Analysis of phase structure and evolution of PP/PEOc blends during quiescent molten-state annealing process from SEM patterns. Part I: droplet/matrix morphology

This work was aimed at studying the phase structure and evolution of polypropylene (PP)/poly(ethylene-1-octene) copolymer (PEOc) blends with droplet/matrix morphology using scanning electron microscopy (SEM) during quiescent molten-state annealing process. The structure parameters, such as the area diameter, d _p , and number average diameters, D _n , of the dispersed phase in PP/PEOc blends were calculated by pattern analysis of SEM images. Moreover, the potential fractal behavior of the phase structure and morphology of PP/PEOc?=?80/20 blend during the process was discussed. The histograms of $ P\left( {{d_p \left/ {{{{\overline{d}}_p}}} \right.}} \right) $ obtained at various annealing time fell on a master curve, demonstrating the self-similar growth of the phase structure of the blends during quiescent molten-state annealing process.     

SiO_2纳米粒子对PMMA/PS共混物共连续相结构退火粗化过程的影响

考察了亲水性纳米SiO2粒子的加入对聚甲基丙烯酸甲酯/聚苯乙烯(PMMA/PS)共混体系的共连续相结构在静态高温退火时形态稳定性的影响,发现静态高温退火条件下,填充体系共连续组成范围变窄幅度较小、特征结构尺寸的粗化速率减慢.流变测试表明纳米SiO2粒子加入之后PMMA/PS共混体系的黏弹性显著提高,从而能减缓破坏构成共连续相结构的纤维断裂或回缩等松弛过程的速率,有效地抑制PMMA/PS共混体系的共连续相结构粗化进程,提高相结构的稳定性.根据现有的两种粗化理论的定性分析表明,在高填充量的共混体系中,加入纳米SiO2粒子导致共混体系的黏弹性的显著改变是影响PMMA/PS共混体系在静态高温退火时共连续相结构粗化速率的主要因素,相对而言界面张力的变化对共连续相结构在静态高温退火时的粗化速率影响则应该较小.     

The morphology and growth of PLA stereocomplex in PLLA/PDLA blends with low molecular weights

The linear poly(L-lactide) and poly(D-lactide) (PLLA, PDLA) with relative lower molecular weights were synthesized, and PLLA/PDLA blends at various content of PDLA were prepared by solution casting. The morphology and growth of poly(lactide) stereocomplex (PLA SC) were investigated by polarized optical microscope. Results revealed that the morphology of SC in the blends strongly depended on the content of PDLA and the annealing temperature. Dendritic and irregular SC with looser structure developed in the specimens with lower content of PDLA, and regular SC spherulites with birefringent and compact structure produced in the specimens with higher content of PDLA. The growth rate (G) of SC increased gradually as the content of PDLA enhanced in the blends. As the annealing temperature enhanced, the SC with brighter and more compact structure appeared. The G value increased at first before declining as the annealing temperature elevated from the 130 to 190°C. And the nonlinear behavior of the growth of SC in the dissimilar specimens was analyzed.     

Suppressed coalescence of dispersed viscous poly(methyl methacrylate) phase in polystyrene matrix by glass beads

The effect of glass beads (GB) on morphology of polystyrene (PS)/poly(methyl methacrylate) (PMMA) blends has been studied by scanning electron microscopy (SEM) at different shear rates and during quiescent annealing. For the viscosity ratio of PMMA to PS greater than unity, the dispersed viscous PMMA phase in the blend coalesced during the shear flow or quiescent annealing. However, the domain size of the PMMA phase decreased significantly under shear even though a small amount of GB was added. The PMMA domain size further decreased and the size distribution became narrower with increasing GB content. According to SEM images, the quiescent coalescence of the PMMA phase was effectively inhibited by adding large amounts of GB, and the breakup of PMMA domains in shear flow was greatly favored by the high local shear prevailed between GB. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 25–35, 2009     

Investigations on structure and properties of blends of polypropylene with polyamide 1010 by Rayleigh scattering

