PANI-DBSA/PAN共混体系的相容性及导电性能

以三氯甲烷/二甲基亚砜为混合溶剂,采用溶液共混的方法制备PANI-DBSA/PAN导电薄膜.采用扫描电镜、差示扫描量热仪、红外光谱及广角X射线衍射分析研究了共混体系的相容性及相态结构.结果表明,PANI-DBSA在PAN基体中分布均匀,聚集尺寸为纳米级,其较均匀的分布及较小的聚集尺寸使其出现较低的逾渗阈值(低于4%);PANI-DBSA/PAN的共混体系只有一个玻璃化转变温度,居于纯PAN和PANI-DBSA之间,表明两者之间具有良好的相容性;FTIR分析证实PANI-DBSA与PAN之间存在氢键相互作用,氢键发生在PANI-DBSA的氨基与PAN共聚物中的羰基之间,这两种聚合物之间的氢键相互作用是导致PANI-DBSA与PAN之间良好相容性的内因.     

Miscibility and hydrolytic degradation in alkaline solution of poly(l-lactide) and poly(p-vinyl phenol) blends

Poly(l-lactide) (PLLA) was melt-blended with poly(p-vinyl phenol) (PVPh) using a two-roll mill, and the miscibility between PLLA and PVPh and degradation of the blend films were investigated. It was found that PLLA/PVPh blend has miscibility in the amorphous state because only single T_g was observed in the DSC and DMA measurements. The T_g of the PLLA/PVPh blend could be controlled in the temperature range from 55 °C to 117 °C by changing the PVPh weight fraction. In alkaline solution, degradation rate of PLLA/PVPh blends was faster than that of neat PLLA because PVPh could dissolve in alkaline solution. The surface morphology of degraded PLLA and PLLA/PVPh blend were observed by SEM. The surface morphology of degraded PLLA/PVPh blend was finer than that of PLLA. Young's modulus of PLLA/PVPh blend increased with increasing PVPh content. Yield stress of PLLA/PVPh blends whose PVPh content was less than 30 wt% kept the level of about 55 MPa and that of PLLA/PVPh blend whose PVPh content was 40 wt% is much lower than that of neat PLLA.     

Linear unsaturated polyester + poly(?-caprolactone) blends: Calorimetric behaviour and morphology

Blends of a linear unsaturated polyester (LUP, commercially named Al100) with poly(?-caprolactone) (PCL) of different molecular weights have been studied. The miscibility and crystallinity have been analyzed through FT-IR spectroscopy, differential scanning calorimetry (DSC) and environmental scanning electronic microscopy (ESEM). All the blends were subjected to the same heat treatment consisting of crystallizing during 45 min at constant temperature (10, 20, 30 or 40 °C). The glass transition temperature, T_g, and fusion temperature, T_fus, have been determined in the whole composition range for each blend. The T_g-composition dependence and the high degree of crystallinity detected at intermediate blend compositions denote an anomalous behaviour that could indicate the lack of homogeneity (phase separation) in the different blends studied. The ESEM measurements confirm the lack of homogeneity of the amorphous region in blends with high content of LUP. The results have been discussed as a function of the crystallization temperature and the molecular weight of PCL.     

Energetic potential and kinetic behavior of peats

The miscibility of blends of isotactic polypropylene and propylene-1-hexene (PH) copolymers with 11 and 21 mol% of 1-hexene (PH11 and PH21, respectively) has been studied theoretically and using DSC, DMA, and AFM techniques. Using experimental PVT data, the solubility parameter approach leads to a critical difference in 1-hexene content for melt miscibility of 17 mass% (~11 mol%) at 200 °C and 0.1 MPa. The theoretical window for miscibility is in close agreement with thermal properties of the blends. The glass transition (T _g) of miscible blends (iPP/PH11 and PH11/PH21) decreases proportionally to the content of PH having the lowest T _g, while immiscible blends (iPP/PH21) display invariable T _g with blend composition. The same trend was extracted from the analysis of the β-relaxation by dynamic mechanical analysis. Room temperature AFM images of blends quenched from 200 °C into liquid nitrogen confirm phase segregation of iPP/PH21 in domains of 1–5 microns, while the AFM images of iPP/PH11 and PH11/PH21 lack any obvious signature of phase separation prior to crystallization.     

