Shear Effect on Morphology of Poly(Butylene Terephthalate)/Poly(Styrene‐co‐Acrylonitrile) Blends

Abstract

The shear flow effect on the morphology of poly(butylene terephthalate)(PBT)/poly(styrene‐co‐acrylonitrile)(SAN) was studied by a parallel plate type shear apparatus. In PBT/SAN = 20/80 blend, particle size of dispersed domains was governed by both break‐up and coalescence processes, and it was much affected by shear rate. The minimum particle size was observed at a certain shear rate. This phenomenon can be explained by the shear matching effect of PBT and SAN; that is, the viscosity ratio of PBT to SAN changed with shear rate and the finest morphology was obtained at the appropriate viscosity ratio. Similar behavior was also observed for PBT/SAN = 70/30 (PBT was the matrix), even though the particle size was larger than that of PBT/SAN = 20/80. For PBT/SAN = 10/90 blend, the sample showed a complicated appearance during shearing. A translucent region correlated to the fine morphology was observed more than twice with increasing shear rate. This phenomenon could not be explained by the viscosity matching effect only. It was affected by small changes in the balance of breaking‐up and coalescence effects.     

Preparation and Evaluation of the Morphology,Flammability, and Mechanical Properties of the Acrylonitrile‐Butadiene‐Styrene/Poly (vinyl chloride) Blends

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

Poly(acrylamide‐co‐acrylic acid)/Poly(vinyl pyrrolidone) Polymer Blends Prepared by Dispersion Polymerization

The structure and properties of a three‐component system, a poly(acrylamide‐co‐acrylic acid)/poly(vinyl pyrrolidone) [P(AM‐co‐AA)/PVP] polymer blend prepared by dispersion polymerization, were studied. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images showed that the resulting P(AM‐co‐AA) microspheres with diameters between 200–300 nm were well‐dispersed in the PVP matrix. Fourier transform infrared spectra (FTIR) showed that intermolecular hydrogen bonding interaction occurred between the dispersed phase and the continuous phase. The mechanical properties of P(AM‐co‐AA)/PVP polymer blends were also determined. With different mass ratios of acrylamide to acrylic acid, it was found that the blends had better mechanical properties with increased AA content.     

Effect of Non‐Ideal Mixed Solvents on Dimensions of Poly(N‐Vinylpyrrolidone) and Poly(Methyl Methacrylate) Coils

An addition of a small amount of non‐solvent tetrahydrofuran (THF) to good solvent water gave rise to a strong solvent power for poly(N‐vinylpyrrolidone) (PVP). It was found that PVP coils in mixtures of water and THF first swelled as the fraction of THF was increased, and then the coils contracted after a critical composition of the solvent mixture based on the measurement of dilute solution viscosities. It was reached that the power of the mixed solvents was not the simple average of the power of individual components. The influence of the non‐ideal mixing of water and THF on the power of these mixtures for PVP and the dimensions of PVP coils was taken into account. Especially the formation of pseudo‐clathrate hydrate structure with the composition φ _THF ≈ 0.44 was found to be an important factor to change the solvation and dimensions of PVP coils. Some other solvent mixtures for PVP and poly(methyl methacrylate) (PMMA) were also found to be non‐ideal mixtures. The viscosities of these solvent mixtures could show positive or negative deviation from the values obtained from the addition rule. It was shown again that the influence of the non‐ideality of these solvent mixtures on the dimensions of polymer coils was great. The action of mixed solvents changed the dimension of polymer coils, not only because of excluded volume effects but also because of the different molecular interactions present in these mixed solvents.     

Poly(m‐Phenylene Isophthalamide) Ultrafine Fibers from an Ionic Liquid Solution by Dry‐Jet‐Wet‐Electrospinning

Ultrafine poly(m‐phenylene isophthalamide) (PMIA) fibers from PMIA solution in an ionic liquid via dry‐jet‐wet electrospinning technology are described. The morphology of the fibers with and without treatment in a coagulation water bath in the dry‐jet‐wet‐electrosinning process was observed by scanning electrical microscopy (SEM) and a high resolution optical microscope. The crystal structure of the fibers was analyzed by wide angle X‐ray diffraction (WAXD). The differences of morphologies and properties between the ultrafine fibers obtained by the electrospinning process and fibers from conventional wet‐spinning technology are discussed. The thermal properties of the ultrafine PMIA fibers were characterized by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA).     