The phase structure and morphology of polypropylene （iPP） blends with poly（decamethylene sebacamide （polyamide 1010, PA 1010） and the part-compatible alloys （iPP/PA 1010/iPP-g-MAH） are investigated by Rayleigh scattering, i.e. small angle light scattering （SALS）. The structure parameters of SALS, i.e. correlation distance, ac and average chord lengths, /, are calculated. Their variation with the composition of the blends and alloys is discussed. The morphology and structure of fracture surfaces in the blends and alloys are studied by SEM images. The average diameter of dispersed phase in the blends and alloys is calculated by graph processing. The variation of average diameter is similar as that of average chord lengths of dispersed phases. The mechanical properties of the blends and alloys are analyzed and the relation of modulus and yield stress with the composition is studied. It is confirmed that the correlation between the modulus and the structure parameters is non-linear, while the correlation between the yield stress and the composition or structure parameters is linear.     

Allylic monomers as reactive plasticizers of polyphenylene oxide. Part III – Rheological and mechanical properties

The chemorheology of blends of diallyl ortho-phthalate (DAOP) as reactive plasticizer of polyphenylene oxide (PPO) were monitored during their cure with either dicumyl peroxide (DCP) or tert-butyl hydroperoxide (TBHP), and their mechanical properties and morphology were studied. The steady shear and dynamic rheology behaviour was consistent with chemical gelation of DAOP in blends with low concentrations of PPO but the gelation behaviour at higher PPO concentrations was more complex. Dynamic mechanical thermal analysis of the blends of PPO:DAOP cured with either DCP or TBHP indicated a two phase structure. For PPO:DAOP/DCP, the lowest transition (between 150 °C and 200 °C) was attributed to a DAOP-rich phase and its T_g was higher than that for pure DAOP/DCP due to the presence of PPO in the DAOP-rich phase. The smaller damping shoulder near 250 °C was caused by a PPO-rich phase with a T_g that was lower than pristine PPO due to the presence of unpolymerized or polymerized DAOP. In contrast, the glass transition region of the PPO:DAOP/TBHP system was very broad due to an overlap of the transitions for DAOP-rich and PPO-rich phases caused by higher levels of unpolymerized DAOP. SEM observations of the blends revealed a two phase morphology with PPO-rich particles in a poly-DAOP matrix for blends with ?30 wt% PPO, a co-continuous morphology for blends with 40 wt% PPO, and a phase inverted morphology with more than 50 wt% PPO. These SEM observations agree with studies of the swelling, disintegration or dissolution of matrix of the blends in solvent.     

Reaction-induced miscibility in blends comprised of bisphenol-A polycarbonate and poly(trimethylene terephthalate)

The inherent miscibility and effects of reaction-induced changes on the phase behaviour of blends of poly(trimethylene terephthalate) (PTT) with bisphenol-A polycarbonate (PC) were studied. The as-prepared (solution-cast) blends exhibited two well-spaced and separated glass transition temperatures (T_gs) and a heterogeneous phase-separated morphology, indicating an immiscible system. However, after annealing at high temperature (at 260 °C), the blends original two T_gs merged into one single T_g, and the annealed blends exhibited a homogeneous morphology, and turned from having a semicrystalline into having an amorphous nature upon extended annealing. The annealing-induced changes of phase behaviour in the blends were analyzed. The homogenization process of the blends upon heating is attributed to chemical transreactions between the PTT and PC chain segments, as evidenced with FT-IR characterization. The IR result showed a new aryl C-O vibration peak at 1,070 cm^–1 for the annealed blends, which is characteristic of an aromatic polyester structure formed from exchange reactions between PTT and PC. The transreactions between PTT and PC led to a random copolymer comprised of PC/PTT segments, which is believed to serve as a compatibilizer at the beginning stage of transreactions, but at later stage, the random copolymer became the main species of blends and turned to a homogeneous and amorphous phase.     