Development of novel elastomeric blends derived from chlorinated nitrile rubber and chlorinated ethylene propylene diene rubber

Chlorinated nitrile rubber (Cl-NBR) has been blended with chlorinated ethylene propylene diene rubber (Cl-EPDM) in different ratios by a conventional mill mixing method. The effect of the blend ratio on processing characteristics, mechanical properties (such as tensile and tear strength, elongation at break, hardness, abrasion resistance, heat build-up and resilience), structure, morphology, glass transition temperature (Tg), thermal stability, flame retardancy, oil resistance, AC conductivity, dielectric properties and transport behavior of petrol, diesel and kerosene were investigated. The shift in absorption bands of blends studied from FTIR spectra, single Tg from DSC analysis and decrease in amorphous nature from XRD showed the molecular miscibility in Cl-NBR/Cl-EPDM blends. SEM images showed the uniform mixing of both Cl-NBR and Cl-EPDM in a 50/50 blend ratio. The TGA curves indicated the better thermal stability of the polymer blend. The elongation at break, heat build-up, resilience and hardness of the polymer blend decreases with an increase in Cl-NBR content in the blend whereas the flame and oil resistance were increased with increase in Cl-NBR content. Among the polymer blends, the maximum torque, tensile strength, tear and abrasion resistance was obtained for the 50/50 blend ratio because of the effective interfacial interactions between the blend components. AC conductivity and dielectric properties of polymer blend increased with increase in the ratio of Cl-NBR in the blend. Different transport properties such as diffusion, permeation and sorption coefficient were measured with respect to nature of solvent and different blend ratios. Temperature dependence of diffusion was used to estimate the activation parameters and the mechanism of transport found to be anomalous.     

Thermal analysis on influence of compatibilizing agents

Studies have been made on differential scanning calorimetry (DSC), thermogravimetric analysis (TG) and dynamic mechanical analysis (DMA) of binary blends of isobutylene-isoprene (IIR) copolymer and polychloroprene (CR) elastomers. Blends of IIR and CR are incompatible and showed separateT _g peaks in DSC curves similar to Tanδ peaks. However, addition of chlorinated polyethylene (CM) elastomer, as compatibilizer, imparts miscibility between IIR and CR which could be judged both through DSC as well as by dynamic loss measurements (Loss modulusE″ and Tanδ). The storage modulus (E′) showed variation of stiffness due to structural changes associated with the addition of compatibilizer. TG plots for these blends showed improvement of thermal stability both by addition of a suitable compatibilizer as well as due to formation of crosslinked structures associated with the vulcanization of the blends by standard curative package.     

Miscibility and compatibilization of poly(trimethylene terephthalate)/acrylonitrile-butadiene-styrene blends

Poly(trimethylene terephthalate)/acrylonitrile-butadiene-styrene (PTT/ABS) blends were prepared by melt processing with and without epoxy or styrene-butadiene-maleic anhydride copolymer (SBM) as a reactive compatibilizer. The miscibility and compatibilization of the PTT/ABS blends were investigated by differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), capillary rheometer and scanning electron microscopy (SEM). The existence of two separate composition-dependent glass transition temperatures (T_gs) indicates that PTT is partially miscible with ABS over the entire composition range. In the presence of the compatibilizer, both the cold crystallization and glass transition temperatures of the PTT phase shifted to higher temperatures, indicating their compatibilization effects on the blends.The PTT/ABS blends exhibited typical pseudoplastic flow behavior. The rheological behavior of the epoxy compatibilized PTT/ABS blends showed an epoxy content-dependence. In contrast, when the SBM content was increased from 1 wt% to 5 wt%, the shear viscosities of the PTT/ABS blends increased and exhibited much clearer shear thinning behavior at higher shear rates. The SEM micrographs of the epoxy or SBM compatibilized PTT/ABS blends showed a finer morphology and better adhesion between the phases.     

