The crystal structure and drawing induced polymorphism in poly(aryl ether ketone)s .3. Crystallization during hot-drawing of poly(ether ether ketone ketone)

The evolution of crystallinity and polymorphism during hot-drawing of amorphous poly(ether ether ketone ketone) (PEEKK) as a function of strain rate, draw ratio, and temperature was investigated. In modification I, the competition of chain extension and molecular alignment is responsible for the strain rate and temperature dependence. Modification II crystallization is basically controlled by chain extension during stretching. The former can be transformed into the latter via relaxation during stretching or annealing at elevated temperature.

The study of banded spherulite patterns by coupled logistic map lattice model

Banded spherulite patterns are simulated in two dimensions by means of a coupled logistic map lattice model. Both target pattern and spiral pattern which have been proved to be existent experimentally in banded spherulite are obtained by choosing suitable parameters in the model. The simulation results also indicate that the band spacing is decreased with the increase of parameter mu in the logistic map and increased with the increase of the coupling parameter epsilon, which is quite similar to the results in some experiments. Moreover, the relationship between the parameters and the corresponding patterns is obtained, and the target patterns and spiral patterns are distinguished for a given group of initial values, which may guide the study of banded spherulite.

Preparation of a blocked isocyanate compound and its grafting onto styrene-b-(ethylene-co-1-butene)-b-styrene triblock copolymer

The epsilon-caprolactam was used to block the isocyanate group to enhance the storage stability of allyl (3-isocyanate-4-tolyl) carbamate. The spectra of FTIR and NMR showed that blocked allyl (3-isocyanate-4-tolyl) carbamate (BTAI) possesses two chemical functions, an 1-olefin double bond and a blocked isocyanate group. The FTIR spectrum showed BTAI could regenerate isocyanate group at elevated temperature. DSC and TG/DTA indicated the minimal dissociation temperature was about 135 degrees C and the maximal dissociation rate appeared at 226 degrees C. Then the styrene-b-(ethylene-co-1-butene)-b-styrene triblock copolymer (SEBS) was functionalized by BTAI via melt free radical grafting. The effect of temperature, monomer and initiator concentrations on the grafting degree and grafting efficiency was evaluated. The highest grafting degree was obtained at 200 degrees C. The grafting degree and grafting efficiency increased with the enhanced concentration of BTAI or initiator.

Miscibility, crystallization and mechanical properties of PPC/PBS blends

In this paper, melt blends of poly(propylene carbonate) (PPC) with poly(butylene succinate) (PBS) were characterized by dynamic mechanical analysis (DMA), differential scanning calorimetry (DSC), tensile testing, wide-angle X-ray diffraction (WAXD), polarized optical microscopy and thermogravimetric analysis (TGA). The results indicated that the glass transition temperature of PPC in the 90/10 PPC/PBS blend was decreased by about 11 K comparing with that of pure PPC. The presence of 10% PBS was partially miscible with PPC. The 90/10 PPC/PBS blend had better impact and tensile strength than those of the other PPC/PBS blends. The glass transition temperature of PPC in the 80/20, 70/30, and 60/40 PPC/PBS blends was improved by about 4.9 K, 4.2 K, and 13 K comparing with that of pure PPC, respectively; which indicated the immiscibility between PPC and PBS. The DSC results indicated that the crystallization of PBS became more difficult when the PPC content increased. The matrix of PPC hindered the crystallization process of PBS. While the content of PBS was above 20%, significant crystallization-induced phase separation was observed by polarized optical microscopy. It was found from the WAXD analysis that the crystal structure of PBS did not change, and the degree of crystallinity increased with increasing PBS content in the PPC/PBS blends.

Thermal and dynamic mechanical properties of PES/PPS blends

Blends of poly(ether-sulfone) (PES) and poly(phenylene sulfide) (PPS) with various compositions were prepared using an internal mixer at 290degreesC and 50 rpm for 10 min. The thermal and dynamic mechanical properties of PES/PPS blends have been investigated by means of DSC and DMA. The blends showed two glass transition temperatures corresponding to PPS-rich and PES-rich phases. Both of them decreased obviously for the blends with PES matrix. On the other hand, T-g of PPS and PES phase decreased a little when PPS is the continuous phase. In the blends quenched from molten state the cold crystallization temperature of PPS was detected in the blends of PES/PPS with mass ratio 50/50 and 60/40. The melting point, crystallization temperature and the crystallinity of blended PPS were nearly unaffected when the mass ratio of PES was less than 60%, however, when the amount of PES is over 60% in the blends, the crystallization of PPS chains was hindered. The thermal and the dynamic mechanical properties of the PPS/PES blends were mainly controlled by the continued phase.