Synthesis and characterization of FePt nanoparticles and FePt nanoparticle/SiO2-matrix composite films

Superparamagnetic face-centered cubic (fcc) FePt nanoparticles were synthesized using a polyol process. The effect of reaction temperature and molar ratio of Fe(CO)₅ to Pt(acac)₂ on the structure, composition and morphology of nanoparticles has been investigated. The optimum processing condition has been obtained for producing well-monodisperse fcc-phase FePt nanoparticles with the 2:1?molar ratio of Fe-Pt at 220?°C. In order to circumvent the problem of FePt particle coalescence during high temperature annealing for the L1₀ ordering, FePt nanoparticle/SiO₂-matrix composite films have been fabricated by sol?Cgel method. The experimental results confirm that the amorphous SiO₂ matrix effectively inhibits the grain growth and particle aggregation during 700?°C annealing for 1?h. Well-monodisperse face-centered tetragonal (fct) FePt particles embedded in the SiO₂ matrix can be obtained with the long-range chemical order parameter S of ~0.74, indicating partially ordered L1₀ phase transition in FePt/SiO₂ composite films. The FePt/SiO₂ system exhibits a hysteretic behavior with smaller coercive field of 1,450 Oe. The incomplete phase transition from cubic deredat height maxsium (A ₁-disordered phase to tetragonal L1₀-ordered phase) might be responsible for it.     

Nano/micro-scale morphologies of semi-interpenetrating poly(ε−caprolactone)/tung oil polymer networks: Isothermal and non−isothermal crystallization kinetics

The isothermal and non-isothermal crystallization kinetics of pure poly(ε−caprolactone) (PCL) and its blends with crosslinked tung oil were investigated as a function of composition, crystallization temperature, and heating rate using differential scanning calorimetric (DSC). The PCL/tung oil semi-interpenetrating polymer networks of different compositions were prepared via cationic polymerization of tung oil in the presence of homogenous solutions of PCL. This unique and relatively new in-situ polymerization and compatibilization blending technique created nano/micro-scale morphologies that cannot be obtained with the traditional melt-processing and/or solvent casting methods. Blends with different miscibility, phase behaviors, and morphologies (miscible, partially miscible, and immiscible) were observed as a function of composition with a constant concentration of boron trifluoride diethyl etherate (BFE) cationic initiator. The morphology of the semi-interpenetrating polymer networks was performed using scanning electron microscopy (SEM). Miscible blends with a single T_g for PCL ≤ 10 wt.%. were observed. While, on the other hand, partially miscible blends with two distinct T_gs and nanoscale morphologies and average particle sizes as small as 100 nm were observed for blends with 20 ≤ PCL wt.% ≤ 30. Immiscible blends with microscale highly interconnected, co-continuous two-phase morphology and two distinct T_gs were detected for 50 wt.% PCL. Both isothermal and non-isothermal crystallization kinetics were strongly influenced by the different miscibility and morphology of the blends. The isothermal and non-isothermal crystallization kinetics of PCL/tung oil blends were analyzed on the basis of Avrami and modified Avrami approaches, respectively. A substantial decrease in the isothermal (longer half time) and non-isothermal (T_m shifted to lower temperature) crystallization kinetics was observed as the concentration of PCL increased in the blends up to 30 wt.% due to the partially miscibility of the blends in this composition range. In a contrast, for 50 wt.% PCL blend, a considerable increase in the crystallization kinetics (isothermal and non-isothermal) was detected due to the highly interconnected, co-continuous two-phase morphology.     

Viscoelastic phase separation in polyethersulfone modified bismaleimide resin

The polymerization-induced phase separation process of polyethersulfone (PES) modified bismaleimide resin, 4,4′-bismaleimidodiphenylmethane (BDM), was investigated by time resolved light scattering (TRLS) and scanning electronic microscopes (SEM). At the blends with 10 wt% and 12.5 wt% PES, a phase inversion structure was found by SEM. TRLS results displayed clearly the spinodal decomposition (SD) mechanism and the exponential decay procedure of scattering vector q_m, which followed Maxwell-type relaxation equation. The characteristic relaxation time τ for the blends can be described by the Williams-Landel-Ferry equation. It demonstrated experimentally that the phase separation behaviors in these PES modified bismaleimide blends were affected by viscoelastic effect.     