Thermal,mechanical and electroactive shape memory properties of polyurethane (PU)/poly (lactic acid) (PLA)/CNT nanocomposites

Polymer blend nanocomposites based on thermoplastic polyurethane (PU) elastomer, polylactide (PLA) and surface modified carbon nanotubes were prepared via simple melt mixing process and investigated for its mechanical, dynamic mechanical and electroactive shape memory properties. Chemical and structural characterization of the polymer blend nanocomposites were investigated by Fourier Transform infrared (FT-IR) and wide angle X-ray diffraction (WAXD). Loading of the surface modified carbon nanotube in the PU/PLA polymer blends resulted in the significant improvement on the mechanical properties such as tensile strength, when compared to the pure and pristine CNT loaded polymer blends. Dynamic mechanical analysis showed that the glass transition temperature (T_g) of the PU/PLA blend slightly increases on loading of pristine CNT and this effect is more pronounced on loading surface modified CNTs. Thermal and electrical properties of the polymer blend composites increases significantly on loading pristine or surface modified CNTs. Finally, shape memory studies of the PU/PLA/modified CNT composites exhibit a remarkable recoverability of its shape at lower applied dc voltages, when compared to pure or pristine CNT loaded system.     

Miscibility and thermal stability of poly(vinyl alcohol)/chitosan mixtures

The miscibility and the thermal behaviour of chitosan acetate (ChA) with poly(vinyl alcohol) (PVA) have been investigated by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and dynamic mechanical analysis (DMA). Chitosan is blended with poly(vinyl alcohol) in acetic acid solution and this solution is cast to prepare the blend film. From thermal curves the thermal transitions: T_g, T_m and characteristic temperatures of decomposition: T_di, T_max have been determined and compared. The influence of the degree of PVA hydrolysis on the thermal properties of blend systems has been discussed.Based upon the observation on the DSC analysis, the melting point of PVA is decreased when the amount of ChA in the blend film is increased. Though some broadening of the transition curves could be noticed (DSC, TGA and DMA), the obtained results suggest that in the solid ChA/PVA blends the components are poorly miscible. Only PVA sample with relatively low DH = 88% and hence low degree of crystallinity shows partial miscibility with ChA of relatively low molecular weight.     

Crystallization of poly(N-methyldodecano-12-lactam) in blends with poly(styrene-stat-acrylic acid)

Crystallization behaviour of blends of poly(N-methyldodecano-12-lactam) (PMDL) with statistical copolymer poly(styrene-stat-acrylic acid) (PSAA) has been studied by the DSC and WAXD methods. The blend films prepared from dioxane solutions were crystallized at laboratory temperature for five days. Approximate crystallinities of as-prepared neat lower- PMDL 5 and higher-molecular weight PMDL 45 were 28% and 19%, respectively. With increasing PSAA content in the blends the crystallinities decreased sharply. The melting point of the primary crystalline structure of PMDL showed a decreasing dependence on PSAA content in the blends, confirming miscibility of the PMDL-PSAA pair. Recrystallization was strongly suppressed in the blends. The lower-melting endotherm appearing at about 10-15 °C above the crystallization temperature was attributed to melting to less perfect structures formed during secondary crystallization. In neat PMDL, the extent of secondary crystallization was approximately 5-10%. In the blends containing 20% PSAA approximate relative proportion of secondary crystallites on total crystallinity was 40% and 60% for the blends with PMDL 5 and PMDL 45, respectively. WAXD measurements did not reveal any change in crystal modification on blending. Increased T_g in blends of flexible PMDL cannot play a significant role in suppression of primary in favour of secondary crystallization. This was attributed to low mobility of PMDL chains due to dilution effect and specific interactions with the amorphous copolymer component, and, in case of the higher-molecular-weight PMDL, a greater involvement of entanglements. Higher T_g of blends was involved in retardation of non-isothermal crystallization on cooling and subsequent cold crystallization.     