Melting behaviors, isothermal and non-isothermal crystallization kinetics of nylon 1212

Isothermal crystallization, subsequent melting behavior and non-isothermal crystallization of nylon 1212 samples have been investigated in the temperature range of 160-171 degreesC using a differential scanning calorimeter (DSC). Subsequent DSC scans of isothermally crystallized samples exhibited three melting endotherms. The commonly used Avrami equation and that modified by Jeziorny were used, respectively, to fit the primary stage of isothermal and non-isothermal crystallizations of nylon 1212. The Avrami exponent n was evaluated, and was found to be in the range of 1.56-2.03 for isothermal crystallization, and of 2.38-3.05 for non-isothermal crystallization. The activation energies (DeltaE) were determined to be 284.5 KJ/mol and 102.63 KJ/mol, respectively, for the isothermal and non-isothermal crystallization processes by the Arrhenius' and the Kissinger's methods.

Branched crystal morphology of linear polyethylene crystallized in a two-dimensional diffusion-controlled growth field

The branched crystal morphology of linear polyethylene formed at various temperatures from thin films has been studied by atomic-force microscopy (AFM), transmission electron microscopy (TEM), electron diffraction (ED) pattern and polymer decoration technique. Two types of branched patterns, i.e. dendrite and seaweed patterns, have been visualized. The fractal dimension d(f) = 1.65 of both dendrite and some of seaweed patterns was obtained by using the box-counting method, although most of the seaweed patterns are compact. Selected-area ED patterns indicate that the fold stems tilt about 34.5degrees around the b-axis and polymer decoration patterns show that the chain folding direction and regularity in two (200). regions are quite different from each other. Because of chain tilting, branched crystals show three striking features: 1) the lamella-like branches show two (200) regions with different thickness; 2) the crystals usually bend towards the thin region; 3) the thick region grows faster by developing branches, thus branches usually occur outside the thick region. The branched patterns show a characteristic width w, which gives a linear relationship with the crystallization temperature on a semilogarithmic plot.

Isothermal and nonisothermal crystallization kinetics of nylon-46

Isothermal and nonisothermal crystallization kinetics of nylon-46 were investigated with differential scanning calorimetry. The equilibrium melting enthalpy and the equilibrium melting temperature of nylon-46 were determined to be 155.58 J/g and 307.10 degreesC, respectively. The isothermal crystallization process was described by the Avrami equation. The lateral surface free energy and the end surface free energy of nylon-46 were calculated to be 8.28 and 138.54 erg/cm(2), respectively. The work of chain folding was determined to be 7.12 kcal/mol. The activation energies were determined to be 568.25 and 337.80 kJ/mol for isothermal and nonisothermal crystallization, respectively. A convenient method was applied to describe the nonisothermal crystallization kinetics of nylon-46 by a combination of the Avrami and Ozawa equations.

Morphology and thermal and mechanical properties of PBT/HIPS and PBT/HIPS-g-GMA blends

The modification of high-impact polystyrene (HIPS) was accomplished by melt-grafting glycidyl methacrylate (GMA) on its molecular chains. Fourier transform infrared spectroscopy and electron spectroscopy for chemical analysis were used to characterize the formation of HIPS-g-GMA copolymers. The content of GMA in HIPS-g-GMA copolymer was determined by using the titration method. The effect of the concentrations of GMA and dicumyl peroxide on the degree of grafting was studied. A total of 1.9% of GMA can be grafted on HIPS. HIPS-g-GNU was used to prepare binary blends with poly(buthylene terephthalate) (PBT), and the evidence of reactions between the grafting copolymer and PBT in the blends was confirmed by scanning electron microscopy (SEM), dynamic mechanical analysis, and its mechanical properties. The SEM result showed that the domain size in PBT/HIPS-g-GMA blends was reduced significantly compared with that in PBT/HIPS blends; moreover, the improved strength was measured in PBT/HIPS-g-GMA blends and results from good interfacial adhesion. The reaction between ester groups of PBT and epoxy groups of HIPS-g-GMA can depress crystallinity and the crystal perfection of PBT.