Electrochemical Synthesis and Structure of Poly(2‐methyl‐1‐naphthylamine) Films

A novel polymer, poly(2‐methyl‐1‐naphthylamine), which was synthesized electrochemically at various temperatures from a solution containing 2‐methyl‐1‐naphthylamine, acetic acid and sodium acetate, was characterized by IR spectroscopy. The structural conclusions were based on comparisons of polymer spectra with the IR‐spectrum of the monomer, 2‐methyl‐1‐naphthylamine. IR spectroscopy indicates that the electropolymerization proceeds via the –NH₂ groups and that the poly(2‐methyl‐1‐naphthylamine) structure consists of imine (–N?C) and amine (–NH–C) links between naphthalene rings as well as a free methyl groups in the chains. An analysis of the “substitution pattern” region in the polymer's spectra suggests that the polymer molecules were formed via mixed N–C(4), N–C(5) and N–C(7) linkages between repeated units. The ratio of between the 1645 and 1620 cm^? 1 peak areas decreases with increased temperature during synthesis, indicating that 25°C is the best temperature to obtain higher molecular weights.     

Crystal Structures of Tetrakis‐(4‐chlorophenylthio)‐butatriene and Tetrakis‐(tert‐butylthio)‐butatriene

Tetrakis‐(4‐chlorophenylthio)‐butatriene (3a) and tetrakis‐(tert‐butylthio)‐butatriene (3b) were synthesized, and their crystal structures were determined. The compound 3a is monoclinic, space group P2₁/c, a=6.9785(8), b=8.6803(9), c=22.884(2) Å, β=93.887(6)^o, V=1383.0(3) ų, Z=2. The compound 3b is monoclinic, space group P2₁/n, a=11.0615(6), b=10.8507(4), c=11.2717(6) Å, β =116.427(2)^o, V=1211.5(1) ų, Z=4. The title compounds 3a and 3b reside on an inversion center so that only half of the molecule is crystallographically unique. Both compounds are not planar. The crystal structures of 3a and 3b have cumulated double bonds. The C7–C8–C8ⁱ and C5–C6–C6ⁱ angles that show the linearity in both structures, respectively, are 176.4(3)° in 3a and 175.6(2)° in 3b.     

Thermal Behavior of Polyamide‐12 and Poly (Styrene‐Co‐Acrylonitrile) Blend

In this work, an unusual morphology of a mixture of polyamide‐12 (PA‐12) with a series of poly (styrene‐co‐acrylonitrile) (SAN) was obtained by solution casting and fast solvent evaporation. The prepared film was transparent although it contained many crystals. These crystals apparently prevented phase separation despite the instability of the PA‐12 and SAN mixtures below 180°C. In isothermal experiments, once the crystals were melted, phase separation began and the scattered intensity fit the Cahn–Hilliard theory. When the AN content in the SAN copolymer was less than 5%, the phase separation took place when only part of the crystals were melted at 180°C. However, due to the constraint of unmelted crystals, the growth rate of phase separation at this temperature was much slower.     

Nonisothermal Crystallization Nucleation of In‐Situ Fibrillar and Spherical Inclusions in Poly (Phenylene Sulfide)/Isotactic Polypropylene Blends

Nonisothermal crystallization nucleation and its kinetics of in‐situ fibrillar and spherical dispersed phases in poly (phenylene sulfide) (PPS)/isotactic polypropylene (iPP) blends are discussed. The PPS/iPP in‐situ microfibrillar reinforced blend (MRB) was obtained via a slit‐die extrusion, hot stretching, and quenching process, while PPS/iPP common blend with spherical PPS particles was prepared by extrusion without hot stretching. Morphological observation indicated that the well‐defined PPS microfibrils were in situ generated. The diameter of most microfibrils was surprisingly larger than or equal to the spherical particles in the common blend (15/85 PPS/iPP by weight). The nonisothermal crystallization kinetics of three samples (microfibrillar, common blends, and neat iPP) were investigated with differential scanning calorimetry (DSC). The PPS microfibrils and spherical particles could both act as heterogeneous nucleating agents during the nonisothermal crystallization, thus increasing the onset and maximum crystallization temperature of iPP, but the effect of PPS spherical particles was more evident. For the same material, crystallization peaks became wider and shifted to lower temperature when the cooling rate increased. Applying the theories proposed by Ozawa and Jeziorny to analyze the crystallization kinetics of neat iPP, and microfibrillar and common PPS/iPP blends, both of them could agree with the experimental results.     