Synthesis of a random copolymer and its compatibility for thermotropic liquid crystalline polymer/poly(ether ether ketone) blends

A random copolymer (RCP) containing poly(ether ether ketone) (PEEK) and thermotropic liquid crystalline polymer (TLCP) segments was synthesized. Its chemical structure and liquid crystalline properties were characterized by FT‐IR, differential scanning calorimetry (DSC) and polar light microscopy (PLM) respectively. A single glass transition temperature (T_g) at 134.0°C, a melting temperature (T_m) at 282.0°C and a temperature of ignition (T_i) at 331.3°C can be observed. Blends of PEEK and TLCP with and without RCP as compatibilizer were prepared by extrusion and the effect of RCP on the thermal properties, dynamic mechanical properties, morphology and static tensile mechanical properties of blends was investigated by means of DSC, dynamic mechanical analysis (DMA), scanning electron microscopy (SEM), etc. Dynamic mechanical measurements indicated that there appeared to be only a single tan δ peak resulting from the glass transition of the PEEK‐rich phase and the T_g value shifted towards higher temperature due to the presence of compatibilizer, as suggested partial compatibility. Morphological investigations showed that the addition of RCP to binary blends reduced the dispersed phase size and improved the interfacial adhesion between the two phases. The ternary compatibilized blends showed enhanced tensile modulus compared to their binary blends without RCP. The strain at break decreased for the ternary blends due to embrittlement of the matrix by the incorporation of some RCP to the matrix phase. Copyright © 2007 John Wiley & Sons, Ltd.     

Thermal properties of single walled carbon nanotubes composites of polyamide 6/poly(methyl methacrylate) blend system

The nanocomposites of polyamide 6 (PA6)/poly(methyl methacrylate) (PMMA)/non-functionalized and functionalized [carboxylic acid (COOH) and hydroxyl (OH)] single wall carbon nanotubes (SWCNTs) were prepared in mass ratios of 79.5/19.5/1, 49.5/49.5/1, and 19.5/79.5/1 by melt–mixing method at 230 °C. The PA6/PMMA blends with mass ratios of 80/20, 50/50, and 20/80 served as references. The Fourier transform infrared analyses of nanocomposites showed the formation of hydrogen bond interactions among PA6, PMMA, and OH and COOH functional groups of SWCNTs. The nanocomposites and blends had higher thermal stability with respect to the PMMA. The differential scanning calorimeter (DSC) curves showed that the nanocomposites and blends exhibited two T _g values at around 51 and 126 °C for PA6 and PMMA, respectively. About 20 °C early crystallization was observed in nanocomposites compared to the blends. The dynamic mechanical analysis (DMA) results suggested that among all the compositions of blends and nanocomposites, storage modulus (E′) was higher for PMMA-rich blends and nanocomposites. At 25 °C, the E′ values were higher for blends and nanocomposites compared to the neat PA6. The tan δ curves indicated that the more heterogeneity of the hybrid nature resulted in PA6/PMMA/SWCNTs-OH or SWCNTs-COOH with 79.5/19.5/1 mass ratio nanocomposites compared to the PA6/PMMA with 80/20 mass ratio blend. The higher T _g values of PA6 and PMMA were observed in DMA studies compared to the DSC studies for PA6 and PMMA as neat and in blends and nanocomposites. The significant improvements in crystallization of nanocomposites were considered resulting from achieving better compatibility among the polymer components and carbon nanotubes.     

