calculation using wetting coefficients was used for predicting the clay nanoparticles localization in the blends. The nanoparticles were almost completely located within the PLA phase in both the PP-rich and PLA-rich systems, in good agreement with the predictions. Addition of a compatibilizer led to localization of the nanoparticles at the interfaces of the blends. From the wide angle X-ray scattering (WAXS) spectra it was concluded that the incorporation of clay led to intercalated structures in the both systems. The increase in impact toughness of the compatibilized blend nanocomposites, with respect to the uncompatibilized ones, was attributed to the weakened interfacial debonding in the presence of the interfacial-localized nanoparticles.