Polymer–Polymer and Single Polymer Composites Involving Nanofibrillar Poly(vinylidene Fluoride): Manufacturing and Mechanical Properties

Nanofibrillar polymer–polymer composites (NFCs) and single polymer composites (SPCs) were produced using linear low density polyethylene (LLDPE) and poly(vinylidene fluoride) (PVDF). The NFCs were fabricated by means of a microfibrillar composite concept comprising melt blending, cold drawing, and compression molding retaining the highly oriented PVDF reinforcing nanofibrils (diameter of approximately 250 nm) dispersed without any agglomeration in the isotropic LLDPE matrix. The SPC films were prepared by partial surface premelting of neat PVDF nanofibrils (diameter of about 130 nm) using hot compaction at 148°C (about 20°C below the complete melting of PVDF), thus preserving the PVDF nanofibrillar identity. Tensile testing of NFCs based on LLDPE and PVDF showed an increase in the tensile modulus by 135% and in the tensile strength at break by 211%, as compared to those of an isotropic LLDPE film. Furthermore, the PVDF SPCs showed an enhancement of tensile modulus of 30% and strength at break of 305% when compared to those of an isotropic PVDF film.     

Morphology,Crystallization, and Melting of Single Crystals and Thin Films of Star‐branched Polyesters with Poly(ϵ‐caprolactone) Arms as Revealed by Atomic Force Microscopy

The morphology and thermal stability of different sectors in solution‐ and melt‐grown crystals of star‐branched polyesters with poly(?‐caprolactone) (PCL) arms, and of a reference linear PCL, have been studied by tapping‐mode atomic‐force microscopy (AFM). Real‐time monitoring of melt‐crystallization in thin films of star‐branched and linear PCL has been performed using hot‐stage AFM. A striated fold surface was observed in both solution‐ and melt‐grown crystals of both star‐branched and linear PCL. The presence of striations in the melt‐grown crystals proved that this structure was genuine and not due to the collapse of tent‐shaped crystals. The crystals of the star‐branched polymers had smoother fold surfaces, which can be explained by the presence of dendritic cores close to the fold surfaces. The single crystals of linear PCL grown from solution showed earlier melting in the {100} sectors than in the {110} sectors, whereas no such sectorial dependence of the melting was found in the solution‐grown crystals of the star‐branched polymers. The proximity of the dendritic cores to the fold surface yields at least one amorphous PCL repeating unit next to the dendritic core and more nonadjacent and less sharp chain folding than in linear PCL single crystals; this evidently erased the difference in thermal stability between the {110} and {100} sectors. Melt‐crystallization in thin polymer films at 53–55°C showed 4 times faster crystal growth along b than along a, and more irregular crystals with niches on the lateral faces in star‐branched PCL than in linear PCL. Crystal growth rate was strictly constant with time. Multilayer crystals with central screw dislocation (growing with or without reorientation of the b–axis) and twisting were observed in both classes of polymers.     

The Composition,Sequence Analysis,and Crystallization Characterization of Poly(Trimethylene‐co‐Butylene Terephthalate) Copolymer

A series of poly(trimethylene‐co‐butylene terephthalate) (PTBT) copolymers were prepared by direct esterification followed by polycondensation. The composition and sequence distribution of the copolymers were investigated by nuclear magnetic resonance (NMR). The results demonstrate that the synthesized PTBT copolymers are block copolymers and the content of poly(butylene terephthalate) (PBT) units incorporated into the copolymers is always less than that in the polymerization feed. The 1,4‐butanediol consumption by a side reaction leads to a relatively lower content of PBT units in the resultant copolymers. At the same time, the PBT and poly(trimethylene terephthalate) (PTT) sequence length distributions in the copolymers are different. The PBT segments favor a longer sequence length than do the PTT segments in their corresponding enriched copolymers. The crystallization rate of the copolymers becomes lower than the homopolymers, especially for PTT‐enriched copolymers. Compared with the PTT segment, the presence of PBT segments in the copolymers seems to accelerate crystallization. A wide‐angle X‐ray diffraction (WAXD) analysis indicates PTT and PBT units do not co‐crystallize. The reduced melting temperatures of the copolymers may be attributed to a smaller lamellar thickness and lateral size due to short sequence lengths.     

Influences of Branched Side Chains and Cross‐linking Network on the Solid State Structures of Oligo‐ and Poly (p‐phenyleneethynylene)s

To investigate the influences of side chains and cross‐linking network on the packing fashion and the formation of aggregates and excimers of poly(p‐phenyleneethynylene)s (PPEs) chains in the solid state, a series of cross‐linkable unsubstituted oligo (p‐phenyleneethynylene)s (OPEVs) and alkoxy‐substituted PPEs (EO‐PPEVs) with vinyl end‐groups were synthesized and characterized. By a thermal cross‐linking reaction, cross‐linked polymers were obtained. The oligomer chains in the cross‐linked polymers containing no residual vinyls are packed randomly, forming no aggregates or excimers; however, aggregates and excimers exist in the cross‐linked polymers if they contain residual vinyls. The chains of EO‐PPEVs with sterically hindered side chains form aggregates in films. The network, leading to a pronounced increase of the film photoluminescence quantum yields, can depress these aggregates. These EO‐PPEVs are fully processable and can become insoluble in normal organic solvents after thermal curing; therefore, they are favorable candidates as active layers for fabrication of high performance multilayer devices.     