Glass transition study of blends of poly(N-methyldodecano-12-lactam) with poly(styrene-co-acrylic acid)

The blends of poly(N-methyldodecano-12-lactam) (MPA) with poly(styrene-co-acrylic acid) (PSAA) prepared from dioxane solutions were studied by differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FTIR). The experimental DSC data of glass transition temperature T_g as a function of composition of amorphous phase were fitted for the as-prepared and re-scanned samples using theoretical approaches. The as-prepared blends show monotonic single-T_g dependence. The values of the Gordon-Taylor coefficient not far from unity suggest miscibility of the blend system in amorphous phase in the whole concentration range. As documented by FTIR, this miscibility is associated with hydrogen bonds between COOH groups of the acrylic acid units in PSAA molecules acting as the H-bond donor and CO groups of MPA acting as the H-bond acceptor. The T_g-dependencies obtained form the second runs have a profound sigmoid character. The Schneider treatment induced an idea of partial limited miscibility in the MPA/PSAA blends caused by prevalence of homogeneous contacts. The difference in T_g between the first and second run can partly be attributed to higher crystallinities in the former.     

Studies on phase morphology and thermo-physical properties of nitrile rubber blends

The study deals with the morphological and thermal analysis of binary rubber blends of acrylonitrile-co-butadiene rubber (NBR) with another polymer. Either ethylene propylene diene terpolymer (EPDM), ethylene vinyl acetate (EVA), chlorosulphonated polyethylene (CSM), or polyvinyl chloride (PVC) has been selected for the second phase. Depending on the relative polarity and interaction parameter of the components, the binary blends showed development of a bi-phasic morphology through scanning electron microscopy (SEM). Use of different types of thermal analysis techniques revealed that these blends are generally incompatible excepting one of NBR and PVC. Derivative differential scanning calorimetry (DDSC), in place of conventional DSC, has been used to characterize the compatibility behavior of the blends. NBR–PVC shows appearance of only one glass transition temperature (T _g) averaging the individual T _g’s of the blend components. The partially missible blend of NBR and CSM shows a broadening of T _g interval between the phase components, while the immiscible blends of either NBR–EPDM or NBR–EVA do not show any change in T _g values corresponding to the individual rubbers of their blend. The experimental T _g values were also compared with those calculated theoretically by Fox equation and observed to match closely with each other. Studies have also been made to evaluate the thermal stability of these blends by thermo-gravimetric analysis (TG) and evaluation of activation energy of respective decomposition processes by Flynn and Wall method. Thermo-mechanical analysis (TMA) was found to be effective for comparison of creep recovery and dimensional stability of the blends both at sub-ambient as well as at elevated temperatures.     

STUDIES ON MISCIBILITY AND MORPHOLOGICAL FEATURES OF BLENDS OF LC COPOLYESTER AND PET

The morphology of a special blend system composed of liquid crystalline aromatic random copolyester (LCP) and semiflexible polyester PET over the whole composition range has been studied by means of polarized microscope, density measurement, DSC, FTIR and SEM. Based on the microscopic observation, it is found that under suitable mechanical mixing condition, LCP may be rather homogeneously dispersed in the PET matrix, with the middle composition range of the contents of LCP at 30--70 wt % the anisotropic and isotropic phase segregation appears, while with LCP contents over 80 wt% the blends exhibit wholly anisotropie. The DSC thermographs of the melt-pressed and quenched films show single T_(?), T_(cc) and T_m. T_(?) increases with increasing content of LCP and ap, proaches to the T_(?) of pure LCP. The experimental results indicate that the two components of this blend system are miscible, there exist some specific interactions between them.     