Compatible blends of biorelated polyesters through catalytic transesterification in the melt

The transesterification during the melt blending of polylactide (PLA) and poly(butylene adipate-co-terephthalate) (PBAT) was investigated in presence of Ti(OBu)₄ as a catalyst. Both the effect of catalyst concentration and reaction duration was considered. The process was studied by analyzing the molecular weight of the polyesters by size exclusion chromatography (SEC). The rheological, thermal and morphological properties of the blends were investigated by melt flow rate, DSC and SEM analyses, respectively. Evidences about the formation of PBAT-PLA copolymers were obtained and discussed. The tensile properties of compression moulded films were also determined and correlated to the structure and phase morphology development of the blends. In particular, the use of Ti(OBu)₄ resulted in the improvement of compatibility. Moreover, the decrease in stiffness and the increase in elongation at break with the increase of mixing time was observed, in good agreement with the improved compatibility of the modified blend.     

Improvement in gas permeability of biaxially stretched PET films blended with high barrier polymers: The role of chemistry and processing conditions

Improvement in oxygen gas barrier properties of polyester/polyamide blends used in packaging industry is the main objective of the present study. For this purpose poly(ethylene terephthalate) (PET)/poly(m-xylene adipamide) (nylon-MXD6) (95/5 w/w) and poly(ethylene terephthalate-co-isophthalate) copolymer (PETI)/MXD6 (95/5 w/w) blends have been prepared with a PET copolymer which consists of 5 wt.% sodium sulfonated isophthalate (PET-co-5SIPA) as compatibilizer and a carboxyl-terminated polybutadiene (CTPB) as filler by using a co-rotating intermeshing twin screw extruder. The effects of chemical architecture and morphology on oxygen gas permeability and processability were analyzed by using a range of characterization techniques including differential scanning calorimetry (DSC), scanning electron microscopy (SEM), oxygen gas permeability analyzer, and a special computer controlled uniaxial stretching system that provides real-time measurement of true stress, true strain and birefringence. The morphological analysis revealed that PET-co-5SIPA was an effective compatibilizer for both PET/MXD6 and PETI/MXD6 blends. DSC analysis and spectral-birefringence technique were used to understand the thermal and stress-induced crystallization behavior of the blends. Morphological analysis of the films after biaxial stretching indicated that the spherical nylon phase was converted to 75 nm thick disks during stretching (aspect ratio L/W = 6) that creates a tortuous pathway for oxygen ingress. Stretching enhanced the barrier properties of PET/MXD6 and PETI/MXD6 blends.     

The assessment of miscibility and morphology of poly(ε-caprolactone) and poly(para-chlorostyrene) blends

The miscibility and morphology of poly(ε-caprolactone) (PCl) and poly(para-chlorostyrene) (PpClS) blend were investigated by using thermal analysis, morphological analysis, viscometry, and the study of melting point depression. A single glass transition temperature was observed by differential scanning calorimetry (DSC) for PCl/PpClS blends in the whole compositional range (0/100, 25/75, 50/50, 62.5/37.5, 75/25, 90/10). Morphology of the polymers and their blends was studied by scanning electron microscopy (SEM). The Fourier transform infrared spectra of the samples were obtained by spectrometer. Up to 12 cm⁻¹ shifts in carbonyl stretching band of PCl was detected in the spectra of PpClS rich blends. The viscosity of PCl, PpClS and their blends has also been studied to investigate the miscibility according the miscibility criteria Δb, and Δ[η]. Using this data, the interaction parameters α and μ, based on the Chee and Sun et al. approaches were determined. These criteria indicated that the blend is miscible in all proportions up to 90% of PCl content in the blends. The melting point depression of PCl in the blends was examined to obtain the interaction parameter, χ₁₂ for this system. The parameter, χ₁₂ was found to be composition dependent. Negative values of the obtained interaction parameter also support the miscibility of this system up to the 90% PCl in the blend.     

Interpenetrating polymer networks of poly(dimethyl siloxane–urethane) and poly(methyl methacrylate)

Simultaneous IPNs of poly(dimethyl siloxane-urethane) (PDMSU)/poly(methyl methacrylate) (PMMA) and related isomers have been prepared by using new oligomers of bis(β-hydroxyethoxymethyl)poly(dimethyl siloxane)s (PDMS diols) and new crosslinkers biuret triisocyanate (BTI) and tris(β-hydroxylethoxymethyl dimethylsiloxy) phenylsilane (Si-triol). Their phase morphology have been characterized by DSC and SEM. The SEM phase domain size is decreased by increasing crosslink density of the PDMSU network. A single phase IPN of PDMSU/PMMA can be made at an M_c = 1000 and 80 wt % of PDMSU. All of the pseudo- or semi-IPNs and blends of PDMSU and PMMA were phase separated with phase domain sizes ranging from 0.2 to several micrometers. The full IPNs of PDMSU/PMMA have better thermal resistance compared to the blends of linear PDMSU and linear PMMA. © 1993 John Wiley & Sons, Inc.     