Morphology and Mechanical Performance of Polysulfone Modified by a Glass Fiber Reinforced Liquid‐Crystalline Polymer

Abstract

Hybrid composites based on polysulfone of bisphenol A (PSF) and glass fiber (GF) reinforced copolyester liquid‐crystalline polymer (gLCP) were obtained by injection molding. The viscosity of the 10% and 20% gLCP composites was lower than that of pure PSF. The Young's modulus followed the direct rule of mixtures. This was due to the counteracting effects of the decreasing orientation of the liquid‐crystalline polymer (LCP) in the skin at increasing gLCP contents on the one hand; and either the increasing skin thickness in the PSF‐rich composites or the lower orientation of the core in the PSF‐poor composites on the other. The composites with 10–20% gLCP showed the best mechanical performance, because, besides their enhanced processability, they showed a tensile strength similar to that of PSF and much larger notched impact strength.     

Morphology of Fractured Polymer‐Polymer Interfaces Bonded at Ambient Temperature as Studied by Atomic Force Microscopy

The amorphous polymer surfaces of polystyrene (PS, M _n=200 kg/mol, M _w/M _n=1.05) and poly(methyl methacrylate) (PMMA, M _n=51.9 kg/mol, M _w/M _n≤1.07) were brought into contact at 21°C to form PS‐PS (for 54 days) and PMMA‐PMMA auto‐adhesive joints (for 11 days). After contact at that temperature corresponding to T _g‐bulk ?81°C for PS and to T _g‐bulk–88°C for PMMA, where T _g‐bulk is the calorimetric glass transition temperature of the bulk sample, the bonded interfaces were fractured and their surfaces were analyzed by atomic force microscopy (AFM). The surface roughness, R _q, of the fractured interfaces was larger by a factor of 3–4 than was that of the free PS and PMMA surfaces aged for the same period of time. A similar increase in R _q was found by comparison of the free PS surface aged at T _g‐bulk+15°C for 1 h and of the surface of the PS‐PS interface fractured after healing at T _g‐bulk+15°C for 1 h. These observations, indicative of the deformation of the fractured interfaces, suggest the occurrence of some mass transfer across the interface even below T _g‐bulk ?80°C.     

Thermal Behavior of an Fe(III)‐2,9,16,23‐Tetramidephthalocyanine‐Grafted Poly(N‐Vinylcarbazole)

Abstract

The introduction of 2,9,16,23‐tetramide‐Fe(III)phthalocyanine [Fe(III)taPc] units into phosphorylated poly(N‐vinylcarbazole) yields an amorphous grafted polymer containing free carbazolyl groups, phosphonic acid attached to carbazolyl groups, and grafted Fe(III)taPc units as evidenced by infrared spectroscopy. Several thermal transitions were detected by differential scanning calorimetry (DSC). The thermodegradation of the grafted sample, analyzed by simultaneous thermogravimetry‐differential thermal analysis (TG‐DTA), showed successive endo‐ and exothermal reactions resulting from the development of a cross‐linked structure. To determine kinetic parameters, both isothermal and dynamic experiments were performed at the different steps of the degradation process and theoretical methods were applied.     

Reactive Compatibilization of Poly(trimethylene terephthalate)/Polypropylene Blends by Polypropylene‐graft‐Maleic Anhydride. Part 1. Rheology,Morphology, Melting,and Mechanical Properties

Poly(trimethylene terephthalate)/polypropylene (PTT/PP) blends were prepared by melt blending. The rheology, morphology, melting, and mechanical properties of PTT/PP blends were investigated with and without the addition of polypropylene‐graft‐maleic anhydride (PP‐g‐MAH). The melt viscosity results showed that the fluid behavior of PTT/PP blends exhibited great disparity to that of PTT but similar to that of PP; the dispersed flexible PP phase in the blends served as a “ball bearing effect” under shear stress, which made the fluid resistance markedly reduced; by contrast, the relatively rigid PTT dispersed phase made only a small contribution to the viscosity. With 5 wt.% PP‐g‐MAH addition during melt processing, both the shear viscosity and the non‐Newtonian index of 70/30 PTT/PP blend were increased over that of the corresponding uncompatibilized one, whereas the shear viscosity of the 30/70 PTT/PP melt decreased slightly indicating that a considerable amount of PP‐g‐MAH did not act as compatibilizer but probably served as plasticizer.