PMMA/PC Blends: Effect of Mixing Conditions on Compatibility

In this work the effect of melt mixing condition and of a trans-esterification catalyst on miscibility of poly(methyl methacrylate) (PMMA)/polycarbonate of bisphenol A (PC) blends is studied. In particular, at high temperature chemical reactions between PMMA and PC phases can take place; these strongly change the compatibility in the blend and materials having single T_g can be obtained. FT-IR analyses, coupled with solvent extraction, suggest that a grafting reaction of PC on PMMA is involved. SEC and DSC data are consistent with spectroscopic results, and some decrement of the molar weight distribution (MWD) of PC phase is observed. On the other hand, the presence of a fraction of modified material having higher MWD of starting PMMA is also noticed. The single T_g characteristic of some materials has been confirmed by experimental data of structural relaxation performed by differential scanning calorimetry (DSC). These materials showed optical clarity and the morphological analysis performed by scanning electron microscopy (SEM) confirm the homogeneity of these materials.     

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.     

A study of the blending of ethylene–styrene copolymers differing in the copolymer styrene content: Miscibility considerations

Blends of two or more ethylene–styrene (ES) copolymers that differed primarily in the comonomer composition of the copolymers were studied. Available thermodynamic models for copolymer–copolymer blends were utilized to determine the criteria for miscibility between two ES copolymers differing in styrene content and also between ES copolymers and the respective homopolymers, polystyrene and linear polyethylene. Model estimations were compared with experimental observations based primarily on melt‐blended ES/ES systems, particularly via the analysis of the glass‐transition (T_g ) behavior from differential scanning calorimetry (DSC) and solid‐state dynamic mechanical spectroscopy. The critical comonomer difference in the styrene content at which phase separation occurred was estimated to be about 10 wt % for ES copolymers with a molecular weight of about 10⁵ and was in general agreement with the experimental observations. The range of ES copolymers that could be produced by the variation of the comonomer content allowed the study of blends with amorphous and semicrystalline components. Crystallinity differences for the blends, as determined by DSC, appeared to be related to the overlapping of the T_g of the amorphous component with the melting range of the semicrystalline component and/or the reduction in the mobility of the amorphous phase due to the presence of the higher T_g of the amorphous blend component. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 2976–2987, 2000     

Mechanical properties and morphology of epoxy/poly(vinyl acetate)/poly(4-vinyl phenol) brominated system

Diglycidyl ether of bisfenol-A (DGEBA)/poly(vinyl acetate) (PVAc)/poly(4-vinyl phenol) brominated (PVPhBr) ternary blends cured with 4,4’-diaminodiphenylmethane (DDM) were investigated by differential scanning calorimetry (DSC), dynamic mechanical thermal analysis (DMTA) and scanning electron microscopy (SEM). Homogeneous (DGEBA+DDM)/PVPhBr networks with a unique T _g are generated. Ternary blends (DGEBA+DDM)/PVAc/PVPhBr are initially miscible and phase separate upon curing arising two T _gs that correspond to a PVAc-rich phase and to epoxy network phase. Increasing the PVPhBr content the T _gof the PVAc phase move to higher temperatures as a consequence of the PVAc-PVPhBr interactions. Different morphologies are generated as a function of the blend composition.     

Compatibility Study of Blends of Acrylic Rubber (ACM), Poly(ethyleneterephalate) (PET), and Liquid Crystalline Polymer (LCP)

The ternary blends of acrylate rubber (ACM), poly(ethyleneterephalate) (PET), and liquid crystalline polymer (LCP) were prepared by varying the amount of LCP, but fixing the ratio of ACM and PET using melt mixing procedure. The compatibility behavior of these blends was investigated with infrared spectroscopy (IR), differential scanning calorimetry (DSC), and dynamic mechanical analyzer (DMA). The IR results revealed the significant interaction between the blend components. Glass transition temperature (T_g) and melting temperature (T_m) of the blends were affected depending on the LCP weight percent in the ACM/PET, respectively. This further suggests the strong interfacial interactions between the blend components. In the presence of ACM, the nucleating effect of LCP was more pronounced for the PET. The thermogravimetric (TGA) study shows the improved thermal stability of the blends.