Morphology of conductive blend fibers of polyaniline and polyamide-11

Polyaniline (PANI), a member of the intrinsically conducting polymer (ICPs) family, was blended with polyamide-11 (polyco-aminoundecanoyle) in concentrated sulfuric acid. The above solution was used to spin conductive PANI/polyamide-11 fibers by wet-spinning technology. Scanning electron microscope (SEM) and transmission electron microscope (TEM) were employed to study the two-phase morphology of the conductive PANI/polyamide-11 fibers. The micrographs of the cross-section, the axial section and the surface of the monofilament demonstrated that the two blend components were incompatible. The morphology of PANI in the fibers was of fibrillar form, which was valuable for producing conducting channels. The electrical conductivity of the fibers was from 10(-6) to 10(-1) S/cm with the different PANI fraction and the percolation threshold was about 5 wt.%. By comparing the two blend systems of PANI/Polyamide-11 fibers and carbon black filled poly(ethylene terephthalate) (PET) fibers, it was shown that the morphology of the conductive component had an influence on electrical conductivity, The former had higher conductivity and lower percolation threshold than the latter. (C) 2001 Elsevier Science B.V. All rights reserved.

Melting crystallization behavior of nylon 66

Analysis of isothermal and nonisothermal crystallization kinetics of nylon 66 was carried out using differential scanning calorimetry (DSC). The commonly used Avrami equation and that modified by Jeziorny were used, respectively, to fit the primary stage of isothermal and nonisothermal crystallizations of nylon 66. In the isothermal crystallization process, mechanisms of spherulitic nucleation and growth were discussed. The lateral and folding surface free energies determined from the Lauritzen-Hoffman treatment are sigma = 9.77 erg/cm(2) and sigma (e) = 155.48 erg/cm(2), respectively; and the work of chain folding is q = 33.14 kJ/mol. The nonisothermal crystallization kinetics of nylon 66 was analyzed by using the Mo method combined with the Avrami and Ozawa equations. The average Avrami exponent (n) over bar was determined to be 3.45. The activation energies (DeltaE) were determined to be -485.45 kJ/mol and -331.27 kJ/mol, respectively, for the isothermal and nonisothermal crystallization processes by the Arrhenius and the Kissinger methods.

Isothermal and nonisothermal crystallization kinetics of nylon-11

Analysis of the isothermal, and nonisothermal crystallization kinetics of Nylon-11 is carried out using differential scanning calorimetry. The Avrami equation and that modified by Jeziorny can describe the primary stage of isothermal and nonisothermal crystallization of Nylon-11. In the isothermal crystallization process, the mechanism of spherulitic nucleation and growth are discussed; the lateral and folding surface free energies determined from the Lauritzen-Hoffman equation are sigma = 10.68 erg/cm(2) and sigma(e) = 110.62 erg/cm(2); and the work of chain folding q = 7.61 Kcal/mol. In the nonisothermal crystallization process, Ozawa analysis failed to describe the crystallization behavior of Nylon-ii. Combining the Avrami and Ozawa equations, we obtain a new and convenient method to analyze the nonisothermal crystallization kinetics of Nylon-11; in the meantime, the activation energies are determined to be -394.56 and 328.37 KJ/mol in isothermal and nonisothermal crystallization process from the Arrhonius form and the Kissinger method. (C) 1998 John Wiley & Sons, Inc.

IN-SITU COMPOSITE - PHENOLPHTHALEIN POLYETHERSULFONE-THERMOTROPIC LIQUID-CRYSTALLINE POLYMER BLENDS

Phase behavior, thermal, theological and mechanical properties plus morphology have been studied for a binary polymer blend. The blend is phenolphthalein polyethersulfone (PES-C) with a thermotropic liquid crystalline polymer (LCP), a condensation copolymer of p-hydroxybenzoic acid with ethylene terephthalate (PHB-PET). It was found that these two polymers form optically isotropic and homogeneous blends by means of a solvent casting method. The homogeneous blends undergo phase separation during heat treatment. However, melt mixed PES-C/PHB-PET blends were heterogeneous based upon DSC and DMA analysis and SEM examination. Addition of LCP in PES-C resulted in a marked reduction of melt viscosity and thus improved processability. Compared to pure PES-C, the charpy impact strength of the blend containing 2.5% LCP increased 2.5 times. Synergistic effects were also observed for the mechanical properties of blends containing < 10% LCP. Particulates, ribbons, and fibrils were found to be the typical morphological units of PHB-PET in the PES-C matrix, which depended upon the concentration of LCP and the processing conditions.