With the increasing of the other component, the melting temperature of the PTT phase showed a slight decrease while the melting temperature of the PP phase showed a slight increase. 5 wt.% PP‐g‐MAH addition had little influence on the melting temperatures of the two components. When PP≤20 wt.%, the cold crystallization temperature of the PTT phase (T_cc (PTT‐phase)) showed little change with the composition; however, it shifted to higher temperature when PP≥30 wt.%. The variations of the T_cc (PTT‐phase), with and without PP‐g‐MAH, suggested that, when PTT was a minor component, the excess PP‐g‐MAH which did not act as compatibilizer might serve as a plasticizer that made the PTT's cold crystallization process to be easier. The SEM results indicated that, for the uncompatibilized blends, the interfaces from particles pulling‐out are clear and smooth, while, for compatibilized blends, the reactive products are at the interfaces. The mechanical properties suggested that PP‐g‐MAH did not result in significant improvement of the toughness of the blend, but the tensile strength increased markedly.     

Rheological Properties,Morphology, and Thermal Performance of E‐MA‐GMA/PC Blend

Blends of ethylene–methyl acrylate–glycidyl methacrylate terpolymer (E‐MA‐GMA, a random terpolymer) and polycarbonate (PC) were prepared in a Haake torque rheometer and the rheological properties, phase morphology, and thermal behavior were investigated. The graft reactions of PC terminal hydroxyl groups with the epoxy groups of E‐MA‐GMA and the in situ formation of the E‐MA‐GMA‐g‐PC copolymers at the interface were illustrated by the improved mixing torque and melt viscosity in E‐MA‐GMA/PC blends. Typical variation and significant deformation of the dispersed phase was observed in E‐MA‐GMA/PC blends with different composition, where PC was the matrix. With the E‐MA‐GMA content increasing, a complex co‐continuous phase structure with some dispersed E‐MA‐GMA particles wrapped in the continuous PC phase was present, indicating strengthened interfacial adhesion. When the E‐MA‐GMA content was higher than the PC component, fibrous structure of the dispersed PC phase in the E‐MA‐GMA matrix was caused by shear flow and interfacial interaction. DSC studies showed that the melting point of E‐MA‐GMA shifted to lower temperature with the increase of PC content, indicating that the enhanced interaction and graft structure hindered the process of crystallization and crystal growth.     

Steady–shear‐induced Isothermal Crystallization of Poly(L‐lactide) (PLLA)

The isothermal crystallization of poly(L‐lactide) (PLLA) under steady‐shear flow was investigated in situ using an optical polarizing microscope with a hot shear stage. The steady–shear‐induced crystalline morphology of PLLA, to a great degree, depends on the crystallization temperature. There is a critical temperature, 120°C, below which shear‐induced row nuclei enhance nucleation ability, leading to the improvement of crystallinity, and above which cylindrite structure is generated. Their numbers increase and size reduces with temperature owing to the better movement and relaxation behavior of chains in the presence of shear flow. The results of 2D wide‐angle x‐ray diffraction (WAXD), showing the oriented structure at high T _c , and differential scanning calorimetry (DSC), detecting the rising of T _m with increasing T _c , well confirm the effect of T _c on the crystallization of PLLA under shear flow.     

Synthesis and Characterization of Novel Poly(1‐Naphthylamine)‐Montmorillonite Nanocomposites Intercalated by Emulsion Polymerization

Nanocomposites of montmorillonite (MMT) with poly(1‐naphthylamine) (PNA) is investigated for the first time by emulsion polymerization using three different oxidants. Polymerization of PNA was confirmed by Fourier transformation infrared (FT‐IR) as well as UV‐visible spectra. The in situ intercalative polymerization of PNA within MMT layers was confirmed by FT‐IR, X‐ray diffraction, conductivity; scanning electron microscopy (SEM) as well as transmission electron microscopy studies. X‐ray diffraction revealed intercalated as well as exfoliated structures of PNA/MMT nanocomposites, which were compared with the reported polyaniline‐MMT nanocomposites. It was found that the increase in the concentration of PNA in the interlayer galleries of MMT led to destruction of the layered clay structure resulting in exfoliation of the nanocomposite. Conductivity of the nanocomposites was found to be in the range of 10^?3 to 10^?2 S cm^?1 which was found to be higher than the ones reported for polyaniline‐clay nanocomposites as well as PEOA‐OMMT nanocomposites at similar concentrations of intercalated species. The morphology of PNA/MMT nanocomposites was found to be governed by the nature of the oxidant used.