Influence of chain extension on the compatibilization and properties of recycled poly(ethylene terephthalate)/linear low density polyethylene blends

Polymeric methylene diphenyl diisocyanate (PMDI) was added as chain extender to a blend of recycled poly(ethylene terephthalate) (R-PET) and linear low density polyethylene (LLDPE) with compatibilizer of maleic anhydride-grafted poly(styrene-ethylene/butadiene-styrene) (SEBS-g-MA). Hydroxyl end groups of PET can react with both isocyanate groups of PMDI and maleic anhydride groups of SEBS-g-MA, which are competing reactions during reactive extrusion. The compatibility and properties of the blends with various contents of PMDI were systemically evaluated and investigated. WAXD results and SEM observations indicated that chain extension inhibits the reaction between PET and SEBS-g-MA. As the PMDI content increased, the morphology of dispersed phase changed from droplet dispersion to rodlike shape and then to an irregular structure. The DSC results showed that the crystallinity of PET decreased in the presence of PMDI, and the glass transition temperature (T_g) of PET increased with addition of 0-0.7 w% PMDI. The impact strength of the blend with 1.1 w% PMDI increased by 120% with respect to the blend without PMDI, accompanied by only an 8% tensile strength decrease. It was demonstrated that the chain extension of PET with PMDI in R-PET/LLDPE/SEBS-g-MA blends not only decreased the compatibilization effect of SEBS-g-MA but also hindered the crystallization of PET.     

Sodium Alginate and Poly(ethylene glycol) Blends: Thermal and Morphological Behaviors

Sodium alginate (SA) was blended with varying amounts of poly(ethylene glycol) (PEG) viz., 10, 20, 30, 40 and 50 wt % by using water as a solvent. The obtained SA/PEG blends have been characterized for thermal behavior by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) and surface morphology by scanning electron microscopic (SEM) methods. DSC analysis indicates the increase in glass transition temperature (T_g) of the blends with an increase in PEG content in the blend, which is due to chain entanglement. TGA results reveal the enhancement of thermal stability of SA/PEG blends in terms of the onset of degradation and percentage of weight loss. SEM photomicrographs shows the two phase morphology. This result indicates the immiscible nature of the SA/PEG blends.     

Phase morphology of iPP/aPS/SEP blends

Supermolecular structure and phase morphology of the ternary isotactic polypropylene/atactic polystyrene/poly(styrene-b-ethylene-co-propylene) (iPP/aPS/SEP) compression molded blends with 100/0, 90/10, 70/30, and 50/50 iPP/aPS weight ratios and with different amounts of added SEP compatibilizer were studied by optical microscopy (OM), scanning electron microscopy (SEM), transmission electron microscopy (TEM), small-angle X-ray scattering (SAXS) and wide-angle X-ray diffraction (WAXD). SEP significantly reduced the size of dispersed aPS particles that enabled better spherulitization in the iPP matrix. Furthermore, iPP spherulites in ternary blends with 90/10 iPP/aPS weight ratio became larger in comparison with the pure iPP. TEM revealed that the SEP formed continuous interface layer around the dispersed aPS particles even when only 2.5 wt.% of SEP was added. Particle size distribution was distinctly bimodal. When the SEP content was increased to 10 wt.%, joining together smaller and bigger aPS and SEP particles formed dispersed aggregates. Additionally, both amorphous components (aPS and SEP) influenced crystallization process of iPP matrix and so modified, to some extent, its final supermolecular structure. SEP compatibilizer did not significantly affect crystallite orientation. The increase of crystallite sizes, which was more affected by the addition of aPS than by the addition of SEP, seemed to be influenced by the solidification effect rather than by the phase morphology of the blends.     

Thermal degradation studies in poly(vinyl chloride)/poly(methyl methacrylate) blends

The miscibility, morphology, and thermal properties of poly(vinyl chloride) (PVC) blends with different concentrations of poly(methyl methacylate) (PMMA) have been studied. The interaction between the phases was studied by FTIR and by measuring the glass transition temperature (T_g) of the blends using differential scanning calorimetry. Distribution of the phases at different compositions was studied through scanning electron microscopy. The FTIR and SEM results show little interaction and gross phase separation. The thermogravimetric studies on these blends were carried out under inert atmosphere from ambient to 800 °C at different heating rates varying from 2.5 to 20 °C/min. The thermal decomposition temperatures of the first and second stage of degradation in PVC in the presence of PMMA were higher than the pure. The stabilization effect on PVC was found most significant with 10 wt% PMMA content in the PVC matrix. These results agree with the isothermal degradation studies using dehydrochlorination and UV-vis spectroscopic results carried out on these blends. Using multiple heating rate kinetics the activation energies of the degradation process in PVC and its blends have been reported.     

Fabrication and magnetic properties of FePt nanoparticle assemblies embedded in MgO-matrix systems

Hydrophilic FePt nanoparticles (NPs) have been embedded into the MgO-matrix systems via a sol–gel process to prevent FePt NPs from aggregating and sintering during the heat-treatment process required for the L1₀ ordering. The chemically ordered L1₀-phase FePt can be obtained after annealing at 700 °C for 60 min in atmosphere containing H₂. The effect of the pH value of MgO collosol and FePt nanocrystal loading amount on the structure, morphology, and magnetic properties of FePt/MgO nanocomposites has been investigated. The neutral pH value of 7 in MgO sol is beneficial to stabilize FePt NPs and obtain higher chemical ordering parameter S for the face-centered tetragonal -FePt/MgO nanocomposites with larger coercivity. The FePt NPs loading amount also plays a key role in tuning the microstructure and magnetic properties of the nanocomposites. The relatively higher FePt NPs loading with FePt/MgO molar ratio (R_FM) of 1:2 leads to relatively perfect hexagonal assembly and pure L1₀ phase. When the R_FM is 1:5 and 1:10, the MgO-matrix in nanocomposites causes the Fe element loss in FePt NPs along with formation of secondary phases such as magnesioferrite or Pt₃Fe during the annealing process. Under optimal processing of neutral pH value of 7 and R_FM of 1:2, the presence of MgO matrix produces more homogeneous microstructures and better magnetic properties with higher room-temperature coercivity (H _C = 4.65 kOe).     

A polymer of bisphenol A and bisphenol A diglycidyl ether and its blends with poly(styrene‐co‐acrylonitrile): In situ polymerization preparation,morphology, and mechanical properties

The poly(hydroxy ether of bisphenol A)‐based blends containing poly(acrylontrile‐co‐styrene) (SAN) were prepared through in situ polymerization, i.e., the melt polymerization between the diglycidy ether of bisphenol A (DGEBA) and bisphenol A in the presence of poly(acrylontrile‐co‐styrene) (SAN). The polymerization reaction started from the initial homogeneous ternary mixture of SAN/DGEBA/bisphenol A, and the phenoxy/SAN blends with SAN content up to 20 wt % were obtained. Both the solubility behavior and Fourier transform infrared (FTIR) spectroscopy studies demonstrate that no intercomponent reaction occurred in the reactive blend system. Differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), and scanning electronic microscopy (SEM) were employed to characterize the phase structure of the as‐polymerized blends. All the blends display the separate glass transition temperatures (T_g's); i.e., the blends were phase‐separated. The morphological observation showed that all the blends exhibited well‐distributed phase‐separated morphology. For the blends with SAN content less than 15 wt %, very fine SAN spherical particles (1–3 μmm in diameter) were uniformly dispersed in a continuous matrix of phenoxy and the fine morphology was formed through phase separation induced by polymerization. Mechanical tests show that the blends containing 5–15 wt % SAN displayed a substantial improvement of tensile properties and Izod impact strength, which were in marked contrast to those of the materials prepared via conventional methods. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 525–532, 1999